THE LIBRARY

OF

THE UNIVERSITY
OF CALIFORNIA

PRESENTED BY

PROF. CHARLES A. KOFOID AND
MRS. PRUDENCE W. KOFOID

ZOONOMIAs

O R,

THE LAWS

OF

ORGANIC LIFE.

VOL. I.
BT ERASMUS DARWIN, M.D.JF.R.S.

AUTHOR OF THE BOTANIC GARDEN.

Principio coelum, ac terras, campofque liquentcs,
.Lucentemque globum lunas, titaniaque ailra,
Spiritus intus alit, totamque infufa per artus
Mens agitat molem, et magno fe corpore mifcet.

ViRG.-ffin.vL

Earth, on whofe lap a thoufand nations tread,

And Ocean, brooding his prolific bed,

Night's changeful orb, blue pole, and filvery zones,

Where other worlds encircle other funs,

One Mind inhabits, one diffufive Soul

Wields the large limbs, and mingles with the whole.

DUBLIN:

PRINTED FOR B. DUGDALE, DAME-STREET.

Cl MB ) X

at 1/1 J- o--i M

,»:^- 1 ! I

DEDICATION.

JL O the candid and ingenious Members of the
College of Phyficians, of the Royal Philofophical
Society, of the Two Univerfities, and to all thofe,
who ftudy the Operations of the Mind as a Science,
or who praftife Medicine as a Profeffion, the fub-
fequent Work is,

With great Refpeft,

N.

Inscribed by

THE AUTHOR.

DERBY, May i, 1794.

.k o 1 1

:

orbos. ;
^ EB M. 9* '!<> tnob«w!'P

CONTENTS.

Preface. i

SECT. I. Of Motion. 5

II. Explanations and Definitions. 7

III. The Motions of the Retina demonftrated

by Experiments J 5

IV. Laws of Animal Caufation. 3 2

V. Of the four Faculties or Motions of the

Senforium. 34

VI. Of the four Cla/es of Fibrous Motions. 36
VII. Of Irritative Motions. 38

VIII. Of Senfttive Motions. 43

IX. Of Voiitntary Motions. 46

X. Of Affbciate Motions. 50

XI. Additional Observations on the Senforlal

Powers. 54

XII. Of Stimulus, Senforial Exert ian, and Fi-

brous Contraction. 62

XIII. Of Vegetable Animation. 106

XIV. Of the Production of Ideas. 1 13
XV. Of the Cla/es of Ideas. 1 3 5

XVI. Of Inftincl. 145

XVII. The Catenation of Animal Motions. 2 2 1

XVIII. Of Sleep. 235

XIX. Of Reverie. 260

SECT.

VI

CONTEMPTS.

SECT. XX.

XXI.

XXII.

XXIII.
XXIV.

XXV.
XXVI.

XXVIL

XXVIII.

XXIX.

XXX.
XXXI.
XXXII.
XXXIII.
XXXIV.
XXXV.
XXXVI.
XXXVIII.
XXXVIII.

XXXIX.
XL*

Of Vertigo. 268

Of Drunkennefs. 283

Of Propenfity to Motion. Repetition.

Imitation. 293

Of the Circulatory Syftem. 304

Of the Secretion of Saliva, and of

Tears. And of the Lacrymal Sack. 3 1 2
Of the Stomach and Intejiines. 320

Of the Capillary Glands, and of the

Membranes. 333

Of Hemorrhages. 338

The Paralyfis of the Lacleals. 346

The Retrograde Motions of the Abforbent

Veffels. 351

The Paralyfis of the Liver. 40 1

Of Temperaments 408

Difeafes of Irritation,
of Senfation.
of Volition.

— tf AJficiation.

The Periods of Difeafes.

Of Digeftion, Secretion, Nutrition.

447
474

502

Of the Oxygenation of the B,

Lungs and Placenta,
Of Generation.
Of Ocular Speclra.

n

525

the

533
542
605

Additional Obfervations on Vertigo, referred to n
Seft. ^X. Page 275, Line 2. 640

TO

TO

ERASMUS DARWIN,

ON HIS WORK INTITLED

Z O O N O M I A.

By DEWHURST BILS BORROW.

HAIL TO THE BARD! who fung, from Chaos hurPd
How funs and planets forra'd the whirling world ;
How fphere onfphere Earth's hidden ftrata bend,
And caves of rock her central fires defend ;
Where gems new-born their twinkling eyes unfold, 5

And young ores (hoot in arborefcent gold.

How the fair Flower, by Zephyr woo'd, unfurls
Its panting leaves, and waves its azure curls ;
Or fpreads in gay undrefs its lucid form

To meet the fun, and (huts it to the ftorm ; 10

While in green veins impaffion'd eddies move,
And Beauty kindles into fire and love.

How the firft embryon-fibre, fphere, or cube,
Lives in new forms — a line — a ring — a Lube ;
Clofed in the womb with limbs unfinim'd laves, I j

Sips with rude mouth the falutary waves ;
Seeks round its cell the fanguine ftreams, that pafs,
And drinks with crimfon gills the vital gas ;
Weaves with foft threads the blue meandering vein,
The heart's red concave, and the filver brain ; 20

Leads the long nerve, expands the impatient fenfe,
And clothes in filken (kin the nafcent Ens.
Erewhile, emerging from its liquid bed,
It lifts in gelid air its nodding head ;

The light's firft dawn with trembling eyelid hails, 25

With lungs untaught arrefts the balmy gales ;
Tries its new tongue in tones unknown, and hears
The ftrange vibrations with unpraclifed ears;

viii TO ERASMUS DARWIN.

Seeks with fpread hands the bofom's velvet orbs,

With clofing lips the milky fount abforbs ; 3©

And, as comprefs'd the dulcet ftreams diftil,

Drinks warmth and fragrance from the living rill ;—

Eyes with mute rapture every waving line,

Prints with adoring kifs the Paphian fhrine,

A nd learns erelong, the perfect form confefs'd, 35

Ideal Beauty from its mother's breaft.

Now in ftrong lines, with bolder tints defign'd,

You fketch ideas, and portray the mind ;

Teach how fine atoms of impinging light

To ceafelefs change the vifual fenfe excite ; 40

While the bright lens collects the rays, that fwerve,

And bends their focus on the moving nerve.

How thoughts to thoughts are link'd with viewlefs chains,

Tribes leading tribes, and trains purfuing trajns ;

With fhadowy trident how Volition .guides, 45

Surge after furge, his intellectual tides ;

Or, Qiieen of Sleep, Imagination roves -^

With frantic Sorrows, or delirious Loves.

Go on, O FRIEND ! explore with eagle-eye ;
Where wrapp'd in night retiring Caufes lie : 50

Trace their flight bands, their fecret haunts betray.
And give new wonders to the beam of day ;
Till, link by link with ftep afpiring trod,
You climb from NATURE to the throne of GOD.

So faw the Patriarch with admiring eyes 55

From earth to heaven a golden ladder rife ;
jnvolv'd in clouds the myfticfcale afcends,
And brutes and angels crowd the diftant ends.

Trtn. Col. Cambridge,
Jan. I, 1794.

REFERENCES TO THE WORK.

Butane Garden, Part I. Line 1 8. Seft. XVI. a. and XXXVIII.

Line i.

" """"" 3»
4-.
— — • 5«

Canto I. 1. joj.
IV 1. 402.
I. 1. 140.

nr. i. 401.

26.

— 36.'
38-

XVI. 4.
XVI. 4.

XVI. 6.
——III. and VII.

8.
— — • Q.

IV. 1. 452.

i. i. 14.

44-

XVJII. 17.

s

45.

XVII. 3. 7.

Zconomia.

47-
50.

XVIII. 8.
Xx XIX. 4 g.

12.

Seft. XIII.

XXXIX. the Motte.

13.

XXXIX. 4. I.

54-

XXXIX. 8.

PREFACE.

JL H E purport of the following pages is an en-
deavour to reduce the fa£b belonging to ANIMAL
LIFE into clafles, orders, genera, and fpecies ; and,
by comparing them with each other, to unravel the
theory of difeafes. It happened, perhaps unfortu-
nately for the inquirers into the knowledge of
difeafes, that other fciences had received improve-
ment previous to their own ; whence, inttead of
comparing the properties belonging to animated na-
ture with each other, they, idly ingenious, bufied
themfelves in attempting to explain the laws of life
by thofe of mechanifm and chemiftry ; they confi-
dered the body as an hydraulic machine, and the
fluids as palling through a feries of chemical changes,
forgetting that animation was its eflential charac-
teriftic.

The great CREATOR of all things has infinitely
diverfified the works of his hands, but has at the
fame time (lamped a certain fimilitude on the fea-
tures of nature, that demonftrates to us, that the
'whole is one family of one parent- On this fimilitude i$
founded ail rational analogy ; which, fo long as it
is concerned in comparing theeffemial properties of
bodies, leads us to many and important difcoveries ;
but when with licentious activity it links together
objects, otherwife difcordant, by fome fanciful fimi-
litude 5 it may indeed colled ornaments for wit

B and

* PREFACE.

and poetry, but philofophy and truth recoil from
its combinations.

The want of a theory, deduced from fuch ftrict
analogy, to' conduct the practice of medicine, is la-
mented by its profeffors ; for, as a great number of
unconnected facts are difficult to be acquired, and
to be reafoned from, the art of medicine is in many
inftances lefs efficacious under the direction of its
wifeft practitioners ; and by that bufy crowd, who
either boldly wade in darknefs, or are led into end-
lefs error by the glare of falfe theory, it is daily
practifed to the deftruction of thousands ; add to
this the unceafing injury which accrues to the pub-
lic by the perpetual advertifements of pretended
noftrums ; the minds of the indolent become fuper-
flitioufly fearful of difeafes, which they do not la-
bour under ; and thus become the daily prey of
fome crafty empiric.

A theory founded upon nature, that mould bind
together the fcattered facts of medical knowledge,
and converge into one point of view the laws of
organic life, would thus on many accounts contri-
bute to the intereil of fociety. It would capacitate
men of moderate abilities to practife the art of
healing with real advantage to the public ; it would
enable every one of literary acquirements to dif-
tinguifh the genuine difciples of medicine from
thofe of boaftful effrontery, or of wily addrefs ;
and would teach mankind in fome important fitua-
tions the knowledge of the?nfelves.

There are fome modern practitioners, who de-
claim againil medical theory in general, not confi-
dering that to think is to theorize ; and that no one
can direct a method of cure to a perfon labouring
under difeafe without thinking, that is, without
theorizing ; and happy therefore is the patient,
whofe phylician poffefles the bed theory.

The

PREFACE. 3

The words idea, perception, fenfation, recollec-
tion, fuggeftion, and aflbciation, are each of them
ufed in this treatife in a more limited fenfe than in
the writers of metaphyfic. The author was in
doubt, whether he mould rather have fubftituted
new words inftead of them ; but was at length of
opinion, that new definitions of words already in
ufe would be lefs burthentbme to the memory of
the reader.

A great part of this work has Iain by the writer
above twenty years, as fome of his friends can tef-
tify : he had hoped by frequent revilion to have
made it worthy the acceptance of the public ; this
however his other perpetual occupations have in
part prevented, and may continue to prevent, as long
as he may be capable of reviling it ; he therefore begs,
of the candid reader to accept of it in its prefent
flate, and to excufe any inaccuracies of expreffion,
or of conclufion, into which the intricacy of his
fubjecl:, the general imperfection of language, or
the frailty he has in common with other men, may
have betrayed him ; -and from which he has not the
vanity to believe this treatife to be exempt.

B 2 ZOONOMIA,

Z O O N O M I A.

SECT. L

OF MOTION.

JL H E WHOLE OF NATURE may be fuppofed to
conlift of two eflences or fubftances ; one of which
may be termed fpirit, and the other matter. The
former of thefe poffeffes the power to commence
or produce motion, and the latter to receive and
communicate it. So that motion, confidered as
a caufe, immediately precedes every effect ; and,
confidered as an effect, it immediately fucceeds
every caufe.

The MOTIONS OF MATTER may be divided into
two kinds, primary and fecondary. The fecondary
motions are thofe which are given to or received
from other matter in motion. Their laws have been
fuccefsfully inveftigated by phiiofophers in their
treatifes on mechanic powers. Thefe motions are
diftinguiftied by this circumftance, that the velocity
multiplied into the quantity of matter of the body
acted upon is equal to the velocity multiplied into
the quantity of matter of the acting body.

The primary motions of matter may be divided
into three claffes, thofe belonging to gravitation,
to chemiftry, and to life ; and each clafs has its
peculiar laws. Though thefe three claffes include
the motions of folid, liquid, and aerial bodies j

there

6 OFMOTION. SECT. I.

there is neverthelefs a fourth divifion of motions ;
I mean thofe of the fuppofed ethereal fluids of mag-
netifm, electricity, heat, and light ; whofe proper-
ties are not fo well inveiligated as to be claffed with
fufficient accuracy.

ift. The gravitating motions include the annual
and diurnal rotation of the earth and planets, the
flux and reflux of the ocean, the defcent of heavy-
bodies, and other phenomena of gravitation. The
unparalleled fagacity of the great NEWTON has de-
duced the laws of this clafs of motions from the
iimple principle of the general attraction of matter.
Thefe motions are diftinguiftied by their tendency
to or from the centers of the fun or planets.

id. The chemical clafs of motions includes all
the various appearances of chemiftry. Many of the
fads, which belong to thefe branches of fcience, are
nicely alcertained, and elegantly clafled ; but their
laws have not yet been developed from fuch fimple
principles as thofe above-mentioned ; though it is
probable, that they depend on the fpecific attracti-
ons belonging to the particles of bodies, or to the
difference of the quantity of attraction belonging
to the fides and angles of thofe particles. The che-
mical notions are diftinguifhed by their being gene-
rally attended with an evident decompolition or
new combination of the active materials.

3^/. The third clafs includes all the motions of the
animal and vegetable world ; as well thofe of the
veffels, which circulate their juices, and of the
rnufcles, which perform their locomotion, as thofe
of the organs of fenfe, which conftitute their ideas.

Thib laft clafs of motion is the fubject of the fol-
lowing pages ; which, though confcious of their
many imperfections, 1 hope may give fome pleafure
to the patient reader, and contribute fomething to
the knowledge and to the cure of difeafes.

SECT.

SE«T. II. DEFINITIONS* 7

SECT. II. i.

EXPLANATIONS AND DEFINITIONS.

I. Outline of the animal economy . — II. i. Ofthejerifo-

rium. 2. Of the brain and nervous medulla. 3.

A nerve. 4. A mufcular fibre. 5. The immediate

organs of fenfe. 6. "The external organs of ' fenfe. 7.

An idea or fenfual motion. 8. Perception. 9. Sen-

fation. 10 Re collection and fuggeft ion. n. Habit,

caufation> affbciation, catenation. 12. Reflex ideas.

13. Stimulus defined.

As fome explanations and definitions will be neceffary in the profecu-
tion of the work, the reader is troubled with them in this place,
and is intreated to keep them in his mind as he proceeds, and to
take them for granted, till an apt opportunity occurs to evince their
truth ; to which I /hall premife a very fhort outline of the animal
economy.

I. — i. THE nervous fyftem has its origin from
the brain, and is diflributed to every part of the
body. Thofe nerves, which ferve the fenfes, prin-
cipally arife from that part of the brain, which is
lodged in the head ; and thofe, which ferve the
purpofes of mufcular motion, principally arife from
that part of the brain, which is lodged in the neck
and back, and which is erroneoufly called the fpi-
nal marrow. The ultimate fibrils of thefe nerves
terminate in the immediate organs of fenfe and
mufcular fibres, and if a ligature be put on any part
of their paflage from the head or fpine, all motion
and perception ceafe in the parts beneath the liga-
ture.

a. The

* DEFINITIONS. SECT. II. i.

2. The longitudinal mufcular fibres compofe the
locomotive mufcles, whofe contractions move the
bones of the limbs and trunk, to which their extre-
mities are attached. The annular or fpiral mufcular
fibres compofe the vafcular mufcles, which confti-
tute the inteflinal canal, the arteries, veins, glands,
and abforbent veffels.

3. The immediate organs of fenfe, as the retina
of the eye, probably con fifl of moving fibrils, with
a power of contraction lirnilar to that of the larger
mufcles above defcribed.

4. Tiie cellular membrane confifts of cells, which
refemble thofe of a fponge, communicating with
each other, and connecting together all the other
parts of the body.

5. The arterial fyfte'tn confifts of the aortal and
the pulmonary artery, which are attended through
their whole courfe with their correfpondent veins.
The pulmonary artery receives the blood from the
right chamber of the heart, and carries it to the mi-
nute extenfive ramifications of the lungs, where it
is expofed to the action of the air on a furface equal
to that of the whole external fkin, through the thin
itioift coats of thofe veffels, which are fpread on the
air-cells, which conftitute the minute terminal ra-
mificatitihs of the wind pipe. Here the blood
changes its colour from a dark red to a bright fear-
let. 'It is then collected by the branches of the pul-
monary vein, and conveyed to the left chamber of
the heart.

6. The aorta is another large artery, which re-
ceives the'blood from the left chamber of the heart,
after it has been thus aerated in the lungs, and con-
veys it by afcending and defcending branches to
every other part of the fyftem ; the extremities of
this artery terminate either in glands, as the falivary
glands, lacrymal glands, &c. or in capillary veflels,
which are probably lefs involuted glands \ in thefe

fome

SECT. II. i. DEFINITIONS. 9

foii.-e fluid, as faliva, tears, perfpiratlon, are fepa-
rated from the blood ; and the remainder of the
blood is abfoibed or drank up by branches of veins
CTrefpondent to the branches of the artery ; which
are fu mimed with valves to prevent its return ; and
is thus carried back, after having again changed its
colour to a dark red, to the right chamber of the
heart, The circulation of the blood in the liver
differs from this general fyftem ; for the veins which
drink up the refluent blood from thole arteries,
which are fpread on the bowels and mefentery, unite
into a trunk in the liver, and form a kind of artery,
which is branched into the whole fuhltance of the
liver, and is cahed the vena portarum ; and from
which the bile is feparated by the numerous hepatic
glands, which constitute that vifcus.

7. The glands may be divided into three fyftems,
the convoluted glands, fuch as thofe above defcribed,
which feparate bile, tears, faliva, &c. Secondly,
the glands without convolution, as the capillary vef-
fels, which unite the terminations of the arteries and
veins ; and feparate. both the mucus, which lubri-
cates the cellular membrane, and the perfpirable
matter, which preferves the Ikin moift and flexible.
And thirdly, the whole abforbent fyftem, confining
of the lacleals, which open their mouths into the
ftomach and inteflines, and of the lymphatics, which
open their mouths on the external furface of the
body> and on the internal linings of all the ceils of the
cellular membrane, and other cavities of the body.

Thefe lacteal and lymphatic veflels are furnifhf d
with numerous valves to prevent the return of the
fluids, which they abforb, and terminate in glands,
called lymphatic glands, and may hence be confi-
dered as long necks or mouths belonging to thefe
glands. To thefe they convey the chyle and mucus,
with a part of the perfpirable matter, and atmof-
pherk moifture ; all which, after having pafled

through

io DEFINITIONS. SECT. II. 2,

through thefe glands, and having fuffered feme
change in them, are carried forward into the blood,
and lupply perpetual nourifhment to the fyftem, or
replace its hourly wafte.

8. The ftomach and inteftinal canal have a con-
flant vermicular motion, which carries forwards
their contents, after the la&eals have drank up the
chyle from them -, and which is excited into aclion
by the ftimulus of the aliment we fwallow, but
which becomes occafionally inverted or retrograde,
as in vomiting, and in the iliac paffion.

II. i. The wordfen/brium in the following pages is
deligned to exprefs not only the medullary part of
the brain, fpinal marrow, nerves, organs of fenfe,
and of the mufcles ; but alfo at the fame time that
living principle, or fpirit of animation, which re-
iides throughout the body, without being cogniza-
ble to our fenfes, except by its effects. The changes
which occafionally take place in the fenforium, as
during the exertions of volition, or the fenfations
of pleafure or pain, are termed fen/or ial motions.

2» The fimilarity of the texture of the brain to
that of the pancreas, and fome other glands of the
body, has induced the inquirers into this fubject to
believe, that a fluid, perhaps much more fubtile
than the eleclric aura, is feparated from the blood
by that organ for the purpofes of motion and fenfa-
tion. When we recollect, that the eleclric fluid it-
ielf is actually accumulated and given out volunta-
rily by the torpedo and the gymnotus ele&ricus,
that an electric (hock will frequently ftimulate into
motion a paralytic limb, and laftly that it needs no
perceptible tubes to convey it, this opinion feems
not without probability ; and the fingular figure of
the brain and nervous fyftem feems well adapted to
dHiribute it over every part of the body.

For the medullary fubftanceof the brain not only
occupies the cavities of the head and fpine, but pat

ics

SECT. II. 2. DEFINITIONS. n

fes along the innumerable ramifications of the
nerves to the various mufcles and organs of fenfe.
In thefe it lays afide its coverings, and is intermixed
with the flender fibres, which conftitute thofe muf-
cles and organs of fenfe. Thus all r(iefe diftant ra-
mifications of the fenforium are united at one of
their extremities, that is, in the head and fpine ;
and thus theie central parts of the fenforium con-
ftitute a communication between all the organs of
fenfe and mufcles.

3. A nerve is a continuation of the medullary fub-
ftance of the brain from the head or fpine towards
the other parts of the body, wrapped in its proper
membrane.

4. The mufculdr fibres are moving organs inter-
mixed with that medullary fubftance which is con-
tinued along the nerves, as mentioned above. They
are indued with the power of contraction, and are
again elongated either by antagonift mufcles, by
circulating fluids, or by elaftic ligaments. So the
mufcles on one fide of the fore-arm bend the fingers
by means of their tendons, and thofe on the other
fide of the fore-arm extend them again. The arte-
ries are diftended by the circulating blood ; and in
the necks of quadrupeds there is a ftrong elaftic li-,
gament, which aflifts the mufcles, which elevate the
head, to keep it in its horizontal pofition, and to
raife it after it has been depreffed.

5. The immediate organs of fenfe confift in like
manner of moving fibres enveloped in the medul-
lary fubftance above mentioned ; and are erroneouf-
ly fuppofed to be fimply an expanfion of the ner-
vous medulla, as the retina of the eye, and the
rete mucofum of thefkin, which are the immediate
organs of viiion, and of touch. Hence when \ve
fpeak of the contractions of the fibrous parts of the
body, we fhall mean both the contractions of the

mufcles.

12 DEFINITION S, SECT. II. i.

mufcles, and thofe of the immediate organs of fcnfe.
Thefejibrous motions are thus dittinguifhed from the
fenforial motions above mentioned.

6. The external organs of fenfe are the coverings
of the immediate organs of fenfe, and are mecha-
nically adapted for the reception or tranfmiffion of
peculiar bodies, or of their qualities, as the cornea
and humours of the eye, the tympanum of the ear,
the cuticle of the fingers and tongue.

7. The word idea has various meanings in the
writers of metaphyfic : it is here ufed limply for
thofe notions of external things, which our organs
of fenfe bring us acquainted with originally ; and is
defined a contraction, or motion, or configuration,
of the fibres, which conftitute the immediate organ
of fenfe ; which will be explained at large in an-
other part of the work. Synonymous with the word
idea, we mall fometimes ufe the words fenfual mo-
tion in contradiftinction to mufcular motion.

8. The word perception includes both the action
of the organ of fenfe in confequence of the impact
of external objects, and our attention to that ac-
tion ; that is, it expreffes both the motion of the
organ of fenfe, or idea, and the pain or pleafure
that fucceeds or accompanies it.

9. 1 he pleafure or pain which neceffarily accom-
panies all thofe perceptions or ideas which we at-
tend to, either gradually fubfides, or is fucceeded
by other fibrous motions. In the latter cafe it is
termedy^vT/tf//^, as explained in Sect. V. 2, and VI.
2. — The reader is intreated to keep this in his mind,
that through all this treatife the word fenfation is
ufed to exprefs pleafure or pain only in its active
Hate, by whatever means it is introduced into the
fyftem, without any reference to the ftimulation of
external objects.

10. The vulgar ufe of the word memory is too
unlimited for our purpofe : thofe ideas which we

voluntarily

SECT. II. 2. , DEFINITIONS. 13

voluntarily recall are here termed ideas of recollefti-
cn, a?, when we will to repeat the alphabet back-
wards. And thofe ideas which are fuggefted to us
by preceding ideas are here termed ideas of Juggejl-
ion, as whilft we repeat the alphabet in the ufual or-
der ; when by habits previoufly acquired B is fug-
gefted by A, and C by B, without any effort of
deliberation.

1 1. The word affectation properly fignifies a fociw-
ety or convention of things in fome refpects iirnilar
to each other. We never fay in common language,
that the effect is affociated with the caufe, though
they neceffarily accompany or fucceed each other.
Thus the contractions of our mufcles and organs of
fenie may be faid to be affociated together, but can-
not with propriety be faid to be affociated with irri-
tations, or with volition, or with fenfation ; becaufe
they are caufed by them, as mentioned in Sect. IV.
When fibrous contractions fucceed other fibrous con-
tractions, the connection is termed aff&ciation ; when
fibrous contractions fucceed fenforlal motions, the
connection is termed caufation ; when fibrous and
fenforial motions reciprocally introduce each other
in progrefiive trains or tribes, it is termed catenation
of animal motions. All thefe connections are faid
to be produced by habit \ that is, by frequent repe-
tition.

1 2. It may be proper to obferve, that by the un*
avoidable idiom of our language the ideas of per-
ception, of recollection, or of imagination, in the
plural number fignify the ideas belonging to percep-
tion, to recollection, or to imagination ; whilft the
idea of perception, of recollection, or of imagina-
tion, in the fingular number is ufed for what is
termed " a reflex idea of any of thofe operations
of the fenforium."

13. By the wordflimulus is not only meant the
application of external bodies to our organs of fenfe

and

14 DEFINITIONS. SECT. II.*.

and jnufcular fibres, which excites into action the
fenforial power termed irritation ; but alfo pleafurc
or pain, when they excite into action the fenforial
power termed fenfation ; and defire or averfion,
when they excite into action the power of volition ;
and laftly, the fibrous contractions which precede
affectation ; as is further explained in Sect, XII. 2.
i.

SECT.

SECT. III. i. MOTIONS OF THE RETINA.

SECT. III.

THE MOTIONS OF THE RETINA DEMONSTRATED BY
EXPERIMENTS.

I. Of animal motions and of ideas. II. The fibrous
ftruclure of the retina. III. The aftivity of the re-
tina in vifion. i . Rays of light have no momentum.
2. Objects long viewed become fainter. 3* Spectra of
black objecls become luminous. 4. Varying fpeclra
from gyration. 5. From long injpedion of various
colours. IV. Motions of the organs of fenfe conftitute
ideas, i. Light from prejjing the eye-ball, and found
from the pulfation of the carotid artery. 2. Ideas in
Jleep mif taken for perceptions. 3. Ideas of imaginati-
on produce pain andjicknefs like fenfations. 4. When
the organ of fenfe is deftroyed, the ideas belonging to
that fenfe per ifh. V. Analogy between mufcular mo-
tions and Jenfual motions, or ideas, i. cfihey are both
originally excited by irritations. 2. And ajjociated to-
gether in the fame manner. 3. Both aft in nearly the
fame times. 4. Are alike ftrengthened or fatigued by
exercife. 5. Are alike painful from inflammation. 6.
Are alike benumbed by comprejjion. 7. Are alike liable
to paralyfis. 8. To convulfion. 9. To the influence
of old age. VI. Objections anfwered. i . Why we
cannot invent new ideas, i. If ideas refemble exter-
nal objefls. 3. Of the imagined fenfation in an ampu-
tated limb. 4. /ibftratl ideas. VII. What are ideas,
if they are not animal motions ?

BEFORE the great variety of animal motions
can be duly arranged into natural clafles and orders,
it is neceflary to fmooth the way to this yet uncon-
quered field of fcience, by removing fome obftacles

C which

*6 MOTIONS OF THE RETINA. SECT. III. i.

which thwart our paffage. I. To demonftrate that
the retina and other immediate organs of fenfe pof-
fefs a power of motion, and that thefe motions con-
flitute our ideas, according to the fifth and feventh
of the preceding affertions, claims our firft attenti-
on.

Animal motions are diftinguiflied from the com-
ttiunicated motions, mentioned in the firft feclion,
as they have no mechanical proportion to their caufe;
for the goad of a fpur on the Ikin of a horfe fhall
induce him to move a load of ha^. They differ
from the gravitating motions there mentioned, as
they aj*e exerted with equal facility in all directions,
and they differ from the chemical clafs of motions,
becaufe no apparent decompofitions or new combi-
nations are produced in the moving materials.

Hence, when we fay, animal motion is excited
by irritation, we do not mean that the motion bears
any proportion to the mechanical impulfe of the
ilimulus ; nor that it is affected by the general gra-
vitation of the two bodies ; nor by their chemical
properties, but folely that certain animal fibres are
excited into action by fomething external to the *
moving organ.

In this fenfe the ftimulus of the blood produces
the contractions of the heart ; and the fubftances
we take into our ftomach and bowels irritate them
to perform their neceffary functions. The rays of
light excite the retina into animal motion by their
ftimuius ; at the lame time that thofc rays of light
themfeives are phyfically converged to a focus by
the inactive humours of the eye. The vibrations of
the air ftirnulate the auditory nerve into animal ac-
tion ; while it is probable that the tympanum of
the ear at the fame time undergoes a mechanical vi-
bration.

To

Seer. III. i. MOTIONS OF THE RETINA. 17

To render this circumftance more eafy to be com-
prehend e 1 motion may be defined to be a variation of
fgure ; for the whole univerfe may be confidered ag
one rhino; pofTeffmg a certain figure ; the motions of
any of its parts are a variation of this figure of the
whole : this definition of motion will be further ex-
plained in Section XIV. 2. 2. on the production of
ideas.

Now the motions of an"organ of fenfe are a fuc-
cefllon of configurations of that organ ; thefe con-
figurations fucceed each other quicker or flower ;
and whatever configuration of this organ of fenfe,
that is, whatever portion of the motion of it is, or
has ufually been, attended to, conftitutes an idea*
Hence the configuration is not to be confidered as
an effect of the motion of the organ, but rather as
apart or temporary termination of it; and that,
whether a paufe fucceeds it, or a configuration im-
mediately takes place. Thus when a fucceffion of
moving objects are prefented to our view, the ideas
of trumpets, horns, lords and ladies, trains and
canopies, are configurations, that is, parts or links
of the fuccellive motions of the organ of vifion.

Thefe motions or configurations of the organs of
fenfe differ from the fenforial motions to be defcrib-
ed hereafter, as they appear to be (imply contrac-
tions of the fibrous extremities of thofe organs, and
in that refpect exactly referable the motions or con*
tractions of the larger mufcles, as appears from the
following experiment. Place a circular piece of red
filk about an inch in diameter on a (heet of white
paper in a ftrong light, as in Plate I. — look for a
minute on this area, or till the eye becomes fome-
what fatigued, and then, gently clofing your eyes,
and (hading them with your hand, a circular green
area of the fame apparent diameter becomes vifible
in the clofed eye. This green area is the colour
reverfe to the red area, which had been previoufly
C 2 infpected,

J8 MOTIONS OF THE RETINA. SECT. III. j.

infpefted, as explained in the experiments on ocular
fpeftra at the end of the work, and in Botanical
Garden, P. I. additional nore, No. I. Hence it ap-
pears, that a part of the retina, which had been fa-
tigued by contraction in one direction, relieves it-
ielf by exerting the antagonift fibres, and producing
a contraction in an oppofite direction, as is common
in the exertions of our mufcles. Thus when we are
tired with long action of our arms in one direction,
as in holding a bridle on a journey, we occafion-
ally throw them into an oppofite pofition to relieve
the fatigued mufcles.

Mr. Locke has defined an idea to be " whatever
is prefent to the mind ;" but this would include the
exertions of volition, and the fenfations of pleafure
and pain, as well as thofe operations of our fyftem,
which acquaint us with external objects ; and is
therefore too unlimited for our purpofe. Mr. Locke
feems to have fallen into a further error, by con-
ceiving, that the mind could form a general or ab-
ftract idea by its own operation, which was the
copy of no particular perception ; as of a triangle
in general, that was neither acute, obtufe, nor
right angled. The ingenious Dr. Berkley and Mr.
Hume have demonftrated, that fuch general ideas
have no exigence in nature, not even in the mind
of their celebrated inventor. We ihall therefore
take for granted at prefent, that our recollection or
imagination of external objects confifts of a partial
repetition of the perceptions, which were excited
by thofe external objects, at the time we became ac-
quainted with them ; and that our reflex ideas of
the operations of our minds are partial repetitions
of thofe operations.

II, The following article evinces that the organ
of vifion confifts of a fibrous part as well as of the
nervous medulla, like other white mufcles ; and
hence, as it refembles the mufcular parts of the

body

SECT. III. 3. MOTIONS OF THE RETINA. 19

body in its ftruclure, we may conclude, that it muft
refemble them in poflefling a power of being excit-
ed into animal motion. — -The fubfequt-nt experi-
ments on the optic nerve, and on the colours re-
maining in the eye, are copied from a paper on ocu-
lar fpecira publifhed in the feventy-fixth volume of
the Philof. Tranf. by Dr. R. Darwin of Shrewf-
bury ; which, as I mail have frequent occafion to
refer to, is reprinted in this work, Seel:. XL. The
retina of an ox's eye was fufpended in a glafs of
warm water, and forcibly torn in a few places ; the
edges of thefe parts appeared jagged and hairy, and
did not contract and become fmooth like (imple
mucus, when it is diftended till it breaks ; which
evinced that it confifled of fibres. This fibrous
conftruction became ftill more diftincl to the fight
by adding fome cauftic alcali to the water ; as the
adhering mucus was firft eroded, and the hair-like
fibres remained floating in the veffeL Nor does the
degree of tranfparency of the retina invalidate this
evidence of its fibrous ftrudure, fince Leeuwenhoek
has fliewn, that the cryftaJline humour itfelf confilb
of fibres. Arc. Nat. V. I. 70.

Hence it appears, that as the mufcles confift of
larger fibres intermixed with a fmaller quantity of
nervous medulla, the organ, of vifion confift-s of a
greater quantity of nervous medulla intermixed
with fmaller fibres. It is probable that the locomo-
tive mufcles c/f microfcopic animals may have
greater tenuity than thofe of the retina ; and there
is reafon to conclude from analogy, that the other
immediate organs of fenfe, as the portio molHs of
the-auditory nerve, and. the rete mucofum of the
ikin, poffefs a fimilarity of ftruclure with the reti-
na, and a fimilar power of being excited into anU
mal motion.

III. The fubfequent articles {hew, that neither
mechanical impreffions, nor chemical combinations.

of

?o MOTIONS OF THE RETINA. SECT. HI, 5.

of light, but that the animal adivity of the retina
conftitutes vifion.

i. Much has been conjectured by philosophers
about the momentum of the rays of light ; to fubjecl:
this to experiment a very light horizontal balance
was conftrucled by Mr. Michel, with about an inch
fquare of thin leaf-copper fufpended at each end of
it, as defcribed in Dr. Prieftley's Hiftory of Light
and Colours. The focus of a very large convex
mirror was thrown by Dr. Powel, in his lectures on
experimental phiiofophy, in my prefence, on one
wing of this delicate balance, and it receded from
the light ; thrown on the other wing, it approached
towards the light, and this repeatedly ; fo that no
fenlible impulie could be obferved, but what might
well be afcribed to the afcent of heated air.

Whence it is reafonable to conclude, that the
light of the day muft be much too weak in its dilute
ftate to make any mechanical impreflion on fo tena-
cious a fubftance as the retina of the eye. — -Add to
this, that as the retina is nearly tranfparent, it could
therefore make lefs refinance to the mechanical im-
pulfe of light;- which, according to the obfervati-
ons related by Mr. Melvil in the Edinburgh Literar
ry Effays, only communicates heat, and fhould there-
fore only communicate momentum, where it is ob-
ftrucled, reflected, or refracted. — -From whence alfo
niay be collected the final caufe of this degree of
tranfparency of the retina, viz. left by the focus of
flronger lights, heat and pain mould have been pro-
duced in the retina, inftead of that ftimulus which
excites it into animal motion.

2. On looking long on an area of fcarlet filk of
about an inch in diameter laid on white paper, as
in Plate I. the fcarlet colour becomes fainter, till at
length it entirely vanifhes, though the eye is kept
uniformly and tieadily upon it. Now if the change
$f motipn of the retina was a mechanical imprcffi.

SECT. III. 3. MOTIONS OF THE RETINA. , 21

on, or a chemical tinge of coloured light, the per-
ception would every minute become ftronger and
ftronger — whereas in this experiment it becomes
every inftant weaker and weaker. The fame cir-
cumflance obtains in the continued application of
found, or of fapid bodies, or of odorous ones, or
of tangible oness to their adapted organs of icnfe.

Thus when a circular coin, as a {hilling, is preffed
on the palm of the hand, the fenfe of touch is me-
chanically compreffed ; but it is the flimulus of this
preflure that excites the organ of touch into ani-
mal action, which conftitutes the perception of
hardnefs and of figure : for in feme minutes the
perception ceafes, though the mechanical prefTure of
the object remains.

3. Make with ink on white paper a very black fpot
about half an inch in diameter, with a tail about an
inch in length, fo as to refemble a tadpole, as in
Plate II. ; look ftedfaftly for a minute on the center
of this fpot, and on moving the eye a little, the
figure of the tadpole \vill be feen on the white part
of the paper j which figure of the tadpole will ap-
pear more luminous than the other part of the white
paper ; which can only be explained by fuppofing
a part of the retina, on which the tadpole was
delineated, to have become more fenfible to light
than the other parts of it, which were expofed to
the white paper ; and not from any idea of mecha-
nical impreffion or chemical combination of light
with the retina.

4. When any one turns round rapidly, till he be-
comes dizzy, and falls upon the ground, the fpec-
tra of the ambient objects continue to prefent them-
felves in rotation, and he feems to behold the ob-
jects ftillin motion. Now if thefe fpectra were im-
preflions on a paffive organ, they either muft conti-
nue as they were received laft, or not continue at
ill,

5- Placq

22 MOTIONS OF THE RETINA. SECT. III. 3.

5. Place a piece of red filk about an inch in dia-
meter on a fheet of white paper in a ftrong light, as
in Plate I. ; look fteadily upon it from the diftance
of about half a yard for a minute ; then doling
your eye-lids, cover them with your hands and hand-
kerchief, and a green fpeclrum will be feen in your
eyes refembling in form the piece of red filk. After
fome feconds of time the fpeftrum will difappear,
and in a few more feconds will reappear ; and thus
alternately three or four times, if the experiment
be well made, till at length it vanifhes entirely.

6. Place a circular piece of white paper, about
four inches in diameter, in the funfhine, cover the
center of this with a circular piece of black filk,
about three inches in diameter ; and the center of
the black filk with a circle of pink filk, about two
inches in diameter ; and the center of the pink filk
with a circle of yellow filk, about one inch in dia-
meter ; and the center of this with a circle of blue
fiik, about half an inch in diameter ; make a fmall
fpot with ink in the center of the blue filk, as in
Piate 111. look fteadily for a minute on this central
fpot, and then clofing your eyes, and applying your
hand at about an inch diftance before them, fo as to
prevent too much or too little light from paffing
through the eye-lids, and you will fee the moft beau-
tiful circles of colours that imagination can con*
ceive ; which are moft refembled by the colours oc-
cafioned by pouring a drop or two of oil on a ftili
lake in a bright day. But thefe circular irifes of co-
lours are not only different from the colours of the
filks above mentioned, but are at the fame time per*
petually changing as long as they exift*

From all thefe experiments it appears, that thefe
fpectra in the eye are not owing to the mechanical
impulfe of light impreffed on the retina ; nor to its
chemical combination with that organ ; nor to the
abforption and emiffion of light j as is fuppofed

perhaps

SECT. 111.4. MOTIONS OF THE RETINA. 2*

perhaps crroncoufly, to take place in calcined fhells
and other phofphorefcent bodies, after having been
expofed to the light : for in all thefe cafes the fpec-
tra in the eye ftiould either remain of the fame co-
lour, or gradually decay, when the object is with-
drawn ; and neither their evanefcence during the
prefence of their object, as in the fecond experi-
ment, nor their change from dark to luminous, as
in the third experiment, nor their rotation, as in
the fourth experiment, nor the alternate prefence
and evanefcence of them, as in the fifth experiment,
nor the perpetual change of colours of them, as in
the laft experiment, could exift.

IV. The fubfequent articles ihew, that thefe ani-
mal motions or configurations of our organs of
fenfe conftitute our ideas.

1. If any one in the dark prefles the ball of his
eye, by applying his finger to the external corner
of it, a luminous appearance is obferved ; and by
a fmart ftroke on the eye great flafhes of fire are
perceived. (Newton's Optics.) So that when the
arteries, that are near the auditory nerve, make
flronger pulfations than ufual, as in fome fevers,
an undulating found is excited in the ears Hence
it is not the prefence of the light and found, but
the motions of the organ, that are immediately ne-
ceflary to conftitute the perception or idea of light
and found.

2. During the time of fleep, or in delirium, the
ideas of imagination are midaken for the percepti-
ons of external objects ; whence it appears, that
thefe ideas of imagination are no other than a rei-
teration of thofe motions of the organs of fenfe,
which were originally excited by the ftimulus of
external objects : and in our waking hours the fim-
ple ideas, that we call up by recollection or by
imagination, as the colour of red, or the fmell of

a rofe,

24 MOTH3NS OF THE RETINA. S*CT. III. 4.

a rofe, are exact refemblanccs of the fame fimplc
ideas from perception ; and in confequence muft be
a repetition of thofe very motions.

3. The difagreeable fenfation called the tooth-
edge is originally excited by the painful jarring of
the teeth in biting the edge of the glafs, or porce-
lain cup, in which our food was given us in our in-
fancy, as is further explained in the Section XVI.
10, on Inftinft. — This di {agreeable fenfation is after-
wards excitable not only by a repetition of the
found, that was then produced, but by imaginati-
on alone, as I have myfelf frequently experienced ;
in this cafe the idea of biting a china cup, when I
imagine it very diftinclly, or when I fee another
perfon bite a cup or glafs, excites an actual pain in
the nerves of my teeth. So that this idea and pain
ieem to be nothing more than the reiterated motions
of thofe nerves, that were formerly fo difagreeably
affected.

Other ideas that are excited by imagination or '
recollection in many inftances produce flmilar ef-
fects on the conftitution, as our perceptions had
formerly produced, and are therefore undoubtedly
a repetition of the fame motions. A ftory which
the celebrated Baron Van Swieten relates of him-
felf is to this purpose. He was prefent when the
putrid carcafe of a dead dog exploded with prodi-
gious ftench ; and fome years afterwards, acciden-
tally riding along the fame road, he was thrown
into the fame ficknefs and vomiting by the idea of
the ftench, as he had before experienced from the
perception of it.

4. Where the organ of fenfeis totally deftroyed,
the ideas which were received by that organ feem
to peri Hi along with it, as well as the power of per-
ception. Of this a fatisfactory inftance has fallen
under my obfervation. A gentleman about fixty
years of age had been totally deaf for near thirty

years :

SECT. III. 5. MOTIONS OF THE RETINA, 25

years : he appeared to be a man of good under-
ftanding, and amufed himfelf with reading, and by
converfine: either by the ufe of the pen, or by figns
made with his fingers, to reprefent letters. I ob-
ferved that he had' ib far forgot the pronunciation
of the language, that when he attempted to fpeak,
none of his words had diftinct articulation, though
his relations could fometimes underftand his mean-
ing. But, which is much to the point, he allured
me, that in his dreams he always imagined that
people converfed with him by figns or writing, and
never that he heard any one fpeak to him. From
hence it appears, that with the perceptions of founds
he has alfo loft the idea of them ; though the or-
gans of fpeech dill retain fomewhat of their ufual
habits of articulation.

This obfervation may throw fome light on the
medical treatment of deaf people ; as it may be
learnt from their dreams, whether the auditory
nerve be paralytic, or their deafnefs be owing to
fome defect of the external organ.

It. rarely happens that the immediate organ of
vifion is perfectly deftroyed. The moft frequent
caufes of blindnefs are occaiioned by defects of the
external organ, as in cataracts and obfufcations of
the cornea. But 1 have had the opportunity of
converfing with two men, who had been fome years
blind; one of them had a complete gutta ferena,
and the other had loft the whole fubftance of his
eyes. They both told me that they did not re-
member to have ever dreamt of vifible objects, fmce
the total lofs of their fight.

V. Another method of difcovering that our ideas
are animal motions of the organs of fenfe, is from
confidering the great analogy they bear to the mo-
tions of the larger mufcles of the body. In the
following articles it will appear that they are ori-
ginally excited into action by the irritation of ex-
ternal

26 MOTIONS OF THE RETINA. SECT, III. j.

ternal objects like our mufcles ; are affociated toge-
ther like our mufcular motions ; act in limilar time
with them ; are fatigued by continual exertion like
them; and that the organs of fenfe are fubject to
inflammation, numbnefs, palfy, convulfion, and
the defects of old age, in the fame manner as the
mufcular fibres.

1. All our perceptions or ideas of external ob-
jects are univerfally allowed to have been originally
excited by the ftimulus of thofe external objects ;
and it will be (hewn in a fucceeding fectlon, that it
is probable that all our mufcular motions, as well
thofe that are ^become voluntary as thofe of the
heart and glandular fyftem, were originally in like
manner excited by the ftimulus of fomething exter-
nal to the organ of motion.

2. Our ideas are alfo affociated together after
their production precifely in the fame manner as our
mufcular motions ; which will likewifebe fully ex-
plained in the fucceeding fection.

3. The time taken up in performing an idea is
like wife much the fame as that taken up in perform-
ing a mufcular motion. A mufician can prefs the

- keys of an harpfichord with his fingers in the or-
der of a tune he has been accuftomed to play, in as
little time as he can run over thofe notes in his
mind. So we many times in an hour cover our eye-
balls with our eye- lids without perceiving that we
are in the dark ; hence the perception or idea of
light is not changed for that of darknefs in fo fmali
a time as the twinkling of an eye; fo that in this
cafe the mufcular motion of the eye-lid is perform-
ed quicker' than the perception of light can be
changed for that of darknefs. — So if a fire-ftick be
\vlnrfed round. in the dark, a luminous circle ap-
pears to the obferver ; if it be whirled fomewhaC
flower, this circle becomes interrupted in one part ;
and then the time taken up in fuch a revolution of

the

ICT. III. 5. MOTIONS OF THE RETINA. 27

the flick is the fame that the obferver ufes in chang-
ing his ideas : thus the ^x,ootMW aw of Homer, the
long (hadow of the flying javelin, is elegantly de-
figned to give us an idea of its velocity, and not of
its length.

4. The fatigue that follows a continued attention
of the mind to one object is relieved by changing
the fubjeft of our thoughts ; as the continued
movement of one limb is relieved by moving an-
other in its (lead. Whereas a due exercife of the fa-
culties of the mind ftrengthens and improves thofe
faculties, whether of imagination or recolle&ion ;
as the exercife of our limbs in dancing or fencing
increafes the ftrength and agility of the mufcles thus
employed.

5. If the mufcles of any limb are inflamed, they
do not move without pain ; fo when the retina is
inflamed, its motions alfo are painful. Hence light
is as intolerable in this kind of ophthalmia, as pref-
fure is to the finger in the paronychia. In this dif-
eafe the patients frequently dream of having their
eyes painfully dazzled; hence the idea of ftrong
light is painful as well as the reality, The firft of
thefe facts evinces that our perceptions are motions
of the organs of fenfe; and the latter, that our
imaginations are alfo motions of the fame organs.

6. The organs of fenfe, like the moving mufcles,
are liable to become benumbed, or lei's fenfible,
from comprefllon. Thus, if any perfon on a light
day looks on a white wall, he may perceive the ra-
mifications of the optic artery, at every pulfation
of it, reprefented by darker branches on the white
wall ; which is evidently owing to its comprefling
the retinue during the diaftole of the artery. Sa-
vage Noiblog.

7. The organs of fenfe and the moving mufcles
are alike liable to be affe&ed with palfy, as in the

D gutta

2S MOTIONS OF THE RETINA. SECT. III. 5.

gutta ferena, and in fome cafes of deafnefs ; and
one fide of the face has fometimes loft its power of
fenfation, but retained its power of motion ; other
parts of the body have loft their motions but re-
tained their fenfation, as in the common hemipla-
gia ; and in other inftances both thefe powers have
perifhed together.

8. In fome convulfive difeafes a delirium or infa-
nity fupervenes, and the convulfions ceafe ; and
converfely the convulfions fhall fupervene, and the
delirium ceafe. Of this I have been a witnefs ma-
ny times in a day in the paroxyfms of violent epi-
lepfies ; which evinces that one kind of delirium is
a convulfion of the organs of fenfe, and that our
ideas are the motions of thefe organs : the fubfe-
quent cafes will illuftrate this obfervation.

Mifs G , a fair young lady, with light

eyes and hair, was feized with moft violent convul-
fions of her limbs, with outrageous hiccough, and
moft vehement efforts to vomit : after near an hour
xvas elapfed this tragedy ceafed, and a calm talkative
delirium fupervened for about another hour ; and
thefe relieved each other at intervals during the
greateft part of three or four days. After having
carefully confidered this difeafe, I thought the con-
vulfions of her ideas lefs dangerous than thofe of
her mufcles ; and having in vain attempted to make
any opiate continue in her ftomach, an ounce of
laudanum was rubbed along the fpine of her back,
and a dram of it was uled as an enema ; by this me-
dicine a kind of drunken delirium was continued
rnany hours ; and when it ceafed the convulfions
did not return ; and the lady continued well many
years, except fome {lighter relapfes, which were re-
lieved in the fame manner.

Mifs H , an accomplifhed young lady, with

light eyes and hair, was feized with convulfions of
her iiaibs, with hiccough, and efforts to vomit,

more

SECT. III. 5, MOTIONS OF THE RETINA. 29

more violent than words can exprefs ; thefe conti-
nued near an hour, and were fucceeded with a ca-
taleptic fpafm of one arm, with the hand applied to
her head ; and after about twenty minutes thefe
fpafms ceafed, and a talkative reverie fupervened
for near another hour, from which no violence,
which it was proper to ufe, could awaken her.
Thefe periods of convulfions, firft of the mufcles,
and then of the ideas, returned twice a day for fe-
veral weeks; and were at length removed by great
dofes of opium, after a great variety of other me-
dicines and applications had been in vain experi-
enced. This lady was fubject to frequent relapfes,
once or twice a year for many years, and was as
frequently relieved by the fame method.

Mifs W , an elegant young lady, with

black eyes and hair, had fometimes a violent pain
of her fide, at other times a moft painful ftrangury,
which were every day fucceeded by delirium ;
which gave a temporary relief to the painful fpafms.
After the vain exhibition of variety of medicines
and applications by different phyficians, for more
than a twelvemonth, me was directed to take fome
dofes of opium, which were gradually increafed, by
which a drunken delirium was kept up for a day or
two, and the pains prevented from returning. A
flefh diet, with a little wine or beer, inftead of the
low regimen fhe had previoufly ufed, in a few
weeks completely eftabliflied her health ; which,
except a few relapfes, has continued for many
years.

9. Laflly, as we advance in life all the parts of
the body become more rigid, and are rendered lefs
fufceptible of new habits of motion, though they
retain thofe that were before eftablifhed. This is
fenfibly obferved by thofe who apply themfelves
late in life to mufic, fencing, or any of the mecha-
nic arts. In the fame manner many elderly peo-

D 2 pic

30 MOTIONS OF THE RETINA. SECT. III. 6.

pie retain the ideas they had learned early in life,
but find great difficulty in acquiring new trains of
memory ; infomuch that in extreme old age we
frequently fee a forgetfulnefs of the bufinefs of yef-
terday, and at the fame time a circumftantial re-
membrance of the amufements of their youth ; till
at length the ideas of recollection and activity of
the body gradually ceafe together — fuch is the con-
dition of humanity ! — and nothing remains but the
vital motions and fenfations.

VI. i. In oppofition to this doctrine of the pro-
duction of our ideas, it may be afked, if fome of
our ideas, like other animal motions, are volunta-
ry, why can we not invent new ones, that have
not been received by perception ? The anfwer will
be better underftood after having perufed the fuc-
ceeding lection, where it will be explained, that
the mufcular motions likewife are originally excited
by the ftimulus of bodies external to the moving
organ ; and that the will has only the power of re-
peating the motions thus excited.

2. Another objector may alk, Can the motion of
an organ of fenfe referable an odour or a colour ?
To which I can only anfwer, that it has not been
dernonflrated that any of our ideas refemble the ob-
jects that excite them : it has generally been be-
lieved that they do not ; but this ftiall be difcuffed
at large in Seel. XIV.

5. There is another objection that at firft view
would feem lefs eafy to furmount. After the am-
putation of a foot or a finger, it has frequently hap-
pened, that an injury being offered to the (lump of
the amputated limb, whether from cold air, too
great preffure, or other accidents, the patient has
complained of a fenfation of pain in the foot or
finger, that was cut off. Does not this evince that
all our ideas are excited in the brain, and not in
the organs of fenfe ? This objection is anfwered,

by

SECT. III. 7. MOTIONS OF THE RETINA. 31

by obferving that our ideas of the (hape, place, and
folidity of our limbs, are acquired by our organs
of touch and of fight, which are fituated in our
fingers and eyes, and not by any fenfations in
the limb itfelf.

In this cafe the pain or fenfation, which formerly
has arifen in the foot or toes, and been propagated
along the nerves to the central part of the fenfo-
rium, was at the fame time accompanied with a
vifible idea of the fhape and place, and with a tan-
gible idea of the folidity of the affected limb : now
when thefe nerves are afterwards affected by any
injury done to the remaining flump with a fimilar
degree or kind of pain, the ideas of the fhape,
place, or folidity of the loft limb, return by affo-
ciation ; as thefe ideas belong to the organs of fight
and touch, on which they were firfl excited.

4. If you wonder what organs of fenfe can be
excited into motion, when you call up the ideas of
wifdom or benevolence, which Mr. Locke has
termed abftracled ideas ; I alk you by what organs
of fenfe you firft became acquainted with thefe
ideas ? And the anfwer will be reciprocal ; for it is
certain that all our ideas were originally acquired
by our organs of fenfe ; for whatever excites our
perception muft be external to the organ that per-
ceives it, and we have no other inlets to knowledge
but by our perceptions : as will be further explain-
ed in Section XIV. and XV. on the Productions and
Clafles of Ideas.

VII. If our recollection or imagination be not a
repetition of animal movements, I afk, in my turn,
What is it ? You tell me it confifts of images or
pictures of things. Where is this extenfive canvas
hung up ? or where are the numerous receptacles
in which thofe are depofited ? or to what elfe in the
animal fyftem have they any fimilitude ?

That

ANIMAL CAUSATION. SECT. IV. i.

^ pleafing picture of objects, reprefented in
miniature on the retina of the eye, feems to have
given rife to this illufive oratory ! It was forgot that
this reprefentation belongs rather to the laws of
light, than to thofe of life ; and may with equal ele-
gance be feen in the camera obfcura as in the eye ;
and that the picture vaniflies for ever, when the
object is withdrawn.

SECT. IV.

LAWS OF ANIMAL CAUSATION.

I. The fibres, which conftitute the mufcles and
organs of fenfe, poflefs a power of contraction.
The circumftances attending the exertion of this
power of CONTRACTION constitute the laws of ani-
mal motion, as the circumftances attending the ex-
ertion of the power of ATTRACTION conftitute the
laws of motion of inanimate matter.

II. The fpirit of imagination is the immediate
caufe of the contraction of animal fibres, it refides
in the brain and nerves, and is liable to general or
partial diminution or accumulation.

III. The ftimulus of bodies external to the mov-
ing organ is the remote caufe of the original con-
tractions of animal fibres.

IV. A certain quantity of ftimulus produces ir-
ritation, which is an exertion of the fpirit of ani-
mation exciting the fibres into contraction.

V. A certain quantity of contraction of animal
fibres, if it be perceived at all, produces pleafure ;

a great-

Seer IV. 7. ANIMAL CAUSATION. 33

a greater or lefs quantity of contraction, if it be
perceived at all, produces pain ; thefe conftitute
fenfation.

VI. A certain quantity of fenfation produces de-
lire or averfion ; thefe conftitute volition.

VII. All animal motions which have occurred at
the fame time, or in immediate fucceffion, become
fo connected, that when one of them is reproduced,
the other has a tendency to accompany or fucceed it.
When fibrous contractions fucceed or accompany
other fibrous contractions, the connection is termed
affociation ; when fibrous contractions fucceed fen-
forial motions, the connection is termed caufation ;
when fibrous and fenforial motions reciprocally in-
troduce each other, it is termed catenation of ani-
mal motions. All thefe connections arefaid to be pro-
duced by habit, that is, by frequent repetition. Thefe
laws of animal caufation will be evinced by numerous
facts, which occur in our daily exertions; and will
afterwards be employed to explain the more recon-
dite phaenomena of the production, growth, dif-
cafes, and decay of the animal fyftem.

SECT,

34 SENSORIAL FACULTIES. Sicr.V.

SECT. V.

OF THE FOUR FACULTIES OR MOTIONS OF THE SEN-
SORIUM.

I. Four fenforial powers. 2. Irritation, fenfatlon^ vo-
lition, ajjoclation defined. 3. Senforial motions dif-
tlnguijhed from fibrous motions.

1. THE fpirit of animation has four different
modes of action, or in other words the animal fen-
forium poffeffes four different faculties, which are
occaiionally exerted, and caufe all the contractions
of the fibrous parts of the body, Thefe are the
faculty of caufing fibrous contractions in confe-
quence of the irritations excited by external bodies,
in confequence of the fenfationsof pleafure or pain,
in confequence of volition, and in confequence of
the affociations of fibrous contractions with other
fibrous contractions, which precede or accompany
them.

Thefe four faculties of the fenforium during their
inactive (late are termed irritability, fenfibility, vo-
luntarity, and affectability ; in their active flate
they are termed as above, irritation, fenfation, vo-
lition, afibciation.

2. IRRITATION is an exertion or change of fome
extreme part of the fenforium reading in the muf-
cles or organs of fenfe, in confequence of the ap-
pulfes of external bodies.

SENSATION is a,n exertion or change of the cen-
tral parts of the fenforium, or of the whole of it,
beginning at fome of thofe extreme parts of it,
which refide in the mufcles or organs of fenfe.

VOLITION

SECT.V. SENSORIAL FACULTIES. 35

VOLITION is an exertion or change of the central
parts of the fenforium, or the whole of ^it, termi-
nating in fome of thofe extreme parts of it, which
refide in the mufcles or organs of fenfe.

ASSOCIATION is an exertion or change of fome
extreme part of the fenforium refiding in the muf-
cles or organs of fenfe, in confequence of fome an-
tecedent or attendant fibrous contractions.

3. Thefe four faculties of the animal fenforium
may at the time of their exertions be termed mo-
tions without impropriety of language ; for we
cannot pafs from a ftate of infenfibility or inaction
to a ftate of fenfibility or of exertion without fome
change of the fenforium, and every change includes
motion. We fhall therefore fometimes term the
above defcribed faculties fenforial motions to diftin-
guifli them from fibrous motions ; which latter ex-
preffion includes the motions of the mufcles and or-
gans of fenfe.

The adive motions of the fibres, whether thofe
of the mufcles or organs of fenfe, are probably
fimple contractions ; the fibres being again elongat-
ed by antagonifl mufcles, by circulating fluids, or
fometimes by elaftic ligaments, as in the necks of
quadrupeds. The feniorial motions, which confti-
tute the fenfations of pleafure or pain, and which
conftitute the fenfations of pleafure or pain, and
which conftitute volition, and which caufe the fi-
brous contractions in confequence of irritation or
of aflbciation, are not here fuppofed to be fluctua-
tions or refluctuations of the fpirit of animation ;
nor are they fuppofed to be vibrations or revibrati-
ons, nor condenfations or equilibrations of it; but
to be changes or motions of it peculiar to life.

SECT.

36 FIBROUS CONTRACTIONS. SECT. VI. i,

•Js-mm ii^j "i \i> Taaofmxa a* srvfo, .

SECT. VL

OF THE FOUR CLASSES OF FIBROUS MOTIONS.

i* *JS ' i

I. Origin of fibrous contractions. II. Diftribution of
them into four c/qffes, irritative motions y fenfit'we mo*
tions, 'voluntary motions, and officiate motions, defined.

I. ALL the fibrous contractions of animal bodies
originate from the fenforium, and refolve them-
felves into four clafles, correfpondent with the four
powers or motions of the fenforium above defcrib-
ed, and from which they have their caufation.

1. Thefe fibrous contractions were originally
caufed by the irritations excited by objects, which
are external to the moving organ. As the pulfati-
ons of the heart are owing to the irritations excited
by the ftimulus of the blood ; and the ideas of per-
ception are owing to the irritations excited by ex-
ternal bodies.

2. But as painful or pleafurable fenfations fre-
quently accompanied thofe irritations, by habit thefe
fibrous contractions became caufable by the fenfa-
tions, and the irritations ceafed to be neceflary to
their production. As the fecretion of tears in grief
is caufed by the fenfation of pain ; and the ideas of
imagination, as in dreams or delirium, are excited
by the pleafure or pain, with which they were for-
merly accompanied.

3. But as the efforts of the will frequently ac-
companied thefe painful or pleafurable fenfations, by
habit the fibrous contractions became caufable by
volition ; and both the irritations and fenfations
ceafed to be neceflary to their production. As the

deliberate

SECT. VI. 2. FIBROUS CONTRACTIONS. 37

deliberate locomotions of the body, and the ideas
of recolleftion, as when we will to repeat the alpha-
bet backwards.

4. But as many of thefe fibrous contractions fre-
quently accompanied other fibrous contractions, by
habit they became caufable by their affociations
with them; and the irritations, fenfations, and vo-
lition, ceafed to be neceffary to their production.
As the actions of the mufcles of the lower limbs in
fencing are affociated with thofe of the arms ; and
the ideas of fuggeftion are affociated with other
ideas, which precede or accompany them ; as in re-
peating carelefsly the alphabet in its ufual order af-
ter having began it.

II. We fhall give the following names to thefe
four claffes of fibrous motions, and fubjoin their
definitions.

1. Irritative motions. That exertion or change
of the fenforium, which is caufed by the appulfes of
external bodies, either fimpiy fubfides, or is fuc-
ceeded by fenfation, or it produces fibrous motions ;
it is termed irritation, and irritative motions are
thofe contractions of the mufcular fibres, or of the
organs of fenfe, that are immediately confequent
to this exertion or change of the fenforium.

2. Senfitive motions. That exertion or change
of the fenforium, which conftitutes pleafure or
pain, either fimpiy fubfides, or is fucceeded by vo-
lition, or it produces fibrous motions ; it is termed
fenfation, and the fenfitive motions are thofe con-
tractions of the mufcular fibres, or of the organs
of fenfe, that are immediately confequent to this
exertion or change of the fenforium.

3. Voluntary motions. That exertion or change
of the fenforium, which conftitutes defire or aver-
fion, either fimpiy fubfides, or is fucceeded by
fibrous motions \ it is then termed volition, and vo-
luntary

38 IRRITATIVE MOTIONS. SECT. VII. r.

luntary motions are thofe contractions of the muf-
cular fibres, or of the organs of fenfe, that are im-
mediately confequent to this exertion or change of
the fenforium.

4. Affociate motions. That exertion or change
of the fenforium, which accompanies fibrous mo-
tions, either limply fubfides, or is fucceeded by
fenfation or volition, or it produces other fibrous
motions ; it is then termed affociation, and the
affociate motions are thofe contractions of the muf-
cular fibres, or of the organs of fenfe, that are im-
mediately confequent to this exertion or change of
the fenforium.

SECT. VII.

OF IRRITATIVE MOTIONS.

I. i. Some mufeular motions are excited by perpetual
irritations, i. Others more frequently by fenfations.
3. Others by volition. Cafe of involuntary ft retch-
ings in paralytic limbs. 4. Some fenfual motions are
excited by perpetual irritations. 5. Others more fre-
quently by fenfation or volition.

II. i. Mufeular motions excited by perpetual irrita-
tions occajionally become obedient to fenfation and to
volition. 2. And the fenfual motions.

III. i. Other mufeular motions are ajfociated with the
irritative ones. 2. And other ideas with irritative
ones. Of letters, language, hieroglyphics. Irrita-
tive ideas exift without our attention to them.

vrf " -jb; V> ,Vj.".-..^.-^--.--vfe.:r'.fii- Tj$fb •,*«'*£

I. i. MANY of our mufeular motions are ex-
cited by perpetual irritations, as thofe of the heart

and

SECT. VII. i. IRRITATIVE MOTIONS. 39

and arterial fyftem by the circumfluent blood-
Many other of them are excited by intermitted ir-
ritations, as thofe of the ftomach and bowels by the
aliment we fwallow ; of the bile-ducts by the bile ;
of the kidneys, pancreas, and many other glands,
by the peculiar fluids they feparate from the blood ;
and thofe of the lacteal and other fubfequent veflels
by the chyle, lymph, and moifture of the atmofphere.
Thefe motions are accelerated or retarded, as their
correfpondent irritations are increafed or diminifhed,
without our attention or confcioufnefs, in the fame
manner as the various fecretions of fruit, gum, re-
fin, wax, and honey, are produced in the vegeta-
ble world, and as the juices of the earth and the
mpifture of the atmofphere are abforbed by their
roots and foliage.

2. Other mufcular motions, that are moft fre-
quently connected with our fenfations, are thofe of
the fphincters of the bladder and anus, and the muf-
culi erectores penis, were originally excited into
motion by irritation, for young children make wa-
ter, and have other evacuations without attention
to thefe circumftances ; " et primis etiam ab incu-
nabulis tenduntur faepius puerorum penes, amore
nondum expergefacto." So the nipples of young
women are liable to become turgid by irritation,
long before they are in a fituation to be excited by
the pleafure of giving milk to the lips of a child.

3. The contractions of the larger mufcles of our
bodies, that are mod frequently connected with
volition, were originally excited into action by in-
ternal irritations : as appears from the ftretching or
yawning of all animals after long fleep. In the be-
ginning of fome fevers this irritation of the mufcles
produces .perpetual ftretching and yawning ; in
other periods of fever an univerfal reftleflhefs arifes
from the fame caufe, the patient changing the at-
titude of his body every minute. The repeated

ftruggles

40 IRRITATIVE MOTIONS, SECT. VII. I.

ftruggles of the foetus in the uterus muft be owing
to this internal irritation : for the foetus can have
no other inducement to move its limbs but the tse-
dium or irkfomenefs of a continued pofture.

The following cafe evinces, that the motions of
ftretching the limbs after a continued attitude are
not always owing to the power of the will. Mr.
Dean, a mafon, of Auftry in Leicefterfliire, had
the fpine of the third vertebra of the back enlarg-
ed ; in fome weeks his lower extremities became
feeble, and at length quite paralytic : neither the
pain of blifters, the heat of fomentations, nor the
utmoft efforts of the will could produce the lead
motion in thefe limbs ; yet twice or thrice a day
for many months his feet, legs, and thighs, were
affected for many minutes with forcible ftretch-
Ings, attended with the fenfation of fatigue ; and
he at length recovered the ufe of his limbs, though
the fpine continued protuberant. The fame cir-
cum fiance is frequently feen in a lefs degree in the
common hemiplagia ; and when this happens, I
have believed repeated and flrong mocks of electri-
city to have been of great advantage.

4. In like manner the various organs of fenfe are
originally excited into motion by various external
ftimuli adapted to this purpofe, which motions are
termed perceptions or ideas ; and many of thefe
motions during our waking hours are excited by
perpetual irritation, as thofe of the organs of hear-
ing and of touch. The former by the conftant low
indiftinct noifes that murmur around us, and the
latter by the weight of our bodies on the parts
which fupport them ; and by the unceafing varia-
tions of the heat, moifture, and preflure of the at-
mofphere ; and thefe fenfual motions, precifely as
the mufcular ones above mentioned, obey their cor-
refpondent irritations without our attention or con-
fcioumefs.

5. Other

SECT. VII. 2. IRRITATIVE MOTIONS. 41

5. Other clafies of our ideas are more frequent-
ly excited by our fenfations of pleafure or pain, and
others by volition : but that thefe have all been
originally excited by ftimuli from external objects,
and only vary in their combinations or reparations,
has been fully evinced by Mr. Locke : and are by
him termed the ideas of perception in contradiilinc-
tion to thofe, which he calls the ideas of reflec-
tion.

II. i. Thefe mufcular motions, that are excited
by perpetual irritation, are neverthelefs occafion-
ally excitable by the fenfations of pleafure or pain,
or by volition ; as appears by the palpitation of the
heart from fear, the increafed fecretion of faliva at
the fight of agreeable food, and the glow on the
Ikin of thofe who are amamed. I here is an inftance
told in the Philofophical Tr an factions of a man, who
could for a time flop the motion of his heart when
he pleafed ; and Mr. D. has often told me, he could
Ib far increafe the periftaltic motion of his bowels
by voluntary efforts, as to produce an evacuation
by ftool at any time in half an hour.

2. In like manner the fenfual motions, or ideas,
that are excited by perpetual irritation, are never-
thelefs occafionally excited by fenfation or volition ;
as in the night, when we liften under the influence
of fear, or from voluntary attention, the motions
excited in the organ of hearing by the whifpering
of the air in our room, the pulfation of our own ar-
teries, or the faint beating of a diltant watch, be-
come objects of perception.

ill. Innumerable trains or tribes of other motions
are aflbciated with thefe mufcular motions which
are excited by irritation ; as by the ftimulus of the
blood in the right chamber of the heart, the lungs
are induced to expand themfelves ; and the pecto-
ral and intercoftal mufcles, and the diaphragm, act
at the fame time by their aiTociations with them.

And

4* IRRITATIVE MOTIONS. SECT. VII. 3.

And when the pharynx is irritated by agreeable
food, the mufcles of deglutition are brought into
action by aflbciation. Thus when a greater light
falls on the eye, the iris is brought into action with-
out our attention ; and the ciliary procefs, when
the focus is formed before or behind the retina, by
their aflbciations with the increafed irritative mo-
tions of the organ of vifion. Many common ac-
tions of life are produced in a fimilar manner. If
a fly fettle on my forehead, whilft I am intent on
my prefent occupation, I diflodge it with my finger,
without exciting my attention or breaking the train
of my ideas.

2. In like manner the irritative ideas fuggeft to
us many other trains or tribes of ideas that are af-
fociated with them. On this kind of connection,
language, letters, hieroglyphics, and every kind of
fymbol, depend. The iymbols themfelves produce
irritative ideas, or fenfual motions, which we do
not attend to ; and other ideas, that are fucceeded
by fenfation, are excited by their aflbciation with
them. And as thefe irritative ideas make up apart
of the chain of our waking thoughts, introducing
other ideas that engage our attention, though them-
felves are unattended to, we find it very difficult to
inveftigate by what fteps many of our hourly trains
of ideas gain their admittance.

It may appear paradoxical, that ideas can exift,
and not be attended to ; but all our perceptions are
ideas excited by irritation, and fucceeded by fenfa-
tion. Now when thefe ideas excited by irritation
give us neither pleafure nor pain, weceafe to attend
to them. Thus whilft 1 am walking through that
grove before my window, I do not run againft the
trees or the benches,^ though my thoughts are ftre-
nuoufly exerted on fome other object. This leads
us to a diftinct knowledge of irritative ideas, for the
idea of the tree or bench, which I avoid, exifts on

my

SECT. VIII. i. SENSITIVE MOTIONS. 4$

my retina, and induces by affociation the aftion of
certain locomotive mufcles ; though neither itfelf
nor the actions of thole mufcles engage my atten*
tion.

Thus whilft we are converting on this fubjeclr,
the tone, note, and articulation of every indivi-
dual word forms its correfpondent irritative idea on
the organ of hearing ; but we only attend to the
aflfociated ideas, that are attached by habit to thefe
irritative ones, and are fucceeded by fenfation ; thus
when we read the words " PRINTING-PRESS" we do
not attend to the fiiape, fize, or exiftence of the let-
ters which compofe thefe words, though each of
them excites a correfpondent irritative motion of
our organ of viiion, but they introduce by affocia-
tion our idea of the moil ufeful of modern inven-
tions ; the capacious refervoir of human knowledge,
whofe branching ftreams diffufe fciences, arcs, and
morality, through all nations and all ages.

SECT. VIJI.

OF SENSITIVE MOTIONS.

I. i. Senjltwe. .mufcular motions were originally excited
Into aclion by irritation. 2. And fenfttive fenfual
motions y ideas of 'imagination , dreams* II. i. 6V/z-
Jttive mufcular motions are occasionally obedient to vo-
lition. 2. And fenjitive fenfual motions. III. i.
Other mufcular motions are officiated with the fenji-
five ones. 2. And other fenfual motions.

I. i. MANY of the motions of our mufcles,
that are excited into action by irritation, are at

K the

H SENSITIVE MOTIONS. SECT. VIII. r

the fame time accompanied with painful or pleafur-
able fenfations ; and at length become by habit
caufable by the fenfations. Thus the motions of
the fphincters of the bladder and anus were origi-
nally excited into action by irritation ; for young
children give no attention to thefe evacuations ;
but as foon as they become fenfible of the inconve-
nience of obeying thefe irritations, they fuffer the
water or excrement to accumulate, till it difagree-
ably affects them ; and the action of thofe fphinc-
ters is then in confequence of this difagreeable fen-
fation. So the fecretion of faliva, which in young
children is copioufly produced by irritation, and
drops from their mouths, is frequently attended
with the agreeable fenfation produced by the maf-
tication of tafteful food ; till at length the fight of
fuch food to a hungry perfon excites into action
thefe falival glands j as is feen in the flavering of
hungry dogs.

The motions of thofe mufcles, which are affected
by lafcivious ideas, and thofe which are exerted in
fmiling, weeping, flatting from fear, and winking
at the approach of danger to the eye, and at times
the actions of every large inufcle of the body be-
come caufable by our fenfations. And all thefe mo-
tions are performed with ftrength and velocity in
proportion to the energy of the fenfation that
excites them, and the quantity of fenforialower.

2. Many of the motions of our organs of fenfe,
or ideas, that were originally excited into action by
irritation, become in like manner more frequently
caufable by our fenfations of pleafure or pain. Theie
motions are then termed the ideas of imagination,
and makeup all the fcenery and tranfactions of our
dreams. Thus when any painful or pleafurable fen-
fations poflefs us, as of love, anger, fear ; whether
in our fleep or waking hours, the ideas, that have

been

SECT. VIII. 3. SENSITIVE MOTIONS. 45

been formerly excited by the objefts of thefe fenfa-
tions, now vividly recur before us by their connec-
tion with thefe fenfations themfelves. So the fair
fmiling virgin, that excited your love by her pre-
fence, whenever that fenfation recurs, rifes before
vou in imagination ; and that with all the pleafing
circumftances, that had before engaged your atten-
tion. And in fleep, when you dream under the in-
fluence of fear, all the robbers, fires, and precipices,
that you formerly have feen or heard of, arife be-
fore you with terrible vivacity. All thefe fenfuai
motions, like the mufcular ones above mentioned,
are performed with ftrength and velocity in pro-
portion to the energy of the fenfation of pleafure
or pain, which excites them, and the quantity of
fenforial power.

III. i. Many of thefe mufcular motions above
defcribed, that are mod frequently excited by our
fenfations, are neverthelefs occafionally caufable by
volition ; for we. can frnile or frown ipontaneoufly,
can make water before the quantity or acrimony of
the urine produces a difagreeable fenfation, and can
voluntarily rnaflicate a naufeous drug, or fwallow a
bitter draught, though our fenfation would ftrongly
diffuade us.

2. In like manner the fenfuai motions, or ideas,
that~are mod frequently excited by our fenfations,
are neverthelefs occafionally caufeable by volition,
as we can fponcaneoufly call up laft night's dream
before us, tracing it induftrioufly ftep by ftep
through all its variety of fcenery and t ran faction ;
or can voluntarily examine or repeat the ideas, that
have been excited by our difgutt or admiration.

III. i. Innumerable trains or tribes of motions
are affociated with thefe fenfitive mufcular motions
above mentioned ; as when a drop of water failing
into the wind-pipe difagreeably affects the air-veflcis
of the lungs, they are excited into violent aclion ;

E 2 and

46 VOLUNTARY MOTIONS. SECT, IX. i.

and with thefe fenfitive motions are aflbciated the
adtions of the pe&oral and intercoftal mufcles, and
the diaphragm ; till by their united and repeated
fucceilions the drop is returned through the larynx.
The fame occurs when any thing difagreeably affects
the noftrils, or the ftomach, or the uterus ; variety
of mufcles "are excited by aflbciation into forcible
action, not to be fuppreffed by the utmoft efforts
of the will ; as in freezing/ vomiting, and parturi-
tion.

2. In like manner with thefe fenfitive fenfual
motions, or ideas of imagination, are affociated
many other trains or tribes of ideas, which by fome
writers of metaphyfics have been claffed under the
terms of refemblance, caufation, and contiguity j
and will be more fully treated of hereafter.

SECT. IX.

OF VOLUNTARY MOTIONS.

I. i . Voluntary mufcular motions are originally excited
by irritations. 2. And voluntary ideas. Of reajon.
II. i. Voluntary mufcular motions are occasionally
caufable by fenfations. 2. And voluntary ideas. 111.
i. Voluntary mufcular motions are cccafionally obedient
to Irritations. 2. And voluntary ideas. IV. i. Vo-
luntary mufcular motions are affociated 'with other muf-
cular motions. 2. And voluntary ideas.

WHEN pleafure or pain affecl the animal fyftem,
many of its motions both nuifcular and fenfual are

brought

SECT. IX. i. VOLUNTARY MOTIONS. 47

brought into aftion ; as was {hewn in the preceding
fection, and were called fenfitive motions. The
general tendency of thefe motions is to arreft and
to poflefs the pleafure, or to diflodge or avoid the
pain : but if this cannot immediately be accom-
plifhed, defire or averfion are produced, and the
motions in confequence of this new faculty of the
fenforium are called voluntary.

1. i. Thofe mufcles of the body that are attach-
ed to bones, have in general their principal conne-
tions with volition, as 1 move my pen or raife my
body. Thefe motions were originally excited by
irritation, as was explained in the fection on that
fubjecl, afterwards the fenfations of pleafure or pain,
that accompanied the motions thus excited, induc-
ed a repetition of them ; and at length many of
them were voluntarily practifed in fucceiiion or in
combination for the common purpofes of life, as in
learning to walk, or to fpeak ; and are performed
with ftrength and velocity in proportion to the
energy of the volition, that excites them, and the
quantity of fenforial power.

2. Another great clafs of voluntary motions con-
fifts of the ideas of recollection. We will to repeat
a certain train of ideas, as of the alphabet back-
wards ; and if any ideas, that do not belong to this
intended train, intrude themfelves by other con-
nections, we will to reject them, and voluntarily
perfifl in the determined train. So at my approach
to a houfe which I have but once vilited, and that
at the diftance of many months, I will to recollect
the names of the numerous family I expect to fee
there, and I do recollect them.

On this voluntary recollection of ideas our facul-
ty of reafon depends, as it enables us to acquire an
idea of the diffimilitude of any two ideas. Thus if
you voluntarily produce the idea of a right-angled
triangle, and then of a fquare ; and after having

excited

48 VOLUNTARY MOTIONS. SECT. IX. 3.

excited thefe ideas repeatedly, you excite the idea
of their difference, which is that of another right-
angled triangle inverted over the former ; you are
faid to reafon upon this- fubject, or to compare your
ideas.

Thefe ideas of recollection, like the mufcular mo-
tions above1 mentioned, were originally excited by
the irritation of external bodies, and were termed
ideas of perception: afterwards the pleafure or
pain, that accompanied thefe motions, induced a
repetition of them in the abfence of the external
body, by which they were fir ft excited ; and then
they were termed ideas of imagination. At length
they become voluntarily practifed in fuccceflion or
in combination for the common purpofes of life;"
as when we make ourfelves matters of the hiftory of
mankind, or of the fciences they have inveftigat-
cd ; and are then called ideas of recollection ; and
are performed with ftrength and velocity in pro-
portion to the energy of the volition that excites
them, and the quantity of fenforial power.

II. i. The mufcular motions above defcribed,
that are moft frequently obedient to the will, are
neverthelefs occaiionally caufable by painful or plea-
furable fenfation, as in the ftarting from fear, and
the contraction of the calf of the leg in the cramp.

2. In like manner the fenfual motions, or ideas,
that are moft frequently connected with volition,
are neverthelefs occafionally caufable by painful or
pleafurable fenfation. As the hifiories of men, or
the defcription of places, which we have volunta-
rily taken pains to remember, fometimes occur to
us in our dreams.

Hi. i. The mufcular motions that are generally
fubfervient to volition, are alfo occafionally caufa-
ble by irritation, as in ftretching the limbs after
fleep, and yawning. In this manner a contraction
of the arm is produced by paffing the electric fluid

from

SECT. IX. 4. VOLUNTARY MOTIONS. 49

from the Leyden phial along its rnufcles ; and that
even though the limb is paralytic. The fudden
motion of the arm produces a difagreeable fenfation
in the joint, but the mufcles feein to be brought
into aclion (imply by irritation.

2. The ideas, that are generally fubfervient to
the will, are in like manner occafionally excited by
irritation ; as when we view again an object, we
have before well ftudied, and often recollected.

IV. i. Innumerable trains or tribes of motions
are affociated with thefe voluntary mufcular mo-
tions above mentioned ; as when I will to extend
my arm to a diftant object, fome other mufcles are
brought into action, and preferve the balance of
my body. And when I wi(h to perform any fleady
exertion, as in threading a needle, or chopping
with an ax, the pectoral mufcies are at the iame
time brought into action to preferve the trunk of
the body motionlefs, and we ceafe to refpire for a
time.

2. In like manner the voluntary fenfual motions,
or ideas of recollection, are affociated with many
other trains or tribes of ideas. As when I volunta-
rily recollect a gothic window, that I faw fome time
ago, the whole front of the cathedral occurs to me
at the fame time.

SECT.

5* -ASSOCIATE MOTIONS. SECT. X. i.

SECT. X.

OF ASSOCIATE MOTIONS.

I, i . Many mufcular motions excited by irritations in
. trains or tribes become officiated. 2. A W many ideas.
II. i. Many fenfitive mufcular motions become af-
fociated. ^• And many fenfitive ideas . III. i. Many
voluntary mufcular motions become officiated. 2. And
then become obedient to fenfation or irritation. 3.
And many voluntary ideas become officiated*

ALL the fibrous motions, whether mufcular or
fenfual, which are frequently brought into action
together, either in combined tribes, or in fucceflive
trains, become fo connected by habit, that when
one of them is reproduced the others have a tendency
to fucceed or accompany it.

I. i. Many of our mufcular motions were ori-
ginally excited in fucceflive trains, as the contrac-
tions of the auricles and of the ventricles of the
heart ; and others in combined tribes, as the vari-
ous divifions of the mufcles which compofe the calf
of the leg, which were originally irritated into fyn-
chronous action by the txdium or irkfomenefs of a
continued pofture. By frequent repetitions thefe
motions acquire affociations, which continue dur-
ing our lives, and even after the deftruction of
the greateft part of the fenforium ; for the heart
of a viper or frog will continue to puifate long
after it is taken from the body -, and when it
has entirely ceafed to move, if any part of it is
goaded with a pin, the whole heart will again re-
new its pulfations. This kind of connection we
fliall term irritative aflbciation, to diftinguifli it
from fenfitive and voluntary aflbciations.

2. In

SECT. X. 2. ASSOCIATE MOTIONS. 5r

2. In like manner many of our ideas are origi-
nally excited in tribes ; as all the objects of fight,
after we become fo well acquainted with the laws
of vifion, as to diftinguifli figure and diftance as well
as colour ; or in trains, as while we pafs along the
objects that furround us. The tribes thus receiv-
ed by irritation become affociated by habit, and
have been termed complex ideas by the writers of
metaphyfics, as this book or that orange. The
trains have received no particular name, but thefe
are alike affociations of ideas, and frequently con-
tinue during our lives. So the tafte of a pine-ap-
ple, though we eat it blindfold, recalls the colour
and fhape of it ; and we can fcarcely think on foli-
dity without figure.

II. i. By the various efforts of our fenfations to
acquire or avoid their objects, many mufcies are
daily brought into fucceffive or fynchronous ac-
tions ; thefe become ailociated by habit, and £re
then excited together with great facility, and in
many inftances gain indiflbluble connections. So
the play of puppies and kittens is a reprefentation
of their mode of fighting or of taking their prey ;
and the motions of the mufcles neceflary for thofe
purpoies become afibciated by habit, and gain a
great adroitnefs of action by thefe early repetitions :
fo the motions of the abdominal mufcles, which
were originally brought into concurrent action with
the protrufive motion of the rectum -or bladder by
ienfation, become fo conjoined v/ith them by habit,
that they not only eafily obey thefe fenfations occa-
iioned by the ftimulus of the excrement and urine,
but are brought into violent and unreftrainable ac-
tion in the ftrangury and tenefmus. This kind
of connection we mall term fenfitive aflbciation.

2. So many of our ideas, that have been excited
together or in fucceffion by our fenfations, gain
fynchronous or fucceffive aflbciations, that are fome-

tiaies

52 ASSOCIATE MOTIONS. SECT. X. 3.

times indiflbluble but with life. Hence the idea of
an inhuman or difhonourable action perpetually
calls up before us the idea of the wretch that was
guilty of it. And hence thofe unconquerable anti-
pathies are formed, which forne people have to the
fight of peculiar kinds of food, of which in their in-
fancy they have eaten to excefs or by conftraint.

III. i. In learning any mechanic art, as mufic,
dancing, or the ufe of the fword, we teach many
of our mufcles to act together or in fucceflion by
repeated voluntary efforts ; which by habit become
formed into tribes or trains of aflbciation, and ferve
all our purpofes with great facility, and in fome in-
fiances acquire an indiflbluble union. Thefe mo-
tions are gradually formed into a habit of acting to-
gether by a multitude of repetitions, whilft they
are yet feparately caufable by the will, as is evident
from the long time that is taken up by children in
learning to walk and to fpeak ; and is experienced
by every one, when he firil attempts to fkate upon
the ice or to fwim; thefe we lhali term voluntary
affociation s.

2. All thefe mufcular movements, when they are
thus aflbciated into tribes or trains, become after-
wards not 'only obedient to volition, but to the fen-
fations and irritations ; and the fame movement
compofes a part of many different tribes or trains
of motions. Thus a fingle mufcle, when it acts in
confort with its neighbours on one fide, aflifts to
move the limb in one direction ; and in another,
when it acts with thofe in its neighbourhood on the
other fide ; and in other directions, when it acts
Separately or jointly with thofe that lie immediately
under or above it ; and all thefe with equal facility
after their aflbciations have been well eftablifhed.

The facility, with which each mufcle changes
from one aflbciated tribe to another, and that
either backwards or forwards, is well obfervable

in

SECT. X. 3. ASSOCIATE MOTIONS, 5$

in the mufcles of the arm in. moving the \vind-
lafs of an air-pump ; and the ilownefs of thofe
mufcular movements, that have not been aflbciated
by habit, may be experienced by any one, who
fliall attempt to faw the air quick perpendicularly
with one hand, and horizontally with the other at
the fame time.

3. In learning every kind of fcience we volunta-
rily affociate many tribes and trains of ideas, which
afterwards are ready for all the purpofes either of
volition, fenfation, or irritation ; and in (bine in-
ftances acquire indiffolubie habits of acting together,
fo as to affect our reafonjng, and influence our ac-
tions. Hence the neceflity of a good education.

Thefe affociate ideas are gradually formed into
habits of acting together by frequent repetition,
while they are yet feparately obedient to the will;
as is evident from the difficulty we experience in
gaining fo exact an idea of the front of St. Paul's
church, as to be able to delineate it with accuracy,
or in recollecting a poem of a few pages.

And thefe ideas, thus affociated into tribes, not
only make up the parts of 'the trains of volition,
fenfation, and irritation ; but the fame idea com-
pofes a part of many different tribes and trains of
ideas. So the firnple idea of vvhitenefs compofes a
part of the complex idea of mow, milk, ivory j
and the complex idea of the letter A compofes a
part of the feveral affociated trains of ideas that
make up the variety of words, in which this letter
enters.

The numerous trains of thefe affociated ideas are
divided by Mr. Hume Into three claffes, which he
has termed contiguity, caufation, and refemblance.
Nor mould we wonder to find them thus connected
together, fmce it is the bufinefs of our lives to dif-
pofe them into thefe three claffes ; and we become
valuable to ourfelves and our friends, as we fucceed

in

54 SENSORIAL ACTIONS. SECT. XI. r.

in it. Thofe who have combined an extenfive clafs
of ideas by the contiguity of time or place, are men
learned in the hiftory of mankind, and of the fcien-
ces they have cultivated. Thofe who have connedl-
ed a great clafs of ideas of refemblances, pofTefs the
fource of the ornaments of poetry and oratory, and
of all rational analogy. While thofe who have con-
nected great chffes of ideas ofcaufation, are furnifh-
ed with the powers of producing effects. Thefe are
the men of a&ive wifdom. who lead armies to vic-
tory, and kingdoms to profperty ; or difcover and
improve the fciences, which meliorate and adorn
the condition of humanity.

SECT. XI.

ADDITIONAL OBSERVATIONS ON THE SENSORIAL
POWERS.

I. Stimulation is of various kinds adapted to the organs
of fenfe, to the mufcles, to hollow membranes, and
glands. Some chjctts irritate our fenfes by repeated
impulfes. 11. i. Senfation and volition frequently
ajjeft the whole fenjorium. 2. Emotions, pajfions,
appetites. 3. Origin of .defire and aver/ton. Grite*
rion of voluntary actions, difference of brutes and men.
4. Senfib'dityandvoluntarity. III. Affociations form-
ed before nativity -, irritative motions miftakenfor af-
fociatcd ones.

Irritation.

I. THE various organs of fenfe require various
kinds of flimulation "to excite them into action ;

the

SECT. XL i; SENSORIAL ACTIONS, 55

the particles of light penetrate the cornea and hu-
mours of the eye, and then irritate the naked reti-
na ; fapid particles, diffolved or diffufed in water
or faliva, and odorous ones, mixed or combined
with the air, irritate the extremities of the nerves
of tafle and fmeli j which either penetrate, or are
expanded on the membranes of the tongue and nof-
trils ; the auditory nerves are ilimulated by the vi-
brations of the atmofphere communicated by means
of the tympanum and of the fluid, whether of air or
of water, behind it ; and the nerves of touch by
the hardnefs of furrounding bodies, though the cu-
ticle is interpofed between thefe bodies and the me-
dulla of the nerve.

As the nerves of the fenfes have each their appro-
priated objects, which flimulate them into activity ;
fo the mufcular fibres, which are the terminations
of other fets of nerves, have their peculiar objects,
which excite them into action ; the longitudinal
mufcles are ftimulated into contraction by exten-
lion, whence the ftretching orpandiculation after a
long continued pofture, during which they have
been kept in a ftate of extenfion ; and the hollow
mufcles are excited into action by diftention, as
thofe of the rectum and bladder are induced to pro-
trude their contents from their fenfe of the diften-
tion rather than of the acrimony of thole con-
tents.

There are other objects adapted to ftimulate the
nerves, which terminate in a variety of membranes,
and thofe efpecialiy which form the terminations of
canals ; thus the preparations of mercury particu-
larly affect the falivary glands, ipecacuanha the (to-
mach, aloe the fphincter of the anus, cantharides
that of the bladder, and laftly every gland of the
body appears to be indued with a kind of tafte, by
which it felects or forms each its peculiar fluid from
the blood j and by which it is irritated into acti-
vity.

Many

5$ SENSORIAL ACTIONS. SECT. XT. *J

Many of thefe external properties of bodies, which
ftimulate our organs of fenfe, do not feem to effect
this by a fingle impulfe, but by repeated impulfes ;
as the nerve of the ear is probably not excitable by
a fingle vibration of air, nor the optic nerve by a
lingle particle of light ; which circumftance pro-
duces fome analogy between thofe two fenfes, at
the fame time the fblidity of bodies is perceived by
a fingle application of a folid body to the nerves of
touch, and that even through the-cuticle; and we
are probably poffeiTed of a peculiar fenfe to diftin-
guifli the nice degrees of heat and cold.

The fenfes of touch and of hearing acquaint us
with the mechanical impact and vibration of bodies,
thofe of fmell and tafle feem to acquaint us with
fome of their chemical properties, while the fenfe of
vifion and of heat acquaint us with the exigence of
their peculiar fluids.

Senfation and Volition.

II. Many motions are produced by pleafure or
pain, and that even in contradiction to the power
of volition, as in laughing, or in the ftrangury ;
but as no name has been given to pleafure or pain,
at the time it is exerted fo as to caufe fibrous mo-
tions, we have ufed the term fenfation for this pur-
pofe ; and mean it to bear the fame analogy to plea-
lure and pain,vthat the word volition does to defire
and averfion.

i. It was mentioned in the fifth Section, that,
what we have termed fenfation is a motion of the
central parts, or of the whole fenforium, beginning
at fome extremities of it. This appears firit, be-
caufe our pains and pleafures are always caufed by
our ideas or mufcular motions, which are the mo-
tions of the extremities of the fenforium. And,
fccondly, becaufe the fenfation of pleafure or pain

frequently

"«ECT. XI. 2. SENSOKIAL ACTIONS. 57

frequently continues fome time after the ideas or
mufcular motions which excited it have ceafed:
for we often feel a glow of pleafure from an agree-
able reverie, for many minutes after the ideas, that
were the fubject of it, have efcaped our memory ;
and frequently experience a dejectiotyof fpirits with-
out being able to ailign the caufe of it but by much
recolleclion.

When the fenforial faculty of defire or averfion
is exerted fo as to caufe fibrous motions, it is term-
ed volition ; which is faid in Seel. V. to be a mo-
tion of the central parts, or of the whole fenforium,
terminating in fome of the extremities of it. This
appears, firft, becaufe our defires and averfions al-
ways terminate in recollecting and comparing our
ideas, or in exerting our mufcles ; which are the
motions of the extremities of the fenforium And,
fecondly, becaufe defire or averfion begins, and
frequently continues for a time in the central parts
of the fenforium, before it is peculiarly exerted at
the extremities of it ; for we fometimes feel defire
or averfion without immediately knowing their
objects, and in confequence without immediately
exerting any of our mufcular or fenfual motions to
attain them : as in the beginning of the paflion of
love, and perhaps of hunger, or in the ennui of
indolent people.

Though ienfation and volition begin or termi-
nate at the extremities or central parts of the fen-
forium, yet the whole of it is frequently influenced
by the exertion of thefe faculties, as appears from
their effects on the external habit : for the whole
fkin is reddened by mame, and an univeral tremb-
ling is produced by fear : and every mufcle of the
body is agitated in angry people by the defire of
revenge.

There is another ver ycurious circumftance, which
{hews that fenfation and volition are movements of

the

58 SENSORIAL ACTIONS. SECT. XL 2.

the fenforium in contrary directions ; that is, that
volition begins at the central parts of it, and pro-
ceeds to the extremities ; and that fenfation begins
at the extremities, and proceeds to the central parts :
I mean that thefe two fenforial faculties cannot be
ftrongly exerted at the fame time ; for when we
exert our volition ftrongly, we do not attend to
pleafure or pain ; and converfely, when we are
itrongly affected with the fenfation of pleafure or
pain, we u(e no volition. As will be further ex-
plained in Section XVIII. on fleep, and Section
XXXIV. on volition.

2. All our emotions and paflions feem to arife
out of the exertions of thefe two faculties of the
animal fenforium. Pride, hope, joy, are the names
.of particular pleafures : ihame, defpair, forrow, arc
the names of peculiar pains : and love, ambition,
avarice, of particular defires : hatred, difguft, fear,
anxiety, of particular averfions. Whilft the paf-
lion of anger includes the pain from a recent injury,
and the averfion to the adverfary that occaiioned
it. And companion is the pain we experience at
(the fight of mifery, and the defire of relieving
it.

There is another tribe of defires, which are com-
monly termed appetites, and are the immediate
confequences of the abfence of fome irritative mo-
tions. Thofe, which arife from defect of internal
irritations, have proper names conferred upon
them, as hunger, thirft, luft, and the defire of air,
when our refpiratipn is impaired by noxious va-
pours ; and of warmth, when we are expofed to
too great a degree of cold. But thofe, whofe fti-
niuli are external to the body, are named from the
objects, which are by nature conftituted to excite
them ; thefe defires originate from our paft expe-
rience of the pleafurable fenfations they occafion,

as

SECT. XI. 2. SENSORIAL ACTIONS. 59

as the fmell of an hyacinth, or the tafte of a pine-
apple.

Whence it appears, that our pleafures and pains
are at leaft as various and as numerous as our irri-
tations ; and that our defires and averfions muft be
as numerous as our pleafures and pains. And that
as fenfation is here ufed as a general term for our
numerous pleafures and pains, when they produce
the contractions of our fibres ; fo volition is the
general name for our defires and averfions, when
they produce fibrous contractions. Thus when a
motion of the central parts, or of the whole fenfo-
rium, terminates in the exertion of our mufcles, it
is generally called voluntary aftion ; when it ter-
minates in the exertion of our ideas, it is termed
recolledion, reafoning, determining.

3. As the fenfations of pleafure and pain are ori-
ginally introduced by the irritations of external ob-
jects : fo our defires and averfions are originally in-
troduced by thofe fenfations ; for when the obje<5ts
of our pleafures or pains are at a diftance, and we
cannot inftantaneoufly poflefs the one, or avoid the
other, then defire or averfion is produced, and a
voluntary exertion of our ideas or mufcles fuc-
ceeds.

The pain of hunger excites you to look out for
food, the tree, that (hades you, prefents its odori-
ferous fruit before your eyes, you approach, pluck,
and eat.

The various movements of walking to the tree,
gathering the fruit, and mafticating it, are afTo-
elated motions introduced by their connexion with
ienfation -, but if from the uncommon height of the
tree, the fruit be inacceilible, and you are prevent-
ed from quickly poffefling the intended pleafure,
defire is produced. The confequence of this defire
is, firft, a deliberation about the means to gain the
objeft of pleafure in procefs of time, as it cannot

F be

€o SENSORIAL ACTIONS. Srcr; XI. *

be procured immediately ; and, fecondly, the muf-
cular action necefiary for this purpofe.

You voluntarily call up all your ideas of caufa-
tion, that are related to the effect you defire, and
voluntarily examine and compare them, and at
length determine whether to afcend the tree, or to
gather ftones from the neighbouring brook, is eaiier
to praclife, or more promiling of fuccefs ; and,
finally, you gather the ftones, and repeatedly fling
them to diflodge the fruit.

Hence then we gain a criterion to diftinguifh
voluntary acts or thoughts from thofe caufed by
fenfation » As the former are always employed
about the means to acquire pleafurable objects, or
the means to avoid painful ones ; .while the latter
are employed in the pofleffiun of thofe, which are
already in our power.

Hence the activity of this power of volition pro-
duces'the great difference between the human and
the brute creation. The ideas and the actions of
brutes are almoft perpetually employed about their
prefent pleafures, or their prefent pains ; and, except
In the few inftances which are mentioned in Sec-
tion XVI. oh inftinct, they feldom bufy themfelves
about the meansof procuring future blifs, orof avoid-
ing future mifery ; fo that the acquiring of lan-
guages, the making of tools, and labouring for
jmoney, which are all only the means to procure
pleafures ; and the praying to the Deity, as another
means to procure happinefs, are character! (tic of
human nature.

4. As there are many difeafes 'produced by the
quantity of the fenfation of pain or pleafure being
too great or too little ^ fo are there difeafes produc-
ed by the fufceptibility of the conftitution to mo>
tions caufable by thefe fenfation s being too dull or
too vivid. This fufceptibility of the fyftem to fen-
iitive motions is termed fenfibility, to diftinguifh it

from

SECT. XI. 3. SENSORIAL ACTIONS 61

from fenfation, which is the actual exiftence or
exertion of pain or pleafure.

Other dalles of difeafes are owing to the excef-
five promptitude, or fluggiflinefs of the conftitu-
tion to voluntary exertions, as well as to the quan-
tity of defire or of averfion. This fufceptibility of
the fyftem to voluntary motions is termed volun-
tarity, to diftinguifh it from volition, which is the
exertion of defire or averfion ; thefe difeafes will be
treated of at length in the progrefs of the work.

Affbd&tltih*

III. t. It is not eafy to aflign a caufe, why thofe
animal movements, that have once occurred in fuc-
ceflion, or in combination, mould afterwards have
a tendency to fucceed or accompany each other.
It is a property of animation, and diftinguifhes this
order of being from the other productions of na-
ture.

When a child firft wrote the word man, it was
diftingui/hed in his mind into three letters, and
thofe letters into many parts of letters ; but by re-
peated ufe the word man becomes to his hand in
writing it, as to his organs of fpeech in pronounc-
ing it, but one movement without any delibera-
tion, or fenfation, or irritation, interpofed between
the parts of it. And as many feparate motions of
our mufcles thus become united, and form, as it
were, one motion ; fo each feparate motion before
fuch union may be conceived to confift of many parts
or fpaces moved through ; and perhaps even the
individual fibres of our mufcles have thus gradually
been brought to act in concert, which habits began
to be acquired as early as the very formation of the
moving organs, long before the nativity of the
animal \ as explained in the Se&ion XVI. 2. on in-
ftincl.

F 2 a. There

«J SENSORIAL ACTIONS. Seer. XI. £

2. There are many motions of the body, belong-
ing to the irritative elafs, which might by a hafty
obferver be miftaken for aflbciated ones ; as the pe-
riftaltic motion of the ftomach and inteftines, and
the contrasclrons of the heart and arteries, might be
fuppofed to be aflbciated with the irritative motions
of their nerves of fenfe, rather than to be excited
by the irritation of their mufcular fibres by the dif-
tention, acrimony, or momentum of the blood.
So the diftention, or elongation of mufcles by
objects external to them irritates them into con-
traction, though the cuticle or other parts may
Intervene between the ftimulating body and the
contracting mufcle. Thus a horfe voids his excre-
ment when its weight or bulk irritates the rectum
or fphincter ani. Thefe mufcles act from the irri-
tation of diftention, when he excludes his excre-
ment, but the mufcles of the abdomen and diaph-
ragm are brought into motian by aflbciation with
thofe of the fphincler and rectum.

SECT. XII.

OF STIMULUS, SENSORIAL EXERTION*, AND FIBRQU&
CONTRACTION.

I. Of fibrous contraction, i. Two particles of a Jibre
cannot approach without the intervention offomething,
as in magnet if in, ele£lricity+ elajlicity. Spirit of life
is net ekftric ether. G ah ant's experiments. 2. Con-
traftion of ajibre. 3. Relaxation fucceeds. 4. Sue-
ceffi've contractions, with intervals. Quick pulfe from
debility ) from paucity of blood* W€ak contractions per-
formed

SSCT. XIL OF STIMULUS AND EXERTION. 63

formed In lefs time, and with Jhorter intervals. 5.
5. Laft fituation of the fibres continues after contrac-
tion. 6. Contraction greater than ufual induces plea-
fure or pain. 7. Mobility of the fibres uniform.
Quantity cf fenforial power fluctuates. Constitutes
excitability. If. Of fenforial exertion. \.Animal
motion includes Jlimulus^ fenforial power ^ and contrac-
tile fibres. The fenforial faculties aft feparately or
conjointly. Stimulus of four kinds. Strength and
iveaknefs defined. Senforial power perpetually exkauft-
*d and renewed. Weakncfs from defeci of ftimulus*
From defeci of fenforial power , the dirett and indired
debility of Dr. Brown. Why we become warm in Bux-
ion bath after a time^ and fee well after a time in a
darkifh room, fibres may aft violently , or with their
•wl^ole force ', and yet feebly. Great exertion in inflam-
mation explained. Great ?nufcular force of fome in-
fane people 2. Occqfional accumulation cf fenforial
power in mufcles fubjeft to conft ant Jlimulus. In ani-
mals Jleeping in winter. In eggs, feeds, fchirrous tu-
mours, tendons y bones. 3. Great exertion introduces
pleafure or pain. Inflammation. Libration of the
fyjlem between torpor and activity. Fever-Jits. 4.
Defire and averfion introduced. Excefs of volition
tures fevers. III. Of repeated ftimulus. i. A
Jlimulus repeated too frequently lofes effect. As opium,
wine, grief. Hence old age. Opium and aloes in
fmall dofes. 2. Ajtimulus not repeated too frequently
does not lofe effect. Perpetual movement of the vital
organs. 3. Ajlimulus repeated at uniform times produces
greater effecl. Irritation combined 'with affbciation.
4. Ajlimulus repeated frequently and uniformly may
be withdrawn, and the action of the organ will con-
tinue. Hence the bark cures agues 9 andftrengthens
weak conjlitutions . 5. Defeci, of Jlimulus repeated at
certain intervals caufes fever-Jits. 6. Stimulus long
applied ceafes to aft afecond time. 7. If a Jlimulus
excites fenjation in an organ not ufually excited into fen-

*4 OF STIMULUS AND EXERTION. SECT. XII.

fation. Inflammation is produced. IV. Of ftimulus
greater than natural, i. A Jiimulus greater than
natural diminifhes the quantity of fenforial power in
in general. 2. In particular organs. ^3. Induces the
crgan into fpafmodic actions. 4. Induces the antago-
ntft fibres into aflion. 5. Induces the organ into con-
•vulfive or fixed fpafms. 6. Produces paralyfis of the
organ. V. Of ftimulus lefs than natural, i- Sti-
mulus lefs than natural occafions accumulation of fen-
forial power in general 2. In particular organs,
Jlujhing of the face in a frojiy morning. In fibres fub-
jed to. perpetual Jiimulus only. Quantity of fenforial
•power inverfely as the ftimulus. 3. Induces pain. As
of cold, hunger 9 head-ach. 4. Induces more feeble
and frequent contraction. As in low fevers. Which
are frequently owing to. deficiency ef fenforial power
rather than to deficiency G>f Jiimulus. 5. Inverts fuc-
ceffive trains of motion. Inverts ideas. 6. Induces
faralyfis and death. VI. Cure of increafed exer-
tion, i. Natural cure of exhaujlion of fenforial
power. 2. Decreafe the irritations. Venefedion.
Cold. Abftinence. 3. Prevent the previous cold fit.
Opium. Ear k. Warmth. Anger. SurpHfe. 4, Ex-
cite fome other part of the fyjiem. Opium and warm
bath relieve pains both from defcft and from excefs of
Jiimulus. 5. Fir/I increafe the Jiimulus above, and
then decreafe it beneath the natural quantity. VII.
Cure of decreafed exertion, i. Natural cure by-
accumulation of fenforial power. Ague-fits. Syncops\
2. Increafe the Jiimulation^ by wine^ opium, given
fo as not to intoxicate. Cheerful ideas. 3. Change
the kinds of Jiimulus. 4. Stimulate the officiated or-
gans. Blifters of ufe in heart-burn, and cold extre-
mities. 5. Decreafe thejlimulation for a time, cold
bath. 6. Decreafe the Jlimulation below natural,
and then increafe it above natural* Bark after eme-
tics. Opium after venefeftion. Praclice of Sy den-
ham in chlorofis. 7. Prevent unneceffary expenditure
of fenjorial power. Decumbent pofture, ftlence> dark-

nefs.

SECT. XII. i. OF STIMULUS AND EXERTION. 65

nefs. Pulfe quickened by rifing out of bed. 8. To

the greateft degree of quiefcence apply the leajl flimulus.

Giherwife paralyfts or inflammation of the organ en-
fues. Gin, wine, blifters^ dejlroy by too great ftimu-

lation in fevers with debility. Intoxication in the
Jlightejl degree fucceeded by debility. Golden rule for

determining the beft degree of ftimulus in low fevers.

Another golden rule for determining the quantity of
fpint, which thofe, who are debilitated by drinking

it, may fafely omit.

I. Of Jibrous contraclion.

t. IF two particles of iron lie near each. other
without motion, and after wards approach each other;
it is reafonable to conclude that fomething befides
the iron particles is the caufe of their approxima-
tion ; this invifible fomething is termed magnetifm.
In the fame manner, if the particles, which com-
pofe an animal muicle, do not touch other in the
relaxed ftate of the mufcle, and are brought into
contact during the contraction of the mufcle ; it is
reafbnable to conclude, that fome other agent is
the caufe of this new approximation. For nothing
can act, where it does not exift ; for to act includes
to exift ; and therefore the particles of the mufcu-
lar fibre (which in its ftate of relaxation are fup-
pofed not to touch) cannot affect each other with-
out the influence of fome intermediate agent ; this
agent is here termed the fpirit of animation, or
fenforiai power, but may with equal propriety be
termed the power, which caufes contraction ; or
may be called by another name, which the reader
may choofe to affix to it.

The contraction of a mufcular fibre may be com-
pared to the following electric experiment, which
is here mentioned not as a philotbphical analogy,
but as an illuftration or fimile. to facilitate the coo*

ceptioji

66 OF STIMULUS AND EXERTIOM. SECT. XIL i.

ception of a difficult fubject. Let twenty very fmall
Leyden phials properly coated be hung in a row by
fine filk threads at a fmall diftance from each other ;
let the internal charge of one phial be pofitive, and
of the other negative alternately, if a communica-
tion be made from the internal furface of the firft
to the external furface of the laft in the row, they
will all of them inftantly approach each other,
and thus fhorten a line that might connect them
like a mufcular fibre. See Botanic Garden, p. i.
Canto I. 1. 202, note on Gymnotus.

The attractions of electricity or of magnetifm do
not apply philofophically to the illuftration of the
contraction of animal fibres, fince the force of thofe
attractions increafes in feme proportion inverfely as
the diftance, but in mufcular motion there appears
no difference in velocity or ftrength during the be-
ginning or end of the contraction, but what may
be clearly afcribed to the varying mechanic advan-
tage in the approximation of one bone to another.
Nor can mufcular motion be affimilated with great-
er plaufibility to the attraction of cohefion or elaf-
ticity ; for in bending a fteel fpring, as a fmall
fword, a lefs force is required to bend it the firft
inch than the fecond ; and the fecond than the
third; the particles of fteel on the convex fide of
the bent fpring endeavouring to reftore themfelves
more powerfully the further they are drawn from
each other. See Botanic Garden, P. i. addit.
Note XVIII.

I am aware that this may be explained another
way, by fuppofing the elalHcity of the fpring to
depend more on the compreffion of the particles on
the concave fide than on the extenfion of them on
the convex fide ; and by fuppofing the elafticity of
the elaltic gum to depend more on the refiftance to
the lateral ^compreilion of its particles than to the
longitudinal extenfion of them. Neverthelefs in

mufcular

SECT. XII. i. OF STIMULUS AND EXERTION. 67

mufcular con traction, as above obferved, there ap-
pears no difference in the velocity or force of it at
irs commencement or at its termination ; from
whence we muft conclude that animal contraction
is governed by laws of its own, and not by thofe
of mechanics, chemiftry, magnetifm, or electri-
city.

On thefe accounts I do not think the experiments
conclufive, which were lately publiihed by GaUani,
Volta, and others, to fhew a fiinilitude between the
fpirit of animation, which contracts the inulcular
fibres, and the electric fluid. Since the electric
fluid may act only as a more potent ftimukis exciting
the mufcular fibres into action, and not by fupply-
ing them with a new quantity of the fpirit of life.
Thus in a recent hemiplegia I have frequently ob-
ferved, when the patient yawned and ftretched
himfelf, that the paralytic limbs moved alfo, though
they were totally difobedient to the will. And
when he was electrified by parting fhocks from the
affected hand to the affected foot, a motion of the
paralytic limbs was alfo produced. Now as in the
act of yawning the mufcles of the paralytic limbs
were excited into action by the Itimulus of the irk-
fomenefs of a continued pofture, and not by any
additional quantity of the fpirit of life; fo we
may conclude, that the paffage of the electric fluid,
which produced a limilar effect, acted only as a fti-
mulus, and not by fupplyingany addition of fenfb-
rial power.

If neverthelefs this theory fhould ever become
eftablifhed, a ftimulus muft be called an eductor of
vital ether ; which ftimulus may con lift of lenfati-
on or volition, as in the electric eel, as well as in
the appuites of external bodies ; rwd by drawing off
the charges of vital fluid may occalion the contrac-
tion or motions of the mufcular fibre s, and organs
of fenfe.

a. 'The

€8 OF STIMULUS AND EXERTION. Sscr.XIL U

2. The immediate effect of the action of the fpi-
rit of animation or fenforial power on the fibrous*
parts of the body, whether it acts in the mode of
irritation, ienfation, volition, or afTociation, is a
contraction of the animal fibre, according to the
fecond law of animal caufation. Seel. IV. Thus
the ftinnulus of the blood induces the contraction
of the heart ; the agreeable tafte of a ftrawberry
produces the contraction of the mufcles of deglu-
tition ; the effort of the will contracts the mufcles,
which move the limbs in walking; and by affocia-
tion other mufcles of the trunk are brought into
contraction to preferve the balance of the body.
The fibrous extremities of the organs of fenfe have
been fliewn, by the ocular fpectra in Seel. III. to
fuffer iimilar contraction by each of the above
modes of excitation ; and by their configurations
to conftitute our ideas,

3. After animal fibres have for fome time been
excited into contraction, a relaxation fucceeds, even
though the exciting caufe continues to act. In re-
fpecl to the irritative motions this is exemplified in
the periftaltic contractions of the bowels ; which
ceafe and are renewed alternately, though the fti-
mulus of the aliment continues to be uniformly ap-
plied ; in the fenfitive motions, as in ftrangury,
tenefmus, and parturition, the alternate contracti-
ons and relaxations of the mufcles exift, though
the ftimulus is perpetual. In our voluntary exer-
tions it is experienced, as no one can hang long by
the hands, however vehemently he wills io to do;
and in the aflbciate motions the conftant change of
our attitudes evinces .the neceflity of relaxation to
thofe mufcles, which have been long^n action.

This relaxation of a mufcle after its contraction,
even though the ftimulus continues to be applied,
appears to arife from the expenditure or diminution
pf the fpirit of animation previoufly refidem in the

SECT. XII. i. OF STIMULUS AND EXERTION. 69

mufcle, according to the fecond law of animal cau-
fation in Sect. IV. In thofe conftitutions, which are
termed weak, the fpirit of animation becomes
fooner exhaufted, and tremulous motions are pro-
duced, as in the hands of infirm people, when they
lift a cup to their mouths. The quicker cxhauft-
ion of the fpirit of animation is probably owing to
a lefs quantity of it refiding in the acting fibres,
which therefore more frequently require a fupply
from the nerves, which belong to them.

4. If the fenforial power continues to act, whe-
ther it acts in the mode of irritation, fenfation,
volition, or aflbciation, a new contraction of the
animal fibre fucceeds after a certain interval; which
interval is of fhorter continuance in weak people
than in ftrong ones. This is exemplified in the
fhaking of the hands of weak people, when they
attempt to write. In a manuscript epiftle of one of
rny correfpondents, which is written in a fmall
hand, I obferved from four to fix zigzags in the
perpendicular ftroke of every letter, which mews
that both the contractions of the fingers, and in-
tervals between them, muft have been performed in
very (hort periods of time.

The times of contraction of the mufcles of en-
feebled people being lefs, and the intervals between
thofe contractions being lefs alfo, accounts for the
quick pulfe in fevers with debility, and in dying
animals. The fhortnefs of the intervals between
one contraction and another in weak conftitutions,
is probably owing to the general deficiency of the
quantity of the fpirit of animation, and that there-
fore there is a lefs quantity of it to be received at
each interv/* of the activity of the fibres. Hence
in repeated motions, as of the fingers in perform-
ing on the harpfichord, it would at firfi fight ap-
pear, that fwiftnefs and ftrength were incompati-
ble ; neverthelefs the fmgle contraction of a mufcle

b

7*> OF STIMULUS AND EXERTION. SECT. XII I.

is performed with greater velocity as well as with
greater force by vigorous confutations, as in throw-
ing a javelin.

There is however another circumftance, which
may often contribute to caufe the quicknefs of the
puiie in nervous fevers, as in animals bleeding to
death in the Daughter- houie ; which is the deficient
quantity of blood ; whence the heart is but half
diftended, and in confequence fooner contracts. See
Seel. XXXIL 2- i.

For we muft not confound frequency of repeti-
tion with quicknefs of motion, or the number of
pulfations with the velocity, with which the fibres,
which conftitute the coats of the arteries, contract
themfelves. For where the frequency of the pul-
fations is but feventy-five in a minute, as in health ;
the contracting fibres, which conftitute the fides of
the arteries, may move through a greater fpace in a
given time, than where the frequency of pulfation
is one hundred and fifty in a minute, as in fome
fevers with great debility. For if in thofe fevers
the arteries do not expand themfelves in their
diaftole to more than half the ufual diameter of
their diaflole in health, the fibres whkh conftitute
their coats, will move through a lefs fpace in a mi-
nute than in health, though they make two pulfa-
tions for one.

Suppofe the diameter of the artery during its
fyftole to be one line, and that the diameter of the
fame artery during its diaftole is in health is four
lines, and in a fever with great debility only two
lines. It follows, that the arterial fibres contract in
health from a circle of twelve lines in circumfe-
rence to a circle of three lines in c'^u inference,
that is they move through a fpace of nine lines in
length. While the arterial fibres in the fever with
debility would twice contract from a circle of fix
lines to a circle of three lines j that is while they

move

SECT. XII. r. OF STIMULUS AND EXERTION. 71

move through a fpace equal to fix lines. Hence
though the frequency of pulfation in fever be
greater as two to one, yet the velocity of contrac-
tion in health is greater as nine to fix, or as three
to two.

On the contrary in inflammatory difeafes with
ftrength, as in the pleuriiy, the velocity of the
contracting fides of the arteries is much greater
than in health, for if we fuppofe the number of
pulfations in a pleurify to be half as much more
than in health, that is as one hundred and twenty
to eighty, (which is about what generally happens
in inflammatory difeafes) and if the diameter of the
artery in diaftole be one third greater than in
health, which I believe is near the truth, the re*
fult will be, that the velocity of the contractile fides
of the arteries will be in a pleurify as two and a half
to one, compared to the velocity of their contrac-
tion in a ftate of health, for if the circumference
of the fyftole of the artery be three lines, and the
diaftole in health be twelve lines in circumference,
and in a pleurify eighteen lines ; and fecondly, if
the artery pulfates thrice in the difeafed ftate for
twice in the healthy onc« it follows, that the velo-
city of contraction in the difeafed ftate to that in
the healthy ftate will be forty-five to eighteen, or as
two and a half to one.

From hence it would appear, that if we had a
criterion to determine the velocity of the arterial
contractions, it would at the fame time give us their
ftrength, and thus be of more fervice in diftinguifh-
ing difeafes, than the knowledge of their fre-
quency. As fuch a criterion cannot be had, the
frequency of puifauon, the age of the patient being
allowed for, will in ibme meafure affift us to diftin-
guifli arterial ftrength from arterial debility, fince
in inflammatory difeafes with ftrength the frequency
feldotn exceeds one hundred and eighteen or one

hundred

72 OF STIMULUS AND EXERTION. SECT.*!/. i<*

hundred and twenty pulfations in a minute ; unlefs
under peculiar cir cum fiance, as the great additional
ftimuli of wine or of external heat.

5. After a mufcle or organ of fenfe has been ex-
cited into contraction, and the fenforial power ceafes
to act, the laft fituation or configuration of it con-
tinues ; unlefs it be diftributed by the action of
fome antagonift fibres, or other extraneous power*
Thus in weak or languid people, wherever they
throw their limbs on their bed or fofa, there they
lie, till another exertion changes their attitude ;
hence one kind of ocular fpectra feems to be pro-
duced after looking at bright objects ; thus when a
fire-flick is whirled round in the night, there ap-
pears in the eye a complete circle of fire 5 the ac-
tion or configuration of one part of the retina not
ceafing before the return of the whirling fire.

Thus if any one looks at the fetting fun for a
fiiort time, and then covers his clofed eyes with his
hand, he will for many feconds of time perceive
the image of the fun on his retina. A fimilar image
of all other bodies would remain fome time in the
eye, but is effaced by the eternal change of the
motions of the extremity <,f this nerve in our at-
tention to other objects. See Sect. XVII. i. 3. on
Sleep. Hence the dark fpots, and other ocular
fpectra, are more frequently attended to, and re-
main longer in the eyes of weak people, as after
violent exercife, intoxication, or want of fleep.

6. A contraction of the fibres fomewhat greater
than ufual introduces pleafurable feniation into the
fyftern, according to the fourth law of animal cau-
fation. Hence the pleafure in the beginning of
drunkenneis is owing, to the incrcafed action of the
fyftem from the flimulus of vinous fpirit or of
opium. If the contractions be ftill greater in ener-
gy or duration, painful fenfations are introduced,

as

SECT. XII. r. OF STIMULUS AND EXERTION. 7$

as in confequence of great heat, or cauftic applica-
tions, or fatigue.

If any part of the fyftem, which is ufed to per-
petuai activity, as the ftomach, or heart, or the
fine veffels of the (kin, acts for a time with lefs
energy, another kind of painful fenfation enfues,
which is called hunger, or faintnefs, or cold. This
occurs in a lefs degree in the locomotive mufcles,
and is called wearyfomenefs. In the two former
kinds of fenfation there is an expenditure of fen-
forial power, in thefe latter there is an accumulati-
on of it.

7. We have ufed the words exertion of fenforial
power as a general term to exprefs either irritation,
fenfation, volition, or aflbciation ; that is, to ex-
prefs the activity or motion of the fpirit of anima-
tion, at the time it produces the contractions of
the fibrous parts of the fyftem. It may be fuppofed
that there may exift a greater or lefs mobility of
the fibrous parts of our fyftem, or a propenfity to
be ftimulated into contraction by the greater or
lefs quantity or energy of the fpirit of animation ;
and that hence if the exertion of the fenforial
power be in its natural ftate, and the mobility of
the fibres be increafed, the fame quantity of fibrous
contra&ion will be caufed, as if the mobility of the
fibres continues in its natural ftate, and the fenfo-
rial exertion be increafed.

Thus it may be conceived, that in difeafes ac-
companied with ftrength, as in inflammatory fevers
with arterial ftrength, that the eaufe of greater
fibrous contraction may exift in the increafed mo-
bility of the fibres, whofe contractions are thence
both more forceable and more frequent. And that
in difeafes attended with debility, as in nervous
fevers, where the fibrous contractions are weaker,
and more frequent, it may be conceived that the
caufe confiftsin a decreafc of mobility of the fibres ;

and

74 OF STIMULUS AND EXERTION. SECT. XII. i.

and that thofe weak conftitutions, which are at.
tended with cold extremities and large pupils of the
eyes, may poiTefs lefs mobility of the contractile
fibres, as well as lefs quantity of exertion of the
fpirit of animation.

In anfwer to this mode of reafoning it may be
fufficient to obferve, that the contractile fibres con-
fift of inert matter, and when the fenforial power
is withdrawn, as in death, they poffefs no power of
motion at all, but remain in their laft ftate, whe-
ther of contraction or relaxation, and muft thence
derive the whole of this property from the fpirit of
animation. At the fame time it is not improbable,
that the moving fibres of ttrong people may pof-
fefs a capability of receiving or containing a greater
quantity of the fpirit of animation than thofe of
weak people.

In every contraction of a fibre there is an expen-
diture of the icnforial power, or fpirit of animati-
on ; and where the exertion of this fenforial power
Has been for fome time increafed, and the mufcles
or organs of fenfe have in confequence acted with
greater energy, its propenfity to activity is propor-
tionally lefiened ; which is to be afcribed to the ex-
hauftion or diminution of its quantity. On the
contrary, where there has been lefs fibrous contrac-
tion than ufual for a certain time, the fenforial
power or animation becomes accumulated in the in-
active part of the fyftem. Hence vigour fucceeds
reft, and hence the propenfity to action of all our
organs of (enfe and mufcles is in a ftate of perpe-
tual fluctuation. The irritability for inftance of
the retina, that is, its quantity of fenforial power,
varies every moment according to the brightnefs or
obfcurity of the object laft beheld compared with
the prefent one. The fame occurs to our fenfe of
heat, and to every part of our fyftem, which is
capable of being excited into action.

When

SECT. XII. 2. OF STIMULUS AND EXERTION. 75

When this variation of the exertion of the fen-
forial power becomes much and permanently above
or beneath the natural quantity, it becomes a
cifeafe. If the irritative motions be too great or too
little, it fhews that the flimulus of external things
affects this fenforial power too violently or too in-
ertly. If the fenfitive motions be too great or too
little, the caufe arifes from the deficient or exube-
rant quantity of fenfation produced in confequence
of the motions of the mufcuhr fibres or organs of
fenfe; if the voluntary aclions are difeafed, the
caufe is to be looked for in the quantity of volition
produced in confequence of the defire or aversion
occaiioned by the painful or pleafurable fenfations
above mentioned. And the difeafes of afTociations
probably depend on the greater or lefs quantity of
the other three fenforial powers by which they
were formed.

From whence it appears that the propenfity to
action, whether it be called irritability, fenfibility,
voluntarity, or aflbciability, is only another mode
of expreffion for the quantity of fenforial power re-
fiding in the organ to be excited. And that on the
contrary the words inirritability and inienfibility,
together with inaptitude to voluntary and aflbciate
motions, are fynonymous with deficiency of the
quantity of fenforial power, or of the fpirit of
animation, refiding in the organs to be excited.

II. Of fenforial Exertion.

i. There are three circumflances to be attended
to in the production of animal motions, ift. The
ftimulus. 2d. The fenforial power. 3d. The con-
tractile fibre, i ft. A ftimulus, external to the or-
gan, originally induces into action the fenforial fa-
culty termed irritation ; this produces the contrac-
tion of the fibres, which if it be perceived at all,

G introduces

76 OF STIMULUS AND EXERTION. SECT. XII. 2-

introduces pleafure or pain ; which in their active
flate are termed fenfation ; which is another feiifo-
rial faculty, and occafionally produces contraction
of the fibres ; this pleafure or pain is therefore to
be confidered as another ftimulus, which may either
act alone or in conjunction with the former faculty
of the fenforium termed irritation. This new fti-x
mulus of pleafure or pain either induces into action
the fenforial faculty termed fenfation, which then
produces the contraction of the fibres ; or it intro-
duces defire or averiion, which excite into action
another fenforial faculty, termed volition, and
may therefore be confidered as another ftimulus,
which either alone, or in conjunction with one or
both of the two former faculties of the fenforium,
produces the contraction of animal fibres. There
is another fenforial power, that of affociation,
which perpetually, in conjunction with one or more
of the above, and frequently fingly, produces the
contraction of animal fibres, and which is itfelf
excited into action by the previous motions of con-
tracting fibres.

Now as the fenforial power, termed irritation,
refiding in any particular fibres, is excited into ex-
ertion by the ilimulus of external bodies acting on
thofe fibres; the fenforial power, termed fenfation,
refiding in any particular fibres is excited into exer-
tion by the (limulus of pleafure or pain acting on
thofe fibres; the fenforial power, termed volition,
refiding in any particular fibres is excited into ex-
ertion by the ftimulus of deiire or averfion ; and
the fenforial power termed affociation, refiding in
any particular fibres, is excited into action by the
iUmuius of other fibrous motions, which had fre-
quently preceded them. The word ilimulus may
therefore be ufed without impropriety of language,
for any of thefe four caufes, which excite the four

fenforial

SECT. XII. 2. OF STIMULUS AND EXERTION. 77

fenforial powers into exertion. For though the
immediate caufe of volition has generally been
termed a motive ; and that of irritation only has
generally obtained the name of ftimulus ; yet as the
immediate caufe, which excites the fenforial powers
of fenfation, or of aflbciation into exertion, have
obtained no general name, we iliall ufc the word
ftimulus for them all.

Hence the quantity of motion produced in any
particular part of the animal fyftem will be as the
quantity of ftimulus and the quantity of fenforial
power, or fpirit of animation, redding in the con-
tracting fibres. Where both thefe quantities are
great ftrength is produced, when that word is ap-
plied to the motions of animal bodies. Where
either of them is deficient, iveaknefs is produced, as
applied to the motions of animal bodies.

Now as the fenforial power, or fpirit of animati-
on, is perpetually exhaufted by the expenditure of
it in fibrous contractions, and is perpetually re-
newed by the fecretion or production of it in the
brain and fpinal marrow, the quantity of animal
ftrength muft be in a perpetual (late of fluctuation
on this account ; and if to this be added the un-
ceafmg variation of all the four kinds of ftimulus
above dcfcribed, which produce the exertions of
the fenforiai powers, the ceafelefs viciffitude of
animal ftrength becomes eafiiy comprehended.

If the quantity of fenforial power remains the
fame, and the quantity of ftimulus be leiTened, a
weaknefs of the fibrous contractions enfues, which
may be denominated debility from defeft of ftimulus.
If the quantity of ftimuius remains the lame, and
the quantity of fenforial power be leflened, another
kind of weaknefs enfues, which may be termed
debility frojn defefl of fenforial power ; the former of

G 2 thefe

78 OF STIMULUS AND EXERTION. SECT. XII. 2.

thefe is called by Dr. Brown, in his Elements of
Medicine, direct debility, and the latter indirect de-
bility. The coincidence of fome parts of this work
with correfpondent deductions in the Brunonian
Elementa Medicinee, a work (with fome exceptions)
of great genius, muft be confidered as confirmati-
ons of the truth of the theory, as they were pro-
bably arrived at by different trains of reafoning.

Thus in thofe who have been expofed to cold
and hunger there is a deficiency of ftimulus. While
in nervous fever there is a deficiency of fenforial
power. And in habitual drunkards, in a morning
before their ufual potation, there is a deficiency
both of ftimulus and of fenforial power. While, on
the other hand, in the beginning of intoxication
there is an excefs of ftimulus ; in the hot-ach, after
the hands have been immerfed in mow, there is a
redundancy of fenforial power ; and in inflamma-
tory difeafes with arterial ftrength, there is an ex-
cefs of both.

Hence if the fenforial power be leffened, while
the quantity of ftimulus remains the fame as in
nervous fever, the frequency of repetition of the
arterial contractions may continue, but their force
in refpect to removing obftacles, as in promoting
the circulation of the blood, or the velocity of each
contraction, will be diminifhed, that is, the animal
ftrength will be leffened. And fecondly, if the
quantity of fenforial power be leffened, and the fti-
mulus be increafed to a certain degree, as in giving
opium in nervous fevers, the arterial contractions
may be performed more frequently than natural,
yet with lefs ftrength.

And thirdly, if the fenforial power continues the
fame in refpect to quantity, and the ftimulus be
fomewhat diminifhed, as in going into a darkifh
room, or into a coldifli bath, fuppofe of about
eighty degrees of heat, as Buxton-bath, a tempo-
rary

SICT. XII. 2. OF STIMULUS AND EXERTION. 79

rary weaknefs of the affefted fibres is induced, till
an accumulation of fenibrial power gradually fuc-
ceeds, and counterbalances the deficiency of ftimu-
lus, and then the bath ceafes to feel cold, and the
room ceafes to appear dark ; becaufe the fibres of
the fubcutaneous vefiels, or of the organs, of fenfe,
act with their ufual energy.

A fet of mufcular fibres may thus be ftimulated
into violent exertion, that is, they may act fre-
quently, and with their whole fenforial power, but
may ne vert helefs not aft ftrongly ; becaufe the quan-
tity of their fenforial power was originally fmall,
or was previoufly exhaufted. Hence a ftimulus
may be great, and the irritation in confequence act
with its full force, as in the hot paroxyfms of ner-
vous fever ; but >f the fenforial power, termed irri-
tation, be fmall in quantity, the force of the fibrous
contractions, and the times of their continuance in
their contracted ftate, will be proportionally fmall.
In the fame manner in the hot paroxyfm of-
putrid fevers, which are (hewn in Se<5t. XXXI-II. to
be inflammatory fevers with arterial debility, the
fenforial power termed fen fat ion is exerted with
great activity, yet the fibrous contractions, which
produce the circulation of the blood, are perform-
ed without ftrength, becaufe the quantity of fenfo-
rial power then refiding in that part of the fyftem is
fmall.

Thus in irritative fever with arterial ftrength,
that is, with excefs of fpirit of ani mation, the quan-
tity of exertion during the hot part of the paroxyfrn
is to be eftirnated from the quantity of ftimulus,
and the quantity of fenforial power. While in fen-
fitive (or inflammatory) fever with arterial ftrength,
that is, with excefs of fpirit of animation, the
violent and forcible actions of the vafcular fyftem
during the hot part of the paroxyfm are induced by
the exertions of two fenibrial powers, which are

excited

So OF STIMULUS AND EXERTION. SECT. XII. 2

excited by two kinds of fiimulus. Thefe are the
fenforial power of irritation excited by the ilimulus
of bodies external to the moving fibres, and the
fenforial power of fenfation excited by the pain in
confequence of the increafed contractions of thofe
moving fibres.

And in infane people in fome cafes the force of
their mufcular actions will be in proportion to the
quantity of fenforial power, which they poilefs, and
the quantity of the fiimulus of deiire or averfion,
which excites their volition into action. At the
fame time in other cafes the famulus of pain or
pleafure, and the fiimulus of external bodies, may
excite into action the fenforial powers of fenfation
and irritation, arid thus add greater force to their
mufcular actions.

2. The application of the ilimulus, whether that
fiimulus be fome quality of external bodies, or
pleafure or pain, or defire or averfion, or a link of
affociation, excites the correfpondent fenforial power
into action, and this cauies the contraction of the
fibre. On the contraction of the fibre a part of
the fpirit of animation becomes expended, and the
fibre ceafes to contract, though the ilimulus conti-
nues to be applied ; till in a certain time the fibre
having received a fupply of fenforial power is ready
to contract again, if the ilimulus continues to be
applied. If the ilimulus on the contrary be with-
drawn, the fame quantity of quiefcent fenforial
power becomes refident in the fibre as before its
contraction ; as appears from the readinefs for ac-
tion of the large locomotive mufcles of the body in
a (hort time after common exertion.

But in thofe mufcuiar fibres, which are fubject
to conilant itimulus, as the arteries, glands, and
capillary veflels, another phenomenon occurs, if
their accuftomed ilimulus be withdrawn ; which is,
that the fenforial power becomes accumulated in the

contractile

SECT. XII. 2. OF STIMULUS AND EXERTION. *i

contractile fibres, owing to the want of its being
perpetually expended, or carried away, by their
ufual unremitted contractions. And on this ac-
count thofe inufcular fibres become afterwards ex-
citable into their natural actions by a much weaker
ftimulus ; or into unnatural violence of action by
their accuftomed ftimulus, as is feen in the hot fits
of intermittent fevers, which are in confequence of
the previous cold ones. Thus the minute veifels of
the fkin are conftantly flimulated by the fluid mat-
ter of heat ; if the quantity of this iiimulus of
heat be a while diminished, as in covering the hands
with fnow, the vefleis ceafe to act, as appears from
the palenefs of the fkin ; if this cold application
of fnow be continued but a mort time, the fenfo-
rial power, which had habitually been fupplied to
the fibres, becomes now accumulated in them, ow-
ing to the want of its being expended by their ac-
cuftomed contractions. And thence a lei's ftimulus
of heat will now excite them into violent contrac-
tions.

If the quiefcence of fibres, which had previoufly
been fubjecl: to perpetual ftimulus, continues a lon-
ger time ; or their accuftomed ftimulus be more
completely withdrawn ; the accumulation of fen-
forial power becomes fiill greater* as in thofe ex-
pofed to cold and hunger ; pain is produced, and
the organ gradually dies from the chemical changes,
which take place in it ; or it is at a great diitance of
time reftored to action by ftimulus applied with
great caution in frnail quantity, as happens to fome
larger animals and to many infects, which during
the winter months lie benumbed with cold, and are
faid to fleep, and to perfons apparently drowned,
or apparently frozen to death. Snails have been faid
to revive by throwing them into water after having
been many years fhut up in the cabinets of the

curious 5

82 OF STIMULUS AND EXERTION. SECT. XII. 2,

curious; and eggs and feeds in general are reHored
to life after many months of torpor by the ftimu-
lus of warmth and moiiture.

The inflammation of fchirrous tumours, which
have long exifted in a (late of inaction, is a procefs
of this kind; as well as the fenfibility acquired by
inflamed tendons and bone.s, which had at their
formation a fimilar fenfibility, which had fo long
lain dormant in their uninflamed ftate.

3. If after long quiefccnce from defect of ftimu-
lus the fibres, which had previoufly been habitu-
ated to perpetual ftimulus, are again expofed to
but their ufual quantity of it ; as in thofe who have
fuffered the extremes of cold or hunger ; a violent
exertion of the affected organ commences, owing,
as above explained, to the great accumulation of
fenforial power. This violent exertion not only
diminiihes the accumulated fpirit of animation, but
at the fame time induces pleafure or pain into the
fyftem, which, whether it be fucceeded by inflam-
mation or not, becomes an additional ftimulus, and
acting along with the former one, produces ftill
greater exertions ; and thus reduces the fenforial
power in the contracting fibres beneath its natural
quantity.

When the fpirit of animation is thus exhaufted
by ufelefs exertions, the organ becomes torpid or
unexcitable into action, and a fecond fit of quief-
cence fucceeds that of abundant activity. During
this fecond fit of quiefcencc the fenforial power be-
comes again accumulated, and another fit of exer-
tion follows in train. Thefe vicitlitudes of exer-
tion and inertion of the arterial fyftem conftitute
the paroxyfms of remittent fevers ; or intermittent
ones, when there is an interval of the natural ac-
tion of the arteries between the exacerbations.

In thefe paroxyfms of fevers, which confift of
the libration of the arterial fyftem between the ex-
tremes

. XII. 3. OF STIMULUS AND EXERTION. 83

tremes of exertion and quiefcence, either the fits
become lefs and lefs violent from the contractile
fibres becoming lefs excitable to the ftimulus by ha-
bit, that is, by becoming accuftomed to it, as ex-
plained below XII. 3. i. or the whole fenforial
power becomes exhaufted, and the arteries ceafe to
beat, and the patient dies in the cold part of the
paroxyfm. Or fecondly, fo much pain is intro-
duced into the fyftem by the violent contractions
of the fibres, that inflammation arifes, which pre-
vents future cold fits by expending a part of the
fenforial power in the exteniion of old vefiels or the
production of new ones; and thus preventing the
too great accumulation or exertion of it in other
parts of the fyftem ; or which by the great increafe
of ftimulus excites into great action the whole glan-
dular fyilem as well as the arterial, and thence a
greater quantity of fenforial power is produced in
the brain, and thus its exhauftion in any peculiar
part of the fyftem ceafes to be affected.

4. Or thirdly, in confequence of the painful or
pleafurable fenfation above mentioned, defire and
averfion are introduced, and inordinate volition
fucceeds ; which by its own exertions expends fo
much of the fpirit of animation, that the two other
fenforial faculties, or irritation and fen far ion, act
fo much more feebly ; that the paroxyfms of fever,
or that libration between the extremes of exert -'on
and inactivity of the arterial fyitem, gradually fub-
fides. On this account a temporary infanity is a
favourable fign in fevers, as I have had fbme op.
portunities of obferving.

III. Of repeated Stimulus.

i. When a ftimulus is repeated more frequently
than the expenditure of fenforial power can be re-
newed in the acting organ, the effect of ihe ftimu-
lus

«4 OF STIMULUS AND EXERTION. SECT. XII. 3.

lus becomes gradually diminimed. Thus if two
grains of opium be fwallowed by a perfon unufed
to ib ftrong a ftimulus, all the vafcular fyftems in
the body act with greater energy, ali the fecretions
and the abforption from thofe fecreted fluids are
increafed in quantity ; and pleafure or plain are in-
troduced into the fyftem, which adds an additional
ftimulus to that already to6 great. After fome
Jiours the fenforial power becomes diminifhed in
quantity, expended by the great activity of, the
iyftern ; and thence, when the ftimulus of the
opium is withdrawn, the fibres will not obey their
ufual degree of natural (limulus, and a confequent
torpor or quiefcence fucceeds, as is experienced by
drunkards, who on the day after a great excefs of
fpirituous potation feel indigeftion, head-ach, and
general debility.

In this fit of torpor or quiefcence of a part or of the
whole of the fyftem, an accumulation of the fen-
forial power in the affected fibres is formed, and
occaiions a fecond paroxyfm of exertion by the ap-
plication only of the natural ftimulus, and thus a
libration of the fenforial exertion between one ex-
cefs and the other continues for two or three days,
where the ftimulus was violent in degree ; and for
weeks in fome fevers, from the ftimulus of conta-
gious matter. ^'<

But if a fecond dofe of opium be exhibited be-
fore the fibres have regained their natural quantity
of fenforial power, its effect will be much lefs than
the former, becaufe the fpirit of animation or fen-
forial power is in part exhaufted by the previous
excefs of exertion. Hence all medicines repeated
too frequently gradually lofe their effect, as opium
and wine. Many things of difagreeable tafte at
firft ceafe to be difagreeable by frequent repetition,
as- tobacco ; grief and pain gradually diminifh, and

at

SECT. XII. 3. OF STIMULUS AND EXERTION. 85

at length ceafe altogether, and hence life itfelf be-
comes tolerable.

Be (ides the temporary diminution of the fpirit of
animation or fen ferial power, which is naturally
ftationary or refident in every living f-bre, by a
ilngle exhibition of a powerful ftimulus, the contrac-
tile fibres themfeives, by the perpetual application
of a new quantity of ftimulus, before they have re-
gained their natural quantity of fenforial power,
appear to fuffer in their capability of receiving fo
much as the natural quantity of (enibrial power ;
and hence a permanent deficiency of fpirit of ani-
mation take* place, however long the ftimulus
may have been withdrawn. On this caufe depends
the permanent debility of thofe, who have been
addicled to intoxication, the general weaknefs of
old age, and the natural debility or inirritability
of thofe, who have pale {kins and large pupils of
their eyes.

There is a curious phenomenon belongs to this
place, which has always appeared difficult of folu-
tion j and that is, that opium or aloes may be ex*
hibited in fmall dofes at firft, and gradually in-
creafed to very large ones without producing ftu-
por or diarrhoea. In this cafe, though the opium
and aloes are given in fuch fmall doles as not to
produce intoxicatioij or cathariis, yet they are ex*
hibited in quantities fuilicient in fame degree to
exhauft the fenforial power, and hence a ftronger
and a ilronger dofe is required ; otherwife- the me-
dicine would foon ceafe to act at all.

On the contrary, if the opium or aloes be exhi-
bited in a large dofe at firft, fo as to produce in-
toxication or diarrhoea; after a few repetitions the
quantity of either of them may be diminifhed, and
they will ftill produce this effect, For the more
powerful ftimulus dhTevers the progreffive catena-
tions of animal motions, defcribed in Sect XVjj.

and

86 OF STIMULUS AND EXERTION. SECT.' X II. 3.

and introduces a new link between them ; whence
every repetition ftrengthens this new affociation or
catenation, and the ilimulus may be gradually de-
creafed, or be nearly withdrawn, and yet the ef-
fect mail c ntinue ; becaufe the ienforial power of
aifociation or catenation being united with the fti-
inulus, increafes in energy with every repetition
of the catenated circle ; and it is by thefe means
that all the irritative affociations of motions are
originally produced.

2. When a ftimulus is repeated at fuch diftant
intervals of time, that the natural quantity of fen-
ibrial power becomes completely reftored in the
acting fibres, it will acl with the fame energy as
when firft applied. Hence thofe who have lately
accuftomed ihemfelves to large dofes of opium by
beginning with fmall ones, and gradually increaf-
ingthem, and repeating them frequently, as men-
tioned in the preceding paragraph ; if they inter-
mit the ufe of it for a few days only, mult begin
again with as fmall dofes as they took at firft, other-
wife they will experience the inconveniences of in-
toxication.

On this circumftance depend the conftant un-
failing effects of the various kinds of flimulus,
which excite into aclion all the vafcular fyilems in
the body ; the arterial, venous, abforbent, and
glandular veflcls, are brought into perpetual un-
wearied aftion by the fluids, which are adapted to
IHmuIate them ; but thefe have the fenforial power
of affociation added to that of irritation, and even
in foine degree that of fenfation, and even of voli-
tion, as will be fpoken of in their places ; and life
itfelf is thus carried on by the production of fenfo-
rial power being equal to its wafte or expenditure
in the perpetual movement of the vafcular organi-
zation.

7. When

SECT. XII. 3. OF STIMULUS AND EXERTION. 87

3. When a ftimulus is repeated at uniform in-
tervals of time with fuch diftances between them,
that the expenditure of fenforial power in the act-
ing fibres becomes completely renewed, the effect is
produced with greater facility or energy. For the
fenforial power of allbciation is combined with the
fenforial power of irritation, or, in common lan-
guage, the acquired habit aflifts the power of the
ilimulus.

This circumftance not only obtains in the annual
and diurnal catenations of animal motions explain-
ed in Sect. XXXVI. but in every lefs circle of ac-
tions or ideas, as in the burthen of a fong, or the
iterations of a dance ; and conftitutes the pleafure
we receive from repetition and imitation ; as treat-
ed of in Sett. XXII. 2.

4. When a ftimulus has been many times repeat-
ed at uniform intervals, fo as to produce the com-
plete action of the organ, it may then be gradual-
ly diminifhed, or totally withdrawn, and the ac-
tion of the organ will continue. For the fenforial
power of affociation becomes united with that of
irritation, and by frequent repetition becomes at
length of fufficient energy to carry on the new link
in the circle of actions, without the irritation which
at firft introduced it.

Hence, when the bark is given at dated inter-
vals for the cure of intermittent fevers, if fixty
grains of it be given every three hours for the
twenty-four hours preceding the expected pa-
roxyfm, fo as to ftimulate the defective part of the
fyftem into action, and by that means to prevent
the torpor or quiefcence of the fibres, which con-
ititutes the cold fit ; much lefs than half the quan-
tity, given before the time at which another pa-
roxyfm of quiefcence would have taken place, will
be fufficient to prevent it ; becaufe now the fenfo-
rial power, termed affociation, acts in a twofold

manner,

88 OF STIMULUS AND EXERTION. SECT. XII. 3-

manner. Firfl, in refpect to the period of the ca-
tenation in which the cold fit was produced, which
is now diflevered by the ftronger ftimulus of the
firft dofes of the bark ; and, fecondly, becaufe each
dofe of* bark being repeated at periodical times, has
its effect increafed by the fenibrial faculty of affo-
ciation being combined with that of irritation.

Now, when fixty grains of Peruvian bark are
taken twice a day, fuppofe at ten. o'clock and at
fix, for a fortnight, the irritation excited by this
additional ttimulus becomes a part of the diurnal
circle -of actions, and will at length carry on the
increafed action of the fyftem without the afliftance
of the flimulus of the bark. On this theory the
bitter medicines, chalybeates, and opiates in ap-
propriated dofes, exhibited for a fortnight, give
permanent ftrength to pale feeble children, and
other weak conftitutions.

5. When a defect of ftimulus, as of heat, recurs
at certain diurnal intervals, which induces fome
torpor or quiefcence of a part of the fyftem, the
diurnal catenation of actions becomes difordered,
and a new aflbciation with this link of torpid ac-
tion is formed \ on the next period the quantity
of quiefcence will be increafed, fuppofe the fame
defect of ftimulus to recur, becaufe now the new
aflbciation confpires with the defective irritation
in introducing the torpid action of this part of the
diurnal catenation. In this manner many fever-
fits commence, where the patient is for fome days
indifpoied at certain hours, before the cold pa-
roxyfm of fever is completely formed. See Sect.
XVII. 3. 3. on Catenation of Animal Motions.

6. If a ftimulus, which at firft excited the affect-
ed organ into fo great exertion as to produce fen-
fation, be continued for a certain time, it will ceafe
to produce fenfation both then and when repeated,

though

SECT. XII. 3. OF STIMULUS AND EXEP TION. S9

though the irritative motions in confcquence of
it may continue or be re-excited.

Many catenations of irritative motions were at
firil fucceeded by fenfation, as the apparent motions
of objects when we walk pad them, and probably
the vital motions themfelves in the early ftate of
our exiftence. But as thofe fenfations were fol-
lowed by no movements of the fyftem in confe-
quence of them, they gradually ceafed to be pro-
duced, not being joined to any fucceeding link of
catenation. Hence contagious matter, which has
for fome weeks ilimulated the fyftem into great and
permanent fenfation, ceafes afterwards to produce
general fenfation or inflammation, though it may
ilill induce topical irritations. See Sect. XXXIII. 2.
8. XIX. 10.

Our abforbent fyitem then feems to receive thofe
contagious matters, which it has before experi-
enced, in the fame manner as it imbibes commoa
moifture or other fluids ; that is, without being
thrown into fo violent action as to produce fenfa-
tion ; the confequence of which is an increafe of
daily energy or activity, till inflammation and its
confequences fucceed.

7. If a ftimulus excites an organ into fuch vio-
lent contractions as to produce fenfation, the mo-
tions of which organ had not ufually produced fen-
fation, this new fenforial power, added to the ir-
ritation occafioned by the ftimulus, increafes the
activity of the organ. And if this activity be ca-
tenated with the diurnal circle of actions, an in-
creafing inflammation is produced ; as in the even-
ing paroxyfms of fmall-pox, and other fevers with
inflammation. And hence fchirrous tumours, ten-
dons and membranes, and probably the arteries
themfelves become inflamed, when they are itrong,
ly Simulated.

IV. Of

90 OF STIMULUS AND EXERTION. SECT. XII. 4.

IV. Of Stimulus greater than natural.

i. A quantity of ftimulus greater than natural,
producing an increafed exertion of fenforial power,
whether that exertion be in the mode of irritation,
fenfation, volition, or affociation, diminiflies the
general quantity of it. This fact is obfervable in
the progrefs of intoxication, as the increafed quan-
tity or energy of the irritative motions, owing to
the ftimulus of vinous fpirit, introduces much plea-
furable fenfation into the fyftem, and much exertion
of mufcular or fenfual motions in confequence of this
increafed fenfation ; the voluntary motions, and
even the aflbciate ones, become much impaired or
diminimed ; and delirium and Daggering fucceed.
See Seel. XXI. on Drunkennefs. And hence the
great proftration of the ftrength of the locomotive
mufcles in fome fevers, is owing to the exhauftion
of fenforial power by the increafed aftion of the
arterial fyftem.

In like manner a ftimulus greater than natural,
applied to a part of the fyftem, increafes the exer-
tion of fenforial power in that part, and diminifhes
it in fome other part. As in the commencement
of fcarlet fever, it is ufual to fee great rednefs and
heat on the faces and breafts of children, while at
the fame time their feet are colder than natural ;
partial heats are obfervable in other fevers with de-
bility, and are generally attended with torpor or
quiefcence of fome other part of the fyftem. But
thefe partial exertions of fenforial power are fome-
times attended with increafed partial exertions in
other parts of the fyftem, which fympathzie with
them, as the flufhing of the face after a full meal.
Both thefe therefore are to be afcribed to fympa-
thetic aflbciations, explained in Seel, XXXV. and

not

SECT. XII. 4. OF STIMULUS AND EXERTION. 9?

not to general exauftion or accumulation of fenfo-
rial power.

2 A quantity of (limul us greater than natural,
producing an increafed exertion of fenforial power
in any particular organ, diminifhes the quantity
of it in that organ. This appears from the con-
tractions of animal fibres being not fo eafily excit-
ed by a lefs itimulus after the organ has been fub-
jecled to a greater. Thus after looking at any
luminous object of a fmall fize, as at the fetting fun,
for a fhort time, fo as not much to fatigue the eye,
this part of the retina becomes lefs fenfible to fmal-
ler quantities of light ; hence when the eyes are
turned on other lefs luminous parts of the Iky, a
dark fpot is feen refembling the fhape of the fun,
or other luminous object which we laft behold.
See Seel. XL. No. 2.

Thus we are fome time before we can diftinguifh
objects in an obfcure room after coming from
bright day-light, though the iris prefently contracts
itfelf. We are not able to hear weak founds after
loud ones. And the ftomachs of thofe who have
been much habituated to the ftronger flimulus of
fermented or fpirituous liquors, are not excited
into due action by weaker ones,

3. A quantity of iiimulus fomething greater than
the laft mentioned, or longer continued, induces
the organ into fpafmodic action, which ceafes and
recurs alternately. Thus on looking for a time
on the fetting fun, fo as not greatly to fatigue the
fight, a yellow fpectrum is feen when the eyes are
clofed and covered, which continues for a time,
and then difappears and recurs repeatedly before
it entirely vaniihes. See Sect. XL. No. 5. Thus
the action of vomiting ceafes and is renewed by
intervals, although the emetic drug is thrown up
with the firft effort. A tenefmus continues by
intervals fome time after the exclufion of acrid

H excrement ;

9* OF STIMULUS AND EXERTION. SECT. XII.

excrement ; and the pulfations of the heart of a
viper are faid to continue fome time after it is
cleared from its blood.

In thefe cafes the violent contractions of the fibres
produce pain according to law 4 ; and this pain
conftitutes an additional kind or quantity of ex-
citement, which again induces the fibres into con-
traction, and which painful excitement is again
renewed, and again induces contractions of the
fibres with gradually diminifhing effect.

4. A quantity of flimulus greater than the laft
mentioned, or longer continued, induces the an-
tagonift mufcles into fpafmodic action. This is
beautifully iiluftrated by the ocular fpectra de-
fcribed in Sect. XL. No. 6. to which the reader
is referred. From thofe experiments there is rea-
fon to conclude that the fatigued part of the re-
tina throws itfelf into a contrary mode of action
like ofcitation or pandiculation, as foon as the fti-
mulus, which has fatigued it, is withdrawn ; but
that it ftill remains liable to be excited into action
by any other colours except the colour with which
it has been fatigued. Thus the yawning and ftretch-
ing the limbs after a continued action or attitude
feems occalioned by the antagonift mufcles being
ftimulated by their extenfion during the contrac-
tions of thofe in action, or in the fituation in
which that action laft left them.

5. A quantity of ftimulus greater than the laft,
or longer continued, induces variety of convulfions
or fixed fpafms either of the affected organ or of
the moving fibres in the other parts of the body.
In refpect to the fpectra in the eye, this is well ii-
luftrated in No. 7. and 3, of Sect XL. Epileptic
convulfions, as theemprofthotonos and opifthotonos,
with the cramp of the calf of the leg, locked jaw,
and other cataleptic fits, appear to originate from
pain, as fome of thefe patients fcream aloud be-
fore

SECT. XII. 4. OF STIMULUS AND EXERTION. 93

fore the convulfion takes place; which feems at
firft to be an effort to relieve painful fenfation, and
afterwards an effort to prevent it.

In thefe cafes the violent contractions of the
fibres produce fo much pain, as to conftitute a per-
petual excitement ; and that in fo great a degree
as to allow but fmall intervals* of relaxation of the
contracting fibres as in convulfions, or no inter-
vals at all as in fixed fpafms.

6. A quantity of (limulus greater than the laft,
or longer continued, produces a paralyfis of the
organ. In many cafes this paralyfis is only a tem-
porary effect, as on looking long on a fmall area
of bright red (ilk placed on a meet of white paper
on the floor in a (Iron g light, the red filk gradually
becomes paler, and at length difappears ; which
evinces that a part of the retina, by being violently
excited, becomes for a time unaffected by the'fti-
mulus of that colour. Thus cathartic medicines,
opiates, poifons, contagious matter, ceafe to in-
fluence our fyftem after it has been habituated to
the ufe of them, except by the exhibition of in-
creafed quantities of them ; our fibres not only be-
come unaffected by ftimuli, by which they have
previoufly been violently irritated, as by the mat-
ter of the fm all-pox or mealies ; but they alfo be-
come unaffected by fenfation, where the violent
exertions, which difobled them, were in confe-
quence of too great quantity of fenfation. And
laftly, the fibres, which become difobedient to vo-
lition, are probably difabled by their too violent
exertions in confequence of too great a quantity
of volition.

After every exertion of our fibres a temporary
paralyfis fucceeds, whence the intervals of all muf-
cular contractions, as mentioned in No. 3 and 4 of
this Section ; the immediate caufe of thefe more
permanent kinds of paralyfis is probably owing in

H 2 the

94 OF STIMULUS AND EXERTION. SECT. XII 5.

the fame manner to the too great exhauftion of
the fpirit of animation in the affected part ; fo that
a ftronger ftimulus is required, or one of a different
kind from that, which occafioned thofe too violent
contractions, to again excite the affected organ
into activity ; and if a ftronger ftimulus could be
applied, it muft again induce paralyfis.

For theie powerful ftimuli excite pain at the fame
time, that they produce irritation ; and this pain
not only excites fibrous motions by its ftimulus,
but it alfo produces volition ; and thus all thefe
ftimuli acting at the fame time, and fometimes with
the addition of their aflbciations, produce fo great
exertion as to expend the whole of tire fenforial
power in the affected fibres.

V. Of Stimulus lefs than natural.

i. A quantity of ftimulus lefs than natural, pro-
ducing a decreafed exertion of fenforial power, oc-
cafions an accumulation of the general quantity of
it. This circumftance is obfervable in the hemi-
plagia, in which the patients are perpetually moving
the mufcles, which are unaffected. On this ac-
count we awake with greater vigour after fleep,
becaufe during fo many hours, the great ufual ex-
penditure of fenforial power in the performance of
voluntary actions, and in the exertions of our or-
gans of fenfe, in confequence of the irritations oc-
cafioned by external objects, had been fufpended,
and a confequent accumulation had taken place.

In like manner the exertion of the fenforial
power lefs than natural in one part of the fyftem,
isliabls to produce an increafe of the exertion of it
in fome other part. Thus by the action of vomit-
ing, in which the natural exertions of the motions
of the ftomach are deiiroyed or dirmniihed, an in-

creafed

SECT. XII. 5. OF STIMULUS AND EXERTION. 95-

creafed abforption of the pulmonary and cellular
lymphatics is produced, as is known by the in-
creafed abforption of the fluid depofired in them
in dropfical cafes. But thefe partial quiefcences of
fenibrial power are alfo fometimes attended with
other partial quiefcences, which fympathife with
them, as cold and pale extremities from hunger.
Thefe therefore are to be afcribed to the affociations
of fympathy explained in Sect, XXXV. and not to
the general accumulation of fenforiai power.

2. A quantity of Rimulus lefs than natural, ap-
plied to fibres previoufly accuftomed to perpetual
ftimuius, is iucceeded by accumulation of fenforiai
power in the affected organ. The truth of this
proportion is evinced., becaufe a ftimuius lefs than
natural, if it be fomewhat greater than that above
mentioned, will excite the organ fo circumftanced
into violent activity. Thus on a frofty day with
wind, t^e face of a perfon expofed to the wind is
at firft pale and fhrunk ; but on turning the face
from the wind, it becomes foon of a glow with
waimth and flufliing. The glow of the fkin in
emerging from the cold-bath is owing to the fame
caufe.

It does not appear, that an accumulation of fen-
foriai power above the natural quantity is acquired
by thofe mufcles, which are not fubject to perpe-
tual ftimuius, as the locomotive mufcles : thefe,
after the greateft fatigue, only acquire by reft their
ufual aptitude to motion ; whereas the vafcular
fyftem, as the heart and arteries, after a fliort qui-
efcence, are thrown into violent action by their na-
tural quantity of flimulus.

Neverthelefs by this accumulation of fenforiai
power during the application of decreafed ftimuius,
and by the exhauftion of it during the action of in-
creafed ftimuius, it is wifely provided, that the ac-
tions of the vafcular mufcles and organs of fenfe

are

96 OF STIMULUS AND EXERTION. SECT. XII. 5.

are not much deranged by fmall variations of fti-
mulus ; as the quantity of fenforial power becomes
in fome meafure inversely as the quantity of fti-
mulus.

3. A quantity of ftimulus lefs than that men-
tioned above, and, continued for fome time, in-
duces pain in the affected organ, as the pain of
cold in the hands, when they are immerfed in fnow,
is owing to a deficiency of the ftimulation of heat.
Hunger is a pain from the deficiency of the ftimula-
tion of food. Pain in the back at the commence-
ment of ague-fits, and the head-achs which attend
feeble people, are pains from defect of ftimulus,
and are hence relieved by opium, eflential oils,
fpirit of wine.

As the pains, which originate from defect of
ftimulus, only occur in thofe parts of the fyftem,
which have been previoufly fubjected to perpetual
ftimulus ; and as an accumulation of fenforial power
is produced in the quiefcent organ along with the
pain, as in cold or hunger, there is reafon to
believe, that the pain is owing to the accumula-
tion of fenforial power, For, in the locomotive
mufcles, in the retina of the eye, and other organs
of fenfes, no pain occurs from the abfence of fti-
mulus, nor any great accumulation of fenforial
power beyond their natural quantity, fince thefe
organs have not been ufed to a perpetual fupply of
it. There is indeed a greater accumulation occurs
in the organ of vifion after its quiefcence, becaufe
it is fubject to more conftant ftimulus.

4. A certain quantity of ftimulus lefs than natu-
ral induces the moving organ into feebler and
more frequent contractions, as mentioned in No. I.
4. of this Section. For each contraction moving
through a lefs fpace, or with lefs force, that is,
with lefs expenditure of the fpirit of animation,
is fooner relaxed, and the fpirit of animation

derived

SECT. XII. 5. OF STIMULUS AND EXERTION. 97

derived at each interval into the acting fibres
being lefs, thefe intervals likewife become fhorter.
Hence the tremours of the hands of people accuf-
tomed to vinous fpirit, till they take their ufual
flimulus ; hence the quick pulfe in fevers attended
with ftrength ; in the latter the pulfe feldom beats
above 120 times in a minute, in the former it
frequently exceeds 140.

It muft be obferved, that in this and the two
following articles the decreafed action of the fyf-
tem is probably more frequently occafioned by
deficiency in the quantity of fenforial power, than
in the quantity of ftimulus. Thus thofe feeble
conftitutions which have large pupils of their eyes,
and all who labour under nervous fevers, feem
to owe their want of natural quantity of activity
in the fyftem to the deficiency of fenforial power ;
iince, as far as can be feen, they frequently poflefs
the natural quantity of flimulus.

5. A certain quantity of ft imulus, lefs than that
above mentioned, inverts the order of fucceffive
fibrous contractions ; as in vomiting the vermi-
cular motions of the ftomach and duodenum are
inverted, and their contents ejected, which is
probably owing to the exhauftion of the fpirit of
animation in the acting mufcles by a previous
excefllve flimulus, as by the root of ipecacuanha,
and the confequent defect of fenforial power. The
fame retrograde motions affect the whole inteftinal
canal in ileus ; and the cefophagus in globus hyf-
tericus. See this further explained in Sect. XXIX.
No. ii. on Retrograde Motions,

I muft obferve, alfo, that fomething fimilar hap-
pens in the production of our ideas, or fenfual
motions, when they are too weakly excited 5 when
any one is thinking intenfely about one thing,
and carelefsly converfing about another, he is
liable to ufe the word of a contrary meaning to

that

98 OF STIMULUS AND EXERTION. SECT. XII. 6.

that which he defigned, as cold weather for hot
weather, fummer for winter.

6. A certain quantity of (limulus, lefs than that
above mentioned, is/fucceeded by paralyfis, firft of
the voluntary and feniitive motions, and after-
wards of thofe of irritation and of affociation,
which conilitutes death.

Vf. Cure of increafed Exertion.

i. The cure, which nature has provided for the
increafed exertion of any part of the fyftem, con-
lifts in the confequent expenditure of the fenforial
power. But as a greater torpor follows this ex-
hauftion of fenforial power, as explained in the.
next paragraph, and a greater exertion fucceeds
this torpor, the conftitution frequently finks under
thefe increafing librations -between exertion and
quiefcence ; till at length complete quiefcence, that
is, death, clofes the fcene.

For, during the great exertion of the fyftem in
the hot fit of fever, an increafe of ftimulus is pro-
duced from the greater momentum of the blood,
the greater diftention of the heart and arteries, and
the increafed production of heat, by the violent
aclions of the fyftem occafioned by this augmenta-
tion of ftimulus, the fenforial power becomes di-
minifhed in a few hours much beneath its natural
quantity, the veflels at length ceafe to obey even
thefe great degrees of ftimulus, as fliewn in Sect.
XL. 9. i. and a torpor of the whole or of a part of
the fyftem enfues.

Now as this fecond cold fit commences with a
greater deficiency of fenforial power, it is alfo at-
tended with a greater deficiency of ftimulus than in
the preceding cold fit, that is, with lefs momentum
of blood, lefs diftention of the heart. On this ac-
count the fecond cold fit becomes more violent and

of

SECT. XII. 6. OF STIMULUS AND EXERTION. 99

of longer duration than the firft ; and as a greater
accumulation of fenforial power muft be produced
before the fyftern of veffels will again obey the di-
minifhcd ftimulus, it follows, that the fecond hot
fit of fever will be more violent than the former
one. And that unlefs fome other caufes counter-
act either the violent exertions in the hot fit, or
the great torpor in the cold fit, life will at length
be extinguifhed by the expenditure of the whole
of the ienforial power. And from hence it appears,
that the true means of curing fevers muft be fuch
as decreafe the aclion of the fyftem in the hot fit,
and increafe it in the cold fit ; that is, fuch as pre-
vent the too great diminution of fenforial power in
the hot fit, and the too great accumulation of it
in the cold one.

2. Where the exertion of the fenforial powers is
much increafed, as in the hot fits of fever or in-
flammation, the following are the ufual means of
relieving it. Decreafe the irritations by blood-
letting, and other evacuations ; by cold water taken
into the ftomach, or injected as an enema, or ufed
externally ; by cold air breathed into the lungs,
and diflufed over the Ikin ; with food of lefs ftimu-
lus than the patient has been accuftomed to.

3. As a cold fit, or paroxyfm of inactivity of
fome parts of the fyftem, generally precedes the hot
fit, or paroxyfm of exertion, by which the fenfo-
rial power becomes accumulated, this cold parox-
yfm fhould be prevented by ftimulant medicines
and diet, as wine, opium, bark, warmth, cheer-
fulnefs, anger, furprife.

4. Excite intD greater action fome other part of
the fyftem, by which means the fpirit of animation
may be in part expended, and thence the inordi-
nate actions of the difeafed part may be leffened.
Hence when a part of the Ikin acts violently, as of
the face in the eruption of the fmall pox, if the

feet

#t>o OF STIMULUS AND EXERTION. SECT. XII. 7.

feet be cold they fhould be covered. Hence the
ufe of a blilter applied near a topical inflammation.
Hence opium and warm bath relieve pains both
from excefs and defect of ftimulus.

5. Firft increafe the general ftimulation above its
natural quantity, which may in fome degree ex-
hauft the fpirit of animation, and then decreafe the
ftimulation beneath its natural quantity. Hence
after iudorific medicines and warm air, the appli-
cation of refrigerants may have greater effect, if
they could be adminiftered without danger of pro-
ducing too great torpor of fome part of the fyftem ;
as frequently happens to people in health from
coming out of a warm room into the cold air, by
which a topical inflammation in confequence of
torpor of the mucous membrane of the noftril is
produced, and is termed a cold in the head.

VII. Cure of decreqfed Exertion.
^d sqonjniru ia? afe'fOsaCl ; , . *

i. WHERE the exertion of the fenforial powers
is much decreafed, as in the cold fits of fever, a
gradual accumulation of the fpirit of animation
takes place ; as occurs in all cafes where inactivity
or torpor of a part of the fyftem exifts ; this accu-
mulation of fenforial power increafes, till ftimuli
lefs than natural are fufficient to throw it into
action, then the cold fit ceafes ; and from the ac-
tion of the natural ftimuli a hot one fucceeds with
increafed activity of the whole fyftem.

So in fainting fits, or fyncope, there is a tempo-
rary deficiency of fenforial exertion, and a confe-
quent quiefcence of a great part of the fyftem. This
quiefcence continues, till the fenforial power be-
comes again accumulated in the torpid organs;
and then the ufual diurnal ftimuli excite the revi-
vifcent parts again into action ; but as this kind
of quiefcence continues but a fhort time compared

to

SECT. XIT. 7. OF STIMULUS AND EXERTION. 101

to the cold paroxyfm of an ague, and lefs affects
the circulatory fyftem, a lefs fuperabundancy of
exertion fucceeds in the organs previoufly torpid,
and a lefs excefs of arterial activity. See Sect.
XXXIV. i. 6.

2. In the difeafes occafioned by a defect of fenfo-
rial exertion, as in cold fits of ague, hyfteric com-
plaint, and nervous fever, the following means are
t hole commonly ufed. i. Increafe the ftimulatioii
above its natural quantity for fome weeks, till a
new habit of more energetic contraction of the
fibres is eftablifhed. This is to be done by wine,
opium, bark, fteel, given at exact periods, and in
appropriate quantities ; for if thefe medicines be
given in fuch quantity, as to induce the lead de-
gree of intoxication, a debility fucceeds from the
ufelefs exhauftion of fpirit of animation in confe-
quence of too great exertion of the mufcles or or-
gans of fenfe. To thefe irritative ftimuli mould
be added the fenfitive ones of cheerful ideas, hope,
affection.

3. Change the kinds of ftimulus. The habits
acquired by the conftitution depend on fuch nice
circumftances, that when one kind of ftimulus
ceafes to excite the fenforial power into the quan-
tity of exertion neceffary to health, it is often fuf-
ficient to change the ftimulus for another appar-
ently fimilar in quantity and quality. Thus when
wine ceafes to ftimulate the conftitution, opium in
appropriate dofes fupplies the defect ; and the con-
trary. This is alfo obferved in the effects of ca-
thartic medicines, when one lofes its power, ano-
ther, apparently lefs efficacious, will fucceed. Hence
a change of diet, drink, and ftimulating medi-
cines, is often advantageous in difeafes of debi-
lity.

4. Stimulate the organs, whofe motions are af-
fociated with the torpid parts of the fyftem. The

actions

102 OF STIMULUS AND EXERTION. SECT. XII. 7,

actions of the minute veflels of the various parts
of the external Ikin are not only aflbciated with
each other, but are ftrongly aflbciated with thofe
of fome of the internal membranes, and particu-
larly of the ftomach. Hence when the exertion of
the ftomach is lefs than natural, and indigeftion
and heart-burn fucceed, nothing fo certainly re-
moves thefe fymptoms as the ftimulus of a blifter
on the back. The coldnefs of the extremities, as
of the nofe, ears, or fingers, are hence the beft in-
dication for the fuccefsful application of blifters.

5, Decreafe the ftimulus for a time. By leflen-
ing the quantity of heat for a minute or two by
going into the cold bath, a great accumulation of
ienfoiial power is produced ; for not only the mi-
nute veflels of the whole external fkin for a time
become inactive, as appears by their palenefs ; but
the minute veflels of the lungs lofe much of their
activity alfo by concert with thofe of the fkin, as
appears from the difficulty of breathing at firll
going into cold water. On emerging from the
bath the fenforial power is thrown into great exer-
tion by the ftimulus of the common degree of the
warmth of the atmofphere, and a great production
of animal heat is the confequence. The longer a
perfbn continues in the cold bath {he greater muft
be the prefent inertion of a great part of the fyftem,
and in confequence a greater accumulation of fen-
forial power. Whence M. Pome recommends
fome melancholy patients to be kept from two
to fix hours in fpring-water, and in baths ftill
colder.

6. Decreafe the ftimulus for a time below the
natural, and then increafe it above natural. The ef-
fect of this procefs, improperly ufed, is feen in giving
much food, or applying much warmth, to thofe
who have been previoufly expofed to great hunger,

or to great cold. The accumulated fenforial power
o

IS

SECT. XII. 7. OF STIMULUS AND EXERTION. 103

is thrown into fo violent exertion, that inflam-
mations and mortifications fupervene, and death
clofes the cataftrophe. In many difeafes this
method is the moft fuccefsful ; hence the bark in
agues produces more certain effect after the pre-
vious exhibition of emetics. In difeafes attended
with violent pain, opium has double the effecl:, if
venefection and a cathartic have been previoufly
ufed. On this feems to have been founded the
fuccefsful practice of Sydenham, who ufed vene-
feclion and a cathartic in chlorofis before the exhi-
bition of the bark, iteel, and opiates.

7. Prevent any unneceffary expenditure offen-
forial power. Hence in fevers with debility, a
decumbent pofture is preferred, with iilence, lit-
tle light, and fuch a quantity ,of heat as may pre-
vent any chill fenfation, or any coldnefs of the
extremities. The pulfe of patients in fevers with
debility increafes in frequency above ten pulfations
in a minute on their riling out of bed. For the
expenditure of fenforial power to preferve an erect
pofture of the body adds to the general deficiency
of it, and thus affects the circulation.

8. The longer in tijne and the greater in degree
the quiefcence or inertion of an organ has been, fo
that it ftiil retains life or excitability, the lefs fti-
mulus mould at firft be applied to it. The quan-
tity of ftimulation is a matter of great nicety to de-
termine, where the torpor or quiefcence of the
fibres has been experienced in a great degree, or
for a confiderable time, as in cold fits of the ague,
in continued fevers with great debility, or in peo-
ple famifhed at fea, or perifhing with cold. In
the two laft cafes, very minute quantities of food
mould be firft fupplied, and very few additional
degrees of heat. In the two former cafes, but lit-
tle ftimulus of wine or medicine, above what they
had been lately accuftomed to, fliould be exhibited,

and

104 OF STIMULUS AND EXERTION. SECT. XII. 7.

and this at frequent and ftated intervals, fo that
the effect of one quantity may be obferved before
the exhibition of another.

If thefe circumftances are not attended to, as the
fenforial power becomes accumulated in the quief-
cent fibres, an inordinate exertion takes place by
the increafe of ftimulus acting on the accumulated
quantity of fenforial power, and either the para-
lyfis, or death of the contractile fibres enfues, from
the total expenditure of the fenforial power in the
affected organ, owing to this increafe of exertion,
like the debility after intoxication. Or, fecondly,
the violent exertions above mentioned produce
painful fenfation, which becomes a new ftimulus,
and by thus producing inflammation, and increaf-
ing the activity of the fibres already too great, fooner
exhaufts the whole of the fenforial power in the
acting organ, and mortification, that is. the death
of the part, f upervenes.

Hence there have been many inftances of peo-
ple, whofe limbs have been long benumbed by ex-
pofure to cold, who have loft them by mortifica-
tion on their being too haftily brought to the fire ;
and of others, who were nearly famifhed at fea,
who have died foon after having taken not more
than an uiual meal of food. I have heard of two
well-attefted inftances of patients in the cold fit of
ague, who have died from the exhibition of gin
and vinegar, by the inflammation which enfued.
And in many fevers attended with debility, the
unlimited ufe of wine, and the wanton application
of blifters, I believe, has deftroyed numbers by the
debility confequent to too great ftimulation, that
is, by the exhauftion of the fenforial power by its
inordinate exertion.

Wherever the leaft degree of intoxication exifts,
a proportional debility is the confequence ; but
there is a golden rule by which the neceffary and

ufeful

SECT. XII. 7. OF STIMULUS AND EXERTION. 105

ufeful quantity of flimulus in fevers with debility-
may be afcertained. When wine or beer are exhi-
bited either alone or diluted with water, if the
pulfe becomes flower the ilimulus is of a proper
quantity ; and ihould be repeated every two or
three hours, or when the pulfe again becomes
quicker.

In the chronical debility brought on by drink-
ing fpirituousor fermented liquors, there is another
golden rule by which I have fuccefsfully directed
the quantity of fpirit which they may fafely leflen,
for there is no other means by which they can re-
cover their health. It fliould be premifed, that
where the power of digeftion in thefe patients is
totally deftroyed, there is not much reafon to ex-
peel a return to healthful vigour.

I have directed feveral of thefe patients to omit
one fourth part of the quantity of vinous fpirit
they have been lately accuftomed to, and if in a
fortnight their appetite increafes, they are advifed
to omit another fourth part ; but if they perceive
that their digeftion becomes impaired from the
want of this quantity of fpirituous potation, they
are advifed to continue as they are, and rather
bear the ills they have, than rifk the encounter of
greater. At the fame time flem-meat with or with-
out fpice is recommended, with Peruvian bark and
fteel in fmall quantities between their meals, and
half a grain of opium or a grain, with five or eight
grains of rhubarb at night.^

SECT.

io6 OF VEGETABLE ANIMATION. SECT. XIII. i.

— -tii!

SECT. XIII.

OF VEGETABLE ANIMATION.

I. i. Vegetables are irritable* mimofa, dioncca mufci-
pitla. Vegetable fecretions. 2. Vegetable buds are
inferior animals^ are liable to greater or lefs irrita-
bility. II. Stamens and piftils of plants /hew marks
of jenfibility. III. Vegetables poffefs fome degree of
volition. IV. Motions of plants are affociated like
ih of e of animals* V. i. Vegetable ftruElure like that
of animals > their anthers and fligmas are living crea-
tures. Male- flowers of Vaiiifneria. i. Whether
'vegetables poffefs ideas ? *They have organs of fenfe as
of touch and f melt 9 and ideas of external things ?

I. |. The fibres of the vegetable world, as well
as thofe of the animal, are excitable into a variety
of motion by irritations of external objects. This
appears particularly in the mimofa or feniitive plant,
whofe leaves contract on the flighted injury ; the
dionsea mufcipula, which was lately brought over
from the marfhes of America, prefents us with
another curious inflance of vegetable irritability ;
its leaves are armed with fpines on their upper edge,
and are fpread on the ground around the flem ;
when an infect creeps on any of them in its paffage
to the flower or feed, the leaf {huts up like a fleel
rat-trap, and deftroys its enemy. See Botanic
Garden, Part II. note on Silene.

The various fecretions of vegetables, as of odour,
fruit, gum, refin, wax, honey, feem brought about
in the fame manner as in the glands of animals ;
the taflelefs moifture of the earth is converted by
the hop-plant into a bitter juice > as by the cater-

pillar

SECT. XIII. i. OF VEGETABLE ANIMATION. 107

pillar in the nut-fhell, the fweet kernel is converted
into a bitter powder. While the power of abforp-
tion in the roots and barks of vegetables is excited
into aftion by the fluids applied to their mouths
like the lacteals and lymphatics of animals.

2. The individuals of the vegetable world may
be confidered as inferior or lefs perfect animals ; a
tree is a congeries of many living buds, and in this
refpect refembles the branches of coralline, which
are a congeries of a multitude of animals. Each
of thefe buds of a tree has its proper leaves or petals,
for lungs, produces its viviparous or its oviparous
offspring in buds or feeds ; has its own roots, which
extending down the ftem of the tree are interwo-
ven with the roots of the other buds, and form the
bark, which is the only living part of the item, is
annually renewed, and is fuperinduced upon the
former bark, which then dies, and with its ftag-
nated juices gradually hardening into wood forms
the concentric circles, which we fee in blocks of
timber.

The following circumftances evince the indivi-
duality of the buds of trees. Firft, there are many
trees, whofe whole internal wood is periihed, and
yet the branches are vegete and healthy. Secondly,
the fibres of the barks of trees are chieffy longitu-
dinal, refembling roots, as is beautifully feen in
thofe prepared barks, that were lately brought from
Otaheita. Thirdly, in horizontal wounds of the
bark of trees, the fibres of the upper lip are always
elongated downwards like roots, but thofe of the
lower lip do not approach to meet them. Fourthly,
if you wrap wet mofs round any joint of a vine, or
cover it with moift earth, roots will {hoot out from
it. Fifthly, by the inoculation or engrafting of
trees many fruits are produced from one item.
Sixthly, a new tree is produced from a branch
plucked from an old one, and fet in the ground.

I Whence

lo8 OF VEGETABLE ANIMATION. SECT. XIII. 2.

Whence it appears that the buds of deciduous trees
are fo many annual plants, that the bark is a con-
texture of the roots of each individual bud ; and
that the internal wood is of no other ufe but to
fupport them in the air, and that thus they refera-
ble the animal world in their individuality.

The irritability of plants, like that of animals,
appears liable to be increafed or decreafed by habit ;
for thofe trees or fhrubs, which are brought from
a colder climate to a warmer, put out their leaves
and bloflbms a fortnight fooner than the indige-
nous ones.

ProfefTor Kalm, in his Travels in New York,
obferves that the apple-trees brought from England
bloffom a fortnight fooner than the native ones.
In our country the fhrubs, that are brought a de-
gree or two from the north, are obferved to flou-
rifh better than thofe, which come from the fouth.
The Siberian barley and cabbage are faid to grow
larger in this climate than the fimilar more fouthern
vegetables. And our hoards of roots, as of pota-
toes and onions, germinate with lefs heat in fpring,
after they have been accuftomed to the winter's
cold, than in autumn after the fummer's heat.

II. The ftamens and piftils of flowers fhew evident
marks of fenfibility, not only from many of the
ftamens and fome piftils approaching towards each
other at the feafon of impregnation, but from many
of them clofing their petals and calyxes during the
cold parts of the day. For this cannot be afcrib-
ed to irritation, becaufe cold means a defect of the
ftimulus of heat ; but as the want of accuftomed
ftimuli produces pain, as in coldnefs, hunger, and
thirft of animals, thefe motions of vegetables in
doling up their flowers muftbe afcribed to the difa-
greeable fenfation, and not to the irritation of cold.
Others clofe up their leaves during darknefs, which,

like

SECT. XIII. 4. OF VEGETABLE ANIMATION. 109

like the former, cannot be owing to irritation, as
the irritating material is withdrawn.

The approach of the anthers in many flowers to
the ftigmas, and of the piftils of fome flowers to
the anthers, muft be afcribed to the pallion of love,
and hence belongs to fenfation, not to Irritation.

III. That the vegetable world poflefies fome de-
gree of voluntary powers, appears from their ne-
ceflity to ileep, which we have (hewn in Sect.
XVIII. to confift in the temporary abolition of vo-
luntary power. This voluntary power feems to be
exerted in the circular movement of the tendrils
of vines, and other climbing vegetables ; or in the
efforts to turn the upper furface of their leaves, or
their flowers to the light.

IV. The aflbciations of fibrous motions are ob-
fervable in the vegetable world, as well as in the
animal. The diviiions of the leaves of the fenfitive
plant have been accuftomed to contract at the fame
time from the abfence of light ; hence if by any
other circumflance, as a flight ftroke or injury, one
divifion is irritated into contraction, the neigh-
bouring ones contract alfo, from their motions
being affociated with thofe of the irritated part.
So the various ftamina of the clafs of fyngenefia
have been accuftomed to contract together in the
evening, and thence if you ftimulate one of them
with a pin, according to the experiment of M.
Colvolo, they all contract from their acquired af-
fociations.

To evince that the collapfing of the fenfitive plant
is not owing to any mechanical vibrations propa-
gated along the whole branch, when a fingle leaf
is ftruck with the finger, a leaf of it was flit with
(harp fcifibrs, and fome feconds of time palled be-
fore the plant feemed fenfible of the injury ; and
then the whole branch collapfed as far as the prin-

1 2 cipal

I io OF VEGETABLE ANIMATION. SECT. XIII. 5 .

cipal ftem : this experiment was repeated feveral
times with the leaft poffible impulfe to the plant.

V. i. For the numerous circumftances in which
vegetable buds are analogous to animals, the reader
is referred to the additional notes at the end of the
Botanic Garden, Part I. It is there (hewn, that
the roots of vegetables refembie the lacteal fyi-
temof animals; the fap-veffels in the early fpring,
I before their leaves expand, are analogous to the
placental veffels of the foetus ; that the leaves of
land-plants refembie lungs, and thofe of aquatic
plants the gills of fifli; that there are other fyilems
of veffels refembling the vena portarum of quadru-
peds, or the aorta of fifti ; that the digeftive power
of vegetables is fimilar to that of animals convert-
ing the fluids, which they abforb, into fugar ; that
their feeds refembie the eggs of animals, and their
buds and bulbs their viviparous offspring. And,
laftly, that the anthers and fiigmas are real animals,
attached indeed to their parent tree like polypi or
coral infects, but capable of fpontaneous motion :
that they are affected with the paffion of love, and
furnifhed with powers of reproducing their fpecies,
and are fed with honey like the moths and butter-
flies, which plunder their nectaries. See Botanic
Garden, Part I. add. note XXXIX.

The male flowers of vallifneria approach ftili
nearer to apparent animality, as they detach them-
felves from the parent plant, and float on the fur-
face of the water to the female ones. Botanic
Garden, Part II. Art. Vallifneria. Other flowers
of the claffes of monecia and diecia, and polygamia,
difcharge the fecundating farina, which floating in
the air is carried to the iHgma of the female flow-
ers, and that at confiderable diftances. Can this
be effected by any fpecific attraction ? or, like the
diffufion of the odorous particles of flowers, is it
left to the currents of winds, and the accidental

mifcarriages

SECT. XIII. 5. OF VEGETABLE ANIMATION. 1 1 1

mifcarriages of it counteracted by the quantity of
its produclion ?

2. This leads us to a curious enquiry, whether
vegetables have ideas of external things ? As all
our ideas are originally received by our fenfes, the
queftion may be changed to, whether vegetables
poflefs any organs of fenfe ? Certain it is, that they
poflefs a fenfe of heat and cold, another of moifture
and drynefs, and another of light and darknefs ;
for they clofe their petals occafionally from the pre-
fence of cold, moifture, or darknefs. And it has ,
been already fhewn, that thefe actions cannot be
performed (imply from irritation, becaufe cold and
darknefs are negative quantities, and on that ac-
count fenfation or volition are implied, and in con-
fequence a fenforium or union of their nerves. So
when we go into the light, we contract the iris ;
not from any ftimulus of the light on the fine muf-
cles of the iris ; but from its motions being aflb-
ciated with the fenfation of too much light on the
retina : which could not take place without a fen-
forium or center of union of the nerves of the
iris with thofe of villon. See Botanic Garden,
Part I, Canto 3. 1. 440. note.

Beiides thefe organs of fenfe, which diftinguifh
cold, moifture, and darknefs, the leaves of rnimo-
fa, and of dionxa, and of drofera, and the ftamens
of many flowers, as of the berbery, and the nu-
merous clafs of fyngene(ia? are fenfible to mechanic
impact, that is, they poflefs a fenfe of touch, as
well as a common fenforium ; by the medium of
which their mufcles are excited into action. Laftly,
in many flowers the anthers, when mature, ap-
proach the ftigrna, in others the female organ ap-
proaches to the male. In a plant of coilinibnia, a
branch of which is now before me, the two yellow
ftamens are about three eighths of an inch high,
and diverge from each other, at an angle of about

fifteen

I iz OF VEGETABLE ANIMATION. SECT. XIII. 5.

fifteen degrees, the purple flyle is half an inch high,
and in fome flowers is now applied to the itamen
on the right hand, and in others to that of the
left ; and will, I fuppofe, change place to-morrow
in thofe, where the anthers have not yet effufed
their powder.

I afk, by what means are the anthers in many
flowers, and fligmas in other flowers, directed to
find their paramours? How do either of them
know, that the other exifts in their vicinity ? Is
this curious kind of ftorge produced by mechanic
attraction, or by the fenfation of love ? The latter
opinion is fupported by the ftrongeft analogy, be-?
caufe a reproduction of the fpecies is the confe-
quence ; and then another organ of fenfe muft be
wanted to direct thefe vegetable amourettes to find
each other, one probably analogous to our fenfe of
fmell, which in the animal world directs the new-
born infant to its fource of nourifhment, and they
may thus poffefs a faculty of perceiving as well as
'\ of producing odours.

Thus, befides a kind of tafte at the extremities
of their roots, fimilar to that of the extremities of
our lacteal veffels, for the purpofe of felecling their
proper food : and befides different kinds of irrita-
bility refiding in the various glands, which fepa-
rate honey, wax, reiin, and other juices from their
blood; vegetable life feems to pofiefs an organ of
fenfe to diftinguifh the variations of heat, another
to diftinguifh the varying degrees of moifture,
another of light, another of touch, and probably
another analogous to our fenfe of fmell. To thefe
muft be added the indubitable evidence of their
pafiion of love, and I think we may truly conclude,
that they are furnifhed with a common fenforium
belonging to each bud, and that they muft occafion-
repeat thofe perceptions either in their dreams

or

SECT. XIV. i. PRODUCTION OF IDEAS. 113

or waking hours, and confequently poflefs ideas of
fo many of the properties of the external world,
and of their own exiftence.

SECT. XIV.

OF THE PRODUCTION OF IDEAS.

It Of material and immaterial beings. Doctrine of St.
Paul. II. i. Of the fenfe of touch. Of folidity.
2. Of fgure. Motion. Time. Place. Space.
Number. 3. Of the penetrability of matter. 4.
Spirit of animation foffeffes folidity ', figure, wfibiUty,
&c. Of fpirits and angels. 5. The exiftence of ex-
ternal things. III. Of vi/ion. IV. Of hearing.
V. Of f mil and iafte. VI. Of the organ of fenfe
by which we perceive heat and cold, not by the fenfe
of touch. VI I. Of the fenfe of extenfion, the whole
of the locomotive mufcles may be confidered as one or-
gan of fenfe. VIIL Of- the fenfe 5 of hunger, thirft,
want offreftj air, fuckling children, and luft. 1 X ,
Of many other organs of fenfe belonging to the glands.
Of pairful fenf at ions from the excefs of light, prejjtlire^
heat, itching, cauflics, and eleclricity.

I. PHILOSOPHERS have been much perplexed
to underftand, in what manner we become ac-
quainted with the external world ; infomuch that
Dr. Berkley even doubted its exiftence, from having
obferved (as he thought) that none of our ideas
refemble their correfpondent objects. Mr. Hume
aflerts, that our belief depends on the greater dif-

tinclncfs

ii4 PRODUCTION OF IDEAS. SECT. XIV. i.

tinctnefs or energy of our ideas from perception ;
and Mr. Reid has lately contended, that our belief
of external objects is an innate principle neceflarily
joined with our perceptions.

So true is the obfervation of the famous Mai-
branch, " that our fenfes are not given us to dif-
cover the eflences of things, but to acquaint us with
the means of preferving our exiftence," (L. I. ch. v.)
a melancholy reflection to philofophers !

Some philofophers have divided all created
beings into material and immaterial : the former
including all that part of being, which obeys the
mechanic laws of action and reaction, but which
can begin no motion of itfelf ; the other is the
caufe of all motion, and is either termed the power
of gravity, or of fpecific attraction, or the fpirit
of animation. This immaterial agent is fuppofed
to exift in or with matter, but to be quite diftincl
from it, and to be equally capable of exiftence,
after the matter, which now pofleffes it, is decom-
pofed*

Nor is this theory ill fupported by analogy, fince
heat, electricity, and magnetifm, can be given to
or taken from a piece of iron ; and muft therefore
exift, whether feparated from the metal, or com-
bined with it. From a parity of reafoning, the
fpirit of animation would appear to be capable of
cxifting as well feparately from the body as with
it.

I beg to be underftood, that I do not wifli to
difpute about words, and am ready to allow, that
the powers of gravity, fpecific attraction, electri-
city, magnetifm, and even the fpirit of animation,
may confift of matter of a finer kind ; and to be-
lieve, with St. Paul and Malbranch, that the ulti-
mate caufe only of all motion is immaterial, that
is God. St. Paul fays, " in him we live and move,
and have our being j" and in the i5th chapter to

the

SECT. XIV. 2. PRODUCTION OF IDEAS. 1 1 5

the Corinthians, diftinguifhes between the pfyche
or living fpirit, and the pneuma or reviving fpi-
rit. By the words fpirit of animation or fenibrial
power, I mean only that animal life, which man-
kind poflefies in common with brutes, and in fome
degree even with vegetables, and leave the con-
fideration of the immortal part of us, which is the
object of religion, to thole who treat of revela-
tion.

II. i. OftheSenfe of Touch.

THE firft idea we become acquainted with, arc
thofe of the fenfe of touch ; for the foetus muft ex-
perience fome varieties of agitation, and exert fome
mufcular action, in the womb ; and may with
great probability be fuppofed thus to gain fome
ideas of its own figure, of that of the uterus, and
of the tenacity of the fluid, that furrounds it, (as
appears from the fafts mentioned in the fucceeding
Section upon Inftinct.)

Many of the organs of fenfe are confined to a
fmall part of the body, as the noftrils, ear, or eye,
whilft the fenfe of touch is diffufed over the whole
fkin, but exifts with a more exquifite degree of
delicacy at the extremities of the fingers and
thumbs, and in the lips. The fenfe of touch is
thus very commodioufly difpofed for the purpofe
of encompailing fmaller bodies, and for adapting
itfelf to the inequalities of larger ones. The figure
of fmall bodies feems to be learnt by children by
their lips as much as by their fingers ; on which
account they put every new object to their mouths,
when they are fatiated with food, as well as when
they are hungry. And puppies feem to learn their
ideas of figure principally by the lips in their mode
of play.

We

n<S PRODUCTION OF IDEAS. SECT.XIV. 2.

We acquire our tangible ideas of objects either
by the fimple preflure of this organ of touch againft
a folid body, or by moving our organ of touch
along the furface of it. In the former cafe we learn
the length and breadth of the object by the quan-
tity of our organ of touch, that is imprefied by it :
in the latter cafe we learn the length and breadth
of objects by the continuance of their preflure on
our moving organ of touch.

It is hence, that we are very flow in acquiring
our tangible ideas, and very flow in recollecting
them ; for if I now think of the tangible idea of a
cube, that is, if I think of its figure, and of the
folidity of every part of that figure, I muft con-
ceive ipyfelf as pafling my fingers over it, and feem
in fome meafure to feel the idea, as 'I formerly did
the impreflion, at the ends of them, and am thus
very flow in diftinctly recollecting it.

When a body comprefles any part of our fenfe
of touch, what happens ? Firft, this part of our
fenforium undergoes a mechanical compreflion,
which is termed a iHmulus ; fecondly, an idea, or
contraction of a part of the organ of fenfe is ex-
cited ; thirdly, a motion of the central parts, or of
the whole fenforium, which is termed fenfation, is
produced ; and thefe three conilitute the percep-
tion of folidity.

2. Of Figure, Motion, Time, Place, Space, Number.

No one will deny, that the medulla of the brain
and nerves has a certain figure ; which, as it is
diffufed through nearly the whole of the body,
muft have nearly the figure of that body. Now it
follows, that the fpirit of animation, or living prin-
ciple, as it occupies this medulla, and no other
part, (which is evinced by a great variety of cruel
experiments on living animals,) it follows, that

this

S*CT. XIV. 2. PRODUCTION OF IDEAS. 117

this fpirit of animation has alfo the fame figure as
the medulla above defcribed. I appeal to com-
mon fenfe ! the fpirit of animation acts, Where
does it act ? It acts wherever there is the medulla
above mentioned ; and that whether the limb is
yet joined to a living animal, or whether it be re-
cently detached from it ; as the heart of a viper or
frog will renew its contractions, when pricked
with a pin, for many minutes of time after its ex-
fection from the body. — Does it act any where
elfe ? — No ; then it certainly exifts in this part of
(pace, and no where elfe ; that is, ir hath figure ;
namely, the figure of the nervous fyilem, which is
nearly the figure of the body. When the idea of
iolidity is excited, as above explained, a part of
the exteniive organ of touch is comprefled by fome
external body, and this part of the fenibrium fo
compreffed exactly refembles in figure the figure. of
the body that compreffcd it. Hence, when we
acquire the idea of folidity, we acquire at the fame
time the idea of FIGURE; and this idea of figure,
or motion of a part of the organ of touch, exactly
refembles In its figure the figure of the body that
occafions it ; and thus exactly acquaints us with
this property of the external world.

Now, as the whole univerfe with all its parts
poftefies a certain form or figure, if any part of it
moves, that form or figure of the whole is varied :
hence, as MOTION is no other than a perpetual va-
riation of figure, our idea of motion is alfo a real
refemblance of the motion that produced it.

It may be faid in objection to this definition of
motion, that an ivory globe may revolve on its
axis, and that here will be a motion without change
of figure. But the figure of the particle % on one
iide of this globe is not the fame figure as the figure
of/ on the other fide-, any more than the particles
themfelves are the fame, though they are fimilar

figures ;

1 1 8 PRODUCTION OF IDEAS. SECT. XIV. 2.

figures ; and hence they cannot change place with
each other without difturbing or changing the
figure of the whole.

Our idea of TIME is from the fame fource, but
is more abftracted, as it includes only the com-
parative velocities of thefe variations of figure ;
hence if it be afked, How long was this book in
printing ? it may be anfwered, Whiift the fun was
pa'iling through Aries.

Our idea of PLACE includes only the figure of
a group of bodies, not the figures of the bodies
themfelves. If it be aiked, where is Nottingham-
fhn'e, the anfwer is, it is furrounded by Derby-
mire, Lincolnlhire, and Leiceflerfhire ; hence place
is our idea of the figure of one body furrounded
by the figures of other bodies.

The idea of SPACE is a more abftracted idea of
place excluding the group of bodies.

The idea of NUMBER includes only the particu-
lar arrangements, or diftributions of a group of
bodies, and is therefore only a more abftracted
idea of the parts of the figure of the group of
bodies s thus when I fay England is divided into
forty counties, I only fpeak of certain divifions of
its figure.

Hence arifes the certainty of the mathematical
fciences, as they explain theie properties of bodies,
which are exactly refembied by our ideas of them,
whilft we are obliged to collect almoft all our other
knowledge from experiment ; that is, by obferv-
ing the effects exerted by one body upon another.

3. Of the Penetrability of Matter.

The impoflibility of two bodies exifling together
in the fame fpace cannot be deduced from our idea
of folidity, or of figure. As foon as we perceive
the motions of objects that furround us, and learn

that

SECT. XIV. 2. PRODUCTION OF IDEAS. 1 1$

that we pofTefs a power to move" our own bodies,
we experience, that thofe objects, which excite in
us the idea of folidity and of figure, oppofe this
voluntary movement of our own organs ; as whilft
I endeavour to comprefs between my hands an
ivory ball into a fpheroid. And we are hence
taught by experience, that our own body, and thofe
which we touch, cannot exift in the fame part of
fpace.

But this by no means demonftrates, that no two
bodies can exift together in the fame part of fpace.
Galilseo in the preface to his works feems to be of
opinion, that matter is not impenetrable ; Mr.
Michel, arid Mr. Bofcowich in his Theoria Philof.
Natur. have efpoufed this hypothecs ; which has
been lately publifhed by Dr. Prieftley, to whom the
world is much indebted for fo many important dif-
coveries in fcience. (Hift. of Light and Colours,
p. 391.) The uninterrupted paflage of light through
transparent bodies, of the electric aether through
metallic and aqueous bodies, and of the magnetic
effluvia through all bodies, would feem to give fome
probability to this opinion. Hence it appears, that
beings may exift without poffeffing the property
of folidity, as well as they can exift without poffef-
fing the properties, which excite our fmell or tafte,
and can thence occupy fpace without detruding
other bodies from it ; but we cannot become ac-
quainted with fuch beings by our fenfe of touch,
any more than we can with odours or flavours
without our fenfes of fmell and tafte.

But that any being can exift without exifting in
fpace, is to my ideas utterly incomprehenfible.
My appeal is to common fenfe. To be implies a
when and a where ; the one is comparing it with
the motions of other beings, and the other with
their fituations.

If

120 PRODUCTION OF IDEAS. SECT. XiV. 2,

If there was but one objecl, as the whole crea-
tion may be confidered as one object, then I can-
not alk where it exifls ? for there are no other ob*
jecls to compare its fituation with. Hence if any
one denies, that a being exifts in fpace, he denies,
that there are any other beings but that one ; for
to anfwer the queftion, " Where does it exift ?"
is only to mention the fituation of the objects that
iurround it.

In the fame manner if it be aiked — <c When does
a being exift ?" 1 he anfwer only fpecifies the fuc-
ceffive motions either of itfelf, or of other bodies ;
hence to fay, a body exifts not in time, is to fay,
that there is, or was, no motion in the world.

4. Of the Spirit of Animation-

But though there may exift beings in the uni-
verfe, that have not the property of folidity ; that
is, which can poflefs any part of fpace, at the fame
time that it is occupied by other bodies ; yet there
may be other beings, that can afTume this property
of folidity, or difrobe themfelves of it occafionally,
as we are taught of fpirits, and of angels ; and it
would feem, that THE SPIRIT OF ANIMATION muft
be endued with this property, otherwife how could
it occafionally give motion to the limbs of animals?
— or be itfelf ftimulated into motion by the obtru-
fions of furrounding bodies, as of light, or odour ?

If the fpirit of animation was always neceflarily
penetrable, it could not influence or be influenced
by the folidity of common matter ; they would
exift together, but could not detrude each other
from the part of fpace, where they exift ; that is,
they could 'not communicate motion to each other.
No two things can influence or affect each other, which
have not fome property common to both of them / for to
influence or affecl: another body is to give or com-
municate

SECT. XIV. 2. PRODUCTION OF IDEAS. 121

muuicate fome property to jit, that it had not be-
fore ; but how can one body give that to another,
which it does not pofTefs itfelf ? — The words im-
ply, that they muft agree in having the power or
faculty of poffefiing fonie common property. Thus
if one body removes another from the part of fpace,
that it poflefies, it muft have the power of occupy-
ing that ipace itfelf: and if one body communicates
heat or motion to another, it follows, that they
have alike the property of poflefling heat, or mo-
tion.

Hence the fpirit of animation at the time it com-
municates or receives motion from folid bodies,
muft itfelf poflefs fome property of foiidity. And
in confequence at the time it receives other kinds
of motion from light, it muft poflefs that property,
which light poflefles, to communicate that kind of
motion ; and for which no language has a name,
unlefs it may be termed Vifibility. And at the
time it is ftimulated: into other kinds of animal
motion by the particles of fapid and odorous bodies
affecting the fenles of tafte and fmell, it muft refem-
ble thefe particles of flavour, and of odour, in pof-
fefling fome fimilar or correfpondent property ;
and for which language has no name, unlefs we
may ufe the words Saporoiity and Odoroiity for
thofe common properties, which are poflefled by
our organs of tafte and fmell, and by the particles
of fapid and odorous bodies ; as the words Tangi-
bility and Audibility may expreis the common pro-
perty poflefled by our organs of touch, and of
hearing, and by the folid bodies, or their vibra-
tions, which affecl thofe organs.

5. Finally, though the figures of bodies are in
truth reiembled by the figure of the part of the
organ of touch, which is ftimulated into motion ;
and that organ refembles the folid body, which
ftimulates it, in its property of foiidity ; and though

the

122 PRODUCTION OF IDEAS. SECT. XIV. 2.

the fenfe of hearing resembles the vibrations of ex-
ternal bodies in its capability of being ftimulated
into motion by thofe vibrations ; and though our
other organs of fenfe refemble the bodies, that fti-
mulate them, in their capability of being ftimulat-
ed by them ; and we hence become acquainted with
thefe properties of the external world ; yet as we
can repeat all thefe motions of our organs of fenfe
by the efforts of volition, or in confequence of
the fenfation of pleafure or pain, or by their affo-
ciation with other fibrous motions, as happens in
our reveries or in fleep, there would ftill appear to
be fome difficulty in demonftrating the exiftence
of any thing external to us.

In our dreams we cannot determine this circum-
fiance, becaufe our power of volition is fufpended,
and the {Hmuli of external objeclss are excluded ;
but in our waking hours we can compare our ideas
belonging to one fenfe with thofe belonging to
another, and can thus diftinguifh the ideas occa-
fioned by irritation from thofe excited by fenfation,
volition, or affociation. Thus if the idea of the
fweetnefs of fugar fhould be excited in our dreams,
the whitenefs and hardnefs of it occur at the fame
time by affociation ; and we believe a material
lump of fugar prefent before us. But if, in our
waking hours, the idea of the fweetnefs of fugar
occurs to us, the ftimuli of furrounding objects,
as the edge of the table, on which we prefs, or
green colour of the grafs, on which we tread, pre-
vent the other ideas of the hardnefs and whitenefs
of the fugar from being exerted by affociation.
Or if they fhould occur, we voluntarily compare
them with the irritative ideas of the table or grafs
above mentioned, and detect their fallacy. We
can thus diftinguifh the ideas caufed by the flimuli
of external objeds from thofe, which are intro-
duced by affociation, fenfation, or volition; and

during

SECT. XIV. 3- PRODUCTION OF IDEAS. 123

during our waking hours can thus acquire a know-
ledge of the external world. Which neverthelefs
we cannot do in our dreams, becaufe we have nei-
ther perceptions of external bodies, nor the power
of volition to enable us to compare them with the
ideas of imagination.

III. OfVifion.

OUR eyes obferve a difference of colour, or of
fhade, in the prominences and depreflions of ob-
jects, and that thole fhades uniformly vary, when
the fenfe of touch obferves any variation. Hence
when the retina becomes flimulated by colours or
fhades of light in a certain form, as in a circular
fpot ; we know by experience, that this is a fign,
that a tangible body is before us; and that its
figure is refembled by the miniature figure of the
part of the organ of vifion, that is thus ftimulat-
ed.

Here whilft the ftimulated part of the retina re-
fembles exactly the vifible figure of the whole in
miniature, the various kinds of ftimuli from dif-
ferent colours mark the vifible figures of the mi-
nuter parts ; and by habit we inilantly recall the
tangible figures.

Thus when a tree is the object of fight, a part
of the retina refembling a flat branching figure is
Simulated by various fhades of colours ; but it is
by fuggeftion, that the gibbofity of the tree, and
the mofs, that fringes its trunk, appear before us.
Thefe are ideas of fuggeftion, which we feel or
attend to, affociated with the motions of the reti-
na, or irritative ideas, which we do not attend
to.

So that though our vifible ideas refemble in mi-
niature the outline of the figure of coloured bodies,
in other refpecb they ferve only as a language,

K which

J24 PRODUCTION OF IDEAS. SECT. XIV. 4.

which by acquired aflbciations introduce the tan-
gible ideas of bodies. Hence it is, that this fenfe
is fo readily deceived by the art of the painter to
our amufement and inftruclion. The reader will
find much very curious knowledge on this fubject
in Bifhop Berkley's EfTay on Vifion, a work of great
ingenuity.

The immediate object however of the fenfe of
vifion is light ; this fluid, though its velocity is fa
great, appears to have no perceptible meehankal
impulfe, as was mentioned in the third Section,
but teems to ftimulate the retina into animal mo-
tion by its tranfmiffion through this part of the
fenferium : for though the eyes of cats or other
animals appear luminous in obfcure places ; yet it
is probable, that none of the light, which falls on
the retina, is reflected from it, but adheres to or
enters into combination with the choroide coat be-
hind it.

The combination of the particles of light with
opake bodies, and therefore with the choroide coat
of the eye, is evinced from the heat, which is given
out, as in other chemical combinations. For the
fun-beams communicate no heat in their paflage
through tranfparent bodies, with which they do
not combine, as the air continues cool even in the
focus of the largeft burning-glands, which in a mo-
ment vitrifies a particle of opaque matter.

IV. Oftfa Organ of Hearing.

IT is generally believed, that the tympanum of
the ear vibrates mechanically, when expofed to
audible founds, like the firings of one mufical in-
ftrument, when the fame notes are ftruck upon
another. Nor is this opinion improbable, as the
mufcles and cartilages of the larynx are employed
in producing variety of tones by mechanical vibra-
tion :

SECT. XIV. 4. PRODUCTION OF IDEAS. 125

tion : fo the mufcles and bones of the ear feem
adapted to increafe or diminifh the tenfion of the
tympanum for the purpofes of fimilar mechanical
vibrations.

But it appears from direction, that the tympa-
num is not the immediate organ of hearing, but
that like the humours and cornea of the eye, it is
only of ufe to prepare the object for the immediate
organ. For the portio mollis of the auditory nerve
is not fpread upon the tympanum, but upon the
veftibulum, and cochlea, and femicircular canals
of the ear ; while between the tympanum and the
expanfion of the auditory nerve the cavity is faid
by Dr. Cotunnus and Dr. Meckel to be filled with
water ; as they had frequently obferved by freez-
ing the heads of dead animals before they diflected
them ; and water being a more denfe fluid than
air is much better adapted to the propagation &
vibrations. We may add, that even the external
opening of the ear is not abfolutely neceiTary for
the perception of found : for fome people, who
from thefe defects would have been completely deaf,
have diftinguifhed acute or grave founds by the
tremours of a flick held between their teeth pro-
pagated along the bones of the head, (Haller. Phyf.
T. V. p. 295).

Hence it appears, that the immediate organ of
hearing is not affefted by the particles of the air
themfeives, but is ftimulated into animal motion
by the vibrations of them. And it is probable from
the loofe bones, which are found in the heads of
fome fifties, that the vibrations of water are fenfi-
ble to the inhabitants of that element by a fimilar
organ.

The motions of the atmofphere, which we be-
come acquainted with by the fenfe of touch, are
combined with its folidity, weight, or vis inertise ;
whereas thofe, that are perceived by this organ,

K 2 depend

1*6 PRODUCTION OF IDEAS. SECT. XIV. 5.

depend alone oil its elaftidty. But though the vi-
bration of the air is the immediate object of the
ienfe of hearing, yet the ideas, we receive by this
fenfe, like thole received from light, are only as a
language, which by acquired aflbciations acquaints
us with thole motions of tangible bodies, which
depend on their elafticity ; and which we had be-
fore learned by our fenfe of touch.

V. Of Smell and of Tafte.

THE objects of fmell are diflblved in the fluid
atmofphere, and thofe of tafte in the faliva, or other
aqueous fluid, for the better diffufing them on their
refpective organs, which feem to be" ftimulated into
animal motion perhaps by the chemical affinities of
thefe particles, which conftitute the fapidity and
ffclorofity of bodies with the nerves of fenfe, which
perceive them.

Mr. Volta has lately obferved a curious circum-
fiance relative to our fenfe of tafte. If a bit of clean
lead and a bit of clean iilver be feparately applied to
the tongue and palate no tafte is perceived ; but by
applying them in contact in refpect to the parts out
of the mouth, and nearly fo in refpecl to the parts,
which are immediately applied to the tongue and
palate, a faline or acidulous tafte is perceived, as of
a fluid like a ft ream of electricity pafling from one
of them to the other- This new application of the
fenfe of tafte deferves further inveftigation, as it
may acquaint us with new properties of matter.

From the experiments above mentioned of Gal-
vani, Volta, Fowler, and others, it appears, that
a plate of zinc and a plate of filver have greater
effect than lead and filver* If one edge of a plate
of filver about the fize of half a crown-piece be
placed upon the tongue, and one edge of a plate of
zinc about the fame fize beneath the tongue, and

if

SICT. XIV. 6. PRODUCTION OF IDEAS 127

if their oppdfite edges are then brought into con-
tact before the point of the tongue, a tafte is per-
ceived at the moment of their coming into con-
tact ; fecondly, if one of the above plates be put
between the upper iip and the gum of the fore-
teeth, and the other be placed under the tongue,
and their exterior edges be then brought into con-
tact in a darkifh room, a flafli of light is perceived
in the eyes.

Thefe effects I imagine only mew the fenfibility
of our nerves of fenfe to very fmall quantities of
the electric fluid, as it pafles through them ; for
I fuppofe thefe fenfations are occafioned by flight
electric mocks produced in the following manner.
By the experiments publifhed by Mr. Bennet, with
his ingenious doubler of electricity, which is the
greateft difcovery made in that fcience fince the
coated jar, and the eduction of lightning from thd
fkies, it appears that zinc was always found minus,
and filver was always found plus, when both of
them were in their feparate ftate. Hence, when
they are placed in the manner above defcribed, as
foon as their exterior edges come nearly into con-
tact, fo near as to have an extremely thin plate of
air between them, that plate of air becomes charg-
ed in the fame manner as a plate of coated glafs $
and is at the fame inltant difcharged through the
nerves of tafte or of fight, and gives the fenfations,
as above defcribed, of light or of faporofity ; and
only mews the great fenfibility of thefe organs of
fenfe to the itimulus of the electric fluid in fudden-
ly pafling through them.,

VI. Of the Senfe of Heat.

THERE are many experiments in chemical writ-
ers, that evince the exiftence of heat as a fluid
element, which covers and pervades all bodies, and

is

n$ PRODUCTION OF IDEAS. SECT. XIV. 6.

is attracted by the folations of fome of them, and
is detruded from the combination of others. Thus
from the combinations of metals with acids, and
from thofe combinations of animal fluids, which
are termed fecretions, this fluid matter of heat is
given out amongft the neighbouring bodies ; and
in the folutions of falts in water, or of water in
air, it is abforbed from the bodies, that furro\$nd
them ; whilft in its facility in paffing through me-
tallic bodies, and its difficulty in pervading refins
and glafs, it refembles the properties of the electric
aura ; and is like that excited by friction, and
feems like that to gravitate amongft other bodies
in its uncornbined (late, and to find its equili-
brium.

There is no circum fiance of more confequence
in the animal economy than a due proportion of
this fluid of heat -, for the digeftion of our nutri-
ment in the ftomach and bowels, and the proper
qualities of all our fecreted fluids, . as they are pro-
duced or prepared partly by animal and partly by
chemical proceifes, depend much oh the quantity
of heat ; the excefs of which, or its deficiency, alike
gives us pain, and induces us to avoid the circum-
ftances that occafion them. And in this the per-r
ception of heat effentially differs from the percep*
tions of the f enfe of touch, as we receive pain from
too great preffure of folid bodies, but none from
the abfence of it. It is hence probable, that nature
has provided us with a fet of nerves for the percep*
tion of this fluid, which anatorniits have not yet
attended to.

There may be fome difficulty in the proof of this
afiertion ; if we look at a hot fire, we experience
no pain of the optic nerve, though the heat along
with the light muft be concentrated upon it. Nor
does warm water or warm oil poured into the ear
give pain to the organ of hearing j and hence as

thefe

SECT. XIV. 6. PRODUCTION OF IDEAS. 129

thefe organs of fenfe do not perceive fmall exceffes
or deficiencies of heat ; and as heat has no greater
analogy to the folidity or to the figures of bodies,
than it has to their colours or vibrations ; there
feems no fufikient reafon for our afcribing the per-
ception of heat and cold to the fenfe of touch ; to
which it has generally been attributed, either be-
caufe it is diffused beneath the whole fkin like
the fenfe of touch, or owing to the inaccuracy of
our obfervations, or the defect of our languages.

There is another circumftance would induce us
to believe, that the perceptions of heat and cold
do not belong to the organ of touch ; fi.nce the
teeth, which are the leaft adapted for the percep-
tions of folidity or figure, are the mod fen Able to
heat or cold ; whence we are forewarned from
fwallowing thofe materials, whofe degree of cold-
nefs or of heat would injure our ftomachs.

The following is an extract from a letter of Dr.
R. W. Darwin, of Shrewfbury, when he was a
fludent at Edinburgh. " I made an experiment
yefterday in our hofpital, which much favours
your opinion, that the fenfation of heat and of
touch depend on different fets of nerves. A man
who had lately recovered from a fever, and was
Hill weak, was feized with violent cramps in his
legs and feet ; which were removed by opiates,
except that one of his feet remained infeniible.
Mr. Ewart pricked him with a pin in five or fix
places, and the patient declared he did not feel it
in the leaft, nor was he (eniible of a very (mart
pinch. 1 then held a red-hot poker at fome dif-
tance, and brought it gradually nearer till it came
within thr< e inches, when he afierted that he felt
it quite diftindly. I fuppofe fome violent irrita-
tion on the nerves of touch had caufed the cramps,
and had left them paralytic ; while the nerves of
heat, having fuffered no increased ftimulus, re-
tained their irritability."

Add

i> PRODUCTION OF IDEAS. SECT. XIV. 7,

Add to this, that the lungs, though eafily ftimiu
lated into inflammation , are not fenfible to heat.
See Clafs, III. i. i. ic,

VII. Of the Senfe of Extenfion.

THE organ of touch is properly the fenfe of pref-
fure, but the mufcular fibres themfelves conftitute
the organ of fenfe, that feels extenfion. The fenfe
of preffure is always attended with the ideas of the
figure and folidity of the object, neither of which
accompany our perception of extenfion. The
whole fet of mufcles, whether they are hollow
ones, as the heart, arteries, and inteftines, or lon-
gitudinal ones attached to bones, contract them-
ielves, whenever they are ftimulated by forcible
elongation ; and it is obfervable, that the white
mufcles, which conftitute the arterial fyftem, feem
to be excited into contraction from no other kinds
of ftimulus, according to .the experiments of Haller,
And hence the violent pain in fome inflammations,
as in the paronychia, obtains immediate relief by
cutting the membrane, that was ftretched by the
tumour of the fubjacent parts.

Hence the whole mufcular fyftem may be confi-
dered as one organ of fenfe, and the various atti-
tudes of the body, as ideas belonging to this organ,
of many of which we are hourly confcious, while
many others, like the irritative ideas of the other
fenfes, are performed without our attention.

When the mufcles of the heart ceafe to aft, the
refluent blood again diftends or elongates them ;
and thus irritated they contract as before. The
fame happens to the arterial fyftem, and I fuppofe
to the capillaries/ inteftines, and various glands of
the body,

When the quantity of urine, or of excrement,
<Jiften<4s the bladder, or rectum, thofe parts con-

SECT. XIV. 7. PRODUCTION OF IDEAS. 131

tract, and exclude their contents, and many other
ynufcles by affociation act along with them ; but if
thefe evacuations are not foon complied with, pain
is produced by a little further extenfion of the
mufcular fibres : a fimilar pain is caufed in the
ynufcles, when a limb is much extended for the
reduction of diflocated bones ; and in the punifli-
ment of the rack : and in the painful cramps of the
calf of the leg, or of other mufcles, for a greater
degree of contraction of a mufcle, than the move-
ment of the two bones, to which its ends are af-
fixed, will admit of, muft give fimilar pain to
that, which is produced by extending it beyond
its due length. And the pain from punctures or
incifions arifes from the diftention of the fibres, as
the knife pafles through them ; for it nearly ceafes
as foon as the divifion is completed.

All thefe motions of the mufcles, that are thus'
paturally excited by the flimulus of diftending bo-
dies, are alfo liable to be called into ftrong action
by their catenation, with the irritations or fenfa-
tions produced by the momentum of the progref-
five particles of blood in the arteries, as in inflam*
matory fevers, or by acrid fubftances on other fen-
fible organs, as in the ftrangury, or tenefmus, or
cholera.

We mall conclude this account of the fenfe of
extenfion by obferving, that the want of its object
is attended with a difagreeable fenfation, as well as
the excefs of it. In thofe hollow mufcles, which
have been accuftomed to it, this difagreeable fenfa-
tion is called faintnefs, emptinefs, and finking;
^nd, when it arifes to a certain degree, is attended
with fyncope, or a total quiefcence of all motions,
but the internal irritative ones, as happens from
fudden lofs of blood, or in the operation of tapping
in the dropfy.

VIII,

132 PRODUCTION OF IDEAS. SECT. XIV. 8.

VIII. Of the Appetites of Hunger -, Thirft, Heat, Ex-
tenfion, the 'want of frejh Air^ animal Love, and
the Suckling of Children.

HUNGER is mod probably perceived by thofe
numerous ramifications of nerves that are feen
about the upper opening of the ftomach ; and
thirft by the nerves about the fauces, and the top
of the gula. The ideas of thefe fenfes are few in
the generality of mankind, but are more nume-
rous in thofe, who by difeafe, or indulgence, de-
fire particular kinds of foods or liquids.

A fenfe of heat has already been fpoken of, which
may with propriety be called an appetite, as we
painfully deGre it, when it is deficient in quan-
tity. j?v

The fenfe of extenfion may be ranked amongft
thefe appetites, fince the deficiency of its- object
gives dif agreeable fenfation ; when this happens in
the arterial fyftem, it is called faintnefs, and feems
to bear fome analogy to hunger and to cold ;
which like it are attended with emptinefs of a
part of the vafcular fyftem.

The fenfe of want of frefh air has not been at-
tended to, but is as diftinct as the others, and the
firft perhaps that we experience after our nativity ;
from the want of the object of this fenfe many dif-
eafes are produced, as the jail-fever, plague, and
other epidemic maladies. Animal love is another
appetite, which occurs later in life, and the fe-
males of lactiferous animals have another natural
inlet of pleafure or pain from the fuckling their
offspring. The want of which either owing to
the death of their progeny, or to the fafliion of
their country, has been fatal to many of the fex.
The males have alfo pectoral glands, which are fre-
quently turgid with a thin milk at their nativity,
and are furniihed with nipples, which erect on ti-

< tillation

SECT. XIV. 3. PRODUCTION OF IDEAS. 133

tiilation like thofc of the female ; but which feem
now to be of no further ufe, owing perhaps to
f'ome change which thefe animals have undergone
in the gradual pro^refiicn of the formation of the
earth, and of all that it inhabit.

Thefe feven laft mentioned fenfes may properly
be termed appetites, as they differ from thofe of
touch, light, hearing, tafte, and fmell, in this ref-
pecl ; that they are affected with pain as well by the
defect of their objects as by the excefs of them,
which is not fo in the latter. Thus cold and hunger
give us pain, as well as an excefs of heat or fatiety;
but it is not fo with darknefs and file nee.

IX. Before we conclude this Sedion on the or-
gans of fenfe, we muft obferve, that, as far as we
know, there are many more fenfes, than have been
here mentioned, as every gland feems to be influ-
enced to feparate from the blood, or toabforb from
the cavities of the body, or from the atmofphere,
its appropriated fluid, by the fHmulus of that fluid
on the living gland ; and not by mechanical capil-
lary abforption, nor by chemical affinity. Hence it
appears, that each of thefe glands mull: have a pe-
culiar organ to perceive thefe irritations, but as
thefe irritations are not fucceeded byfenfation, they
have not acquired the names of fenfes.

However when thefe glands are excited into mo-
tions ftronger than ufual, either by the acrimony
of their fluids, or by their own irritability being
much increafed, then the fenfation of pain is pro-
duced in them as in all the other fenfes of the body ;
and thefe pains are all of different kinds, and hence
the glands at this time really become each a different
organ of fenfe, though thefe different kinds of pain
have acquired no names.

Thus a great excefs of light does not give the
idea of light but of pain ; as in forcibly opening
the eye when it is much inflamed. The great ex-
qefs of preffure or diftention, as when the point of

a pin

134 PRODUCTION OF IDEAS. SECT. XIV. 8.

a pin is preffed upon our fkin, produces pain, (and
when this pain of the fenfe of diftention is "ilighter,
it is termed itching, or tickling), without any idea
of folidity or of figure ; an excefs of heat produ-
ces fmarting, of cold another kind of pain ; it is
probable by this fenfe of heat the pain produced by
cauftic bodies is perceived, and of electricity, as
all thefe are fluids, that permeate, diflend, or de-
compofe the parts that feel them.

SECT,

SECT. XV. f. CLASSES OF IDEAS.

SECT. XV,

OF THE CLASSES OF IDEAS.

I. i. Ideas received in tribes. 2. We combine them
further, or abftracJ from thefe tribes. 3. Complex
ideas. 4. Compounded ideas. Simple ideas, modes ,
fubftances, relations, general ideas. 6. Ideas of re-
flexion. 7. Memory and imagination imperfecJly de-
Jined. Ideal prefence. Memorandum-rings, II. I .
Irritative ideas. Perception. 2, Senfitive ideas,
imagination. 3. Voluntary ideas, recolleftion* 4.
AJfociated ideas, fuggejiion. III. i . Dejinitions of
perception, memory, i. Reafoning, judgment, doubt-
ing, diftinguijhing, comparing. 3. Invention. 4.
Confcioufnefs. 5. Identity. 6. Lapfe of time. J.
Free-will.

I. AS the conftituent elements of the material
world are only perceptible to our organs of fenfe
in a ftate of combination ; it follows, that the ideas
or fenfual motions excited by them, are never re-
ceived fingly, but ever with a greater or lefs degree
of combination. So the colours of bodies or their
hardneires occur with their figures : every fmell
and tatte has its degree of pungency as well as its
peculiar flavour : and each note in mufic is com-
bined with the tone of fome inftrument. It ap-
pears from -hence, that we can be fenfible of a
number of ideas at the fame time, fuch as the
whitenefs, hardneis, and coldnefs, of a mow-ball,

and

136 CLASSES OF IDEAS. SECT. XV. i.

and can experience at the fame time many irritative
ideas of furrounding bodies, which we do not at-
tend to, as mentioned in Section VII. 3. 2. But
thofe ideas which belong1 to the fame fenfe, feem to
be more ealliy combined into fynchronous tribes,
than thofe which were jiot received by the fame
fenfe, as we. can more eafily think of the whitenefs
and figure of a lump of fugar at the fame time,
than the whitenefs and fweetnefs of it.

2. As thefe ideas, or fenfual motions, are thus
excited with greater or lefs degrees of combination;
fo we have a power, when we repeat them either
by our volition or fenfation, to increafe or diminifh
this degree of combination, that is, to form com-
pounded ideas from thofe, which were more fim-
ple ; and abftract ones from thofe, which, were
more complex, when they were firft excited ; that
is, we can repeat a part or the whole of thofe fen-
fual motions, which did conflitute our ideas of
perception ; and the repetition of which now con-
flitutes our ideas of recollection, or of imagina-
tion.

3. Thofe ideas, which we repeat without change
of the quantity of that combination, with which
we firft received them, are called complex ideas, as
when you recollect Weftminfter Abbey, or the pla-
net Saturn : but it muft be obferved, that thefe
complex ideas, thus re-excited by volition, fenfa-
tion, or aflbciation, are feldom perfect copies of
their correfpondent perceptions, except in Our
dreams, where other external objects do not de-
tract our attention.

4. Thofe ideas, which are more complex than
the natural objects that firit excited them, have
been called compounded ideas, as when we think
of a fphinx, or griffin,

5, And

SECT. XV. i. CLASSES OF IDEAS. 137

5. And thofe that are lefs complex than the cor-
refpondent natural objects, have been termed al>
ftracted ideas ; thus fweetnefs, and whitenefs, and
folidity, are received at the fame time from a lump
of fugar, yet I can recollect any of thefe qualities
without thinking of the others, that were excited
along with them.

When ideas are fo far abftracted as in the above
example, they have been termed fimple by the
writers of metaphyfics, and^feem indeed to be more
complete repetitions of the ideas or fenfual motions,
originally excited by external objects.

Other clailes o£. thefe ideas, where the abftrac-
tion has not been fo great, have been termed, by
Mr. Locke, modes, fubftances, and relations, but
they feem only to differ in their degree of abftrac-
tion from the complex ideas that were at firft ex>
cited ; for as thefe complex or natural ideas are
themfelves imperfect copies of their correfpondent
perceptions, fo thefe abftract or general ideas are
only ftiil more imperfect copies of the fame per-
ceptions. Thus when I have feen an object but
once, as a rhinoceros, my abftract idea of this ani-
mal is the fame as my complex one. I may think
more or lefs diftin&ly of a rhinoceros, but it is the
very rhinoceros that I faw, or fome part or proper-
ty of him, which recurs to my mind.

But when any clafs of complex obje&s becomes
the fubject of converfation, of which I have feen
many individuals, as a caftle or an army, fome
property or circumftance belonging to it is peculi-
arly alluded to ; and then I feel in my own mind,
that my abftracfc idea of this complex object is only
an idea of that part, property, or attitude of it,
that employs the prefent converfation, and varies
with every fentence that is fpoken concerning it.
So if any ooe fhould fay, " one may fit upon a

horfe

i3» CLASSES OF IDEAS. SECT. JCV. t.

horfe fafer than on a camel," my abftract idea of
the two animals includes only an outline of the
level back of the one, and the gibbofity on the
back of the other. What noife is that in the
ftreet ? — Some horfes. trotting over the pavement.
Here my idea of the horfes includes principally
the fhape and motion of their legs. So alfo
the abftract ideas of goodnefs and courage are
Hill more imperfect reprefentations of the ob-
jects they were received from 5 for here we ab-
ilract the material parts, and recollect only the
qualities.

Thus we abflract fo much from fome of our*
complex ideas, that at length it becomes difficult
to determine of what perception they partake ;
and in many inftances out idea feems to be no other
than of the found or letters of the word, that
Hands for the colle&ive tribe, of which we are
faid to have an abftra&ed idea, as noun, verb, chi-
inaera, apparition*

6. Ideas have been divided into thofe of percep-
tion and thofe of reflection, but as whatever is
perceived muft be external to the organ that
perceives it, all our ideas muft originally be ideas
of perception.

7. Others have divided our ideas into thofe of
memory, and thofe of imagination ; they have
faid that a recollection of ideas in the order they
were received conftitutes memory, and without that
order imagination ; but all the ideas of imagina-
tion, excepting the few that are termed -fimple
ideas, are parts of trains or tribes in the order
they were received ; as if I think of a fphinx,
or a griffin, the fair face, bofom, wings, claws,
tail, are all complex ideas in the order they were
received : and it behoves the writers, who ad-

' here

SECT. XV. CLASSES OF IDEAS. 139

here to this definition, to determine, how^ fmall
the trains muft be, that fhall be called imagi-
nation ; and how great thofe, that fhall be called
memory,

Others have thought that the ideas of memory
have a greater vivacity than thofe of imagination :
but the^ideas of a perfon in fleep, or in a waking
reverie, where the trains connected with fenfation
are uninterrupted, are more vivid and diftincl: than
thofe of memory, fo that they cannot be diflin-
guifhed by this criterion.

The very ingenious author of the Elements of
Criticifm has defcribed what he conceives to be a
fpecies of memory, and calls it ideal prefence ; but
the inftances he produces are the reveries of fenfa-
tion, and are therefore in truth connections of the
imagination, though they are recalled in the order
they were received.

The ideas connected by aflbciation are in com-
mon difcourfe attributed to memory, as we talk
of memorandum. rings, and tie a knot on our
handkerchiefs to bring fomething into our minds
at a diftance of time. And a fchool-boy, who
can repeat a thoufand unmeaning lines in Lilly's
Grammar, is faid to have a good memory.
But thefe have been already fhewn to belong
to the clafs of aflbciation j and are termed ideas
of fuggeftion.

II. Laftly, the method already explained of claf-
ling ideas into thofe excited by irritation, fenfation,
volition, or aflbciation, we hope will be found more
convenient both for explaining the operations of
the mind, and for comparing them with thofe of
the body ; and for the illuflration and the cure of
the difeafes of both, and which we fliall here reca-
pitulate.

VOL. I. L i. Irritative

14® CLASSES OF IDEAS. SECT. XV. 3;

1. Irritative ideas are thofe, which are preceded
by irritation, which is excited by objects external
to the organs of fenfe : as the idea of that tree,
which either I attend to, or which Khun in walking
near it without attention. In the former cafe it is
termed perception, in the latter it is termed limply
an irritative idea.

2. Senfitive ideas are thofe, which are preceded
by the fenfation of pleafure or pain ; as the ideas,
which conftitute our dreams or reveries, this is
called imagination.

3. Voluntary ideas are thofe, which are preceded
by voluntary exertion, as when I repeat the alpha-
bet backwards : this is called recollection.

4. Aflbciate ideas are thofe, which are preceded
by other ideas or mufcular motions, as when we
think over or repeat the alphabet by rote in its
lifual order ; or fing a tune we are accuftomed to 5
this is called fuggeftion.

III. i. Perceptions fignify thofe ideas, which
are preceded by irritation and fucceeded by
the fenfation of pleafure or pain, for whatever
excites our attention interefts us ; that is, it
is accompanied with pleafure or pain ; however
flight may be the degree or quantity of either of
them.

The word memory includes two clafTes of ideas,
either thofe which are preceded by voluntary ex-
ertion, or thofe which are fuggefted by their aflb-
ciations with other ideas.

2. Reafoning is that operation of the fenforium,
by which we excite two or many tribes of ideas ;
and then re-excite the ideas, in which they differ,
or correfpond. If we determine this difference, it
is called judgment; if we in vain endeavour to de-
termine it, it is called doubting.

IP

SECT. XV. 3. CLASSES OF IDEAS.

If we re-excite the ideas, in which they differ,
it is called diftinguifhing. If we re-excite thofe in
which they correfpond, it is called comparing.

3. Invention is an operation of the fenforium,
by which we voluntarily continue to excite one
train of ideas, fuppofe the defign of railing water
by a machine ; and at the fame time attend to all
other ideas, which are connected with this by
every kind of catenation ; and combine or fepa-
rate them voluntarily for the purpofe of obtaining
fome end.

For we can create nothing new, we can only
combine or feparate the ideas, which we have al-
ready received by our perceptions : thus if I wifli
to reprefent a monfler, I call to my mind the ideas
of every thing difagreeable and horrible, and com-
bine the naftinefs and gluttony of a hog, the ftupi^
dity and obftinacy of an afs, with the fur and awk-
wardnefs of a bear, and call the new combination.
Caliban. Yet fuch a monfter may exift in nature,
as all his attributes are parts of nature. So when
I wifti to reprefent every thing, that is excellent,
and amiable ; when I combine benevolence with
cheerfulnefs, wifdom, knowledge, tafte, wit, beau-
ty of perfon, and elegance of manners, and aflb-
ciate them in one lady as a pattern to the world, it
is called invention ; yet fuch a perfon may exift,—-
fuch a perfon does exift ! — It is • < • . ,

who is as much a monfter as Caliban.

4. In refpecl to confcioufnefs, we are only con-
fcious of our exiftence, when we think about it ;
as we only perceive the lapfe of time, when we at-
tend to it ; when we are bufied about other objects,
neither the lapfe of time nor the confcioufnefs of
our own exiftence can occupy our attention. Hence,
when we think of our own exiftence, we only ex-

L 2 cite

j 14* CLASSES OF IDEAS. SECT. XV. 3.

cite abftracted or reflex ideas (as they are termed),
of our principal pleafures or pains, of our defires
or avernons, or of the figure, folidity, colour, or
other properties of our bodies, and call that aft of
the .fenforium a confcioufnefs of our exiftence.
Some philofophers, I believe it is Des Cartes, has
faid, " I think, therefore I exift." But this is not
right reafoning, becaufe thinking is a mode of ex-
iftence ; and it is thence only faying, " I exift,
therefore I exift." For there are three modes
of exiftence, or in the language of grammarians,
three kinds of verbs. Firft, limply I am, or
exift. Secondly, I am acting, or exift in a ftate
of activity, as I move. Thirdly, I am fuffering,
or «xift in a ftate of being acted upon, as I am
moved. The when, and the where, as applica-
ble to this exiftence, depends on the fucceflive
motions of our own or of other bodies ; and
on their refpective fituations, as fpoken of Seel.
XIV. 2. 5.

5. Our identity is known by our acquired ha-
bits or catenated trains of ideas and mufcular
motions ; and perhaps, when we compare infan-
cy with old age, in thofe alone can our identity
be fuppofed to exift. For what elfe is there of
fimilitude between the firft fpeck of living en-
tity and the mature man? — every deduction of
reafoning, every fentiment or paffion, with every
fibre of the corporeal part of our fyftem, has
been fubject almoft to annual mutation ; while
fome catenations alone of our ideas and mufcular
actions have continued in part unchanged.

By the facility, with which we can in our waking
hours voluntarily produce certain iucceffive trains
of ideas, we know by experience, that we have
before reproduced them j that is, we are confcious

of

SECT. XV. 3. CLASSES OF IDEAS. 143

of a time of our exiftence previous to the prefent
time ; that is, of our identity now and heretofore.
It is thefe habits of action, thefe catenations of
ideas and mufcular motions, which begin with life,
and only terminate with it ; and which we can in
fome meafure deliver to ourpoflerity j as explained
in Sea. XXXIX.

6. When the progreflive motions of external
bodies make a part of our prefent catenation of ideas,
we attend to the lapfe of time ; which appears the
longer, the more frequently we thus attend to it ;
as when we expect fomething at a certain hour,
which much interefts us, whether it be an agreeable
or difagreeable event ; or when we count the paffing
feconds on a ftop-watch.

When an idea of our own perfon, or a reflex
idea of our pleafures and pains, defires and a-
verfions, makes a part of this catenation, it is
termed confcioufnefs ; and if this idea of con-
fcioufnefs makes a part of a catenation, which
we excite by recollection, and know by the fa-
cility with which we excite it, that we have be-
fore experienced it, it is called identity, as ex-
plained above.

7. In refpecl: to freewill, it is certain, that we
cannot will to think of a new train of ideas, with-
out previoufly thinking of the firft link of it ; as I
cannot will to think of a black fwan, without pre-
vioufly thinking of a black fwan. But if I now
think of a tail, I can voluntary recollecl all animals
which have tails ; my will is fo far free, that I can
purfue the ideas linked to this idea of tail, as far
as my knowledge of the fubjecl: extends ; but to
will without motive is to will without defire or
averfion ; which is as abfurd as to feel without
pleafure or pain : they are both folecifms in the

terms

CLASSES OF IDE AS. SECT. XV. 3.

terms. So far are we governed by the catenations
of motions, which affect both the body and the
mind of man, and which begin without our irri-
tability, and end with it,

SECT.

SECT. XVI. i, OF INSTINCT. 145

SECT. XVI.

OF INSTINCT.

HAUD EQU1DEM CREDO, QUIA SIT DIVINITUS ILLIS
INGENIUM, AUT RERUM FATO PRUDENTIA MAJOR*

VIRG. GEORG. L. I. 415.

I. Inftinclive aftions defined. Of connate pajfions. II.
Of the fenfations and motions of the fetus in the womb.
III. Some animals are more perfectly formed than
others before nativity. Of learning to walk. IV. Of
ihe fw allowing, breathing, fucking pecking, and
lapping of young animals. V. Of the fenfe of f me II,
and its ufes to animals. Why cats do not eat their kit-
tens. VI. Of the accuracy of fight in mankind, and
their fenfe of beauty. Of the fenfe of touch in ele-
phants, monkies, beavers, men. VII. Of natural
language. VIII. The origin of natural language;
i. the language of fear ; 2. of grief ; 3. of tender
pleafure ; 4. of ferene pleafure ; 5. of 'anger : 6. of
attention. IX. Artificial language of turkies^ hens9
ducklings, wagtails, cuckoos, rabbits, dogs^ and night-
ingales. X. Of mufic \ . of tooth -edge ; of a good ear;
of architecture. XI. Of acquired knowledge ; of
foxes ) rooks i fieldfares, lapwings, dags, cats, horfes9
crows 9 and pelicans. XII. Of birds of paffage, dor~
mice, fnakes, bats, f wallows, quails* ringdoves, Jiare,
chaffinch, hoopoe, chatterer, hawfinch, crofsbtll, rails

and

M OF INSTINCT. SECT. XVI. i.

and cranes. XIII. Of birds nefts ; of the cuckoo;
of /wallows nefls ; of the taylor bird. XIV. Of the
old foldier ; of haddocks, cods, and dogfjh ; of the
remora ; of crabs, herrings, and falmon. XV. Of
fpiders, caterpillars, ants, and the ichneumon. XVI.
i. Of locufts, gnats; 2. bees; 3. dormice ', flies ,
worms, ants, and wafps. XVII. Of the faculty that
dlftlnguljhes man from the brutes.

I. ALL thofe internal motions of animal bodies,
which contribute to digeft their aliment, produce
their fecretions, repair their injuries, or increafe
their growth, are performed without our atten-
tion or con fcioufn el's, They exift as well in our
fleep, as in our waking hours, as well in the foetus
during the time of geftation, as in the infant after
nativity, and proceed with equal regularity in the
vegetable as in the animal fyftem. Thefe motions
have been Ihewn in a former part of this work to
depend on the irritations of peculiar fluids, and as
they have never been claffed amongfl the inftinctive
actions of animals, are precluded from our prefent
difquifition.

But all thofe actions of men or animals, that are
attended with confcioufnefs, and feem neither to
have been directed by their appetites, taught by
their experience, nor deduced from obfervation or
tradition, have been referred to the power of in-
fHnct.. And this power has been explained to be a
divine fomething, a kind of infpiration ; whilft the
poor animal, that poflefTes it, has been thought lit-
tle better than a machine !

The irkfo?nenefs, that attends a continued attitude
of the body, or the pains, that we receive from
heat, cold, hunger, or other injurious circumf-

tances,

SECT. XVI. 2. OF INSTINCT.

tances, excite us to general locomotion : and our fenfes
are fo formed and conftituted by the hand of na-
ture, that certain objects prefent us with pleafure,
others with pain, and we are induced to approach
and embrace thefe, to avoid and abhor thofe, as
fuch fenfations direcl us.

Thus the palates of fome animals are gratefully
affected by the maftication of fruits, others of
grains, and others of flefli ; and they are thence
infligated to attain, and to confume thofe mate-
rials ; and are furnifhed with powers of mufcular
motion, and of digeftion proper for fuch pur.
pofes.

Thefe fenfations and dejtres conftitute a part of
our fyftem, as our mufcles and bones conftitute ano-
ther part : and hence they may alike be termed
natural or connate ; but neither of them can pro-
perly be termed inftinclive : as the word inftinct in
its ufual acceptation refers only to the aftions of
animals, as above explained ; the origin of thefe
aftions is the fubjecl of our prefent enquiry.

The reader is intreated carefully to attend to
this definition of inftinftive aftions, left by ufing the
word inftincl without adjoining any accurate idea
to it, he may not only include the natural defires
of love and hunger, and the natural fenfations of
pain or pleafure, but the figure and contexture of
the body, and the faculty of reafon itfelf under this
general term.

II. We experience fome fenfations, and perform
fome actions before our nativity ; the fenfations of
cold and warmth, agitation and reft, fulnefs arid
inanition, are inftances of the former ; and the
repeated ftruggles of the limbs of the foetus, which
begin about the middle of geftation, and thofe

motions

148 OF INSTINCT. SECT. XVI. a.

motions by which it frequently wraps the umbilical
chord around its neck or body, and even fome-
times ties it on a knot ; are inftances of the latter.
SmeJiie's Midwifery, (Vol. I. p. 182.)

By a due attention to thefe circumftances many of
the actions of young animals, which at firft fight
feemed only referable to an inexplicable in (line!:,
will appear to have been acquired like all other ani-
mal actions, that are attended with confcioufnefs,
by the repeated efforts of our mufcles under the conduft
of our fenfations or dejires.

The chick in the fheli begins to move its feet and
legs on the fixth day of incubation (Mattrecian,
p. 138) ; or on the feventh day, (Langley); after-
wards they are feen to move themfelves gently in
the liquid that furrounds them, and to open and
fhut their mouths, (Harvei, de Generat. p. 62, and
197. Form de Poulet. ii. p. 129). Puppies before
the membranes are broken, that involve them, are
feen to move themfelves, to put out their tongues,
and to open and fhut their mouths, (Harvey, Gip-
foo, Riolan, HallerJ. And calves lick themfelves
and fwallow many of their hairs before their nati-
vity: which however puppies do not, (Swam-
merden, p. 319. Flemyng Phil. Tranf. Ann. 1755.
42.) And towards the end of geftation, the foetus
of all animals are proved to drink part of the li-
quid in which they fvvim, (Haller. Phyliol. T. 8.
204). The white of egg is found in the mouth
and gizzard of the chick, and is nearly or quite
confumed before it is hatched, (Harvie de Generat.
58). And the liquor amnii is found in the mouth
and ftomach of the human foetus, and of calves ;
and how elfe fhould that excrement be produced
in the inteftines of all animals, which is voided in

great

SHCT. XVI. 3. OF INSTINCT. 149

great quantity foon after their birth ; (Gipfon,
Med. Mays, Edinb. V. i. 13. Halleri Phyfiolog.
T. 3. p. 318. and T. 8). In the ftomach of a calf
the quantity of this liquid amounted to about
three pints, and the hairs amongft it were of the
fame colour with thofe on its ikin, (Blafii Anat.
Animal, p. m. 122). Thefe facls are attefted by
many other writers of credit, befides thofe above
mentioned.

111. It has been deemed a furprifing inftance of
inftincl:, that calves and chickens fhould be able
to walk by a few efforts almoft immediately after
their nativity : whilft the human infant in thofe
countries where he is not incumbered with clothes,
as in India, is five or fix months, and in our cli-
mate almoft a twelvemonth, before he can fafely
Hand upon his feet.

The ftruggles of all animals in the womb muft
refemble their mode of fwimming, as by this kind
of motion they can beft change their attitude in
water. But the fwimming of the calf and chicken
refembles their manner of walking, which they
have thus in part acquired before their nativity,
and hence accompliih it afterwards with very few
efforts, whilft the fwimming of the human crea-
ture refembles that of the frog, and totally differs
from his mode of walking.

There is another circumftance to be attended to
in this affair, that not only the growth of thofe
peculiar parts of animals, which are firft wanted
to fecure their fubfiftence, are in general furtheft
advanced before their nativity : but fome animals
come into the world more completely formed
throughout their whole fyftem than others : and
are thence much forwarder in all their habits of

motion*

150 OF INSTINCT. SICT. XVI. 4*

motion. Thus the colt, and the lamb, are much
more perfect animals than the blind puppy, and the
naked rabbit ; and the chick of the pheafant, and
the partridge, has more perfect plumage, and more
perfect eyes, as well as greater aptitude to loco-
iriotion, than the callow neftlings of the dove, and
of the wren. The parents of the former only find
it neceffary to (hew them their food, and to teach
them to take it up ; whilft thofe of the latter are
obliged for many days to obtrude it into their gap-
ing mouths.

IV. From the facts mentioned in No. a. of this
Section, it is evinced that the foetus learns to fwal-
iow before its nativity ; for it is feen to open its
mouth, and its ftomach is found filled with the
liquid that furrounds it. It opens its mouth,
either infligated by hunger, or by the irkfomenefs
of a continued attitude of the mufcles of its face ;
the liquor amnii, in which it fwims, is agreeable
to its palate, as it coniifts of a nourifhing material,
(Haller Phyf. T. 8. p. 204;. It is tempted to ex-
perlence its tafte further in the mouth, and by a few
efforts learns to fwallow, in the fame manner as we
learn all other animal actions, which are attended
with confcioufnefs, by the repeated efforts of our
mufcles under the condutt of our fenfatlons or voli-
tions.

The infpiration of air into the lungs is fo totally
different from that of fwallowing a fluid in which
\ve are immerfed, that it cannot be acquired be-
fore oar nativity. But at this time, when the
circulation of the blood is no longer continued
through the placenta, that fuffocating fenfation,
which we feel about the precordia, when we are
in want of frefli air, difagreeably affects the infant :

and

SECT. XVI. 4. OF INSTINCT. 151

and all the mufcles of the body are excited into
action to relieve this oppreflion ; thofe of the bread,
ribs, and diaphragm are found to anfwer this pur-
pofe, and thus refpiration is difcovered, and is
continued throughout our lives, as often as the
oppreflion begins to recur. Many infants, both
of the human creature, and of quadrupeds, ftrug-
gle for a minute after they are born before they
begin to breathe, (Haller Phyf. T. 8. p. 400. ib.
pt. 2. p. i). Mr. Buffon thinks the action of the
dry air upon the nerves of fmell of new-born ani-
mals, by producing an endeavour to fneeze, may
contribute to induce this firft infpiration, and that
the rarefaction of the air by the warmth of the
lungs contributes to induce expiration, (Hid. Nat.
Tom. 4. p. 174). Which latter it may effect by
producing a difagreeable ienfation by its delay, and
a confequent effort to relieve it. Many children
fneeze before they refpire, but not all, as far as I
have obferved, or can learn from others..

At length, by the direction of its fenfe of fmell,
or by the officious care of its mother, the young
animal approaches the odoriferous rill of its future
nourifhment, already experienced to fwallow. But
in the act of fwallowing, it is neceflary nearly to
clofe the mouth, whether the creature be immerfed
in the fluid it is about to drink, or not : hence,
when the child firft attempts to luck, it does not
ilightly comprefs the nipple between its lips, and
fuck as an adult perfon would do, by abforbing the
milk ; but it takes the whole nipple into its mouth
for this purpoie, compreffes it between its gums,
and thus repeatedly chewing (as it were) the nip-
ple, prefTes out the milk ; exactly in the fame manner
as it is drawn from the teats of cows by the hands

of

152 OF INSTINCT. SECT. XVI. ^

of the milkmaid. The celebrated Harvey obferves,
that the foetus in the womb muft have fucked in a
part of its nourishment, becaufe it knows how to
fuck the minute it is born, as any one may expe-
rience by putting a finger between its lips, and
becaufe in a few days it forgets this art of fucking,
and cannot without fome difficulty again acquire it,
(Exercit. de Gener. Anim. 48). The fame obfer-
vation is made by Hippocrates.

A little further experience teaches the young
animal to fuck by abforption, as well as by com-
preffion ; that is, to open the cheft as in the be-
ginning of refpiration, and thus to rarefy the air
in the mouth, that the preffure of the denfer ex-
ternal atmofphere may contribute to force out the
milk.

The chick yet in the fhell has learnt to drink by
{wallowing a part of the white of the egg for its
food ; but not having experienced how to take up
and fwallow folid feeds, or grains, is either taught
by the folicitous induftry of its mother ; or by
many repeated attempts is enabled at length to
diftinguifli and to fwallow this kind of nutri-
ment.

And puppies, though they know how to fuck
like other animals from their previous experience
in fwallowing, and in refpiration ; yet axe they
long in acquiring the art of lapping with their
tongues, which from the flaccidity of their cheeks,
and length of their mouths, is afterwards a more
convenient way for them to take in water.

V. The fenfes of fmell and tafte in many other
an\mals greatly exceed thofe of mankind, for in
civilized fbciety, as our victuals are generally pre-
pared by others, and are adulterated with fait,

fpice,

SECT. XVI. 5. OF INSTINCT. i 55

fpice, oil, and empyreuma, we do not hefitate
about eating whatever is fet before us, and neglect
to cultivate thefe fenfes : whereas other animals
try every morfel by the fmell, before they take
it into their mouths, and by the tafte before they
fwallow it : and are led not only each to his pro-
per nouriftiment by this organ of fenfe, but it aifo
at a maturer age directs them in the gratification
of their appetite of love. Which may be fur-
ther underftood by confidering the fympathies of
thefe parts defcribed in Clafs IV. 2. 1.7. While
the human animal is directed to the object of
his love by his fenfe of beauty, as mentioned in
No. VI. of this Section. Thus Virgil, Georg. III.
250.

Nonne vides, uttota tremor pertentat equorum
Corpora, fi tantum notas odor attulit auras ?
Nonne canis nidum veneris nafntus odore
Qaeriut, et erranti trahitur fublambere lingua ?
Refpuit at guftum cupidus, labiifq retra&is
Elevat os, trepidanfque novis impellitur aeftria,
Jnferit et vivum felici vomere femen.
Quam tenui filo caecos adne&it amores
Doda Venus, vitaeque monet renovare favillam !

ANON.

The following curious experiment is related by
Galen. " On directing a goat great with young
I found a brifk embryon, and having detached it
from the matrix, and fnatching it away before it
faw its dam, I brought it into a certain room,
where there were many veflels, fome filled with
wine, others with oil, fome with honey, others
with milk, or fome other liquor ; and in others
were grains and fruits j we firit obferved the young

animal

154 OF INSTINCT. SECT. XVI. fr

animal get upon its feet, and walk ; then it fhook
itfelf, and afterwards fcratched its fide with one of
its feet : then we faw it fmelling to every one of
thefe things, that were fet in the room; and
when it had fmelt to them all, it drank up the
milk." L. 6. de locis. cap. 6.

Parturient quadrupeds, as cats, and bitches, and
fows, are led by their fenfe of fmell to eat the pla-
centa as other common food ; why then do they
not devour their whole progeny, as is reprefented
in an antient emblem of TIME ? This is faid fome-
times to happen in the unnatural ftate in which we
confine fows ; and indeed nature would feem to
have endangered her offspring in this nice circum-
flance ! But at this time the ftimulus of the milk
in the tumid teats of the mother excites her to
look out for, and to defire fome unknown circum-
flance to relieve her. At the fame time the fmell
of the milk attracts the exertions of the young
, animals towards its fource, and thus the delighted
mother difcovers a new appetite, as mentioned in
Seel:. XIV. 3. and her little progeny are led to re-
ceive and to communicate pleafure by this mod
beautiful contrivance.

VI. But though the human fpecies in fome of
their fenfations are much inferior to other animals,
yet the accuracy of the fenfe of touch, .which they
poflefs in fo eminent a degree, gives them a great
Superiority of underftanding ; as is well obferved
by the ingenious Mr. Buffon. The extremities of
other animals terminate in horns, and hoofs, and
claws, very unfit for the fenfation of touch;
whilft the human hand is finely adapted to encom-
pafs its object with this organ of fenfe.
* ' The

SECT. XVI. 6. OF INSTINCT. 171

The elephant is indeed endued with a fine fenfe
of feeling at the extremity of his probofcis, -and
hence has acquired much more accurate ideas of
touch and of light than moft other creatures. The
two following inftances of the fagacity of thefe ani-
mals may entertain the reader, as they^were told me
by fome gentlemen of diftinct obfervatiori, and un-
doubted veracity, who had been much converfant
xvith our eaflern fettlements. Firft, the elephants
that are ufed to carry the baggage of our armies,
are put each under the care of one of the natives
of Indoftan, and whilft himfelf and his wife go into
the woods to collect leaves and branches of trees for
his food, they fix him to the ground by a length of
chain, and frequently leave a child yet unable to
walk, under his protection : and the intelligent ani-
mal not only defends it, but as it creeps about,
when it arrives near the extremity of his chain, he
wraps his trunk gently round its body, and brings
it again into the centre of his circle. Secondly,
the traitor elephants are taught to walk on a narrow
path between two pit-falls, which are covered with
turf, and then to go into the woods, and to feduce
the wild elephants to come that way, who fall into
thefe wells, whilft he pafles fafe between them :
and it is univerfaliy observed, that thofe wild ele-
phants that efcape the fnare, purfue the traitor with
the utinoft vehemence, and if they can overtake
him, which fometimes happens, they always beat
him to death.

The monkey has a hand well enough adapted for
the fenfe of touch, which contributes to his great
facility of imitation ; but in taking- objects with his
hands, as a (lick or an apple, he puts his thumb
on the fame fide of them with his fingers, inflead
of counteracting the preffure of his fingers with it :
from this neglect he is much flower in acquiring the
figures of objects, as he is lefs able to determine

VOL. I. N the

i?2 OF INSTINCT. SECT. XVI. 6.

the di fiances or diameters of their parts, or to dif-
tinguifh their vis inertias from rheir hardnefs. Hel-
vetius adds, that the fhonnefs of his life, his being
fugitive before mankind, and his not inhabiting all
climates, combine to prevent his improvement.
(De PEfprif. T. i. p.) There is however at this time
an old monkey (hewn in Exeter Change, London,
who having loft his teeth, when nuts are given tar
him, takes a flone into his hand, and cracks them
with it one by one ; thus ufmg tools to effect his
purpofe like mankind.

The beaver is another animal that makes ufe of
his hands, and if we may credit the reports of tra-
vellers, is poffeiTed of amazing ingenuity. This
however, Mr. Buffon affirms, is only where they
exid in large numbers, and in countries thinly peo-
pled with men ; while in France in their folitary
flate they (hew no uncommon ingenuity.

Indeed all the quadrupeds, that have collar-bones,
(clavicular) ufe their fore- limbs in fome meafure as
we ufe our hands, as the cat, fquirrel, tiger, bear
and lion ; and as they exercife the fenfe of touch
more univerfally than other animals, fo are they
more fagacious in watching and furprifing their
prey. All thofe birds, that ufe their claws for
hands, as the hawk, parrot, and cuckoo, -appear
to be more docile and intelligent ; though the gre-
garious tribes of birds have more acquired know-
ledge.

Now as the image?, that are painted on the retina
of the eye, are no other than figns, which recall to
our imaginations the objects \ve had before exa-
mined by the organ of touch, as is fully demon-
ftratiid by Dr. Berkley, in his treatife on vifion j it
follows that the human creature has greatly more
accurate and diftinct fenfe of vifion than that of any
other animal. Whence as he advances to maturity-
he gradually acquires a fenfe of female beauty,

which

SECT. XVI. 6. OF INSTINCT. i7J

which at this time directs him to the object of his
new paflion.

Sentimental love, as diflinguifhed from the ani-
mal paffion of that name, with which it is frequent-
ly accompanied, confifts in the defire or fenfation
of beholding, embracing, and faluting a beautiful
objeft.

The character iftic of beauty therefore is that it is
the object of love ; and though many other objects
are in common language called beautiful, yet they
are only called fo metaphorically, and ought to be
termed agreeable. A Grecian temple may give us
the pleafurable idea of fublimity, a Gothic temple
may give us the pleafurable idea of Variety, and a
modern houfe the pleafurable idea of utility ; mufic
and poetry may infpire our love by afibciation of
ideas ; but none of thefe, except metaphorically,
can be termed beautiful ; as we have no wifh to
embrace or falute them.

Our perception of beauty confifts in our recogni-
tion by the fenfe of vifion of thofe objects, firft,
which have before infpired our love by the pleafure,
which they have afforded to many of our fenfes : as
to our fenfe of warmth, of touch, of fmell, of tafte,
hunger and thirft ; and, fecondly, which bear any
analogy of form to fuch objects.

When the babe, foon after it is born into this
cold world, is applied to its mother's bofom ; its
fenfe of perceiving warmth is firft agreeably affect-
ed ; next its fenfe of fmell is delighted with the
odour of her milk; then its tafte is gratified by the
flavour of it : afterwards the appetites of hunger
and of thirft afford pleafure by the pofleflion of their
objects, and by the iubfequent digeftion of the ali-
ment; and, laftly, the fenfe of touch is delighted
by the foftnefs and fmoothnefs of the milky foun-
tain, the fource of fuch varietv of happinefs.

N 2 All

174 OF INSTINCT. SECT.XVI.6,

All thefe various kinds of pleafure at length become
aflbciated with the form of the mother's bread;
which the infant embraces with its hands, preffes
with its lips, and watches with its eyes ; and thus
acquires more accurate ideas of the form of its
mother's bofom, than of the odour and flavour or
warmth, which it perceives bv its other fenfes.
And hence at our maturer years, when any object
of vifion is prefented to us, which by its waving
9r fpiral lines bears any fimilitude to the form of
the female bofom, whether it be found in a land-
fcape with foft gradations of rifmg and defcending
furface, or in the forms of fome antique vafes, or
in other works of the pencil or the chiflel, we feel
a general glow of d(elight, which feems to influence
all our fenfes ; and, if the objecl: be not too large,
we experience an attraction to embrace it with our
arms, and to falute it with our lips, as we did in
our early infancy the bofom of our mother. And
thus we find, according to the ingenious idea of
Hogarth, that the waving lines of beauty were ori-
ginally taken from the temple of Venus.

This animal attraction is love; which is a fenfa-
tion, when the object is prefent ; and a defire, when
it is abfent. Which conftitutes-the pureft fource of
human felicity, the cordial drop in the otherwife
vapid cup of life, and which overpays mankind for
the care and labour, which are attached to the pre-
eminence of his fituation above other animals.

It mould have been obferved, that colour as well
as form fometimes enters into our idea of a beauti-
ful object, as a good complexion for inftance, be-
caufe a fine or fair colour is in general a fign of
health, and conveys to us an idea of the warmth of
the object i and a pale countenance on the contrary
gives an idea of its being cold to the touch.

It was before remarked, that young animals ufe
their lips to diftinguifh the forms of things, as well

as

SicT.XVI. 7. OF INSTINCT. i7s

as their fingers, and hence we learn the origin of
our inclination to faiute beautiful objects with our
lips. For a definition of Grace, fee Clafs III. i.

2. 4,

VII. There are two ways by which we become
acquainted with the paiiions of others: fir ft, by
having obferved the effects of them, as of fear or
anger, on our own bodies, v, e know at fight when
others are under the influence of thefe affections.
So when two cocks are preparing to light, each feels
the feathers rife round his own neck, and knows
from the fame fign the difpofition of his adverfary;
and children long before they can fpeak, or under-
ftand the language of their parents, may be fright-
ened by an angry countenance, or foothed by fmiles
and blandiflimcnts.

Secondly, when we put ourfelves into the atti-
tude ihat any paflion naturally occafions, we foon
in fome degree acquire that paffion ; hence when
thofe that icold indulge themfdves in loud oaths,
and violent actions of the arms, they incu.afe their
anger by the mode of exprefling' themlelvts : and
on the contrary the counterfeited f njle of pleafure
in difagreeable company foon brings along with it
a portion of the reality, as is well iliuff rated by Mr.
Burke, (flay on the Sublime and Beautiful.)

This latter method of entering into the paflions
of others is rendered of very extenfive ufe by the
pleafure we take in imitation, which js every day
prefented before our eyes, in the actions of 'chil-
dren, and ind.ed in all the cuftoms and fafliions of
the world. From this our aptitude to imitation,
arifes what is generally underflood by the word
fympathy fo well explained by. Dr. Smith of Glaf-
gow. Thus the appearance of a cheerful counte-
nance gives us pleafure, and oi a melancholy one
makes us iorrowful. .vning and fom<aunes

vomiting are thus propagated by fympathy, and

to i

176 OF INSTINCT. Stcr.XVI.8.

fome people of delicate fibres, at the prefence of a
fpectacle of mifery, have felt pain in the fame parts
of their own bodies, that were difeafed or mangled
in the other. Among ft the writers of antiquity
Ariftotle thought this aptitude to imitation an eflen-
tial property of the human fpecies, and calls man an
imitative animal. T« &<* ^^u^cv.

Thefe then are the natural ligns by which we un-
derftand each other, and on this ilender bafis is built
all human language. For without fome natural figns,
no artificial ones could have been invented or under-
ftood, as is very ingenioufly obferved by Dr. Reid.
(Inquiry into the Human Mind.)

Vill. The origin of this univerfal language is a
fubject of the higheft curioiity, the knowledge of
which has always been thought utterly macceflible.
A part of which we (hall however here attempt.

Light, found, and odours, are unknown to the
foetus in the womb, which, except the few fenfations
and motions already mentioned, fleeps away its time
infenfible of the bufy world. But the moment he
arrives into day, he begins to experience many vivid
pains and pleafures ; thefe are at the fame time at-
tended with certain mufcular motions, and from
this their early, and individual aflbciation, they ac-
quire habits of occurring together, that are after-
wards indiflbluble.

i. Of Fear.

•

As foon as the young animal is born, the lirft
important fenfations, that occur to him, are occafi-
oned by the oppreflion about his precordia for want
of refpiration, and by his, fudden traniition from
ninety-eight degrees of heat into fo cold a climate.
— He trembles, that is, he exerts alternately ail the
mufcles of his body, to enfranchife himfeif from

the

SECT. XVI. 8. O F I N S T I N C T. 177

the oppreflion about his bofom, and begins to
breathe with frequent and fhort refpirations ; at
the fame time the cold contracts his red fkin, gra-
dually turning it pale ; the contents of the bladder
and of the bowels are evacuated : and from the ex-
perience of thefe nrft difagreeable fenfations the
pailion of fear is excited, which is no other than
the expectation of difagreeable fenfations. This
early aflbciation of motions and fenfations- perfifts
throughout life ; the paflion of fear produces a cold
and pale fkin, with tremblings, quick refpiration,
and an evacuation of the bladder and bowels, and
thus conftitutes the natural or univerfal language of
this pailion.

On obferving a Canary bird this morning, Ja-
nuary 28, 1772, at the houfe of Mr. Harvey, near
Tutbury, in Derbyfhire, I was told it always fainted
away, when its cage was cleaned, and defired to fee
the experiment. The cage being taken from the
ceiling, and its bottom drawn out, the bird began
to tremble, and turned quite white about the root
of his bill: he then opened his mouth as if for
breath, and refpired quick, flood ilraigluer upon
his perch, hung his wings, fpread his, tail, clofed
his eyes, and appeared quite ft iff and cataleptic for
near half an hour, and at length with much tremb-
ling and deep refpirations came gradually to him-
felf.

2. Of Grief.

That the internal membrane of the noftrils may
be kept always moid, for the better perception of
odours, there are two canals, that conduft the tears
after they ha^ve done their office in moiftening and
cleaning the ball of the eye into a fack, which is
called the lacrymal lack j and from which there is a

duel,

178 OF INSTINCT. SEcr.XVl.8.

duel, that opens into the noftrils : the aperture of
this duel is formed of exquifite fenfibility, and
tvhen it is ftimulated by odorous particles, or by the
drynefs or coldnefs of the air, the fack contracts it-
felf, and pours more of its contained moiflure on
the organ of fmell. By this contrivance the organ
is rendered more fit for perceiving fuch odours,
and is'preferved from being injured by thofe that
are more ftrong or corroiive. Many other recep-
tacles of peculiar fluids difgorge their contents, when
the ends of their duels are Simulated; as the gall
bladder, when the contents of the duodenum ftirnu-
late the extremity of the common bile duel : and
the falivary glands, when the termination of their
duels in the mouth are excited by the (limulus of
the food we mafticate. Atque veficulae feminales
fuum exprimunt fluidum glande penis fricata.

The coldnefs and drynefs of the atmofphere, com-
pared with the warmth and moifture, which the new-
born infant had juft before experienced, difagreeably
affecls the aperture of this lacrymal fack : the tears,
that are contained in this fack, are poured into the
noftrils, and a further fupply is fecreted by the lacry-
mal glands, and diffufed upon the eye-balls ; as is very
vifible in the eyes and noftrils of children foon after
tbeir nativity. The fame happens to us at our maturer
age, for in levere frofty weather, fnivelling and tears
are produced by the coldnels and drynefs of the air.

But the lacrymal glands, which ieparate the tears
from the blood, are fituated on the upper external
part of the globes of each eye ; and, when a
greater quantity of tears are wanted, we contracl
the forehead, and bring down the eye-brows, and
ufe many other diilortions of the face, to comprefs
thele glands.

Now as the1 fuffocating fenfation, that produces
refpiration, is removed ahnoft as foon as perceived,
does not recur again : this difagreeable irrita-
tion

SECT. XVI. 8. OF INSTINCT*. 179

tion of the lacrymal duels, as it mud frequently
recur, till the tender organ becomes ufed to variety
of odours, is one of the firfl pains that is repeatedly
attended to : and hence throughout our infancy,
and in many people throughout their lives, all dii-
agrceable fenfations are attended with fnivelliitg at
the nofe, a profufion of tears, and fome peculiar
di Portions of countenance : according to the laws
of early aflbciation before mentioned, which con-
flitutes the natural or univerfal language of grief.

You may allure yourfelf of the truth of this ob-
fervation, if you will attend to what paffes, when
you read a diftrelsful tale alone ; before the tears
overflow your eyes, you will invariably feel a titilla-
tion at that extremity of the lacrymal duft, which
terminates in the noftril, then the compreilion of
the eyes fucceeds, and the profufion of tears.

Linnaeus afTerts, that the female bear flieds tears
in grief ; the fame has been faid of the hind, and
fome other animals.

3. Of Tender Pleafure.

The firfl moft lively imprefTion of pleafure, that
the infant enjoys after its nativity, is excited by the
odour of its mother's milk. The organ of fmell
is irritated by this perfume, and the lacrymal fack
empties itfelf into the noftrils, as before explained, and
an increafe of tears is poured into the eyes. Any one
may obferve this, when very young infants are about
to fuck ; for at thofc early periods of life, the fenfation
afFecls the organ of fmell, much more powerfully,
than after the repeated habits of fmelling has inured
it to odours of common ftrength : and in our adult
years, the (Ironger finells, though they arc at the
lame time agreeable to us, as of volatile ipirits,
continue to produce an increased fecretion of tears.

This pleating fenfation of fmell is followed by the
early affedion of the infant to the mother that luc-

klcs

iSe O F I N S T I N C T. SICT. XVI. 8.

kles it, and hence the tender feelings of gratitude
and love, as well as of hopelefs grief, are ever after
joined with the titiliation of the extremity of the
lacrymal ducts, and a profufion of tears.

Nor is it fingular, that the lacrymal fack fhould
be influenced by pleafmg ideas, as the fight of agree-
able food produces the fame effect on the falivary
glands. Ac dum vidimus infomniis lafcivas puellse
fimulacrum, tenditur penis.

Lambs make or wriggle their tails, at the time
when they firfl fuck, to get free of the hard excre-
ment, which had been long lodged in their bowels.
Hence this becomes afterwards a mark of pleafure
in them, and in dogs, and other tailed animals.
But cats gently extend and contract their paws when
they are pleafed, and purr by drawing in their breath,
both which refembie their manner of fucking, and
thus become their language of pleafure, for thefe
animals having collar-bones ufe their paws like hands
when they fuck, which dogs and iheep do not.

4. Of Serene Pleafure.

In the action of fucking, the lips of the infant
are clofeci around the nipple of its mother, till he'
has filled his ftomach, and the pleafure occafioned
by the iiimulus of this grateful food fucceej.s. Then
the fphincter of the mouth, fatigued by the con-
tinued action of fucking, is relaxed ; and the anta-
gonift mufcles of the face gently acting, produce the
imile of pleafure : as cannot but be feen by all who
are converfant with children.

Hence this fmile during our lives is aflbciated with
gentle pleafure ; it is vifible in kittens, and puppies,
when they are played with, and tickled ; but more
particularly marks, the human features. For in
children this expreffion of pleafure is much encou-
la^ed, by their imitation of their parents, or friends ;

who

SECT. XVI. 8. O F I N S T I N C T. i8<

who generally addrefs them with a fmiling counte-
nance : and hence ibme nations are moie remark-
able for the gaiety, and others for the gravity of
their looks.

5. Of Anger.

The actions that conftitute the mode of fighting,
are the immediate language of anger in all animals ;
and a preparation for thefe actions is the natural lan-
guage of threatening. Hence the human creature
clenches his fift, and fternly furveys his adyerfary,
as if meditating where to make the attack ; the ram.
and the bull, draws himfelf fome (teps backwards,
and levels his horns ; and the horfe, as he molt fre-
quently fights by ftriking with his hinder feet, turns
his heels to his foe, and bends back his ears, to liften
oui the place of his adverfary, that the threatened
blow may not be ineffectual.

6. Of Attention.

The eye takes in at once but half our horizon,
and that only in the day, and our fmell informs us
of no very diftant objects, hence we confide princi-
pally in the organ of hearing to apprize us of clan-
ger: when we hear any the fmalleft found, that we
cannot immediately account for, our fears are
alarmed, we fufpend our fteps, hold every mufcle
(till, open our mouths a little, erect our ears, and
liften to gain further information : and this by habit
becomes the general language of attention to objects
of fight, as well as of hearing; and even to ihc IUG-
ceflive trains of our ideas.

The natural language of violent pain, which i<s
expreiTed by writhing the body, grinning, and
fcreaming ; and that of tumultuous pleaiiire, ex-
preffed in loud laughter; belong to Section XXXIV.
on Difeafes from Volition.

IX. If

" i82 OF INSTINCT. SEcr.XVF.?.

*i '*•'?*" *x • *'f -V • * * §•

IX. It mufl have already appeared to the reader,

that all other animals, as well as man, are pofiefled
of this natural language of the pafiions, exprefled
in fjgns or tones ; and we (hall endeavour to evince,
that thofe animals, which have preferved themfelves
from being enflaved by mankind, and are aiTociated
in flocks, are alib pofiefled of fome artificial lan-
guage, and of fome traditional knowledge.

The mother-turkey, when (he eyes .a kite hover-
ing high in air, has either feen her own parents
thrown into fear at his prefence, or has by obferva-
tion been acquainted with his dangerous defigns
upon her young. She becomes agitated with fear,
and ufes the natural language of that paflion, her
young ones catch the fear by imitation, and in an
inftant conceal themfelves in the grafs.

At the fame time that (he (hews her fears by her
gefture and deportment, (he ufes a certain exclama-
tion, Kpe-ut, Koe-ut, and the young ones afterwards
know, when they hear this note, though they do not
fee their dam, that the prefence of their adverfary is
denounced, and hide themfelves as before.

The wild tribes of birds have very frequent op-
portunities of knowing their enemies, by obferving
the deftructiun they make among their progeny, of
which every year but a fmall part efcapes to maturity:
but to our domeftic birds thefe opportunities fo
rarely occur, that their knowledge of their diftant
enemies mult frequently be delivered by tradition in
the manner above explained, through many gene-
rations.

This note oi danger, as well as the other notes
of the mother turkey, when (he calls her flock to
their food, o*- to fleep under her wings, appears to be
an artificial language, both as exprefled by the mo-
ther, and as underltood by the progeny. For a hen
teaches this language with equal eafe to tlr* duck-
lings the has hatched from luppofituious eggs, and

educates

SECT. XVI. 9. OF INSTINCT. 183

educates as her own offspring : and the wagtails, or
hedge-fparrows, learn it from the young cuckoo
their fofter nurfling, and fupply him with food long
after he can fly about, whenever they hear his
cuckooing, which Linneus tells us, is his call of
hunger, (Syft. Nat.) And all our domeftic ani-
mals are readily taught to come to us for food,
when we ufe one tone of voice, and to fly from our
anger, when we ufe another.

Rabbits, as they cannot eafily articulate founds,
and are formed into focieties, that live under ground,
have a very* different method of giving alarm. When
danger is threatened, they thump on the ground
with one of their hinder feet, and produce a found,
that can be heard a great way by animals near the
furface of the earth, which would feem to be an ar-
tificial fign both from its fmgularity and its aptnefs
to the fituation of the animal.

The rabbits on the iilarid of Sor, near Senegal,
have white flelh, and are well tafted, but do not bur-
row in the earth, fo that we may fufpect their dig-
ging themfelves houfes in this cold climate is an ac-
quired art, as well as their note of alarm, (Adan-
fon's Voyage to Senegal).

The barking of dogs is another curious note of
alarm, and would feem to be an acquired language,
rather than a natural fign : for " in the ifland of
Juan Fernandes, the dogs did not attempt to bark,
till fome European dogs were put among them, and
then they gradually begun to imitate them, but in
a firange manner at firft, as if they were learning a
thing that was not natural to them," (Voyage to
South America by Don G. Juan, and Don Ant. de
Ulloa. B. 2. c. 4.)

Linnaeus alfo obferves, that the dogs of South
America do not bark at ftrangers. (Syft. Nat.) And
the European dogs, that have been can ied to Guinea,
are faid in three or four generations to ceafe to bark,

and

» $4 O F I N S T I N C T. SECT. XVI. U>.

and only howl, like the dogs that are natives of that
eoaft, (World Difplayed, Vol. XVII. p. 26.)

A circumftance not diffimilar to this, and equally
curious, is mentioned by Kircherus, de Mufurgia,
in, his Chapter de Lulciniis, " That the young
nightingales that are hatched under other birds, never
fing till they are inftru&ed by the company of other
nightingales." And Johnfton affirms, that the night-
ingales that vifit Scotland, have not thefame harmony
as thole of Italy, (Pennant's Zoology, octavo, p. 255) ;
xvhich would lead us to fufpecl that the. fmging of
birds, like human mufic, is an artificial language,
rather than a natural expreflion of paflion.

X. Our mufic like our language, is perhaps en-
tirely conflituted of artificial tones, which by habit
fugged certain agreeable paflions. For the fame
combination of notes and tones do not excite devotion,
love, or poetic melancholy in a native of Indoftan
and of Europe. And £C the Highlander has the
lame warlike ideas annexed to the found of a bag-
pipe (an instrument which an Englilhman derides;,
as the Englifhman has to that of a trumpet or fife,*'
(Dr. Brown's Union of Poetry and Mufic, p. 58.)
So " the mufic of the Turks is very different from
the Italian, and the people of Fez and Morocco
have again a different kind, which to us appears very
rough vaud horrid, but is highly pleafing to them,'*
(L* Arte Armoniaca a Giorgio Antoniotto). Hence
we fee why the Italian opera does not delight an un-
tutored Englifhman; and why thofe, who are unac-
cu domed to mufic, are more pleafed with a tune, the
Second or third time they hear it, than the firft.
For then the fame melodious train of founds excites
the melancholy, they had learned from the fong ; or
the lame vivid combination of them recalls all the
ininhful ideas of the dance and company.

Even the founds, that were once difagreeable to us,
may by habit be affociated with other ideas, fo as to

become

SKCT. XVI. ic. OF INSTINCT. 185

become agreeable. Father Lafitau, in his account of
the Iroquois, fays " the mufic and dance of thofe
Americans, have fomething in them extremely bar-
barous, which at firft difgufts. We grow reconciled
to them by degrees, and in the end partake of them
with pleafure, the favages themfelves are fond of
them to diftra&ion," (IV:ceurs des Savages, Tom. ii.)

There are indeed a few founds, that we very ge-
nerally afibciate with agreeable ideas, as the whitt-
ling of birds, or purring of animals, that are de-
lighted ; and fome others, that we as generally affo-
ciate with difagreeable ideas, as the cries of animals
in pain, the hifs of forne of them in anger, and the
midnight howl of beads of prey. Yet we receive no
terrible or fublime ideas from the lowing of a cow,
or the braying of an afs. Which evinces, that thefe
emotions are owing to previous aflbciations. So if
the rumbling of a carriage in the llreet be for a mo-
ment miftaken for thunder, we receive a fublime fen-
fation, which ceafes as foon as foon as we know it is
the noife of a coach and fix.

There are other difagreeable founds, that are faid
to fet the teeth on edge ; which, as they have always
been thought a neceflary effect of certain difcor-
dant notes, become a proper fubjecl: of our inquiry.
Every one in his childhood has repeatedly bit a part
of the glafs or earthen veflel, in which his food has
been given him, and has thence had a very difagree-
able fenfatiori in the teeth, which fenfation was de-
figned by nature to prevent us from exerting them
on objects harder than themfelves. The jarring
found produced between the cup and the teeth is al-
ways attendant on this difagreeable fenfation : and
ever after when fuch a found is accidentally produ-
ced by the conflicl of two hard bodies, we feel by
aflociation of ideas the concomitant dif.igueable fen-
fation in our teeth.

Others

»86 OF INSTINCT. SECT. XVI. 10.

Others have in their infancy frequently held the
corner of a filk handkerchief in their mouth, or the
end of the velvet cape of their coat, whilft their
companions in play have plucked it from them, and
have given another diiagreeable fenfation to their
teeth, which has afterwards recurred on touching
thofe materials. And the fight of a knife drawn
along a china plate, though no found is excited by
it, and even the imagination of fuch a knife and
plate fo fcraped together, I know by repeated ex-
perience will produce the fame difagreeable fenfa-
tion of the teeth.

Thefe circumnances indifputably prove, that this
fenfation of the tooth-edge is owing to aflbciated
ideas ; as it is equally excitable by fight, touch,
hearing, or imagination.

In refpect to the artificial proportions of found
excited by mufical inftruments, thofe, who have
early in life aflbciated them with agreeable ideas,
and have nicely attended to diftinguim them from
each other, are faid to have a good ear, in that coun-
try where fuch proportions are in famion : and not
from any fuperior perfection in the organ of hearing,
or any inftinftive fympathy between certain founds
and pafiions.

1 have obferved a child to be exquifitely delighted
with muiic, and who could with great facility learn
to fmg any tune that he heard diftinctly, and yet
whole organ of hearing was fo imperfect, that it
was neceflary to fpeak louder to him in common con-
verfation than to others.

Our mufic, like our architecture, feems to have no
foundation in nature, they are both arts purely of
human creation, as they imitate nothing. And the
profeffors of them have only clafled thofe circum-
liances, that are mod agreeable to the accidental
rafle of their age, or country ; and have called it
Proportion* But this proportion mud always fluc-
tuate.

SECT. XVI. ii. OF INSTINCT. 187

tuate, as it refts on the caprices, that are introdu-
ced into our minds by our various modes of educa-
tion. And thefe fluctuations of tafte mud become
more frequent in the prefent age, where mankind
have enfranchifed themfelves from the blind obedi-
ence to the rules of antiquity in perhaps every
fcience, but that of architecture. See Seel. XII.

7- 1-

XL There are many articles of knowledge, which

the animals in cultivated countries feem to learn
very early in their lives, either from each other, or
from experience, or observation : one of the mod
general of thefe is to avoid mankind. There is fo
great a refemblancc in the natural language of the
paflions of all animals, that we generally know,
when they are in a pacific, or in a malevolent hu-
mour, they have the fame knowledge of us ; and
hence we can fcold them from us by fome tones and
geftures, and could poflibly attract them to us by
others, if they were not already apprized of our ge-
neral malevolence towards them. Mr. Gmelin,
Profeflbr at Peterfburg, allures us, that in his jour-
ney into Siberia, undertaken by order of the Em-
prefs of Ruflia, he faw foxes, that exprefled no fear
of himfelf or companions, but permitted him to
come quite near them^ having never feen the human
creature before. And Mr. Bougainville relates,
that at his arrival at the Malouine, or Falkland's
Iflands, which were not inhabited by men, all the
animals came about himfelf and his people ; the
fowls fettling upon their heads and fhoulders, and
the quadrupeds running about their feet. From the
difficulty of acquiring the confidence of old animals,
and the eafe of taming young ones, it appears that
the fear, they all conceive at the fight of mankind,
is an acquired article of knowledge.

This knowledge is more nicely underftood by
rooks, who are formed into fodeties, and build, as

O it

i88 OF INSTINCT.

it were, cities over our heads; they evidently dif-
tinguifli, that the danger is greater when a man is
armed with a gun. Every one has feen this, who
in the fpring of the year has walked under a rookery
with a gun in his hand : the inhabitants of the trees
rife on their wings, and feream to the unfledged
young to flirink into their nefts from the fight of
the enemy. The vulgar obferving this circumftance
fo uniformly to occur, aflert that rooks can fmell
gun-powder.

The fieldfairs, (turdus pilarus) which breed in
Norway, and come hither in the cold feafon for our
winter berries ; as they are affociated in flocks, and
are in a foreign country, have evident marks of
keeping a kind of watch, to remark and announce
the appearance of danger. On approaching a tree,
that is covered with them, they continue fearlefs
till one at the extremity of the bum rifing on his
\vings gives a loud and peculiar note of alarm, when
they all immediately fly, except one other, who
continues till you approach flill nearer, to certify
as it were the reality of the danger, and then he
alfo flies off repeating the note of alarm.

And in the woods about Senegal there is- a bird
called uett-uett by the negroes, andfquallers by the
French, which, as foon as they fee a man, fet up a,
loud feream, and keep flying round him, asif their
intent was to warn other birds, which uponhearing
the cry immediately take wing. Thefe birds are the
bane of fportfmen,. and frequently put me into a
paffion, and obliged me to (hoot them (Adanfon's
Voyage to Senegal, 78). For the fame intent the
letter birds' of our climate feem to fly after a hawk,
cuckooy or owl, and feream to prevent their com-
panions from being furprifed by the general enemies
of themfelves, or of their eggs and progeny.

But the lapwing, (charadrius pluvialis Lin.) when
her unfledged offspring run about the marfhes,

where

SiiCT.XVL ii. OF INSTINCT. 189

where they were hatched, not only gives the note
of alarm at the approach of men or dogs, that her
young may conceal themfelves ; but flying and
fcreaming near the adverfary, (he appears more foli-
citous and impatient, as he recedes from her family,
and thus endeavours to miflead him, and frequently
fucceeds in her defign. Thefe laft inftances are fo
appofite to the fituation, rather than to the natures
of the creatures, that ufe them ; and are fo fimilar
to the actions of men in the fame circumftances,
that we cannot but believe, that they proceed from
a fimilar principle.

Mifs M. E. Jacfon acquainted me, that (he wit-
nefled this autumn an agreeable inftance of fagacity
in a little bird, which feemed to ufe the means to
obtain an end ; the bird repeatedly hopped upon a
poppy-ftem, and (hook the head with its bill, till
many feeds were fcattered, then it fettled on the
ground, and eat the feeds, and again repeated the
lame management. Sept. i, i794._

On the northern coaft of Ireland a friend of mine
faw above a hundred crows at once preying upon
mufcles ; each crow took a mufcle up into the air
twenty or forty yards high, and let it fall on the
(tones, and thus by breaking the (hell, got poflef-
fion of the animal. — A certain philofopher (I think
it was Anaxagoras) walking along the fea-fhore to
gather (hells, one of thefe unlucky birds mistaking
his bald head for a (lone, dropped a (hell-filh upon
it, and killed at once a philofopher and an oyfter.

Our domeftic animals, that have fome liberty, are
alfo pofleffed of fome peculiar traditional knowledge;
dogs and cats have been forced into .each other's fo-
ciety, though naturally animals of a very different
kind, and have hence learned from each other to
eat dog's grafs, (agroitis canina) when they are fick,
to promote vomiting. I have feen a cat miftake the

O 2, blade

490 OF INSTINCT. SECT. XVI. n.

blade of barley for this grafs, which evinces it is an
acquired knowledge. They have alfo learnt of each
other to cover their excrement and urine ; about a
fpoonful of water was fpilt upon iny hearth from the
tea-kettle, and I obferved a kitten cover it with aflies.
Hence this mud alfo be an acquired art, as the crea-
ture miflook the application of it.

To preferve their fur clean, and efpecially their
\vhiikers, cats warn their faces, and generally quite
behind their ears, every time they eat. As they
cannot lick thofe places with their tongues, they firit
wet the infide of the leg with faliva, and then re-
peatedly warn their faces with it, which mufl origi-
nally be an effect of reafoning, becaufe a means is
ufed to produce an effect ; and feems afterwards to
be taught or acquired by imitation, like the greateft
part of human arts*

Thefe animals feem to poiTefs fomething like an
additional fenfe by means of their whifkers ; which
have perhaps fome analogy to the antennas of moths
and butterflies. The whifkers of cats confift not
only of the long hairs on their upper lips, but they
have alfo four or five long hairs (landing up from
each eyebrow, and alfo two or three on each cheek ;
all which, when the animal erects them, make with
their points fo many parts of the periphery of a cir-
cle, of an extent at lead equal to the circumference
of any part of their own bodies. With this inflru-
ment, I conceive, by a little experience, they can
at price determine, whether any aperture amongft
hedges or fhrubs, in which animals of this genus
live in their wild flare, is large enough to admit
their bodies ; which to them is a matter of the great-
eft confequence, whether purfuing or purfued.
They have like wife a power of erecting and bring-
ing forward the whifkers on their lips ; which pro- .
bably is for the purpofe of feeling, whether a dark
hole be further- permeable.

The

SECT. XVI. ii. OF INSTINCT. 191

The antennas, or horns, of butterflies and moths,
who have awkward wings, the minute feathers of
which are very liable to injury, ferve, I fuppofe, a
fimilar purpofe of meafuring, as they fly or creep
amongft the leaves of plants or trees, whither their
wings can pafs without touching them.

Mr. Leonard, a very intelligent friend of mine,
faw a cat catch a trout by darting upon it in a deep
clear water at the mill at Weaford, near Lichfield.
The cat belonged to Mr. Stanley, who had often
feen her catch fifh in the fame manner in fummer,
when the mill-pool was drawu fo low, that the fifti
could be feen. I have heard of other cats taking
fifh in mallow water, as they flood on the bank.
This feems a natural art of taking their prey in cats,
which their acquired delicacy by domeftication has
in general prevented them from ufing, though their
defire of eating fifh continues in its original ftrength.
Mr. White, in his ingenious Hiftory of Selbourn,
was witnefs to a cat's fuckling a young hare, which
followed her about the garden, and came jumping
to her call of affection. At Elford near Lichfield,
the Rev. Mr. Sawley had taken the young ones out
of a hare, which was fhot ; they were alive, and the
cat, who had juft lofl her own kittens, carried them
away, as it was fuppofed, to eat them ; but it pre-
fently appeared, that it was affection not hunger
which incited her, as fhe fuckled them, and brought
them up as their mother.

Other inflances of the miftaken application of
what has been termed indinct may be obferved in
flies in the night, who miftaking a candle for day*
light, approach and perifh in the flame. So the pu-
trid fmell of the flapelia, or carrion-flqwer, allures
the large flefh-fly to depofit its young worms on its
beautiful petals, which perifh there for want of
ftourifhment. This therefore cannot be a necefTary

inftinft

192 OF INSTINCT. SECT. XVI. ir

inflincl, becaufe the creature miftakes the applica-
tion of it.

Though in this country horfes fhew little veftiges
of policy, yet in the defarts of Tartary, and Siberia,
when hunted by the Tartars they are feen to form a
kind of community, fet watches to prevent their
being furprifed, and have commanders, who direct,
and haften their flight, Origin of Language, Vol. I.
p. 2 i 2. In this country, where four or five horfes
travel in a line, the firft always points his ears for-
ward, and the lad points his backward, while the
intermediate ones leem quite carelefs in this refpe£t;
which feems a part of policy to prevent furprife. As
all animals depend moft on the ear to apprize them
of the approach of danger, the eye taking in only
half the horizon at once, and horfes poflefs a great
nicety of this fenfe ; as appears from their mode of
fighting mentioned No. 8. 5. of this Section, as well
as by common obfervation.

There are fome parts of a horfe, which he cannot
conveniently rub, when they itch, as about the
fhoulder, which he can neither bite with his teeth,
nor fcratch with his hind fool ; when this part itches,
he goes to another horfe, and gently bites him in
the part which he wifhes to be bitten, which is im*
mediately done by his intelligent friend. I once
observed a young foal thus bite its large mother,
who did not choofe to drop the grafs fhe had in her
mouth, and rubbed her nofe againfl the foal's neck
initead of biting it ; which evinces that fhe knew
the defign of her progeny, and was not governed
by a necefiary inftind to bite where fhe was bitten,

Many of our fhrubs, which would otherwife af-
ford an agreeable food to horfes, are armed with
thorns or prickles, which fecure them from thofe
animals; as the holly, hawthorn, goofeberry, gorfe.
In the extenfive moorlands of Staftbrdfhire, the

horfe§

Sacr.XVI. n. OF INSTINCT. 193

horfes have learnt to (tamp upon a gorfe-bufh with
one of their fore-feet for a minute together, and
when the points are broken, they eat it without
injury. The horfes in the new for eft in Hampihire
are affirmed to do the fame by Mr. Gilpin. Foreft
Scenery, II. 251, and 112. Which is an art other
horfes in the fertile parts of the country do not
pofiefs, and prick their months till they bleed, if
they are induced by hunger or caprice to attempt
eating gorfe.

Swine have a fenfe of touch as well as of fmell at
the end of their nofe, which they ufe as a hand,
both to root up the foil, and to turn over and exa-
mine objects of food, fomewhat like the probofcis
of an elephant. As they require flicker from the
cold in this climate, they have learnt to collecl;
draw in theh mouths to make their neft, when the
wind blows cold ; and to call their companions by
repeated cries to aflift in the work, and add to their
warmth by. their numerous bed-fellows. Hence
thefe animals, which are efteemed fo unclean, have
alfo learned never to befoul their dens, where they
have liberty, with their own excrement ; an art,
which cows and horfes, which have open hovels to
run into, have never acquired. I have obferved
great fagacky in fwine ; but the fhort lives we allow
them, and their general confinement, prevents their
improvement, which might probably be otherwife
greater than that of dogs.

Inftances of the fagacity and knowledge of ani-
mals are very numerous to every obferver, and
their docility in learning various arts from mankind,
evinces that they may learn fimilar arts from their
own fpecies, and thus be pofleffed of much acquired
and traditional knowledge.

A dog whofe natural prey is flieep, is taught by
mankind, not only to leave them unmolefted, but

to

194- OF INSTINCT. SECT.XVI.M,

to guard them ; and to hunt, to fet, or to deftroy
other kinds of animals, as birds, or vermin ; and
in fome countries to catch fi(h, in others to find
truffles, and to pra&ife a great variety of tricks ;
is it more furprifing that the crows mould teach
each other, that the hawk can catch lefs birds, by
the fuperior fwiftnefs of his wing, and if two of
them follow him, till he fucceeds in his defign, that
they can by force mare a part of the capture ? This
1 have formerly obferved with attention and afto-
nifhment.

There is one kind of pelican mentioned by Mr.
Ofbeck, one of Linnseus's travelling pupils (the
pelicanus aquilus), whofe food is fim ; and which
it takes from other birds, becaufe it is. not formed
to catch them itfelf ; hence it is called by the Eng-
Jim a Man-of-war-bird, Voyage to China, p. 88.
There are many other interefting anecdotes of the
pelican and cormorant, collected from authors of
the beft authority, in a well-managed Natural Hif-
tory for Children, publifhed by Mr. Galton. John-
fon. London.

And the following narration from the very accu-
rate Monf. Adanfon, in his Voyage to Senegal,
may gain credit with the reader : as his employ-
ment in this country was folely to make obferva-
tions in natural hiftory. On the river Niger, in his
road to the ifland Griel, he faw a great number pf
pelicans, or wide throats. " They moved with
great ftate like fwans upon the water, and are the
largeft bird next to the oftrich ; the bill of the one
I killed was upwards of a foot and half long, and
the bag fattened underneath it held two and twenty
pints of water. They fwim in flocks, and form a
large circle, which they contract afterwards, driv-
Jng.the fim before them with their legs : when they
fee the fifh in fufficient number confined in this

fpace.

SECT. XVI. 12. OF INSTINCT, 195

fpace, they plunge their bill wide open into the
water, and (hut it again with great quicknefs. They
thus get fifh into their throat-bag, which they eat
afterwards on ihore at their leifure." P. 247.

XII. 'Ihe knowledge and language of thofe birds,
that frequently change their climate with the fea-
fons, is fHll- more extenfive : as they perform thefe
migrations in large focieties, and are Ids fubjecl to
the power of man, than the refident tribes of birds.
They are faid to follow a leader during the day,
who is occafionally changed, and to keep a conti-
nual cry during the night to keep themfelves toge-
ther. It is probable that thefe emigrations were
at firft undertaken as accident directed, by the more
adventurous of their fpecies, and learned from one
another like the difcoveries of mankind in naviga-
tion. The following circumltances ftrongly fupport
this opinion.

i. Nature has provided thefe animals, in the cli-
mates where they are produced, with another re-
fource : when the feafon becomes too cold for their
constitutions, or the food they were fupported with
ceafes to be fupplied, I mean that of ileeping,
Dormice, fnakes, and bats, have not the means of
changing their country ; the two former from the
want of wings, and the latter from his being not
able to bear the light of the day. Hence thefe ani-
mals are obliged to make ufe of this refource, and
lleep during the winter. And thofe fwallows that
have been hatched too late in the year to acquire
their full (Irength of pinion, or that have been
maimed by accident of difeafe, have been frequent-
ly found in the hollows of rocks on the fea coafts,
and even under water in this torpid ftate, from
which they have been revived by the warmth of a
fire. This torpid date of fwallows is teftined by
innumerable evidences both of antient and modern

names.

*96 OFINSTINCT. SECT. XVf. 12.

names. Ariftotle -fpeaking of the fwallows fays,
" They pafs into warmer climates in winter, if
fuch places are at no great diftance ; if they are,
they bury themfelves in .the climates where they
dwell," (8. Hift. c. 16. See alfo Derham's Phyf.
Theol. v. ii. p. 177.)

Hence their emigrations cannot depend on a
necejjary inftincl:, asr the emigrations themfelves are
not mceffary !

2. When the weather becomes cold, the fwal-
lows in the neighbourhood aifemble in large flocks ;
that is, the unexperienced attend thofe that have
before experienced the journey they are about to
undertake : they are then feen fame times to hover
on the coaft, till there is calm weather, or a wind,
that fuits the direction of their flight, Other birds
of paflage have been drowned by thoufands in the
fea, or have fettled on (hips quite exhaufted with
fatigue. And others, either by miftaking their
courfe, or by diftrefs of weather, have arrived in
countries where they were never feen before, and
thus are evidently fubjec~l tto the fame hazards that
the human fpecies undergo, in the execution of their
artificial purpofes.

3. The fame birds are emigrant from fome coun-
tries and not fo from others : the fwallows were feen
at Goree in January by an ingenious philofopher of
my acquaintance, and he was told that they conti-
nued there all the year; as the warmth of the cli-
mate was at all feafons fufficient for their own con-
flituiions, and for the production of the flies that
fupply them with nouriftiment. Herodotus fays,
that in Lybia, about the fprings of the Nile, tbe
fwallows continue all the year. (L. 2,)

Quails (tetrao corturnix, Lin.) are birds of paflage
from the coalt of Barbary to Italy, and have fre-
quently fettled in large fhoals on (hips, fatigued
with their flight. (Hay, Wifdom of God, p. 129.

Derharu

SECT. XVI. 12. O F ! N S 7 I N C T. 197

Derham Phyfic. Theol. v. ii. p. 178.) Dr. Ruffe!,
in his Hiftory of Aleppo, obferves that the fwallows
vifit that country about the end of February, and
having hatched their young difappear about the
end of July ; and returning again about the
beginning of October, continue about a fortnight,
and then again difappear. (P. 70 )

When my late friend Dr. Chambres, of Derby,
was on the ifland of Caprea in the bay of Naples,
he was informed that great flights of quails annu-
ally fettle on that ifland about the beginning of May,
in their paffage from Africa to Europe. And that
they always come when the fouth-eaft wind blows,
are fatigued when they reft on this iiland, and are
taken in fuch amazing quantities and fold to the
Continent, that the inhabitants pay the bifhop his
ftipend out of the profits arifmg from the fale of
them.

The flights of thefe birds acrofs the Mediterra-
nean are recorded near three thoufand years ago.
" There went forth a wind from the Loid and
brought quails from the fea, and let them fall upon
the camp, a day's journey round about it, and they
were two cubits above the earth," (Numbers, chap,
ii. ver. 31.)

In our country, Mr. Pennant informs us, that
fome quails migrate, and others only remove from
the internal parts of the ifland to the coafts, (Zoo-
logy, octavo, 210.) Some of the ringdoves and
flares breed here, others migrate, (ibid. 510, 511.^
And the flender billed fmall birds do not all quit
thefe kingdoms in the winter, though the difficulty
of procuring the worms and infects, that they feed
on, fupplies the fame reafon for migration to them
all, (ibid. 51 1.)

Linnseus has obferved, that in Sweden the female
chaffinches quit that country in September, migrat-
ing into Holland, and leave their mates behind till

their

i^S O F I N S T I N C T. SECT. XVI. 12.

their return in fpring. Hence he has called them
Fringilla ccelebs, (Amaen. Acad. ii. 42. iv. 595.)
Now in our climate both fexes of them are peren-
nial birds. And Mr. Pennant obferves that the hoo-
poe, chatterer, hawfinch, arid crofsbill, migrate into
England fo rarely, and at fuch uncertain times, as
not to deferve to be ranked among our birds of paf-
fage, (ibid. 51'!.)

The waterfowl, as geefe and ducks, are better
adapted for long migrations, than the other tribes
of birds, as, when the weather is calm, they can
not only reft ttiemfelyes, or fleep upon the ocean,
but poflibly procure fome kind of food from it.

Hence in Siberia, as foon as the lakes are fro-
zen, the water fowl, which are very numerous, all
difappear, ,and are fuppofed to fly to warmer cli-
mates, except the rail, which, from its inability for
long flights, probably fleeps, like our bat, in their
winter. The following account from the Journey
of ProfefTor Gmelin, may entertain the reader,
" In the neighbourhood of Krafnoiark, amongft
many other emigrant water fowls, we obferved a
great number of rails, which when purfued never
took flight, but endeavoured to efcape by running.
We enquired how thefe birds, that could not fly,
could retire into other countries in the winter, and
were told, vbo-th by the Tartars and Affanians, that
they well knew thofe birds could not alone pafs
into other countries : but when the cranes (|es grues)
retire in autumn, each one takes a rail (un rale; upon,
his back, and carries hirn to a warmer climate.'*

Recapitulation.

T. All birds of paflfage can exift in the climates,
where they are produced.

a, They

SECT. XVI. 13. O F I N S T I N C T. 199

2. They are fubjeft in their migrations to the
fame accidents and difficulties, that mankind are
fubjecl: to in navigation.

3. The fame fpecies of birds migrate from fome
countries, and are refident in others.

From all thefe circumftances it appears that the
migrations of birds are not produced by a necef-
fary inftincl:, but are accidental improvements, like
the arts among mankind, taught by their cotempo-
raries, or delivered by tradition from one genera-
tion of them to another.

XIII. In the feafon of the year which fupplies
the nourimment proper for the expected brood, the
birds enter into a contract of marriage, and with
joint labour conftruct a bed for the reception of
their offspring. Their choice of the proper feafon,
their contracts of marriage, and the regularity
with which they conftrudt their nefts, have in all
ages excited the admiration of naturalifts ; and
have always been attributed to the power of in-
fHnft, which, like the occult qualities of the an-
tient philofophers, prevented all further enquiry.
We (hall confider them in their order.

Their Choice of the Seafon.

Our domeftic birds, that are plentifully fupplied
throughout the year with their adapted food, and
are covered with houfes from the inrlemeacy of the
weather, lay their eggs at any feafon: which evinces
that the fpring of the year is not pointed out to
them by a necelfary inftincl.

Whilft the wild tribes of birds choofe this time
of the year from their acquired knowledge, that
the mild temperature of the air is more convenient
for hatching their eggs, and is foon likely to fupply

. that

O F I N S T I N C T. $ECT. XVI. i 3.

that kind of nourifhment that is wanted for their
young.

If the genial warmth of the fpring produced the
paffion of love, as it expands the foliage of trees,
all other animals (hould feel its influence as well
as birds : but, the viviparous creatures, as they
fuckle their young, that is, as they previoufly di-
geft the natural food, that it .may better fuit the
tender flomachs of their offspring, experience the
influence of this paflion at all feafons of the year,
as cats and bitches. The graminivorous animals
indeed generally produce their young about the
time when grafs is fupplied in the greateft plenty,
but this is without any degree of exaclnefs^ as ap-
pears from our cows, fheep, ,and hares, and may
be a part of the traditional knowledge, which they
learn from the example of the parents.

fbeir Contrafts of Marriage.

Their mutual paffion, and the acqnired know-
ledge, that their joint labour is neceflary to procure
fuftenance for their numerous family, induces the
wild birds to enter into a contract of marriage,
which does not however take place among the
ducks, geefe, and fowls, that are provided with
their daily food from our barns.

An ingenious philofopher has lately denied, that
animals can enter into contracts, and thinks this an
efTential difference between them and the human
creature : — but does not daily obfervation con-
vince us, that they form contracts of friendfhip
with each other, and with mankind ? When pup-
pies and kittens play together, is there not a tacit
contract, that they will not hurt each other ? And
does not your favorite dog expect you mould give
him his daily food, for his fervices and attention

to

SECT. XVI. 13. OF INSTINCT. 201

to you ? And thus barters his love for your pro.
tection ? In the fame manner that all contrads arc
made amongft men, that do not underftand each
others' arbitrary language.

The Conjlruftion of their Ne/ls.

1. They feem to be inftrufted how to build their
nefts from their obfervation of that, in which they
were educated, and from their knowledge of thofe
things, that are mod agreeable to their touch in
refped to warmth, cleanlinefs, and (lability. They
choofe their fituations from their ideas of fafety
from their enemies., and of flicker from the wea-
ther. Nor is the colour of their nefts a circum-
ftance unthought of; the finches, that build in
green hedges, cover their habitations with green
mofs ; the fwallow or martin, that builds againft
rocks and houfes, covers her's with clay, whilfi
the lark choofes vegetable ftraw nearly of the co-
lour of the ground (lie inhabits : by this contrivance,
they are all lefs liable1 to be difcovered by their ad-
verlaries.

2. Nor are the nefts of the fame fpecies of birds
conftrucled always of the fame materials, nor in the
fame form ; which is another circumftance that
afcertains, that they are led by obfervation.

In the trees before Mr. Levet's houfe in Lichfield,
there are annually nefts built by fparrows, a bird
which ufually builds under the tiles of houfes, or
the thatch of barns. Not finding fuch convenient
fituations for iheir nefts, they build a covered neft
bigger than a man's head, with an opening like a
mouth at the fide, refembling that of a magpie,
except that it is built with ftraw and iay, and lined
with feathers, and fo nicely managed as to be a de-
fence againft both wind and rain.

The

sea O F I N S T I N C T. SECT. XVL I ji

The following extract from a Letter of the Rev.
IVJr. J. Darwin, of Carleton Scroop in Lincolnfhire,
authenticates a curious fact of this kind. " When
I mentioned to you the circumftance of crows or
frooks building in the fpire of Welbourn church,
you expreiTed a defire of being well informed of the
certainty of the fact. Welbourn is fituated in the
road from Grantham to Lincoln on the Cliff row ; I
yefterday took a ride thither, and enquired of the
re&or, Mr. Ridgehill, whether the report was true,
that rooks built in the fpire of his church. He af-
fured me it was true, and that they had done fo time
immemorial, as his parifhioners affirmed. There was
a common tradition, he faid, that formerly a rookery
in fome high trees adjoined the church yard, which
being cut down (probably in the ipring, the building
ieafon), the rooks removed to the church, and built
theiy nefts on the outfide of the fpire on the tops of
•windows, which by their projection a little from the
fpire made them convenient room, but that they
built a Ho on the infide. I faw two nefts made with
/licks on the outfide, and in the fpires, and Mr.
Ridgehill faid there were always a great many.

Ct Ifpent the day with Mr. Wright, a clergyman,
at Fulbeck, near Welbourn, and in the afternoon Dr.
Ellis of Headenham, about two miles from Weibourn,
drank tea at Mr. Wright's, who faid he remembered,
when Mr. Welby lived at Welbourn, that he received
a letter from an acquaintance in the weft of England,
defiring an anfwer, whether the report of rooks
building in Welbourn church was true, as a wager
was depending on that fubject : to which he returned
an anfwer ascertaining the fact, and decided the
wager." Aug. 30, 1704.

So the jackdaw (corvus monedula) generally
builds in church-fteeples, or under the roofs of
high houfes ; but at Selbourn, in Southamptonihire,
where towers and fteeples are not fufficiently nu-
merous,

Skcr. XVI. 13. OFlNSTINct.

merous, thefe birds build in forfaken rabbit bur-
rows. See a curious account of thefe fubterra-
nean nefts in White's Hiftory of Selbourn, p. 59.
Can the ikilful change of architecture in thefe
birds and the fparrows above mentioned be go-
verned by inftinct ? Then they muft have two in-
ftincts, one for common, and the other for extra-
ordinary occafions.

I have feen green worded in a neft, which no
where exifts in nature : and the down of thirties irt
thofe nefts, that were by fome accident conftructed
later in the fummer, which material could not be
procured for the earlier nefts : in many different
climates they cannot procure the fame materials^
that they ufe in ours. And it is well known, that
the canary birds, that are propagated in this coun-
try, and the finches, that are kept tame, will build
their nefts of any flexile materials, that are given
them. Plutarch, in his Book on Rivers, fpeaking
of the Nile, fays* " that the fwallows collect a ma-
terial, when the waters recede, with which they
form nefts, that are impervious to water." And in
India there is a fwallow that collects a glutinous
fubftance for this purpofe, whofe neft is efculent,
and efteemed a principal rarity amongft epicures,
(Lin. Syft. Nat.) Both thefe muft be conftruded of
very different materials from thofe ufed by the fwal-
lows of our country.

In India the birds exert more artifice in building
their nefts on account of the monkeys and fnakes :
fome form their penfile nefts in the fliape of a purfe,
deep and open at top; others with a hole in the
fide ; and others, ftill more cautious, with an en-
trance at the very bottom, forming their lodge
near the fummit. But the taylor-bird will not
ever truft its neft to the extremity of a, tender twig,
but makes one more advance to fafety by fixing it
to the leaf itfelf. It picks up a dead leaf, and fews

VOL. I, P i

f 04 O F I N S T I N C T. SECT. XVI. i>

it to the fide of a living one, its flender bill being
its needle, and its thread fome fine fibres ; the lin-
ing confifts of feathers, gofTamer, and down; iu
eggs are white, the colour of the bird light yellow,
its length three inches, its weight three ftxteenths
of an ounce ; fo that the materials of the neft, and
the weight of the bird, are not likely to draw down
an habitation fo flightly fufpended. A neft of this,
bird is preferved in the Bririfh Mufeum, (Pennant**
Indian Zoology). This calls te* one's mind the Mo-
faic account of the origin of mankind, the firft
dawning of art there afcribed to rhemr i^that of
fewing leaves together. For many other curious
kinds of nefts fee Natural Hiftory for Children, by
Mr. Galton. Johnfon. London Part I. p. 47*
Gen. Oriolus*

3, Thofe birds that are brought up by our care*
and have had little communication with others of
their own fpecies, are very defective in this ac-
quired knowledge ; they are not only very awk^
ward in the conftrucUon of their nefts, but gene-
rally fcatter their eggs in various parts of the room
or cage, where they are confined, and feldom pro-
duce young ones, till, by failing in their firft at-
tempt, they have learnt fomsthing from their owrv
obfervation.

4. During the time of incubation birds are faid'
in general to turn their eggs every day ; fome cover
them, when they leave the neft, as^ ducks and'
geefe.; in fome the male is^faid to bring food to the
female, that (he may have lefs occafion of abfencer
m others he is faid to take her place, when (he goes
in queft, of food -r and all of rhem are faid to kave
their eggs a fhorter time in- cold weather than in
warm. In. Senegal' the oftrich fits on her eggs only
during the night, leaving them in the day to thq,
heat of the fun ; but at the Cape of Good Hope,
where the heat is lefs,, fh$ fits on them day and
night.

If

. XVI. 13- OF INSTINCT. 205

If it fhould be afked, what induces a bird to fit
weeks on its firft eggs unconfcious that a brood of
young ones will be the product ? The anfwer mud
be, that it is the fame paflion that induces the hu-
man mother to hold her offspring whole nights and
days in her fond arms, and prefs it to her bofom^
unconfcious of its future growth to fenfe and man-
hood, till obfervation. or tradition have informed
her.

5. And as many ladies are too refined to hurfe
their own children, and deliver them to the care
and provifion of others ; fo is there one inftance
of this vice in the feathered world. The cuckoo
in fome parts of England, as I am well informed
by a very diftinft and ingenious gentleman, hatches
and educates her own young ; whilft in other parts
me builds no neft, but ufes that of fome leffer
bird, generally either of the wagtail, or hedge
fparrow, and depofiting one egg in it, takes no
further care of her progeny.

As the Rev, Mr. Stafford was walking in Glofop
Dale, in the Peak of Derbyfhire, he faw a cuckoo
rife from its neft. Thfe neft was on the ftump of a
tree, that had been fome time felled, among fome
chips that were in part turned grey^ fo as much to
referable the colour of the birdj in this neft were
two young cuckoos : tying a firing about the leg of
one of them^ he pegged the other end of it to the
ground, and very frequently for many days beheld
the old cuckoo feed thef£ her young, as he flood
Very near them.

The following extract of a Letter from the Rev.
Mr. Wilmot, of Morley, near Derby, ftrengthens
the truth of the fact above mentioned, of the
cuckoo fometimes making a neft, and hatching her
own young.

<c In the beginning of July, 1792, I was attend-
ing fome labourers on my farm, when one of them

P 2 faid

io6 OF INSTINCT. SECT. XVI. t

faid to me, "There is a. bird's neft upon one of the
Coal flack Hill's ;' the bird is now fitting, and is ex-
aftly like a cuckoo. They fay that cuckoos never
hatch their own eggs, otherwife I fhould have fworn
it was one " He took me to the fpot, it was in an open
fallow ground ; the bird was upon the neft, I flood and
obferved her fome time, and was perfectly fatisfied it
was a cuckoo ; I then put my hand towards her, and
fhe almoft let me touch her before fhe rofe from the
neft, which (he appeared to quit with great unea-
linefs, flamming over the ground in the manner that
a hen partridge does when didurbed fr/om a new
hatched brood, and went only to a thicket about
forty or fifty yards from the neft ; and continued
there as long as 1 ftaid to obferve her, which was
not many minutes. In the neft, which was barely a
hole fcratched out of the coal-flack in the manner
of a plover's neft, I obferved three eggs, but did
not touch them. As I had labourers conftantly at
work irr that field, I went thither every day, and
always looked to fee if the bird was there, but did
not dtfturb her for feven or eight days, when I was
tempted to drive her from the n,eft, and found two-,
young ones, that appeared t'» have been hatched
fome days, but there was no appearance of the third
egg. 1 then mentioned this extraordinary circinn-
ftance (for fuch I thought it) to Mr. and Mrs. Holyoak
of Bldrord Grange, Warwickfhrre, and to Mifs M.
Willes, who were on a vifit at my houfe, and who
all went to fee it. Very lately 1 reminded Mr. Holy-
oak' of it, who told me he had a perfect recollection
of the whole, and that, confidering it a curiofityr.
he walked to look at it feveral times, was perfectly
fansfled as to its- being a cuckoo, and thought her
more attentive to her young, than any other bird he
ever obferved, having always found her brooding
her young. In about a week after I firft faw the
young ones, one of them was miffing, and I rather
fufpecled my plough-boys having taken it ; though it

in+eht

SECT. XVI. 14. OF INSTINCT. ±07

might poffibly have been taken by a hawk, fome
time when the old one was feeking food. I never
found her off her neft but once, and that was the
lad time 1 (aw the remaining young one, when it
was almoft full feathered. I then went from home
for two or three days, and, when I -returned, the
young one was gone, which I take for granted had
flown. Though during this time I frequently faw
cuckoos in the thicket I mention, I never obferved
any one, that I fuppofed to be the cock-bird, pair-
ed with this hen."

Nor is this a new obfervation, though it is entire-
ly overlooked by the modern naturalifts, for Arif-
totle (peaking of the cuckoo, aiTerts that me fome-
times builds her neft among broken rocks, and oa
high mountains, (L. 6. H. c. i.) but adds in ano-
ther place that (he generally poffeffes the neft of
another bird, (L. 6. H. c. 7.) And Niphus fays
that cuckoos rarely build for themfelves, moft fre-
quently laying their eggs in the nefts of other birds,
(Gefner, L, 3. de Cuculo.)

The Philofopher who is acquainted with thefe
facts concerning the cuckoo, would feem to have
very little reaion himfelf, if he could imagine this
neglect of her young to be a neceffary injlinft !

XiV. The deep recedes of the ocean are inac-
ceffible to mankind, which prevents us from hav-
ing much knowledge of the arts and government
of its inhabitants.

i. One of the baits ufed by the fiflierman, is an
animal called an Old Soldier, his fize and form are
fomewhat like the craw-fifli, with this difference,
that his tail is covered with a tough membrane in-
ftead of a (hell ; and to obviate this defect, he
feeks out the uninhabited (hell of fome dead fifh,
that is hrge enough to receive his tail, and carries
It about with him as part of his clothing or armour,

2,

*oS OF INSTINCT. SECT. XVI. 14.

2. On the coafts about Scarborough, where the
haddocks, cods, and dog fiih, are in great abund-
ance, the fifherrnen univerfally believe that the dog*
fifli make a line, or femicircle, to encompa& a fhoal
of haddocks and cod, confining them within cer-
tain limits near the Chore, and eating them as occa-
fion requires. For the haddocks and cods are al-
ways found near the more without any dog-fifh
among them, and the dog-fi(h further off without
any haddocks or cod ; arad yet the former are known
to prey upon the latter, and in fome years devour
fuch immenfe quantities as to render this fifhery
more expenfive than profitable.

•3. The remora, when he wifhes to remove his
fituation, as he is a very flow iwimmer, is content
to take an outfide place on whatever conveyance
is going his way ; nor can the cunning animal be
tempted to quit his hold of a fhip when (he is fail-
ing, not even for the lucre of a piece of pork, left
it fhould endanger the lofs of his paffage : at other
times he is eafily caught with the hook.

4. The crab-fim, like many other teftaceous ani-
mals, annually changes its (hell ; it is then in a foft
Hate, covered only with a mucous membrane, and
conceals itfeif in holes in the fand or under weeds ;
at this place a hard (helled crab always Hands cen-
tinel, to prevent the fea infects from injuring the
other in its defencelefs (late ; and the fiftiermen
from his appearance know where to find the foft
ones, which they ufe for baits in catching other
fidi.

And though the hard (helled crab, when he is on
this duty, advances boldly to meet the foe, and
will with difficulty quit the field ; yet at other
times he (hews great timidity, and has a wonder-
ful fpeed in attempting his efcape ; and, if often,
interrupted, will pretend death like the fpider, and
xyatch an opportunity to fmk himfelf into the fand,

keepipg

SECT. XVI. 14. OF INSTINCT.

keeping only his eyes above. My ingenious friend
Mr. Burdett, who favoured me with thefe accounts
at the time he was furveying the coafts, thinks the
commerce between the fexes takes place at this
time, and infpires the courage of the creature.

5. The flioals of herrings, cod?, haddocks, and
other fifh, which approach our fliores at certain fea-
fons, and quit them at other feafons without leav-
ing one behind ; and the falmon, that periodically
frequent our rivers, evince, that there are vagrant
tribes of fifh, that perform as regular migrations as
the birds of paffage already mentioned.

6. There is a cataracl on the river LLfFey in Ire-
land about nineteen feet high : here in the falmon
feafon many of the inhabitants amufe thernfelves in
obfcrving thefe fifh le,:p up the torrent. They dart
themfelves quite out of the water as they afcend,
and frequently fall back many times before they
furmount it, and bafkets made of twigs are placed
near the edge of the ftrcani to catch them ia
their falL

I have obferved, as I have fat by a fpout of wa-
ter, which defcends from a ftone trough about two
feet into a ftream below, at particular feafons of the
year, a great number of little fiih called minurns,
or pinks, throw themfelves about twenty times their
own length out of the water, expecting to get into
the trough above.

This evinces that the ftorgee, or attention of the
dam to provide for the offspring, is ftrongly everted
amongft the nations of fifh, where it would feera
to be the moft neglected ; as thefe falmon cannot
be fuppofed to attempt fo difficult and dangerous a
talk without being eonfcious of the purpofe or end
of their endeavours.

It is further remarkable, that moft of the old fal-
mon return to the fea before it is proper for the
young (lioaU to attend them, yet that a few old ones

continue

«io OF INSTINCT. SECT. XVI. i&

continue in the rivers fo late, that they become per-
fectly emaciated by the inconvenience of their fitu-
ation, and this apparently to guide or to protect
the unexperienced brood.

Of the fmaller water animals we have fUll lefs
knowledge, who neverthelefs probably poflels many
fuperior arts; fome of thefe are mentioned in Bo-
tanic Garden, P. L Add. Note XXVII. and
XXVIII. The nympha of the water-moths of our
rivers, which cover themfelves with cafes of ft raw,
gravel, and fhell, contrive to make their habitations
nearly in equilibrium with the water ; when too
heavy, they add a bit of wood or draw; when tqq
light, a bit of gravel. Edinb. Tranf.

All thefe circumftances bear a near refemblance
to the deliberate actions of human reafon.

XV. We have a very imperfect acquaintance with,
the various tribes of infects: their occupations, man-
ner of life, and even the number of their fenfcs,
differ from our own, and from each other ; but
there is reafon to imagine, that thofe which poflefs
the fenfe of touch in the njoft exquifite degree, and
-whofe occupations require the mod conftant exer-
tion of their powers, are indued with a greater pro-
portion of knowledge and ingenuity.

The fpiders of this country manufacture nets of
various forms, adapted to various fituations, to ar-
reft the flies that are their food ; and fome of them,
have a houfe or lodging place in the middle of the
net, well contrived for warmth, fecurity, or con-
cealment. There is a large Spider in South Ame-
rica, who conftructs nets of fa ftrong a texture as
to entangle fmall birds, particularly the humming
bird. And in Jamaica there is Another fpider, who
digs a hole in the earth obliquely downwards, about
fhree inches in length, and one inch in diameter,
this cavity (he lines with a tough thick web, which
^rhen taken out refembles a leathern purfe :

6tcT.XVI.is. OF INSTINCT. -211

what is mod curious, this houfe has a door with
hinges, like the operculum of fome fea-fhel's ; and
herfelf and family, \vho tenant this neft, open and
(hut the door, whenever they pafs or repafs. This
hiftory was told me, and the neit wiih its operculum
fhewn me by the late Dr Butt of Bath, who was
fome years phyfician in Jamaica.

The production of thefe nets is indeed a part of
the nature or conformation of the animal, and their
natural ufe is to fupply the place of wings, when
flic vufhes to remove to another fituation. But
when flie employs them to entangle her prey, there
are marks of evident defign, for me adapts the form
of each net to its fituation, and flrengthens thofe
lines, that require it, by joining others to the mid-
dle of them, and attaching thole others to diflant
objects, with the fame individual ait, that is ufed
by mankind in fupporting the mads and extending
the fails of mips. This work is executed with
more mathematical exa&nefs and ingenuity by the
field fpiders, than by thofe in our houfes, as their
conftrucYions are more fubjected to the injuries of
dews and tempefts.

Befides the ingenuity fhewn by thefe little crea-
tures in taking their prey, the circumftance of their
counterfeiting death, when they are put into ter-
ror, is truly wonderful ; and as foon as the objecl:
of terror is removed, they recover and run away.
Some beetles are allo faid to poffefs this piece of
hypocrify.

The curious webs, or chords, conftru&ed by fome
young caterpillars to defend themfelves from cold,
or from infects of prey ; and by illk-worms and
fome other caterpillars, when they tranfmigrate into
aurelias or larvx, have defervedly excited the ad-
miration of the inquifitive. But our ignorance of
their manner of life, and even of the number of
fheir fenfcs, totally precludes us from underfland-

ing

si* OF INSTINCT. «ccT,XVI.i5.

ing the means by which they acquire this know-
ledge.

The care of the falmon in choofing a proper
Situation for her fpawn, the ftruclure of the nefts
*>f birds, their patient incubation, and the art of
the cuckoo in depofiting her egg in her neighbour's
jmrfery, are inftances of great fagacity in thole
creatures : and yet they are much inferior to the
arts exerted by many of the infe6t tribes on fimilar
occafions. The hairy excrefcences on briars, the
oak apples, the blafted leaves of trees, and the
lumps on the backs of cows, are fituations that
are rather produced than, chofen by the mother in-
fed for the convenience of her offspring. The
cells of bees, waips, fpiders, and of the various
coralline infects, equally aftonim us, whether we
attend to the materials or to the architecture.

But the conduct of the ant, and of iorne fpecies
of the ichneumon fly in the incubation of their
eggs, is equal to any exertion of human fcicnce.
The ants' many times in a day move their eggs
Dearer the furface of their habitation, or deeper be*
low it, as the heat of the weather varies ; and ia
colder days lie upon them in heaps for the purpofe
of incubation ; if their manfion is too dry, they
carry them to places where there is moifture, and
you may diftinclly fee the little worms move and
£ick up the water. When too much moifture ap-
proaches their neft, they convey their eggs deeper
in the earth, or to fome other place of fafety,
(Swammerd. Epil. ad Hift. Infects, p. 153. Phil,
Jranf. No. 23. Lowthorp, V. 2. p. 7.)

There is one fpecies of ichneumon-fly, that digs
a hole in the earth, and carrying into it two or three
living caterpillars, depofits her eggs, and nicely
clofing up the neft leaves them there ; partly doubt-
lefs to ajlift the incubation, and partly to fupply

food

IBBCT.XVI.i6. OF INSTINCT. 213

food to her future young, (Derham. B. 4. c. 13,
Arift-.>tlc Hift. Animal, L. 5. c. 20. V

A friend of mine put about fifty large caterpil-
lars collected fro HI cabbages on iome bran and a
few leaves Litt.. a. box, and covered it with gauze
to p. event dieir elcape. After a few days we law,
from moix rvm three: fourths of them, about eight
or ten Htri, aterpillars of the ichneumon-fly come
out of the-.r backs, arid Jpni coch a fmall cocoon of
filk, ai. ' in a few days the large caterpillars died.
This fruail fly it feems lavs it$ egg in the back of
the cabbage caterpillar, which when hatched preys
u; >n 'he material, which is produced there for the
purpose of irrakin- filk for the future neft of the
cabbage caterpillar; of which being deprived, the
cr.amre wa'nders about till it dies, and thus our
gardens are preferred by the ingenuity of this cruel
fly* This curious property of producing a filk
thread, which is common to fome Tea animals, fee
Botanic Garden, Part I. Note XXVII and is de-
figne-j for tne purpole of their transformation as
in the filk- worm, is ufed for conveying themfelves
from higher o^anches to lower ones of trees by fome
caterpillars, and to make themfelves temporary
nelts or tents, and by the fpider for entangling his
prey Nor is it flrange that fo much knowledge
Ihould !>e acquired by iuch fmall animals ; fmce
there is rei-ion to imagine, that thefe infecls have
the fenfe of touch, either in their probofcis, or their
antennae, to a great degree of perfection ; and
thence may poflefs, as far as their fphere extends,
as accurate knowledge, and fubtile invention, as
the difcoverers of human arts

XVI. i. If we were better acquainted with the
hiftories of thofe infecls that are iurmcd into foci-
eties, as the bees, wafps, and ants, I make no
doubt but we mould find, that their arts and im-
provements arc not fo fimilar and uniform as they

now

O F I N S T I N C T. S«CT. XVI. 16.

now appear to us, but that they arofe in the fame
manner from experience and tradition, as the arts
of our own fpecies ; though their reafoning is from
fewer ideas, is bufied about fewer objects, and is
exerted with lefs energy.

There are fome kinds of infects that migrate like
the birds "before mentioned. The locuft of warmer
climates has. fometimes come over to England ; it
is fliaped like a grafshopper, with very large wings,
and a body above an inch in length. It is menti-
oned as coming into Egypt with an eaft wind,
" The Lord brought an eaft wind upon the land
all that day and night, and in the morning the eaft
wind brought the locuils, and covered the face of
the earth, fo that the land was dark/' Exod. x. 13.
The emigrations of thefe infects are mentioned in
another part of the fcripture, <4 The locufts have
no kipgj yet go they forth all them in bands."
Prov xxx. 27.

The accurate Mr. Adanfon, near the river Gam-
bia in Africa, was witnefs to the migration of thefe
infects. " About eight in the morning, in the
jnonth of February, there iuddenly aroie over our
heads a thick cloud., which darkened the air, and
deprived us of the rays of the fun. We found it
vras a cloud of locufts raifed about twenty or thirty
fathoms from the ground, and covering an extent
of feveral leagues ; at length a ihower of thefe in-
fects defcended, and after devouring every green
herb, while they refted, again refumed their flight.
This cloud was brought by a ftrong eail-wind, and
was all the morning in palling over the adjacent
country/' (Voyage to Senegal, 158)^

In this country the gnats are fometimes feen to
migrate in clouds, like the mufketoes of warmer
climates, and our fwarrns of bees frequently travel
many miles, and are faid in North America always
to fly towards .the fouth. The prophet Ifaiah has a

beautifu}

SECT. XVI. 1 6. OFINSTINCf. *.\$

beautiful allufion to thefe migrations, cc The Lord
fhall call the fly from the rivers of Egypt, and (hall
hifs for the bee that is in the land of Affyria,"
lla. vii. 1 5. which has been lately explained by
Mr. Bruce, in his travels to difcover the fource of
the Nile.

2. I am well informed that the bees that were
carried into Barbadoes, and other weftern iflands,
ceafed to lay up any honey after the firft year, a*
they found it not ufeful to them : and are now be-
come very troublefome to the inhabitants of thofc
iflands by infefting their fugar-houfes ; but thofe in
Jamaica continue to make honey, as the cold north
winds, or rainy feafons of that ifland, confine them
at home for feveral weeks together. And the bees
of Senegal, which differ from thofe of Europe only
in fize, make their honey not only fuperior to ours
in delicacy of flavour, but it has this fmgularity,
that it never concretes, but remains liquid as fyrup,
(Adanfon). From fome obfcrvations of Mr. Wild-
man and of other people of veracity, it appears,
that during the fevere part of the winter feafon for
weeks together the bees are quite benumbed and
torpid from the cold, -and do not confume any of
their provifion. This itate of fleep, like that of
fwallows and bats, feems to be the natural refourcer
of thole creatures in cold climates, and the making
of honey to be an artificial improvement.

As the death of our hives of bees appears to be
owing to their being kept fo warm, as to require
food when thdr flock is exhaufted ; a very obferv-
ing gentleman at my requeft put two hives for many
weeks into a dry cellar, and obferved, during alt
that time,, they did not confume any of their pro-
vifion, for their weight did not decreafe, as it had
done when they were kept in the open air. The
lame obfervation is made in the Annual Regifter for
A/68. p. 113. And the Rev. Mr. "White, in his-

Method

*'6 OF INSf iMCT. SEcf.XVI.,5.

Method of preferring Bees, adds, that thofe on
the north fide of his houfe confumed lefs honey in
the winter than thofe on the fouth fide.

There is another obfervatiori on bees well afcer-
tained, that they at various times, when the feafon
begins to be cold, by a general motion of their legs
as they hang in clufters produce a degree of wSrmth^
which is eafily perceptible by the hand. Hence by
this ingenious exertion, they for a long time pre-
vent the torpid (late they would naturally fall
into.

According to the late obfefvations of Mr. Hun-
ter, it appears that the bees-wax is not made front
the duft of the anthers of flowers, which they bring
home on their thighs, but that this makes what is
termed bed-bread, and is ufed for the purpofe of
feeding the bee-maggots ; in the fame manner but-
terflies live on honey, but the previous caterpillar
lives on ^vegetable leaves, while the maggots of
large flies require flefh for their food$ and thofe of
the ichneumon fly require infects for their food*
What induces the bee who lives on honey to lay
up vegetable pbwder for its young ? What induced
trie butterfly to lay its eggs on leaves, when itfelf
feeds on honey? What induces the other flies tb
feek a food for their progeny different from what
they confume themfelves ? If thefe are not deduc-
tions from their own previous experience or obfer-
vation, all the aftions of mankind mufl be refolved
into inftinct.

3* The dormoufe con fumes but little of its food
during the rigour of the feafon, for they roll them-
felves up, or fleep, or lie torpid the greater}, part
of the time ; but on warm funny days experience
a ihort revival, and take a little food, and then
relapfe into their former ftate." (Pennant Zbblog.
p» 67*) Other animals^ that fleep in winter with-
out laying up any provender, are obferved to go

into

. 1 6. OF INSTINCT. 217

into their winter beds fat and flrong, but return
to day-light in the fpring feafon very lean and fee-
ble. The common flies ileep during the winter
without any provifion for their nourifhment, and
are daily revived by the warmth of the fun, or of
our fires. Thefe whenever they fee light endea-
vour to approach it, .having obferved, that by its
greater vicinity they get free from the degree of
torpor that the cold produces ; and are hence in-
duced perpetually to burn themfelves in our can-
dles : deceived, like mankind, by the mifapplica-
tionof their knowledge, Whiift many of the fub-
terraneous infects, as the common worms, feem to
retreat fo deep into the earth as not to be enlivened
or awakened by the difference of our winter days ;
and (top up their holes with leaves or draws, to
prevent the frofts from injuring them, or the cen-
tipes from devouring them. The habits of peace,
or the ftratagems of war, of thefe fubterranean na-
tions are covered from our view; but a friend of
mine prevailed on a diftreiled worm to enter the
hole of another worm on a bowling-green, and he
prefently returned much wounded about his head.
And I once faw a worm rife haftily out of the earth
into the funfhine, and obferved a centipes hanging
at its tail ; the centipes nimbly quitted the tail,,
and feizing the worm about its middle, cut it in
half with its forceps, and preyed upon one party
while the other efcaped. Which evinces they have
defign in (lopping the mouths of their habitations.

4. The wafp of this country fixes his habitation
under ground, that he may not be affected with the
various changes of our climate ; but in Jamaica he
hangs it on the bough of a tree, where the feafons
are lefs fevere. He weaves a very curious paper of
vegetable fibres to cover his neft, which is con-
ftructed on the fame principle with that of the bee,
but with a different material \ but as his prey con-

fiffe

M OF INSTINCT. SECT. XVf. i&

fifts of flefh, fruits, and infers, which are perifha-
b!e commodities, he can lay up no provender for
the winter.

M. de Loubiefe, in his relation of Siam, fays,
*c That in a part of that kingdom, which lies open
to great inundations, all the ants make their fcttle-
ments upon trees ; no ants' neiis are to be feen any
where elfe." Whereas in our country the ground
is their only fituation. From the fcriptural account
of thefe infects, one might be led to fufpect, that in
fome climates they lay up a provifion for the win-
ter. Origen affirms the fame, v(Cont. Celf. L. 4.^
But it is generally believed that in this country they
do not, (Prov. vi. 6. xxx. 25.) The white ants of
the coaft of Africa make themfelves pyramids eight
or ten feet high, on a bafe of about the fame width,
with a fmooth furface of rich clay, exceflively hard
and well t^uilt, which appear at at a diftance like an
aifemblage of the huts of the negroes, (Adanfon.)
The hiftory of thefe has been lately well defcribed
in the Philofoph. Tranfaccions, under the name of
termes, or termites. Thefe differ very much from
the neft of our large ant ; but the real hiftory of
this creature, as well as of the wafp, is yet very
imperfectly known.

Wafps are faid to catch large fpiders, and to cut
off their legs, and carry their mutilated bodies to
their young, Dicl. Raifon. Tom. I. p. 152.

One circumllance I fhall relate which fell under
my own eye, and (hewed the power of reafon in a
wafp, as is it exercifed among men. A wafp, on
a gravel walk, had caught a fly nearly as large as
himfelf ; kneeling on the ground I obferved him
feparate the tail and the head from the body parr,
to which the wings were attached. He then took
the body part in his paws, and rofe about two feet
from the ground with it ; but a gentle breeze waft-
ing the wings of the fly turned him round in the

;- OF INSTINCT. 219

air, and he fettled again with his prey upon the
gravel. I then diftinctly obferved him cut off with
his mouth, firft one of the wings, and then the
other, after which he flew away with it unmolefted
by the wind.

Go, thou fluggard, learn arts and induftry from
the bee, and from the ant !

Go proud reafoner, and call the worm thy fifter!

XVII Conclufton.

It was before obferved how much the fuperior
accuracy of our fenfe of touch contributes to increafe
our knowledge; but it is the greater energy and
activity of the power of volition fas explained in
the former Sections of this workj that marks man-
kind, and has given him the empire of the world.

There is a criterion by which we may diftinguifh
our voluntary acts or thoughts from thofe that are
excited by our fenfations : " The former are al-
ways employed about the means to acquire plea-
furable objects, or to avoid painful ones : while the
latter are employed about the poffeffion of thofe that
are already in our power."

If we turn our eyes upon the fabric of our fel-
low animals, we find they are fupported with bones,
covered with {kins, moved by mufcles ; that they
poffefs the fame fenfes, acknowledge the fame ap-
petites, and are nourifhed by the fame aliment with
ourfelves ; and we mould hence conclude from the
ftrongeft analogy, that their internal faculties were
alfo in fome meafure fimilar to our own,

Mr. Locke indeed publifhed an opinion, that
other animals pofiefled no abftract or general ideas,
and thought this circumflance was the barrier be-
tween the brute and the human world. But thefe
abftra&ed ideas have been fince demonftrated by
. I, ( Biihpp

OF INSTINCT.

Bifliop Berkley, and allowed by Mr. Hume, to
have no exigence in nature, not even in the mind
«f their inventor, and we are hence neceffitated to
look for fome other mark of diftin&ion.

The ideas and actions of brutes, like thofe of
children, are almoft perpetually produced by their
prefent plcafures, or their prefent pains ; and, ex-
cept in the few inftances that have been mentioned
in this Section, they feldom bufy themfelves about
the means of procuring future blifs, or of avoiding
future mifery.

Whilft the acquiring of languages, the making
of tools, and the labouring for money ; which are
all only the means of procuring pleafure : and the
praying to the Deity, as another means to procure
happinefs, are chara&eriftic of human nature.

.

SECT,

SecT.XVH. i. CATENATION OF MOTIONS, 221
SECT. XVII.

THE CATENATION OF MOTIONS,

I. i. Catenations of animal motion. 2. Are pw-
duced by irritations^ by fenfations, by volitions*
3. They continue fome time after they bait been ex-
cited. Caufe of catenation. 4. We can then exert
eur att-ention on other objects. 5. Many catenations
of motions go on together. 6. Some links of the
catenations of motions may be left out without dif-
uniting the chain. 7. Interrupted circles of motion
continue confufedly till they come to the part of the
Circle ', where they were dijlurbed. 8. Weaker ca-
tenations are diJJ.evered by flronger. 9. Then new
catenations take place. 10. Mitch effort prevents
their reuniting. Impediment of fpeech. 1 1. Trains
more eafily diffevered than circles. 12. Sleep
deftroys volition and external ftimulus. II. 7«-
flanccs of various catenations in a "sung lady play-
ing on the harpjichord, HL \.V\} hat catenations are
the Jlrongeft. %. Irritations joined with affociations
from Jlronge ft connexions, Vital motions. 3. New
links with increafed force ', cold fits of fever produced.

4. New links with decreafed force. Cold bath,

5. Irritation joined with fenfation. Inflammatory
fever. Why children cannot tickle themfefaes*

6. Volition joined with fenfation. Irritative ideas
of found become fenfible. 7. Ideas of imagination
^dijevered by irritation, by volition, production of

furprife.

I. i. To inveftigate with precifion the catena*
tions of animal motions, it would be well to attend
£9 the manner pf their production : but we cannot

begin

222 CATENATION OF MOTIONS SECT. XVII' i;

begin this difquifition early enough for this purpofe,
as the catenations of motion feem to begin with
life, and are only extinguifhable with it. We have
fpoken of the power of irritation, of fenfation, of
volition, and of aflbciation, as preceding the fibrous
motions ; we now ftep forwards, and confider, that
converfely they are in their turn preceded by thofe
motions ; and that all the fucceffive trains or cir-
cles of our actions are compofed of this twofold
concatenation. Thofe we fhall call trains of ac-
tion which continue to proceed without any flared
repetitions ; and thofe circles of a&ion, when the
parts of them return at certain periods, though the
trains of which they confift, are not exaclly fimi-
Jar. 'The reading an epic poem is a train of ac-
tions ; the reading a fong with a chorus at equal
diftances in the meafure conflitutes fo many circles
of action.

2. Some catenations of animal motion are pro-
duced by reiterated fucceffive irritations, as when
we learn to repeat the alphabet in its order by fre-
quently reading the letters of it. Thus the vermi-
cular motions of the bowels were originally pro-
duced by the fucceffive irritations of the paffing
aliment ; and the fucceflion of actions of the auri-
cles and ventricles of the heart was originally form-
ed by fucceffive flimulus of the blood, thefe after-
wards become part of the diurnal circles of animal
actions, as appears by the periodical returns of
hunger, and the quickened pulfe of weak people in
the evening.

Other catenations of animal motion are gradually
acquired by fucceffive agreeable fenfations, as in
learning a favourite fong or dance ; others by dif-
agreeable fenfations, as in coughing or ni&itation ;
thefe become aflbciated by frequent repetition, and
afterwards compofe parts of greater circles, of ac-
tion like thofe above mentioned.

Other

ECT. XVIL i. CATENATION OF MOTIONS. 223

Other catenations of motions are gradually ac-
quired by frequent voluntary repetitions ; as when
\ve deliberately learn to march, read, fence, or any
mechanic art, the motions of many of our mufcles
become gradually linked together in trains, tribes,
or circles of aclion. Thus when any one at firft
begins to ufe the tools in turning wood or metals
ia a lathe, he wills the motions of his hand or fin-
gers, till at length thefe actions become fo connected
with the effect, that he feems only to will the point
of the chifiel. Thefe are caufed by volition, con-
nected by aflbciation like thofe above defcribed, and
afterwards become parts of our diurnal trains or
circles of action.

3. All thefe catenations of animal motions are li-
able to proceed fome time after they are excited, un-
lefs they are diflurbed or impeded by other irrita-
tions, fenfations, or volitions ; and in many in-
flances in fpite of our endeavours to flop them ;
and this property of animal motions is probably the
caufe of their catenation. Thus when a child re-
volves fome minutes on one foot, the fpeclra of
the ambient objects appear to circulate round him
fome time after he falls upon the ground. Thus
rhe palpitation of the heart continues fome time
after the object of fear, which occafioned it, is re-
moved. The blufh of fhame, which is an excefs
of fenfation, and the glow of anger, which is an
excefs of volition, continue fome time, though the
affected perfon finds, that thofe emotions were
caufed by miftaken facts, and endeavours to ex-
tinguifh their appearance. See Sect. XII. i. 5.

4. When a circle of motions becomes connected
by frequent repetitions as above, we can exert our
attention ftrongly on other objects, and the conca-
tenated circle of motions will nevertheless 'proceed
in due order ; as whilfl you are thinking on this

fubjects,

2*4 CATENATION OF MOTIONS. SECT. XVIt r.

fubjedt, you ufe variety of mufcles in walking about
your parlour, or fitting at your writing table.

5. Innumerable catenations of motions may pro-
ceed at the fame time, without incommoding each
other. Of thefe are the motions of the heart and
arteries ; thofe of digeftion and glandular fecre-
vion j of the ideas, or fenfual motions ; thofe of
progreffion, and of fpeaking ; the great annual cir-
cle of actions fo apparent in birds in their times
of breeding and moulting ; the monthly circles of
many female animals ; and the diurnal circles of
Seeping and waking, of fulnefs and inanition*

6. Some links of fucceffive trains or of fynchron-
©us tribes of action may be left out without disjoin-
ing the whole. Such are our ufual trains of recol-
lection ; after having travelled through an enter-
taining country, and viewed many delightful lawnsr
rolling rivers, and echoing rocks ; in the recollec-
tion of our journey we leave out the many dittricts,.
that we crofTed, which were marked with no pecu-
liar pleafure. Such alfo are our complex ideas,
they are catenated tribes of ideas, which do not
perfectly refembie their correfpondent perceptions*
becaufe fome of the parts are omitted.

7. If an interrupted circle of actions is not en-
tirely diflevered, it will continue to proceed con-
fufedly, till it comes to the part of the circle,
where it was interrupted.

The vital motions in a fever from drunkcnnefs,,
and in other periodical difeafes, are inftances of
this circumftance. The accidental inebriate does
not recover himfelf perfectly till about the fame
hour on the fucceeding day.. The accuftomed:
drunkard is disordered, if he haa not his ufual
potation of fermented liquor. So if a confiderable
part of a connected tribe of action be difturbed,
that whole tribe goes on with confufion, till the
part of the tiibe affected regains its accuftomed ca-
tenations..

Stcr. XVII. i. CATENATION OF MOTIONS. 225

tenations. So vertigo produces vomiting, and a
great fecretion of bile, as in fea-ficknefs, all thefe
being parts of the tribe of irritative catenations.

8. Weaker catenated trains may be diffevered
by the fudden exertion of the (Ironger. When a
child firft attempts to walk acrofs a room, call to
him, and he inftantly falls upon the ground. So
\vhile I am thinking over the virtues of my friends,
if the tea-kettle fpurt out fome hot water on my
flocking ; the fudden pain breaks the weaker chain
of ideas,, and introduces a new group of figures of
its own. This circumflance is extended to fome
unnatural trains of action, which have not been
confirmed by long habit ; as the hiccough, or an
ague-fit, which are frequently curable by iurprife.
A young lady about eleven years old had for five
days had a contraction of one mufcie in her fore
arm, and another in her arm, which occurred four
or five times every minute ; the mufcies were feen
to leap, but without bending the arm. To coun-
teract this new morbid habit, an iflue was placed
over the convulfed mufcie of her arm, and an
adhefive plafter wrapped tight like a bandage over
the whole fore arm, by which the new motion*
were immediately deflroyed, but the means were
continued fome weeks to prevent a return.

9. If any circle of actions is difTevered, either
by omiflion of fome of the links, as in fleep, or
by infertion of other links, as in furprife, new ca-
tenations take place in a greater or lefs degree.
The lad link of the broken chain of actions be-
comes connected with the new motion which has
broken it, or with that which was neareit the link
omitted ; and thefe new catenations proceed inftead
of the old ones. Hence the periodic returns of
ague-fits, and the chimeras of our dreams.

10. If a train of actions is diflevered, much ef-
fort of volition or fenfation will preveju its being

reftored.

226 CATENATION OF MOT IONS. SECT, xvrl 2.

reftored. Thus in the common impediment of
fpeech, when the aflbciation of the motions of the
mufcles of enunciation with the idea of the word
to be fpoken is difordered, the great voluntary ef-
forts, which diftort the countenance, prevent the
rejoining of the broken aflbciations. See No. II.
ip. of this Section. It is thus likewife obfervable
in fome inflammations of the bowels, the too flrong
efforts made by the mufcles to carry forward the
offending material fixes it more firmly in its place,
and prevents the cure. So in endeavouring to re-
cal to our memory fome particular word of a fen-
tence, if we exert ourfelves too ftrongly about it,
we are lefs likely to regain it.

1 1 . Catenated trains or tribes of action are eafier
diflevered than catenated circles of action. Hence
in epileptic fits the fynchronous connected tribes of
action, which keep the body erect, are diffevered,
but the circle of vital motions continues undifturb-
cd.

12. Sleep deitroys the power of volition, and
precludes the flimuli of external objects, and thence
difievers the trains, of which thefe are a part;
which confirms the other catenations, as thofe of
the vital motions, fecretions, and abforptions ; and
produces the new trains of ideas, which constitute
our dreams.

II. i. All the preceding circumflances of the
catenations of animal motions will be more clearly
underftood by the following example of a perfon
learning mufic ; and when we recollect the variety
of mechanic arts, which are performed by aflbciated
trains of mufcular actions catenated with the effects
they produce, as in knitting, netting, weaving ;
and the greater variety of affociated trains of ideas
caufed or catenated by volitions or fenfations, as in

our

&CT. XVI. 2. CATENATION OF MOT IONS.

our hourly modes of reafoning, or imagining, or
recolle&ing, we (hall gain fome idea of the innu-
merable catenated trains and circles of aclion, which
form the tenor of our lives, and which began, and
will only ceafe entirely with them.

2. When a young lady begins to learn mufic, flic
voluntarily applies herfelf to the characters of her
mufic-book, and by many repetitions endeavours to
catenate them with the proportions of found, of
which they are fymbols. The idea excited by the
mufical characters are ilowly connected with the
keys of the harpfichord, and much effort is necef-
fary to produce every note with the proper finger,
and in its due place and time ; till at length a traia
of voluntary exertions becomes catenated with cer-
tain irritations. As the various notes by frequent
repetitions become connected in the order, in which
they are produced, a new catenation of fenfitive
exertions becomes mixed with the voluntary ones
above defcribed ; and not only the mufical fymbols
of crotchets and quavers, but the auditory notes
and tones at the fame time, become fo many fuc-
ceffive or fynchronous links in this circle of cate-
nated actions.

At length the motions of her fingers become ca-
tenated with the mufical characters ; and thefe no
fooner ftrike the eye, than the finger prefles down,
the key without any voluntary attention between
them : the activity of the hand being connected
with the irritation of the figure or place of the
mufical fymbol on the retina ; till at length by fre-
quent repetitions of the fame tune the movements
of her fingers in playing, and the mufcles of the
larynx in finging, become aflbciated with each
other, and form part of thofe intricate trains and
circles of catenated motions, according with the fe-
cond article of the preceding propofidons in No. i.
of this Section.

3, Befides

22S CATENATION OF MOTIONS. SECT. XVII. i-

3. Befides the facility, which by habit attends
the execution of this mufical performance, a curi-
ous circumftance occurs, which is, that when our
young mufician has begun a tune, me finds herfelf
inclined to continue it 5 and that even when (he is
carelefsly finging alone without attending to her
own fong ; according with the third preceding
article.

4. At the fame time that our young performer
continues to play with great exaclnefs this accuf-
tomed tune, me can bend her mind, and that in-
tenfely, on forfte other object, according with the
fourth article of the preceding propofitions.

The manufcript copy of this work was lent to
many of my friends at different times for the pur-
pofc of gaining their opinions and criticifms on
many parts of it, and I found the following anec-
dote written with a pencil opofite to this page,
but am not certain by whom. " I remember fee-
ing the pretty young actrefs, w;ho fucceeded Mrs*
Arne in the performance of the celebrated Pad-
lock, rehearfe the mufical parts at her harpfichord
under the eye of her matter with great tafte and
accuracy ; though I obferved her countenance full
of emotion, which I could not account for ; at laft
flic fuddenly burft into tears ; for (he had all this
time been eyeing a beloved canary bird, fuffering
great agonies, which at that inftant fell dead from
its perch."

5. At the fame time many other catenated circles
of action are going on in the perfon of our fair
mufician, as well as the motions of her fingers, fuch
as the vital motions, refpiration, the movements of
her eyes and eyelids, and of the intricate mufcles
of vocality, according with the fifth preceding
article.

6. If by any ftrong impreflion on the mind of
our fair mufician fhe fhould be interrupted for a

very

SECT. XVII. 2. CATENATION OF MOTIONS. 229

very inconfiderable time, (he can dill continue her
performance, according to the fixth article.

7. If however this interruption be greater,
though the chain of actions be not diiTevered, it
proceeds confufedly, and our young performer
continues indeed to play, but in a hurry without
accuracy and elegance, till fhe begins the tune a-
gain, according to the feventh of the preceding ar-
ticles,

8. But if this interruption be ftjll greater, the
circle of actions becomes entirely diffevered, and
fhe finds herfelf immediately under the neceility Co
begin over again to recover the loft catenation, ac-
cording to the eighth preceding article.

9. Or in trying to recover it fhe will fing fome
diifonant notes, or ftrike fomc improper keys, ac-
cording to the ninth preceding article.

10. A very remarkable thing attends this breacli
of catenation, if the performer has forgotten
fome word of her fong, the more energy of
mind me ufes about it, the more diftant is fhe
from regaining it ; and artfully employs her mind
in part on fome other object, or endeavours to
dull its perceptions, continuing to repeat, as h
were inconfciouily, the former part of the fonga
that me remembers, in hopes to regain the loft co»-
aexion.

For if the activity of the mind itfelf be more
energetic, or takes its attention more, than the
connecting word, which is wanted ; it will not per-
ceive the flighter link of this loft word ; as who
liftens to a feeble found, muft be very filent and
motionlefs ; fo that in this cafe the very vigour of
the mind itfelf feems to prevent it from regaining
the loft catenation, as well as the too great exer-
tion in endeavouring to regain it, according to the
tenth preceding article*

We

*$v CATENATION OF MOTIONS. SECT. XVlf 5.

We frequently experience, when we are doubt-
ful about the fpelling of a word, that the greater
voluntary exertion we ufe, that is the more intenfely
xve think about it, the further are we from regain-
ing the loft affociation between the letters of it,
but which readily recurs when we have become
careiefs about it. In the fame manner, after hav-
ing for an hour laboured to recollect the- name
of fome abfent perfon, it (hall feem, particularly
after fleep, to come into the mind as it were fpon-
taneoufly ; that is, the word we are in fearch of,
was joined to the preceding one by affociation ;
this affociation being diffevered, we endeavour to
recover it by volition; this very action of the
mind (trikes our attention more, than the faint
link of adbciation, and we find it impoffible by this
means to retrieve the loft word. After fleep, when
volition is entirely fufpended, the mind becomes
capable of perceiving the fainter link of affociation,
and the word is regained.

On this circumftance depends the impediment of
fpeech before mentioned ; the firft fyllable of a word
i& caufable by volition, but the remainder of it is in
common converfation introduced by its affociations
with this firft fyllable acquired by long habit. Hence
when the .mind of the ftammerer is vehemently em-
ployed en fome idea of ambition of fhining, or fear
of not fucceeding,- the aflbciations of the motions
of the muicies or articulation with each other be-
come diflevered by this greater exertion, and he en-
deavours in vain by voluntary efforts to rejoin the
- broken afibciation. For this purpofe he continues
to repeat the fiift fy liable, which is caufable by vo-
lition, and drives in vain, by various diftortions of
countenance, to produce the next links, which are
fubjedt to affociation. See Clafs IV. 3, I. i.

1 1 . After our accomplilhed mufician has acquired
great variety of tunes and fongs, fo that fome of

them

. 2. CATENATION OF MOTIONS. 23;

them begin to ceafe to be eafily recollected, fhc
finds progreffive trains of mufical notes more fre-
quently forgotten, than thofe which are compofed
of reiterated circles, according with the eleventh
preceding article.

12. To finifh our example with the preceding ar-
ticles we muft at length fuppofe, that our fair per-
former falls afleep over her harpfichord ; and thus
by the fufpenfion of volition, and the exclufion of
external ftimuli, fhe diflevers the trains and circles
of her muficai exertions.

III. i. Many of thefe circumftances of catenati-
ons of motions receive an eafy explanation from the
four following confequences to the feventh law of
animal caufation in Seel. IV. Thefe are, firft, that
thofe fucceflions or combinations of animal motions,
whether they were united by caufation, aflbciation,
or catenation, which have been mod frequently re-
peated, acquire the flrongeft connection. Secondly,
that of thefe, thofe, which have been lefs frequently
mixed with other trains or tribes of motion, have the
ftrongeft connection. Thirdly, that of thefe, thofe,
which were firit formed, have the ftrongeft connecti-
on. Fourthly, that if an animal motion be excited
by more than one caufation, aflbciation, or catena-
tion, at the fame time, it will be performed with
greater energy.

2. Hence alfo we under (land, why the catenati-
ons of irritative motions are more ftrongly connect-
ed than thofe of the other clafles, where the quan-
tity of unmixed repetition has been equal ; becaufe
they were firft formed. Such are thofe of the fe-
cerning and abforbent fyftems of veflels, where the
action of the gland produces a fluid, which ftimu-
lates the mouths of its correfpondent abforbents.
The aflbciated motions feem to be the next mod
ilrongly united, from their frequent repetition , and
where both thefe circumftances unite, as in the vital

motions

*J2 CATENATION OF MOTIONS. SECT. XVII. 3.

motions, their catenations are indiflbluble but by
the deftru&ion of the animal.

3. Where a new link has been introduced into a
circle of a&ions by fome accidental defect of ftimu-
lus ; if that, defect of flimulus be repeated at the fame
part of the circle a fecond or a third time, the defec-
tive motions thus produced, both by the repeated
jdefecl: of flimulus and by their catenation with the
parts of the circle of actions, will be performed with
lefs and lefs energy. Thus if any perfon is expofed
to cold at a certain hour to day, fo long as to render
fome part of the fyftem for a time torpid ; and is
again expofed to it at the fame hour to-morrow, and
the next day ; he will be more and more affecled by
it, till at length a cold fit of fever is completely form-
ed, as happens at the beginning of many of thofe
fevers, which are called nervous or low fevers.
Where the patient has flight periodical (hiverings
and palenefs for many days before the febrile pa-
roxyfm is completely formed*

4. On the contrary, if the expofure to cold be for
To fhort a time, as not to induce any confiderable
cFegree of torpor or rjuiefcepce, and is repeated
daily as above mentioned, it lofes its effect more
and more at every repetition, till the conftitution
can bear it without inconvenience, or indeed with-
out being confcious of it. As in walking into the
cold air in frofty weather. The fame rule is appli-
cable to increafed ftimulus,'as of heat, or of vinous
fpirit, within certain limits, as is applied in the two
laft paragraphs to Deficient Stimulus, as is further
explained in Sed. XXXVI. on the Periods of DifV
cafes.

5. Where irritation coincides with fenfation to
produce the fame catenations of motion, as in inflam-
matory fevers, they are excited with (till greater
energy than by the irritation alone. So When chiU
dren expeft to be tickled in play, by a feather light-
ly paffed over the lips, or by gently vellicating the

foles

SICT. XVII. 3. CATENATION OF MOTIONS. 233

foles of their feet, laughter is moft vehemently ex-
cited ; though they can ftimulate thefe parts with
their own fingers unmoved. Here the pleafurable
idea of playfulnefs coincides with the vellication ;
and there is no voluntary exertion ufed to diminifh
the fenfation, as there would be, if s. child fhould
endeavour to tickle himfelf. See Seel:. XXXIV*

i. 4-

6. And lafHy, the motions excited by the junc-
tion of voluntary exertion with irritation are per-
formed with more energy, than thofe by irritation
fingly ; as when we liften to fmall noifes, as to the
ticking of a watch in the night, we perceive the
moft weak founds, that are at other times unheeded.
So when we attend to the irritative ideas of found in
our ears, which are generally not attended to, we
can hear them ; and can fee the fpeclra of objects,
which remain in the eye, whenever we pleafe to ex-
ert our voluntary power in aid of thofe weak actions
pf the retina, or of the auditory nerve.

7. The temporary catenations of ideas, which
are caufed by the fenfations of pleafnre or pain, are
eafily diflevered either by irritations, as when a fud-
den noife difturbs a day-dream ; or by the power of
volition, as when we awaken from fleep. Hence in
our waking hours, whenever an idea occurs, which
is incongruous to our former experience, we in-
ftantly diflever the train of imagination by the
power of volition, and compare the incongruous idea
with our previous knowledge of nature, and reject
it. This operation of the mind has not yet acquired
a fpecific name, though it is exerted every minute
of our waking hours ; unlefs it may be termed
INTUITIVE ANALOGY. It is an aft of reafoning of
which we- are unconfcious except from its effects in
preferving the congruity of our ideas, and bears the
fame relation to the fenforial power of volition, that
irritative ideas, of which we are unconfcious except

by

CATENATION OF MOTIONS. SECT. XVIII. 5

by their effe&s, do to the fenforial power of irritati-
on ; as the former is produced by volition without
our attention to it, and the latter by irritation with-
out our attention to them.

If on the other hand a train of imagination or of
voluntary ideas are excited with great energy, and
paffing on with great vivacity, and become difiever-
ed by fome violent ftimulus,. as the difcharge of a
piftol near one's ear* another circumftance takes
place, which is termed SURPRISE; which by ex-
citing violent irritation, and violent fenfation, em-
ploys for a time the whole fenforial energy, and thus
diflevers the pafling trains of ideas, before the pow-
er of volition has time to compare them with the
jifual phenomena of nature. In this cafe fear is
generally the companion of furprife, and adds to
our embarraflment, as every one experiences in
fome degree when he hears a noife in the dark,
which he cannot inftantly account for. This cate-
nation of fear with furprife is owing to our perpetual
experience of injuries from external bodies in moti-
on, unlefs we are upon our guard againft them. See
Sett. XVIII. 17. and XIX. %.

Many other examples of the catenations of animal
motions are explained in Se&. XXXVI. on the Peri-
04s of Difeafes.

SECT.

. XVIII. OF S L E E P. 235

SECT. XVIII.

OF SLEEP.

i; Volition is fufpended in ficcp. 2. Senfation conti-
nues. Dreams prevent delirium and inflammation.
3- Nightmare. 4. Ceafe lefs flow of ideas in dreams.
5. We feem to receive them by the fenfes. Optic
nerve perfectly fenfibk in Jleep. Eyes lefs dazzled
after dreaming of vifible objecls. 6- Reverie, be-
lief. 7. How we diflinguijh ideas from percepti-
ons. 8. Variety of fcenery in dreams, excellence of
the fenfe of vifton. 9. Novelty of combination in
dreams. 10. Dijttriftnefs of imagery in dreams.
n. Rapidity of traufaftion in dreams. 12. Of
meafuring time. Of dramatic time and place.
Why a dull play induces Jleep, and an interefting
one reverie. 13. Confcioiifnefs of our exigence and
identity in dreams. 14. How we awake fometinws
fuddenly, fometimes frequently. 15. Irritative mo-
tions continue in Jleep , internal irritations are fuc~
cceded by fenfation. Senfibility increases during
fleep, and irritability. Morning dreams. Why
cpilepfies occur in Jleep. Ecftacy of children. Cafe
of convuJJions in Jleep. Cramp, why painful*
Aflhma. Morning fw eats. Increafe of heat. In-
creafe of urine in jleep. Why more liable to take
cold in jleep. Catarrh from thin night -caps. Why
we feel chilly at the approach of Jleep, and at wak~
ing in the open air. 16. Why the gout commences in

Jleep. Secretions are more copious in Jleep , young
animals and plants grow more in Jleep. \ 7. Incon-

fiflency of dreams. Abfence of furprife in dreams.

i 8. Why we forget fome dreams and not others. \ 9.

Sleep-talkers . awake with furprife. 20. Remote

VOL. I. R

OF SLEEP. SECT. XVIII. i.

caufes of Jleep. dtmofphere with lefs oxygene.
Comprejfton of the brain in fpina bifida. By whir-
ling on an horizontal wheel. By cold. 21. Defini-
tion of jleep.

I. THERE are four fituations of our fyftem, which
in their moderate degrees are not ufually termed dif-
eafes, and yet abound with many very curious and
inftrudtive phenomena ; thefe are fleep, reverie,
vertigo, drunkennefs. Thefe we fhall previoufly
confider, before we ftep forwards to develop the
caufes and cures of difeafes with the modes of the
operation of medicines.

As all thofe trains and tribes of animal motion,
which are fubje&ed to volition, were the lafl that
were caufed, their connection is weaker than that
of the other claffes ; and there is a peculiar circum-
ftance attending this caufation, which is^ that it is
entirely fufpended during ileep ; whilft the other
claffes of motion, which are more immediately ne-
ceflary to life, as thofe caufed by internal fUmuli,
for inftance the pulfations of the heart and arteries,
or thofe catenated with pleafurable fenfation, as the
powers of digeftion, continue to ftrengthen their
habits without interruption. Thus though man in
his fkeping (late is a much lefs perfeft animal than
in his waking hours ; and though he confumes more
than one third of his life in this his irrational fitua-
tion ; yet is the wifdom of the Author of nature
manifeit. even in this feemin-g imperfection of his
work !

The truth of this affertion with refpecl; to the large
mufcles of the body, which are concerned in loco-
motion, is evident ; as no one in perfect fanity
walks about in his fleep, or performs any domeftic
offices ; and in refpeft to the mind, we n^ver ex-
ercife our reafon or recollection in dreams \ we may
fometimes feem diftrafted between contending paf*

SECT. XVIII. 2. OF SLEEP. 2F7

fions, but we never compare their obje£h, or deli-
berate about the acquifition of thofe objects, if our
ileep is perfect. And though many fynchronous
tribes or fucceflive trains of ideas may reprefent the
houfes or walks, which have real exigence, yet are
they here introduced by their connection with our
fenfations, and are in truth ideas of imagination,
not of recollection.

2. For our fenfations of pleafure and pain arc ex-
perienced with great vivacity in our dreams ; and
hence all that motley group of ideas, which are
caufed by them, called the ideas of imagination,
with their various alTociated trains, are in a very vi-
vid manner acted over in the fenforium ; and thefe
fometimes call into action the larger mufcles, which
have been much alTociated with them ; as appears
from the muttering featences, which fome people
utter in their dreams, and from the obfcure bark-
ing of fleeprng dogs, and the motions of their
feet and noftrils.

This perpetual flow of the trains of ideas, which
conftitute our dreams, and which are caufed by
.painful or pleafurable fenfation, might at firfl view
be conceived to be an ufelefs expenditure of fen-
forial power. But it has been mewn, that thofe
motions, which are perpetually excited, as thofe of
the arterial fyftem by the ftimulus of the blood, are
attended by a great accumulation of fenforial power,
after they have been for a time fufpended ; as the
hot-fit of fever is the confequence of the cold one*
Now as thefe trains of ideas caufed by fenfation are
perpetually excited during our waking hours, if
they were to be fufpended in ileep like the voluntary
motions, (which are exerted only by intervals du-
ring our waking hours,) an accumulation of fenfo-
rial power would follow ; and on our awaking- a
delirium would fupervene, fince thefe ideas caufed
by fenfation would be produced with fuch energy,

R 2 that

OF SLEEP. SECT. XVIII. 3.

that we fhould miftake the trains of imagination for
ideas excited by irritation ; as perpetually happens
to people debilitated by fevers on their firft awak-
ing ; for in thefe fevers with debility the general
quantity of irritation being diminiflied, that of fen-
fation is increafed. In like manner if the actions
of the (lomachj: inteftines, and various glands,
which are perhaps in part at lead caufed by or cate-
nated with agreeable fenfation, and which perpetu-
ally exift during, our waking hours, were like the
voluntary motions fufpended in our fleep ; the great
accumulation of fenforial power, which would ne-
ceflfarily follow^ would be liable to excite inflamma-
tion in them.-

3. When by our continued pofture in fleep,
Jo me urieafy fenfations are produced, we either gra-
dually awake by the exertion of volition, or the
xnufcles connected by habit with fuch fenfations
alter the pofition of the body ; but where the fleep
is uncommonly profound,- and thofe uneafy fenfa-
tions great, the difeafe called the incubus, or night-
mare, is produced. -Here the defire of moving the.
body is painfully exerted, by the power of moving
it, or volition, is incapable of action, till we
awake. Many lefs difagreeable druggies in our
dreams, as when we wifli in vain- to fly from terri-
fying objeds, conftitute a (lighter degree of this dif-
eafe. In av/akkig from the nightmare I have more
than once obferved, that there was no diforder in
Hiy pulfe ; nor do I believe the refpiration i* labo-
rious, as forne have affirmed. It occurs to people
\vhoie ileep: is too profound, and fome difagreeable
fenfation exifts, which at other times would have
awakened them, and have .thence prevented the
difeafe of nightmare j as after great fatigue or hun-
ger with too large a fupper and wine, which oeca-
fion our fleep- to be uncommonly profound* See
No. i4> of this Sedion*

4- &*

SECT. XVIII. 4. $. OF SLEEP.

4. As the larger mufcles of the body are much
more frequently excited by volition than by fenfa-
tion, they are but feldom brought into action in
our fleep : but the ideas of the mind are by habit
much more frequently connected with fenfation
than with volition ; and hence the ceafelefs flow of
our ideas in dr-eams. Every one's experience will
teach him this truth, for we all daily exert much
voluntary muicular motion: but few of mankind
can bear the fatigue of much voluntary thinking.

<j. A very curious circumftance attending thefe
our flceping imaginations is, that we feem to re-
ceive them by the fenfes. The mufcles, which are
fubfervient to the external organs of fenfe, are con-
nected with volition, and ceafe to aft in fleep;
hence the eyelids are clofed, and the tympanum of
the ear relaxed : and it is probable a fimilarity of
voluntary exertion may be neceflary for the percep-
tions of the other nerves of fenfe ; for it is obfeived
that the papillae of the tongue can be feen to be-
come ereded, when we attempt to tafte any thing
extremely grateful. Hewfon Exper. Enquir. V. 2.
186. Albini Annot. Acad. L. i. c. 15, Add to
this, that the immediate organs of fenfe have no
objects to excite them in the darknefs and filence
ot the night ; but their nerves of fenfe neverthelefs
continue to poflefs their perfecl activity fubferyient
to all their numerous fenfitive connections. This
vivacity of our nerves of fenfe during the time of
fleep is evinced by a circumftance, which almoft
every one mud at foine time or other have experi-
enced ; that is, if we fleep in the day-light, and
endeavour to fee fome object in our dream, the
light is exceedingly painful to our eyes ; and after
repeated druggies we lament in our fleep, that we
cannot fee it. In this cafe I apprehend the eye lid
jis in fome degree opened by the vehemence of our
(enfationsj and, the iris being dilated, the optic

nerve

•

220 O F S L E E P. SECT. XVIII. $.

nerve (hews as great or greater fenfibility than in
our waking hours. See No. 15. of this Sedion.

When we are forcibly waked at inidmght from;
profound fleep, our eyes are much dazzled with
the light of the candle for a minute or two, after
there has been fufficient time allowed for the con-
tra&ion pf the iris ; which is owkig to the accu-
mulation of fenforial power in the organ of vifion
during its ftate of lefs adivity. But when we have
dreamt much of vifible objeds, this accumulation
of fenforial power in the organ of vifion is leflened
or prevented, and we awake in the morning with-
out being dazzled with the light, after the iris
has had time to contract jtfelf. This i§ a matter of
great curiofity, and may be thus tried by any one
in the day-light. Clofe your eyes, and cover them
•with your hat ; think for a minute on a tune, which
you are accuftomed to, and endeavour to fing it
with as little activity of mind as poflible. Sudden-
ly uncover and open your eyes, and in one fecond
of time the iris will contract itfelf, but you will
perceive the day more luminous for feveral feconds,
owing to the accumulation of fenforial power in the
Optic nerve.

Then again clofe and cover your eyes, and think
intenfely on a cube of ivory two inches diameter,
attending firft to the north and fouth fides of it, ancl
then to the other four fides of it ; then get a clear
image in your mind's eye of all the fides of the
iaine cube coloured red ; and then of it coloured
green; and then of it coloured blue; laftly, open
your eyes as in the former experiment, and after
the firft fecond of time allowed for the contraction
of the iris, you will not perceive any increafe of the
light of the day, or dazzling; becaufe now there is
no accumulation of fenforial power in the optic
nerve; that having been expended by its adion in
thinking over vifiblc obje&s.^

SECT. XVIII. 6. 7. O F S L E E P.

This experiment is not eafy to be made at firft,
but by a few patient trials the fact appears very
certain ; and fhews clearly, that our ideas of ima-
gination are repetitions of the motions of the nerve,
which were originally occafioned by the ftimulus
of external bodies ; becaufe they equally expend
the icniorial power in the organ of fenfe. See Seel:.
HL 4. which is analogous to our being as much
fatigued by thinking as by labour.

6. Nor is it in our dreams alone, but even in our
waking reveries, and in great efforts of invention,
fo great is the vivacity of our ideas, that we do not
for a time diftinguifh them from the real prefence
of fubftantial objects ; though the external organs
of fenfe are open, and furrounded with their ufual
ftimuli. Thus whilft I am thinking over the beau-
tiful valley, through which I yefterday travelled, I
do not perceive the furniture of my room : and
there are fome, whofe waking imaginations are fo
apt to run into perfect reverie, that in their com-
mon attention to a favourite idea they do not hear
the voice of the companion, who accofts them, un-
lefs it is repeated with unufual energy.

This perpetual miftake in dreams and reveries,
where our ideas of imagination are attended with a
belief of the prefence of external objeds, evinces
beyond a doubt, that all our ideas are repetitions of
the motions of the nerves of fenfe, by which they
were acquired ; and that this belief is not, as fome
late philofophers contend, an inttincl neceflarily
connected only with our perceptions.

7. A curious queftion demands our attention in
this place ; as we do not diftinguifli in our dreams
and reveries between our perceptions of external
obje&s, and our ideas of them in their abfence,
how do we diftinguifli them at any time ? In a
dream, if the fweetnefs of fugar occurs to my ima-
gination, the whitenefs and hardnefs of it, which

O F S L E E P. SEPT. XVIII. $.

were ideas ufually connected with the fweetnefs,
immediately follow in the train ; and I believe a\
material lump of fugar prefent before my fenfes ;
but in my \vaking hours, if the fweetnefs occurs to
my imagination, the ftimulus of the table to my
hand, or of the window to my eye, prevents the
other ideas of the hardnefs and whitenefs of the
fugar from fucceeding ; and hence I perceive the
fallacy, and difbelieve the exigence of objects cor-
refpondent to thofe ideas, whofe tribes or trains are
broken by the ftimulus of other objects. And
further in our waking hours, we frequently exert
our volition in comparing prefent appearances with
fuch, as we have ufually obferved ; and thus cor-
rect the errors of one fenfe by our general know-
ledge of nature by intuitive analogy. See Sed.
XVII. 3. 7. Whereas in dreams the power of voli-
tion is fufpended, we can recollect and compare
our prefent ideas with none of our acquired know-
ledge, and are hence incapable of obferving any
absurdities in them.

By this criterion we diftinguifh our waking from
our fleeping hours, we can voluntarily recollect our
fleeping '. ideas^when we are awake, and compare
them with our waking ones ; but we cannot in our
fleep voluntarily recollect our waking ideas at all.

8. The vaft variety of fcenery, novelty of combi-
nation, and (iiftinctnefs of imagery, are other cu-
rious circumftances of our fleeping imaginations.
The variety of fcenery feems to arife from the fupe-
rior activity and excellence of pur fenfe of vifion;
which in an inftant '^infolds to t]ie mind extenfive
fields of pleafurable ideas | while the other fenfes
collect their objects flowly, and 'with little combina-
tion ; add to this, that the ideas, which this organ
prefents us with, are more frequently connected
with our fenfation than thofe of any other.

9. The

*' */ ^- V. , ?', -v &% ,

SECT. XVIII. 9. 10. ii. OF SLEEP.

9. The great novelty of combination is owing to
another circumftance ; the trains of ideas, \vhich
are carried on in our waking thoughts, are in our
jdreams diffevered in a thoufand places by the fufpen-
fion of volition, and the abfence of irritative ideas,
and are hence perpetually falling into new catena-
tions. As explained in Sect. XVI. i. 9. For the
power of volition is perpetually exerted dining our
.waking hours in comparing our pafling trains of
ideas with our acquired knowledge of nature, and
thus forms many intermediate links in their catena-
tion. And the irritative ideas excited by the ftimulus
of the objects, with which we are furrounded, are
every moment intruded upon us, and form other
links of our unoeafing catenations of ideas

ip. The abfencc of the ftimuli of external bodies,
and of volition, in our dreams renders the organs
of fenfe liable to be more ftrongly affected by the
powers of fenfation, and of ailociation. For onf
defires or averfions, or the obtrufions of furround-
ing bodies, diifever the fenfitive and aflbciate tribes
of ideas in our waking hours by introducing thofe
of irritation and volition amongft them. Hence
proceeds <the fuperior diftinctnefs of pleafurable or
painful imagery in our fleep ; for we recai the figure
and the features of a long loft friend, whom we
loved, in our dreams with much more accuracy and
vivacity than in our waking thoughts. This circum-
flance contributes £o prove, that our ideas of ima-
gination are reiterations of thofe motions of our
organs of fenfe, which were excited by external
objects ; becaufe while we are expofed to the ftimuli
of prefent objects, our ideas of abfent objects can-
not be fo diftinctly formed.

1 1. The rapidity of the fucceilion of tranfactions
in our dreams is almoft inconceivable ; infomuch
that, when we are accidentally awakened by the

jarring

O F S L E E F. SECT. XVIII, i *.

jarring of a door, which is opened into our bed-
chamber, we fometimes dream a whole hiftory of
thieves or fire in the very inftant of awaking.

Daring thefufpenfion of volition we cannot com*
pare our other ideas with thofe of the parts of time
in which they exift ; that is, we cannot compare the
imaginary fcene, which is before us, with thofe
changes of it, which precede or follow it : becaufe
this ad of comparing requires recollection or volun-
tary exertion. Whereas in our waking hours, we
are perpetually making this companion, and by
that means our waking ideas are kept confident with
each other by intuitive analogy ; but this comparifont
retards the fucceffion of them, by occafioning their
repetition. Add to this, that the tranfa&ions of
our dreams confift chiefly of vifible ideas, and that
a whole hiftory ©f thieves and fire may be beheld in
an inftant of time like the figures in a pifture.

1 2. From this incapacity of attending to the parts
of time in our dreams, arifes our ignorance of the
length of fche night; which, but from our conftant
experience to the contrary, we fhould conclude was
but a few minutes, when our ileep is perfect. The
fame happens in our reveries ; thus when we are
pofTeffed with vehement joy, grief, or anger, time
appears fhort, for we exert no volition to compare
the prefent fcenery with the paft or future ; but when
we are compelled to perform thofe exercifes of mind
or body, which are unmixed with paflion, as in
travelling over a dreary country, time appears long ;
for our defire to fini(h our journey occafions us more
frequently to compare our prefent fituation with the
parts of time or place, which are before and behind
us.

So when we are enveloped in deep contemplation
of any kind, or in reverie, as in reading a very in*
terefting play or romance, we meafure time very
inaccurately j and hence, if a play greatly affects

our

SECT. XVIII. 12. OF SLEEP. 22?

our paflions, the abfurdities of palling over many
days or years, and of perpetual changes of place,
are not perceived by the audience ; as is experienced
by every one, who reads or lees foine plays of the
immortal Shakefptar ; but it is necefiary for inferior
authors to obferve thofe rules of the *d*'** and
*&™ inculcated by Ariftotle, becaufe their works
do not intereft: the paflions fufficiently to produce
complete reverie. ^

Thofe works, however, whether a romance or a
fermon, which do not intereft us fo much as to in-
duce reverie, may neverthelefs incline us to fleep,
For thofe pleafurable ideas, which are prefented to
us, and are too gentle to excite laughter, (which is
attended with interrupted voluntary exertions, as
explained Seel:. XXXIV. i. 4.) and which are not
accompanied with any other emotion, which ufually
excrtes fome voluntary exertion, as anger, or fear,
are liable to produce fleep ; which confifts in a fuf-
penfion of all voluntary power. But if the ideas
thus prefented to us, and intereft our attention, are
accompanied with fo much pleafurable or painful
fenfation as to excite our voluntary exertion at the
fame time, reverie is the confequence. Hence an
inter-efting play produces reverie, a tedious one pro-
duces fleep : in the latter we become exhaufted by
attention, and are not excited to any voluntary ex-
ertion, and therefore fleep j in the former we are
excited by fome emotion, which prevents by its pain
the fufpenfion of volition, and in as much as it in?
terefts us, induces reverie, as explained in the next
Settion.

But when our fleep is imperfect, as when we have
determined to rife in half an hour, time appears
longer to us than in moft other fituations. Here
our folicitude not to overfleep the determined time
induces us in this imperfect fleep to compare the
quick changes of imagined fcenery with the parts

of

OF SLEEP. SECT, XVIII. 13. 14,

jof time or place, they would have taken up, had
they real exiftence ; and that more frequently than
in our waking hours ; and hence the time appears
longer to us : and I make no doubt, but the per-
mitted time appears long to a man .going to the gal-
lows, as the fear of its quick lapfe will make him
think frequently about tit,

13. As we gain our knowledge of time by com-
paring the prefent fcenery with the pad and future,
and of place by comparing the fituations of objects
with each other ; fo we gain our idea of confciouf-
nefs by comparing ourfelves with the fcenery around
us ; and of identity by comparing our prefent con-
fcioufnefs with our pad confcioufnefs : as we never
think of time or place, but when we make the com-
parifpus above mentioned, fo we never think of con-
icioufnefs, but when we compare our own exiftence
with that of other objects ; nor of identity, but
when we compare our prefent and our paft confei-
oufnefs. Hence the confcioufnefs of our own ex-
iftence, and of pur identity, is owing to a voluntary-
exertion of our minds : and OQ that account in our
complete dreams we neither meafure time, are fur-
prifed at the fudden changes of place, 'nor attend to
our own exiftence, or identity; becaufe our power
of volition is fufpended. B,ut all thefe circumftances
are more or lefs obfervable in our incomplete ones ;
for then we attend a little to the lapfe of time, and
the changes of place, and to our pwrj exiftence ; and
even to our identity of perfon ; for a lady feldom,
dreams, that (he is a foidier ; nor a man, that he i§
brought to bed.

14. As long as our fenfations only excite theii;
fenfual motions, or ideas, our ileep continues found ;
but as foon as they excite defires or averfions, our
fleep becomes imperfect ; and when that defire or
averfion is fo ftrong, as to produce voluntary mo-
tions.

SECT. XVIIL 14. O F S L E E P.

tions, we begin to awake ; the larger mufcles of the
body are brought into action to remove that irrita-
tion or fenfation, which a continued pofture has
cauied ; we itretch our limbs, and yawn, and our
fleep is thus broken by the accumulation of volun-
tary power.

Sometimes it happens, that the act of waking is
fuddenly produced, and this foon after the com-
mencement of fleep ; which is occafioned by fome
fenfation fo difagreeable, as inltantaneoufly to excite
the power of volition ; and a temporary action of
all the voluntary motions fuddenly fucceeds, and we
ftart awake. This is fometimes accompanied with
loud noife in the ears, and with fome degree of fear ;
and when it is in great excefs, fo as to produce con-
tinued convulfive motions of thofe mufcles, which
are generally fubfervient to volition, it becomes
epilepfy : the fifs of which in fome patients gene-
rally commence during fleep. This differs from the
night-mare defcribed in No. 3. of this Section, be-
caufe in that the difagreeable fenfation is not fo
great as to excite the power of volition into action ;
for as foon as that happens, the difcafe ceafes.

Another circumitance, which fometimes awakes
people foon after the commencement of their fleep,
is where the voluntary power is already fo great in
quantity as almoit to prevent them from falling
afleep, and then a little accumulation of it foon again
awakens them ; this happens in cafes of infanity, or
where the mind has been lately much agitated by
fear or anger. There is another circumftance in
which fleep is likewife of (hort duration, which arifes
from great debility, as after great over-fatigue, and
in fome fevers, where the itrength of the patient
is greatly diminifhed, as in thefe cafes the pulfe
intermits or flutters, and the refpiration is pre-
vioufly affected, it feems to originate from the want

of

OF SLEEP. SECT. XVIII. i$.

of fome voluntary efforts to facilitate refpiration, as
uvhen we are awake\ And is further treated of in
Vol. II. .Ciafs I. 2. i. 2. on the Difeafes of the Vo*
luntary Power. Art. Somnus interruptus.

15. We come now to thofe motions which' de-
pend on irritation. The motions of the arterial and
glandular fyftems continue in our fleep, proceeding
flower indeed, but ftronger and more uniformly,
than in our waking hours, when they are incommo-
ded by external ftimuli, or by the movements of vo-
lition ; the motions of the mufcles fubfervient to
refpiration continue to be flimulated into action, and
the other, internal fenfes of hunger, third, and luft,
are not only occafionally excited in our Hfleep, but
their irritative motions are fucceeded by their ufual
fenfations, and make a part of the farrago of our
dreams. Thefe fenfations of the want of air, of
hunger, third, and luft, in our dreams, contribute
to prove, that thefe nerves of the external fenfes arc
alfo alive and excitable in our fleep ; but as the fti-
inuli of external objects are either excluded from
them by the darknefs and filence of the night, or
their accefs to them is prevented by the fufpeniion of
volition, thefe nerves of fenfe fa.ll more readily
into their connexions with fenfation and with afib-
ciation ; becaufe much fenforial power, which dur-
ing the day was expended in moving the external
organs of fenfe in conlequence of irritation from
external ftimuli, or in confequence of volition, be-
comes now in fo'me degree accumulated, and renders
the internal or immediate organs of fenfe more ea-
jfily excitable by the other fenforial powers. Thus
in reipect to the eye, the irritation from external
ftimuli, and the power of volition during our wak-
ing hours, elevate the eye-lids, adapt the aperture
of the ins to the quantity of light, the focus of the
•cry ftal line humour, and the angle of the optic axifes
to the diitaace of the object, ail which perpetual ac-
tivity

-

SECT. XVIII. 15. O F S L E E P. 229

tivity during the day expends much fcnforial power,
which is faved during our ileep.

Hence it appears, that not only thofe parts of the
fyftem, which are always excited by internal ftimuli,
as the ftomach, inteftinal canal, bile-duds, and the
various glands, but the organs of fenfe alfo, may
be more violently excited into action by the irrita-
tion from internal ftimuli, or by fenfation, during
our fleep than in our waking hours j becaufe during
the fufpenfion of volition, there is a greater quan-
tity of the fpirit of animation to be expended by the
other fenforial powers. On this account our irrita-
bility to internal ftimuli, and our fenfibility to pain
or pleafure, is not only greater in fleep, but increa-
fes as our fleep is prolonged. Whence digeflion and
fecretion are performed better in fleep, than in our
waking hours, and our dreams in the morning have
greater variety and vivacity, as our fenfibility in-
creafes, than at night when we firft lie down. And
hence epileptic fits, which are always occafioned by
fomediiagreeable fenfation, fo frequently attack thofe
\vho are fubjeft to them, in their fleep ; becaufe at
this time the fyftem is more excitable by painful fen-
fation in confequence of internal ftimuli j and the
power of volition is then fuddenly exerted to relieve
this pain, as explained Seel XXXIV. i. 4.

There is a difeafe, which frequently affects children
in the cradle, which is termed ecftafy, and feems to
confift in certain exertions to relieve painful fenfa-
tion, in which the voluntary power is not fo far ex-
cited as totally to awaken them, and yet is fufficient
to remove the difagreeable fenfation, which excites itj
in this cafe changing the pofture of the child fre-
quently relieves it.

1 have at this time under my care an elegant
young man about twenty-two years of age, who fel-
dom fleeps more than an hour without experiencing
a convuliion fit $' which ceafes in about half a mi-
nute

OF SLEEP.

imte without any fubfequent ftupor. Large dofes
of opium only prevented the paroxyfms, fo l°no as
they prevented him from fleeping by the intoxication,
which they induced. Other medicines had no effect
on him. He was gently awakened every half hour
for one night, but without good effecl, as he foon
flept again, and the fit returned at about the fame
periods of time, for the accumulated fenforial power,
which occafioned the increafed fcnfibility to pain,
was not thus exhaufled. This cafe evinces, that the
fenfibiiity of the fyflem to internal excitation increa-
fcs, as our lleep is prolonged ; till the pain thus oc-
cafioned produces voluntary exertion ; which, wheni
it is in its ufual degree, only awakens us ; but when
It is more violent, it occafions cortvulftons.

The cramp in the calf of the leg is another kind
of convulfior;, which generally commences in ileep,
occafioned by the continual increafe of irritability
from internal ftimuli, or of fenfibiiity, during that
ftate of our exiftence. The cramp is a violent ex
ertion to relieve pain, generally either of the ikin
from cold, or of the bowels, as in fome diarrhoeas,
or from the mufcles having been previoufly over-
tlretched, as in walking up or down deep hills. But
in thefe convulfions of the rnufcles, which form the
calf of the leg, the contraction is fo violent as to oc-
cafion another pain in conlequence of their own toa
violent contraction, as foon a« the original pain, which
caufed the contradion, is removed. And hence the
cramp, or fpafm, of thefe mufcles is continued without
intermiflion by this new pain, unlike thealternate con-
vulfions and remiflions in epileptic fits. The reafony
that the contraction of thefe mufcles of the calf of
the leg is more violent during their convulfion than
that of others, depends on the weaknefs of their
antagonift mufcles ; for after thefe have been con-
traded in their ufual adion, as at every flep in
walking, they are again extended, not, as mod

other

Skcr. XVill. 15. OF SLEEP. 251

other mufcles are, by their antagonids, but by the
weight of' the whole body on the balls of the toes ;
and that weight applied to great mechanical advan-
tage on the heel, that is, on the other end of the
bone of the foot, which thus acts as a lever.

Another difeafe, the periods of which generally
commence during our fleep, is the a'thma. What-
ever may be the remote caufe of paroxyfms of afth-
ma, the immediate caufe of the convulfive refpira-
tion, whether in the common ai^hina, or in what is
termed the convulfive afthma, which are perhaps
only different degrees of ihe fame difeafe, mud be
owing to violent voluntary exertions to relieve pain,
as in other corivulfions ; and the increafe of irrita-
bility to internal flimuii, or of fenfibility, during
Deep mud occafion them to commence at this time.

Debilitated people, who have been unfortunately
accuftomed to great ingurgitation of fpirituous po-
tation, frequently part with a great quantity of
water during the night, but with not more than ufual
in the day-time. This is owing to a beginning tor-
por of the abforbent fyftem, and precedes anafarca,
which commences in the day, but is cured in the
night by the increafe of the irritability of the abfor-
bent fyliem during ileep, which thus imbibes from
the cellular membrane the fluids, which had been
accumulated there during the day ; though it is pof-
fible the horizontal pofition of the body may con-
tribute fomething to this purpofe, and alfo the
greater irritability of fome branches of the abforbent
veflels, which open their mouths in the cells of the
cellular membrane, than that of other branches.

As foon as a perfon begins to ileep, the irritability
and fenfibility of the fyltern begins to increafe,
owing to the fufpenfionof volition and the exclufion
of external ftimuli. Hence the actions of the veflels
in obedience to internal Simulation become ftronger
and more energetic, though lefs frequent in refpecl:
to number. And as many of the fecretion$ are in.
VOL. I, .S creafed

2$* O F S L E E P. SECT. XVIII. 16*

creafed, fo the heat of the fyfiem is gradually in-
creafed, and the extremities of feeble people, which
had been cold during the day, become warm. Tilt
towards morning many people become fo warm, as
to find it neceflary to throw oft forae of their bed-
clothes, as foon as they awake ; and in others
fweats are fo liable to occur towards morning during
vheir fleep.

Thus thofe, who are not accuftomed to fleep in*
the open air, are very liable to take cold, if they
happen to fall afleep on a garden bench, or in a
carriage with the window open. For as the fyftem
is warmer during fleep, as above explained, if a cur-
rent of cold air affects any part of the body, a torpor
of that part is more effectually produced, as when a
cold blaft of air through a key-hole or cafement falls
upon a perfon in a warm room. In thofe cafes the
affected part pofieffes lefs irritability in refpect to heat,
from its having previoufly been expofed to a greater
flimulus of heat, as in the warm room, or during
fleep ; and hence, when the ftimuhis of heat is di-,
minifhed, a torpor is liable to enfue ; that is, we
take cold. Hence people who fleep in the open air,
generally feel chilly both at the approach of fleep,
and on their awaking ; and hence many people are
perpetually fubject to catarrhs if they freep in a
lefs warn* head-drefs, than that which they wear in
the day. .

1 6. Not only the fenforial powers of irritation and
of fenfation, but that of affbciation alfo appear to acl:
with greater vigour during thefufpenfion of volition:
in fleep. It will be fhewn in another place, that the
gout generally^ attacks the liver, and that afterwards
an inflammation of the ball of the great toe com-
menccs by affociation, and that of the liver ceafes.
Now as this change or metaftafis of the activity
of the fyftem generally commences in fleep, it fol-
lows, that the.fe aflbeiations of motion exift with

greater

Skct. XVIIJ. 16. O F S L E £ P. 253

greater energy at that time; that is, that the fenforial
faculty of aftoc'ation, like thofe of irritation and of
fenfation, becomes in fome meafure accumulated
during the fufpenfion of volition.

Other aflbciate tribes and trains of motions, as
well as the irritative and fenfitive ones, appear to
be increafed in their activity during the fufpenfion
of volition in fleep. As thofe which contribute to
circulate the blood, and to perform the various fe-
cretions ; as well as the aflbciate tribes and trains of
ideas, which contribute to furnifli the perpetual
ilreams of our dreaming imaginations.

In fleep the fecretions have generally been fup-
pofed to be diminifhed, as the expectorated mucus in
coughs, the fluids difcharged in diarrhceas, and in
falivaticn, except indeed the fecretion of fweat,
which is often vifibly increafed. This error feems to
have arifen from attention to the excretions rather
than to the fecretions. For the fecretions, except
that of fweat, are generally received into refervoirs,
as the urine into the bladder, and the mucus of the
interlines and lungs into their refpeclive cavities ;
but thefe refervoirs do not exclude thefe fluids im-
mediately by their ftimulus, but require at the fame
time fome voluntary efforts, and therefore permit
them to remain during fleep. And as they thus
continue longer in thofe receptacles in our fleeping
hours, a greater part is abforbed from them, and the
remainder becomes thicker, and fometimes in lefs
quantity, though at the time it was fecreted the fluid
was in greater quantity than in our waking hours.
-Thus the urine is higher coloured after long fleep ;
which fhews, that a greater quantity has been fe-
creted, and that more of the aqueous and faline part
has been reabfcrbed, and the earthy part left in the
bladder ; hence thick urine" in fevers ihews only a
greater action of the veflels which fecrete it in the
kidneys, and of thofe which abforb it from the blad-
der.

$2, The

254 OF SLEEP. SECT. XVItt. 17

The fame happens to the mucus expe&orated in
coughs, xvhich is thus thickened by abforption of its
aqueous and faline pam ; and the fame of the feces
of the inteftines. From hence it appears, and front
\vhathas been faid ia No. i ^, of this Section con-
cerning the increafe of irritability and of fenfibility^
during ileep, that the fecretions are in general rather
increaied than diminifhed during thefe hours of our
cxiftence ; and it is probable that nutrition is almoffc
entirely performed in Ileep ; and that young animals
grow more at this time than in th-eir waking hoursy
as young plants have long fines been obfcrved to
grow more in the night, which is their time of
fleep.

17. Two other remarkable circumilances of our
dreaming ideas are their inconfiftency, and the total
abfence of furprife. Thus we feem to be prefent at
more extraordinary metamorphofes of animals or trees,
than are to be met with in the fables of antiquity ;
and appear to be tranfported from place, which ft a •!
divide, as quickly as the changes of fcenery are per-
formed in a play-houfe j. and yet are not fenfible of
their inconnitency, nor in the leafi degree affected
with furprife.

We mud confkier this circumftance more minute-
ly. In our waking trains of ideas, thole that are
inconfi!r.ent with the ufual order of nature, fo rarely
have occurred to us, that their connexion is the
fllghtbft of all others : hence, when a confident train
of ideas is exhaufted, we attend to the external ili-
muii, that u-fualjy furround us, rather than to any
inconfrilent idea which might otherwife prefent itfelf ;.
and if an inconfiftent idea (liould intrude itfelf, we
inimevliately compare it with the preceding one, and
voluntarily reject the train it would introduce ; this
appears further in the Sedion on Reverie, in which
Itate of the mind external ftimuli are not attended to,
and yet the Itreams of ideas are kept confident by the
of volition. But as our faculty of volition

Si CT. XVIII. 18. 19. O F S L E E P. 255

is fufpended, and all external famuli are excluded
in fleep, this flight er connexion of ideas take place ;
and the train is laid to be inconfiflent ; that is, difli-
inilar to the ufual order of nature.

But, when any con lift en t train of fenfitive or vo-
luntary ideas is flowing along, if any external ftimu-
lus affects us Ib violently, as to intrude irritative
ideas forcibly into th-e mind, it difunites the former
train of ideas/, and we are affected with furprife*
Thefe ftimuli of unufual energy or novelty not only
difunite our common trains of ideas, but the trains of
tnufcular motions alfo, which have not been long
eflablifhed by habit, and diftarb thofe that have.
Some people become motionlefs by great furprife,
the fits of hiccup and of ague have been often re-
moved by it, and it even affects the movements of
the heart and arteries ; but in our flcep, all external
ftimuli are excluded, and in confequence no furprife
can exift. See Section XVII. 3. 7.

1 8. We frequently awake with pleafure from a
dream, which has delighted us, without being able
to recollect the tranfaclions of it: unlefs perhaps at
a diftance of time, fome analogous idea may intro-
duce afrefh this forgotten train : and in our waking
reveries we fometimes in a moment loie the train of
thought, but continue to feel the glow of pleafure,
or the depreflion of fpirits, it occaiioned : whilft at
other time we can retrace with eafe thefe hiftories of
our reveries and dreams.

The above explanation of furprife throw* light
upon this fubject. When we are fuddenly awaked
by any violent ftimulus, the furprife totally difunites
the trains of our fleeping ideas from thefe of our
waking ones ; but if we gradually awake, this does
not happen ; and we readily unravel the preceding
trains of imagination.

19. There are various degrees of furprife; the
pi ore intent we are upon the train of ideas, which

we

25$ OF SLEEP. SECT. XVIII. 23,

we are employed about, the more violent muft be
the ftimulus that interrupts them, and the greater is
the degree of furprife. I have obferved dogs, who
have flept by the fire, and by their obfcure barking and
ftruggling have appeared very intent on their prey,
that (hewed great furprife for a few feconds after
their awaking by looking eagerly about them ; which
they did not do at other rimes of waking. And an
intelligent friend of mine has remarked, that his
lady, who frequently fpeaks much arid articulately
in her fleep, could never recollect her dreams in the
morning, when* this happened to her: but that
when me did not fpeak in her fleep, fhs could always
recoiled them,

Hence, when our fenfations aft fo ftrongly in fleep
as to influence the larger mufcles, as in thofe, who
talk or ftruggle in their dreams ; or in thofe, who
are affected with complete reverie (as defcribed in
the next Section), great furprife is produced, when
they awake ; and 'thefe, as well as thofe who are
completely drunk or delirious, totally forget after-
wards their imaginations at thofe times.

20. As the immediate caufe of fleep confifls in
the fufpenfion of volition, it follows, that whatever
diminilhes the general quantity of fenforial power, or
derives it from the faculty of volition, will con-
Ititute a remote caufe of fleep ; fuch as fatigue from
mufcular or mental exertion, which diminifhes the
general quantity of fenforial power ; or an increafe
of the fenfitive motions, as by attending to foft mufic,
which diverts the fenforial power from the faculty of
volition ; or laftly, by increafe of the irritative mo-
tions, as by wine,, or food, or warmth ; which not
only by their expenditure of fenforiai power dimi-
riifri the quantity of volition ; but alfo by their pro-
ducing pleafurable fenfations (which occafion other
inufcuiar or fenfual motions in confequence), doubly
decreafe the voluntary power, and thus more forcibly
produce fleep. See Seel. XXXIV. 1.4.

Another

SECT. XVIII. 20. OF SLEEP. 257

Another method of "inducing fleep is delivered in
a very ingenious work lately publifhed by Dr. Bed-
does. Who, after lamenting thai opium frequently
occafions reftleflhefs, thinks, " that in moft cafes it
would be better to induce fleep by the abftraftion of
flimn'i, than by exhaufling the excitability;" and
adds, " upon this principle we could not have a
better foporific than an atmofphere with a diminifh-
ed proportion of oxygene air, and that common air
might be admitted after the patient was afleep."
(Obferv. on Calculus, &c. by Dr. Beddoes. Murray.)
If it (hould be found to be true, that the excitability
of the fyftem depends on the quantity of oxygene
abforbed by the lungs in refpiration according to the
the theory of Dr. Beddoes, and of Mr. Girtanner,
this idea of fleeping in an atmofphere with lefs oxy-
gene in its compofition might be of great fervice in
epileptic cafes, and in cramp, and even in fits of the
afthma, where their periods commence from the in*,
creafe of irritability during fleep.

Sleep is likewife faid to be induced by mechanic
preffure on the brain in the cafes of fpina bifida.
Where there has been a defect of one of the verte-
brae of the back, a tumor is protruded in confequence;
and, whenever this tumor has been comprefled by
the hand, fleep is faid to be induced, becaufe the
whole of the brain both within the head and fpine
becomes comprefled bv the retroceffion of the fluid
within the tumor. But by what means a compref-
fion of the brain induces fleep has not been explain-
ed, but probably by diminifliing the fecretion of fen-
forial power, and then the voluntary motions be-
come fufpended previoufly to the irritative ones> as
occurs in moft dying perfons.

Another way of procuring fleep mechanically was
related to me by Mr. Brindley, the famous canal en-
gineer, who was brought up to the bufinefs of a mill-
wright j he told me, that he had more than once

feer*

2$S O F SLEEP, SECT. XVIII, 21,

ieen the experiment of a rn'an extending himfelf
acrofs the large (lone of a corn-mill, and that by
gradually letting the (lone whirl, the man fell afleep
before the (lone had gained its full velocity, and he
fuppofed would have died without pain by the con-
tinuance or increafe of the motion. In this cafe the
centrifugal motion of the head and feet muft accu-
mulate the blood in both thofe extremities of the
body, and thus comprefs the brain.

JLafHy, we (hould mention the application of cold ;
•which, when in a lefs degree, produces watchfulnefs
by the pain it occafious, and the tremulous convul-
fions of the fubcutaneous rnufcles ; but when it is
applied in great degree, is faid to produce fleep. To
explain this effect it has been faid, that as the veffels
of the ikin and extremities become firft torpid by
the want of the flimulus of heat, and as thence lefs
blood is circulated through them, as appears from
their palenefs, a greater quantity of biood poured
upon the brain produces fleep by its com-preilion of
that organ. But I (houl J rather imagine, that the
fenforial power becomes exhaufted by the convulfive
actions in confequence of the pain of cold, and of
the voluntary exercife previoufly ufed to prevent it,
and that the fleep is only the beginning to die, as the
fufpenfion of voluntary power in lingering deaths
precedes for many hours the extinction of the irrita-
tive motions.

21. The following are the characteristic circum-
ilances attending perfect fleep.

j. The power of volition is totally fufpended.

2. The trains of ideas caufed by fenfation proceed
with greater facility and vivacity; but become in-
confi (lent with the ufual order of nature. The muf-
cular motions caufed by fenfation continue ; as thofe
concerned in our evacuations during infancy, and
afterwards in digeftion, and in priapifmus.

3. The

SECT. XVIII. 2i. OF SLEEP. 259

3. The irritative mufcular motions continue, as
thofe concerned in the circulation, in fecretion, in
refpiration. But the irritative fenfual motions, or
ideas, are not excited ; as the immediate organs of
fenfe are not (limulated into aclion by external ob-
jects, which are excluded by the external organs
of fenfe ^ which are not in fleep adapted to their
reception by the power of volition, as in our waking
hours.

4. The aflbciate motions continue; but their
firfl: link is not excited into aclion by volition, or
by external ftimuli. In all refpecb, except thofe
above mentioned, the three lad fenforial powers are
fomewhat increafed in energy during the fufpenfion
of volition, owing to the confequeiit accumulation of
the fpirit of animation.

SECT,

*6o OP REVERIE. SECT. XiX. i.

SECT. XIX.

OF REVERIE.

i. Various degrees of reverie. 2. Sleep-walkers.
Cafe of a young lady. Great furprife at awaking.
And total forgetfulnefs of what faffed in reverie.
3. No fufpenfion of 'volition in reverie. 4. Senji-
live motions continue ', and are confident. 5. Irri-
iative motions continue, but are not fucceeded by
fenfation. 6« Volition mceffary for the perception
of feeble impreffions. -7. AJfrciated motions continue.
8. Nerves offenfe are irritable in fleep> but not in
reverie. 9. Somnambuli are not afleep. Contagion
received but once. \ o. Definition of reverie.

i, WHEN we are employed with great fenfation
of pleafure, or with great efforts of volition, in the
purfuit of fome interefting train of ideas, we ceafe
to be confcious of our exiilence, are inattentive to
time and place, and do not diftinguifh this train of
fenfitive and voluntary ideas from the irritative ones
excited by the prefence of external objecls, though
our organs of ienfe are furrounded with their ac-
cuilorned ftimuli, till at length this interefting train
of ideas becomes exhaufted, or the appulfes of ex-
ternal objects are applied with unufual violence,
and we return with furprife, or with regret, into
the common track of life. This is termed reverie
or ftudium.

In fome conftitutions thefe reveries continue a
confiderable time, and are not to be removed
without greater difficulty, but are experienced in
a lefs degree by us all ; when we attend earneftly
to the ideas excited by volition or fenfation, with
their ailbciated connexions, but are at the fame

time

SECT. XIX. 2. O F R E V E R I E. *6f

time confcious at intervals of the ftiinuli of fur-
founding bodies. Thus in being prefent at a play,
or in reading a romance, fome perfons are fo totally
abforbed as to forget their ufual time of fleep, and
to neglect their meals ; while others are (aid to
have been fo involved in voluntary ftudy as not to
have heard the discharge of artillery ; and there is
a ftory of an Italian politician, who could think fo
intenfely on other fubjecls, as 'to be infenfible to
the torture of the rack.

From hence it appears, that thefe catenations of
ideas and mufcular motions, which form the trains
of reverie, are compofed both of voluntary and
fenfitive aflbciations of them ; and that thefe ideas
differ from thofe of delirium or of fleep, as they
are kept confident by the power of volition ; ancl
they differ alfo from the trains of ideas belonging
to infanity, as they are as frequently excited by
fenfation as by volition. But laitly, that the whole
fenforial power is fo employed on thefe trains of
complete reverie, that like the violent efforts of
volition, as in convulfions or infanity ; or like the
great activity of the irritative motions in drunken-
nefs ; or of the fenfitive motions in delirium ;
they preclude all fenfation confequent to external
ftimulus.

2. Thofe perfons, who are faid to walk in their
fleep, are affected with reverie to fo great a degree,
that it becomes a formidable difeafe ; the eflence of
which confifts in the inaptitude of the mind to at*
tend to external ftimuli. Many hiflories of this
difeafe have been publifhed by medical writers $ of
which there is a very curious one in the Laufanne
Tranfaftions. I fhall here fubjoin an account of
fuch a cafe, with its cure, for the better illuf-
tration of this fubject.

A. very ingenious and elegant young lady, with
light eyes and hair, about the age of feventeen, in

other

*62 OF REVERIE. -SECT. XIX. 2.

other refpech well, was fuddenly feized focn after
her ufual menflruation, with this very wonderful
rnalady7 The difeafe began with vehement convul-
fions of ahnoft every mufcle of her body, with
great but vain efforts to vomit, * and the mod vio-
lent hiccoughs, that can be conceived : thefe were
fucceeded in about an hour with a fixed fpafm ; in
which one hand was applied to her head, and the
other to fupport k : in about half an hour thefe
eeafed, and the reverie began fuddenly, and was at
firft manifeft by the look of her eyes and counte-
nance, which feemed to exprefs attention. Then
fhe converfed aloud with imaginary perfons with
her eyes open, and could not for about an hour be
brought to attend to the flimulus of external ob-
jects by any kind of violence, which it was proper
to ufe : thefe fymptoms returned in this order every
day for five or fix weeks.

Thefe converfations were quite confident, and
we could underftand, what (he fuppofed her imagi-
nary companions to anfwer, by the continuation of
her part of the difcourfe. Sometimes (he was an-
gry, at other times (hewed much wit and vivacity,
but was mod frequently inclined to melancholy.
In thefe reveries (he fometimes fung over fome
mufic with accuracy, and repeated whole pages
from the Englifh poets. In repeating fome lines
from Mr. Pope's works me had forgot one word, and
began again, endeavouring to recollect it; when
fhe came to the forgotten word, it was fhouted
aloud in her ear, and this repeatedly to no purpofe;
but by many trials fhe at length regained it her?
felf.

Thefe paroxyfms were terminated with the appear-
ance of inexpreffible furprife, and great fear, from
which fhe was fome minutes in recovering herfelf,
Calling on her fitter with great agitation, and very
frequently underwent a repetition of convulfions,

apprentljr

SECT. XIX, 2. OF REVERIE. 263

apparently from the pain of fear. See Sect. XVII.

•

After having thus returned for about an hour
every day for two or three weeks, the reveries
feemed to become lefs complete, and fome of their
circumflances varied ; fo that (he could walk about
the room in them without running againft any of
the furniture ; though thefe motions were at firft
very unfteady and tottering. And afterwards me
once drank a diih of tea, when the whole appara-
tus of the tea-table was fet before her ; and expref-
fed fomc fufpicion, that a medicine was put into it,
and once feemed to fmell of a tuberofe, which was
in flower in her chamber, and deliberated aloud
about breaking it from the'ftem, faying, " it
would make her filler fo charmingly angry." At
another time in her melancholy moments (lie heard
the found of a palling beil, '* I wifh I was dead,"
me cried, liftening to the bell, and then taking off"
one of her fhoes, as (he fat upon the bed, " I love
the colour black," fays me, " a little wider, and a
little longer, even this might make me a coffin I" —
Yet it is evident, me was not fenfible at this timey
any more than formerly, of feeing or hearing any
perfon about her ; indeed when great light was
thrown upon her by opening the mutters of the
window, her trains of ideas feemed lefs melancho-
ly ; and when I have forcibly held her hands, or
covered her eyes, (lie appeared to grow impatient,
and would fay, (he could not tell what to do, for
fhe could neither fee nor move. In all thefe cir-
cumftances her pulfe continued unaffected as in
health. And when the paroxyfm was over, (he
could never recollect a (ingle idea of what had
palled in it.

This afloniming difeafe, after^the life of many
other medicines and applications in vain, was cured
by very large dofes of opium given about an hour

before

*&4 6 F R E V-.E R I E. SECT. XIX. 3. 4 $. &

before the expe&ed returns of the paroxyfms ; and
after a few relapfes, at the intervals of three ot
four months, entirely difappearetl. But (he conti-
liued at times to have other fymptoms of epilepfy.

3. We fhall only here coniider, what had hap-
pened during the time of her reveries, as that is
our prefent fubjecl ; the fits of convulfion belong
to another part of this treatife. Sett. XXXIV. 44.

There feems to have been no fufpenfion of voli*
lion during the fits of reverie, becaufe me endea-
voured to regain the loft idea in repeating the lines
of poetry, and deliberated about breaking the tube-
fofe and fufpe&ed the tea to have been medicated.

4. 1 he ideas and mufcular movements depend-
ing ^on fenfation were exerted with their ufual viva-
city, and were kept from being inconfiftent by the
power of volition, as appeared from her whole con-
verfation, and was explained in Sett. XVII. 3. 7.
and XVIII. 1 6.

5. The ideas and motions dependant on irrita-
tion during the firft weeks of her difeafe, whilft
the reverie was complete, were never fucceeded by
the fenfation of pleafure or pain; as (he neither
faw, heard, nor felt any of the furrounding objects.
Nor was it certain that any irritative motions fuc-
ceeded the ftimulus of external objects, till the re-
verie became lefs complete, and then (he could walk
about the room without running againft the furni-
ture of it. Afterwards, when the reverie became
ftill lefs complete from the ufe of opium, fome few
irritations were at times fucceeded by her attention
to them. As when (he fmelt at a tuberofe, and
drank a difh of tea, but this only when (he feemed
voluntarily to attend to them*

6. In common^life when tve liften to diftant
founds, or wifli to diflinguifh objecls in the night,
we are obliged flrongly to exert our volition to
difpofe the organs of fenfe to perceive them, and

to

SECT. XIX. 7. O F R E V E R I E. 26$

to fupprefs the other trains of ideas, which might
interrupt thefe feeble fenfations. Hence in the pre-
fent hiftory the ftrongeft ftimuli were not perceived,
except when the faculty of volition was exerted on
the organ of fenfe ; and then even common ftimuli
were fometimes perceived ; for her mind was fo
ftrenuoufly employed in purfuing its own trains of
voluntary or fenfitive ideas, that no common ftimuli
could fo far excite her attention as to difunite them;
that is, the quantity of volition or of fenfation al-
ready exifting was greater than any, which could
be produced in confequence of common degrees of
ftimutation. But the few ftimuli of the tuberofe,
and of the tea, which fhe did perceive, were fuch,
as accidentally comcided with the trains of thought,
which were palling in her mind ; and hence did not
difunite thofe trains, and create furprife. And their
being perceived at all was owing to the power of
volition preceding or coinciding with that of irri-
tation.

This explication is countenanced by a fact men-
tioned concerning a fomnambulift in the Laufanne
Tranfa&ions, who fcmetimes opened his eyes for a
fhort time to examine, where he was, or where his
ink-pot (food, and then fhut them again, dipping
his pen into the pot every now and then, and wri-
ting on, but never opening his eyes afterwards, al-
though he wrote on from line to line regularly, and
corrected fome errors of the pen, or in fpelling:
fo much eafier was it to him to refer to his ideas of
the pofitions of things, than to his perceptions of
them.

7. The afibciated motions perfifted in their ufual
channel, as appeared by the combinations of her
ideas, and the ufe of her mufcles, and the equality
of her pulfe ; for the natural motions of the arte-
rial fyftem, though origina'ly excited like other
motions by ftimulus, feem in part to continue by

their

*66 Of* REVERIE. Si-.cT.XlX 8. 9}

their aflociatibn with each other. As the heart of
a viper pulfates long after it is cut out of the body,
and removed from the ftimulus of the blood.

8. In the fection on fleep, it was obferved
that the nerves of fenfe are equally alive 'and fuf-
ceptible to 'irritation in that ftate, as when we are
awake ; but that they are fecluded from ftimulating
objects, or rendered unfit to receive them : but in
complete reverie the reverfe happens, the immedi-
ate organs of fenfe are e*xpofed to their ufual (li-
mn li ; but are either not excited into action at all,
or not into fp great action, as to produce attention
or fenfation.

The total forgetfulnefs of what Cartes in reveries ;
and the. furprife on recovering from them, are ex-
plained in Se&ion XVIII, 19. and in Section XVIL

3- 7-

9. It appears from hence, that rever e is a dif-

eafe of the epileptic or cataleptic kind, fmce the
paroxyfms of this young lady always began and
frequently terminated with convulfia^s ; and though
in its greateft degree it has been called fomnambu-
lation, or fleep-walking, it is totally different from
fleep ; becaufe the eflential character of ileep con-
lifts in the total fufpenfion of volition, which in re-
verie is not affected ; and tl>e eflential character of
reverie confifts not in the abfence of thofe irritative
motions of our fenfes, which are occafioned by the
ftimulus of external objects, but in their never
being productive of fenfation. So that during a fit
of reverie that if range event happens to the whole,
fyftem of nerves, which .occurs only to fome parti-
cular branches of them in thofe, who are a fecond
time expofed to the action of contagious matter.
If the matter of the fmall-pox be inferted into the
arm of one, who has previoufly had that difeafe, it
will (limulate the wound, but the general fenfation
or inflammation of the fyftem dees not follow,

which

fetcf. XIX. io. OF REVERIE. 267

which conftitutes the difeafe. See Sect. XII. 7. 6.

XXXIII. 2. 8.

10. The following is the definition or character
of complete reverie, i. The irritative motions
occafioned by internal ftimuli continue, thofe from
the ftimuli of external objects are either not pro-
duced at all, or are never fucceeded by fenfation or
attention, unlefs they are at the fame time excited
by volition. 2. The fenfltive motions continue,
and are kept confident by the power of volition.

3. The voluntary motions continue undifturbed.

4. The afibciated motions continue undifturbed.
Two other cafes of reverie are related in Section

XXXIV. 3. which further evince, that reverie is
an effort of the mind to relieve fome painful fenfa-
tion, and is hence allied to convulfion, and to in-
fanity. Another cafe is related in Clafs III. j,
2. 2.

VOL.I. T SECT,

OF VERTIGO. SECT, XX, ».

SECT. XX.

OF.VLRT1GO.

r .iteirjj- £t« a^jds* Js<r;:,i::-> i
I. We determine our perpendicularity by the apparent
motions of objects. A 'per > on hood-winked cannot
walk in a flraight line. Dizzinefi on looking from
a low er, in a room Jluined with uniform lozenge s^
on riding over fnow. 2. Di^zinefs from moving
objefts. A whirling 'wheel. Fluff nations of a river. '
^Experiment with a child. 3. Bizzincfs from our own
. motions and thofe of other objects. Riding over a
.broad ftr earn. Sea-Jicknefs* 5. Of turning round
.on me foot. Dervifes- in Turkey. Attention of tie
,mind prevents flight fea~ftcknefs. After a voyage
ideas of vibratory motions are ft ill perceived onjhore.
6. Ideas continue fome time after they are excited.
Circumftances of turning on one foot, Jlanding on a
tower i and walking in the dark, explained. 7. /r-
ritative ideas of apparent motions. Irr it alive ideas
of founds \ Battement of the found of bells and
organ-pipes. Vertiginous noife in the head. Irri~
tative motions of the flomach, intejHnes, and glands.
8. Symptoms thai accompany vertigo. Why vomit-
ing comes on in ftrokes of the palfy. By the motion
ef a fbip. By injuries on the head. Why motion
wakes fjck people vomit. 9.. Why drunken people
are vertiginous. Why ajlone in the ureter, or bile-
duff\ produces vomiting, i o. Why after a voyage
ideas of vibratory motions are perceived on Jborc.
1 1 . Kinds of vertigo and their cure. 1 2. Definition
of vertigo.

•*f*'jii£. '''"**&.'''':

T. IN learning to walk fre judge of the difta-mres
of the objeds, which we approach^ by the eye;,
and by obferving^their perpendicularity determine

our

SECT. XX. i. OF VERTIGO. 169

our own. This circumftance not having been at-
tended to by the writers on vifion, the difeafe call-
ed vertigo or dizzinefs has been little underftood.

When any perfon lofes the power of mufcular
a&ion, whether he is ereft or in a fitting pofture, he
finks down upon the ground : as is feen in fainting
fits, and other inftarices of great debility. Hence
it follows, that fome exertion of mufcular power is
neceffary to preferve our perpendicular attitude.
This is performed by proportionally exerting the
antagonist mufeles of the trunk, neck, and limbs ;
and if at any time in our locomotions we find our-
felves inclining to one fide, we either reflore our
equilibrium by the efforts of the mufeles on the
other fide, or by moving one of our feet extend
the bafe, which we reft upon, to the new center of
gravity.

But the moft eafy and habitual manner of deter-
mining our want of perpendicularity, is by attend-
ing to the apparent motion of the objecls within
the fphere of diftincl: vifion ; for this apparent mo-
tion of objecls, when we incline from our perpen-
dicularity, or begin to fall, is as much greater than
the real motion of the eye, as the diameter of the
fphere of diftinct vifion is to our perpendicular
height.

Hence no one, who is hood-winked, can walk
in a (traight line for a hundred fleps together ; for
he inclines fo greatly, before he is warned of his
want of perpendicularity by the fenfe of touch, not
having the apparent motions of ambient objects to
meafure this inclination by, that he is necefiitated
to move one of his feet outwards, to the right or
to the left, to fupport the new centre of gravity, and
thus errs from the line he endeavours to proceed
in.

For the fame reafon many people become dizzy,
when they look from the fumrmt of a tower, which

T 2, i*

27* Of VERTIGO. SECT. XX. *,

is raifed much above all other objects, as thefe ob-
jects are out of the fphere of diftinct vifion, and they
are obliged to balance their bodies by the lefs accu-
rate feelings of their mufcles.

There is another curious phenomenon belonging
to this place, if the circumjacent vifible objects are
fo fmall, that we do not diftinguifh their minute
parts ; or fo fimilar, that we do not know them
from each other ; we cannot determine our perpen-
dicularity by them. Thus in a room hung with a
paper, which is coloured over with fimilar fmall
txlack lozenges or rhomboids, many people become
dizzy ; for when they begin to fall, the next and
the next lozenge fucceeds upon the eye; which
fhey miftake for the firft, and are not aware, that
they have any apparent motion. But if you fix a
fheet of paper, or draw any other figure, in the
midft of thefe lozenges, the charm eeafes, and no
dizzinefs is perceptible.—- The fame occurs, when
we ride over a plain covered with (ROW without
trees or other eminent objects .

2. But after having compared vifible obje£ts at
reft with the fenfe of touch, and learnt to diftinguifh
their fhapes and fhades, and to meafure our want of
perpendicularity by their apparent motions, we come
to confrder them in real motion. Here a new diffi-
culty occurs, and we require fome experience to learn
the peculiar mode of motion of any moving objects,
before we can make ufe of them for the purpofes
of determining our perpendicularity. Thus fome
people become dizzy at the fight of a whirling wheel,
or by gazing on the fluctuations of a river, if no
fleady objects are at the fame time within the fphere of
their diflin-Ct vifion ; and wh-en a child firft can (land
erect upon his legs, if you gain his attention to a
white handkerchief fteadily extended like a fail, and
afterwards make it undulate, he inftantly lofes his-
perpendicularity, and tumbles on the ground.

3- ^

. XX. 3. 4. OF VERTIGO. 27*

3. A fecond difficulty we have to encounter is to
diftinguifh our own real movements from the appa-
rent motions of objects. Our daily praclice of walk-
ing and riding on horfeback foon inftructs us with
accuracy to difcern thefe modes of motion, and to
afcribe the apparent motions of the ambient objects to
ourfelves ; but thofe which we have not acquired by
repeated habit, continue to confound us. So as we
ride on horfeback the trees and cottages, which oc-
cur to us, appear at reft ; we can meafure their dif-
tances with our eye, and regulate our attitude by
them : yet if we carelefsly attend to diftant hills or
woods through a thin hedge, which is near us, we
obferve the jumping and progreffive motions of them ;
as this is increafed by the parallax of thefe objects ;
which we have not habituated ourfelves to attend to.
When firft an European mounts an elephant fixteen
feet high, and whole mode of motion he is not ac-
cuftomed to, the objects feem to undulate, as he
pafles, and he frequently becomes fiek and vertigN
nous, as I am well informed. Any other unufuai
movement of our bodies has the fame eftect5 as riding
backwards in a coach, fwinging on a rope, turning
round fwiftly on one leg, fcating on the ice, and a
thoufand others. So after a patient has been lopg
confined to his bed, when he firft attempts to walk,
he finds himfelf vertiginous, and is obliged by prac-
tice to learn again the particular modes of the appa-
rent motions of objects, as he walks by them.

4. A third difficulty, which occurs to us in learn-
ing to balance ourfelves by the eye, is, when both
ourfelves and the circumjacent objects are in real
motion. Here it is neceffary that we mould be ha-
bituated to both thefe modes of motion in order to
preferve our perpendicularity. Thus on horfeback
we accurately obferve another perfon whom we
meet, trotting towards, without confounding his
jumping and progreflive motion with our own, be-

caufe

*9* O P V E R T I G O. SECT. XX. f,

caufe we have been accuftomed to them both ; that
is, to undergo the one, and to fee the other at the
fame time. But in riding over a broad and fluc-
tuating ftream, though we are well experienced in
the motions of our horfe, we are liable to become
dizzy from our inexperience in that of the water.
And when firii: we go on (hip-board, where the move-
ments of ourfelves, and the movements of the large
waves are both new to us, the vertigo is almoft un-
avoidable with the terrible ficknefs, which attends it.
And this I have been affured has happened to ft-
veral from being removed from a large fliip into q.
fmall one ; and again from a fmall one into a man of
war.

5. From the foregoing examples it is evident, that,
when we are furrounded with unufual motions, we
Jofe' our perpendicularity : but there are fome pecu-
liar circumstances attending this effeft of moving
qbje&s, which we come now to mention, and (hall
hope from the recital of them to gain fome infight
into the manner of their production.

When a child moves round quick upon one foot,
the circumjacent objects become quite indiftincl:, as
their diftance increafes their apparent motions ; and
this great velocity confounds both their forms, and
their colours, as is feen in whirling round a many
coloured wheel ; he then lofes his ufual method of
balancing himfelf by vifion, and begins to ftagger,
and attempts to recover himfelf by his mufcuhr
feelings. This daggering adds to the inftability of
the vifible obje&s by giving a vibratory motion
befides their rotatory one. This child then drops
upon the ground, and the neighbouring objects
ieem to continue for fome feconds of time tq circu-
late around him, and the earth under him appears
to librate like a balance. In fome feconds of time
thefe fenfations of a continuation of the motion of
pbjefts yanifh 5 but if he continues turning round

fome what

SECT. XX. 5. OF VERTIGO. , 273

fomewhat longer, before he falls, ficknefs and vo-
miting are very liable to fucceed. But none of
thefe circumftances affect thofe who have habituated
themfelves to this kind of motion, as the dervifes
in Turkey, amongft whom thefe fwift gyrations
are a ceremony of religion.

In an open boat palling from Leith to Kinghorn
in Scotland, a fudden change of the wind fhook
the utidiftended fail, and flopt our boat ; from this
unufual movement the paflengers all vomited ex-
cept myfelf I obferved, that the undulation of
the (hip, and the inftability of all vifible objects,
inclined me llrongly to be fick ; and this continued
or increafed, when I clofed my eyes, but as often
as I bent my attention with energy on the manage-
ment and mechanifm of the ropes and fails, the
ficknefs ceafed ; and recurred again, as often as I
relaxed this attention ; and I am aflured by a gen-
tleman of obfervation and veracity, that he has
more than once obferved, when the veflel has been
in immediate danger, that the fea-ficknefs of the
paflengers has inftantaneouily ceafed, and recurred
again, when the danger was over.

Thofe, who have been upon the water in a boat
or (hip fo long, that they have acquired the necef-
fary habits of motion upon that unflable element,
at their return on land frequently think in their re-
veries, or between ileeping and waking, that they
obferve the room, they fit in, or fome of its furni-
ture, to librate like the motion of the veflel.
This I have experienced myfelf, and have been
told, that after long voyages, it is fome time before
thefe ideas entirely vanifh. The fame is obfervable
in a lefs degree after having travelled fome days in
a ftage coach, and particularly when we lie down
in bed, and compofe ourfelves to fleep; in this cafe
it is obfervable, that the rattling noife of the
coach, as well as the undulatory motion, haunts

us.

274 OF VERTIGO. SECT. XX. 6,

us. The drunken vertigo, and the vulgar cuftom of
rocking children, will be confidered in the next
Section.

6. The motions, which are produced by the
power of volition, may be immediately flopped by
the exertion of the fame power on the antagonifl
mufcles ; otherwife thefe with all the other clafles
of motion continue to go on, fome time after they
are excited, as the palpitation of the heart conti-
nues after the objeft of fear, which occafioned it,
is removed. But this circijmftance is in no clafs
of motions more remarkable than in thofe depen-
dent on irritation ; thus if any one looks at the fun,
-and then covers his eyes witji his hand, he will for
many feconds of time, perceive the image of the
fun marked on his retina: a fimilar image of all
other vifible objects would remain fome time form-
ed on the retina, but is extinguifhed by the perpe^
tual change of the motions of this nerve in our
attention to other objects. To this mult be added,
that the longer time any movements have continu-
ed to be excited without fatigue to the organ, the
longer will they continue fpontaneoufly, after the
excitement is withdrawn : as the tafte of tobacco
in the mouth after a perfon has been fmpaking it.
This tafte remains To ftrong, that if a perfon con-
tinues to draw air through a tobacco pipe lr\ the
dark, after having been fmoking fome time, he
cannot diftinguifh whether his pipe be lighted op
not.

From thefe two confederations it appears, that
the dizzinefs felt in the head, after feeing objects
in unufuai motion, is no other than a continuation
pf the motions of {he optic nerve excited by thofe
objects, and which engage our attention. Thus on
turning round on one foot, the vertigo continues
for fome feconds of time after the perfon is faller}
pn the ground ; and the longer he has continued

to

SECT. XX. 7. OF VERTIGO. 275

jo revolve, the longer will continue thefe fucceffive
motions of the parts of the optic nerve. See an
additional note at the end of this volume.

Any one who (lands alone on the top of a high
, tower, if he has not been accuftomed to balance
himfelf by objects placed at fuch diftances and with
fuch inclinations, begins to dagger, and endea-
vours to recover himfelf by his mufcular feelings.
During this time the apparent motion of objects at
a diftance below him is very great, and the fpectra
of thefe apparent motions continue a little time
after he has experienced them ; and he is perfua-
ded to incline the contrary way to counteract their
effects ; and either immediately falls, or applying
his hands to the building, ufes his mufcular feelings
to preferve his perpendicular attitude, contrary to
the erroneous perfuafions of his eyes. Whilft the
perfpn, who walks in the dark, daggers, but with-
out dizzinefs ; for he neither has the fenfation of
moving objects to take off his attention from his
mufcular feelings, nor has he the fpectra of thofe
motions continued on his retina to add to his con-
fufion. It happens indeed fometimes to one (land-
ing on a tower, that the idea of his not having
room to extend his bafe by moving one of his feet
outwards when he begins to incline, fuperadds
fears to his other inconveniences ; which like fur-
prife, joy, or any great degree of fenfation, ener-
vates him in a moment^ by employing the whole
fenforial power, and by thus breaking all the affo-
ciated trains and tribes of motion.

j. The irritative ideas of objects, whilft we are
awake, are perpetually prefent to our fenfe of fight ;
as we view the furniture of our rooms, or the
ground, we tread upon, throughout the whole day
without attending to it. And as our bodies are
never at perfect reft during our waking hours,
phefe irritative ideas of objects are attended perpe-
tually

276 OF VERTIGO. SECT. XX. 7.

tually with irritative ideas of their apparent moti-
ons. The ideas of apparent motions are always
irritative ideas, becaufe we never attend to them,
whether we attend to the objects themfelves, or to
their real motions, or to neither. Hence the ideas
of the apparent motions of objefts are a complete
circle of irritative ideas, which continue throughout
the day.

Alfo during all our waking hours, there is a
perpetual confufed found of various bodies, as of
the wind in our rooms, the fire, diftant converfa-
tions, mechanic bufmefs ; this continued buzz, as
we are feldotn quite motionlels, changes its loud-
nefs perpetually, like the found of a bell ; which
rifes and falls as long as it continues, and feems to
pulfate on the ear. Thus any one may experience
by turning himfelf round near a waterfall ; or by
finking a glafs bell, and then moving the direction
of its mouth towards the ears, or from them, as
long as its vibrations continue. Hence this undu-
lation of indiftincl: found makes another concomi-
tant circle of irritative ideas, which continues
throughout the day.

We hear this undulating found, when we are
perfectly at reft ourfelves, from other fonorous
bodies befides bells ; as from two organ-pipes,
which are nearly but not quite in unifon, when
they are founded together. When a bell is ftruck,
the circular form is changed into an elliptic one ;
the longed axis of which, as the vibrations conti-
nue, moves round the periphery of the bell ; and
\vheneither axis of this eliipfe is pointed towards
our ears, the found is louder ; and lefs when the
intermediate parts of the ellipfe are oppofite to us.
The vibrations of the two organ -pipes may be
compared to Nonius's rule ; the found is louder,
when they coincide, and lefs at the intermediate
times. But, as the found of bells is the mod

familiar

X. 8. OF VERTIGO. ±77

familiar of thofe founds, which have a confidera^
ble battement, the vertiginous patients, who at-
tend to the irritative circles of founds above de-
fcribed, generally compare it to the noife of
bells.

The periftaltic motions of our ftomach and in-
teftines, and the fecretions of the various glands,
are other circles of irritative morions, fome of them
more or lefs complete, according to our abftinence
or fatiery.

So that the irritative ideas of the apparent motions
of objects, the irritative battements of founds, and
the movements of our bowels and glands compofe
a great circle of irritative tribes of motion: and
when one confiderable part of this circle of motions
becomes interrupted, the whole proceeds inconfu-
fion, as defcribed in Seftion XVII. i. 7. on Catena-
tion of Motions,

8. Hence a violent vertigo, from whatever caufe
it happens, is generally attended with undulating
noife in the head, perverfions of the motions of the
ftomach and duodenum, unufual excretion of bile
and gaftric juice, with much pale urine, fometimes
with yellownefs of the (kin, and a difordered fecre-
tion of almoft every gland of the body, till at
Jength the arterial fyftem is affected, and fever fuc-
ceeds.

Thus bilious vomitings accompany the vertigo
occafioned by the motion of a (hip ; and when the
brain is rendered vertiginous by a paralytic affection
of any part of the body, a vomiting generally
enfues, and a great difcharge of bile : and hence
great injuries of the head from external violence
are fucceeded with bilious vomitings, and fome-
times with abfcefles of the liver. And hence,
when a patient is inclined to vomit from other
caufes, as in fome fevers, any motions of the at-
tendants in his room, or of himfelf when he is

raifed

2,c5 OF VERTIGO. SECT. XX. 9. 10.

taifed or turned in his bed, prefently induce the
vomiting by fuperadding a degree of vertigo.

9, And converfely it is very ufual with thofe,
whofe ftomachs are affected from internal caufes,
to be afflidted with vertigo, and noife in the head ;
fuch is the vertigo of drunken people, which con-
tinues, when their eyes are clofed, and themfelves
in a recumbent pofture, as well as when they are in
an .erect pofture, and have their eyes open. And
thus the irritation of a (ione in the bile-duel, or in
the ureter, or an inflammation of any of the
inteftines, are accompanied with vomitings and

vertigo.

In thefe cafes the irritative motions of the fto-
mach, which are in general not attended to, become
fa changed by fome unnatural flimulus, as to be*
come uneafy, and excite our ienfation or attention.
And thus the other irritative trains of motions,
which are aflbciated with it, become difordered by
their fympathy. The fame happens, when a piece
of gravel (licks in the ureter, or when fome part of
the inteftinal canal becomes inflamed. In thefe
cafes the irritative mufcular motions are firft dif-
turbed by unufuai ftimulus, sad a difordered aclion
of the fenfual motions, or dizzinefs enures. While
in fea-ficknefs the irritative fepfual motions, as.
vertigo, precedes ; and the difordered ? irritative
mufcular motions, as thofe of the-iloia^ch in yp-
mhing, follow.

10. When thefe irritative motions are difturbed?
if the degree be not very great, the exertion of
voluntary attention to any other object, or any
fadden fenfation, will disjoin thefe new habits of
motion. Thus fome drunken people have becpme
fober immediately, when any accident has ftrongly
excited their attention ; and fea iicknefs has vanifn-
ed, when the fhip has been in danger. Hence
wheu our attention to other objecls is moft relaxed,
•b? as.

8p.cT.XX.il. OF VERTIGO. 279

as jufl before we fall aileep, or between our reve-
ries when awake, thefe irritative ideas of motion
and found are mod liable to be perceived ; as thofe
who have been at fea, or have travelled long in a
coach, feem to perceive the vibrations of the (hip,
or the rattling of the wheels, at thefe intervals ;
which ceafe again, as foon as they exert their atten-
tion. That is, at thofe intervals they attend to the
apparent motions, and to the battement of founds
of the bodies around them, and for a moment
miftake them for thofe real motions of the (hip,
and noife of wheels, which they had lately been
accuftomed to : or at thefe intervals of reverie, or
on the approach of fleep, thefe fuppofed motions
or founds may be produced entirely by imagina-
tion.

We may conclude from this account of vertigo,
that fea-ficknefs is not an effort of nature to relieve
herfelf,, but a neceffary confequence of the affocia-
tions of catenations of animal motions. And may
thence infer, that the vomiting, which attends the
gravel in the ureter, inflammations of the bowels,
and the commencement of fome fevers, has a fimi-
lar origin, and is not always an effort of the vis
medicatrix naturae. But where the adion of the
organ is the immediate confequence of the (limu-
lating caufe, it is frequently exerted to dillodge
that iiimulus, as in vomiting up an emetic drug ;
at other times, the aftion of an organ is a general
effort to relieve pain, as in convulsions of the loco-
motive mufeles ; other actions drink up and carry
on the fluids, as in abforption and fecretion ; all
which may be termed efforts of nature to relieve,
or to preferve herfelf.

u. The cure of vertigo will frequently depend
on our previoufly inveftigating the caufe of it, which
irom what has been delivered above may originate
from the diforder of any part of the great trihes of

irritative

*So OF VERTIGO. SECT. XX. ft.

irritative motions, and of 'the aflbciate motions
catenated with them.

Many people, when they arrive at fifty or fixty
years of age, are affected with flight vertigo;
which is generally but wrongly afcribed to indigef-
tion, but in reality arifes from a beginning defect
of their fight ; as about this time they alfo find it
neceifary to begin to ufe fpectacles* when they read
fmall prints, efpecially in winter^ or by candle light,
but are yet able to read without them during the
fummer days, when the light is ftronger. Ihefe
people do not fee objects fo diftinctly as formerly j
and by exerting their eyes more than ufual, they
perceive the apparent motions of objects, and con*
found them with the real motions of them $ and
therefore cannot accurately balance themfelves fo
as eafily to preferve their perpendicularity by
them.

That is, the apparent motions of objects, which
are at reft, as we move by them, mould only excite
irritative ideas : but as thefe are now become lefs
diftirict, owing to the beginning imperfection of
our fight, we are induced voluntarily to attend ta
them ; and then thefe appaient motions become
fucceeded by fenfation ; and thus the other parts of
the trains of irritative ideas, or irritative mufcular
motions, become difordered, as explained above.
In thefe cafes of flight vertigo I have always pro-
mifed my patients, that they would get free from it
in two or three months, as they mould acquire the
habit of balancing their bodies by lefs diftinct ob-
jects, and have feldom been miftaken in my prog-
noftic.

There is an auditofy vertigo, which is called a
noife in the head, explained in No. *;. of this fecti-
on, which alfo is very liable to affect people in the
advance of life, and is owing to their hearing lefs
perfectly than before. This is fometimes called a
* ringing

SECT. XX. ii. OF VERTIGO. *St

ringing, and fometimes a fmging, or buzzing, in
the ears, and is occafioned by our firft experiencing
a difagreeable fenfation from our not being able
diftindly to hear the founds, we ufed formerly to
hear diftindly. And this difagreeable fenfation ex-
cites defire and confequent volition ; and when we
voluntarily attend to fmali indiftinft founds, even
the whifpering of the air in a room, and the pulfa-
tions of the arteries of the ear are fucceeded by
fenfation ; which minute founds ought only to have
produced irritative feniuai motions, or unperceived
ideas. See Section XVII. 3. 6. Thefe patients
after a while lofe this auditory vertigo, by acqui-
ring a new habit of not attending voluntarily to
thefe indiftinct founds, but contenting themfelves
with the lefs accuracy of their fenfe of hearing.

Another kind of vertigo begins with the diforder-
ed action of fome irritative mufcular motions, a»
thofe of the flomach from intoxication, or from
emetics ; or thofe of the ureter, from the ftimulus
of a (lone lodged in it ; and it is probable, that
the difordered motions of fome of the great con-
geries of glands, as of thofe which form the liver,
or of the inteftinal canal, may occafion vertigo in
confequence of their motions being affociated or
catenated with the great circles of irritative moti-
ons ; and from hence it appears, that the means of
cure mud be adapted to the caufe.

To prevent fea-ficknefs it is probable, that the
habit of fwinging for a week or two before going
on (hipboard might be of iervice. For the vertigo
from failure of light, fpeclacies may be ufed. For
the auditory vertigo, aether may be dropt into the
ear to ftimulate the part, or to diffolve ear-wax, if
fuch be a part of the caufe. For the vertigo arifing
from indigeftion, the peruvian bark and a blifter
are recommended. And for that owing to a (tone

in

Qfr VE&TIGO. Sicr.XX. ii.

in the ureter, venefe&ion, cathartics, opiates, fa!
foda aerated.

12. Definition of vertigo, i. Some of the irri-
tative fenfual, or mufcular motions, which were
ufually not fucceeded by fenfation, are in this dif-
eafe fucceeded by fenfation ; and the trains or
circles of motions, which were ufually catenated
with them, are interrupted, or inverced, or proceed
in confufion. 2. The fenfitive and voluntary mo-
tions continue undifturbed. 3. The afibciate trains
or circles of motions continue ; but their catena-
tions with fome of the irritative motions are dif-
ordered, or inverted, or dhTevered.

SECT.

SECT. XXI. i. OF DRUNKENNESS. 28^

SECT. XXI.

OF DRUNKENNESS.

I. Sleep from fatiety of hunger. From rocking children.
From ur if or?n founds. 2. Intoxication from comriion
food after fat ^te and Inanition. 3. From wine or
opium. Chllnefs after meals. Vert/go- Why plea-
fur e is produced by intoxication, and by fwinging and
rocking children. And why pain is relie-ved by it.
4. Why drunkards ftagger and fiammer, and are
liable to weep. 5. And become ddirlous^ flecpy, and
Jlupid. 6. Or make pale urine and vomit. 7. Ob-
jehs are feen double. 8. Attention of the mind dl-
minifhes drunkenncfs. 9. Difordered irritative mo-
tions of all the fenfes. io. Difeafes from drunken-
nefs. ii. Definition of drunkennefs.

I. IN the (late of nature when the fenfe of hun-
ger is appeafed by the (limulus of agreeable food, the
bufmefs of the day is over, and the human favage
is at peace with the world, he then exerts little at-
tention to external objects, pleafmg reveries of ima-
gination fucceed, and at length Deep is the refult :
till the nourimment which he has procured, is car-
ried over every part of the fyftem to repair the inju-
ries of action, and he awakens with frefh vigour,
and feels a renewal of his fenfe of hunger.

The juices of fome bitter vegetables, as of the pop-
py and thelauro-cerafus, and the ardent fpirit pro-
duced in the fermentation of the fugar found in ve-
getable juices, are fo agreeable to the nerves of the
ftomach, that, taken in a fmall quantity, they in-
ftantly pacify the leafe of hunger j and the iuatten-
lion to external ftimuli with the reveries of imagi-

VOL. I. U nation.

284 OF DRUNKENNESS.- SECT. XXI. 2. £

nation, and fleep, fucceeds, in the fame manner as
when the ftomach is filled with other lefs intoxicat-
ing food.

This inattention to the irritative motions occafiori-
ed by external ftimuli is a very important circum-
ftancein the approach of fleep, and is produced in-
young children by rocking their cradles : during
which all vifible objects become indiftinct to them.
An uniform foft repeated found, as the murmurs of
a gentle current, or of bees, are faid to produce
the fame effect, by prefenting indiitindt ideas of in*
eonfequential founds, and by thus ftealing our at-
tention from other objects, whiift by their conti-
nued reiterations they become familiar themfelves,
and we ceafe gradually to attend to any thing, and
fleep enfues.

2. After great fatigue or inanition, when the
ftomach is fuddenly filled with flefh and vegetable
food, rhe inattention to external ftimuli, and the
reveries of imagination, become fo confpicuotis as
to amount to a degree of intoxication. The fame is
at any time produced by fuperadding a little wine OP
©pium to our common meals ; or by taking thefe fe-
parately in confiderable quantity , and this more
efficacioufly after fatigue or inanition -y becaufe a
lefs quantity of any ftimulating material will excite
an organ into energetic a6tion, after i£ has lately
been torpid from defe£tof (timulus; as objects ap-
pear more luminous, after we have been in the dark;
and becaufe the fufpenfion of volition,- which is the
immediate caufeof fleep, is fooner induced, after a
continued voluntary exertion has in part exhausted
the fenforial power .of volition ; in the fame manner
as we cannot contract a fmgle mufcle long together
without intervals of inaction.

3. In the beginning of intoxication we are inclined
to fleep, as mentioned above, but by the excite-
ment of external circumftances, as of noife, light^

bufmefc,

SECT. XXI 3. OF DRUNKENNESS. 285

bufinefs, or by the exertion of volition, we prevent
the approaches of it, and continue to take into our
flomach greater quantities of the inebriating mate-
rials. By thefe means the irritative movements of the
flomach are excited into greater action than is natu-
ral : and in confequence all the irritative tribes and
trains of motion, which are catenated with them,
become fufceptible of flronger action from their ac-
cuflomed ftimuli ; becaufe thefe morions are excited
both by their ufual irritation, and by their aifocia-
tion with the increafed actions of the ftomach and
lacteals. Hence the (kin glows, and the heat of the
body is increafed, by the more energetic action of
the whole glandular fyftem ; and pleafure is intro-
duced in confequence of thefe increafed motions
from internal flimulus. According to Law 5. Sect.
IV. on Animal Caufation.

From this great increafe of irritative motions from,
internal flimulus, and the increafed fenfation intro-
duced into the fyftem in confequence ; and fecondly,
from the increafed fenfitive motions in confequence
of this additional quantity of fenfation, fo much
fenforial power is expended, that the voluntary power
becomes feebly exerted, and the irritation from the
flimulus of external objects is lefs forcible ; the ex-
ternal parts of the eye are not therefore voluntarily-
adapted to the diftances of objects, whence the ap-
parent motions of thole objects either are feen dou-
ble, or become too indiftinct for the purpofe of ba-
lancing the body, and vertigo is induced.

Hence we become acquainted with that very cu-
rious circumflance, why the drunken vertigo is at-
tended with an increafe of pleafure -, for the irritative
ideas and motions occaficned by internal ftimulus,
that were not attended to in our fober hours, are
now juft fo much increafed as to be fucceeded by
pleafurable fenfation, in the fame manner as the
more violent motions of our organs are fucceeded by

U a painful

286 OF DRUNKENNESS.- SECT. XXI. j,

painful fenfaticn. And hence a greater' quantity of
pleafurable fenfation is introduced into the conftitu-
tion ; which is attended in feme people with an in-
creafe of benevolence and good hurnour.

If the apparent motions of objects is much increa-
fed, as when we revolve on one foot, or are fwung
on a rope, the ideas of thefe apparent motions are
alfo attended to, and are fucceeded with pleafurable'
fenfation, till they become familiar to us by frequent
life. Hence children areatfirft delighted with thefe
kinds of exercife, and with riding, and failing, and
hence rocking young children inclines them to fleep.
For though in the vertigo from intoxication the
irritative ideas of the apparent motions of objects
are indtflinct from their decreafe of energy : yet
in the vertig,o occafioned by rocking or fwinging
the irritative ideas of the apparent motions of ob-
jects are increafed in energy, and hence they induce
pleafure into the fyftem, but are equally indiftinct,.
and in confequence equally unfit to balance our-
felves by.- This addition of pleafure precludes de-
fire or averfion, and in confequence the voluntary-
power is feebly exerted, and on this account rock-
ing young children inclines them to ileep.

In what manner opium and wine act in relieving
pain is another article, that well deferves our atten-
tion. There are many pains that originate from de-
fect as well as from: excefs of ftimulus ; of thefe are
thofe of the fix appetites of hunger, thiril, lull, the
want of heat, of (Mention, and of frefh air. Thus-
if our cutaneous- capillaries ceafe to act from the
diminifned ftimulus of heat, when we are expofed to
cold weather, or our ftomach is uneafy for want of
food ; thefe are both pains from defect of ftimulus,
and in confequence opium,, which, llimulates all the
moving fyftem into increafed action, muft relieve,
them. But this is not the cafe in thofe pains, which,
arife from excefs of ftimulus, as in violent inflamma^

tions :

SECT. XXI. 4. 5. OF DRUNKENNESS. 287

cions : in thafe the exhibition of opium is frequent-
ly injurious by increafing the adion of the fyftem
already too great, as in inflammation of the bowels
mortification is often produced by the ftimulus of
opium. Where, however, no fuch bad confequen-
ces follow ; the ftimulus of opium, by incieafing all
the motions of the fyftem, expends fo much of the
fenforial power, that the actions of the whole fyftem
foon become feebler, and in confequence thofe which
produced the pain and inflammation.

4. When intoxication proceeds a little further,
(he quantity of pleafurable fenfation is fo far in-
creafed, that all defire ceafes, for there is no pain in
the fyftem to excite it. Hence the voluntary exer-
tions are diminifhed, ftaggering and ftammering fuc-
ceed ; and the trains of ideas become more and
more inconfiftent from this defect of voluntary ex*
ertion, as explained in the lections on deep and re-
verie, whilft thofe pafTions which are unmixed with
volition are more vividly felt, and (hewn with lefs
referve ; hence pining love, or fuperftitious fear, and
the maudlirg tear dropped on the remembrance of
the moft trifling diftrefs.

5. At length all thefe circumftances are increafed;
the quantity of pleafure introduced into the fyftem
by the increafed irritative mufcular motions of the
whole fanguiferous, and glandular, and abforbent
fyftems, becomes fo great, that the organs of fenfe
are more forcibly excited into action by this internal
pleafurable fenfation, than by the irritation from the
flimulus of external objects. Hence the drunkard
ceafes to attend to external ftimuli, and as volition
js nowalfo fufpended, the trains of his ideas become
totally inconfiftent as in dreams, or delirium : and
at length a ftupor fucceeds from the great ex-
hauftion of fenforial power, which probably does
not even admit of dreams, and in which, as in apo-
plexy, no motions continue but thofe from internal

ia from fenfation, and from affociation.

6. In

288 OF DRUNKENNESS. SECT. XXI. 6. 71

6. In other people a paroxyfm of drunkennefs has
another termination ; the inebriate, as foon as he
begins to be vertiginous, makes pale urine in great
quantities and very frequently, and at length be-
comes fick, vomits repeatedly, or purges, or has
profufe fweats, and a temporary fever enfues with a
quick (Irong pulfe. This in fome hours is fucceeded
by flecp ; but the unfortunate bacchanalian does not
perfectly recover himlelf till about the fame time of
the fucceeding day, when his courfe of inebriation
began. As fhewn in ^^ect XVII. r. 7. on Catena-
tion. Th£ tempoiarv fever \vith (Irong pulfe is ow-
ing to the fame cauitr as the glow on the fk»n men-
tioned in the third paragraph of this Section : the
flow of urine an<4 fickneis arifes fiorri the whole fyi-
tem of irritative motions being thrown into confu-
fion by their allbciaticns with each other ; as in fea-
ficknefs, mentioned in Seel. XX. 4 on Vertigo : ancj
which is more fully explained in bsct. XXIX. on
Diabetes.

7. In this vertigo from internal caufes we fee ob-
jects double, as two candles inftead of one, which is
thus explained. Two lines drawn through the axes
of our two eyes meet at the object we attend to :
this angle of the optic axes increafes or diminiflies
with the lefs or greater diitances of objecls. All ob-
jects before or behind the place where this angle is
formed, appear double; as any one may obferve by
holding up a ppn between his eyes and the candle ;
when he looks attentively at a fpot on the pen, and
careicfsly at the candle, it will appear double ; and
the reverfe when he looks attentively at the can-
dle and careleisly at the pen ; fo that in this cafe the
mufcies of the eye, like thofe of the limbs, Dagger
and are difobedicnr to the expiring efforts of voli-
tion Numerous objects are indeed fometimes feen
by the inebriate, occafioned by the refractions made
by the tears, which it and upon his eye-lids.

8. This

SECT. XXI. 8. 9. OF DRUNKENNESS, 2-89

8. This vertigo alfo continues, when the inebriate
lies in his bed, in the dark, or with his eyes clofedj
and this more powerfully than when he is erect, and
in the light. For the irritative ideas of the apparent
motions of objeds are now excited by irritation from
internal ftimulus, or by afibciation with other irri-
tative motions ; and the inebriate, like one in a
dream, believes the objects of thefe irritative mo-
tions to be prefent, and reels himfelf vertiginous. I
have obferved in this fituation, fo long as my eyes
and mind were intent upon a book, the ficknefs and
vertigo ceafed, and were renewed again the moment
I difcontinued this attention ; as was explained in
the preceding account of fea-ficknefs. Some drunken
people have been known to become fober inftantly
from fome accident, that has ftrongly excited their
attention, as the pain of a broken bone, or the
news of their houfe being on fire.

9. Sometimes the vertigo from internal caufes, as
from intoxication, or at the beginning of fome fevers,
becomes fo univerfal, that the irritative motions
which belong to other organs of fenfe are fucceeded
by fenfation or attention, as well as thofe of the eye.
The vertiginous noife in the ears has been explained
in Se£t. XX. on Vertigo. The tafte of the faliva, which
in general is not attended to, becomes perceptible, and
jthe patients complain of a bad tafte in their mouth.

The common fmellsof the furroundingairfometimes
excite the attention of thefe patients, and bad fmell?
are complainedof, which to otherpeople are impercep-
tible. The irritative motions that belong to the fenfe
of prefTure, or of touch, areattendedto, andthepatient
.conceives the bed to librate, and is fearful of falling
out of it. The irritative motions belonging tothefenfes
of diftention, and of hear, like thofe above mentioned,
become attended to at this time : hence we feel the pul-
fationof our arteries all over us, and complain of heat,
or of cold in parts of the body where there is no ac-
cumulation or diminution of a&ual heat. AH which

i$o OF DRUNKENNESS. SECT. XXI. 10.

are to be explained, as in the laft paragraph, by the
irritative ideas belonging to the various fenfes being
now excited by internal flimuli, or by their adora-
tions with other irritative motions. And that thp
inebriate, like one in a dream, believes the external
objects, which ufually caufed thefe irritative ideas, tq
be now prefent.

TO. The difeafes in confequence of frequent ine-
briety, or of daily taking much vinous fpirit without
inebriety, confiit in the paralyfis which is liable to
fucceed violent (limulation. Organs, whofe actions
are affociated with others, are frequently more af-
fected than the organ, which is ftimulated into too
violent action. See Sect. XXIV. 2, 8. Hence in,
drunken people it generally happens, that the; fecre-
tpry veflels of the liver become firft paralytic, and a,
torpor with confequent gall-ftones or fchirrus of this
•vifcus is induced with concomitant jaundice ; other-
wife it becomes inflamed in confequence of previous,
torpor, and this inflammation is frequently transfer-
red to a more fenfible part, which is aflbciated with
it, and produces the gout, or the rofy eruption of
the face, orforne other leprous eruption on the head,
or arms, or legs. Sometimes the ftomach is firft
affected, and paralyfis of the lacteal fyitem is indu-
ced : whence a total abhorrence from Hem-food, and
general emaciation. In others the lymphatic fyftem
is affected with paralyfis, and dropfy is the confe-
quence. In Tome inebriates the torpor of the liver
produces pain without apparent fchirrus, or gall-
hones, or inflammation, or confequent gout, and in
thefe epilepfy or irifanity are often the confequence.
All which will be more fully treated of in the courfe
of this work.

I am well aware that it is a common opinion, that
the gout is as frequently owing to gluttony in eating,
as to intemperance in drinking fermented or fpiri-
tuous liquors. To this I anfwer, that I have feen

no
" '

SECT. XXI. 10. OF DRUNKENNESS. 29*

no perfon afflicted with the gout, who has not drank
freely of fermented liquor, as wine and water, or
[mall beer : though as the difpofition to all the dif-
eafes, which have originated from intoxication, is in
fome degree hereditary, a lefs quantity of fpirituous
potation will induce the gout in thofe, who inherit
the difpofition from their parents. To which I rnuft
add, that in \oung people therheumatiimis frequent-
ly miftaken for the gout.

Spice is feldom taken in fuch quantity as to do any
material injury to the fyftem, flefh meats as well as
vegetables are the natural diet of mankind ; with
thefe a glutton maybe crammed up to the throat,
and fed like a flailed ox ; but he will not be difeafed,
unlefs he adds fpirituous or fermented liquor to his
fooJ. This is well known in the diftilleries, where
the fwine, which are fattened by the fpirituous fedi-
ments of barrels, acquire difeafed livers. But mark
•what happens to a man, who drinks a quart of
wine or of ale, if he has not been habituated to it.
He loies the ufe both of his limbs and of his un<-
derftanding ! He becomes a temporary idiot, and has
a temporary ftroke of the palfy ! And though he
{lowly recovers after fome hours, is it not reafonable
to conclude, that a perpetual repetition of fo power-
ful a poifon mud at length permanently affecl: him ?
If a perfon accidentally becomes intoxicated by eat-
ing a few muftirooms of a peculiar kind, a general
alarm is excited, and he is faid to be poifoned, and
emetics are exhibited ; but fo familiarifed are we to
the intoxication from vinous fpirit, that it occafions
laughter rather than alarm.

There is however confiderable danger in too hafti-
ly difcontinuing the ufe of fo ftrong a ftimulus, left
the torpor of the fyftem, or paralyfis, mould fooner
be induced by the omiflion than the continuance of
this habit, when unfortunately acquired. A golden
pie for determining the quantity, which may with

fafety

292 OF DRUNKENNESS SECT. XXI. u.

fafety be difcontinued, is delivered in Section XII.
7. 8.

u. Definition of drunkennefs. Many of the ir-
ritative motions are much increafed in energy by in-
ternal ftimulation.

2. A great additional quantity of pleafurable
fenfation is occafioned by this increafed exertion
of the irritative motions. And many fenfitive mo-
tions are produced in confequence of this increafed
fenfation.

3. The afibciated trains and tribes of motions, ca-
tenated with the increafed irritative and fenfitive mo-
tions, aredifturbed, and proceed in confufion.

4. The faculty of volition is gradually impaired,
•whence proceeds the inflability of locomotion, inac-
curacy of perception, and inconfiftency of ideas ;
and is at length totally fufpended, and a temporary
apoplexy fucceeds.

SECT.

. XXII. i. REPETITION AN-D IMITATION.

SECT. XXII.

OF PROPENSITY TO MOTION, REPETITION AND
IMITATION.

I. Accumulation of fen formal power in hemiplagia, in
JliCj.. i'i (old fi; cj fever, in the locomotive mufcles,
in the organs oj Jenfe. Produces propenfity to action.
II. Repetition by three fenforial powers. In rhimes
and alliterations, in mufic, dancing, architecture,
land f cape -paint ing ^ beauty. III. i. Perception con-
fifts in imitation. Four kinds of imitation. 2. Vo-
luntary. Dogs taught to dance. 3. Senfitivc. Hence
fympathy and all our virtues* Contagious matter of
•venereal ulcers, of hydr ophobia, of jail-fever , of fmall-
pox, produced by imitation, and the fex of the em-
bryon. 4. Irritative imitation. 5. Imitations re-
folvable into ajfociations.

I. i. IN the henipiagia, when the limbs on one
fide have loft their power of voluntary motion, the
parent is for many days perpetually employed in
moving thole of the other. 2. When the volun-
tary power is fufpended during fleep, there commen-
ces a ^eafeleis flow of fenfitive motions, or ideas of
imagination, which compofe our dreams, 3. When
in the cold fit of an intermittent fever fome parts of
the Jyflem have for a time continued torpid, and
have thus expended lefs than their ufual expenditure
of fenforial power ; a hot fit fucceeds, with violent
adion of thofe vefiels, which had previoufly been
quiefcent. All thefe are explained from an accumu-
lation of fenforial power during the inactivity of fome
part of the fyftem.

Befides the very great quantity of fenforial power
perpetually produced and expanded in moving the

arterial,

294. REPETITION AND IMITATION. SECT. XXII. j,

arterial, venous, and glandular fyftems, with the va*
rious organs of digeftion, as defcribed in Section
XXXII. 3. 2, there is alfo a conftant expenditure of
it by the action of our locomotive mufcles and or-
gans of fenfe. Thus the4 thickhefs of the optic
nerves, where they enter the eye, and the great ex-
panfion of the nerves of touch beneath the whole of
the cuticle, evince the great confumption of fenfo-
rial power by thefe fenfes. And our perpetual muf-
cular actions in the common offices of life, and in
conftantly preferving the perpendicularity of our
bodies during the day, evince a confiderable expen-
diture of the fpirit of animation by our locomotive
mufcles. It follows, if the exertion of thefe or-
gans of fenfe and mufcles be for a while intermit-
ted, that fome portion of fenforial power mufl be
accumulated, and a propenfity to activity of fome
kind enfue from the increafed excitability of the
fyftem. Whence proceeds the irkfomenefs of a
continued attitude, and of an indolent life.

However fmall this hourly accumulation of the
fpirit of animation may be, it produces a propenfity
to fome kind of action ; but it neverthelefs requires
either defire or averfion, either pleafure or pain, or
fome external ftimulus, or a previous link of aflb-
ciation, to excite the fyftem into adivity ; thus it
frequently happens, when the mind and body are fp
unemployed as not tp poflefs any of the three firft
kinds of ftimulj, that the laft takes place, and con-
fumes the fmall but perpetual accumulatipn of fen-
forial power. Whence fome indolent people repeat
the fame verfe for hours together, or hum the iamq
tune. Thus the poet:

Onward he trudged, not knowing what he fought,
And whittled as he went, for want of thought.

II. The

Sect. XXI. 2. REPETITION AND IMITATION. 29-

II. The repetitions of motions may be at firft
produced either by volition, or by fenfation, or by
irritation, but they foon become eafier to perform
than any other kinds of action, becaufe they foon
become afibciated together, according to Law the
feventh, Section IV. on Animal Caufation. And
becaufe their frequency of repetition, if as much
fenforial power be produced during every reitera-
tion as is expended, adds to the facility of th^ir pro-
duction.

If a (Umulus be repeated at uniform intervals of
time, as defcribed in Section XII. 3. 3. the action,
whether of our mufcles or organs of fenfe, is pro-
duced with ftill greater facility or energy ; becaufe
the fenforial power of aflbciation mentioned above,
is combined with the fenforial power of irritation ;
that is, in common language, the acquired habit af~
fifts the power of the ftimulus.

This not only obtains in the annual, lunar, and
diurnal catenations of animal motions, as explained
in Section XXXVI. which are thus performed with
great facility and energy; but in every lefs circle of
actions or ideas, as in the burthen of a fong, or the
reiterations of a dance. To the facility and diftinct-
nefs, with which we hear founds at repeated inter-
vals, we owe the pleafure, which we receive from,
mufical time, and from poetic time ; as defcribed
in Botanic Garden, P. 2. Interlude 3. And to this
the pleafure we receive from the rhimes and allite-
rations of modern verification ; the fource of which
without this key would be difficult to difcover.
And to this likewife fliould be afcribed the beauty of
the duplicature in the perfect tenfe of the Greek
verbs, and of fame Latin ones, as tango tetigi, mor-
deo momordi.

There is no vaiiety of notes referable to the
gamut in the beating of the drum, yet if it be per-
formed in mufical time, it is agreeable to our ears ;

and

296 REPETITION AND IMITATION! SECT. XXII. 2.

and therefore this pleafurable fenfation mu'ft be ow-
ing to the repetition of the divifioris of the founds at
terrain intervals of time, or mufical bars. Whe-
ther thefe times or bars are diftinguifhed by a paufe,
or by an emphafis or accent, certain it is, that this
diftindlion is perpetually repeated ; othervvife the ear
could not determine inftantly, whether the fuccef-
fions of found were in common or in triple time. In
common time there is a divifion between every two
crotchets, or other notes of equivalent time ; though
the bar in written mufic is put after every fourth
crotchet, or notes equivalent in time ; i'n triple time
the divifion or bar is after every three crotchets, or
notes equivalent ; fo that in common time the repe-
tition recurs more frequently than in triple time.,
The grave or heroic verfes of the Greek «nd Latin
'poets are written in common time ; the French he-
toic verfes, and Mr. Anftie's humorous verfes in his
Bath Guide, are Written in the fame time as the
Greek and Latin verfes, but are one bar fhortef.
The Englifh grave or heroic verfes are meafured by
triple time, as Mr. Pope's tranfiation of Homer.

But befides thefe little circles of mufical lime,
there are the greater returning periods, and the ftill
more diftant chorufes, which like the rhimes at the
ends of verfes, owe their beauty to repetition; that
is, to the facility and diftin&nefs with which we per-
ceive founds, which we expect to perceive, or have
perceived before; or in the language of this work,
to the greater eafe and energy with which our organ
is excited by the combined fenforial powers of aflb-
ciation and irritation, than by the latter fingly,

A certain uniformity or repetition of parts enters
the very compofition of harmony. Thus two o&aves
neare'l to each other in the fcale commence their
vibrations together after every fecond vibration of
the higher one. And where the firft, third, and
fifth compofe a chord, the vibrations concur or coin-
cide

$*cf. XXII 3. REPETITION AND IMITATION. 297

cide frequently, though lefs fo than in the two oc-
taves. It is probable that thefe chords bear fome
analogy to a mixture of three alternate colours in
the fun's fpectrum feparated by a prifm.

The pleafure we receive from a melodious fuccef-
iion of notes referable to the gamut is derived from
another fource, viz. to the pandiculation or counter-
action of antagonifl fibres. See Botanic Garden,
P. 2. Interlude 3, If to thefe be added our early
aflbciations of agreeable ideas with certain propor-
tions of found, I fuppofe, from thefe three fources
fprings all the delight of mufic, fo celebrated by
ancient authors, and fo cnthufiaftically cultivated at
prefent. See Se&. XVI. No. 10. on Inftinct.

This kind of pleafure arifing from repetition, that
is from the facility and diftinctnefs, with which we
perceive and underftand repeated fenfations, enters
into all the agreeable arts ; and when it is carried to:
excefs is termed formality. The art of dancing like
that of mufic depends for a great part of the plea-
fure, it affords, on repetition j architecture, efpe-
cially the Grecian, confifts of one part being a re-
petition of another ; and hence the beauty of the
pyramidal outline in landfcape-painting ; where one
fide of the picture may be faid in fome meafure to
balance the other. So univerfally does repetition
contribute to our pleafure in the fine arts, that beau-
ty itfelf has been defined by fome writers to confift
in a due combination of uniformity and variety.
See Sea. XVI. 6.

III. i. Man is termed by Ariilotle an imitative
animal \ this propenfity to imitation not only appears
in the actions of children, but in all the cuftoms and
fafhions of the world : many thoufands tread in
the beaten paths of others, for one who traverfes
regions of his own difcovery. The origin of this
propenfity of imitation has nor, that I recollect, been
deduced from any known principle ; when any ac-
tion

29S REPETITION AND IMITATION. SECT. XXfT. 3.

tion prefents itfelf to the view of a child, as of
whetting a knife, or threading a needle, the parts
of this action in refpect of time, motion, figure, are
imitated by a part of the retina of his eye ; to per-
form this action therefore with his hands is eafier
to him than to invent any new action, becaufe it
confifts in repeating with another fet of fibres, viz.
with the moving mufcles, what he had juft performed
by fome part of the retina ; juft as in dancing we
transfer the times of motion from the actions of the
auditory nerves to the mufcles of the limbs. Imi-
tation therefore confifts of repetition, which we have
fhewn above to be the eafieft kind of animal action,
and which we perpetually fall into, when we pofiefs
an accumulation of fenforial power, which is not
otherwife called into exertion.

It has been fhewn, that our ideas are configura-
tions of the organs of fenfe, produced originally in
confequence of the ftimulus of external bodies. And
that thefe ideas, or configurations of the organs of
fenfe, refemble in fome property a correfpondent
property of external matter; as the parts of the
ienies of fighi and of touch, which are excited into ac-
tion, refemble in figure the figure of the ftimulating
body ; and probably alfo the colour, and the quan-
tity of denfity, which they perceive. As explained
in Seel. XIV. 2." 2. Hence it appears, that our per-
ceptions themfelves are copies, that is, imitations
of fome properties of external matter; and the pro-
penfity to imitation is thus interwoven with our ex-
iftence, as it is produced by the ftimuli of external
bodies, and is afterwards repeated by our volitions
and fenfations, and thus conftitutes all the opera-
tions of our minds.

2. Imitations refolve themfelves into four kinds,
voluntary, fenfitive, irritative, and aflbciate. The vo-
luntary imitations are, when we imitate deliberately
the actions of others, either by mimicry, as in acting a

play,

. 3. REPETITION AMD IMITATION. 299

play, or in delineating a flower; or in the common
actions of our lives, as in our drefs, cookery, lan-
guage, manners, and even in our habits of think-
ing.

Not only the greateft part of mankind learn all the
common arts of life by imitating others, biit brute
animals feem capable of acquiring knowledge with
greater facility by imitating each other, than by any
methods by which we can teach them ; as dogs and
cats, when they are fick, learn of each other to eat
grafs ; and I fuppofe, that by making an artificial
dog perform certain tricks, as in dancing on his
hinder legs, a Irving dog might be eafily induced to
imitate them ; and that the readied way of inftruct-
ing dumb animals is by practifing them with others
of the fame fpecies, which have already learned the
artswewifhto teach them. The important ufe of
imitation in acquiring natural language is mentioned
in Sed. XVI. 7. and 8. on Inftinct.

3. The fenfitive imitations are the immediate con-
fequences of pleafure or pain, and thefe are often pro-
duced even contrary to the efforts of the will. Thus
many young men on feeing cruel furgical operations
become fick, and fome even feel pain in the parts of
their own bodies, which they fee tortured or wounded
in others ; that is, they in fome meafure imitate by the
exertions of their own fibres the violent actions,
which they witnefTed in thofe of others. In this cafe
a double imitation takes place, firft the obferver imi-
tates with the extremities of the optic nerve the
mangled limbs, which are prefent before his eyes ;
then by a fecond imitation he excites fo violent action
of the fibres of his own limbs as to produce pain in
thofe parts of his own body, which he faw wounded
in another. In thefe pains produced by imitation
the effect has fome fimilarity to the caufe, which dif-
tinguifhes them from thofe produced by allociation ;
as the pains of the teeth, called tooth-edge, which

VOL. I. X are

REPETITION AND IMITATION. SECT. XXH. 5.

are produced by afibciation with difagreeable founds,
as explained in Sect. XVI. 10.

The effect of this powerful agent, imitation, in
the moral world, is mentioned in Sect. XVI. 7. as it
is the foundation of all our intellectual fympathies
with the pains and pleafures of others, and is in
confequence the fotfrce of all our virtues. For in
what confifts our fympathy with the miferies, or
with the joys, of our fellow creatures, but in an in-
voluntary excitation of ideas in fome meafure fimi-
lar or imitative of thofe, which we believe to exift
in the minds of the peifons, whom we commiferate
or congratulate ?

There are certain concurrent or fucceflive actions
of fome of the glands, or other parts of the body,
which are pofleffed of fenfation, which become in-
telligible from this propenfity to imitation. Of
thefe are the production of matter by the mem-
branes of the fauces, or by the ikin, in confequence
erf the venereal difeafe previoufly affecting the parts of
generation. Since as no fever is excited, and as nei-
ther the blood of fuch patients, nor even the matter
from ulcers of the throat, or from cutaneous ulcers,
will by inoculation produce the venereal difeafe in
others, as obferved by Mr. Hunter, there is reafon
to conclude, that no contagious matter is conveyed
thither by the blood -veffels, but that a milder matter
is formed by the actions of the fine veffels in thofe
membranes imitating each other. See Sect. XXXIII.
a. 9. In this difeafe the actions of thefe veflels pro-
ducing ulcers on the throat and (kin are imperfect
imitations of thofe producing chancre, orgonorrhoea j
frnce the matter produced by them is not infectious,
while the imitative actions in the hydrophobia ap-
pear to be perfect refemblances, as they produce a
material equally infectious with the original one,
"which induced them,

The

3. REPETITION AND IMITATION. 301

The contagion from the bite of a mad dog dif-
fers from other contagious materials, from its being
communicable from other animals to mankind, and
from many animals to each other ; the phenomena
attending the hydrophobia are in fame degree expli-
cable on the foregoing theory. The infectious mat-
ter does not appear to enter the circulation, as it can-
not be traced along the courfe of the lymphatics from
the wound, nor is there any fwelling of the lympha-
tic glands, nor does any fever attend, as occurs in
the fmall-pox, and in many other contagious difeafes ;
yet by fome unknown procefs the difeafe is commu-
nicated from the wound to the throat, and that
many months after the injury, fo as to produce pain
and hydrophobia, with a fecretion of infectious fali-
va of the fame kind, as that of the mad dog, which
inflicted the wound.

This fubject is very intricate. — It would appear,
that by certain morbid actions of the falivary glands
of the mad dog, a peculiar kind of faliva is produced;
which beirig inftilled into a wound of another ani-
mal, ftimulates the cutaneous or mucous glands into
morbid actions, but which are ineffectual in refpect
to the production of a fimilar contagious material ;
but the falivary glands by irritative fympathy are
thrown into fimilar action, and produce an infectious
faliva fimilar to that inftilled into the wound.

Though in many contagious fevers a material
fimilar to that which produced the difeafe, is thus
generated by imitation ; yet there are other infectious
materials, which do not thus propagate themfelves,
but which feem to act like flow poiibns. Of this
kind was the contagious matter, which produced the
jail-fever at the afllzes at Oxford about a century
ago. Which, though fatal to many, was not com-
municated to their nurfes or attendants. In thefe
cafes, the imitations of the fine veflels as above def-
cribed, appear to be imperfect, and do not therefore

X 2 produce

302 REPETITION AND IMITATION. SECT. XXfl. 4.$.

produce a matter fimilar to that, which ftimulates
them ; in this circumftance refembling the venereal
matter in ulcers of the throat or fkin, according to
the curious difcovery of Mr. Hunter above related,
who found, by repeated inoculations, that it would
not infect. Hunter on Venereal Difeaie, Part vi.
eh. i.

Another example of morbid imitation is in the
prodtt&ion of a great quantity of contagious matter,
as in the inoculated fmall-pox, from a fmall quan-
tity of ft infer ted into the arm, and probably diffufed
in the blood* Thefe particles of contagious matter
flimulate the extremities of the fine arteries, of the
fkin, and caufe them to imitate fome properties of
thofe particles of contagious matter, fo as to produce
a thousandfold of a fimilar material. See Section
XXXIII. 2. 6. Other inftances are mentioned in
the Section on Generationy which mew the probabi-
lity that the extremities of the feminal glands may
imitate certain ideas of the rnindy or actions of the
organs of fenfe, and thus occafion the male or fe-
male fex of the embryon. See Sect. XXXIX. 6.

4. We come now to thofe imitations, which are
not attended with fenfation. Of thefe are all the ir-
ritative ideas already explained, as wheff the retina
of the eye imitates by its action or configuration the
tree or -the bjench, which I fliun in walking, pad
without attending to them. Other examples of thefe
irritative imitations are daily obfervable in common
life; thus one yawning perfon mall feta whole com-
pany a yawning ; and fome have acquired winking
of the eyes or impediments of fpeech by imitating
their companions without being confcious of it.

5. Befides the three fpecies of imitations above
defcribed there may be fome aflbciate motions, which
may imitate each other in the kind as well as in the
quantity of their action ; but it is difficult to diftin-

them from the alfoclatipas of motions treated

SECT. XXII. 5. REPETITION AND IMITATION. 303

of in Se&ion XXXV. Where the aftions of other
perfons are imitated, there can be no doubt, or where
\veimitateapreconceivedidea by exertion of our
locomotive mufcles, as in painting a dragon ; all
thefe imitations may aptly be referred to the fources
above defcribed of the propenfity to activity, and
the facility of repetition ; at the fame time I do not
affirm, that all thofe other apparent fenfitive and ir-
ritative imitations may not be refolvable into affo-
ciations of a peculiar kind, in which certain diftant
parts of fimilar irritability or fenfibility, and which
have habitually acted together, may affect each other
exactly with the fame kinds of motion ; as many
parts are known to fympathife in the quantity of their
motions. And that therefore they may be ultimately
refolvable into alfociadons of aftion, as defcribed in.
Sett, XXXV.

SECT,

'304 OF THE CIRCULATORY SYSTEM. SECT. XXIII. i.
SECT. XXIII.

OF THE CIRCULATORY SYSTEM.

I. The heart and arteries have no antagonift mufcles.
Veins abforbtbe blood, propel it forwards, and di/tcnd
the heart ; contraction of the htart diftends the ar-
teries. Vena port arum. II. Glands which take their
fluids from the blood. With long necks, with fljort
necks. II], Ahforbent fyjlem. IV. Heat given out
from glandular fecretions. Blood changes colour in
the lungs and in the glands and capillaries. V. Blood
is abforbed by veins, as chyle by lafteal veffels, otber-
ivife they could not join their ftreams. VI. Two kinds
offtimulus, agreeable and difagreeable. Glandular
appetency. Glands originally poffejjed fenfation.

I. WE now ftep forwards to itluftrate fome of the
phenomena of difeafes, and to trace out their mod
efficacious methods of cure ; and (hall commence
this fubjeft with a fhort defcription of the circulatory
fyftem.

As the nerves, whqfe extremities form our various
organs of fenfe and mufcles, are all joined, or com-
municate, by means of the brain, for the convenience
perhaps of the diftribution of a fubtile etherial fluid
for the purpofe of motion ; fo all thqfe veflels of the
body, which carry the grofler fluids for the purpofes
of nutrition, communicate with each other by the
heart.

The heart and arteries are hollow mufcles, and
are therefore indued with power of contraction ir^
confecjuence of ftimulus, like all other mufcular
fibres ; but, as they have no antagonift mufcles, thq
cavities of the veifels, which they form, would re-
main

SECT. XXIII. i. OF THE CIRCULATORY SYSTEM. 305

main for ever clofed, after they have contra&ed
themfelves, unlefs forne extraneous power be applied
to a^ain diftend them. This extraneous power in
refpect to the heart is the current of blood, which is
perpetually abforbed by the veins from the various
glands and capillaries, and pufhed into the heart by
a power probably very fimiiar to that, which raifes
the fap in vegetables in the fpring, which, accord-
ing to Dr. Hale's experiment on the ftump of a vine,
exerted a force equal to a column of water above
twenty feet high. This force of the current of
blood in the veins is partly produced by their abfor-
bent power, exerted at the beginning of every fine
ramification ; which may be conceived to be a mouth
abforbing blood, as the mouths of the la&eals and
lymphatics abforb chyle and lymph. And partly by
their intermitted compreflion by the pulfations of
their generally concomitant arteries ; by which the
blood is perpetually propelled towards the heart, as
the valves in many veins, and the abforbent mouths
in them all, will not fuffer it to return.

The blood, thus forcibly injected into the cham-
bers of the heart, diftends this combination of hol-
low mufcles ; till by the ftimulus of diflention they
contract: themfelves ; and, pufhing forwards the
blood into the arteries, exert fufficient force T.Q
overcome in lefs than a fecond of time the vis iner-
tise, and perhaps fome elafticity, of the very extenr
five ramifications of the two great fyflems of the
aortal and pulmonary arteries. The power neceflary
to do this in fo fhort a time muft be confiderable,
and has been varioufly eitimated by different phyfio-
logifls.

The mufcular coats of the arterial fyftem are then
brought into aclion by the ftimulus of diflention,
and propel the blood to the mouths, or through the

Convolution^

306 OF THE CIRCULATORY SYSTEM. SECT. XXIII. 2,

convolutions, which precede the fecretory apertures
of the various glands and capillaries.

In the veflels of the liver there is no intervention
of the heart; but the vena portarum, which does
the office of an artery, is diftended by the blood
poured into it from the mefenteric veins, and is by
this diftention ftimulated to contract itfelf, and propel
the blood to the mouths of the numerous glands,
which compofe that vifcus.

II. The glandular fyftem of veffels may be di-
\ided into thofe, which take fome fluid from the
circulation ; and thofe, which give fomething to it.
Thofe, which take their fluid from the circulation are
the various glands, by which the tears, bile, urine,
perfpiration, and many other fecretions are produ-
ced ; thefe glands probably confift of a mouth to
fele£i, a belly to digeft, and an excretory aperture
to emit their appropriated fluids \ the blood is con-
veyed by the power of the heart and arteries to the
irjouths of thefe. glands, it is there taken up by the
living power of the gland, and carried forwards to
it? belly, and excretory aperture, where a part is fe-
parated, and the remainder abforbed by the veins for
further purpofes.

Some of thefe glands are fqrnimed with long con-
voluted necks or tubes, as the feminal ones, which
are curioufly feen when injected with quickfilver.
Others feem to confift of fharter tubes, as that great
congeries of glands which conftitute the liver, and
thole of the kidneys Some have their excretory
apartures opening into refervoirs, as the urinary
and gall bladders. And others on the external body,
as thofe which fecrete the tears, and perfpirable
matter.

Another great fyftem of glands, which have very
fhor t necks, are the capillary veiTels ; by which the
mienfibie perfpiration is fecreted on the fkin; and

. . • . : * : 4 • , • ; ,• • , : ;,.*-• • »i i . .'

the

SECT. XXIII. 3- OF THE CIRCULATORY SYSTEM. 307

the mucus of various conf.ftencies, which lubricate;?
the interfaces of the cellular membrane, of the muf-
cular fibres, and of all the larger cavities of the
body. From the want of a long convolution of vef-
fels fome have doubted, whether thefe capillaries
fhould be confidered as glands, and have been led to
conclude, that the perfpirable matter rather exuded
than was fecreted. But the fluid of perfpiration is
not fimple water, though that part of it which ex-
hales into the air may be iuch ; for there is a part of
it, which in a (late of health is abforbed again ; but
which, when the abfarbents are difeafed, remains on
the furface of the ikin, in the form of fcurf, or in-
durated mucus. Another thing, which (hews their
fimilitude to other glands, is their fenfibility to cer-
tain affections of the mind ; as is leen in the deeper
colour of the fkin in the blufh of mame,,or the
greater palenefs of it from fear.

III. Another feries of glandular vefTels is called
the abforbent fyftem ; thefe open their mouths into
^11 the cavities, and upon all thofe furfaces of the
body, where the excretory apertures of the other
glands pour out their fluids. The mouths of the
abforbent fyftem drink up a part or the whole of
thefe fluids, and carry them forwards by their living
power to their refpe&ive glands, which are called
conglobate glands. There thefe fluids undergo
fome change, before they pafs on into the circula-
tion ; but if they are very acrid, the conglobate
gland fwells, and fometime fuppurates, as in inocu-
lation of the fmall-pox, in the plague/ and in vene-
real abforptions ; at other times the fluid may per-
haps continue there, till it. undergoes fome chemical
change, that renders it lefs noxious ; or, what is
more likely, till it is regurgitated by the retrograde
motion of the gland in fpontaneous fweats or diar-
rhoeas

308 OF THE CIRCULATORY SYSTEM. SECT. XXIII. 4.

rhceas, as difagreeing food is vomited from the do-
mach.

IV. As all the fluids, that pafs through thefe
glands, and capillary veflels, undergo a chemical
change, acquiring new combinations, the matter of
heat is at the fame time given out ; this is apparent,
fmce whatever increafes infenfible perfpiration, in-
creafes the heat of the ikin ; and when the adion of
thefe veflels is much increased but for a moment, as
in blufhing, a vivid heat on the (kin is the immediate
confequence. So when great bilious fecretions, or
thofe of any other gland, are produced, heat is
generated in the part in proportion to the quantity
of the fecretion.

The heat preduced on the fkin by blufhing may
be thought by fome too fudden to be pronounced a
chemical effect, as the fermentations or new com-
binations taking place in a fluid is in general a
flower procefs. Yet are there many chemical mix«
tures in which heat is given out as inftantaneoufly ;
as in folutions of metals in acids, or in mixtures of
eflential oils and acids, as of oil of cloves and acid
of nitre. So the bruifed parts of an unripe apple
become almofl inflantaneoufly fweet ; and if the
chemico-animal procefs of digeftion be flopped for
but a moment, as by fear, or even by voluntary
erudation, a great quantity of air is generated, by the
fermentation which inflantly fucceeds the flop of
digeftion. By the experiments of Dr. Hales it appears,
that an apple during fermentation gave up above fix
hundred times its bulk of air ; and the materials in
the flomach are fuch, and infuch actuation, as im-
mediately to run into fermentation, when digeflion
is impeded.

As the blood paffes through the fmall veflels of the
lungs, which connect the pulmonary artery and
vein, it undergoes a change of colour from a dark to

a light

SECT. XXIII. 5. OF THE CIRCULATORY SYSTEM. 309

a light red : which may be termed a chemical
change, as it is known to be effected by an admix-
ture of oxygene, or vital air ; which, according to
a difcoyery of Dr. Prieftley, pafles through the moid
membranes, which conftitute the fides of thefe vef-
fels. As the blocd pafles through the capillary vef-
fels, and glands, which conned the aorta and its va^
rious branches with their correfpondent veins in the
extremities of the body, it again lofes the bright
red colour, and undergoes fome new combinations
jn the glands or capillaries, in which the matter of
heat is given out from the fecreted fluids. This pro-
cefs therefore, as well as the procefs of refpiration,
has fome analogy to combuflion, as the vital air or
oxygene feems to become united to fome inflamma-
ble bafe, and the matter of heat efcapes from the
new acid, which is thus produced.

V. After the blood has pafled thefe glands and
capillaries and parted with whatever they chofe to
take from it, the remainder is receive \ by the veins,
which are a fet of blood-abforbing veflels in general
correfponding with the ramifications of the arterial
fyflem. At the extremity of the fine convolutions
of the glands the arterial force ceafes ; this in ref-
peft to the capillary veflels, which unite the extre-
mities of the arteries with the commencement of the
veins, is evident to the eye, on viewing the tail of a
tadpole by means of a folar, or even by a common
microfcope, for globules of blood are feen to endea-
vour to pafs, and to return again and again, before
they become abforbed by the mouths of the veins ;
which returning of thefe globules evinces, that the
arterial force behind them has ceafed. The veins are
furnifhed with valves like the lymphatic abforbents;
and the great trunks of the veins, and of the la&eals
and lymphatics, join together before the ingrefs of
their fluids into the left chamber of the heart ; both

which

OF THE CIRCULATORY SYSTEM. SECT. XXIH. 6.

which evince that the blood in the veins, and the
lymph and chyle in the lacteals and lymphatics, are
carried on by a fimilar force; otherwife the ftream,
which was propelled with a lefs power, could not
enter the veflels, which contained the ftream pro-
pelled with a greater power. From whence it ap-
pears, that the veins are a fyftem of veflels abforbing
blood, as the lacteals and lymphatics are a fyftem
of veflels abforbing chyle and lymph. See Section
XXVI. i.

VI. The movements of their adapted fluids in the
various veflels of the body are carried forwards by
the actions of thofe veflels in confequence of two
kinds of ftimulus, one of which may be compared to
a pleafurable fenfationor defire inducing the veflel to
feize, and, as it were, to fwallow the particles thus
felected from the blood ; as is done by the mouths of
the various glands, veins, and other abforbents,
which may be called glandular appetency. The
other kind of flimulus may be compared to difa-
greeable fenfation or averfion, as when the heart has
received the blood, and is ftimulated by it to pufh it
forwards into the arteries ; the fame again ftimulates
the arteries to contract, and carry forwards the blood
to their extremities, the glands and capillaries. Thus
the mefenteric veins abforb the blood from the intef-
tines by glandular appetency, and carry it forward
to the vena portarum ; which acting as an artery
contracts itfelf by difagreeable flimulus, and pufhes
it to its ramified extremities, the various glands,
which conftitute the liver.

It ieems probable, that at the beginning of the
formation of thefe veflels in the embryon, an agree-
able fenfation was in reality felt by the glands during
fecretion, as is now felt in the act of fwallowing pa-
latable food ; and that a difagreeable fenfation was
originally felt by the heart from the diftention occa-

fioned

SECT. XXIII. 6. OF THE CIRCULATORY SYSTEM. 31 i

fionedby the blood, or by its chemical flimulus; but
that by habit thefe are all become irritative motions ;
that is, fuch motions as do not affecl: the whole fyf-
tem, except when the veffcls are difeafed by inflam-
mation.

SECT.

OF THE SALIVA AND TEARS. SECT. XXiV. t»

SECT. XXIV.

OF TrfE SECRETIONS OF SALIVA, AND OF TEARS,
AND OF THE LACRYMAL SACK.

I. Secretion of fdl'rva increafed by mercury in the
blood* i. By the food in the mouth. Drynefs of the
mouth not from a deficiency of /diva. 2 By fenfiti've
ideas. 3. By volition. 4. By di ft aft ef ul fiib fiances*
It is fe crete d In a dilute and f aline ft ate. It then be-
comes more vifcid. c. By ideas of d$afteful fub-
ftances. 6. By naufea. 7. By aver/ton. 8. By
catenation with Stimulating fubftances in the ear.
IL i. Secretion of tears lefs injleep. From ftimula-
iion of their excretory duel:. 2. Lacrymal fack is a
gland. 3. Its ufes. 4. fears arefecreted when the
nafal dud is ftimulated. 5. Or when it is excited
by fenfation. 6. Or by volition, j. T/JC lacrymal
fack can regurgitate its contents into the eye* 8. More
tears are fecreted by ajjociation with the irritation of
the nafal duel f the la:rymal fuck, than the puncla
lacrymalia can imbibe. Of the gout in the liver and
Jiomach.

I. THE falival glands drink up a certain fluid
from the circumfluent blood, and pour it into the
mouth. rl hey are fometimes ftimulated into a&ion.
by the blood, that furrounds their origin, or by fome
part of that heterogeneous fluid : for when mercurial
falts, or oxydes, are mixed with the blood, they fti-
mulate thefe glands into unnatural exertions; and
then an unufual quantity of faliva is feparated.

As the faliva fecreted by thefe glands is mod
wanted during the maftication of our food, it hap-
pens, when the terminations of their du6ts in the
mouth are ftimulated into adion, the falival glands

themfelves

SECT. XXIV. 2. 3-4- OF THE SALIVA AND TEARS. 31 j

themfelves are brought into increafed aftion at the
fame time by afibciation, and feparate a greater
quantity of their juices from the blood ; in the fame
manner as tears are produced in greater abundance
during the ftimulus of the vapour of onions, or of
any other acrid material in the eye.

The faliva is thus naturally poured into the mouth
only during the ftimulus of our food in maftication ;
for when there is too great an exhalation of the mu-
cilaginous fecretion from the membranes, which
line the mouth, or too great an abforption of it, the
mouth becomes dry, though there is no deficiency in
the quantity of faliva ; as in thofe who fleep with
their mouths open, and in fome fevers.

2. Though during the maftication of our natural
food thefalival glands are excited into aclion by the
ftimulus on their excretory duds, and a due quantity
of faliva is feparated from the blood, and poured
into the mouth; yet as this maftication of our food
is always attended with a degree of pleafure ; and
that pleafurable fenfation is alfo connected with our
ideas of certain kinds of aliment : it follows, that
when thefe ideas are reproduced, the pleafurable fen-
fation arifes along with them, and the falival glands
are excited into action, and fill the mouth with faliva
from this fenfitive alTociation, as is frequently feen in
dogs, who Haver at the fight of food.

3. We have alfo a voluntary power over the ac-
tion of thefe falival glands, for we can at any time
produce a flow of faliva into our mouth, and fpit out,
or fwallow it at will.

4. If any very acrid material be held in the mouth,
as the root of pyrethrum, or the leaves of tobacco,
the falival glands areftimulated into ftronger action
than is natural, and thence fecrete a much larger
quantity of faliva ; which is at the fame time more
vifcid than in its natural ftate ; becaufe the lympha-
tics, that open their mouths into the duels of the

falival

OF THE SALIVA AND TEARS. SECT. XXIV. 5. &

falival glands, and on the membranes, which line
the mouth, are likewife ftimulated into ftronger
action, and abforb the mofe liquid parts of the faliva
with greater avidity ; and the remainder is left both
in greater quantity and more vifcid.

The increafed abforption in the mouth by fome
flimulatin^ fubflar ces, which are called aftringents,
as crab jiiice, is evident from the inftant drynefs
produced in the mouth by a fmaii quantity of
them,

As the extremities of the glands are of exquifite
tenuity, as appears by their difficulty of injection, it
was neceffary for them to fecfete their fluids in a very
dilute Rate ; and probably for the purpofe of fiimu-
lating them into action, a quantity of neutral fait is
likevvife fecreted or formed by the gland. This
aqueous and ialine part of all fecreted fluids is again
reabfcrbed into the habit. More than half of fome
fecreted fluids is thus imbibed from the refervoirs,
into which they are poured ; as in the urinary blad-
der much more than half of what is fecreted by the
kidneys becomes reabforbed by the lymphatics, which
are thickly difperfed around the neck of theb adder*
This feems to be the purpofe of the urinary bladders
of tifh, as otherwife fuch a receptacle for the urine
could have been of no ufe to an animal immerfed in
water.

5. The idea of fubflances difagreeably acrid will
alfo produce a quantity of faliva in the mouth ; as
when we fmell very putrid vapours, we are induced
to fpit out our faliva, as if fomething dilagreeable
was actually upon our palates.

6, When difagreeable food in the ftomach produ-
ces naufea, a flow of faliva is excited in the mouth
by aflbciation ; as efforts to vomit are frequently
produced by difagreeable drugs in the mouth by the

7. A

Sfecr. XXiV. 2. OF THE SALIVA AND TEARS. 315

7. A preternatural flow of faliva is likevvife foiae-
times occaiioncd by a difeafe of the voluntary power ;
for if xve think about our faliva> and determine not
to (wallow it, or not to fpit it out, an exertion is
produced by the will, and more faliva is fecreted
againft our wifll ; that is, by our averfion, which
bears the fame analogy to defire, as pain does to4
pleafure ; as they are only modifications of the fame
difpofitioh of the fenforium. See Clafs IV. 3. 2. i.

8. The quantity of faliva may alfo be increafed
beyond what is natural, by the catenation of the
motions of thefe glands with other motions, or feii-
fations, as by an extraneous body in the ear; of
which I have known an inflance; or by the applica-
tion of ftizolobium, filiqua hirfuta, cowhage, to the
feat of the parotis, as fome writers have affirmed.

II. t. The lacrymal gland drinks up a certain,
fluid from the circumfluent blood, and pours it oh
the ball of the eye, on the upper part of the exter-
nal cornet of the eyelids. Though it may perhaps
be flimulated into the performance of its natural
udlion by the blood, -which furrounds its origin, or
by fome part of that heterogeneous fluid ; yet as the
tears fecreted by this gland are more wanted at fome
times than at others, its fecretion is variable, like that
of the faliva above mentioned, and is chiefly produced
when its excretory duel: is flimulated ; for in our
common fleep there feems to be little or no fecretion
of tears ; though they are occafionally produced by
our fenfations in dreams.

Thus when any extraneous material on the eye-
ball, or the drynefs of the external covering of it,
or the coldnefs of the air, or the acrimony of fome
vapours, as of onions, Simulates the excretory duel:
of the lacrymal gland, it difcharges its contents upon
the ball ; a quicker fecretion takes place in the gland,
and abundant tears fucceed, to moiiten, clean, and
lubricate the eye, Thefe by frequent nictitation are

VOL. I. Y diffufed

316 OF THE SAL1V4 AND TEARS SECT. XXfV. 2. 5. 4,

difFufed over the whole ball, and as the external an-
gle of the eye in winking is doled iboner than the
internal angle, the tears are gradually driven foi-
wards, and downwards from the lacrymal gland to
the puncta lacrymalia.

2. The lacrymal fack, with its puncta lacrymalia,
and its nafal duel, is a complete gland ; and is fm-
gular in this refpect, that it neither derives its fluid
from, nor difgorges it into the circulation. The
fimplicity of the ftructure of this gland, and both
the extremities of it being on the furfaceof the body,
makes it well worthy our minuter obfervation ; as
the actions of more intricate and concealed glands
may be better underftood from their analogy to this,

3. This fimple gland confifts of two abforbing
mouths^ a belly, and an excretory duel. As the
tears are brought to the internal angle of the eyev
thefe two mouths drink them up, being ftimula-ted
into action by this fluid, which they abforb. The
belly of the gland, or lacrymal fack, is thus filled, in
which the faline part of the tears is abforbed, and
when the other end of the gland, or nafal duel, is
ftimulated by the drynefs, or pained by the coldnek
of the air, or affected by any acrimonious duft o?
vapour in the noftriis, it is excited into action toge-
ther with the fack, and the tears are difgorged upon
the membrane, which lines the noftriis ; where they
ferve a fecond purpofe to moiften, clean, and lubri-
cate the organ of fmeil.

4. Whea- the nafal duet of this gland-is ftimulated
by any Very acrid material, as the powder of tobac-
co, or volatile fpirits, it not only difgorges the con-
tents of its belly or receptacle (the lacrymal fack;,
and abforbs haftily all the fluid, that is ready for it
in the corner of the eye ; but by the aifociation of its
motions with thofe of the lacrymal gland, it excites
that alfo into increafed action,- and a large flow of
tears is poured into the eye*

5. Thir

T.XXiV. 5.6.7.8. OF THE SALIVA AND TEARS. 317

5. This nafal duct is likewife excited into ftrong
aelion by fenfitive ideas, as in grief, or joy, and then
ulfo by its afibciations with the lacrymal gland it
produces a great flow of tears without any external
ilimulus ; as is more fully explained in Seel:. XVI. 8.
on Inftindt.

6. There are fome, famous in the arts of exciting
companion, who are faid to have acquired a volun-
tary power of producing a flow of tears in the eye;
which, from what has been faid in the fection on
Inftincl: above mentioned, I fhould fufpect, is per-
formed by acquiring a voluntary power over the
aclion of this nafal duel.

7. There is another circumftance well worthy our
attention, that when by any accident this nafal duel:
is obftructed, the lacrymal fack, which is the belly
or receptacle of this gland, by flight preflure of the
finger is enabled to difgorge its contents again into
the eye ; perhaps the bile in the fame manner, when
the biliary duels are obtfru&ed, is returned into the
blood by the veffels which fecrete it ?

8. A very important though minute occurrence
muft here be obferved, that though the lacrymal
gland is only excited into aclion, when we weep at
a diftrefsful tale, by its aiTociation with this nafal
duel, as is more fully explained in Seel. XVI. 8 ;
yet the quantity of tears fecreted at once is more
than the puncta lacrymalia can readily abforb ; which
{hews that the motions occasioned by ajjociatiom are fre-
quently more energetic than the original motions, by which
they were occasioned. Which we (hall have occafion
to mention hereafter, to illuftrate, why pains fre-
quently exift in a part diflant from trre caufe of
them, as in the other end of the urethra, when a ftone
Simulates the neck of the bladder. And why in-
flammations frequently arile in parts diftant from their
caufe, as the gutta rolea of drinking people, from an
inflamed liver.

Ys The

318 OF THE SALIVA AND TEARS. SECT.

The inflammation of a part is generally preceded
by a torpor or quiefcence of it; if this exifts in any
large congeries of glands, as in the liver, or any
membranous paTt, as the ftomach, pain is produced
and chiilinefs in confequence of the torpor of the
vefiels. In this fituation fometimes an inflammation
of the parts fucceeds the torpor ; at other times a
diftant more fenfible part becomes inflamed ; whofe
actions have previoufly been affociated with it ; and
the torpor of the firft part ceafes. This I apprehend
happens, when the gout of the foot fucceeds a pain
©f the biliary duet, or of the ftomach. Laftly, it
fometimes happens, that the pain of torpor exifts
without any confequent inflammation of the affected
part, or of 'any diftant part aflbciated with it, as in
the membranes about the temple and eye-brows in
hemicrania, and in tfrofe pains, which occafion con-
vulfions ; if this happens to gouty people, when k
affects the liver, I fuppofe epileptic fits are produced ;
and, when it affects the ftomach, death is the COTJ-
fequence. In rhefe cafes the pulfe is weak, and the
extremities cold, and fuch medicines as ftimulate
the quiefcent parts into action, or which induce in'-
flammation in them, or in any diftant parr, which
is aflbciated with them, cures the prefent pain of
torpor, and faves the patient.

I have twice feen a gouty inflammation of the
liver, attended with jaundice ; the patients after a
few days were both of them affected with cold fits;
like ague-fits, and their feet became affected with
gout, and the inflammation of their livers cealed.
It is probable, that the uneafy fenfations about the
ftomach, and indigeftion which precedes gouty
paroxyfms, are generally owing to torpor or flight
inflammation of the liver, and biliary ducts ; but
where great pain with continued ficknefs, wirh
fssbls p«ulfe, and fearaticn of cold, affect rhe

ftomaeihi

SECT. XXIV. 8. OF THE SALIVA AND TEARS. 319

ftomach in patients debilitated by the gout, that it
is a torpor of the flomach itfelf, and deftroys the
patient from the great connexion of that vifcus with
the vital organs. See Sed, XXV. 17.

SEC 1\

320 STOMACH AND INTESTINES. S&ct. XX\r, i

%

SECT. XXV.

OF THE STOMACH AND INTESTINES.

f. Of ^wallowing our food. Ruminating animals. %.
Action of the Jiomaclf. 3. dttion of the inteftines.
Irritative motions cvnnecltd with tbefe. 4. Effttft
of repletion. '"$, Stronger aftion of the flomach and
inteftines from more fiimulating food. 6. Their action
inverted by ftill 'greater famuli. Or by difguftful
ideas. Or by volition.' 7. Other glands ftrengthen
or invert their motions by fympathy. '8. Vomiting
performed by intervals, g. Inversion of the cutane-
iotfs absorbents, i o. Increafed fecretion of bile and
pancreatic juice. 1 1 . Jnverfion of the lacJeals. 1 2.
And of the bile-duels. 13. Cafe of a cholera. 14.
Further account of the in'verfion of lacieals* 15. Iliac
pajjwns. Valve of the colon. 16. Cure of the iliac
pajfion. 17. Pain' of gall-flone diftinguifoed from
pain of tie ftomach. Gout of the Jlomach from torpor^
from inflammation. Intermitting pulfs owing to
indigejiion. To ovcrdofe of foxglove. Weak pulfe
from emetics. Death from a blow on the Jlomach.
From gout of the Jlomach.

i. THE throat, ftomach, and jnteflines, may be
confidered as one great gland ; which like the lacry-
rnal fack above mentioned, neither begins nor ends
in the circulation. 'Though the act of mafticating
our aliment belongs to the fenfitive clafs of motions,
jfor the pleafure of its tafte iniduces the mufcles of
the jaw into action ; yet the deglutition of it when
malticated is generally, if not always, 'an irritative
motion, occafioned by the application of the food
already mafticated to the origin of the pharynx ;
'

. XXV. 2. 3. STOMACH A*D INTESTINES, 3.21

in the fame manner as we often fwallow our fpit.tle
without attending to it.

The ruminating cbfs of animals have the power
to invert the motion of their gullet, and of their
fir (I ftomach, from the flimulus of this aliment,
when it is a little further prepared ; as is their daily
practice in chewing the cud ; and appears to the eye
of any one, who attends to them, whilft they are
employed in the fecond maftication of their food.

2. When our natural aliment arrives into the
ftomach, this organ is ftimulated into its proper
vermicular aftion ; which beginning at the upper
orifice of it, and terminating at the lower one,
gradually mixes together and pumes forwards the
digefting materials into the inteltine beneath it.

At the fame time the glands, that fupply the
gaftric juices, which ,are neceffary to promote the
chemical part of the procefs of digeftion, are ftimu-
lated to difcharge their contained fluids, and to
feparate a further fupply from the blood-veflels : and
the lacleals or lymphatics, which open their mouths
into the ftomach, are ftimulated into a&ion, and
take up fome part of the digefting materials.

3. The remainder of thefe digefting materials is
carried forvvards into the upper inteftines, and
ftimulates them into their periftaltic motion fimilar
to that of- the ftomach ; wljich continues gradually
to mix the changing materials, and pafs them along
through the valve of the colon to the excretory end
&f this great gland, the fphincter ani.

The digefting materials produce a flow of bile,
and of pancreatic juice, as they pafs along the duo-
denum, by ftimulating the excretory duels of the
liver and pancreas, which terminate in that inte-
ftine : and other branches of the abforbent or lym-
phatic fyftem, called lacleals, are excited to drink
up, as it pailes, thofe parts of the digefting mate-
rials.

322 STOMACH AND INTESTINES. SECT. XXV. 4. 5.

rials, that are proper for rheir purpofe, by its ftiniu-
lus on their mouths.

4. When the ftomach and inteftines are thus
filled with their proper food, not only the motions
of the gaftric glands, the pancreas, liver, and
lacteal veflels, are excited into a&ion ; but at the
fame time the whole tribe of irritative motions are
exerted with greater energy, a greater degree of
warmth, colour, plumpnefs, and moiflure, is given
to the ikin from the increafed action of thofe glands
called capillary veifels ; pleafurable fenfation is ex-
cited, the voluntary motions are lefs eafily exerted,
and at length fufpended ; and fleep fucceeds, un-
lefs it be prevented by the fHmulus of furrounding
objects, or by voluntary exertion, or by an acqui-
red habit, which was originally produced by one or
other of thefe circufnftances, as is explained in Seel.
XXI. on Drunkennefs.

At this time alfo, as the blood-veflels become re-
plete with chyle, more urine is feparated into the
bladder, and lefs of it is reabforbed ; more mucus
poured into the cellular membranes, and lefs of it
jeabforbed : the pulfe becomes fuller and fofter,
and in general quicker. The reafon why lefs urine
and cellular mucus is abforbed after a full meal
with fufficient drink is owing to the blood-veflels
being fuller : hence one means to promote abforp-
tion is to decreafe the refiftance by emptying the
yeffels by venefedion. From this decreafed abforp-
tion the urine becomes pale as well as copious, and
the. ikin appears plump as well as florid.

By daily repetition of thefe movements they all
become connected together, and make a diurnal
circle of irritative action, and if one of this chain
be difturbed, the whole is liable to be put into dif-
order. See Seft. XX. on Vertigo.

5. When the itomach and inteftines receive a
quantity of food, whofe ftimulus is greater than

ufual

SECT. XXV. 6. STOMACH AND INTESTINES. 323

ufual, all their motions, and thofe of the glands
and lymphatics, are itimu'ared into ftronger action
than ufual, and perform their offices with greater
vigour and in lefs time : Inch are the effects cf
certain quantities of fpice or oi vinous fpirit.

6. But if the quantity or duration of thefe (timuii
are Mill further increased, the ftomach and throat
are (iimulated into a motion, whole direction is
contrary to the natural one above defcribed ; and
they regurgitate the materials, which they contain,
iinltead of carrying them forwards. This retrograde
motion of the (tomach may be compared to the
firetchings of wearied limbs the contrary wav, and
is well elucidated by the following experiment.
Look earneftly for a minute or two on an area an
inch Iquare of pink (ilk, placed in a ilrong light,
the eye becomes fatigued, the colour becomes faint,
and at length vaniihes, for the fatigued eye can no
longer be itimulated into, direct motions ; then on
doling the eye a green fpeclrum will appear in it,
which is a colour directly contrary to pink, and
which will appear and difappear repeatedly, like the
efforts in vomiting. See Section XXIX i r.

Hence all thole drugs* which by their bitter or
aftringent (timulus increale the action of the
ftomach, as camomile and white vitriol, if their
quantity is increafed above a certain dole, become
emetics.

Thefe inverted motions of the ftomach and throat
are generally produced from the fiimulus of unna-
tural food, and are attended with the Jenfation of
naufea or ficknefs : but as this fenfation is again
connected with an idea of the diftafteful food,
which induced it ; fo an idea of nauleous food will
alfo fometimes excite the action of naufea ; and that
give rife by affociation to the inverfion of the moti-
ons of the itomach and throat. As fome, who
have had horfe-flefh or dogs-fielh given them for

beef

324 STOMACH AND INTESTINES. SECT. XXV. 7. 8.

beef or mutton, are faid to have vomited many
Jiours afterwards, when they have been told of the
impofition.

I have been told of a perfon, who had gained a
voluntary command over thefe inverted motions of
the ftomach and throat,' and fupported himfelf by
exhibiting this curiofity to the public. At thefe
exhibitions he fwallowed a pint of red rough goofe-
berries, and a pint of white fmooth ones, brought
them up in fmall parcels into his mouth, and re-
ftored them feparately to the fpectators, who called
for red or white as they pleafed, till the whole were
re-delivered.

7.' At the fame time that thefe motions of the
ftomach and throat are ftimulated into inversion,
fome of .the other irritative motions, that had ac-
quired more immediate connexions with the fto-
mach, as thofe of the gaftric glands, are excited
into ftronger action by this alTociation ; and fome
other of thefe motions, which are more eafily ex-
cited, as thofe of the gaftric lymphatics, are invert-
ed by their aflbciation with the retrograde motions
of the ftomach, and regurgitate their contents,
and thus a greater quantity of mucus, and of lymph,
or chyle, is poured into .the ftomach, and thrown
up along with its contents.

8. Thefe inversions of the motion of the ftomach
in vomiting are performed by intervals, for the
fame reafon that many other motions are recipro-
cally exerted and relaxed ; for during the time of
exertion the ftimulus, or fenfation, which caufed
this exertion, is not perceived : but begins to be
perceived again, as foon as the exertion ceafes,
and is fome time in again producing its effect. As
explained in Seel. XXXiV. on Volition, where it
is (hewn, that the contractions of the fibres, and
the fenfation of pain, which pccafioned that exer-
tion, cannot exift at the fame time. The exertion

ceafes

T.XXV.9. lo. ix. 12. STOMACH AND INTESTINES. 335

ceafes from another caufe alfo, which is the ex-
hauftion of the fenforial power of the part, and theft?
two caufes frequently operate together.

9. At the times of thefe inverted efforts of the
ftomach not only the lymphatics, which open their
mouths into the ftomach, but thofe of the fkin alfo,
are for a time inverted ; for fweats are fornetimes
pufhed put during the efforts of vomiting without
an increafe of heat.

10. But if by a greater ftimulus the motions of
the ftomach are inverted ftill more violently or
more permanently, the duodenum has its periftaltic
motions inverted at the fame time by their affocia-
t'ion with thofe of the ftomach ; and the bile and
pancreatic juice, which it contains, are by the in-
verted motions brought up into the ftomach, and
diicharged along with its contents; while a greater
quantity of bile and pancreatic juice is poured into
this inteftine; as the glands, that fecrete them, are
by the^r affociation with the motions of the inteftine
excited into ftronger action than ufual.

1 1 . The other inteftines are by affociation ex-
cited into more powerful action, while the lympha-
tics, that open their mouths into them, fuffer an
inverfion of their motions correfponding with the
lymphatics of the ftomach, and duodenum ; whicli
with a part of the abundant fecretion of bile is
carried downwards, and contributes both to ftimu-
late the bowels, and to increafe the quantity of the
evacuations. This inverfion of the motion of the
lymphatics appears from the quantity of chyle,
which comes away by (tools; which is otherwife
abforbed as foon as produced, and by the immenfe
quantity of thin fluid, which is evacuated along
with it.

12. But if the ftimulus, which inverts the fto-
mach, be ftill more powerful, or more permanent,
it fornetimes happens, that the motions of the biliary

glands,

3*6 STOMACH AND INTESTINES SECT. XXV. 13. 14.

glands, and of their excretory duels, are at the
fame time inverted, and regurgitate their contained
bile into the blood veflels, as appears by the yellow
colour of the fkin, and of the urine ; and it is
probable the pancreatic fecretion may fuffer an in-
yerfion at the fame time, though we have yet no
raark by which this can be afcertained.

13. Mr. eat two putrid pigeons out of a

cold pigeon-pye, and drank about a pint of beer
and ale along with them, and immediately rode
about five miles. He was then feized with vomit-
ing, which was after a few periods fucceeded by
purging ; thefe continued alternately for two hours ;
and the purging continued by intervals for fix or
eight hours longer. During this time he could not
force himfelf to drink more than one pint in the
whole ; this great 'inability to drink was owing to
the naufea, or inverted motions of the flomach,
which the voluntary exertion of fwallowing could
feldom and with difficulty overcome; yet he dif-
charged in the whole at leaft fix quarts ; whence
came this quantity of liquid? Firft, the contents of
die flomach were emitted, then of 'the duodenum,
gall-bladder, and pancreas, by vomiting. After
this the contents of the lower bowels, then the
chyle, that was in , the lacleal veflels, and in the
receptacle of chyle, was regurgitated into the intef-
tines by a retrograde motion of thefe veflels. And
afterwards the mucus depofited in the cellular mem-
brane, and on the furface of all the other mem-
branes, feems to have been abforbed ; and with the
fluid abforded from the air to have been carried up
their lefpe.ctive lymphatic branches by the increafed
energy of their natural motions, and down the
vifceral lymphatics, or lacleals, by the inverfion of
their motions*

14. It may be difficult to invent experiments to
demonstrate the truth of this inverfion of fome

branches

SECT. XXV. 15. STOMACH AND 1NESTINES. 327

branches of the abforbent fyftem, and increafect
abforption of others, but the analogy of thefe vef-
fels to the Intel; inal canal, and the fymptoms of
many difeafes, render this opinion more probable
than many other received opinions of the animal
ceconomy.

In the above inflance, after the yellow excrement
was voided, the fluid ceafed to have any fmell,
and appeared like curdled milk, and then a thinner
fluid, and fome mucus, were evacuated ; did not
thefe feera to partake of the chyle, of the mucous
fluid from all the cells of the body, and laflly, of
the atmofpheric moifture ? All thefe facts maybe
eafily obferved by any one, who takes a brifk
purge.

15. Where the (Hmulus on the ftomach, or on
fome other part of the inteftinal canal, is ftill more
permanent, not only the lacteal veflels, but the
whole canal itfelf, becomes inverted from its aflb-
ciations : this is the iliac paiTion, in which all tire
fluids mentioned above are thrown up by tire
mouth. At this time the valve in the colon, from
the inverted motions of that bowel, and the in-
verted action of this living valve, does not prevent
the regurgitation of its contents.

The ftructure of this valve may be reprefented
by a flexile leathern pipe (landing up from the bot-
tom of a veflel of water : its fides collapfe by the
preiTure of the ambient fluid, as a fmait part of that
fluid paries through it ; but if it has a living power,
and by its inverted action keeps itfelf open, it be-
comes like a rigid pipe, and will admit the whole
liquid to pafs. See Sect. XXIX. 2. 5.

In this cafe the patient is averfe to drink, from
the conftant inverfion of the motions of the fto-
mach, and yet many quarts are daily ejected from
f'-.e ftomach, which at length find! of excrement,

and

STOMACH AND INTESTINES. SECT. XXV. 15.

and at lafl feem to be only a thin mucilaginous or
aqueous liquor.

From whence is it poilible, that this great quan-
tity of fluid for many fucceflive days can be fupplied^
after the cells of the body have given up their
fluids, but from the atmofphere? When the cuta-
neous branch of abforbents ads with unnatural
ftrength, it is probable the inteftinal branch has its
motions inverted, and thus a fluid is fupplied with-
out entering the arterial fyfteffi. Could oiling or
painting the fkin give a check to this difeafe ?

So when the ftomach has its motions inverted?
the lymphatics of the .ftomach, which are mod
ftridly aflbciated with it, invert their motions at
the fame time. But the more diftant branches of
lymphatics, which are lefs ftrictly aflbciated with it,
a£t with ihcreafed energy ; a$ the cutaneous lym-
phatics in the cholera, or iliac paflion, above de-
fcribed. And other irritative motions become de-
creafed, as the pulfations of the arteries, from the
extra-derivation or exhauftion of the fenforial
power.

Sometimes when ftronger vomiting takes placed
the more- diftant branches of the lymphatic fyftem
invert their motions with thofe of the ftomach, and
loofe (tools are produced, and cold fweats.

S6 when the lacteals have their motions inverted;
is during the operation of ftfong purges, the
urinary and cutaneous abforbents have their mo-
tions increafed to fupply the want of fluid in the
blood, as in great thifft ; but after a meal with
fufficient potation the urine is pa:le, that is, the
arinary abforbents act weakly, no fupply of water
being wanted for the blood. And when the intefti-
nal abforbents acl: too violently, as when too great
quantities of fluid have been drank, the urinary
abibrbents invert their motions to carry off the

fuperfluity

Seer. XXV. 16. 17. STOMACH AND INTESTINES. 32?

fuperfluity, which is a new circumftance of aflbcia-
tion, and a temporary diabetes fupervenes.

1 6. I have had the oportunity of feeing four
patients in the iliac paflion, where the ejected ma-
terial fmelled and looked like excrement. Two of
thefe were fo exhaufted at the time I faw them,
that more blood could not be taken from them,
and as their pain had ceafed, and they continued
to vomit up every thing which they drank, I fuf-
pecled that a mortification of the bowel had already
taken place, and as they were both women advanced
in life, and a mortification is produced with lefs
preceding pain in old and weak people, thefe both
died. The other two, who were both young men,
had (till pain and flrength fufficient for further
venefection, and they neither of them had any
appearance of hernia, both recovered by repeated
bleeding, and a fcruple of calomel given to one,
and half a dram to the other, in very fmall pills :
the ufual means of clyfters, and purges joined with
opiates, had been in vain attempted. I have thought
an ounce or two of crude mercury in lefs violent
. difeafes of this kind has been of ufe, by contribu-
ting to reftore its natural motion to fome part of
the inteftinal canal, either by its weight or flimulus;
and that hence the whole tube recovered its ufual
aifociations of progreflive periftaltic motion I have
in three cafes feen crude mercury given in fmall
dofes, as one or two ounces twice a day, have great
effect in (topping pertinacious vomitings.

17. Befides the affections above defcribed, the
ftomach is liable, like many other membranes of
the body, to torpor without confequent inflamma-
tion : as happens to the membranes about the headj
in fome cafes of hemicrania, or in general head-
ach. This torpor of the itomach is attended with
indigeftion, and confequent flatulency, and with
pain, which is ufualiy called the cramp of the fto-

330 STOMACH AND INTESTINES. SECT. XXV. 17"

rnach, and is relievable by aromatics, eficntial oils,
alcohol, or opium.

The intruiion of a gall-done into the commort
bile-duel from the gall-bladder -is fometimes mif-
taken for a pain of the ftomach, as neither of them
are attended with fevef ; but in the palfage of a
gall-fione, the pain is confined to a lefs fpace,
-which is exactly where the common bile-duel enters
the .duodenum, as explained in Section XXX. 3.
Whereas in this gaftrodynia the pain is diffufed over
the whole ftomach ; and, like other difeafes from
torpor,' the pulfe is weaker, and the extremities
coktef, and the general debility greater, than in
the paffage of a gall ftone ; for-in the former the
debility is the confequence of the pain, in the
latter it is the caufe of it.

Though the firft fits of the gout, I believe, com-
mence with a torpor of the liver ; and the ball of
the toe becomes inflamed inftead of the mem-
branes of the liver in confequence of this torpor,
as a coryza or catarrh frequently fucceeds a long
cxpofure of the feet to cold, as in fnow, or on a
moid brick-floor; yet in old or exhaufteJ conftf-
tutions, which have been long habituated to its
attacks, it fometimes commences with a torpor of the
llomach, and is transferable to every membrance of
the body. When the gout begins with torpor of the
iiomach, a painful feniation of cold occurs, which the
patient compares to ice, with weak pulfe, cold extre-
mities, and ficknefs ; this in its flighter degree is re-
lievable by fpice, wine, or opium; in its greater
degree it is fucceeded by fudden death, which is
owing to the fytnpathy of the ftomach with the
heart, as explained below.

if the ftomach becomes inflamed in confequence
of this gouty torpor of it, or in confequence of its
fympathy with fome other part, the danger is lefs.
A ficknefs and vomiting continues many days, or

evea

if CT. XXV. 17. STOMACH AND INTESTINES. 331

even week?, the flomach rejecting every thing fli-
niulant, even opium or alcohol, together with
much vifcicl mucus ; till the inflammation at length
ceafes, as happens when other membranes, as thofe
of the joints, are the feat of gouty inflammation ;
as obferved in Sett. XXIV. 2. 8.

The fympathy or aflbciation of motions, between
thofe of the flomach and thofe of the heart, are
evinced in many difeafes. Firfl, many people are
occafionally affected with an intermiffion of their
pulfe for a few days, which then ceafes again. In
this cafe there is a (top of the motion of the heart,
and at the fame time a tendency to eructation from
the flomach. As foon as the patient feels a ten-
dency to the intermiffion of the motion of his heart,
if he voluntarily brings up wind from his flomach,
the flop of the heart does not occur. From hence
I conclude that the flop of digeflion is the primary
difeafe ; and that air is inflantly generated from the
aliment, which begins to ferment, if the digeflive
procefs is impeded for a moment, (fee Sect. XX1IL
4.) ; and that the flop of the heart is in confe-
quence of the aflbciation of the motions of thefe
vifcera, as explained in Sect. XXXV. i. 4. ; but if
the little air, which is inflantly generated during
the temporary rorpor of the flomach, be evacuated,
the digeflion recommences, and the temporary
torpor of the heart does not follow. One patient,
\vhom I lately faw, and who had been five or fix
days much troubled with this intermiffion of a pul-
fation of his heart, and who had hemicram*a with
fome fever, was immediately relieved from them all
by lofing ten ounces of blood, which had what is
termed an inflammatory crud on it.

Another inftance of this aflbciation between the
motions of the flomach and heart is evinced by the
exhibition of an over dofe of foxglove, which in-
duces an inceflant vomiting, which is attended with

VOL. I. Z very

STOMACH AND INTESTINES. SECT. XXV. 17.

very flow, and fometimes intermitting pulfe. —
Which continues in fpite of the exhibition of wine
and opium for two or three days. To the fame
afibciation muft be afcribed the weak pulfe, which
conftantly attends the exhibition of emetics during
their operation. And alfo the fudden deaths,
which have been occafioned in boxing by a blow
on the ftomach ; and laftly, the fudden death of
thofe, who have been long debilitated by the gout,
from the torpor of the ftomach. See Seel:, XXV,
i. 4*

SECT.

S*CT. XXVI. i. OF GLANDS AND MEMBRANES. 3^
SECT. XXVI.

OF THE CAPILLARY GLANDS AND MEMBRANES*

I. i . The capillary veflels are glands. 2. Their excre*
tory duels. Experiments on the mucus of the intef*
tines , abdomen , cellular membrane, and on the
humours of the eye. 3. Scurf on the head, cough,
catarrh, diarrhoea, gonorrhoea. 4. Rheitmatifm.
Gout. Leprofy. II. i. The moft minute membranes
are unorganized. 2. Larger membranes are com-
pofed of the duels of the capillaries, and the mouths
of the abf or bents. 3. Mucilaginous fluid is fecreted
on their furf aces. III. Three kinds of Rheumatifm.

1. i. THE capillary veflels are like all the other-
glands except the abforbent fyftem, inafmuch as
they receive blood from the arteries, feparate a fluid
from it, and return the remainder by the veins.

2. This feries of glands is of the moft extenfive
ufe, as their excretory duels open on the whole ex-
ternal fkin forming its perfpirative pores, and on the
internal furfaces of every cavity of the body. Their
fecretion on the Ikin is termed infenfibie perfpira-
tion, which in health is in part reabforbed by the
mouths of the lymphatics, and in part evaporated
in the air ; the fecretion on the membranes, which
line the larger cavities of the body, which have ex-
ternal openings, as the mouth and inteftinal canal,
is termed mucus, but is not however coagulable
by heat ; and the fecretion of the membranes of
thofe cavities of the body, which have no external
openings, is called lymph or water, as in the cavi-
ties of the cellular membrane, and of the abdo-
men ; this lymph however is coagulable by the heat
of boiling water. Some mucus nearly as vifcid as

Z 2 the

334 OF GLANDS AND MEMBRANES. SECT. XXV? s.

the white of egg, which was difcharged by ftool,
did not coagulate, though I evaporated it to one-
fourth of the quantity, nor did the aqueous and
vitreous humours of a fheep's eye coagulate by the
like experiment : but the ferofity from an anafar-
cous leg, and that from the abdomen of a dropfical
perfon, and the cryflalline humour of a fheep's eye,
coagulated in the fame heat.

3. When any of thefe capillary glands are Simu-
lated into greater irritative actions, than Is natural,
they fecrete a more copious material ; and as the
mouths of the abforberit fyftem, which open in
their vicinity, are at the fame time ftimulated into
greater aclion, the thinner and, more faline part of
the fecreted fluid is taken up again ; and the re-
mainder is not only more copious but alfo more
vifcid than natural. This is more or lefs trouble-
fome or noxious according to the importance of
the functions of the part affected : on the Ikin and
bronchia, where this fecretion ought naturally to
evaporate, it becomes fo vifcid as to adhere to the
membrane ; on the tongue it forms a pellicle*
which can with difficulty be feraped off; produces
the fcurf on the heads of many people j and the
mucus, which is fpit up by others in coughing.
OR the noftrils and fauces, when the fecretion of
thefe capillary glands is increafed, it is termed
fimple catarrh ; when in the inteftines, a mucous
diarrhoea -9 and in the urethra, or vagina, it has the
name of gonorrhoea, or fluor albus.

4. When thefe capillary glands become inflamed,
a (till more vifcid or even cretaceous humour is
produced upon the furfaces of the membranes,
which b the caufe or the effect of rheumatifm,
gout, leprofy, and of hard tumours of the legs,
which generally termed fcorbutic j all which will
¥e treated of hereafter.

II. i. The

SECT. XXVI. 2. OF GLANDS AND MEMBRANES. 335

II. r. The whole fur face of the body, with all
its cavities and contents, are covered with mem-
brane. It lines every vefiel, forms every cell, and
binds together all the mufcular and perhaps the
o(Teo.us fibres of the body ; and is itfelf therefore
probably a fimpler fubftance than thofe fibres. And
as the containing vefTels of the body from the
larged to the lead are thus lined and connected
with membranes, it follows that thefe membranes
themfelves confided of unorganized materials.

For however fmall we may conceive the diame-
ters of the minuted vefTels of the body, which
efcape our eyes and glafles, yet thefe vefleis mud
coniid of coats or fides, which are made up of an
unorganized material, and which are probably pro-
duced from a gluten, which hardens after its pro-
duction, like the filk or web of caterpillars and
fpiders. Of this ntaterial confid the membranes,
which line the fhells of eggs, and the (hell itfelf,
both which are unorganized, and, are formed from,
mucus, which hardens after it is formed, either by
the abforption of its more fluid part, or by its uni-
ting with forne part of the atmofphere. Such is
alfo the production of the fhelis of fnails, and of
ihell-nfh, and 1 fuppole of the enamel of the
teeth.

2. But though the membrane?, that compofe the
fides of the mod minute velTels, are in truth unor-
ganized materials, yet the larger membranes, which
are perceptible to the eye, feem to be compofed of
an intertexture of the mouths of the abforbent
fydem, and of the excretory du&s of the capilla-
ries, with their concomitant arteries, veins, ?Uld
nerves: and from this conftruction it is evident,
that thefe membranes mud poiTefs great irritability
to peculiar dimuli, though they are incapable of
any motions, that are vifible to the naked eye :
daily experience mews us, that in their infla-

$36 OF QLANDS AND MEMBRANES. SLCT. XXVI. 3.

jned ftate they have the greateft fenfibility to pain,
as in the pleurify and paronychia.

3. On all thefe membranes a mucilaginous or
aqueous fluid is fecreted, which moiftens and lubri-
cates their furfaces, as was explained in Section
XXIII. 2, Some have doubted, whether this mu-
cus is feparated from the blood by an appropriated
fet of glands, or exudes through the membranes,
or is an abrafion or deftruction of the furface of the
membrane itfelf, which is continually repaired on
the other fide of it, but the great -analogy between
the capillary veflels, and the other glands, counte-
nances the former opinion ; and evinces, that thefe
capillaries are the glands, that fecrete it ; to which
\ve mutt add, that the blood in patting thefe capil-
lary veflels undergoes a change in its colour from
florid to purple, and gives out a quantity of heat ;
from whence, as in other glands, we muft conclude
that fomething is fecreted 'from it.

III. The feat of rheumatiirn is in the membranes,
or upon them ; but there are three very diftinct dif-
eafes, which commonly are confounded under this
name. Firft, when a membrane becomes affected
with torpor, or inactivity of the veflels which com-
pofe it, pain and coldneis fucceed, as in J:he hemi-
crania, and oiher head-achs, which are generally
tefmed nervous rheumatifm ; they exift whether
the part be at reft or in motion, and are generally
attended with other marks of debility.

Another rheumatifm is faid to exift, when inflam-
mation and fweliing, as well as pain, affect fome of
the membranes of the joints, as of the ancles,
wrifts, knees, elbows, and fometimes of the ribs.
This is accompanie4 with fever, is analogous to
pleurify and other inflammations, and is termed the
pcute rheumatifm.

A third difeafe is called chronic rheumatifm,
is d$inguiJhed from that firft mentioned, as

JB

SECT. XXVI. 3 OF GLANDS AND MEMBRANES. 337

in this the pain only affects the patient during the
motion of the part, and from the fecond kind of
rheumatifm above defcribed, as it is not attended
with quick pulfe or inflammation. It is generally
believed to fucoeed the acute rheumatifm of the
fame p^rt, and that fome coagulable lymph, or cre-
taceous, or calculous material, has been left on the
membrane ; which gives pain, when the mufcles
move over it, as fome extraneous body would do,
which was too infoluble to be abforbed. Hence
there is an analogy between the chronic rheuma-
tifm and the difeafes which produce gravel or gout-
ftones ; and it may perhaps receive relief from the
fame remedies, fuch as aerated fal foda.

SECT.

333 OF HEMORRHAGES. S|CT. XXVII. t-

SECT. XXVII.

Of HAEMORRHAGES.

I. The 'veins are abforbent vejjeh. i. Hemorrhage*
from inflammation. Cafe of hemorrhage from the
kidney cured by cold bathing. Cafe of hemorrhage
from the nofe cured by cqld immerfion. II. Hemorr-
hage from venous paralyfis. Of Piles. Black Jlooh.
Petecbitf. 'Consumption. Scurvy of the lungs*
Blacknefs of the face and eyes in epileptic Jits. Cure
of hemorrhages from venous inability.

I. AS the imbibing mouths of the abforbent fyf-
tern already defcribed open on the furface, and into
the larger cavities of the body, fo there is another
fyftem of abforbent veflels, which are not common-
ly elteemed fuch, I mean the veins, which take up
the blood from the various glands and capillaries,
after their proper fluids or fecretions have been
feparated from it.

The veins referable the other abforbent vefTels ;
as the prcgreilion of their contents is carried on in
the fame manner in both, they alike abforb their
appropriated fluids, and have valves to prevent its
regurgitation by the accidents of mechanical vio-
lence. This appears firft, beccaufe there is no pul-
fation in the very beginnings of the veins, as is>feen
by microfcopes ; which muft happen, if the blood
"was carried into them by the actions of the arteries.
For though the concurrence of various venous
,C reams of blood from different diftances muft pre-
vent any pulfation in the larger branches, yet in the
very beginnings of ail thefe branches a pulfation

rhuft

SECT. XXVII. i. OF HAEMORRHAGES. 359

mud unavoidably exift, if the circulation in them
was owing to the intermitted force of the arteries.
Secondly, the venous abforpdon of blood from the
penis, and from the teats of female animals after
their erection, is ftill more fimilar to the lymphatic
abforption, as it is previoufly poured into cells,
where all arterial impulfe muft ceafe.

There is an experiment, which feems to evince
this venous abforption, which confifts in the exter-
nal application of a ftimulus to the lips, as of vine-
gar, by which they become inftantly pale, that is,
the bibulous mouths of the veins by this ftimulus
are excited to abforb the blood fader, than it can
be fupplied by the ufual arterial exertion. See
Sed. XXIII. 5.

There are two kinds of haemorrhages frequent in
difeafes, one is where the glandular or capillary
action is too powerfully exerted, and propels the
blood forwards more hafUly, than the veins can
abforb it; and the other is, where the abforbent
power of the veins is diminifhed, or a branch of
them is become totally paralytic.

The former of thefe cafes is known by the heat
of the part, and the general fever or inflammation
that accompanies the haemorrhage. An haemorr-
hage from the nofe or from the lungs is ibmetimes a
crilis of inflammatory difeales, as of the hepatitis
and gout, and generally ceafes fpontaneoufly, when
the veflels are confiderably emptied. Sometimes
the haemorrhage recurs by daily periods accompa-
nying the hot fits of fever, and ceafing in the cold
fits, or in the intermiffions ; this is to be cured by
removing the febrile paroxyfms, which will by
treated of in their place. Otherwife it is cured by
venefe&ion, by the internal or external preparations
of lead, or by the application of cold, with an ab-
ftemious diet, and diluting liquids, like other in-
flammations.

340 OF HEMORRHAGES. SECT. XXVII. i .

flammations. Which by inducing a quiefcence on
thofe glandular parts, that are affected, prevents a
greater quantity of blood from being protruded
forwards, than the veins are capable of abfprb-
ing.

Mr. B had an hemorrhage from his kid-
ney, and parted with not lefs than a pint of blood
a day (by conjecture) along with his urine for above
a fortnight : venefedtions, mucilages, balfams, pre-
parations of lead, the bark, alum, and dragon's
blood, opiates, with a large blifter on his loins,
•were Separately tried, in large dofes, to no pur-
pofe. He was then directed to bathe in a cold
fpring up to the middle of his body only, the
upper part being covered, and the haemorrhage
diminifhed at the firft, and ceafed at the fecond im-
merfion.

In this cafe the external capillaries were rendered
quiefcent by the coldnefs of the water, and thence a
lefs quantity of blood was circulated through them ;
and the internal capillaries, or other glands, became
quiefcent from their irritative aflbciations with the
external ones ; and the hemorrhage was (topped a
fufficient time for the ruptured veflels to contract
their apertures, or for the blood in thofe apertures
to coagulate.

Mrs. K had a continued haemorrhage from

her nofe for fome days ; the ruptured veflel was not
to be reached by plugs up the noftrils, and the fen-
fibility of her fauces was fuch that nothing could
be borne behind the uvula. After repeated vene-
feftion, and other common applications, (he was
directed Jo immerfe her whole head into a pail of
water, which was made colder by the addition of
feveral handfuls of fait, and the haemorrhage im-
mediately ceafed, and returned no more; but
her pulfe continued hard, and (he was neceffita-

SECT. XXVII. 2. OF HEMORRHAGES. 34,

ted to lofe blood from the arm on the fticceeding
day.

Query, might not the cold bath inftantly (lop
hemorrhages from the lungs in inflammatory cafes?
— for the fhortnefs of breath of thofe who go fud-
denly into cold water, is not owing to the accumu-
lation of blood in the lungs, but to the quiefcence
of the pulmonary capillaries from aflbciation, as
explained in Seclion XXXII. 3. 2.

II. The other kind of hemorrhage is known
from its being attended with a weak pulfe, and
other fymptoms of general debility, and very fre-
quently occurs in thofe, who have difeafed livers,
owing to intemperance in the ufe of fermented
liquors. Thefe conftitutions are (hewn to be lia-
ble to paralyfis of the lymphatic abforbents, pro-
ducing the various kinds of dropfies in Section
XXIX. 5. Now if any branch of the venous fyf-
tem lofes its power of abforption, the part fwells,
and at length burfts and difchargesr the blood,
which the capillaries or other glands circulate
through them.

It fometimes happens that the large external veins
ofvthe legs burfl, and effufe their blood; but this
occurs mod frequently in the veins of the inteftines,
as the vena portarum is liable to fuffer from a fchir-
rus of the liver oppofmg the progreffion of the
blood, which is abforbed from the inteftines.
Hence the piles are a fymptom of hepatic obftruc-
tion, and hence the copious difcharges downwards
or upwards of a black material, which has been
called melancholia, or black bile ; but is no other
than the blood, which is probably difcharged from
the veins of the inteftines.

J. F. Meckel, in his Experimenta de Finibus
Vaforum, publifhed at Berlin, 1772, mentions his
difcovery of a communication of a lymphatic veflel

-with

34* OF HAEMORRHAGES, SECT. XXV] 1. 2.

with the gaftric branch of the vena portarum. It
is pofiible, that when the motion of the lymphatic
becomes retrograde in fome difeafes, that blood
may obtain a pafTage into it, where it analtomofes
with the vein, and thus be poured into the in-
teftines. A difcharge of blood with the urine fome-
times attends diabetes, and may have its fource in
the fame manner.

Mr. A , who had been a hard drinker,

and had the gutta rofacea on his face and bread:,
after a ftroke of the palfy voided near a quart of a
black vifcid material by (tool : on diluting it with
water it did not become yellow, as it muft have
done if it had been infpiffated bile, but continued
black like the grounds of coffee.

But any other part of the venous fyftem may be-
come quiefcent or totally paralytic as well as the
veins of the inteftines : all which occur more fre-
quently in thofe who have difeafed livers, than in
any others. Hence troublefome bleedings of the
nofe, or from the lungs with a weak pulfe ; henee
haemorrhages from the kidneys, too great menftru-
ation ; and hence the oozing of blood from every
part of the body, and the petechias in thofe fevers,
which are termed putrid, and which is erroneouily
afcribed to the thinnefs of the blood : for the blood
In inflammatory difeafes is equally tiuid before it
coagulates in the cold air.

Is not that hereditary confumption, which occurs
chiefly in dark-eyed people about the age of twenty,
and commences with flight pulmonary haemorrhages
without fever, a difeafe of this kind ? — Thefe hse-
morrhages frequently begin during fleep, when the
irritability of the lungs is not fufficient in thefe
patients to carry on the circulation without the
ailillance of volition ; for in our waking hours, the
motions ot the lungs are in part voluntary, efpeci-

allv

. XXVII. 2. OF HEMORRHAGES. 345

ally if any difficulty of breathing renders the efforts
of volition neceiTary. See Clafs I. 2. i. 3. and
Clafs HI. 2. i. 12. Another fpecies of pulmonary
confumption which feems more certainly of fcro-
phulous origin is defcribed in the next Section,
No. 2.

I have feen two cafes of women, of about forty
years of age, both of whom were feized with quick
weak pulfe, with difficult refpiration, and who fpit
up by coughing much vifcid mucus mixed with dark
coloured blood. They had both large vibices on
their limbs, and petechias ; in one the feet were in
danger of mortification, in the other the legs were
cedematous. To relieve the difficult refpiration,
about fix ounces of blood were taken from one of
them, which to my furprife was fizy, like inflamed
blood : they had both palpitations or unequal pulfa-
tions of the heart. They continued four or five
weeks with pale and bloated countenances, and did
not ceafe fpitting phlegm mixed with black blood,
and the pulfe feldom flower than 1 30 or 135 in a
minute. This blood, from its dark colour, and
from the many vibices and petechise, feems to have
been venous blood ; the quieknefs of the pulfe, and
the irregularity of the motion of the heart, are to
be afcribed to debility of that part of the fyftem ;
as the extravafation of blood originated from the
defed of venous abforption. The approximation
of thefe two cafes to fea-fcurvy is peculiar, and
may allow them to be called fcorbutus pulmonalis.
Had thefe been younger fubjeds, and the paralyfis
of the veins had only affected the lungs, it is pro-
bable the difeafe would have been a pulmonary con-
fumption.

Lafl week I faw a gentleman of Birmingham,
who had for ten days laboured under great palpi-
tation of his heart, which was fo diftinctly felt by

the

$44 OF HAEMORRHAGE! SECT, xxvif. &

the hand* as to difcountenance the idea of there
being a fluid in the pericardium. He frequently
fpit up mucus ftained with dark coloured blood, his
pulfe very unequal and very weak, with cold hands
and nofe. He could not lie down at all, and for
about ten days paft could not fleep a minute toge-
ther, but waked perpetually with great uneafinefs0
Gould thofe fymptoms be owing to very extenfive
adhefioris of the lungs ? or is this a fcofbutus pul-
monalis ? After a few days he fuddenly got fo much
better as to be able to fleep many hours at a time
by the ufe of one grain of powder of foxglove
twice a day, and a grain of opium at night. .After
a few days longer, the bark was exhibited, and the
opium continued with fome wine ; and the palpi-
tations of his heart became much relieved, and he
recovered his ufual degree of health, but died fud-
denly fome months afterwards.

In epileptic fits the patients frequently become
black in the face, from the temporary paralyfis of
the venous fyftem of this part. I have known two
inftances where the blacknefs has continued many

days. Mr. P , who had drank intemperately?

was feized with the epilepfy when he was in his
fortieth year ; in one of thefe fits the white part of
bis eyes was left totally black with effufed blood -y
which was attended with no pain or heat, and was
in a few weeks gradually abforbed, changing colour
as is ufual with vibices from bruifes.

The haemorrhages produced from the inability of
the veins to abforb the refluent blood, is cured by
opium, the preparations of fteel, lead, the bark,
\-itriolic acid, arid blifters; but thefe have the effect
with much more certainty, if a venefe&ion to a few
ounces, and a moderate cathartic with four or fix
grains of calomel be premifed, where the patient

is

SECT. XXVIII. 2. PARALYSIS OF ABSORBENTS. 34$

is not already too much debilitated ; as one great
means of promoting the abforption of any fluid
confifts in previoufly emptying the veflels, which are
to receive it.

SECTJ

346 PARALYSIS OF ABSORBENTS. SECT. XXVIII. ;*
SECT. XXVIII.

OF THE PARALYSIS OF THE ABSORBENT SYSTEM.

I. Paralyfis of the latteals^ atrophy. DiJIafte to animal
food. II. Caufeofdropfy. Caufe of herpes. Scro-
phuia. Mefentetic confumption. Pulimnary con-
JumptioK* Why ulcers in the lungs are fo difficult to
heal.

THE term paralyfis has generally been ufed to
cxprefs the lofs of voluntary motion, as in the hemi-
plagia, but may with equal propriety be applied to
exprefs the difobediency of the mufcular fibres to
the other kinds of ilimulus ; as to thofe of irritation
or fenfation.

1. There is a fpecies of atrophy, which has not
been well underftood ; when the abforbent vefTels
of the ftomach and inteftines have been long inured
to the ftimulus of too much fpirituous liquor, they
at length, either by the too fudden omiflion of fer-
mented or fpirituous potation, or from the gradual
decay of nature, become in a certain degree para-
lytic ; now it is obfefved in the larger mufcles of
the body, when one fide is paralytic, the other is
more frequently in motion, owing to the lefs ex-
penditure of fenforial power in the paralytic limbs ;
fo in this cafe the other part of the abforbent fyflem
acls with greater force, or with greater perfeve-
rance, in confequence of the paralyfis of the lac-
fleais ^ and the body becomes greatly emaciated in
a fmall time.

I have feen feveral . patients in this difeafe, of
which the following are the circumflances. i . They
were men of about fifty years of age, and had
lived freely in refped to fermented liquors. 2. They

loft

feet. XXVIII. 2. PARALYSIS OF ABSORBENTS. 347

loft their appetite to animal food. 3. They became
fuddenly emaciated to a great degree. 4. Their
fkins were dry and rough. 5. They coughed and
expectorated with difficulty a vifcid phlegm. 6- The
membrane of the tongue was dry and red, and lia-
ble to become ulcerous.

The inability to digeft animal food, and the con-
fequent diftafte to it, generally precedes the dropfy,
and other difeafes, which originate from fpirituous
potation. I fuppofe when the ftomach becomes in-
irritable, that there is at the fame time a deficiency
of gaftric acid ; hence milk feldom agrees with thefe
patients, unlefs it be previoufly curdled, as they
have not fufficient gaftric acid to curdle it; and
hence vegetable food, which is itfelf acefcent, will
agree with their flomachs longer than animal food,
which requires more of the gaftric acid for its
digeftion.

In this difeafe the fkiii is dry from the increafed
abforption of the cutaneous lymphatics, the fat is.
abforbed from the increafed abforption of the cellu-
lar lymphatics, the mucus of the lungs is too vifcid
to be eafily fpit up by the increafed abforption. of
the thinner parts of it, the membrana fneideriana
becomes dry, covered with hardened mucus, and
at length becomes inflamed and full of apthas, and
either thefe floughs, or pulmonary ulcers, terminate
the fcene.

II. The immediate caufe of dropfy is the para-
lyfis of fome other branches of the abforbent fyftem,
which are called lymphatics, and which open into
the larger cavities of the body, or into the cells of
the cellular membrane ; whence thofe cavities or
cells become diftended with the fluid, which is
hourly fecreted into them for the purpofe of lubri-
cating their furfaces. As is more fully explained
in No. 5. of the next Section,

VOL. I. A a As

348 PARALYSIS OF ABSOREENTS. SECT. XXVIII. *•

As thofe lymphatic veffels confift generally of a
long neck or mouth, which drinks up its appropri-
ated fluid, and of a conglobate gland, in which this
fluid undergoes fome change, it happens, that feme-
times the mouth of the lymphatic, and fometimes
the belly or glandular part of it, becomes totally or
partially paralytic. In the former cafe, where the
mouths of the cutaneous lymphatics become torpid
or quiefcent, the fluid fecreted on the (kin ceafes to
be abforbed, and erodes the (kin by its faline acri-
mony, and produces eruptions termed herpes, the
difcharge from which is as fait, as the tears, which
are fecreted too faft to be reabforbed, as in grief,
or when the pun&a lacrymalia are obftrufted, and
which running down the cheek redden and inflame
the fkin.

When the mouths of the lymphatics, which open
on the mucous membrane of the noftrifs, become
torpid, as on walking into the air in a frofty morn-
ing; the mucus, which continues to be fecreted,
has not its aqueous and faline part reabforbed,
which running over the upper lip inflames it, and
has a fait tafte, if it falls on the tongue.

When the belly, or glandular part of thefe lym-
phatics, becomes torpid, the fluid abforbed by its
mouth ftagnates, and forms a tumour in the gland.
This difeafe is called the fcrophula. If thefe glands
fuppurate externally, they gradually heat, as tbofe
of the neck ; if they fuppurate without an opening
on the external habit, as the mefenteric glands, a
he&ic fever enfues, which deftroys the patient j if
they fuppurate in the lungs, a pulmonary confump-
tion enfues, which is believed thus to differ from
that deferibed in the preceding Section, in refpect
to its feat or proximate caufe.

It is remarkable, that matter produced by fup-
puration will 'He concealed in the body many weeks,
or even months, without producing hectic fever ;

but

SECT. XXVIII; 2. PARALYSIS OF ABSORBEN FS. 349

but as foon as the wound is opened, fo as to admit
air to the fur face of the ulcer, a he&ic fever fuper*
venes, even in very few hours, which is probably
owing to the azotic part of the atmofphere rather
than to the oxygene ; becaufe thofe medicines*
which contain much oxygene, as the calces or
bxydes of metals, externally applied, greatly con-
tribute to heal ulcers, of thefe are the folutions of
lead and mercury, and copper in acids, or their
precipitates.

Hence when wounds are to be healed by the firft
intention, as it is called^ it is neceffary carefully to
exclude the air from them. Hence we have one
caufe, which prevents pulmonary ulcers from heal-
ing, which is their being perpetually expofed to
the air.

Both the dark-eyed patients, which are affe&ed
with pulmonary ulcers from dificient venous abforp-
tion, as defcribed iri Section XXVII. 2. and the
light-eyed patients from deficient lymphatic abforp«
tion, which we are now treating of, have generally
large apertures of the iris ; thefe large pupils of
the eyes are a common mark of want of irritability;
and it generally happens, that an increafe of fenfi-
bility, that is, of motions in confequence of fenfa-
-tion, attends thefe conftitutions. See Seel. XXXI.
2. Whence inflammations may occur in thefe front
ftagnated fluids more frequently than in thofe con-
ftitutions, which poffsfs more irritability and lefs
fenfibility.

Great expectations in refpect to the cure of con-
fumptions, as well as of many other difeafes, are
produced by the very ingenious exertions of DR,
BEDDOES; who has eftablifhed an apparatus for
breathing various mixtures of airs or gaffes, at the
hot-wells near Briftol, which well deferves the at-
tention of the public.

A a 4

350 RETROGRADE ABSORBENTS. SECT, XXIX. i.

DR. BEDDOES very ingenioufly concludes, from
the florid colour of the blood of ccnfurnptive pati-
ents, that it abounds in oxygene ; and that the
rednefs of their tongues and lips, and the fine blufb
of their cheeks fliew the prefence of the fame prin-
ciple, like flefh reddened by nitre. And adds,
that the eircumftance of the confumptions of preg-
nant women being (lopped in their progrefs during
' pregnancy, at which time their blood may be fup-
pofed to be in part deprived of its oxygene, by
oxygenating the blood of the fcetus, is a forcible
argument in favour of this theory ; which muft
foon be confirmed or confuted by his experiments.
See EiTay on Scurvy, Confumption, &c. by Dr.
Beddoes. Murray. London. Alfo Letter to Dr,
Darwin, by the fame. Murray. London,

S E CT.

SECT. XXiX. i. RETROGRADE ABSORBENTS-

SECT. XXIX.

ON THE RETROGRADE MOTIONS OF THE ABSORBENT
SYSTEM.

I. Account of the abforbent fyftem. II. The ial<ves of
ihe abforbent veffels may fuffer their fluids to regurgi-
tate in fome difeafcs. 111. Communication from the
alimentary canal to, the bladder by mean* of the abfor-
bent veffels. IV. The phenomena of diabetes ex-
plained. V. i . The phenomena ofdropfies explained.
2. Cafes of the ufe of foxglove. VI. Of cold fweats.
VII Tranflations of matter, of chyle, of milk, of
mine, operation of purging drugs applied externally.
VIII. Circumftances by which the fluids, that are
effufed by the retrograde motions of the abforbent
ve/fels, are dijlinguijhed. IX. Retrograde mot ions of
vegetable juices. X Objections anfwered. XI. The
cafes, which induce the retrograde motions of animal
•uejfelsy and the medicines by which the natural moti-
ons are rejlored.

N. B. The following Scclion is a tranflation of apart of
a Latin thefis written by the late Mr. Charles Darwin,
which was printed 'with his prize dijfertation on a
criterion between matter and mucus in 1780. Sold
by Cadell, London.

I. Account of the Abforbent Syftem*

i. THE abforbent fyftem of veffels in animal
bodies confifts of feveral branches, differing in re-
fpecl to their fituaticms, and to the fluids, which
they abforb.

The inteftinal abforbents open their mouths on
the internal furfaces of the inteltines $ their office is

tQ

35* RETROGRADE ABSORBENTS. SECT. XXIX. j

to drink up the chyle and the other fluids from the
alimentary canal ; and they are termed lacleals, to.
diftinguilh them from the other abforberu veffels,
which have been termed lympatjcs.

Thofe whofe mouths are difperfed on the exter-
nal (kin, imbibe a great quantity of water from the
atmofphere, and a part pf the perfpirable matter,
which does not eyapqrate, and are termed cutane-
ous abforbents.

Thofe, which arife from the internal furface of
the bronchia, and which imbibe moifture from the
atmofphere, and a part of the bronchial mucus,
are called pulmonary abforbents.

Thofe, which opei} their innumerable mouths
into the cells of the whole cellular membrane ; and
whofe ufe is to take up the fluid, which is poured
into thofe cells, after it has done its office there ;
may be called cellular Abforbents.

Thofe, which arife from the internal furfaces of
the membranes, which line the larger cavities of
ttye body, as the thorax, abdomen, fcrqtum, peri-
cardium., take up the mucus poured into tfyofe car
vines ; and are diftingui(he4 by the names of their1
refpe&iye cavities.

Whilft thqfe, which arife from the internal fur-
faces of the urinary bladder, gall-bladder, falivary
due~ts, pr pther receptacles of fecreted fluids, may
take their names from thofe fluids ; the thinner parts
pf which it is their office to abibrb : as urinary,
bilious, or falivary abforbents.

2. Many of thefe abforbent veflels, both lac~teal§
and lymphatics, like fame of the veins, are replete
with valves: which feenr defigned to affift the pror
grefs of their fluids, or at leafl to prevent their re-
gurgitation ; where they are fubjecled to the inter-
mitted preflure of the mufcular, or arterial adtion§
in their neighbourhood.

Thef?

SECT. XXIX. 2. RETROGRADE ABSORBANTS. 353

Thefe valves do not however Appear to be necef-
fary to all the abforbents, any more than to all the
veins ; fmce they are not found to exiit in the ab-
forbent fyftem of fifh ; according to the difcoveri-es
of the ingenious, and much lamented Mr. Hewfon.
Philof. Tranf. v. 59, Enquiries into the Lymph.
Syft. p. 94.

3. Thefe abforbent veffels are alfo furnimed with
glands, which are called conglobate glands ; whofe
ufe is not at prefent fufficiently inveftigated ; but it
is probable that they refemble the conglomerate
glands both in ftru&ure and, in ufe, except that their
abforbent mouths are for the conveniency of fitua-
tion placed at a greater diftance from the body of
the gland. The conglomerate glands open their
mouths immediately into the fanguiferous veffels,
which bring the blood, from whence they abforb
their refpe&ive fluids, quite up to the gland : but
thefe conglobate glands collect their adapted fluids
from very diftant membranes, or cyfts,' by means
of mouths furnimed with long necks for this pur-
pofej and which are called lac!eals? or lympha-
tics.

4. The fluids, thus collected from various parts
of the body, pafs by means of the thoracic duft
into the left fubciavian near the jugular vein j ex-
cept indeed that thofe collected from the right fide
of the head and neck, and from the right arm, are
carried into the right fubclavian yein : and fome-
times even the lymphatics from the right fide of the
lungs are inferted into the right fubclavian vein ;
whilft thofe of the left fide of the head open but
juft into the fummit of the thoracic duel.

5. In the abforbent fyftem there are many anafto-
mofes of the vefifels, which feem of great confe-
quence to the prefervation of health. Thefe anafto-
mofes are discovered by diflection to be very fre-
quent between the inteflinal and urinary lympha-
tics

354 RETROGRADE ABSORBENTS. SECT. XXIX. a,

tics, as mentioned by Mr. Hewfon, (Phil. Tranf,
v. 58.)

6. Nor do all the inteftinal abforbents feem to
terminate in the thoracic ducr*, as appears from,
fome curious experiments of D. Munro, who gave
madder to fome ariirnals, having previoufly put a
ligature on the thoracic duel, and found their
bones, and the feruin of their blood, coloured red.
> , . i i ' ' •,.

II* The Valves of the Akforbent Syftem may fujfcr tbeir
Fluids to regurgitate in fome Difeafes.

i. THE many valves, which occur in the pro-
grefs of the lymphatic and lacteal veflels, would
feem infuperable o-bftacles to the regurgitation of
their contents. But as thefe valves are placed in
veflels, which are indued with life, and are them-
felves indued with life alfq ; and are very irritable
into thofe natural motions, which abforb, or propel
the fluids they contain ; it is poflible, in fame dif-
eafes, where thefe valves or veflels are ftimulated
into unnatural exertions, or are become paralytic,
that during the diaflole of the part of the yeflel to
which the valve is attached, the valve may not fo
completely clofe, as to prevent the relapfe of the
lymph or chyle. This is rendered more probable,
by the experiments of injecting mercury, or water,
pr fuet, or by blowing air down thefe veflels : all
which pafs the valves very eafily, contrary to the
natural courfe of their fluids, when the veflels are,
thus a little forcibly dilated, as mentioned by Dr.
Haller, Elem. Phyfiol. t. iii. f. 4.

" The valves of the thoracic duel: are few, fome
afTert they are not more than twelve, and that they
do not very accurately perform their office, as they
do not clofe the whole area of the duel, and thencq
may permit chyle to repafs them downwards. In
living animals, however, though not always, yet

morq

SECT. XXIX. i. RETROGRADE ABSORBENTS. 355

more frequently than in the dead, they prevent the
chyle from returning. The principal of thefe valves
is that, which prelides over the infertion of the
thoracic duel, into the fubclavian vein ; many have
believed this alfo to perform the office of a valve,
both to admit the chyle into the vein, and to pre-
clude the blood from entering the duel; but in my
opinion it is fcarcely fuffiqitnt for this purpofe."
Haller, Elem. Phyf. t. vii. p. 226-

2. The mouths of the lymphatics feem to admit
water to pals through them after death, the invert-
ed way, eafier than the natural one ; fmce an in-
verted bladder readily lets out the water with which
it is filled; whence it may be inferred, that there is
no obftacle at the mouths of thefe veflels to prevent
the regurgitation of their contained fluids.

I was induced to repeat this experiment, and
having accurately tied the ureters and neck of a
frefii ox's bladder, I made an opening at the fundus
of it ; and then, having turned it infide outwards,
filled it half full with water, and was furprifed to
fee it empty itfelf fo haftily. I thought the experi-
ment more appofite to my purpofe by fufpending the
bladder with its neck downwards, as the lymphatics
are chiefly fpread upon this part of it, as fhewn by
Dr. Watibn, Philof. Tranf. v. 59. p. 392.

3. In fome difeafes, as in the diabetes and fcro-
phula, it is probable the valves themfelves are dif-
eaied, and are thence incapable of preventing the
return of the fluids they mould fupport. Thus the
valves of the aorta itfelf have frequently been
found fchirrous, according to the difle&ions of
Monf. Lieutaud, and have given rife to an inter-
rupted pulfe, and laborious palpitations, by fuffer-
ing a return of part of the blood into the heart.
Nor are any parts of the body fo liable to fchirro-
fity as the lymphatic glands and veflels, infomuch

that

356 RETROGRADE ABSORBENTS. SECT. XXIX. 2.

that their fchirroilties have acquired a diftind name,
and been termed fcrophula.

4. There are valves in other parts of the body,
analogous to thofe of the abforbent fyflem, and
which are liable, when difeafed, to regurgitate their
contents : thus the upper and lower orifices of the
flomach are clofed by valves, which, when too great
quantities of warm water have been drank with a
defign to promote vomiting, have fometimes refift-
ed the utmofl efforts of the abdominal mufcles, and
diaphragm : yet, at other times, the upper valve,
or cardia, eafily permits the evacuation of the con-
tents of the flomach ; whilft the inferior valve, or
pylorus, permits the bile, and other conten;s of the
duodenum, to regurgitate into the flomach.

5. The valve of the colon is well adapted to pre-
vent the retrograde motion of the excrements ; yet,
as this valve is poiTefied of a living power, in the
iliac paflion, either from fpafm, or other unnatural
exertions, it keeps itfeif open, and either fuffers or
promotes the retrograde movements of the contents
of the inteftines below ; as in ruminating animals
the mouth of the firft flomach feems to be fo con-
flruded, as to facilitate or aflift the regurgitation of
the food ; the rings of the cefophagus afterwards
contracting themfelves in inverted order. De liaen,
by means of a fyringe, forced fo much water into
the redum inteflinum of a dog, that he vomited it
in a full flream from his mouth ; and in the iliac
paflion above mentioned, excrements and clyfler
are often evacuated by the mouth. See Sedion
XXV. 15.

6. The punda lacrymalia, with the lacrymai
fack and nafal dud, compofe a complete gland, and
much refemble the inteflinal canal : the punda
lacrymalia are abforbent mouths, that take up the
tears from the eye, when they have done their office
there, and convey them, into the noftrils 5 but when

the

SECT. XXIX. 3. RETROGRADE ABSORBENTS. 357

the nafal duel is obftructed, and the lacrymal fac1*
diftended with its fluid, on preflure with the finger
the mouths of this gland (pun&a lacrymalia) will
readily difgorge the fluid, they had previoufly
abforbed, back into the eye.

7. As the capillary vefiels receive blood from the
arteries, and feparating the mucus, or perfpirable
matter from it, convey the remainder back by the
veins ; thefe capillary veflels are a let of glands, in
.every refpect fimilar to the fecretory veflels of the
liver, or other large congeries of glands. The be-
ginnings of thefe capillary veflels have frequent
anaftomofes into each other, in which circumstance
they are refembled by the lacteals ; and like the
mouths or beginnings of other glands, they are a
fet of abforbent veflels, which drii>k up the blood
which is brought to them by the arteries, as the
chyle is drunk up by the lacleals : for the circula-
tion of the blood through the capillaries is proved
to be independent of arterial impulfe ; fince in the
blulh of fhame, and in partial inflammations, their
aclion is increafed, without any increafe of the mo-
tion of the heart.

8. Yet not only the mouths, or beginnings of
thefe anaftomofing capillaries are frequently feen by
microfcopes, to regurgitate fome particles of blood,
during the ftruggles of the animal; but retrograde
motion of the blood, in the veins of thofe animals,
from the very heart of the extremity of the limbs,
is obfervable, by intervals, during the dittrefles of
the dying creature. Haller, Elem. Phyfioi. t. i.
p. 216. Now, as the veins have perhaps all of
them a valve fomewhere between their extremities
and the heart, here is ocular demonflration of the
fluids in this difeafed condition of the animal, re-
pafling through venous valves : and it is hence
highly probable, from the ftricteft analogy, that if
the courfe of the fluids, in the lymphatic veflels,

could

RETROGRADE ABSORBENTS. SECT. XXIX. £

could be fubje&ed to microfcopic obfervation, they
would alfo, in the difeafed ftate of the animal, be
feen to repafs the valves, and the mouths of thofe
vefTels, which had previoufly abforbed them, or
promoted their progrefiion.

IJI. Communication from the Alimentary Canal to the
Bladder, by means of the Abforbent Veffels,

MANY medical philofophers, both ancient and
modern, have fufpecled that there was a nearer
communication between the ftomach and the urinary
bladder, than that of the circulation : they were
led into this opinion from the great expedition with
which cold water, when drank to excefs, pafTes off
by the bladder ; and from the fimilarity of the
urine, when produced in this hafty manner, with
the material that was drank.

The former of thefe circumftances happens per-
petually to thofe who drink abundance of cold
water, when they are much heated by exercife, ancj,
to many at the beginning of intoxication.

Of the latter, many inftaaces are recorded by
Etmuller, t. xi. p. 716. where fimple water, wine,
and wine with fugar, and emulfions, were returned
by urine unchanged. ,

There are other experiments, that feem to de-
monftrate the exigence of another paiTage to the
bladder, befides that through the kidneys. Thus
Dr. Kratzenftein put ligatures on the ureters of a
dog, and then emptied the bladder by a catheter;
yet in a little time the dog drank greedily, and
made a quantity of water, (Difputat. Morbor.
Halleri. t. iv. p. 63.) A fimiiar experiment is re-
lated in the Philofophical Tranfaclions, with the
fame event, (No. 65, 67, for the year J67O.)

Add to this, that in fome morbid cafes the urine
has continued to pafs, after the fuppiiration or total

deftru&ion

SECT. XXIX. 3. RETROGRADE ABSORBENTS. 359

deftru&ion of the kidneys ; of which many In-
ftances are referred to in the Elem. Phyfiol. t. vii.
p. 379. of Dr. Haller.

From all which it muft be concluded, that fome
fluids have pafled from the ftomach or abdomen,
without having gone through the fanguiferous cir-
culation : and as the bladder is fupplied with many
lymphatics, as defcribed by Dr. Watfon, in the
Philof. Tranf. v. 59. p. 392. and as no other veflels
open into it befides thefe and the ureters, it feems
evident, that the unnatural urine produced as above
defcribed, when the ureters were tied, or the kid-
neys obliterated, was carried into the bladder by
the retrograde motions of the urinary branch of
the lymphatic fyftem.

The more certainly to afcertain the exiflence of
another communication between the ftomach and
bladder, befides that of the circulation, the follow-
ing experiment was made, to which I muft beg
your patient attention : — A friend of mine (June
14, 1772) on drinking repeatedly of cold fmali
punch, till he began to be intoxicated, made a
quantity of colourlefs urine. He then drank about
two drams of nitre diflblved in fome of the punch,
and eat about twenty ftalks of boiled afparagus : on
continuing to drink more of the punch, the next
urine that he made was quite clear, and without
ftnell ; but in a little time another quantity was
made, which was not quite fo colourlefs, and had a
ftrong fmell of the afparagus : he then loft about
four ounces of blood from the arm.

The fmell of afparagus was not at all perceptible
in the blood, neither when frem taken, nor the
next morning, as myfelf and two others accurately
attended to ; yet this fmell was ftrongly perceived
in the urine, which was made juft before the blood
was taken from his arm.

Some

360 RETROGRADE ABSORBENTS. SECT. XXIX. 4,

Some bibulous paper, moiftened in the ferum of
this blood, and fuffered to dry, (hewed no figns of
nitre by its manner of burning. But fome of the
fame paper* moiftened in the urine, and dried, ori
being ignited, evidently fliewcd the prefence of
nitre. This blood and the urine flood fome days
cxpofed to the fun in the open air, till they were
evaporated to about a fourth of their original quan-
tity, and be^an to (link : the paper which was then
moiftened with the concentrated urine, mewed the
prefence of much nitre by its manner of burning ;
whilft that moiftened with the blood (hewed no fuch
appearance at all.

Hence it appears, that certain fluids at the begin-
ning of intoxication, firid another paflage to the
bladder befides the long courfe of the arterial cir-
culation; and as the inteftinal abforbents are joined
with the urinary lymphatics by frequent anaftomo-
fes, as Hewfon has demonftfated ; and as there is
no other road, we may juftly conclude, that thefe
fluids pafs into the bladder by the urinary branch
of the lymphatics, which has its motions inverted
during the difeafed ftate of the animal.

A gentleman, who had been fome weeks affected
with jaundice, arid whofe Urine was in cohfequence
of a very deep yellow^ took fome cold fmall punch,
in which was dilfolved about a dram of nitre ; he
then took repeated draughts of the punch, and
kept himfelf in a cool room, till on the approach
of flight intoxication he made a large quantity of
water ; this water had a flight yellow tinge, as
might be expected from a fmall admixture of bile
fecreted from the kidneys 5 but if the whole of it
had pafled through the languiferous veflels, which
were now replete with bile (his whole (kin being as
yelfow as gold) would not this urine alfo, as well as
that he had made for weeks before, have been of a
deep yellow ? Paper dipped in this watef, ahdi

dryedj

SECT. XXIX. 4. RETROGRADE ABSORBENTS. 361

dryed, and ignited, (hewed evident marks of the
prefence of nitre, when the flame was blown out.

IV. Tie Phenomena of the Diabetes explained, and of
fome Diarrhoeas.

THE phenomena of many difeafes are only ex-
plicable from the retrograde motions of fome of the
branches of the lymphatic fyftem ; as the great and
immediate flow of pale urine in the beginning of
drunkennefs ; in hyfteric paroxyfms ; from being
expofed to cold air ; or to the influence of fear or
anxiety.

Before we endeavour to illuftrate this doctrine,
by defcribing the phenomena of thefe difeafes, we
muft premife one circumftance ; that all the
branches of the lymphatic fyftem have a certain
fympathy with each other, infomuch that when one
branch is ftimulated into unufual kinds or quan-
tities of motion, fome other branch has its motions
either increafed, or decreafed, or inverted at the
fame time. This kind of fympathy can only be
proved by the concurrent teftimony of numerous
facts, which will be related in the courfe of the
work. 1 (hall only add here, that it is probable,
that this fympathy does not depend on any commu-
nication of nervous filaments, but on habit ; owing
to the various branches of this fyftem having fre-
quently been ftimulated into action at the fame
time.

There are a thoufand inftances of involuntary
motions aflbciated in this manner ; as in the a& of
vomiting, while the motions of the ftomach and
cefophagus are inverted, the pulfations of the arte-
rial fyftem by a certain fympathy become weaker ;
and when the bowels or kidneys are ftimulated by
poifon, a ftone, or inflamation, into more violent
adion ; the ftomach and cefophagus by fympathy in-
vert their motions.

I. When

362 RETROGRADE ABSORBENTS. SECT. XXIX. £

1. When any one drinks a moderate quantity of
vinous fpirit, the whole fyftem acts with more
energy by confent with the ftomach and inteftines,
as is feen from the glow on the fkin, and the increafe
of ftrength and activity ; but when a greater quan»
tity of this inebriating material is drank, at the
fame time that the lafteals are excited into greater
action to abforb it ; it frequently happens, that the
urinary branch of abforbents, which is connected
with the lacteals by many anaftomofes, inverts its
motions, and a great quantity of pale unanimalized
urine is difcharged* By this wife contrivance too
much of an unneceffary fluid is prevented from
entering the circulation—This may be called the
drunken diabetes, to diftinguilh it from the other
temporary diabetes, which occur in hyfteric difea-
fes, and from continued fear or anxiety.

2. If this idle ingurgitation of too much vinous
fpirit be daily practifed, the urinary branch of ab-
forbents at length gains an habit of inverting its
motions, whenever the la&eals are much ftimula-
ted ; and the whole or a great part of the chyle is
thus daily carried to the bladder without entering
the circulation, and the body becomes emaciated.
This is one kind of chronic diabetes^ and may be
diflinguifhed from the others by the tafte and ap-
pearance of the urine; which is fweet, and the
colour of whey, and may be termed the chylife-
tous diabetes.

3 Many children have a fimilar difpofition of
chyle in their urine, from the irritation of worms in
their inteftines, which ftimulating the mouths of
the lafteals into unnatural a&ion, the urinary
branch of the abforbents becomes inverted, and
carries part of the chyle to the bladder ; part of the
chyle alfo has been carried to the iliac and lumber
'glands, of which inftances are recorded by Haller,
t. vii. 2 25. and which can be explained on no other

theory ;

XXIX 4. RETROGRADE ABSORBENTS. 363

theory : hut the directions of the lymphatic fyftem
of the human body, v/hich have yet been publifh-
ed, are not fufficiently extenfive for our purpofe ;
Jet if we may reafon from comparative anatomy,
this tranflation of chyle to the bladder is much
illuftrated by the account given of this fyflem of
vefiels in a -turtle, by Mr. Hewfon, who obferved,
" That the la&eals near the root of the mefentery
anaftomofe, fo as to form a net-work, from which
feveral large branches go into fome confiderable
lymphatics lying near the fpine ; and which can be
traced almoft to the anus, and particularly to the
kidneys. Philof. Tranf. v. 59. p. 199 — Enquiries,
p. 74.

4. At the fame time that the urinary branch of
abforbents, in the beginning of diabetes, is excited
into inverted action, the cellular branch is excited
by the fympathy above mentioned, into more ener-
getic action ; and the fat, that was before depofited,
is reabforbed and thrown into the blood vefiels ;
\vhere it floats, and was miftaken for chyle, till the
late experiments of the ingenious Mr. Hewfon de-
monflrated it to be fat.

This appearance of what was miftaken for chyle
in the blood, which was drawn from thefe patients,
and the obftructed liver, which very frequently
accompanies this difeafe, feems to have led Dr.
Mead to fulpect the diabetes was owing to a defect
of fanguifkation ; and that the fchirrofity of the
liver was the original caufe of it; but as the fchir-
rhus of the liver is moft frequently owing to the
fame caufes, that produce the diabetes and dropfies;
namely, the great ufe of fermented liquors ; there
is no wonder they mould exift, together, without
being the confequence of each other.

5. If the cutaneous branch of abforbents gains a
habit of being excited into ftronger action, and
imbibes greater quantities of moifture from the

VOL. I. B b atmofphere,

364 RET AGGRADE ABSORBENTS. SECT. XXIX- 4

atmofpbere, at the fame time that the urinary
branch has its motions inverted, another kind of
diabetes is formed, which may be termed the aque-
ous diabetes. In this diabetes the cutaneous abfor-
bents frequently imbibe an amazing quantity of
atmofpheric moifture, infomuch that there are au-
thentic hiftories, where many gallons a day, for
many weeks together, above the quaritity that has
been drank, have been difcharged by urine.

Dr. Keil, in his Medicina Statica, found that he
gained eighteen ounces from the moid air of one
night ; and Dr. Percival affirms, that one of his
hands imbibed, after being well chafed, near an
ounce and half of water, in a quarter of an hour.
(Tranfaft. of the College, London, vol. ii. p. 102.)
Home's Medic. Fads, p. 2. feel. 3.

The pale urine in hyfterical women,, or which is
produced by fear or anxiety, is a temporary com-
plaint of this kind ; and it would in reality be the
fame difeafe, if it was confirmed by habit,

6. The purging (loots, and pale urine, occafion-
ed by expofing the naked body to cold air, or
fprinkling it with cold water, originate from a fimi-
tar caufe \ for the mouths of the cutaneous lympha-
tics being fuddenly expofed to cold become torpid,
^and ceafe, or nearly ceafe, to ad; whilft, by the
fympathy above d.efcribed, not only the lymphatics
of the bladder and inteftines ceafe alfo to abforb
the more aqueous and faline part of the fluids fecre-
ted into them ; but it is probable that theie lym-
phatics invert their motions, and return* the fluids,
which were previouily abforbed, into the inteftines
and bladder. At the very inflant that the body is
expofed naked to the cold air, an unufual movement
is felt in the bowels ; as is experienced by boya
going into the cold bath : this could not occur from
. an obftru&ion of the perfpirable matter, fince there

is

5tCT.XXiX.4. RETROGRADE ABSORBENTS, 365

is not time for that to be returned to the bowels by
the courfe of the circulation.

There is alfo a chronic aqueous diarrhoea, in
which the atmofpheric moifture, drank up by the
cutaneous and pulmonary lymphatics, is poured
into the inteftines, by the retrograde motions of
the lacteals. This difeafe is mod fimilar to the
aqueous diabetes, and is frequently exchanged for
it : a diftinft inflance of this is recorded by Ben-
ningerus, Cent. v. Obf. 98. in which an aqueous
diarrhoea fucceeded an aqueous diabetes, and de-
ftroyed the patient* There is a curious example of
this, described by Sympfon fDe Re Medica) — " A
young man (fays he) was feiz'ed with a fever, upon,
which a diarrhoea came on, with great ftupor; and
he refufed to drink any thing, though he was parch-
ed up with exceflive heat : the better to fupply him
with moifture, I directed his feet to be immerfed in
cold water ; immediately I obferved a wonderful
decreafe of water in the veflel, and then an impe-
tuous ftream of a fluid, fcarcely coloured, was dif-
charged by ftool, like a cataract. "

7. There is another kind of diarrhoea, which has
been called cseliaca ; in this difeafe the chyle, drank
up by the lacleals of the fmall inteftines, is proba-
bly poured into the large inteftines, by the retro-
grade motions of their lacleals : as in the chylife-
rous diabetes, the chyle is poured into the bladder,
by the retrograde motions of the urinary branch of
abforbents.

The chyliferous diabetes, like this chyliferous
diarrhoea, produces fudden atrophy ; fmce the nou-
ri&ment, which ought to fupply the hourly wafte
of the body, is expelled by the bladder, or reclum :
whilft the aqueous diabetes, and the aqueous diarr-
hoea produce exceflive thirft ; becaufe the. moifture,
which is obtained from the atmofphere, is not con-
veyed to the thoracic receptacle, as it ought to be,

B b 2 but

RETROGRADE ABSORBENTS. SECT. XXlX 4

but to the bladder, or lower inteflines ; whence the
chyle, blood, and whole fyftem of glands, are rob-
bed of their proportion of humidity.

8. There is a third fpecies of diabetes, in which
the urine is mucilaginous, and appears ropy in
pouring it from one veflel into another ; and will
fometimes coagulate over the fire. This difeafe
appears by intervals, and ceafes again, and feems
to be occafioned by a previous dropfy in fome part
of the body. When fuch a collection is reabforbed,
it is not always returned into the circulation ; but
the fame irritation that Stimulates one lymphatic
branch to reabforb the depofited fluid, inverts the
urinary branch, and pours it into the bladder,
Hence this mucilaginous diabetes is a cure, or the
confequence of a cure, of a worfe difeafe, rather
than a difeafe itfelf.

Dr. Cotunnius gave half an ounce of cream of
tartar, every morning, to a patient, who had the
anafarca ; and he voided a great quantity of urine ;
a part of which, put over the fire, coagulated, on
the evaporation of half of it, fo as to look like the
jarhite of an egg. De Ifchiade Nervos.

This kind of diabetes frequently precedes a
dropfy ; and has this remarkable circumilance at-
tending it, that it generally happens in the nighty
as during the recumbent ftate of the body, the fluid,
that was accumulated in the cellular membrane.,
or in the lungs, is more readily abforbed, as it is
lefs impeded by its gravity. I have feen more than
one inftance of this difeafe. Mr. D. a man in the
decline of life, who had long accuftomed himfelf
to fpirituous liquor, had fwelled legs, and other
fymptoms of approaching anafarca j about once in
a week, or ten days, for feveral months, he was
feized, on going to bed, with great general uneafi-
nefs, which his attendants refembled to an hyfteric
fit $ and which terminated jp a great difeharge of

vifcid

S*CT. XXIX. 4. RETROGRADE ABSORBENTS. 367

vifcid urine ; his legs became lefs fwelled, and he
continued in better health for fome days afterwards,
I had not the opportunity to try if this urine would
coagulate over the fire, when part of it was evapo-
rated, which I imagine would be the criterion of
this kind of diabetes ; as the mucilaginous fluid de-
pofited in the cells and cyfts of the body, which
have no communication with the external air, feems
to acquire, by ftagnation, this property of coagula-
tion by heat, whieh the fecreted mucus of the in-
teftines and bladder do not appear to potTefs ; as I
have found by experiment; and if any one fhould
fuppofe this coagulable urine was feparated from the
blood by the kidneys, he may recollect that in the
moft inflammatory difeafes, in which the blood is
niofl replete or moft ready to part with the coagu-
lable lymph, none of this appears in the urine.

9. Different kinds of diabetes require different
methods of cure. For the firft kind, or chylife-
rous diabetes, alter clearing the ftomach and in-
tedines, by ipecacuanha and rhubarb, to evacuate
any acid material, which may too powerfully ftimu-
late the mouths of the lacteals, repeated and large
dofes of tincture of cantharides have been much re-
commended. The fpeciftc flimulus of this medi-
cine, on the neck of the bladder, is likely to excite
the numerous abforbent veflels, which are fpread on
that part, into ftronger natural actions, and by that
means prevent their retrograde ones ; till, by per-
fifting in the ufe of the medicine, their natural
habits of motions might again be eftablifhed,
Another indication of cure, requires fuch medicines,
as by lining the inteflines with mucilaginous fub-
ftances, or with iuch as confifl of fmooth particles,
or which chemically deftroy the acrimony of their
contents, may prevent the too great action of the
inteftinal abiorbents. For this purpofe, I have
found the earth precipitated from afolution of alum,

by

36$ RETROGRADE ABSORBENTS. SECT. XXIX. 4,

by means of fixed alcali, given in the dofe of half a
dram every fix hours, of great advantage, with a
few grains of rhubarb, fo as to produce a daily eva^
cuation.

The food fhould confift of materials that have the
leaft ftimulus, with calcareous water, as of Briflol
and Matlock; that the mouths of the laOeals may
be as little ftimulated as is neceffary for their proper
abforption ; left with their greater exertions, fhould
be connected by fympathy, the inverted motions of
the urinary lymphatics.

The fame method may be employed with equal
advantage in the aqueous diabetes, fo great is the
fympathy between the (kin and the ftomach. To
which, however, fome application to the fkin might
be ufefully added ; as rubbing the patient all over
with oil, to prevent the too great adion of the cuta*
neous abforbents. I knew an experiment of this
kind made upon one patient with apparent adyan?
tage.

The mucilaginous diabetes will require the fame
treatment, which is mod efficacious in the dropfy,
and will be defcribed below. I mud add, that the
diet and medicines above mentioned, are ftrongly
recommended by various authors, as by Morgan,
Willis, Harris, and Etmuller; but more hiftories
of the fuccefsful treatment of thefe difeafes are
•wanting to fully afcertain the moil efficacious me-
thods of cure.

In a letter from Mr. Charles Darwin, dated April
24, 1778, Edinburgh, is the fubfequent paiTage: — •
" A man who had long laboured under a diabetes
died yefterday in the clinical ward. He had for
fome time drank four, and pafled twelve pounds of
fluid daily ; each pound of urine contained an ounce
of lugar. He took, without confiderable relief,
gum kino, fanguis draconis melted with alum, tinc-
ture of cantharides, ifinglafs, gum arabic, crabs.

SECT. XXIX. 4. RETROGRADE ABSORBENTS. 369

eyes, fpirit of hartfhorn, and eat ten or fifteen
cyders thrice a day. Dr. Home, having read my
thefis, bled him, and found that neither the frefh
blood nor the ferum tafted fweet. His body was
opened this morning — every vifcus appeared in a
found and natural ftate, except that the left kidney
had a very fmall pelvis, and that there was a con-
fiderable enlargement of moft of the mefenteric lym-
phatic glands. I intend to infert this in my thefis,
a£ it coincides with the experiment, where fome
afparagus was eaten at the beginning of intoxica-
tion, and its fmell perceived in the urine, though
not in the blood. '

The following cafe of chyliferous diabetes is ex-
tracted from fome letters of Mr. Hughes, to whofe
unremitted care the infirmary at Stafford for many
years was much indebted. Dated October 10,

1778-

Richard Davis, aged 33, a whitefmith by trade,
had drank hard by intervals ; was much tro'ubled
with fwead-ng of his hands, which incommoded him
in his occupation, but which ceafed on his fre-
quently dipping them in lime. About feven months
ago he began to make large quantities of water ;
his legs are cedematous, his belly tenfe, and he
complains of a rifing in his throat, like the globus
hyftericus : he eats twice as much as other people,
drinks about fourteen pints of fmall beer a day,
befides a pint of ale, fome milk-porridge, and 3.
baion of broth, and he makes about eighteen pint§
of water a-day.

He tried alum, dragon's .blood, flee!, blue vitriol,
and cantharides in large quantities, and duly re-
peated, under the care of Dr. Underbill, but with-
out any effect ; except that on the day after he
omitted the cantharides, he made but twelve pints
of water, but on the next day this good effect ceafed

37° RETROGRADE ABSORBENTS. SECT. XXIX. 4,

November 21. — He made eighteen pinrs of water,
and he now, at Dr. Darwin's requeft, took a grain
of opium every four hours, and five grains of aloes
at night ; and had a flannel fhirt given him.

22. — Made fixteen pints. 23, — Thirteen pints :
drinks lefs,

24. — Increafed the opium to a grain and quarter
every four hours : he made twelve pints.

25." — Increufed the opium to a grain and half :
he now makes ten pints j and drinks eight pints in
a day.

The opium was gradually increafed during the
next fortn'ght, till he took three grains every four
hours, but without any further diminution of his
water. During the ufe of the opium he fweat much
in the nights, fo as to have large drops ftand on
his face and all over him, The quantity of opium
was then gradually decreafed, but not totally omit-
ted, as he continued to take aboiit a grain morning
and evening.

January 17. — He makes fourteen pints of water a
day. Dr. Underhill now directed him two fcruples
of common rofm triturated with as much fugar,
every fix hours ; and three grains of opium every
night.

19.— Makes fifteen pints of water: fweats at
night.

21. — Makes feyenteen pints of water ; has twitch-
ings of his limbs in a morning, and pains of his
legs : he now takes a dram of rofm for a dofe, and
continues the opium.

23. — Water more coloured, and reduced to fix-
teen pints, and he thinks has a brackifh tafle.

26. -Water reduced to fourteen pints.

28. — -Water thirteen pints ; he continues the
opium, and takes four fcruples of the rofm for a
dofe.

February i. — Water twelve pints.

4CrWatcr

SECT. XXIX. 4. RETROGRADE ABSORBENTS. 371

4.— Water eleven pints : twitchings lefs ; takes
five fcrupl'is for a dole.

8.— Water ten pints: has had many (tools,

12. — Appetite lefs : purges very much.

After this the roiin either purged him, or would
not ftay on his ftomat h ; and he gradually relapfed
nearly to his former condition, and in a few months
funk under the difeafe.

October 3, Mr. Hughes evaporated two quarts
of the water, and obtained from it four ounces and
half of a hard and brittle faccharine rnafs, like trea-
cle which had been fome time boiled. Four ounces
of blood, which he took from his arm with defign.
to examine it, had the common appearances, ex-
cept that the ferum refembled cheeie-whey ; and
that on the evidence of four perfons, two of whom
did not know what it was they tailed, the ferum had
aj'iltijh t-ifte.

From hence it appears, that the faccharine matter,
with which the urine of thefe patients fo much
abounds, does not enter the blood-veflels like the
nitre and afparagus mentioned above ; but that the
proceis of digeftion relembles the procefs of the
germination of vegetables, or of making barley into
malt; as the vait quantity of fugar found in the
jurine mud be made from the food which he took
(which was double that taken by others), and from
the fourteen pints of fmall beer which he drank.
And, fecondly, as the ferum of the blood was not
fweet, the chyle appears to have been conveyed to
the bladder without entering the circulation of the
blood, lince fo large a quantity of fugar, as was
found in the urine, namely, twenty ounces a day,
could not have previoufly exifted in the blood with-
out being perceptible to the tafte.

November i. Mr. Hughes diflblved two drams
of nitre in a pint of a decoction of the roots of
afparagus, and added to it two ounces of tincture

of

57* RETROGRADE ABSORBENTS. SECT. XXIX. 4.

I

of rhubarb : the patient took a fourth part of this
mixture every five minutes, till he had taken the
whole. — In about half an hour he made eighteen
ounces of water, which was very manifeftly tinged
with the rhubarb j the fmell of the afparagus was
doubtful.

He then loft four ounces of blood, the ferum of
which was not fo opake as that drawn before, but
of a yellowim caft, as the ferum of the blood
ufually appears.

Paper, dipped three or four times in the tinged
urine and dried again, did not fcintillate when it
was fet on fire; but tfhen the flame was blown out,
the fire ran along the paper for half an inch ; which,
when the fame paper was unimpregnated, it would
not do ; nor when the fame paper was dipped in
urine made before he took the nitre, and dried in
the fame manner.

Paper, dipped in the ferum of the blood and
dried in the lame manner as in the urine, did not
fcintillate when the flame was blown out, but burnt
exactly in the fame manner as the fame paper dip-
ped in the ferum of blood drawn from another per*
fon.

This experiment, which is copied from a letter
of Mr. Hughes, as well as the former, feems to
evince the exiftence of another paflage from the
inteftines to the bladder, in this difeafe, befides that
of the fanguiferous fyftem ; and coincides with the
curious experiment related in fedlion the third,
except that the fmell of the afparagus was not here
perceived, owing perhaps to the roots having been
made ufe of inftead of the heads.

The rifing in the throat of this patient, and the
twhchings of his limbs, feem to indicate fome fimi-
larity between the diabetes and the hyfteric difeafe,
befides the great flow of 'pale urine, which is com-
mon to them both.

Perhaps

SECT. XXIX. 5. RETROGRADE ABSORBENTS. 375

Perhaps if the mefenteric glands were nicely in*
fpefted in the diffeftions of thefe patients ; and if
the thoracic duel, and the larger branches of the
lacteals, and if the lymphatics, which arile from the
bladder, were well examined by injection, or by
the knife, the caufe of diabetes might be more ceiv
tainly underllood.

'I lie opium alone, and the opium with the rofm,
feem much to have ferved this patient, and might
probably have effected a cure, if the difeafe had
been (lighter, or the medicine had been exhibited,
before it had been confirmed by habit during the
feven months it had continued. The increafe of
the quantity of water on beginning the large dofes
of rofm was probably owing to his, omitting the
jnorning dofes of opium.

V. The Phenomena of Dropjtes explained,.

I. SOME inebriates have their paroxyfms of in-
ebriety terminated by much pale urine, or profufe
fweats, or vomiting, or (tools ; others have their .
paroxyfms terminated by ftupor, or fleep, without
the above evacuations.

The former kind of thefe inebriates have been
obferved to be more liable to diabetes and dropfy ;
and the latter to gout, gravel, and leprofy. Evoe !
attend ye bacchanalians ! dart at this dark train of
evils, and, amid yqar immodeft jefts, and idiot
laughter, recoiled,

Quern Deus volt perdere, prius dementat.

In thofe who are fubjecl: to diabetes and dropfy,
the abforbent veflels are naturally more irritable
in the latter j and by being frequently diilurb-

ed

374 RETROGRADE ABSORBENTS. SECT. XXIX. s.

ed or inverted by violent ftimulus, and by their too
great fympathy with each other, they become at
length either entirely paralytic, or are only fufcep-
tible of motion from the ftimulus of very acrid
materials ; as every part of the body, after having
been ufed to great irritations, becomes lefs affe&ed
by fmaller ones. Thus we cannot diftinguim ob-
je&s in the night, for fome time after we come out
of a ftrong light, though the iris is prefently dila-
ted; and the air of a fummer evening appears cold,
after we have been expofed to the heat of the
day.

There are no cells in the body, where drqpfy may
not be produced, if the lymphatics ceafe to abforb
that mucila /inous fluid, which is perpetually de-
pofited in them, for the purpofe of lubricating their
furfaces.

If the lymphatic branch, which opens into the
cellular membrane, either does its office imperfect-
ly, or not at all ; thefe cells become replete with a
mucilaginous fluid, which, after it has ftagnated
fome time in the cells, will coagulate over the fire ;
and is erroneoufly called water. Wherever the
feat of this difeafe is, (uniefs in the lungs or other
pendent vifcera) the mucilaginous liquid above
mentioned will fubfide to the mod depending parts
of the body, as the feet and legs, when thofe are
lower than the head and trunk ; for all thefe qells
have communications with each other.

When the cellular abforbents are become infen-
ble to their ufual irritations, it mod frequently hap-
pens, but not always, that the cutaneous branch
of abforbents, which is ftridtly afibciated with them,
fuffers the like inability. And then, as no water is
abforbed from the atmofphere, the urine is not
only lefs diluted at the time of its fecretion, and
confequently in lefs quantity and higher coloured :

but

SICT. XXIX. 5. RETROGRADE ABSORBENTS.

but great third is at the fame time induced, for as
no water is abforbed from the atmofphere to dilute
the chyle and blood, the la&eals and other abfor-
bent vefiels, which have not loft their powers, are
excited into more conftant or more violent action,
to fupply this deficiency ; whence the urine be-
comes dill lefs in quantity, and of a deeper colour,
and turbid like the yolk of an egg, owing to a
greater abforption of its thinner parts. From this
ftronger action of thofe abforbents, which fiill re-
tain their irritability, the fat is alfo abforbed, and
the whole body becomes emaciated. This increafed
exertion of fome branches of the lymphatics, while
others are totally or partially paralytic, is refembled
by what conftantly occurs in the hemiplagia ; when
the patient has loft the ufe of the limbs on one
fide, he is incefiantly moving thofe of the other ;
for the moving power, not having accefs to the
paralytic limbs, becomes redundant in thofe which
are not difeafed.

The paucity of urine and thirft cannot be ex-
plained from a greater quantity of mucilaginous
fluid being depofited in the cellular membrane : for
though thefe fymptoms have continued many weeks,
or even months, this collection frequently does not
amount to more than very few pints. Hence alfo
the difficulty of promoting copious fweats in anafarca
is accounted for, as well as the great thirft, paucity
of urine, and lofs of fat ; (ince, when the cutane-
ous branch of abforbents is paralytic, or nearly fo,
there is already too fmall a quantity of aqueous
fluid in the blood : nor can thefe torpid cutaneous
lymphatics be readily excited into retrograde mo-
tions.

Hence likewife we under ftand, why in the af-
cites, and fome other dropfies, there is often no
thirft, and no paucity of urine ; in thefe cafes

the

RETROGRADE ABSORBENTS. ^ECT. XX1&. f.

the cutaneous abforbents continue to do their
office.

Some have believed, that dropfies were occafion-
ed by the inability of the kidneys, from having only
obferved the paucity of urine ; and have theflce
laboured much to obtain diuretic medicines ; but
it is daily obfervable, that thofe who die of a total
inability to make water, do not become dropficai
in confequence of it : Fernelius mentions one, who
laboured under a perfect fuppreflion of urine during
twenty days before his death, and yet had no fyrop-
toms of dropfy. Pathol. 1. vi. c. 8. From the
fame idea many pbyficians have retrained their pa-
tients from drinking, though their thirft has been
very urgent ; and fome cafes have been publifhed,
where this cruel regimen has been thought advan-
tageous : but others of nicer obfervation are of
opinion, that it has always aggravated the diftrefies
of the patient ; and though it has abated his fwell-
ings, yet by inducing a fever it has haftened his
difiblution. See Tranfaclions of the College, Lon-
don, vol. ii. p. 235. Cafes of Dropfy by Dr. G<
Baker.

The cure of anafarca, fo far as refpecls the eva-
cuation of the accumulated fluid, coincides with
the idea of the retrograde action of the lymphatic
fyftem. It is well known that vomits, and other
drugs, which induce ficknefs or naufea ; at the
fame time that they evacuate the ftomach, produce
a great abforption of the lymph accumulated in the
cellular membrane. In the operation of a vomit,
not only the motions of the ftomach and duodenum
become inverted, but alfo thofe of the lymphatics
and lafteals, which belong to them ; whence a great
quantity of chyle and lymph is perpetually poured
into the ftomach and inteftines, during the opera-
tion, and evacuated by the mouth. Now at the

fame

SECT. XXIX. 5. RETROGRADE ABSORBENTS. 377

fame time, other branches of the lymphatic fyftem,
viz. thofe which open on the cellular membrane,
are brought into more energetic action, by the
fympathy above mentioned, and an increafe of their
abforption is produced.

Hence repeated vomits, and cupreous falts, and
fmall dofes of fquill or foxglove, are fo efficacious
in this difeafe. And as draftic purges aft alfo by
inverting the motions of the la&eals ; and thence
the other branches of lymphatics are induced into
more powerful natural action, by fympathy, and
drink up the fluids from all the cells of the body ;
and by their anaftomofes, pour them into the lac-
teal branches ; which, by their inverted actions,
return them into the inteftines ; and they are thus
evacuated from the body : — thefe purges alfo are
ufed with fuccefs in discharging the accumulated,
fluid in anafarca.

II. The following cafes are related with defign
to afcertain the particular kinds of dropfy in which
the digitalis purpurea, or common foxglove, is
preferable to fquill, or other evacuants, and wrere
firft publifhed in 1780, in a pamphlet entitled Ex-
periments on mucilaginous and purulent Matter,
&c. Cadell. London. Other cafes of dropfy, treat-
ed with digitalis^ were afterwards publimed by
Dr. Darwin in the Medical Tranfadions, vol. iii. in
which there is a miflake in refpect to the dofe of the
powder of foxglove, which mould have been from
five grains to one, inftead of from five grains to '
ten.

Anafarca of the Lungs.

i. A lady, between forty and fifty years of age,
had been indifpofed fome time, was then feized
with cough and fever, and afterwards expectorated

much

•Jfrfc RETROGRADE ABSORBENTS. SECT. XXIX. 5,

much digefted mucus. This expectoration fud-
• denly ceafed, and a confiderable difficulty of brea-
thing fupervened, with a pulfe very irregular both
in velocity and flrength ; (he was much diftrefled
at firft lying down, and at firft rifing ; but after a
minute or two bore either of thofe attitudes with
eafe. She had no pain or numbnefs in her arms 5
fhe had no hectic fever, nor any cold fhiverings,
and the urine was in due quantity, and of the na-
tural colour.

The difficulty of breathing was twice confidera-
bly relieved by fmall dofes of ipecacuanha, which
operated upwards and downwards, but recurred in
a few days : (he was then directed a decoction of
foxglovej (digitalis purpurea) prepared by boiling
four ounces of the freih leaves from two pints of
water to one pint ; to which was added two ounces
of vinous fpirit : me took three large fpoonfuls of
this mixture every two hours, till me had taken it
four times; a, continued ficknefs fupervened, with
frequent vomiting, and a copious flow of urine :
thele evacuations continued at intervals for two or
three days, and relieved the difficulty of breathing
— She had fome relapfes afterwards, which were
again relieved by the repetition of the decoclian of
foxglove.

2. A gentleman, about fixty years of age, who
had been addicted to an immoderate ufe of fer*
mented liquors, and had been very corpulent, gra-
dually loft his ftrength and fleflh, had great diffi-
culty of breathing, with legs forriewhat fwelled;
and a very irregular pulfe. He was very much
diftrefied at firft lying down, and at firft rifing
from his bed, yet in a minute or two was eafy in
both thofe attitudes- He made ftraw-coloured urine
in due quantity, and had no pain or numbnefs of
his arms.

He

Jfkcr.XXlX;$. RETROGRADE ABSORBENTS. 379

He took a large fpoonful of the decodion of fox-
glove, as above, every hour, for ten or twelve fuc-
ceflive hours, had inceflant ficknefs for about two
days, and pafTed a large quantity of urine, upon
which his breath became quite eafy, and the fwell-
ihg of his legs fubfided ; but as his whole confti-
tution was already finking from the previous intem-
perance of his life, he did not furyive more than
three or four months.

Hydrops Pericardii.

3. A gentleman of temperate life and fedulou^
application to bufmefs, between thirty and forty
years of age, had long been fubjecl, at intervals, to
an irregular pulfe : a few months ago he became
vveak, with difficulty of breathing, and dry cough.
In this fituation a phyfician of eminence directed
him to abflain from all animal food arid fermented
liquor, during which regimen all his complaints
increaTed ; he now became emaciated, and totally
loft his appetite ; his pulfe Very irregular both in
velocity and ftrength; with great difficulty of breath-
ing, and fo me f welling of his legs; yet he could
lie down horizontally in his bed, though he got
little fleep, and paflfed a due quantity of urine, and
of the natural colour: no fullnefs or hardnefs could
be perceived about the region of the liver ; and he
had no pain or numbnefs in his arms.

One night he had a moft profufe fweat all ovec
his body and lim'bs, which quite deluged his bed,
and for a day or two fomewhat relieved his diffi-
culty of breathing, and his puife became lefs irre-
gular : this copious fweat recurred three or four
times at the intervals of five or fix days,, and re-
peatedly alleviated his fymptonis.

C G He

380 RETROGRADE ABSORBENTS. SECT. XXIX. $.

He was direded one large fpoonful of the above
decoction of fox-glove every hour, till it procured
fome considerable evacuation : after he had taken
it eleven fucceffive hours he had a few liquid ftools,
attended with a great flow of urine, which lad had
a dark tinge, as if mixed with a few drops of
blood : he continued fick at intervals for two days,
but his breath became quite eafy, and his pulfe quite
regular, the fwelling of his legs difappcared, and
his appetite and fleep returned.

He then took thiee grains of white vitriol twice
a day, with fome bitter medicines, and a grain of
opium with five grains of rhubarb every night ; was
advifed to eat fiefh meat, and fpice, as his {lomach
would bear it, with fmall beer, and a few glafles
of wine ; and had iiTues made in his thighs , and
has fuffered no relapfe^

4. A lady, about fifty years of age, had for fome
weeks great difficulty of breathing, with very irre-
gular pulfe, and confiderable general debility : fhe
could lie down in bed, and the urine was in due
quantity and of the natural colour, and fhe had no
pain or numbnefs of her arms.

She took one large fpoonful of the above decoc-
tion of foxglove every hour, for tenor twelve fuc-
ceflive hours ; was lick, and made a quantity of
pale urine for about two days, and was quite re-
lieved both of the difficulty of breathing, and the
irregularity of 'her pulfe. She then took a grain of
opium, and five grains of rhubarb, every night,
fqr many weeks ; with fome flight chalybeate and
bitter medicines, and has fuffered no relapfe.

Hydrops TTiorads.

5. A tradefman, about fifty years of age, became
weak- and Ihort of breath, efpecially on increafe of

motion*

SECT. XXIX. 5. RETROGRADE ABSORBENTS, 381

motion, with pain in one arm, about the infertion
of the biceps mufcle. He obferved he fometimes
in the night made an unufual quantity of pale
\vater. He took calomel, alum, andperuvian bark,
and all his fymptoms increafed: his legs began ta
fwell confiderably ; his breath became more diffi-
cult, and he could not lie down in bed ; but all
this time he made a due quantity of ilraw-coloured
water.

The decoclion of foxglove was given as in the
preceding cafes, which operated chiefly by purging,
and feemed to relieve his breath for a day or two ;
but alfo feemed to contribute to weaken him. — He
became after fome weeks univerfally dropfical, and
died comatous.

6. A young lady of delicate conftitution, with'
light eyes and hair, and who had perhaps lived too'
abflemioufly both in refpe6t to the quantity and
quality of what Che eat and drank, was feized with
great difficulty of breathing, fo as to threaten im-
mediate death. Her extremities were quite cold,
and her breath felt cold to the back of one's hand.
She had no fweat, nor could lie down for a iingle'
moment ; and had previoufly, and at prefent, com-
plained of great weaknefs and pain and numbnefs'
of both her arms ; had no fwelling of her legs, no
third, water in due quantity and colour. Her fifter,
about a year before, was afflidted with fimilar fymp-
toms, was repeatedly blooded, and died univerfally
dropfical.

A grain of opium was given immediately, and
repeated every fix hours with evident and amazing
advantage ; afterwards a blifter, with chalybeates,
bitters, and eifenrial oils, were exhibited, but no-
thing had fuch eminent effecT: in relieving the
difficulty of breathing and coldnefs of her extremi-
ties as opium, by the ufe of which in a few weeks
Cc 2 file

5Sa RETROGRADE ABSORBENTS. SECT. XXIX. £

fhe perfectly regained her health, and has fuffered
uo relapfe.

Af cites.

7. A young lady of delicate conftitution having
been expofed to great fear, cold, and fatigue, by
the overturn of a chaife in the night, began with
pain and tumour in the right hypochondrium : in
a few months a flucluation was felt throughout the
whole abdomen, more diftinclly perceptible indeed
about the region of the ftomach ; fince the inte-
guments of the lower part of the abdomen gene-
rally become thickened in this difeafe by a degree
of anafarca. Her legs were not fw'elled, no third,
water in due quantity and colour. — She took the
foxglove fo as to induce ficknefs and ftools, but
without abating the fwelling, and was obliged at
length to fubmit to the opeiation of tapping.

8. A man about fixty-feven, who had long been
accuftomed to fpirituous potation, had fome time
laboured under afcites ; his legs fomewhat fwelled ;
his breath eafy in all attitudes \ no appetite ; great
third ; urine in exceedingly fmall quantity, very
deep coloured, and turbid ; pulfe equal. He took
the foxglove in fuch quantity as vomited him, and
induced ficknefs for two days ^ but procured no
flow of uiine, of diminution of his fwelling ; but
\vas thought to leave him confiderably weaker.

9. A corpulent man, accuftomed to large potati-
on of fermented liquors, had vehement cough, dif-
ficult bieathing, anafarca of his legs, thighs, and
hands, and confiderabte tumour, with evident flue-
tuation of his abdomen ; his pulfe was equal ; his
urine in fmall quantity, of deep colour, and turbid.
Thefe fwellings had been twice confiderably abated
by drailic cathartics. He took three ounces of a

of foxglove (made by boiling one ounce

of

SECT. XXIX. 5. RETROGRADE ABSORBENTS. 383

of the frefh leaves in a pint of water) every three
hours, for twq whole days ; it then began to vomit
arjd purge him violently, and promoted a great flow
of urine ; he was by thefe evacuations completely
emptied in twelve hours. After two or three months
all thefe fymp\o;us returned, and were again re-
lieved by the ufe of the foxglove ; and thus in the
ipace of about three years he was about ten times
evacuated, and continued all that time his ufual
potations: excepting at fir ft, the medicine operated
only by urine, and did not appear confiderably to
weaken him. — The laft time he took it, it had no
effect ; and a few weeks afterwards he vomited a
great quantity of blood, and expired.

QJEJERIES.

1. As the firft fix of thefe patients had a due
difcharge of urine, and of the natural colour, was
ijot the feat of the difeafe confined to fome part of
the thorax, and the fwelling of the legs rather a
fymptom of the obftrucled circulation of the blood,
than of a paralyi'is of the cellular lymphatics of
thofe parts ?

2. When the original difeafe is a general ana-
farca, do not the cutaneous lymphatics always be-
come paralytic at the fame time with the cellular
ones, by their greater fympathy with each other ?
and hence the pau.city of urine, and the great thiril,
diftinguiih this kind of dropfy ?

3. In the anafarca of the lungs, when the difeafe
is not very great, though the patients have confi-
derable difficulty of breathing at their firft lying
down, yet after a minute or two their breath be-
comes eafy again ; and the fame occurs at their
firft rifmg. Is no,t this owing to the time neceffpry

for

384 RETROGRADE ABSORBENTS. SECT. XXIX. 5.

for the fluid in the cells of the lungs to change
its place, fo as the leaft to incommode refpiratiorj
in the new attitude ?

4. In the dropfy of the pericardium (Joes not the
patient bear the horizontal or perpendicular atti-
tude with equal eafe ? Does this circumftance dif-
tinguifh the dropfy of the pericardium from that of
the lungs and of the thorax?

5. Do the univerfal fweats diftinguifh the dropfy
of the pericardium, or of the thorax? and thofe,
which cover the upper parts of the body only, the
anafarca of the Jungs?

6. W hen in the dropfy of the thorax, the patient
endeavours to. lie down, does not the extravafated
fiui comprefs the upper parts of the bronchia, and
to- ally preclude the accefs of air to every part of
the lungs ; whilft in the perpendicular attitude the
inferior parts of the lungs only are comprefled f
Docs not fometbing fimilar to this occur in the
anafarca of the lungs, when the difeafe is very great,
and thus prevent thofe patients alfo from lying
down ?

7. As a principal branch of the fourth cervical
nerve of the left fide, after having joined a brancl>
of the third and of the fecond cervical nerves, de-
fcending between the fubclavian vein and artery,
is received in a groove formed for it in the peri-
cardium, and is obliged to make a confiderable
turn outwards to go over the prominent parj: of it,
where the point of the heart is lodged, in its courfe
to the diaphragm j and as the other phrenic nerve
of the right fide has a ftraight courfe to the dia-
phragm ; and as many other confiderable branches
of this fourth pair of cervical nerves are fpread ori
the arms ; does not a pain in the left arm diltin-
guifh a difeafe of the pericardium, as in the angina
pe&oris, or in the dropfy of the pericardium ? and

does

SECT. XXIX. 6. RETROGRADE ABSORBENTS. 38,5

does not a pain or weak nets in both arms diilin-
guith the dropfy of the thorax ?

8. Do not -the drop Iks of the thorax and pericar-
dium frequently ex: ft together, and thus and lo
the uncertainty and 'fatality of the difeafe ?

9. Might not the foxglove be ferviceable in hy-
drocephalus interims, in hydrocele, and in white
f well ings of the joints ?

, VI. Of cold Sweats.

THERE have been hiftories given of chronical im-
moderate fweatings, which bear fome analogy to
the diabetes. Dr. Willis mentions a lady then
living, whofe fweats were for many years fo pro-
fufe, that all her bed-clothes were not only moift-
ened, but deluged with them every night j and that
many ounces, and fometimes -pints, of this fweat,
were received in veflels properly placed, as it trick-
led down her body. He adds, that (he had great
thirft, had taken many medicines, and fubmitted to
various rules of life, and changes of climate, but
fiili continued jto have thefe immoderate fweats.
Pharmac. ration, de fudore anglico.

Dr. Willis has alfp obferved, that the fudor an-
glicanus which appeared in England, in 1483, and
continued till 1551, was in fome refpecls fimilar
to the diabetes ; and as Dr. Gaius, who faw this dif-
eafe, mentions the vifcidity, as well as the quantity
of thefe fweats, and adds, that the extremities were
often cold, when the internal parts wer£ burnt up
with heat and third, with great and fpeedy emaci-
ation and debility : there is great rcafon to believe,
i hat the fluids were abforbed from the cells of the
body by the cellular and cyftic branches of the lym-
phatics, and poured on the fkin by the retrograde
motions of the cutaneous ones.

Sydenhara

}S$ RETROGRADE ABSORBENTS. SECT. XXIX. 6,

Sydenham has recorded, in the ftationary fever
of the year 1685, the vifcid fweats flowing from the?
bead, which w ere' probably from the fame fource,
as thofe in the fweating plague above mentioned.

It is very common in dropfies of the cheft or
lungs to have the difficulty of breathing relieved
by copious fweats, flowing from the head and neck.
Mr. P. about 50 years of age, had for many weeks
been afflicted with anafarca of his legs and thighs,
attended with difficulty of breathing; and had re-
peatedly been relieved by fquilj, other bitters, and
chalybeates.— One night the difficulty of breathing
became fq great, that it .was thought he mutt have
expired ; but fo copious a fweat came out of his
head and neck, that in a few hours fome pints, by
eftimation, were wiped off from thofe parts, and his
breath was for a time relieved. This dyfpncea and
thefe fweats recurred at intervals, and after fome
weeks he ceafed to exift. The fkin of his head
and neck felt cold to the hand, and appeared pale
at the time thefe fweats flowed fo abundantly'; which
is a proof, that they were produced by an inverted
motion of the abforbents of thofe parts ; for fweats,
which are the confequence of an increafed a61ion
of the fanguiferousfyftem,are always attended with)
a warmth of the fkin, greater than is natural, ancl
a more florid colour ; as the fweats from exercife,
or thofe that fucceed the cold fits of agues. Can
any one explain how thefe partial fweats fhould re-
lieve the difficulty of breathing in anafarca, but by
fuppoiing that the pulmonary branch of abforbents
drank up the fluid in the cavity of the thorax, or
in the cells of the lungs, and threw it on the fkin,
by the retrograde motions of the cutaneous branch ?
for, if we could fuppofe, that the increafed adion
of the cutaneous glands or capillaries poured 'upon
the fkin this fluid, previoufly abforbed from the
Jungs ; why is not the whole furface of the body

covered

$tcT. XXIX. 6. RETROGRADE ABSORBENTS. 337

fcovered with fvveat ? why is not the {kin warm ? Add
to this, that the fwears above-mentioned were clam-
my or glutinous, which the condenfed perfpirable
matter is not ; whence it would feem to have been
a different fluid from that of common perfpira-
tion.

Dr. Dobfon, of Liverpool, has given a very inge-
nious explanation of the acid fweats, which heob-
ferved in a diabetic patient — he thinks part of the
chyle is fecreted by the (kin, and afterwards under-
goes an acetous fermentation. — Can the chyle get
thither, but by an inverted motion of the cutane-
ous lymphatics ? in the fame manner as it is carried
.to the bladder, by the inverted motions of the uri-
nary lymphatics. Medic. Obfervat. and Enq. Lon-
don, vol. v.

Are not the cold fweats in fome fainting fits, and
in dying people, owing to an inverted motion of
the cutaneous lymphatics ? for in thefe there can be
no increafed arterial or glandular action.

Is the difficulty of breathing, aiifing from ana-
farca of the lungs, relieved by fweats from the head
and neck; whilft that difficulty of breathing, which
arifes from a dropfy of the thorax, or pericardium,
is never attended with thefe fweats of the head ?
and thence can thefe difeafes be diftinguifhed from
each other ? Do the periodic returns of nocturnal
afthma rife from a temporary dropfy of the lungs,
collected during their more torpid Hate in found
fleep, and then re-abforbed by the vehement efforts
of the difordered organs of refpiranon, and carried
off by the copious fweats about the head and neck?

More extensive and accurate diffecYions of th<
lymphatic fyflem are wanting to enable us to unravt
fchefe knots of fcknce.

VII. Translations

388 RETROGRADE ABSORBENTS. SECT. XXIX. 7.

VII. Translations of Matter, of Chyle, of Milk, of
Urine. Operation of purging Drugs applied exter-
nally.

1. THE tranflations of matter from one part of
the body to another, can only receive an explana-
tion from the doctrine of the occafional retrograde
motions of fome branches of the lymphatic fyiterri :
for how can matter, abforhed and mixed with the
-whole mafs of blood, be fo haftily ..collected again
in any one part ? and is it not an immutable law, in
animal bodies, that each gland can fecrete no other,
but its own proper fluid ? which is, in part, fabri-
cated in the very gland by an animal procefs, which
it there undergoes: of thefe purulent tranflations
innumerable and very remarkable inftances are re-
corded.

2. The chyk, which is feen among the materials
thrown up by violent vomiting, or in purging ftools,
.can only come thither by its having been poured
into the bowels by the inverted motions of the lac-
teals : for our aliment is not converted into chyle in
the ftomach or inteflines by a chemical procefs, but
is made in the very mouths of the la&eals ; or iq.
the mefenteric glands; in the fame manner as other
fecreted fluids are made by an animal procefs in
xheir adapted glands.

Here a curious phenomenon in the exhibition of
mercury is worth explaining : — If a moderate dole
of calomel, or fix or ten grains, be fwallowed, and
within one or two days a cathartic is given, a fali-
vation is prevented : but after three or four days, a
falivation having come on, repeated purges every
day, for a week or two, are required to eliminate
the mercury from the conflitution. For this acrid
metallic preparation, being abforbed by the mouths
of the Jackals, continues, for a time arrefted by the

mefenteric

SECT. XXIX. 7. RETROGRADE ABSORBENTS. 389

jnefenteric glands, (as the variolous or venereal poi-
fons fwell the fubaxillar or inguinal glands) : which,
during the operation of a cathartic, is returned into
the inteitines by the inverted adion of the ladteals,
and thus carried our of the fyftem.

Hence we underftand the ufe of vomits or purges,
to thofe who have fwallowed either contagious or
poifonous materials, even though exhibited a day
or even two days after fuch accidents ; namely, that
by the retrograde motions of the ladteals and lym-
phatics, the material ftill arrefted in the mefenteric,
or other glands, may be eliminated from the body.

3. Many inftances of milk and chyle found in
ulcers are given by Haller, EL Phyfiol. t. 7. p. i2y
23, \vhich admit of no other explanation than by
fuppofing, that the chyle, imbibed by one branch of
the abforbent fyftem, was carried to the ulcer, by
the inverted motions of another branch of the fame
fyftem.

4. Mrs. P. on the fecond day after delivery, was
feized with a violent purging, in which, though
opiates, mucilages, the bark, and teftacea were pro-
fufely ufed, continued many days, till at length me
recovered. During the time of this purging, no
milk could be drawn from her J3reafts ; but the
/tools appeared like the curd of milk broken into
fmall pieces. In this cafe, was not the niilk taken
up from the follicles of the pecloral glands, and
thrown on the inteftines, by a retrogreffion of the
inteftinal abforbents? for how can we ..for a moment
fufpecl that tjie niucous glands of the inteftines
could feparate pure milk from the blood ? Dr. Smel-
ly has obferved, that loofe {tools, mixed with milk,
which is curdled in the inteftines, frequently re-
lieves the turgefcency of the breafts of thofe who
ftudioufly repel their milk. Cafes in Midwifery, 43,,
"No. 2. i.

5- J-F.

RETROGRADE ABSORBENTS. SECT. XXIX. 7.

5. J. F. Meckel obferved in a patient, whofe urine
was in fmall quantity and high coloured, that a
copious fweat under the arm-pits, of a perfectly
urinous fmell, ftained the linen ; which ceafed again
when the ufual quantity of urine was difcharged by
the urethra. Here we muft believe from analogy,
that the urine was firft fecreted in the kidneys, then
re-abforbed by the increafed aclion of the urinary
lymphatics, and laftly carried to the axillae by the
retrograde motions of the lymphatic branches of
thofe parts. As in the jaundice it is necerTary, that
the bile mould firil be fecreted by the liver, and
re-abforbed into the circulation, to .produce the yel-
lownefs of the ikin ; as was formerly demonflrated
by the late Dr. Munro, (Edin, Medical Eflays) an4
if in this patient the urine had been re-abforbed into
the mafs of blood, as the bile in the jaundice, why
was it not detected in other parts ;of the body, as
well as in the arm-pits ?

6. Cathartic and vermifuge medicines applied ex-
ternally to the abdomen, feem to be taken up by
the cutaneous branch of lymphatics, and pour-
ed on the interlines by the retrograde motions of
the lacleals, without having parted the circula*
tion. *$$

For when the draftic purges are taken by the
mouth, they excite the lacleals of. the intefl ines in-
to retrograde motions, as appears frpm the chyle,
which is found coagulated among the feces, as was
ihewn above, »t(fecl. 2 and 4.) And as the cutane-
ous lymphatics are joined with the la&eals of the
interlines, by frequent anaflomofes; it would be
more extraordinary, when a ilrong purging drug,
abforbed by the ikin, is carried to the anaftomofmg
branches of the lacleals unchanged, if it (hould not
excite them into retrograde aftion--- as efficacioufly,

StcT. XXIX. 8. RETROGRADE ABSORBENTS, 39t

as if it was taken by the mouth, and mixed with
the food of the flomach.

VIII. Cimimjiances by which the Fluids, that are effii-
fed by the retrograde Motions of the abforbent Vef-
fels, are diftinguijhed.

I. WE frequently obferve an unufual quantity of
mucus or other fluids in fome difeafes, although the
a<Slion of the glands, by which thefe fluids are fe-
parated from the blood, is not unufually increafed ;
but when the power of abforption alone is dimi-
nifhed. *Thus the catarrhal humour from the nof-
trils of fome, who ride in frofly weather ; and the
tears, which run down the cheeks of tbofe, who
have an obftrudtion of the puncla lacrymalia ; and
the ichor of thofe phagedenic ulcers, which are not
attended with inflammation, are all inftances of this
circumflance.

Thefe fluids however are eafily diflinguifhed from
others by their abounding in ammoniacal or muri-
atic falts ; whence they inflame the circumjacent
Ikin : thus in the catarrh the upper lip becomes red
and fwelled from the acrimony of the mucus, and
patients complain of the faltnefs of its taile. The
eyes and cheeks are red with the corrofive tears,
and the ichor of fome herpetic eruptions erodes far
and wide the contiguous parts, and is pungently
fait to the tafte, as fome patients have informed
me.

Whilft, on the contrary, thofe fluids, which are
efFufed by the retrograde adion of the lymphatics,
are for the mod part mild and innocent ; as water,
chyle, and the natural mucus : or they take their
properties from the materials previouily abforbed,

as

39* RETROGRADE ABSORBENTS. SECT. XXIX. 8.

as in the coloured or vinous urine, or that fcented
with afparagus, defcribed before.

2. Whenever the fecretion of any fluid is increaf-
ed, there is at the fame time an increafed heat in:
the part ; for the feereted fluid; as the bile, did not
previoufly exift in the mafs of blood, but a new
combination is produced in the gland. Now as fo-
lutions are attended with cold, fo combinations are
attended with heat ; and it is probable the fum of
the heat given out by all the feereted fluids of ani-
mal bodies may be the caufe of their general heat
above that of the atmofphere.

Hence the fluids derived from increafed fecretions
are readily diftinguiflied from thofe originating from
the retrograde motions of the lymphatics :* thus an
increafe of heat either in the difeafed parts, or dif-
fufed over the whote body, is perceptible, when
eopious bilious (tools are confequent to an inflamed
liver ; or a copious mucous falivation from the in-
flammatory angina.

3. When any feereted fluid is produced in an un-
ufual quantity, and at the fame time the power of
abforption is increafed in equal proportion, not only
the heat of the gland becomes more intenfe, but
the feereted fluid becomes thicker and milder, its
thinner and fa line parts being re-abforbed : and
thefe are diftinguifhable both by their greater con-
fidence, and by therf heat, from the fluids, which
are effufed by the retrograde motions of the lym-
phatics ; as is obfervable towards the termination of
gonorrhoea, catarrh, chincough? atd in thofe ulcers,
which are faid to abound with laudable pus.

4. When chyle is obferved in (tools, of among
the materials ejected by vomit, we may be confi-
dent it muft have been brought thither by the re-
trograde motions of the ladeals ; for chyle does not
previoufly exift amid the contents of the inceftines,

SECT. XXIX. 9. RETROGRADE ABSORBENTS. 393

but is made in the very mouth of the la&eals, as
was before explained.

5, When chyle, milk, or other extraneous fluids
are found in the urinary bladder, or in any other
excretory receptacle of a gland ; no one can for a
moment believe, that theie have have been collect-
ed from the mafs of blood by a morbid fecretion,
as ii: contradicts all analogy.

. Aurea chirse

Mala ferant quercus ? NarcifTo floreat alnus ?
Pin^uia corticibus fudent eie&ra myricae?

VlRGIl.

IX. Retrograde Motions of Vegetable "Juices.

THERE are befides fome motions of the fap in ve-
getables, which bear analogy to our prefent fubjecl: ;
and as the vegetable tribes are by many philofophers
held to be inferior animals, it may be a matter of
curiofity at leaf! to obferve, that their abforbent
veflels feem evidently, at times, to be capable of a
retrograde motion. Mr. Perault vcut off a forked
branch of a tree, with the leaves on; and invert-
ing one of the forks into a veffel of water, obferved
that the leaves on the other branch continued green
much longer than thofe of a iimilar branch, cut off
from the fame tree ; which fhews, that the water
from the vefiel was carried up one part of the fork-
ed branch, by the retrograde motion of its veffels,
and fupplied nutriment fome time to the other part
of the branch, which was out of the water. And
the celebrated Dr. Hales found, by numerous very
accurate expeiiments, that the fap of trees rofe up-
wards during the warmer hours of the day, and in
part defcended again during the cooler ones. Ve-
getable Statics.

It

394. RETROGRADE ABSORBENTS. SECT. XXIX. id'*

It is well known that the branches of willows,1
and of many other trees, will either take root in
the earth or engraft on other trees, fo as to have
their natural direction inverted, and yet flourim wittr
vigour".

Dr Hope has alfd made this pleating experiment,
after the manner of Hales — he has placed a forked
branch, cut from one tree, erecl: between two'
others ; then cutting off a part of the bark from
one fork applied it to a iimilar branch of one of
the trees in its vicinity j and the fame of the other
fork 5 fo that a tree is feen to grow fufpended in the
air, between two other trees ; which fupply the&
fofter friend with due nourifhment.

Jlirariturque novas frondes, et non fua poma.

All thefe experiments clearly evince, that the
juices of vegetables can occafionally pafs either up-
wards or downwards in their abforbeut fyflem of
vefTels.

X. Objections anfwered.

THE following experiment, at firft view, would
feem to invalidate this opinion of the retrograde'
motions of the lymphatic veifels, in fome difeafes.

About a gallon of milk having been given to an
hungry fwirie, he was fuffered to live about an hour,
and was then killed by a flroke or two on his head
•with an axe. — On opening his belly the ladeals were
well feeri filled with chyle ; on irritating many of
the branches of them with a: knife, they did not ap-
pear to empty themfelves haftily ; but they did
however carry forwards their contents in a little
time.

1 then

SECT XXIX. 10. RETROGRADE ABSORBENTS. 595

I then patted a ligature round feveral branches
Of lacteals, aaJ inhaled tne n much with a knife
beneatn the ligature, but could not make them re-
gurgitate their contained tiuiJ in o tne boweis.

I am not in JeeJ certain, that the nerve was not
at the fame time included in the ligature, and thus
the lymphatic rendered unirritable or iifelefs ; but
this however is certain, that it i> n >t any quantity
of any ilimulus, Which induces the veflels of animal
bodies to revert their motions ; but a certain quan-
tity of a certain itimulus, as appears from wounds
in tlie ftomach, which do not produce vomiting 5
and wounds' of the inteftines, which do not produce
the cholera morbus.

At Nottingham, a few years ago, two fhoem\ke*-$
quarrelled, and one of them with a knife, which
they ufe in their occupation, dabbed his companion
about the region of the ftomach. On opening the
abdomen of the wounded man after his death, the
food and medicines he had taken were in part
found in the cavity of the belly, on the outride of
the bowels ; and there was a wound about half ari
inch long at the bottom of the ftomach ; which I
fuppofe was diftended with liquor and food at the
time of the accident ; and thence was more liable
to be injured at its bottom : but during the whole
time he lived, which was about ten days, he had no
efforts to vomit, nor ever even complained of being
fick at the ftomach I Other cafes umitar to this are
mentioned in the philofophical tranfadlions.

Thus, if you vellicate the throat with a feather,
naufea is produced \ if you wound it with a pen-
knife, pain is induced, but not iicknefs. So it the
foles of the feet of children or their armpits are
tickled, oonvulfive laughter is excited, which ceafes
the moment the hand is applied, fo as to rub them
more forcibly,

Dd The

39* RETROGRADE ABSORBENTS. SECT. XXIX. rr,

The experiment therefore above related upon the
la&eals of a dead pig, which were included in a
ftritSt ligature, proves nothing ; as it is not the quan-
tity, but the kind of ftimulus, which excites the
lymphatic veflels into retrograde motion.

XI. The Caufes which induce the retrograde Motions of
animal Vejjels; and the Medicines by which the natu-
ral Motions are rejlored.

1. SUCH is the conftru&ion of animal bodies,
that all their parts, which are fubjecled to lefs ft i-
muH than nature deligned, perform their functions
with lefs accuracy : thus, when too watery or too
acefcent food is taken into the ftomacb, indigeftion,
and flatulency, and heart-burn fucceed.

2. Another law of iiritation, connate with our
exiftence, is, that all thofe parts of the body, which
have previoufly been expofed to too great a quantity
of fuch ftimuli, as ftrongly affe<St them, become for
fome time afterwards difobedient to the natural
quantity of their adapted ftimuti. — Thus the eye is
incapable of feeing objecls in an obfcure room,
though the iris is quite dilated, after having been
Expofed to the meridian fun.

3. There is a third law of iiritation, that all the
parts of our bodies, which have been lately fabject-
cd to lefs ftimulus, than they have been accuftomed
to* when they are expofed to their ufual quantity of
ftimulus, are excited into more energetic motions :
thus when we come from a dufky cavern into the
glare of daylight, our eyes are dazzled ; and after
emerging from the cold bath, the fldn becomes warm
and red -

4. There is a fourth law of irritation, that all
the parts of our bodies, which are fubje&ed to ftill
Wronger ftimuli for a length of time, become tor*

and refufe co obey even thefe ftronger ftimuli ;

and

S»CT. XXIX. ii. RETROGRADE ABSORBENTS, 397

.

and thence do their offices very imperfectly. — Thus,
if any one looks earneftly for fome minutes on an
area, an inch diameter^ of red iilk, placed on a
fheet of white paper, the image of the lilk will gra-
dually become pale, and at length totally vanifh.

5. Nor is it the nerves of fenfe alone,as the optic
and auditory nerves, that thus become torpid, when
the ftimulus is withdrawn or their irritability de-
creafed ; but the motive mufcles, When they are de-
prived of their natural ftimuli, or of their irritabi-
lity, become torpid and paralytic ; as is feen in the
tremulous hand of the drunkard in a mo'rning j and
in the awkward ftep of afge;

The hollow mufcles alfo, of which the various
veflels of the body are conftrudled, when they are
deprived of their natural ftimuli, or of their due de-
gree of irritability, not only become tremulous, as
the arterial pulfations of dying people j but alfo
frequently invert their motions, as in vomiting, in
hyfteric fuffocations, ami diabetes above defcribed.

I muft beg your patient atteritiofk, for a few mo-
ments, whilft I endeavour to explain how the retro-
grade actions cf our hollow mufcles are the
confequence of their debility ; as the tremulous
actions of the folid mufcles are the confe-
quence of their debility. When, through fatigue,
a mufcle can act no longer, the antagonilt mufcles,
either by their inanimate elafticity, or by their ani-
mal action, draw the limb into a contrary direction :
in the folid mufcles, as thofe of locomotion, their
aftions are aflbciated in tribes, which have been ac-
cuftomed to fynchronous action only ; hence when
they are fatigued, only a fmgle contrary effort takes
place ; which is either tremulous, when the fatigued
mufcles are again immediately brought into action ;
or it is a pandiculation, or ft retching, .where they
are not immediately again brought into adiion.

Now the motions of the hollow mufcles, as they
in general propel a fluid along their cavities, are af-

P 2 fociated

RETROGRADE ABSORBENTS. SECT. XXIX. n.

fociated in trains, which have been accuftomed to
fucceflive afrions : hence when one ring of, fiich a
mufcle is fatigued from its too great debility, and is
brought into retrograde adion, the next ring from
its affociation falls fucceflively into retrograde action,
and fo on throughout the whole canal. See Sect.
XXV. 6.

6. But as the retrograde motions of the ftomach,
cefophagus, and fauces in vomiting are, as it were,
apparent to the eye ; we mail coniider this opera-
tion more minutely, that the fimilar operations in
the more recondite parts of our fyftem may be eafier
underftood

From certain naufeous ideas of the mind, from
an ungrateful tafle in the mouth, or from foetid
fmells, vomiting is fometimes inflantly excited ; or
even from a ftroke on the head, or from the vibrato*
ry motions of a fhip ; all which originate from afib-
ciation, or. fympathy. See Seel. XX. on Vertigo.

But when the ftomach is fubjected to a lefs ftimu-
lus than is natural, according to the firft law of
irritation mentioned above, its motions become clif-
turbed, as in hunger ; firft pain is produced, then
fickoefs, and at length vain efforts to vomit, as many
authors inform us.

But when, a great quantity of wine, or of opium,
is fw allowed, the retrograde motions of the ftomach
do not occur till after federal minutes, or even
hours ; for when the power of fo ftrong a ftimulus
ceafes, according to the fecond law of irritation,
mentioned above, the periftahic motions become tre-
mulous, and at length retrograde ; as is well known
to the drunkard, who. on the next morning has fick-
nefs and vomitings.

When a ftill greater quantity of wine, or or opium,
or when naufeous vegetables, or ftrong bitters, or
metallic falts, are taken into the ftomach, they
qaickly induce vomiting ; though all thefe in lefs

dofes

SKCT. XXIX. M, RETROGRADE ABSORBENTS. 399

dofes excite the ftomach into more energetic adion
and ftrengthen the digeftion; as the flowers of cha-
momile, and the vitriol of zinc : for, according to
the fourth law of irrita ion, the ftomach will not
long be obedient to a. Hiinulus fo much greater than
ii natural ; but its action becomes firft tiemulous and
then retrograde.

7. When the motions of any vcflels become re-
trograde, lefs heat of the body is produced ; for in
paroxyfms of vomiting, of hyfteric affections, of di-
abetes, of afthma, the 'extremities of the body are
cold ; hence we may conclude, that thefe fymptoms
arifc from the debility of the parts in action ; for an
increafe of mufcular action is always attended with
mcreafe of heat.

8. But as animal debility is owing to defect of (U-
fnulus, or to defect of irritability, as (hewn above,
the method of cure is eaiily deduced : when the
vafcular mufcles are not excited into their due acti-
on by the natural ftimuli, we (hould exhibit thofe
medicines, which po fiefs a ft ill greater degree of
ftimulus ; amongft thefe are the feet ids, the vola-
tiles, aromatics, bitters, metallic falts, opiates, wine,
which indeed fhould be given in final I dofes, and
frequently repeated. To thefe fhould be added
conliant, but moderate exercife, cheerfulnefs of
mind, and change of country to a warmer climate ;
and perhaps occasionally the external ftimulus of
blifters.

It is alfo frequently ufeful to diminifh the quan-
tity of natural ftimulus for a (hort time, by which
afterwards the irritability of the fyftem becomes in-
ctealed ; according to the third law of irritation
above-mentioned, hence the ufe of baths fomewhat
colder than, annual heat, and of equitation in the
open air. *

The

RJ/TROGRApE ABSORBENTS. SECT. XX IX-

X&£ catalogue of difeafes owing to the retrograde moti-

' ons of lymphatics is ^here omitted s as it will appear

3% the -fecond 'volume of this work. The following

is the conclujton to this thejis of Mr. CHARLKS

DARWIN. -

THUS have J endeavoured in a concife manner
to explain the numerous difeafes, wtich deduce
their origin from the inverted motions of the hollow
mufcles of our bodies ; and it is probable, that Saint
Vitus's dance, arid the ftammering of fpeech, brigi-
Bate from a fimilar inverted order of the 'aflbciatcd
motions of foirie of the folid mufcles; which, as it
is foreign to my ptefent purpofe, I Ihall not here
dilcuJs. •

1 beg, illuftrious profejOfors, and ingenious fellow-
ilueents, that you will recollect flow difficult a taflt
I have attempted, to evince the retrograde motions
of the lymphatic veffels, wfren the veffels tlienlfelvei
for fo many ages escaped the eyes' and glafles of phi-
lofophers : and if you are not yet convinced of thd
truth of this theory, hold, I entreat you, yoiir minds
in fufpenfe, lill ANATOMY draws her fword witK
jhappier omens, cuts afunder the knots which entan-
gle PHYSIOLOGY ; amd, like an augur Irifpeding the
immolated vi&im, announces to mankind the wifdoiii
bf HJEAVEI4.

Sacx. XXX. i* PARALYSIS OF THE LlVEJl. 4*1

SECT. XXX.

PARALYSIS OF THE £1VER AND

I- Bile-dufts lefs irritable' after having been Jlhnulated
muck. 2. Jaundice from paralyfis of tty bile-dufts
cur id by eleclric Jhocks. 3. From bile-ftones. Ex-
periments on bile-ftones. Oil vomit. 4. Palfy of
the liver, two caufes. 5. Schirrofity of the liver.
6. Large livers of geefe. IL '"aralyfis of the kid*
neys. III. Story of Prometheus*

i. FROM the ingurgitation of fpirituous liquors
into the ftomach and duodenum, the termination
of the common bile-dudt in that bowel becomes
Simulated into unnatural a&ion, and a greater quan-
tity of bile is produced from all the Decretory yeflels
of the liver, by the affociation of their nootions wkh
thole of their excretory du6b ; as has t^een explain-
ed in Sedion XXIV. and XXV. but as all parts of
the body, that have been aiFe&ed with ftronger (ti-
muli for any length of time, become lefs fufceptible
of motion, from their natural weaker ftimuli, it fol-
lows, that the motions of the fecretory veffeis, and
in confequence the fecretion of bile, is lefs than is
natural during the intervals of fobriety. 2. If this
ingurgitation of fpirituous liquors has been daily con-
tinued in confiderable quantity, and is then fud-
denly intermitted, a languor or paralyfis of the
common bile-duel is induced ; the bile is prevented
from being poured into the inteftines ; and as the
bilious abfprbents are ftimulated into ftronger adion
by its accumulation, and by the acrimqny pr vifci-
dity, which it acquires by delay, it is abforbed, and

carried

PARALYSIS OF THE LIVER. SECT. XXX.

parried to the receptacle of the chyle ; or ptherwife
the fecretory veffels of the liver, by the above-men-
tioned Jlimulus, invert their motions, and regurgi-
tate their contents into the blood, as fometime?
happens to the tears in the lachrymal fack;, fee Sed.
XXIV. 2. 7. and one kind of jaundice is brought on.

There js reafon to believe, that the bile is moft
tfr.equent.lv returned into the circulation by the in<-
verted motions of thefe hepatic glands, for the bile
does not feem liable 10 be abforbed by the lympha?
tics, for it fpaks through the gall-dufts, and is frer
quently found in the cellular membrane. This kincj
of jaundice is not generally attended with pain, nei-
ther at the extremity of the bile-duel:, where it
(enters the duodenum, nor on the region of th§
gall-bladder^.

Mr. S. a gentleman between 40 and 50 years of
age, had Had the jaundice about fix weeks, without
pain, iicknefs, or fever ; and had taken emetics, ca*
thartics, mercurials, bitters, chalybeates, eflentiaj
oil, and aether, without apparent advantage. On 9.
fuppolnion that the oburucltion of the bile might
Tpe owing to the paralyfis, or tprpid aclion of the
common bile-duel:, and the ft}mulants taken into
the ftomach feeming to have no efFed, 1 defired
half a fcqre fmart electric (hocks from a coated bot-
tle, which held about a fjuart, to be paffed through
the liver, and along the cpurfe of the common gall*
du(S? as nea/ as could be gueffed, and on that very
day the ftools became yellow ; he continued the elec-
trie fhocks a few days more, and hi§ fldn gradually
Became clear.

3. The bilious vomiting and purging, that affedls
fome people by intervals of a few weeks, is a lefs
degree of this difeafe ; the bile dud is lefs irritable
than natural, and hence the bile becomes accumu-
lated in the gall-bladder, and hepatic dufts, till by
its quantity, acrimony or vifcidity, a greater degree
of irritation is prgduced, and it is fuddenly evacu-
ated

SECT. XXX. i. PARALYSIS OF THE LIVER. 4oj

ated, or laftly from the abforption of the more
liquid parts of the bile, the remainder becomes in-
fpitfated, and cryiiailizes into piaffes too large to
J>afs, and forms another kind of jaundice, where
the bile-du& is not quite paralytic, or has, regained
its irritability.

This difeafe is attended with much pain, which
at firlt is felt at the pit of the ilomach, exactly ia
the centre of the body, where the bile-duel: enters
the duodenum ; afterwards, when the fize of the
fcile^flones increafe, it is alfo felt on the right fide,
where the gall-bladder is fituated. The former pain
at the pit of the flomach recurs by intervals, as the
bile-Hone is puttied againft the neck of the duct ;
like the paroxyfrns of the flone in the urinary blad-
der, the other is a more dull and conftant pain.

Where thefe bile-ilones are too large to pafs, and
the bile-dudis poffefs their fenfibility, this becomes
a very painful and hopelefs difeafe. I made the fol-
lowing experiments with a view to their chemical
folution. '

Some fragments of the Tame bile-ftone were put
pto the weak fpirit of marine fait, which is fold in
the (hops, and into folution of mild alcali; and into
a foluiion of cauftic alcali ; and into oil of turpen-
tine; without their being diflblved. All thefe mix-
tures were after fome time put into a heat of boil-
ing Water, and then the oil of turpentine diflblved
its fragment? of bile-ltone, but no alteration was
produced upon thofe in the other liquids except
Jo me change of their colour.

Some fragments of the fame bile-done were put
into vitriolic ssther, and were quickly diffolved with-
out additional heat. Might not aether mixed with
yolk of egg or with honey be given advantageoufir
in bilious concretions ?

I have in two inftances feen from 30 to 50 bile-
ilones come away by llool, about the iize of large

peas

404 PARALYSIS OF THE LIVER. SECT. XXX. r.

peas, after having given fix grains of calomel in the
evening, and four ounces of oil of almonds or olives
on the fucceeding morning. I have alfo given half
a pint of good olive or almond oil as an emetic
during the painful fit, and repeated it in half an
hour, if the firft clid not operate, with frequent good
cffea.

4. Another difeafe of the liver, which I have
feveral times obferved, confifts in the inability or
paralyfis of the fecretory .veifels. This aifeafe has
generally the fame eaufe as the preceding one, the
too frequent potation of fpirituous liquors, or the
too fudden omiflion of them, after the habit is con-
firmed ; as is greater or lefs in proportion, as the
whole or a part of the liver is affected, and as the
inability or paralyfis u more or lefs complete.

This palfy of the liver is known from thefe fymp-
torm, the patients have generally pafled the meridian
of life, have drank fermented liquors daily, but
perhaps not been opprobrious drunkards ; they lofe
their appetite, then their flefh and ftrength dimi-
nifh in confequence, there appears no bile in their
flools, nor in their urine, nor is any hardnefs or
fwelling perceptible on the region of the liver. But
•what is peculiar to this difeafe, and diftinguifhes it
from all others at the firft glance of the eye, is the
bombycinous colour of the {kin, which, like that
of full-grown iilkworms, has a degree of tranfpa-
rency with a yellow tint not greater than is natural
to the ferum of the blood.

Mr. C. and Mr. B. both very ftrong men, be-
tween 50 and 60 years of ige, who had drank ale
at their meals inftead of fmail beer, but were not
reputed hard drinkers, fuddenly became weak, loft
their appetite, flefh and fbength, with all the fymp-
toms above enumerated, and died in about two
months from the beginning of their malady. Mr.
C. became anaiarcous a few days before his death,

and.

SECT. XXX. i. PARALYSIS OF THE LIVER.

and Mr. B. had frequent and great haemorrhages
from an iflue and fome parts of his mouth, a few
days before his death. In both thefe cafes calomel,
bitters and chalybeates were repeatedly ufed with-
out effecl. '

One of the patients defcribed above, Mr. G. was
by trade a plumber ; both of them could digeft no
food, and died apparently for want of blood. Might
not the transfufion of blood be ufed in thefe cafes
with advantage ?

5. When the paralyfis of the hepatic glands is
Jefs complete, or lefs univerfal, a fchirrofity of fome
part of the liver is induced ; for the fecretory vef-
fels retaining fome of their living power take up a
fluid from the circulation, without being fufficiently
irritable to cany it forwards to their excretory duds;
hence the body, or receptacle of each gland, be-
comes inflated, and this diftenfion increafes, till, by
its very great ftimulus inflammation is produced, or
till thofe parts of the vifcus become totally paraly-
tic. This difeafe is diftinguifhable from the fore-
going by the palpable hardnefs or largenefs of the
liver; and as the hepatic glands are not totally para-
lytic, or the whole liver not atfec"led, fome bile con-
tinues to be made. The inflammations of this
vifcus, confequent to the fchirrofity of it, belong to
the difeafes of the fenfuive motions, and will be
treated of hereafter.

6. The ancients are faid to have poffefled an art
of increafing the livers of geefe to a fize greater
'than the remainder of the goofe. Martial. 1. 13.

epig. 58. — This is faid to have been done by fat and
fig*. Horace, 1. 2. fat. 8.— Juvenal fets thefe large
Jivers before an epicure as a great rarity. Sat. 5. 1.
114; and Perfius, "fat. 6. 1.71. Pliny fays thefe
large goofe-livers'were foaked in mulled milk, that
is, I fappofe, milk mixed with honey and wine ; and
"adds, <c that it is uncertain whether Scipio Metellus,

of

4o6 PARALYSIS OF THE LIVER. SECT. XXX a.

of corifular dignity, or M. Seftius, a Roman knight,
was the great difcoverec of this excellent dim." A
modern traveller, I believe Mr. Brydone, afferts
that the art of enlarging the livers of geefe dill
exilis in Sicily ; and it is to be lamented that hedi^i
not import it into his native country, as fome me-
thod of affecting the human liver might perhaps
have been collected from it ; befides the honour he
might have acquired in improving our giblet pies.

Our wifer caupones, I am told, know how to fat-
ten their fowls, as well as their geefe, for the London
markets, by mixing gin inftead of figs and fat with
their food ; by which they are faid to become fleepy,
and to fatten apace, and probably acquire enlarged
livers ; as the fwine are arjerted to do, which are
fed on the fediments of barrels in the diftilleries ;
and which fo frequently obtains in thofe, who in-
gurgitate much, ale, or wine, or drams.

II. The irritative difeafes of the kidneys, pancreas,
fpleen, and other glands., are analogous to thofe of
the liver above defcribed, differing only in the con-
fequences attending their inability to action. For
inltance, when the' fecretpry veffels of the kidneys
become difobedient to the ftimulus of the palling
current of blood, no urine is feparated or produced
by them ; their excretory mouths become filled with
concreted mucus, or calculus matter, and in eight or
ten days, iluporand death intervenes in confequence
of the retention of the feculent part of the blood.

This difeafe in a fiighter degree., or when only a
part of the kidney is affected, is fucceeded by par-
tial inflammation of the kidney in confequence of
previous torpor. In that cafe greater actions of the
Decretory veffels occur, and the nucleus of gravel is.
formed by the inflamed muc6us membranes of the
tubuli uriniferi, as farther explained in its place.

This torpor or paralyfis of the fecretory vefTels
of the kidneys, like that of the liver, owes its origin

to

SJTCT. XXX. 3: PARALYSIS OF THE LIVER. 407

to their being previously habituated to too great fti-
mulus ; which in this country is generally owing to
the alcohol contained in ale or wine ; and hence
muft be regiftered amongft the difeafes owing to
inebriety; though it may be caufed by whatever
occasionally inflames the kidney ; as too vio-
lent riding on horfeback, or the cold from a damp
bed, or by flecping on the cold ground ; or
perhaps by drinking in general too little aqdeous
fluids.

JII. I fhall conclude this fe£tion on the difeafes
of the liver induced by fpirituous liquors, with the
well known llory of Prometheus, which feems in-
deed to have been invented by pbyiicians in thofe
ancient times, when all things were clothed in
hieroglyphic, or in fable. Prometheus was painted
as dealing fire from heaven, which might well re-
prefetit the inflammable fpirit produced by fermen-
tation ; which may be faid to animate or enliven
the man of clay : whence the conquefts of Bacchus,
as well as the temporary mirth and noife of his de-
votees. But the after punifhments of thofe, who
Heal this accurfed fire, is a vulture gnawing the li-
ver ; and well allcgoiifes the poor inebriate linger-
ing for years under painful hepatic difeafes. When
the expediency of laying a further tax on the dif-
tillation of fpirituous liquors from grain was can-
vafled befoie the Houfe of Commons fome years
ago, it was faid of the diftillers with great truth,
" They take the bread from the people, and convert it
into poifon!" Yet is this manuiadory of difeafe
permitted to continue, as appears by its paying into
the treafury above 9co,coo/. near a million of mo-
ney annually. And thus, under the names of rum,
brandy, gin, whifkey, ufquebaugh, wine, cyder,
beer, and porter, alcohol is become the bane

of

4o8 OF TEMPERAMENTS- SECT XXXL

of the Chriftian world, as opium of the Maho-
roetan.

Evoe ! parce, Liber *
Farce, gravi metucnde thyrfo i Hot.

SECT, xxxt

OF TEMPERAMENTS.

I, The temperament of decreafed irritability known Ij
weak pu/fe, large pupils of the eye, cold extremities*
Are generally fuppofed to be too irritable. Bear pain
better than labour. Natives of North-America con-
trajied with tbofe upon the coift of Africa. Narrow
and broad Jhouldeied people. Irritable conjlitutions
bear labour better than p tin. II. 'Temperament of
increafedfenfibility. Liable to intoxication^ to inflam-
nation, hamoptoe, guttaferena, enthujlafm^ delnium,
reverie. Thefe constitutions are indolent to voluntary
exertions, and dull to irritations. 7 he natives of
South- America, and brute animals of this tempera-
ment. III. Of increased voluntarily ; thefe arefub-
jecJ to locked jaw, convuljions^ epilepfy^ mania. Are
very aflive, bear cold, hunger, fatigue. Are fuitedto
great exertions. This temperament dijlinguifhes man-
kind from other animals. IV. Of incrcaftd ajjocia-
tion. Thefe have great memories, are liable to quar-
tan agues, and Jironger fympathies of parts with
each other. V. Change of temperaments into on*
another.

ANTIENT writers have fpoken much of tem-
peraments, but without fufficient precifion. By

temperament:

SECT. XXXI. i. OF TEMPERAMENTS.

temperament of the fyftem ihould be meant a per-
manent predifpofition to certain clafles of clifeafes :
without this definition a temporary predifpofition
to every diftinct malady might be termed a tempe-
rament. There are four kinds of constitution,
which permanently deviate from good health, aqd
are perhaps fufficiently marked to be diftinguimed
from each other, and conflitute the temperaments
or predifpolitions to the irritative, fenfitive, volun-
tary, and alfociate claffes of difeafes.

I. The Temperament of decreased Irritability.

THE difeafes which are caufed by irritation, molt
frequently originate from the defeclofit; for thofe
which are immediately owing to the excefs of it, as
the hot fits of fever, are generally occafioned by an
accumulation of fenforial power in confequence of
a previous defect of irritation, as in the preceding
cold fits of fever. Whereas the difeafes, which are
caufed by fenfation and volition, moil frequently
originate from the excefs of thofe cenforial powers,
as will be explained below.

The temperament of decreafed irritability appears
from the following circumftances, which fhew that
the mufcular fibres or organs 6f fenfe are liable to
become torpid or quiefcent from lefs defect of fti-
mulation than is productive of torpor or quiefcence
in oiher conftitutions.

I. The firft is the weak pulfe, which in fome
conftitutions is at the fame time quick. 2. The
next mofh marked criterion of this temperament is
the largenefs of the aperture of the iris, or pupil
of the eye, which has been reckoned by fome a
beautiful feature in the female countenance, as an
indication of delicacy, but to an experienced ob-
ferver it is an indication of debility, and is there-
fore

4f » OF TEMPERAMENTS. SECT. XXXI. *a

fore a defect, not an excellence. The third moflf
marked circumftance in this conftitution is, that the
extremities, as the hands and feet, or nofe and ears,
are liable to become cold and pale in fnuations in
refpedt to warmth, where thofe of greater ftrength
are not affected. Thofe of this temperament are
fubjed to hyfteric aftedions, nervous fevers, hy-
drocephalus, fcrophula, and confumption, and to
all -other difeafes of debility.

Thofe, who pofTefs this kind of conititution, are
popularly fuppofed to be more irritable than is na-
tural, but are in reality lefs fo. This rmftake has
arifen from their generally having a greater quick-
nefs of pulfe, as explained in Sed. XII. I. 4. XII.
3. 5. ; but this frequency of puife is not necelTary
to the temperament, like the debility of it.

Perfons of this temperament are frequently found
amongft the fofter fex, and amongft narrow-fhoul-
dered men; who are faid to bear labour worfe, and
pain better than others. This laft circumftance is
fuppofed to have prevented the natives of North
America from having been made flaves by the
Europeans. They are a narrow mouldered race of
people, and will rather expire under the lafh, than
be made to labour. Some nations of Aria have
fmall hands, as may be feen by the handles of their
fcymetars ; which with their narrow fhoulders fhew,
that they have not been accuftomed to fo great la-
bour with their hands and arms, as the European
nations in agriculture, and thofe on the coafts of
Africa in fwimming and rowing. Dr. Maningham,
a popular accoucheur in the beginning of this cen-
tury, obferves in his aphorifms, that broad moul-
dered men procreate broad fhouldered children.
Now as labour ftrengthens the mufcles employed,
and increafes their bulk, it would feem that a few
generations of labour or of indolence may in this

SECT. XXXI. *. OF TEMPERAMENTS.

refped change the form and temperament of the
body.

On the contrary, thofe who are happily poffeffed
6f a great degree of irritability, bear labour better
than pain ; and are ilrong, adtive, and ingenious.
But there is not properly a temperament of in-
creafed irritability .tending to difeafe, becaufe an in-
creafed quantity of irritative motions generally in-
duces an iucreafe of pieafure or pain, as in intoxi-
cation, or inflammation ; and then the new motions
are ihe immediate confequences of increafed fenfa-
tion, not of increafed irritation ; which have hence
been fo perpetually confounded with each other.

II. Temperament of Senjibilityi

THERE is not properly a temperament, or pre«r
difpofition to difeafe, from decreafed fenfibility,
fmce irritability and not fenfibility is immediately
necefTary to bodily health. Hence it is the excefs
of fenfation alone, as it is the defect of irritation,
that mod frequently produces difeafe. This tem-
perament of increafed fenfibility is known from the
increafed activity of all thofe motions of the organs
of fenfe and mufcles, which are exerted in confe-
quence of pieafure or pain, as in the beginning of
drunkennefs, and in inflammatory fever. Hence
thofe of this conftitution are liable to inflammatory
difeafes, as hepatitis, and to that kind of confump-
tion which is hereditary, and commences with flight
repeated hcemoptoe. They have high-coloured lips,'
frequently dark hair and dark eyes with large pu-
pils, and are in that cafe fubjedT to gutta ferena.
They are liable to enthufiafm, delirium, and reve-
rie. In this laft circumfiance they are liable to
ftart at the clapping of a door ; becaufe the more
intent any one is on the pafling current of his ideas,

E e the

4* » OF TEMPERAMENTS. S*CT. XXXf. *.

the greater furprife he experiences on their being
diffevered by fome external violence, as explained in
Seel, XIX. on reverie.

As in thefe conftitutions more than the natural
(jnantities of fenfitive motions are produced by the
irtcreafed quantity of fenfatiori exifting in the habit,
it follows, that the irritative motions will be per-
formed in fome degree with lefs energy, owing to
the great expenditure of fenforial' power on the fen-
fitive one?. Hence thofe of this temperament do
not attend to flight flimulatrons, as explained in
Sect. XIX. But when a ftimul'us is fo great as to
excite fenfatron, it produces greater fenfitive actions
of the fyftem than in others; fuch as delirium or
inflammation. Hence they are liable to be abfent
in company ; fit or He long in one pofture ; and in
winter have the fkin of their legs burnt into vari-
ous colours by the fire. Hence alfo they are fear-
ful of pain ; covet mufic and ileep ; and delight ia
poetry -and romance.

As the motions in confequence of fenfation arc
more than natural, it alfo happens from the greater
expenditure of fenforial power on them, that the
voluntary motions are lefs ealily exerted. Hence the
fubjecis of this temperament are indolent in refpecl:
to all voluntary exertions, whether of mind or body.

A race of people of this defcription feems to have
been found by the Spaniards in the iflands of Ame-
rica, where they firft landed, ten of whom are faid
not to have contained more food than one Spaniard,
nor to have been capable of more than one tenth
of the exertion of a Spaniard. Robertfon's Hifto-
fv.-— In ji Hate fimrlar to this the greateft part of
the animal world pafs their lives, between fleep or
inactive reverie, except when they are excited by

the call of hunger.

. "

*"j*&i •

III. The

S KCT. XXXI. 3. 4. OF TEMPERAMENTS. 413

III. The Temperament df mcreafid Voluntarily.

THOSE of this conflitutiori differ from both the
l<lft mentioned in this, that the pain, which gradu-
ally fubfides in the firft, and is productive of in-
flammation or delirium in the fecond, is in this fuc-
cceded by the exertion of the mufcles or ideas,
which are moil frequently connected with volition ;
and they are thence fubjecl to locked jaw, convul-
iions, epilepfy; and mania, as explained in Sect.
XXXIV. Thofe of this temperament attend to the
flighted: irritations or fenfations, and immediately
exert themfelves to obtain or avoid the objects of
them, they can at the fame time bear cold and
hunger better than others, of which Charles the
Twelfth of Sweden was an infiance. They are
fuited and generally prompted to all great exertions
of genius or labour, as their defires are more ex-
tenfive and more vehement, and their powers of
attention and of labour greater. It is this facility
of voluntary exertion, which diftinguifhes men from
brutes, and which has made them lords of the ere*
ation.

IV. The Temperament of increafed Affbciation.

THIS conftitution confifts in the too great faci-
lity, with which the fibrous motions acquire habits
of aflbciation, and by which thefe aflbciations be-
come proportionably ftronger than in thofe of the
other temperaments. Thofe of this temperament
are flow in voluntary exertions, or in thofe depend-
ent on fenfation, or on irritation. Hence great
memories have been faid to be attended with lefs
fenfe and lefs imagination from Ariftotle down to

E e 2 the

4H OF TEMPERAMENTS. SECT. XXXI. 5.

the prefent time ; for by the word memory thefe
writers only underftood the unmeaning repetition of
words or numbers in the order they were received,
without any voluntary efforts of the mind.

In this temperament thofe affeciations of motions,
which are commonly termed fympathies, aft with
greater certainty and energy, as thofe between dif-
turbed vifion and the inverfion of the motion of
the ftomach, as in fea-ficknefs ; and the pains in the
flioulder from hepatic inflammation. Add to this,
that the catenated circles of aclions are of greater
extent than in the other confutations. Thus if a
ft.rong vomit or cathartic be exhibited in this tem-
perament, a fmaller quantity will produce as great
an effect, if it be given fome weeks afterwards ;
whereas in other temperaments this is only to be
expeded, if it be exhibited in a few days after the
firft dofe. Hence quartan agues are formed in thofe
of this temperament, as explained in Se&ion XXXII .
on difeafes from irritation, and other intermittents
are liable to recur from flight caufes many weeks
after they have been cured by the bark.

V. The firft of thefe temperaments differs from
the ftandard of health from defect, and the others
from excefs of fenforial power; but it fometimes
happens that the fame individual, from the changes
introduced into his habit by the different feafons of
the year, modes or periods of life, or by accidental
difeafes, paries from one of thefe temperaments to
another. Thus a long ufe of too much fermented
liquor produces the temperament of increafed fenfl-
bility ; great indolence and folitude that of decreafed
irritability; and want of the neceflaries of life that
of inerealed voluntarily.

; «li :-

SECT.

SECT. XXXII. p, DISEASES OF IRRITATION. 415

SECT. XXXII.

DISEASES OF IRRITATION.

Irritative fevers with Jlrong pulfe. With weak pulfc.
Symptoms of fever. Their fource. II. I. 0(uick

pulfe is owing to decreased irritability. Z. Not in

Jleep or in apoplexy. 3. From inanition. Owing
to deficiency of fenforial power- III* I • Caufes of

fever. From defefi of heat. Heat from fecretions.
Pain of cold in the loins and forehead, z. Great ex-

pmfe of fenforial power in the vital motions. Im-
merjion in cold water. Succeeding glow of heat.
Difficult refpiration in cold lathing explained. Why
the cold bath invigorates. Bracing and relaxation
are mechanical terms. 3. Ufes of cold bathing. Ufes
of cold air in fevers. 4. Ague jits from cold air.
Whence their periodical returns. IV. Defect of dif-
tention a caufe of fe<ver. Deficiency of blood. Trans-
fufion of blood. V. I. Defecl of momentum of the
blood from mechanic Jlimuli. 2. Air injected into,
the blood 'veffels. 3. Exercife increases the momentum
of the blood. 4. Sometimes bleeding increafes the
momentum of it. VI. Influence of the fun and moon
on difeafes. The chemical Jlimulus of the blood,
Menjiruation obeys the lunations. Queries. VII.
Quiefcence of large glands a caufe of fever. Swell-
ing of the prcecordia. VIII. Other caufes of qui-
efcence, as hunger, bad air , fear, anxiety. IX. I.
Symptoms of the, cold ft, ^. Of the hot ft. 3.
Second cold ft why. 4. Inflammation iniroditced*
or delirium, or Ji up or. X. Recapitulation. Fever

not

DISEASES OF IRRITATION. SHOT. XXXII. r.

not an effort of nature to relieve her f elf. Doftrinq
cffpafm.

I. WHEN the contra&ile iides of the heart anc}
arteries perform a greater number pf pulfations in
a given time, and move through a greater area at
each pulfation, whether thefe motions are occafion-
ed by the ftimulus of the acrimony or quantity of
the blood, or by their affociation with other irri-
tative motions, or by the increafed irritability of the
Arterial fyftem, that is, by an increafed quantity
of fenforial power, one kind of fever is produced ;
which may be called Synocha irritativa, or Febris
irritativa pulfu forti, or irritative fever with ftrong
pulfe.

When the contra&ile fides of the heart and arte-
ries perform a greater number of pulfations in 4
given time, but move through a much lefs area at
each pulfation, whether thefe motions are occa-
iioned by defect of their natural ftimuli, or by
the defect of other irritative motions with which
they are aflbciated, or from the inirritability of the
* arterial fyftem, that is, from a decreafed quantity
of fenforial power, another kind of fever arifes ;
which may be termed, Typhus irritativus, or Fe-
bris irritativa pulfu debili, or irritative fever with
weak pulfe. The former of thefe fevers is the
fynocha of nofologifts, and the latter the typhus
miticr, or nervous fever. In the former there ap-
pears to be an increafe of fenforial power, in the
latter a deficiency of it ; which is (hewn to be the
immediate caufe of flrength and weaknefs, as de-
fined in Sea. XII. 1.3.

It fliould be added, that a temporary quantity of
ftrength or debility may be induced by the defect
or excefs of fHmulus above what is natural ; and
that in the fame fever debility always exifts during the

cold

&SCT. XXXII. 2. DISEASES OF IRRITATI JN. 41

.cold ft, though Jlrcngtli does not always exijl during
the hot fit.

Thefe fevers arc always connected with, and ge-
nerally induced by, ihc disordered irritative motions .
of the organs of icnfe, or of the imedinal canal, or
of the glandular 1} item, or of the abforbent fyf-
tem ; and hence are always complicated with fome
or many of thefe difordered motions, which are
termed the fymptoms of the fever, and which com-
pofe the great variety in thefe difeafcs.

The irritative fevers both with flrong and with
xvcak pulfe, as well as the fcrifitive fevers with ilrong
and with weak pulfe, which are to be defcribed in
the next fe&ion, are liable to periodical remiflions,
and then they take the name of intermittent fevers,
and are diilinguifhed by the periodical times of
fjigir accefs.

II. For the better illuflration of the phenomena
of irritative fevers we mufl refer the reader to the
circumflances of irritation explained in'Sect. XII.
and mall .commence this intricate fubjcct by f peak-
ing of the quick pulfe, and proceed by confider-
ing ingny of the caufes, which either feparately or
in combination moll frequently produce the cold
fits pf fevers.

i. If the arteries are dilated but to half their
ufual diameters, though they contract twice as fre-
quently in a given time, they will circulate only
'half their ufual quantity of blood : for as they arc
cylinders, the blood which they contain mufl be
as the fquares of their diaaieters. Hence when the
pulfe becomes quicker and fiiialler in the fame-
proportion, the heart and arteries a6t with Ids ener-
gy than in their natural flatc. See Seel. XII. i. 4.

That this quick fmall pulfe is owing to want cf
irritability, appears, firft, bccaufc it attends other
fymptoms of want of irritability ; and, fecondiy,
becaufc on the application of a flimulas gica'e,*

than

4iS DISEASES OF IRRITATION. SECT, XXXII. a.

s?

than ufual, it becomes flower and larger. Thus
;in cold fits of agues, in hyfteric palpitations of the
heart, and when the body is much exhaufted J)jr
haemorrhages, or by fatigue, as well as in nervous
fevers, the pulfe becomes quick and fmall ; and,
fecondly, in all thofe cafes if an increafe of ftimu-
lus be added, by giving a little wine or opium ;
the quick fmall pulfe becomes flower and larger,
as any one may eafily experience on himfelf, by
counting his pulfe afterdrinking one or two glafles
of wine, when he is faint from hunger or fatigue.

'Now nothing can fo ftrongly evince that this
quick fmall pulfe is pwing to defect of irritability^
than that an additional ftimulus, above what is
natural, makes it become flower and larger immedi-
ately : for what Js meant by a defect of irritability,
but that thje arteries and heart are not excited jnto
their ufual exertions by their ufual quantity of
ftimulus?.but if you increafe the quantity of fti-
inulus, and they immediately act with their ufual
energy, this proves their previous want of their
natural degree of irritability. TJjus the trembling
hands of drunkards in a morning become fleady,
and acquire flrength to perform their ufuaj offices,
by the accuftomed ftimulus of a glafs or two of
Brandy.

2. In fleep and in apoplexy the pulfe becomes
flower, which is not owing to defect of irritability,
jfor it is at the fame time larger ; and thence the
quantity of tjie circulation is rather increafecj than
diminifjked. In thefe cafes the organ's of ferife are
clofecj, and the voluntary power is fufpended, while
the motions dependent on internal' irritations, as
thofe of digeftion and fecretion, are carried on with
more than their ufual vigour ; which has led fuper-
ficial obfervers to confound thefe cafes with thofe
ariiing ifrom want of irritability. Thus if you lift
up the eyelid of an apoplectic patient, who is not

SECT. XXXII. 2. DISEASES OF IRRITATION. 419

^dually dying, the iris will, as ufual, contract it-
felf, as this motion is affociated with the ftimulus
of light ; {nit it is not fo in the laft ftages of ner-
vous fevers, where the pupil of the eye continues
expanded in the broad day-light: in the former
cafe there is, a want of voluntary power, in the lat-
ter a want of irritability.

Hence alfo thofe conftitutions which are deficient
in quantity of irritability, and which poflefs too
great feniibility, as during the pain of hunger, of
hyfteric fpafms, or nervous headachs, are generally
fuppofed to have too much irritability ; and opium,
which in its due dofe is a moft powerful flimulant,
is erroneoufly called a fedative ; becaufe by increaf-
ing the irritative motions it decreafes the pains arif-
ing from defect of them,

Why the pulfe fhould become quicker both from
an increafe of irritation, as in the fynocha irritativa,
or irritative fever with ftrong pulfe; and from the
decreafe of it, as in the typhus irritativus, or irri-
tative fever with weak pulfe ; feems paradoxical.
The former circumftance needs no illuftration ;
fmce if the ftimulus of the blood, or the irritability
of the fanguiferous fyftem be increafed, and the
Strength of the patient not diminifhed, it is plain
that the motions nmfl be performed quicker and

In the latter circumtfance the weaknefs of the
mufcular power of the heart is foon overbalanced
by the elafticity of the coats of the arteries, which
they poffefs befides a mufcular power of contra6H-
bn ; and hence the arteries are diftended to lefs
than their ufual diameters. The heart being thus
flopped, when it is but half emptied, begins fooner
to dilate again ; and the arteries being dilated to
lefs than their ufual diameters, begin fo much
fooner to contract themfelves ; infomuch, that in the
dagcs of fevers with weaknefs the frequency of

pulfation

420 DISEASES OF IRRITATION, SECT. XXXII, 3.

pulfation of the heart and arteries becomes doubled;
which, however, is never the cafe, in fevers with
ftrength, in which they feldom exceed 118 or 120
pulfations in a minute. It mufl be added, that in
thefe cafes, while the pulfe is very fmall anid very
quick, the heart often feels large, and labouring to
one's hand ; which coincides with the above expla-
nation, (hewing that it does no,t completely empty
itfelf.

3. In cafes however of debility from paucity of
blood, as in animals which are bleeding to death
in the fiaughter-houfe, the quick pulfations of the
heart and arteries may be owing to their not being
diftended to more than half their ufoal diaftole ;
and in confequence they njuft contract fooner, or
more frequently, in a given tiifle.. As weak people
are liable to a deficient quantity of blood, this
caufe may occalionally contribute to quicken the
pulfe in fevers with debility, which may be known
by applying one's hand upon the heart as above ;
but the principal caufe I fuppofe to confift in the
diminution of fenforial power. When a mufcle
contains, or is fupplied with but little fenforia^
power, its contraction foon ceafes, and in confe-
quence may foon reftir, as is feen in the trernbling
hands of people weakened by age or by ch'Uflken-
nefs. See Sea. XII. i. 4. XII. 3. 4.

It may neverihelefs frequently happen, that both
the deficiency of ilimulus, as where the quantity
of blood is leflened (as defcribed in No. 4. of this
fe6tion), and the deficiency of fenforial power, as
in thofe of the temperament of inirritability, de-
icribed in Se6l. XXXI. occur at the fame time j
which will thus add to the quicknefs of the pulfe
and to the danger of the difeafe.

III. i. A certain degree of heat is ncceffary to
mufcular motion, and is, in confequence, effential
to life. This is obferved in thofe animals and infec~h

which

SECT. XX&II. 3. DISEASES OF IRRITATION. 4sj

V/hich pafs the cold feafon in a torpid flatc, and
which revive on being warmed by the fire. This
.neceffary ftimulus of heat has two Iburces ; one from
the fluid atmofphere of heat, in which all things
are immerfed, and the other from the internal com-
binations of the panicles, which form the various
fluids, which are produced in the extenfive fyftems
of the glands. When either the external heat,
which furrounds us, or the internal production of
it, becomes lefTened to a certain degree, the pain of
cold is perceived.

This pain of cold is experienced mod fenfibly by
pur teeth, when ice is held in the mouth ; or by
our whole fyftem after having been previoufly ac-
cuftomed to much warmth. It is probable, that this
pain does not arife from the mechanical or chemi-
cal effects of a deficiency of heat ; but that, like
the organs of fenfe by which we perceive hunger
and thiift, this fenfe of heat fuffers pain, when the
flimulus of its object is wanting to excite the irri-
tative motions of the organ ; that is, when the fen-
forial power becomes too much accumulated in the
quiefcent fibres. See Sect. XII. 5. 3. For as the
periilaltic motions of the flomach are leflened, when
the pain of hunger is great, fo the action of the
cutaneous capillaries are leflened during the pain of
cold ; as appears by the palenefs of the fkin, as ex-
plained in Sect. XIV. 6. on the production of ideas.

The pain in the fmall of the back and forehead in
the cold fits of the ague, in nervous hemicrania,
and in hyfteric paroxyims, when all the irritative
motions are much impaired, feems 10 arife from this
caufe ; the veflels of thefe membranes or mufcles
become torpid by their irritative affociations with
other parts of the body, and thence produce lefs of
their accullomed fecretions, and in confequence lefs
heat is evolved., and they experience the pain oi"

cold

DISEASES OF IRRITATION. SEcr.^CXXII. 3.

cold ; which coldnefs may often be felt by the hand
applied upon the affecled part.

2. The importance of a greater or lefs deduction
of heat from the fyftem will be more eafy to compre-
hend,! if we fir ft 'coniider the great expenfe of fen-
forial power ufed in carrying on the vital motions ;
that is, which circulates, abforbs, fecretes, aerates,
and elaborates .the whole mafs of fluids with un-
ceafing afljduity. The fenforial power, or fpirit of
animation, ufed in giving perpetual and ftrong mo-
tion to the heart, which overcomes the elafticity and
vis inertise of the whole arterial fyftem ; next the
expenfe of fenforial power in moving with great
force and velocity the innumerable trunks and ra-
mifications of the arterial fyftem ; the expenfe of
fenforial power in circulating the whole mafs of
blood through the long and intricate intortions of
the very fine veflels, which compofe the glands and
capillaries; then the expenfe of fenforial power in
the exertions of the abforbent extremities of all
the lafteals, arid of all the lymphatics, which open
their mouths on the external furface of the fkin,
and on the internal furfaces of every cell or inter-
ftice of the body ; then the expenfe of fenforia,!
power in the venous abforption, by which the blood
is received from the papillary vefTels, or glands?
where the arterial power ceafes, and is drank up,
and returned to the heart ; nexphe expenfe of fen-
forial power ufed by the mufclejj of refpiration in
their office of perpetually expanding the bronchia, or
air-vefleis, of the lungs ; and laftly in thevunceafing
periftaltic motions of the ilomach and whole fyftem
of inteitines, and in all the fecretions of bile, gaf-
tric juice, mucus, perfpirable matter, and the vari-
ous excretions from the lyliem. It" we coniider
the ceafeleis expenfe of fenforial power thus perpe-
tually employed, it will appear to be much greater
in a day than all the voluntary exertions of our

mufcles.

SECT. XXXII. 3. DISEASES OF IRRITATION. 425

mufcles and organs of fenfe1 confume in a week ;
and all this without any fenfible fatigue ! Now, it"
but a part of thele vital motions are impeded, or
totally flopped but for a fhort time, we gain an idea,
that there muft be a great accumulation of fenfo-
rial power; as its production in thefe organs, which
are fubjecl to perpetual activity, is continued during
their quiefcence, and is in confequence accumu-
lated.

While, on the contrary, where thofe vital organs
aft too forcibly by increafe of iUmulus without a
proportionally-increafed production of fenforial pow-
er in the brain, it is evident, that a great deficiency
of action, that is torpor, muft foon follow, as in
fevers ; whereas the locomotive mufcles, which act
only by intervals, are neither liable to fo great ac-
cumulation of fenforial power during their times of
inactivity, nor to fo great an exhauftion of it during
their times of action.

Thus, on going into a very cold bath, fuppofe at
33 degrees oi heat on Fahrenheit's fcale, the action
of the fubcutaneous capillaries, or glands, and of
the mouths of the cutaneous abforbents is diminifh-
ed, or ceafes for a time. Hence lefs or no blood
paries thefe capillaries, and palenefs fucceeds. But
foon after emerging from the bath, a more florid
colour and a greater degree of heat is generated
on the fkin than was pofferTed before immerfion ;
for the capillary glands, after this quiefcent Hate,
occafioned by the want of ftimulus, become more
irritable than ufual to their natural ftimuli, owing
to the accumulation of fenforial power, and hence
a greater quantity of blood is tranfmitted through
them, and a greater fecretion of perfpirable mat-
ter ; and, in confequence, a greater degree of heat
fucceeds. During the continuance in cold water
the breath is cold, and the act of refpiration quick
and laborious ; which have generally been afcribed

to

424 DISEASES OF IRRITATION. SECT. XXXII. 3

to the obftruclion of the circulating fluid by a fpafm
of the cutaneous veffels, and by a confequent ac-
cumulation of blood in the lungs, occafioned by
the preflure as well as by the coldnefs of the water.
This is not a fatisfaclory account of this curious
phenomenon, fince at this time the whole circula-
tion is lefs, as appears from the fmallnefs of the
pulfe and coldnefs of the breath ; which mew that
lefs blood pafies through the lungs in a given time ;'
the fame' laborious breathing immediately occurs
when the paienefs of the fkin is produced by fear,-
wheie no external cold or preflure are applied.

The minute veflels of the bronchia, through
which the blood pafies from the arterial to the venal
fyftem, and which correfpond with the cutaneous
capillaries, have frequently been expofed to cold
air, and become quiefcent along with thofe of the
fkin ; and hence their motions are fo aflbciated
together, that when one is aife6led either with qui-
efcence or exertion, the other fympathizes with it,
according to the laws of irritative aflbciation. See
Seel:. XXVIT. i. on haemorrhages.

Befides the quiefcence of the minute veflels of
the lungs, there are many other fyftems of veflels
which become torpid from their irritative aflbcia-
tions with thofe of the fkin, as the abforbents of
the bladder and interlines ; whence an evacuation
of pale urine occurs, when the naked fkin is ex-
pofed only to the coldnefs of the atmofphere ; and
fprinkling the naked body with cold water is known
to remove even pertinacious conitipation of the
bowels. From the quiefcence of fuch extenfive
fyftems of veflels as the glands and capillaries of
the ikin, and the minute veflels of the lungs, with
their various abforbent feries of veflels, a great ac-
cumulation of fenforial powers is occafioned; part
of which is again expended in the increafed exer-
tion of all thefe veflels, with an uriiverfal glow of

heat

SECT.XXXIf. 3. DISEASES OF IRRITATION. 42$

heat in confequence of this exertion, and the re-
mainder of it adds vigour to both the vital and
voluntary exertions of the whole day.

If the activity of the fubcutaneous vefTels, and
of thofe with which their actions are afibciated, was
too great before cold immerfion, as in the hot days
of fummer, and by that means the fenforial power
was previously diminifhed, we fee the caufe why
the cold bath gives fuch preient ftrength ; namely,
by (topping the unneceflary activity of the fubcu-
taneous veflels, and thus preventing the too great
exbauflion of fenforial power ; which, in metapho-
rical language, has been called bracing the fyftem :
which is, however, a mechanical term, only appli-
cable to drums, or mufical firings : as on the con-
trary the word relaxation, when applied to living
animal bodies, can only mean too fmall a quantity
of ftimulus, or too fmall a quantity of fenforial
power : as explained in Seel. XH. i.

3. This experiment of cold bathing prefents us
with a fimple fev^r-fit ; for the pulfe is weak, fmall,
and quick during the cold immerfion ; and be-
comes flrong, full, and quick during the fubfequent
glow of heat ; till in a few minutes thefe fymptoms
iubfide, and the temporary fever ceafes,

In thofe conftitutions where the degree of imr-
ritability, or of debility, is greater than natural, the
coldnefs and palenefs of the fkin with the quick
and weak pulfe continue a long time after the patient
leaves the bath ; and the fubfequent heat approach-
es by unequal flufhings, and he feels himfelf dif-
ordered for many hours. Hence the bathing in
a cold fpring of water, where the heat is but forty-
eight degrees on Fahrenheit's thermometer, much
difagrees with thofe of weak or inirritable habits of
body j who poffefs fo little fenforial power, that they
cannot without injury bear to have it diminifhed
even for a fhort time > but who can neverthelefs

bear

4*6 DISEASES OF IRRITATION. SECT. XXXII. 3.

bear the more temperate coldnefs of Buxton bath,
which is about eighty degrees of heat, and which
ftrengthens them, aud makes them by habit lefs lia-
ble to great quiefcence from fmall variations of
cold, and thence lefs liable to be difordered by the
unavoidable accidents of life. Hence it appears,
why people of thefe inirritable conftituticns, which
is another expreffion for fenforial deficiency, are
often much injufed by bathing in a cold fpring of
water ; and why they mould continue but a very
fhort time in baths, which are colder than their
bodies ; and flioul4 gradually increafe both trre de-
gree of coldnefs of the water, and the time of their
continuance in it, if they would obtain falutary ef-
fects from cold immerfions. See Se6t. XII. 2. i»

On the other hand, in all cafes where the heat
of the external furface of the body, or of the inter-
nal furface of the lungs, is greater than natural,
the ufe of expofure to cool air may be deduced.
In fever-fits attended with ftrength, that is with
great quantity of fenforial power, it removes the
additional ftimulus of heat from the furfaces above-
mentioned, and thus prevents their excefs of ufe.
lefs motion ; and in fever-fits attended with debi-
lity, that is with a deficiency of the quantity of
fenforial power, it prevents the great and dangerous
wafte of fenforial power expended in the unnecef-
fary increafe of the actions of the glands and capil-
laries of the (kin and iungs.

4. In the fame manner, when any one is long
cxpofed to very cold air3 a quiefcence is produced
of the cutaneous and pulmonary capillaries and ab-
forbents, owing to the deficiency of their ufual fti-
mulus of heat ; and this quiefcence of fo great a
quantity of veffels affects, by irritative aflbciation,
the whole abforbent and glandular fyflem, which
becomes in a greater or lefs degree quiefcent, and
a cold fit of fever is produced,

If

. XXXII. 4. DISEASES OF IRRITATION. 427

It the deficiency of the ftimulus of heat is very
great, the quiefcence becomes fo general as to ex-
tinguifh life, as in thofe who arc frozen to death.

If the deficiency of heat be in lefs degree, but
yet fo great as in fome meafare to diforder the
fyftem, and fhould occur the fucceeding day, it
will induce a greater degree of quiefcence than
before, from its acting in concurrence with the
period of the diurnal circle of actions, explained
in Seel:. XXXVf. Hence from a fmali beginning
a greater and greater degree of quiefcence may be
induced, till a complete fever-fit is formed ; and'
which will continue to recur at the periods by
which it was produced. See Seel. XVIL 3. 6.

If the degree of quiefcence occafioned by de-
fect of the itimulus of heat be very great, it will
recur a fecond time by a (lighter caufe, than that
which firft induced it. If the caufe, which induces
the fecond fit of quiefcence, recurs the fucceed-
ing day, the quotidian fever is produced ; if not till
the alternate day, the tertian fever ; and if not till
after feventy-two hours from the firft fit of quief-
cence, the quartan fever is formed. This laft kind'
of fever recurs lefs frequently than the other, as it
is a difeafe only of thofe of 'the temperament of
affociability, as mentioned in Seet. XXXI. ; for in
other conftitutions the capability of forming a habit
ceafee, before the new caufe of quiefcence is again
applied, if that does not occur fooner than in
feventy-two hours

.And hence thofe fevers, whofe caufe is from cold
air of the night or morning, are more liable to
obferve the folar day in their periods ; while thofe
from other caufes frequently obferve the lunar day
in their periods, their paroxyfms returning' near an:
hour later every day, as explained in Seel. XXXVI.

IV. Another frequent caufe of the cold fits of
fever is the defect of the ftimulus of diftentioh.

F f The

4*8 DISEASES OF IRRITATION. SECT. XXXII. 4

The whole arterial fyftem would appear, by the ex-
periments of Haller, to be iiritable by no other
flimulus, and the motiont of the heart and ali-
mentary canal are certainly in fome meafure de-
pendant on the fame caufe. SeeSe&.XIV. 7. Hence
there can be no wonder, that the diminution of
detention fhould frequently induce the quiefcence,
which Conftitutes the beginning of fever-fits.

Monfieur Leiutaud has judicioufly mentioned the
deficiency of the quantity of blood amongft the
caufes of difeafes, which he fays is frequently evi-
dent in diiTeclions : fevers are hence brought on by
great haemorrhages, diarrhoeas, 01 other evacuations;
or from the continued ufe of diet, which contains
but little nourifhment; or from the exhauftion oc
caiioned by violent fatigue, or by thofe chronic dif
cafes in which the digeftion is much impaired ; ai
where the ftomach has been long affe&ed with th<
gout or fc birr us ; or in the paralyfis of the liver,
as deferibed in Sedt. XXX. Hence a paroxyfm o;
gout is liable to recur on bleeding or purging ; as
the torpor of fome vifcus, which precedes the in
flamma'tion of the foot, is thus induced by the want
of the ftimulus of diftention. And hence the e>;
tremities of the body, as the nofe and fingers, are
more liable to become cold, when we have long
abftained from food; arid hence the pulfe is increaf-
ed both in ftrength and velocity above the natural
Ihndard after a full meal by the ftimulus of dif-
tention.

However, this ftimulus of diftention, like th
ftimulus of heat above defcribed, thougb it contr
butes much to the due adlion not only of the heart,
arteries, aud alimentary canal, but feems neceflary
to the proper fee ret ion of all the various glands ;
yet perhaps it is not the fole caufe of any of thele
numerous motions: for as the lacleals, cutaneous
abforbents, and the various glands appear to be

(Umulaied

SECT. XXXII. 5. DISEASES OF IRRITATION. 429

Simulated into acYion by the peculiar pungency of
the fluids they abforb, fo in the inteilinal canal the.,
pungency of the digefting aliment, or the acrimony
of the faeces, ieein to contribute, as well as their
bulk, to promote the periftaltic motions ; and in the
arterial fyftem, the momentum of the particles of
the circulating blood, and their. acrimony, ftimulate
the arteries, a$ well as the diftenUon occafioned
by. it. ., Where the pulfe is fmall this defeci of dif-
tentiott is prefent, and. contributes much, tQ pro-
duce the febris irritativa pulfu debili, or irritative
fever with weak pulfe, called by modern writers
nervoits fever,, as a predifponent caufe. See Sec"t.
XII. I. 4. Might not the transfufion of blood,
fuppoie of four ounces daily from a ftrong man,
or other healthful animal, as a fheep or an afs, be
ufed in the early ftate of nervous or putrid fevers
with great profpc£l of fuccefs ?

V. The defed of the momentum of the particles
of. the circulating blood is another caufe of the
quiefcence., . with which the cold fits of fever com-
mence. This ftimulus of the mpmentuin of the pro-
greflive particles of the blood docs not aft over
the whole body like thofe of heat and diflention
above defcribed; but is confined to the arterial fyf-
tern ; an'd differs from, the ftimulus of the detention
of the bloody as much as the vibration of the air
does from the currents of it. Thus are the dif-
ferent organs of our bodies ftimulated by four dif-
ferent mechanic properties of the exteirial world :
the fenfe of touch by the predu.re of folid bodies
fc> as to diftinguifh their figure; the mufcular fyf-
tem by the diftention, which they . occaiion ; the
internal furface of the arteries, by the .momentum
of their moving particles; and the auditory nerves,
by the vibration of them : and thefe four mechanic
properties are as different from each, other as the
F f % various

43$ DISEASES OF IRRITATION. SECT. XXXII. $,

various chemical ones, which are adapted to the
numerous glands, and to the other organs of fenfe.

2. The momentum of the progreflive particles of
blood is compounded of their velocity and their
quantity of matter : hence whatever circumftances
dirninim either of thefe without proportionally in-
creaiing the other, and without fuperadding either
of the general ftimuli of heat or diftention, will
tend to produce a qinefcence of the arterial fyftem,
and fiorn thence of all the other irritative motions,
which are connected with it.

Hence in all thofe confutations or difeafes where
t'he blood contains a greater proportion of ferum,
which is the lighteft part of its composition, the
pulfations of the arteries are weaker, as in nervous
levers, chlorolis, and hyfteric complaints ; for in
thefe cafes the momentum of the progreflive parti-
cles of blood is lefs : and hence, where the denfer
parrs of its compolition abound, as the red part
of if, or the coagulable lymph, the arterial pulfati-
ons are (honger 5 as in thofe of robuft health, and
in inflammatory difeafes.

That this ftrmulus of the momentum of the par-
ticles of the circulating fluid is of the greateft con-
feqnence to the arterial aclion, appears from the
experiment or injeding air into the blood veflels,
\vhichfeems to deftroy animal life from the want
of this ftimulus of momentum ; for the diftention
of the arteries is not diminiihed by it, it poiTerTes
no corrofive acrimony, and is lefs liable to repafs
the valves than the blood itfelf ; iince air-valves in
all machinery require much lefs accuracy of con-
flruction than thofe uhich are oppofed to water.

3. One method of recreating the velocity of the
blood, and in confequence the momentum of its
particles, is by the exercife of the body, or by
the fusion of its furface : fo, on the contrary, too
great indolence contributes to decreafe this ftimulus

of

SECT. XXXII. 6. DISEASES OF IRRITATION. 43r

of the momentum of the particles of the circulating
blood, and thus tends to induce quiefcence : as is
feen in hylleric cafes, and chlorous, and the other,
difeafes of fedentaiy people.

4. The velocity ol the particles of the blood in
certain circumilances is increafed by venefe&ion,
which, by removing a part of it, diminishes the re-
iiftance to the motion of the other part, and hence
jthe momentum of the particles of it is increafed.
This may be eaiily undeiftood by confidering it in
the extreme, fmce, if the refiftance was greatly in-
creafed, fo as to overcome the propelling power,
there could be no velocity, and in confequence no
momentum at all. From this circumftance arifes
that curious phenomenon, the truth of which I
nave been more than once witnefs to, that vene-
leclion will often iqftantaneoufly relieve thofe ner-
vous pains, which attend the cold periods of hyfle-
lic, afthmatic, or epileptic difeaies ; and that even
•where large dofes of opium have been in vain ex-
hibited. In thefe cafes the pulfe becomes ilronger
after the bleeding, and the extremities regain their
natural warmth ; and an opiate then given a6ts
with much more certain effecl:.

VI. There is another caufe, which feems pccafi-
pnally to induce quiefcence into fome part of
our fyftem, I mean the influence of the fun, ^nd
moon; the attraction of thefe luminaries., by de-
creafing the gravity of the particles of the blood,
cannot aifeft their momentum, as their vis inertia:
remains the fame ; but it may neverthelefs produce
fome chemical change in them, becaufe whatever
affe&s the general attractions of the particles of
matter may be fuppofed from analogy to affect
their fpecific attradions or affinities : and thus the
flimulus of the particles of blood may be dimi-
nifhed, though not their momentum. As the tides
of the fea obey the fouthing and northing of the

moon

4|a DISEASES OF IRRITATION. SECT. XXXI). t.

moon (allowing for the time necefTary for their
xriotion, and the obihucYions of the fhores), it is
probable, that there are alib atmofpheric tides on
both fides of the earth, which to the inhabitants
of another plane* might fo defied the Jight as to
referable the ring of Saturn. Now as thefe tides
of water, or of air, are railed by the diminution
of their gravity, it follows, that their preffure on
the furface of the earth is no greater than the
preffure of the other parts of the ocean, or of the
atmofphere, where no fuch tides exift ; and^there-
fore that they cannot affeclt the mercury in the
barometer. In the fame manner, the gravity in all
^ther terreftrial bodies is cjiminifhed at the times
pf the fouthing and northing of the niopn, and that
ma greater degree w.htn- this coincides- with the
ibuthing and northing of the fun^ and this in a
ftill greater degree about the times of the equi-
noxes* This decreafe of the gravity of all 'bodies
during the time the moon pafTes our zenith^ 'or
nadir might poffibly be fhewn by the flower vi-
brations of a pendulum,- compared with a fpring
clock, or with : aftronomjcal obfervation. Since a
pendulum of a certain length moves flower at the
line than near the poles, becaufe the gravity being
diminifhed and the vis inertias continuing the fame,
the motive power is lefs, but the refinance to be
overcome continues the fame. Tfie combined pow-
ers of the lunar and folar attraction is eftimated
by Sir Ifaac Newton not to exceed one 7,868, §5oth
part of the power of gravitation, which feems in-
deed but a fmail circumftance to prpduce any con-
iiderable effedj: on the weight of fublunary bodies,
and yet this is fufficienjt to raife the tides at the
equator above ten feet high ; and if it be conii-
dcred, what frnall impulfes of other bodies produce
their effedls on the organs of fenfe adapted to the
perception of them, as of vibration on the aucji-

tdrjr

. XXXII. 6. DISEASES OF IRRITATIO^. 433

nerves, we fliall ceafe to be furprifed, that
fo minute a diminution in the gravity of the par-
ticles of blood fhou}d fo far affect their chemical
changes, or their ftimujating quality, as, joined with
other caufes, fqme.tirnes to produce the beginnings
of difeafes.

Add to this, that if .the lunar influence produ-
ces a very fmgll degree of quiefcencq at firft, and
if that rcjcurs #t certain periods even with lefs
power to produce quiefcence than at firft, yet the
quiefcence will daily increafe by the acquired
habit a6lingat the fame time, till at length fo great a
degree of quiefcence is induced as to produce
phrenfy, canine madnefs, epilepfy, hyfteric pains
or cold fits of fever, inflances of many of which
are to be found in Dr. Mead's W9rk on this f ab-
ject. The folar influence alfo appears daily in fe-
yeral difeafes; but as darknefs, filence, fleep, and
our periodical meals mark the parts of the folaf
circle of actions, it is fometimes dubious to wliich
of thefe the periodical returns of thefe difeafes ar$
to be afcribed.

As far as I have been able tp obferve, the pe-
riods of inflammatory difeafes obferve the folar
day ; as the gout and rheumatifm have their greateft
quiefcence about noon and midnight, and their ex-
acerbations fome hours after ; as they have more
frequently their immediate caufe from cold air, in-
.anition, or fatigue, than from the effe£l of luna-
tions : whilft the cold fits of hyfleric patients,
and thofe in nervous fevers, more frequently occur
twice a day, later by near half an hour each
time, according to the lunar day ; w hi 1ft fonie fus
of intermittents, which are undifturbpd by medi-
cines, return at regular folar periods, and others
at lunar ones ; which may, probably, be owing to
the difference of the periods of thofe external cir-

cumftances

434 DISEASES OF IRRITATION. SECT. XXXU. p.

cumftances of cold, inanition, or lunation, which
immediately caufed them.

'v We muft, however, oWerve, that the periods of
quiefcence and exacerbation in difeafes do not
always commence at the time&'of the fyzygies or
'quadratures of the' moon and fun, or at the times
of their pafling the zenith or nadir; but as it is
probable, that the ftimulus of the particles of the
circumfluent blood is gradually diminifhed from
the time of the quadratures to that of the fyzy-
gies, the quiefcence may commence at any hour,
when co-operating with other caufes of quiefcence,
it becomes great enough to produce a difeafe :
afterwards it will Continue to recur at the fame
'periods of the lunar or folar influence; the fame
caufe operating conjointly with the acquired habit,
that is with the catenation of this new motion
'with the difTevered links of the lunar or folar cir-
cles of animal a&ion.

In this mariner the periods of menftruation obey
the lunar month with great exadtnefs in healthy pa-
tients (and perhaps the venereal orgafm in brute
animals does the fame), yet tjiefe periods do not
commence ' either at the fyzygies or quadratures
t)f the lunations/ but at whatever time of the lunar
periods they begin, they obferve the fame in their
returns till fome greater caufe diflurbs them.

Hence, though the bell way to calculate the time
of the expected returns of the paroxyfms of peri-
odical difeafes is to count the number of hours
between the commencement of the two preceding
fits, yet the following obfervations may be worth
attending to, when we endeavour to prevent the
returns of maniacal or epileptic difeafes ; whofe
periods (at the beginning of them efpecially) fre-
quently obferve the fyzygies of the moon an4
'fun, and particularly about the equinox.

The greateft of the two tides happening in every
, * *-M revolution

. XXXII. 7* DISEASES OF IRRITATION. 435

revolution of the moon, is that when the moon ap-
proaches neareft to the zenith or nadir ; for this
reafon, while the fun is in the northern ligns,
that is during the vernal and fummer months, the
greater of the two diurnal tides in our latitude is
that, when the moon is above the horizon ; and
when the fun is in the fouthern figns, or during the
autumnal and winter months, the greater tide is
that, which arifes when the moon is belo\v the
horizon : and as the fun approaches fomewhat
nearer the earth in winter than in fummer, the
greateft equinoctial tides are obfervcd to be a little
.before the vernal equinox, and a little after the
autumnal one.

Do not the cold periods of lunar difeafes com-
mence a few hours before the fou thing of the
moon during the vernal and fummer months., and
before the northing of the moon during the au-
tumnal and winter months ? Do not palfies and
apoplexies, which occur about the equinoxes,
happen a few days before the vernal equinoctial
Junation, and after the autumnal one ? Are not the
periods of thofe diurnal difeafes more obftinate,
that commence many hours before the fouthing
or northing of the moon, than of thofe which
commence 'at thofe times? Are not thofe palfies
and apoplexies more dangerous which commence
many days before the fyzygies of the moon, than
thofe which happen at thofe times? See Se6l.
JCXXVI. on the periods of difeafes.

VII. Another very frequent caufe of the cold
fit of fever is the quiefcenceef fome of thofe large
Congeries of glands, which compofe the liver,
fpleen, or pancreas; one or more of which are
frequently fo enlarged in the autumnal intermit-
tents as to be perceptible to the touch externally,
and are called by the vulgar ague-cakes. As thefe
glands are flimulated into a&ion by the fpccific

pungency

DISEASES OF IRRITATION. SECT. XXXII.?.

pungency of the fluids, which they abforb, the/
general caufe of their quiefcence feems to be i^e
too great inlipidity of the fluids of the body, co-
operating perhaps at the fame time with other ge-
neral caufes of quiefcence.

Hence, in mariliy countries at cold feafons,
which have fucceeded hot ones, and amongft thofe,
who have lived on innutritious and unfti ululating
diet, thefe agues are mod frequent. The enlarge-
ment of thefe quiefcent vifcera^and the Iwelling of
the prsecordia in many other fevers, is,, mod pro-
bably, owing to the fame caufe; which may confiil
in a general efficiency of the production of fenio-
rial power, as well as in the diminifhed Simulation
of the fluids ; and wh.ep the quieicence of fo great
a number of glantjs, as conftitute one of thofe
Jarge vifcera, commences, all the other irritative
motions are aije$:ed by their connexion, with it,
and the cold fit of fever is prgduced.

VIII. There are many other caiife$3 which pro-
duce quiefcence of fpme part of the animal fyftem,
as fatigue, hunger, thirft, bad djet, difappointed
love, unwhoiefome air, exhauftion from evacua-
tions, and many others ; but the lad caufe, that we
thall mention, as frequently productive of cold
fits of fever, is fear or anxiety of mind. The
pains, which we are firft and moil generally ac-
quainted with, have been produced by defect of
fome (limulus ; thus, foon after our natiyity \vef
become acquainted with the pain from tl)e;? cold-
nefs of the air, from the want of refpiration, and.
from the want of food. Nqw §1J tjiefe pain? pcca{
floned by defect of ilimulus are attended withqui-
cfcence of the organ, and at the fame, time with
a greater or lefs degree of quiefcence of other
parts of the fyftem : thus, if we even endure the^
pain of hunger fo as to mifs one meal inflead of
our daily habit of repletion, not only the perif-
taltic motions of the ftomach and bowels are di-

miniiliecj

SfiCT.X3fXlI.9- DISEASES OF IRRITAf ION. 437

minifhed, but we are more liable to coldnefs of
our extremities, as of our nofes, and cars, and
feet, than at other times.

Now, as fear is originally excited by our hav-
ing experienced pain, and is itfelf a painful affec-
tion, the fame quieicence of other fibrous motions
Accompany it, as have been mod frequently con-
nected with this kind of pain, as explained in
Seel. XVI. 8 i. as the coldnefs and palenefs of
the ikin, trembling, difficult refpiration, indigef-
tion, and other fymptoms, which contribute to
form the cold fit of fevers. Anxiety is fear con-
tinued through a longer time, and, by producing
chronical torpor of the fyftem, extinguimes life
/lowly, by what is commonly termed a broken heart.
IX. I. We now Hep forwards to coniider the
other fymptoms in confequenpe of the quicfcence
which begins the fits of fever. If by any of the
circumftances before defcribed, or by two or more
of them a6ling at the fame time, a great degree
of quiefcence is induced on any confiderable part
of the circle pf irritative motions, the whole clafs
of them is more or lefs cjifturbed by their irrita-
tive aflfociations. If this torpor be occafioned by
a deficient fupply of fenforial power, and happens
to any of thofe parts of the fyftem, which are ac-
cuftomecj to perpetual a&ivity, as the vital motions,
the torpor ihcreafes rapidly, becaufe of the -great ex-
penditurp of fenforial power by the in ceilant acti-
vity' pf T t)iofe ' parts of the fyilem, as fhewn in
No. 3-2. of this Sedlion. Hence a deficiency of
all the fecretions facceeds, and as animal heat is
produced in proportion to the quantity of thofe
fecretions, the coldnefs of the fkin is the firft
circumdance, which is attended to. Dr. Martin
aliens, that fome parts of his body were warmer
than natural in the cold fit of fever ; but it is
certain, that thofe which are uncovered, as the
fingers, and nofe, and ears, are much colder to
the touch, and paler in appearance. It is pofli-

blc

438 DISEASES OF IRRITATION. SECT. XXXII.9:

i>le, that his experiments were made at the be-
ginning of the fubfequent hot fits; which com-
mence with partial diftrifeutions of heat, owing to
fome parts of the body regaining their natural
irritability fooner than others.

From the quiefcence of the anaftomoflng capil-
laries a palenefs pf the fkin fucceeds, and a lefs
fecretion of the perfpirable matter ; from the qui-
efcence of the pulmonary capillaries a difficulty
of refpiration arifes ; and from the quiefcence of
the other glands lefs bile, lefs gaftric and pancrea-
tic juice, are fecreted into the ftomach and intef-
tines, and lefs mucus and faliva are poured into
the mouth ; whence arises the dry tongue, cof-
tivenefs, dry ulcers, and paucity of urine. From
the quiefcence of the abforbent fyflem arifes the
great thirft, as lefs moifture is abibrbed from the
atmofphere. The abforption from the atmofphere
was obferved by Dr. Lyfter to amount to eighteen
ounces in one night, above what he had at the
fame time infenfibly perfpired. See Langrifh,
On the fame account the urine is pale, though in
fmall quantity,' for the thinner part is not abforbed
from it; and when repeated ague fits continue
long, the legs fwell from the diminifhed 'abforp-
tion of the cellular abforbents.

From the quiefcence of the inteftinal canal a
lofs of appetite and flatulencies proceed. From
the partial quiefcence of the glandular vifcera a
fuelling and teniion about the pr2ecordia becomes
fenfible to the touch ; which is occafioned by the
delay of the fluids from the defe£l of venous or
lymphatic abforption. The pain of the forehead,
and of the limbs, and ef the fmall of the back,
arifes from the quiefcence of the membranous
fafcia, or mufcles of thofe parts, in the fame man-
ner as the Ikin becomes painful, when the vefiels,
of which it is compofed, become quiefcent from

cold

SECT. XXXII. 9. DISEASES OF IRRITATION 439

cold. The trembling in confequence of the pain
of coldnefs, the reftleflhefs, and the yawning, and
ftretching of the limbs, together with the Ihud-
dering, or rigours, are convuliive motions ; and
will be explained amongft the difeafes of voli-
tion ; Sea. XXXIV. ,

Sicknefs and vomiting is a frequent fymptom
in the beginnings of fever-fits, the mufcular fibres
of the ftomach fhare the general torpor and debi-
lity of the fyftem ; their motions become firft
leffened, and then flop, and then become retro-
grade ; for the acl of vomiting, like the globus
hyftericus and the borborigmi of hypochondriacs,
is always a fymptom of debility, either from want
of ftimulus, as in hunger ; or from want of fen-
forial power, as af er intoxication ; or from fym-
pathy with fome other torpid irritative motions,
as in the cold fits of ague. See Sect. XII. 5. 5.
XXIX. 11. and XXXV. i. 3. where this aft of vo-
miting is further explained.

The fmall pulfe, which is faid by fome writers
to be flow at the commencement of ague-fits, and
which is frequently trembling and intermittent, is
owing to the quiefcence of the heart and arterial
fyftem, and to the refiftance oppofed to the cir-
culating fluid from the inactivity of all the glands
and capillaries. The great weaknefs and inability
to voluntary motions, with the infenfibility of the
extremities, are owing to the general quiefcence
of the whole moving fyftem ; or perhaps, fimpiy
to the deficient production of fenforlal power.

If all thefe fymptoms are further increafed,
the quiefcence of all the mufcles, including the
heart and arteries, becomes complete, and death
enfues. This is, moft probably, the cafe of thofe
who are ftarved to death with cold, and of thofe
who are faid to die in Holland from long fkaiting
on their frozen canals.

2. As

44* DISBARS OF IRRITATION. SECT. XXXII 9.

2. As foon as this general quiefcence of the*
fyftem. ceafes, either by the diminution of the
caufe, or by the accumulation of fenforial power,
(as in fyneope, Sect. XII. 7. i.). which is the na-
tural confequenee of previous quiefcence, the hot
fit commences. Every gland of the body is .now
ftimulaied into ftfoflgfcr £6tion than is" natural, as
its irritability- is increafed by accumulation of
fenforial power during its late quiefcence, a fuper-
abu'hdan'ce of all the fecretions is produced, and an
increafe of heat hi confequence of the increafe of
thefe fec?etio'ns. The fkin becomes red, and the
perfpitation great, owing to the increafed action of
the capillaries during the hot part of the paroxyfm.
The fecretion of perfpirable matter is perhaps great-
er during the hot fit than In the fweating fit, which
follows; but as the abforpticn of it alfo is greater,
it does not ftand on the fkin in vifible dro'ps : add
to this, that the evaporation of it is aifo greater,
from the increafed heat oF the fkin. But at the
decline of the hot fit, as the mouths of the abfor-
bents of the fkin are expofed to the cooler air, or
bed-clothes, thefe velfels fooner lofe their increafed
activity, and ceafe to abforb more than their natural
quantity : but the fecerning veffels for fome time
longer, being kept warm by the circulating bloody
continue to pour out an increafed quantity of per-
fpirable matter, which now Hands on the fkin^ in
large virible drops ; the exhalation of it alfo being
leflened by the greater coolnefs of the fkin, as well
as its abforpfion by the dimimfhed action of the
lymphatics. See Giafs I. 1. 1. 3.

The incieafed fecretion of bile and of other flu-
ids poured into the inteflines frequently induce a
purging at the decline of the hot fit; for as the
external abforbent veffels have their mouths ex-
pofed to the cold air, as above mentioned, they
ceafe to be excited into unnatural activity fooner

tharj

SECT.XXXU. 9. DISEASES OF IRRITATION.

than the fecretory veffels, whofe mouths are expofed
to the waniith of the blood : now, as the internal
abforbents fympathize with the external ones, thefe
alfo, which during the hot fit drank up the thin-
ner part of the bile, or of other fecreted fluids,
lofe their incieafed activity before the gland loles
its increafed activity, at the decline of the hot fit ;
and the loofe dejections are produced from the
fame caufe, that the incieafed perfpiration Hands
on the fmfa^e of the fkin, from the increafed ab-
ibrption ceafing iboner than the incieafed fecre-
tion.

The urine during the cold fit is in fmall quan-
tity and pale, both from a deficiency of the fecre-
tion and a deficiency of the abforptton. During
the hot fit it is in its ufual quantity, but very high-
coloured and turbid, becaufe a greater quantity had
been fecreted by the increafed action of the kid-
riies, and alfo a greater quantity of its more aque-
ous part had been a bfoi bed from it in the bladder
by the increafed aclion of the abforbents ; and
laftly, at the decline of the hot fit it is in large
quantity and lefs coloured, or turbid, becaufe the
abforbent vefTels of the bladder, as obferved above,
lofe their increafed action by iympathy with the
cutaneous ones fooner than the fecretory veffels of
the kidnies lofe their increafed activity. Hence
the quantity of the fedimenf, and the colour of the
urine, in fevers, depend much on the quantity fe-
creted by the kidnies, and the quantity abforbed
from it again in the bladder : the kinds of fedi-
ment, as the lateritious, purulent, mucous, or
-Woody lediments, depend on other caufes. It fhould
*be obferved, that if the fweating be incieafed by
the heat of the loom, or of the bed-clothes,
a paucity of turbid urine will continue to be pn>
duced, as the abforbents of the bladder will have
their activity increafed by their fympathy with the

veflela

44* DISEASES OF IRRITATION. SECT. XXXII. 9.

veflels of the fkin, for the purpofe of fupplying the
fluid expended in perfpi ration.

The pulfe becomes itrong and full, owing to the
increafed irritability of the heart and arteries, from
the accumulation of fen fo rial power during their
quiefcence, and to the quicknefs of the return of
the blood from the various glands and capillaries.
This increafed action of all the fecretory . veflels
does not oecur veiy fuddenly, nor univerfally at
the fame time. The heat feems to begin about the
center, and to be diffufed from thence irregularly
to the other parts of the fyflem. This may be
owing to the fituation of the parts which firft be-
came quiefcent and caufed the fever-fit, efpecially
when a hardnefs of tumour about the praecordia
can be felt by the hand ; and hence this part, in
whatever vifctis it is feated, might be the firfl to
regain its natural or increafed irritability.

3. It mud be here noted, that, by the increafed
quantity of heat, and of the impulie of the blood
at the commencement of the hot fit, a great in-
creafe of itimulus is induced, and is now added to
the increafed irritability of the fyflem, which was
occafioned by its previous quiefcence. This addi-
tional flimulus of heat and momentum of the blood'
augments the violence of the movements of the ar-
terial and glandular fyftem in an increafing ratio.
Thefe violent exertions flili producing more heat and
greater momentum of the moving fluids, till at
length the fenforial power becomes walled by this
great ftimulus beneath its ufual quantity, and pre-
difpofes the fyflem to a fecond cold fit.

At length all thefe unnatural exertions fpontane-
ouily fubfide with the increafed irritability that pro-
duced them ; and which was itfelf produced by the
preceding quiefcence, in the fame manner as the
eye, on coming from darknefs into day-light, in a"
little time ceafes to be dazzled and pained, and

gradually

SBCT. XXXII. 10. DISEASES OF IRRITATION. 445

gradually recovers its natural degree of irritabi-
lity.

4. But if the increafe of irritability, and the con-
fequent increafe of the itimulus of heat and mo-
mentum, produce more violent exertions than thofe
above defcribed ; great pain arifes in fome part of
the moving fyftem, as in the membranes of the
brain, pleura, or joints ; and new motions of the
veflels are produced in coniequence of this pain,
which are called inflammation ; or delirium or ftu-
por arifes ; as explained in Sect. XXI. and XXXIII. :
for the immediate effect is the fame, whether the
great energy of the moving organs arifes from an
increafe of ftimulus or an increafe of irritability ;
though in the former cafe the waile of fenforial
power leads to debility, and in the latter to health.

Recapitulation.

X. Thofe mufcles, which are lefs frequently ex-
erted, and whofe actions are interrupted by fleep,
acquire lefs accumulation of fenforial power during
their quiefcent ftate, as the mufcles of locomotion.
In thefe mufcles after great exertion, that is, after
great exhauftion of fenforial power, the pain of fa-
tigue enfues ; and during reft there is a renovation
of the natural quantity of fenforial power; but
where the reft, or quiefcence of the mufcle, is long
continued, a quantity of fenforial power becomes
accumulated beyond what is neceflary ; as appears
by the uueafmefs occafioned by want of exercife';
and which in young animals is one caufe exciting
them into action, as is feen in the play of puppies
and kittens.

But when thofe mufcles, which are habituated
to perpetual actions, as thofe ot the ftomach by the
ftimulus of food, thofe of the veflels of the (kin by

G g the

444 DISEASES OF IRRITATION. SECT. XXXII. 10.

the ftimulus of heat, and thofe which conftitute the
arteries and glands by the fiimulus of the blood, be-
come for a time quiefcent, from the want of their ap-
propriated ftimuli, or by their aflbciations with other
quiefcent parts of the fyftem ; a greater accumula-
tion of fenforial power is acquired during their qui-
efcence, and a greater or quicker exhauftion is pro-
duced during their increafed aclion.

This accumulation of fenforial power from defi-
cient action, if it happens to the ilomach from want
of food, occafions the pain of hunger ; if it happens
to the veffels of the fkin from want of heat, it oc-
cafions the pain of cold ; and if to the arterial
fyftem from the want of its adapted ftimuli, many
difagreeable fenfations are occafioned, fuch as are
experienced in the cold fits of intermittent fevers,
and are as various, as there are glands or membranes
in the fyftem, and are generally termed univerfai
uneafinefs.

When the quiefcence of the arterial fyftem is not
owing to defed of ftimulus as above, but to the de-
fective quantity of fenforial power, as in the com-
mencement of nervous fever, or irritative fever with
weak pulfe, a great torpor of this fyftem is quickly
induced ; becaufe both the irritation from the fti-
mulus of the blood, and the aflbciation of the vaf-
cular motions with each other, continue to excite
the arteries into action, and thence quickly exhauft
the ill-fupplied vafcular mufcles ; for to reft is death ;
and therefore thofe vafcular mufcles continue to pro-
ceed, though with feebler adtion, to the extreme of
wearinefs or faintnefs ; while nothing fimilar to this
affects the locomotive mufcies, whofe addons are ge-
nerally caufed by volition, and not much fubjecl:
either to irritation or to other kinds of aflbciations
befides the voluntary ones, except indeed when they
are excited by the lafh of flavery.

In

SECT. XXXII, 10. DISEASES OF IRRITATION; 44$

In thefe vafcular mufcles, which are fubject to
perpetual a&ion, and thence liable to great accumu-
lation of fenforial power during their quielcence
from want of ftimulus, a great increafe of activity
occurs, either from the renewal of their accuitom-
ed ilimulus, or even from much lefs quantities of
ftimulus than ufual. This increafe of aclion con-
ftitutes the hot fit of fever, which is attended with
various increafed fecretions, with great concomitant
heat, and general uneaiinefs. The uneafinefs attend-
ing this hot paroxvfm of fever, or fit of exertion^
is very different from that, which attends the pre-
vious cold fit, or fit of quiefcence, and is frequent-
ly the caufe of inflammation, as in pleurify, which
is treated of in the next fedtion.

A iimilar effect occurs after the quiefcence of our
organs of fenfe ; thofe which are not fubject to per-
petual aclion^ as the tafte and fmell, are lefs liable
to an exuberant accumulation of fenforial power
after their having for a time been ina&ive ; but the
eye, which is in perpetual action during the day,
becomes dazzled, and liable to inflammation after
a temporary quiefcence.

Where the previous quiefcence has been owing to
a defect of fenforial power, and not to a defect of
ftimulus, as in the irritative fever with weak pulfe,
a Iimilar increafe of adlivity of the arterial fyftenx
fucceeds, either from the ufual ftimulus of the blood,
or from a ftimulus lefs than ufual ; but as there is
in general in thefe cafes of fever with weak pulfe a
deficiency of the quantity of the blood, the pulfe in
the hot fit is weaker than in health, though it is
ftronger than in the cold fit, as explained in No. 2. of
this fection. But at the fame time in thofe fevers,
where the defect of irritation is owing to the de-
fect of the quantity of fenforial power, as well as
to the defect of ftimulus, another circumftance oc-
curs ; which conlifts in the partial diftribution of it,

Gg z as

446 DISEASES OF IRRITATION. SECT XXXII. 10.

as appears in partial flufhings, as of the face or
bofom, while the extremities are cold; and in the
increafe of particular fccretions, as of bile, faliva,
infenfible perfpiration, with great heat of the fkin,
or with partial fweats,or diarrhoea.

There are alfo many uneafy fenfations attending
thefe increafed actions, which, like thofe belonging
to the hot fit of fever with (hong pulfe, are fre-
quently followed by inflammation, as in fcarlet fe-
ver ; which inflammation is neverthelefs accompa-
, nied with a pulfe weaker, though quicker, than the
pulfe during the remiflion or intermiflion of the pa-
roxyfms, though flronger than that of the previous
cold fit.

From hence I conclude, that both the cold and
hot fits of fever are neceflary confequences of the
perpetual and inceflant action of the arterial and
glandular fyftem fince thofe mufcular fibres, and thofe
organs of fenfe, which are moft frequently exerted,
become neceflarily moft affected both with defect
and accumulation of fenforiai power: and that hence
fcwr-fts are not an effort of nature to relieve herfelf,
and that therefore they mould always be prevented
or diminifhed as much as poflible, by any means
which decreafe the general or partial vafcular acti-
ons, when they are greater, or by increafing them
when they are lefs than in health, as defcribed in
Sed. XII. 6. i.

Thus have I endeavoured to explain, and I hope
to the farisfaction of the candid and patient reader,
the principal fymptoms or circumftances of fever
without the introduction of the fupernatural power
of fpafm. To the arguments in favour or' the doc*
trine of fpafm it may be fufficient to reply, that in
the evolution of medical as well as of dramatic ca-
taftrophe,

Ncc Deftft intcrfit, nifi dignus vindicc nodus incident.

HOR.

SECT.

SECT. XXXIII. i. DISEASES OF SENSATION, 447

SECT. XXXIII.

DISEASES OF SENSATION.

I. Motions excited by fenfation. Digejlion. Genera-
tion. Pleafure of exigence. Hypochondriacifm. z.
Pain introduced. Senfiticve fevers of two kinds. 3.
Two fenforial powers exerted in fenjitive fevers. Size
of the blood. Nervous fevers diflingui/bed from pu-
trid ones. The feptic and antifeptic theory. 4. TWQ
kinds of delirium. 5. Other animals are lefs liable
to delirium, cannot receive our contagious difeafes,
and are lefs liable to madnefs. II. I. Senfttive moti-
ons generated. 2. Injlammation explained. 3. Its
remote caufesfrom excefs of irritation, or of irrita-
bility, not from thofe pains which are owing to defect
of irritation. New vejjiels produced, and much heat*
4. Purulent matter fecreted. 5. Contagion explained.
6. Received but once. 7. If common matter be con-
tagious ? 8. Why feme contagions are received but
once. 9. Why others may be received frequently. Con-
tagions of f mall-pox and meafles do not acJ at the
fame times. Two cafes of fuch patients. 10. The
blood from patients in the fmall-pox will not infecl
others. Cafes of children thus inoculated. The va-
rious contagion is not received into the blood. It
acls by fenfitive affbciation between thejiomach and
Jkin. III. i. Absorption of f olid s and fluids, z. Art
of healing ulcers. 3. Mortif cation attended with lefs
pain in weak people.

I. i. AS many motions of the body are excited
and continued by irritations, fo others require, either

conjundly

44$ DISEASES OF SENSATION. SECT. XXXIII. t.

conjundly with thefe, or feparately, the pleafurable
or painful fenfations, for the purpofe of producing
them with due energy. Amonglt ihefe the bufinefs
of digeition fupplies us with an inftance ; if the
food, which we Swallow, is not attended with agree-
ably fenfation, it digefts lefs perfectly ; and if very
difagreeable fenfation accompanies it, fuch as a nau-
feous idea, or very difguflful tafte, the digeflion be-
comes impeded ; or retrograde motions of the fto-
ipach and cefophagus fucceed, and the food is,

The bufinefs of generation depends fo much on
agreeable fenfation, that, where the object is diC
guit-ul, neither voluntary exertion nor irritation can
effedi the purpofe ; which is alfo liable to be inter-
rupted by the pain of fear or bafhfijlnefs.

Befides the pleasure, which attends the irritations
produced by the objeds pf luil and hunger, there
feems to be a fum of pleafurable affection accompa-
nying the various fecretions of the numerous glands,
which conftitute the pleafure of life, in contradif-
tincuon to the tsedjum vitse. This quantity or fum
of pleafurable affe&ion feems to contribute to the
due or energetic performance of the whole move-
|ible tyftem, as well that of the heart and arteries,
as of digeflion and of abforption ; fince without
fhe due quantity of pleafurable fenfation, flatulen-
cy and hypochondriacifrn affedt the inteftines, and
a languor feizes the arterial pt^lfations and fecreti-
ons ; as occurs in great and continued anxiety of the
mind.

2. Betides the febrile motions occafioned by irrita-
tion, defcribed in Seel:. XXXII. and termed irritative
fever, it frequently happens that pain is excited by
the violence of the fibrous contractions ; and other
new motions are then fuperadded, in confequence,
of fenfation, which we (hall term febris fenfitiva, or
ienfitive fever* It mull be obferved, that moil it"-

ritative

SEcr.XXXlII. i. DISEASES OF SENSATION. 449

ritative fevers begin with a decreafed exertion of
irritation, owing to delea 01 ftimulus ; but that on
the contrary the feniitivc fevers, or inflammations,
generally begin with the iucreafed exertion of fen-
fation, as mentioned in Sect. XXXI. on tempera-
ments : for though the cold fit, \vhich introduces
inflammation, commences with decreafed irritation,
yet the inflammation itfelf commences in the hot
lit during the increafe of fenfation. Thus a com-
mon puftule, or phlegmon, in a part of little fen-
fibility does not excite an inflammatory fever ; but
if the ftomach, inteftines, or the tender fubftance
beneath the nails, be injured, great fenfation is pro-
duced, and the whole fyftem is thrown into that
kind of exertion, which conftitutes inflammation.

Thefe fenfitive fevers, like the irritative ones, re-
folve themfelves into thofe with arterial ftrength, and
thofe with arterial debility, that is, with excefs or
defect of fenforial power ; thefe may be termed the
febris fenfitiva pulfu forti, fenfitive fever with ftrong
pulfe, which is the fynocha, or inflammatory fever ;
and the febris fenfitiva pulfu debili, fenfitive fever
with weak pulfe, which is the typhus gravior, or
putrid fever of fome writers.

3. The inflammatory fevers, which are here term-
ed fenfitive fevers with flrong pulfe, arc generally
attended with fome topical inflammation, as pleu-
rify, peripneumony, or rheumatifm, which diftin-
guifhes them from irritative fevers with ftrong pulfe.
The pulfe is ftrong, quick, and full ; for in this fever
there is great irritation, as well as great fenfation,
employed in moving the arterial fyftem. The fize,
or coagulable lymph, which appears on the blood,
is probably an increased fecretion from the inflamed
internal lining of the whole arterial fyftem, the thin-
ner part being taken away by the increafed abforp-
of ^he inflamed lymphatics.

The

DISEASES OF SENSATION. SECT. XXXIII. t.

The fenfitive fevers with weak pulfe, which are
termed putrid or malignant fevers, are diftinguifhed
from irritative fevers with weak pulfe, called ner-
vous fe'/ers, defcribed in the laft fedion, as the
former confift of inflammation joined with debility,
and the latter" of debility alone. Hence there is
greater heat and more florid colour of the fkin in
the former, with petechias, or purple fpots, and aph-
thae, or floughs in the throat, and generally with
prev o contagion.

\Vhen animal matter dies, as a flough in the
throat, or the mortified part of a carbuncle, if it
be kept moifl and warm, as during its adhefion to
a living body, it will foon putrify. This, and the
origin of contagion from putrid animal fubftances,
feem to have given rife to the feptic and antifeptic
theory of thefe fevers.

The matter in puftules and ulcers is thus liable to
become putrid, and to produce microfcopic animal-
cula ; the urine, if too long retained, may alfo gain
a putrefcent fmell, as well as the alvine feces \ but
fonie writers have gone fo far as to believe, that the
blood itfelf in thefe fevers has fmelt putrid, when
drawn from the arm of the patient : but this feems
not well founded ; fince a fmgle particle of putrid
matter taken into the blood can produce fever, how
can we conceive that the whole mafs could continue
a minute in a putrid ftate without deftroying life ?
Add to this, that putrid animal fubftances give up
air, as in gangrenes ; and that hence if the blood
was putrid, air fhould be given out, which in the
blood-vefiels is known to occafion immediate death.

In thefe fenfitive fevers with ftrong pulfe (or in-
flammations) there are two fenforial faculties con-
cerned in producing the difeafe, viz. irritation and
fenfation ; and hence, as their combined adion is
more violent, the general quantity of fenfoiial pow-
er becomes further exhaufted during the exacerba-
tion,

SKCT. XXXIII. i. DISEASES OF SENSATION. 541

tion, and the fyftem more rapidly weakened than
in irritative, fever with ftrong pulfe ; where the fpiric
of animation is weakened by but one mode ot" us
exertion : fo that this febris feniitiva pulfu forti (or
inflammatory fever,) may be couiideied as the febris
irritativa pulfu forti, with the addition of inflamma-
tion ; and the febris fenfitiva pulfu debili (or malig-
nant fever) may be confidered as the febris irritativa
pulfu debili (or nervous fever;, with the addition of
inflammation.

4. In thefe putrid or malignant fevers a deficiency
of irritability accompanies the increafe of fenfibi-
lity ; and by this waile of fenforial power by the
excefs of fenfation, which was already too fmall,
arifes the delirium and ilupor which fo perpetually
attend thefe inflammatory fevers with arterial debi-
lity. In thefe cafes the voluntary power fir ft ceafes
to aft from deficiency of fenforial fpirit ; and the
ftimuli from external bodies have no effect on the
exhaufted fenforial power, and a delirium like a
dream is the confequence. At length the internal
ftimuli ceafe to excite fufficient irritation, and the
fecretions are either not produced at all, pr too par-
fimonious in quantity. Amongft thefe the fecretion
of the brain, or production of the fenforial power,
becomes deficient, till at laft all fenforial power
ceafes, except what is juft neceflary to. perform the
vital motions, and a f.upor fucceeds ; which is thus
owing to the fame caufe as the preceding delirium
exerted in a greater degree.

This kind of delirium is owing to a fufpenfion of
volition, and to the difobedience of the fenfes to. ex-
ternal ftimuli, and is always occafio.ned by great
debility, or paucity of fenforial power ; it is, there-
fore a bad fign at the end of inflammatory fevers,
which had previous arterial firength, as rheumatifm,
or pleurify, as it (hews the prelence of great ex-
hauftion of fenforial power in 3 fyftem, which hav?

ing

DISEASES OF SENSATION. SECT. XXXIII. i.

ing lately been expofed to great excitement, is not
fo liable to be ftimulated into its healthy a&ion,
either by additional itimulus of food and medicines,
or by the accumulation of fenforial power during
its prefent torpor. In inflammatory fevers with de-
bility, as thofe termed putrid fevers, delirium is
fometimes, as well as flupor, rather a favourable
fign ; as lefs fenforial power is wafted during its
continuance (fee Clafs II. i. 6.8.), and the conititu-
tion not having been previoufly expofed to excefs
of Simulation, is more liable to be excited after
previous quiefcence.

When the fum of general pleafurable fenfation
becomes too great, another kind of delirium fuper-
venes, and the ideas thus excited are miitaken for
the irritations of external objedls : fuch a delirium
is produced for a time by intoxicating drugs, as
fermented liquors, or opium; a permanent delirium
of this kind is fometimes induced by the pleafures
of inordinate vanity, or by the enthufiaflic hopes
of heaven. In thefe cafes the power of volition is
incapable of exertion, and in a great degree the
external fenfes become incapable of perceiving their
adapted ftimuli, becaufe the whole fenforial power
is employed or expended on the ideas excited by
pleasurable fenfation.

This kind of delirium is diftinguifhed from that
which attends the fevers above mentioned from its not
being accompanied with general debility, but fimply
with excefs of pleafurabie fenfation ; and is there-
fore in forne meafure allied to madnsfs or to reve-
rie; it differs from the delirium of dreams, as in
this the power of volition is not totally fufpendid,
nor are the fenfes precluded from external ftimula-
tion ; there is therefore a degree of confiftency, in
this kind of delirium, and a degree of attention to
external objects, neither of which exifl in the deli-
rium of fevers or in dreams.

SECT. XXXIII. a. DISEASES OF SEMSATION. 453

5. It would appear, that the vafcular fyftem of
other animals are lefs liable to be put into action
by their general fum of pleafurable or painfui fen-
fation ; and that the trains of their ideas, and the
mufcular motions uiually aflbciated with them, are
lefs powerfully conneded than in the human fyitem.
For other animals neither weep, nor fmile, nor
Jaugh ; and are hence feldom fubjeft to delirium,,
as treated of in Sed}. XVI. on InftincL Now as
pur epidemic and contagions djfeafes are probably
produced by difagreeable feafatiou, and not fimply
by irritation ; there appears a reafon, why brute
animals are lefs liable to epidemic or contagious
difeafes; and fecondiy, why none of our contagions,
as the fmall-pox or meafles, can be communicated
to them, though oae of theirs, viz. the hydropho-
bia, as well as many of their poifons, as thofe of
foakes and of infe&s, cornmunjcate tbeir Deleterious
or painful effedls to mankind-

Where the quantity of general painful fenfation
is too great in the fyftem, inordinate voluntary ex-
ertions are produced either of pur ideas, as in me-
lancholy and madnefs, or of our mufcles, as iu
convulfion. From thefe maladies alfo brute animals
are much more exempt than mankind, owing to
their greater inaptitude to voluntary exertion, as
mentioned in Seel. XVI. on Inftincl.

IL i. When any moving organ is excited into
fuch violent motions, that a quantity of pleafurable
pr painful fenfation is produced, it frequently hap-
pens (but not always) that new motions of the af-
fefted organ are generated in confequence of the
pain or pleafure, which are termed inflammation.

Thefe new motions are of a peculiar kind, tend-
ing to diflend the old, and to produce new fibres,
and thence to elongate the ftraight mufcles, which
ferve locomotion, and to form new veflels at the
extremities or fides of the vafcular mufcles.

2. Thus

4S4 DISEASES OF SENSATION. SECT. XXXIII. a,

2. Thus the pleafurable fenfations produce an
enlargement of the nipples of nurfes, of the papillse
of the tongue, of the penis, and probably produce
the growth of the body from its embryon ftate to
its maturity ; whilft the new motions in confequence
of painful fenfation, with the growth of the fibres
or veflels, which they occafion, are termed inflamma-
tion.

Hence when the flraight mufcles are inflamed,
part of their tendons at each extremity gain new life
and fenfibility, and thus the mufcle is for a time
elongated ; and inflamed bones become foft, vafcu-
lar, and fenfible. Thus new veflels (hoot over the
cornea of inflamed eyes, and into fchirrhous tu-
mours, when they become inflamed ; and hence all
inflamed parts grow together by intermixture, and
inofculation of the new and old veflels.

The heat is occaiioned from the increafed fecre-
tions either of mucus, or of the fibres, which pro-
duce or elongate the veflels. The red colour is
owing to the pellucidity of the newly formed veflels,
and as the arterial parts of them are probably form-
ed before their correfpondent venous parts.

3* Thefe new motions are excited either from
the increafed quantity of fenfation in confequence
of greater fibrous contractions, or from increafed
feniibility, that is, from the increafed quantity of
fenforial power in the moving organ. Hence they
are induced by great external ftimuli, as by wounds,
broken bones, and by acrid or infectious materials,
or by common ilimulion thofe organs, which have
been fome time quiefcein ; as the ufual light of
the day inflames the eyes of thofe, who have been
confined in dungeons ; and the wTarrnth of a com-
mon fire inflames thofe, who have been previoufly
expofed to much cold.

But thefe new motions are never generated by
that pain, which arifes from defect of ftirnulus, as

from

SECT.XXXIIT.2. DISEASES OF SENSATION. 455

from hunger, third, cold, or inanition, with all
thofe pains which are termed nervous. Where thefe
pains exift, the motions of the affected part are
leilened ; and if inflammation fucceeds, it is in fome
diiiant parts ; as coughs are caufed by coldnefs and
moifture being long-applied to the feet ; or it is in
confequence of the renewal of the flimulus, as of heat
or food, which excites our organs into ftronger acti-
on aftet their temporary quiefcence ; as kibed heels
after walking in fnow.

4. But when thefe new motions of the vafculaf
mufcles are exerted with greater violence, and thefe
veffels are either elongated too much or too haftily,
a new material is fecreted from their extremities,
which is of various kinds according to the pecu-
liar animal motions of this new kind of gland, which
fecre'es it ; fuch is the pus laudabile or common
matter, the variolous matter, venereal matter, ca*
tarrhous matter, and many others.

5. Thefe matters are the product of an animal
procefs ; they are fecreted or produced from the
blood by certain difeafed motions of the extremities
of the blood-vefiels, and are on that account all
of them contagious ; for if a portion of any of
thefe matters is tranfmitted into the circulation, or
perhaps only inferted into the ikin, or beneath
the cuticle of an healthy perfon, its flimulus in a
certain time produces the fame kind of morbid mo-
tions, by which itfelf was produced ; and hence a
iimilar kind is generated. See Seel. XXXIX. 6. I.

6. It is remarkable, that many of thefe contagi-
ous matters are capable of producing a fimilar dif-
eafe but once ; as the final 1-pox and meafles ; and
I fuppofe this is true of all thofe contagious dif-
eafes, which are fpontaneoufly cured by nature in a
certain time ; for if the body was capable of re-
ceiving the difeafe a fecond time, the patient muft
perpetually infed himfelf by the very matter, which

he

456 DISEASES OF SENSATION. SE£T. XXXIII. 2,

he has himfelf produced, and is lodged about him ;
and hence he could never become free from the
difeafe. Something fimilar to this is feen in the fe>
condary fever of the confluent fmall-pox ; there is
a great ablbrption of variolous matter, a very minute
part of which would give the genuine fmall-pox to
another peribnj but here it only Simulates the fyf-
tem into common fever ; like that which common
pus, or any other acrid material might occalion.

7. In the pulmonary confumption, where com-
mon matter is daily abforbed, an irritative fever
only, without new inflammation, is generally pro-
duced ; which is terminated like other irritative
fevers by fweats or loofe (tools. Hence it does not
appear, that this abforbed matter always ads as a
contagious material producing frefh inflammation or
new abfcefles. Though there is reafon to believe*
that the firft time any common matter is abforbed,
it has this eifecl, but not the fecond time, like the
variolous matter above mentioned.

This accounts for the opinion, that the pulmo-
nary confumption is fometirnes infectious, which
opinion was held by the ancients, and continues in
Italy at prefent ; and I have myfelf feen three or
four inftances, where a hulbaud and wife, who have
flept together, and have thus much received each
other's breath, who have infected each other, and
both died in confequence of the original taint or*
only one of them. This alfo accounts for the ab-
fcefles in various parts of the body, that are fome*
times produced after the inoculated fmall-pox is
terminated; for this fecond abforp'ion of variolous
matter afts like common matter, and produces only
irritative fever in thofe children, whofe conftituti-
ons have already experienced the abforption of com-
mon matter ; and inflammation with a tendency to
produce new abfcefles in thofe, whofe conftitutions

have

SECT. XXXIII. 2. DISEASES OF SENSATION. 457

' have not experienced the abforptions of coramoa
matter.

It is probable, that more certain proofs might
have been found to fhew, that common matter is
infectious the fir ft nine it is abfnrbed, tending to
produce fimilar abfceffes, but not the fecond time of
its abforption, if this fubject had been attended to.

8. 'I hefe contagious difeafes are very numerous,
as the plague, fmall-pox, chicken-pox, meafles, fcar-
let-fever, pemphigus, catarrh, chincough, venereal
difeafe, itch, trichoma, tinea. The infectious ma-
terial does not feem to be diflblved by the air, but
only mixed with it perhaps in fine powder, which
foon fubiides ; fince many of thefe contagions can
only be received by actual contact, and others of
them only at fmall diftances from the infected per-
fon, as is evident from many perfons having been
near patients of the fmall-pox without acquiring the
difeafe.

The reafon why many of thefe- difeafes are re-
ceived but once, and others repeatedly, is not well
underflood ; it appears to me, that the conftitution
becomes fo accuftomed to the iiimuii of thefe in-
fectious materials, by having once experienced them,
that though irritative motions, as hectic fevers, may
again be produced by them, yet no fenfation, and
in confequence no general inflammation fucceeds ;
as difagreeable fmells or taftes by habits ceafe to be
perceived ; they continue indeed to excite irritative
ideas on the organs of fenfe, but thefe are not fuc-
ceeded by fenfation.

There are rn.my irritative motions, which were
at firft fucceecled by fenfation, but which by fre-
quent repetition ceafe to excite fenfarion, as explain-
ed in Sect. XX. on Vertigo. And, that this circum-
ftance exifls in refpect to infectious matter appears
from a known fact ; that nurfes, who have had the
fmall-pox, are liable to experience fmall ulcers on

their

458 DISEASES OF SENSATION. SECT. XXXIII. 2.

their arms by the contact of variolous matter in
lifting their patients ; and that when patients, who
have formerly had the fmali pox have been inocu-
lated in the arm, a phlegmon, or inflamed fore, has
fucceeded, but no fubfequent fever. Which (hews,
that the contagious matter of the fmall-pox has not
loft its power of ilimulating the part it is applied
to, but that the general fyftem is not affeded in
confequence. See Sect. XII. 7. 6. XIX. 10.

9. From the accounts of the plague, virulent ca-
tarrh, and putrid dyfentery, it feems uncertain,
whether thefe difeafes are experienced more than
once ; but the venereal difeafe and itch are doubtlefs
repeatedly infedlious \ and as thefe difeafes are never
cured fpontaneoully, but require medicines, which
act without apparent operation, fome have fufpecl:-
cd, that the contagious material produces fimilar
matter rather by a chemical change of the fluids,
than by an animal procefs ; and that the fpecific me-
dicines deftroy their virus by chemically combining
with it. This opinion is fuccefsfully combated by
Mr. Hunter, in his Treatife on Venereal Difeafe,
Part I. c. i.

But this opinion wants the fupport of analogy,,
as there is no known procefs in animal bodies, which
is purely chemical, not even digeftion ; nor can any
of thefe matters be produced by chemical procefles.
Add to this, that it is probable, that the infects,
obferved in the puftules of the itch, and in the (tools
ot dyfenteric patients, are the confequences, and
not the caufes of thefe difeafes. And that the fpe-
cific medicines, which cure the itch and lues vene-
rea, as brim (lone arid mercury, adt only by increaf-
ing the abforption of the matter in the ulcufcles of
thofe difeafes, and thence clifpofmg them to heal';
which would other wife continue to fpread.

Why the venereal difeafe, and itch, and tenia, or
fcald head, are repeatedly contagious, while thofe

contagions

S*CT. XXXIII a. DISEASES OF SENSATION. 459

contagions attended with fever can be received but
once, feems to depend on their being rather local
difeafes than univerfal ones, and are hence not at-
tended with fever, except the purulent fever in their
laft llages, when the patient is deftroyed by them.
On this account the whole of the fyftem does not
become habituated to thefe morbid adions, fo as to
ceafe to be affected with fenfation by a repetition of
the contagion. Thus the contagious matter of the
Venereal difeafe, and of the tenia, affects the lym-
phatic glands, as the inguinal glands, and thofe
about the roots of the hair and neck, where it is
ar retted, but does not feem to affect the blood-
reffels, fmce no fever enfues.

Hence it would appear, that thefe kinds of con-
tagion are propagated not by means of the circula-
tion, but by fympathy of diftant parts with each
other ; fince if a diftant part, as the palate,
fhould be excited by fenfitive affociation into
the fame kind of motions, as the parts originally
affected by the contact of infectious matter ; that dif-
tant part will produce the fame kind of infectious
matter ; for every fecretion from the blood is formed
from it by the peculiar motions of the fine ex-
tremities of the gland, which fecretes it ; the vari-
ous fecreted fluids, as the biles faliva, gaftric juice,
Hot previouily exifting, as fuch, in the blood- vef-
fels.

And this peculiar fympathy between the genitals
the throat, owing to fenfitive affociation, ap-
pears not only in the production of venereal ulcers
in the throat, but in variety of other inttances, as
in the mumps, in the hydrophobia, fome coughs,
ftrangulation, the production of the beard, change
of voice at puberty. Which are further defcribed
inClafsIV. i. 2.7.

To evince that the production of fuch large quan-
tities of contagious matter, as are Teen in fome

H h variolous

460 DISEASES OF SENSATION. SKCT.XXXlTf 2.

variolous patients, fo as to cover the whole fkin
almoft with puflules, does not arife from any che-
mical fermentation in the blood, but that it i»
owing to morbid motions of the fine extremities
of the capillaries, or glands, whether thefe be rup-
tured or not, appears from the quantity of this
matter always cor ref ponding with the quantity of
the fever ; that is, with the violent exertions of thofe
glands and capillaries, which are the terminations
of the arterial fyftem.

The truth of this theory is evinced further by a
circumftance obferved by Mr. J. Hunter, in his
Treatife on Venereal Difeafe ; that in a patient, who
was inoculated for the fmall-pox, and who appear-
ed afterwards to have been previoufly infeded with
the meafles, the progrefs of the fmall-pox was de-
layed till the meafles had run their courfe, and that
then the fmall-pox went through its ufual periods.

Two fimilar cafes fell under m-y care, which I
(hall here relate, as it confirms that of Mr. Hunter,
and contributes to illuftrate this part of the theory
of contagious difeafes. I have tranfcribed the par-
ticulars from a letter of Mr. Lightwood of Yoxal*
the furgeon who daily attended them, and at my
requeft, after I had feen them, kept a kind of jour-
nal of their eafes.

Mifs H. and Mifs L. two fitters, the one about
four and the other about three years old,, were ino-
culated Feb. 7, 1791- On the loth there was a
rednefs on both arras difcernible by a glafs. On
the i ith their arms were fo much inflamed as to
leave no doubt of the infection having taken place.
On the 1 2th lefs appearance of inflammation on
their arms. In the evening Mifs L. had an erup-
tion, which refembled the meafles. On the I3th
the eruption on Mifs L. was very full on the face
and breaii, like the meafles, with confiderable fever.
It was now known, that the meafles were in a farm

houfe

SECT. XXXIII. 2. DISEASES OF SENSATION, 461

houfe in the neighbourhood. Mrfs H.'s arm lefs in-
flamed than yellerday. On the I4th Mifs L.'s fever
great, and the eruption univerfal. The arm appears
to be healed. Mifs H.'s arm fomewhat redder. They
were now put into fcparate rooms. On the i5th
Mifs L.'s arms as yefteiday. Eruption continues.
Mifs H.'s arms have varied but little i6th, the
eruptions on Mifs L. are dying away, her fever gone.
Begins to have a little rednefs in one arm at the
place of inoculation. Mifs H.'s arms get redder,
but fhe has no appearance of complaint. 2othy
Mifs L.'s arms have advanced flowly till this day,
and now a few puftules appear* Mifs H.'s arm has
made little progrefs from the i6th to this day, and
fiow {he has fome fever. 2ift5 Mifs L. as yefter-
day. Mifs H. has much inflammation, and an in-
Creafe of the red circle on one arm to the fize of
half a crown, and had much fever at night, with
fetid breath. 22d, Mifs L.'s puftules continue ad-
vancing. Mifs H.'s inflammation of her arm and
red circle increafes. A few red fpots appear in dif-
ferent parts with fome degree of fever this morningv
23d, Mifs L. has a larger crop of puftules. Mils
H. has fmall puftules and great inflammation of her
arms, with but one puftule likely to fuppurate. Af-
ter this day they gradually got well, and the puftules
difappeared.

In one of thefe cafes the meafles went through
their common courfe with milder fymptoms thaa
ufual, and in the other the meafly contagion feemed
juft fufficient to (top the progrefs of variolous con-
tagion, but without itfelf throwing the conflitution
into any diforder. At the fame time both the
meafles and fmall-pox feem to have been rendered
milder. Does not this give an idea, that if they
were both inoculated at the fame time, neither of
them might affect the patient ?

H h 2 From

462 DISEASES OF SENSATION. SECT. XXXIII. a.

From thefe cafes I contend, that the contagious
matter of thefe difeafes does nor affect the confuta-
tion by a fermentation, or chemical change of the
blood, becaufe then they muft have proceeded toge-
ther, and have produced a third fomething, not
exactly iimilar to either of them : but that they
produce new motions of the cutaneous terminations
of the blood- vefie Is, which for a time proceed daily
•with increafing activity, like forae paroxyfms of fe-
ver, till they at length fecrete or form a fimilar
poifon by thefe unnatural actions*

Now as in the meafles one kind of unnatural mo-
tion takes place, and in the fmaTl-pox another kind,
it is eafy to conceive, that thefe different kinds of
morbid motions cannot exift together ; and there-
fore, that that which has firft begun will continue
till the fyftem becomes habituated to the ftimulus
which occafions- it, and has ceafed to be thrown
into aclion by it; and then the other kind of ftimu-
lus will in its turn produce fever, and new kinds
of motions peculiar to itfelf.

10. On further considering the aclion of conta-
gious matter, fince the former part of this work was
fent to the prefs; where I have aliened, in Sect.,
XXII. 4. 3. that it is probable, that the variolous
matter is diffufed through the blood; I prevailed on:
my friend Mr. Power, furgeon at Bofworth in Lei-
cefterfhire to tryr whether the fmall-pox eould be
inoculated by ufing the blood of a variolous pati-
ent inftead of the matter from the puftules ; as I
thought fuch an experiment^ might throw fome light
at lead on this interesting fubject. The following,
is an extract from his letter ;—

**. March 1 1 r 1793- I inoculated two children,,
who had not had the fmall-pox, with blood ; which
was taken from a patient on the fecond day after the
eruption commenced, and before it was completed*
And at the fame time I inoculated myfelf with

blood

SECT. XXXIII. s. DISEASES OF SENSATION. 463

blood from the fame perfon, in order to compare
the appearances, which might arife in a perfon lia-
ble to receive the infection, and in one not liable to
receive it. On the fame day I inoculated four other
children liable to receive the infection with blood
taken from another perfon on the fourth day after
the commencement of the eruption. The patients
from whom the blood was taken had the difeafe
mildly, but had the moft puflules of any I could
felecl from twenty inoculated patients ; and as much
of the blood was infmuated under the cuticle as I
could introduce by elevating the (kin without draw-
ing blood ; and three or four fuch punctures
were made in each of their arms, and the blood
was ufed in its fluid ftate.

" As the appearances in all thefe patients, as
well as in myfelf, were fimilar, I fhall only mention
them in general terms. March 13. A flight fubcu-
ticular difcoloration, with rather a livid appearance,
without forenefs or pain, was vifible in them all,
as well as in my own hand. 15. The difcolo ration,
fomewhat lefs, without pain or forenefs. Some pa-
tients inoculated on the fame day with vanolous
matter have conliderable inflammation. 17. The
difcoloration is quite gone in them all, and from my
own hand, a dry mark only remaining. And they
were all inoculated on the iSth, with variolous mat-
ter, which produced the difeafe in them all."

Mr. Power afterwards obferves, that, as the pati-
ents from whom the blood was taken had the dif-
eafe mildly, it may be fuppofed, that though the
contagious matter might be mixed with the blood,
it might dill be in too dilute a (late to convey the
infection ; but adds at the fame time, that he has
dilute:! -recent matter with at leaf! five times its
quantity of water, and which has flill given the in-
feclion ; though he has fometimes diluted it fo far
as to fail.

The

464 DISEASES OF SENSATION. SECT. XXXIII, ».

The following experiments were inflituted at my
requeft by my friend Mr. Hadley, furgeon in Derby,
to afcertain whether the blood of a perfon in the
fmall-pox be capable of communicating the difeafe.
"Experiment lit. Oclober i8th, 1793. I took fome
blood from a vein in the arm of a perfon who had
the fmall-pox, on the fecond day of the eruption,
and introduced* a fmall quantity of it immediately
with the point of a lancet between the fcarf and
true fkin of the right arm of a boy nine years old
in two or three different places ; the other arm was
inoculated with variolous matter at the fame time.

** J9th. The puuv^ured parts of the right arm
were furrounded with fome degree of fubcuticular
inflammation, soth. The inflammation more con-
iiderable, with a flight degree of itching, but no
pain upon preflure. 21 ft. Upon examining the arm
this day with a lens I found the inflammation lefs
extenfive, and the rednefs changing to a deep yel-
low or orange-colour. 22d. Inflammation nearly
gone. 2jd. Nothing remained, except a flight dif-
coloration and a little fcurfy appearance on the
pun£lures. At the fame the inflammation of th$
arm inoculated with variolous matter was increafing
faft, and he had the difeafe mildly at the ufual
time.

" Experiment 2d. I inoculated another child
at the fame time and in the fame manner, with blood
taken on the firft day of the eruption ; but as the
appearance and effe&s were fimilar to thofe in the
preceding experiment, I (hall not relate them mi*
nutely. -^

«' Experiment 3d. October 2pth. Blood was
taken from a perfon who had the fmall-pox, on the
third day of the eruption, and on the fixth from the
commencement of the eruptive fever. I introduced
fome of it in its fluid flate into both arms of a boy
feven years old. 2ift. There appeared to be fome

inflammation.

Sacr. XXXIII. a. DISEASES OF SENSATION. 465

inflammation under the cuticle, where the punctures
xvere made, 22d. Inflammation more coniiderable.
23d. On this day the inflammation was fomewhat
greater, and the cuticle rather, elevated.

<c 24th. Inflammation much lefs, and only a brown
or orange colour remained. 25th. Scarcely any dif-
coloration left. On this day he was inoculated with
variolous matter, the progrefs of the infection went
on in the ufual way, and he had the fmall-pox very
favourably.

u At this time I was requefted to inoculate a
young peribn, who was thought to have had the
fmall-pox, but his parents were not quite certain ;
in one arm I introduced variolous matter, and in the
other blood, taken as in experiment 3d. On the
fecond day after the operation, the punclured parts
were inflamed, though I think the arm in which I
had inferted variolous matter was rather more fo
than the other. '* On the third the inflammation was
increafed, and looked much the fame as in the pre-
ceding experiment. 4th. The inflammation was
much diminimed, and on the 5th almoft gone. He
was expofed at the fame time to the natural infedti-
on, but has continued perfectly well.

" I have frequently obferved (and believe mod
practitioners have done the fame), that if variolous
matter be inferted in the arm of a perfon who has
previoufly had the fmall-pox, the inflammation
on the fecond or third days is much greater, than
if they had not had the difeafe, but on the fourth
or fifth it difappears.

" On the 23d I introduced blood into the arms
of three more children, taken on the third and
fourth days of the eruption. The appearances were
much the fame as mentioned in experiments firft and
third. They were afterwards inoculated with vari-
olous matter, and had the difeafe in the regular way.

« The

4*6 DISEASES OF SENSATION. SECT. XXXIII, 2.

" The above experiments were made with blood
taken from a fmall vein in the hand or foot of three
or four different patients, w^om I had at that time
under inoculation. They were feleded from 169,
as having the greateft number of puflules. The
part was wafhe.d with warrn water before the blood
was taken, to prevent the poffibility of any inatter
being mixed with it from the furfa.ce.1*

Shall we cpnclude frpm hence, that the variokms
matter never enters the blood-veflels ? but that the
morbid motions of the veffels of the {kin around the
infertipn of it continue to increafe in a larger and
larger circle for fix or feven days; that then their
quantity of morbid a&ion becomes great enough to
produce a fever-fit, and to affect the ftomach by
afibciation of rnptions ? and finally, that a fecond
aflbciation of motions is produced between the flo-
mach and the other parts of the {kin, inducing them
into morbid aclipns iirnUar to thofe of the circle
round the infertion of the variolous matter ? Many
more experiments and obfervatipns are required be*
fore this important queftion can be fatisfadority
anfwere.4'

It may be adduced, that the matter inferted into
the ikin of the arm frequently fwells the lymphatic;
in the axilla, that in that circumftance it feems to
be there ^rrefted in its progrefs,, and cannot be ima-
gined to enter the blood by that lymphatic gland
till the fwelling of it fubiides. Some other pbseno-
mena of the difeafe are more eafily reconcileable tot
this theory of fympathetic motions than to that of
abforptior\ ; as the time taken up between the in-
fertion of the matter, a,nd. the operation of it on the
fyilem, a$ mentioned above. For the circle around
the infertion is feen to increafe, and to inflame; and
I believe, undergoes a kind of diurnal paroxyfm of
torpor and palenefs with a fucceeding increafe of
adlion arid colour, like a topical fever-fit. Whereas

' I

SECT. XXXIII. a. DISEASES OF SENSATION. 467

if the matter is conceived to circulate for fix or
feven days with the blood, without producing dif-
order, it ought to be rendered milder, or the blood-
yeffels more familiarized to its acrimony.

It is much eafier to conceive from this docTtrine of
affociated or fympathetic motions of diilant parts of
the fyftem, how it happens, that the variolous iri-
fection can be received but once, as before ex-
plained ; than by fuppofing, that a change is ef-
fected in the mafs of blood by any kind of ferment-
ative procefs.

The curious circumftance of the two contagion$
of fmall-pox and meafles not adting at the fame
time, but one of them reding or fufpending its ac-
tion till that pf the other ceafes, may be much
eafier explained from fympathetic or aflbciated acti-
ons of the infecled part with other parts of the
iyitem, than it can. from fuppofing the two conta-
gions to enter the circulation.

The (kin of the face is fubjecl: to more frequent
yiciffitudes of heat and cold, from its expofure to
the open air, and is in confequence more liable to
fenfitive affociation with the ftomach than any ther
part of the furface of the body, becaufe their ac-
tions have been more frequently thus affociated.
Thus in a furfeit from drinking cold water, when
a perfon is very hot and fatigued, an eruption is
liable to appear on the face in confequence of this
fympathy. In the fame manner the rofy eruption on
the faces of drunkards more probably arifes from
the fympathy of the face with the ftorjiach, rather
than between the face and the. liver, as is generally
fuppofed.

This fympathy between the ftomach and the fkin
of the face is apparent in the eruption of the fmall-
pox ; fmce, where the difeafe is in considerable
quantity, the eruption of the face firft fucceeds the
ficknefs of the ftomach. In the natural difeafe the

ftomach

468 DISEASES OF SENSATIOtf. SECT. XXXIlJ. 3.

ftomach feems to be frequently primarily affedted,
either alone or along with the tonfils, as the matter
feems to be only diffufed in the air, and by being
mixed with the faliva, or mucus of the tonfils, to
be fwallowed into the ftomach.

After fome days the irritative circles of motions
become difordered by this new ftimulus, which acls
upon the mucous lining of the ftomach ; and fick-
nefs, vertigo, and a diurnal fever fucceed. Thefe
difordered iiritative motions become daily increafed
for two or three days, and then by their increafed
a&ion certain fenfitive motions, or inflammation, is
produced, and at the next cold fit of fever, when
the ftomach recovers from its torpoi?, an inflamma-
tion of the external fkin is formed in points (which
afterwards fuppurate), by fenfitive aflfociarion, in the
fame manner as a cough is produced in coufequence
of expofing the feet to cold, as defcribed in Se£.
XXV. I. i. and Clafs IV. 2. i. 7. If the inoculated
fkin of the arm, as far as it appears inflamed, was
to be cut out, or deftroyed by cauflic, before the
fever commenced, as fuppofe on the fourth day after
inoculation, would this prevent the difeafe ? as it is
fuppofed to prevent the hydrophobia.

III. i. Where the new vefieis, and enlarged old
ones, which conditute inflammation, are not fo haf-
tily diftended as to burft, and form a new kind of
gland for the fecretion of matter, as above menti-
oned ; if fuch circumftances happen as diminifh the
painful fenfatioii, the tendency to growth ceafes, and
by and by an abforption commences, not only of
the fuperabundant quantity of fluids depofited in
the inflamed part, but of the folids likewife, and this
even of the hardelt kind.

Thus during the growth of the fecond fet of
teeth in children, the roots of the firft fet are to-
tally abforbed, till at length nothing of them re-
mains but the crown $ though a few weeks before,

SF.CT. XXXIII. y. DISEASES OF SENSATION.- 469

*f they are drawn immaturely, their roots are found
complete. Similar to this Mr. Hunter has obferv-
ed, that where a dead piece of bone is to exfoliate,
or to feparate from a living one, the dead part
does not putrefy, but remains perfe&iy found, while
the furface of the living part of the bone, which is
in contact with the dead part, becomes abforbed,
and thus effects its feparaiion. Med. Comment.
Edinb. V. 1.425. In the fame manner the calca-
reous matter of gouty concretions, the coagulable
lymph depofited on inflamed membranes in rheu-
matifm and extravafated blood become abforbed;
which are all as folid and as indiflbluble materials as
the new veflels produced in inflammation.

This abforption of the new veflels and depofited
fluids of inflamed parts is called resolution : it Is
produced by firfl ufing fuch internal means as de-
creafe the pain of the part, and in confequence its
new motions, as repeated bleeding, cathartics, dilu-
ent potations, and warm bath.

After the veflels are thus emptied, and the ab-
forption of the new veflels and depofited fluids is
evidently begun, it is much promoted by (Umulating
the part externally by folutions of lead, or other
metals, and internally by the bark, and fmali doles
of opium. Hence when an ophthalmy begins to
become paler, any acrid eye-water, as a foiution of
fix grains of white vitriol in an ounce of water,
haflens the abforption, and clears the eye in a very
fhort time. But the fame application ufed a few
days fooner would have increafed the inflammation.
Hence after evacuation opium in frnall cjoks may
contribute to promote the abforption of fluids de-
pofited on the brain, as obferved by Mr. Bromfield
in his treatife of furgery.

2. Where an abfcefs is formed by the rupture of
thefe new veflels, the violence of inflammation
ceafes, and a new gland feparates a material called

pus;

470 DISEASES OF SENSATION. SECT. XXXIII. 3.

pus : at the fame time a lefs degree of inflammation
produces new vefiels called vulgarly proud flefh ;
which, if no bandage confines its growth, nor any
other circum (lance promotes absorption in the
wound, would rife to a great height above the ufual
fize of the parr.

Hence the art of healing ulcers confifts in pro-
ducing a tendency to abforption in the wound
greater than the depofuion. Thus when an ill-
conditioned ulcer feparates a copious and thin dif-
charge, by the ufe of any (limulus, as of falls of
lead, or mercury, or copper externally applied, the
difcharge becomes dtminifhed in quantity, and be-
comes thicker, as the thinner parts are firft ab-
forbed. ». •*

But nothing fo much contributes to increafe the
abforption in a wound as covering the whole limb
above the fore with a bandage, which fhould be
fpread with fome plafter, as with emplaftrum de
mink), to prevent it from flipping. By this artifi-
cial tight nefs of the (kin, the arterial pulfations aft
with double their ufual powder in promoting the
afcending current of the fluid in the valvular iym*
phatics.

Internally the abforption from ulcers fhould be
promoted firft by evacuation, then by opium, bark,
mercury, fteel.

3. Where the inflammation proceeds with greater
violence pj* rapidity, that is>, when by the painful
fenfation a more inordinate activity of the organ is
produced, and by this great activity an additional
quantity of painful fenfation follows in an increafmg
ratio, till the whole of the fenfqrial power, or fpirit
of animation, in the part becomes exhaufted, a mor-
tification enfues, as in a carbuncle, in inflamma-
tions of the bowels, in the extremities of old people,
or. in the limbs of thofe who are brought near a
fire after having been much benumbed with cold.

And

SECT. XXXIII. 4- DISEASES OF SENSATION. 471

And fvom hence it appears, why weak people are more
fubject to mortification than ftrong ones, and why
in weak perfons lefs pain will produce mortifica-
tion, namely, becaufe the fenibrial power is fooner
exhaufted by any excels of activity* I remember
feeing a gentleman who had the preceding day tra-
velled twro ftages in a chaife with what he termed
a bearable pain in his bowels ; which when I faw
him had ceafed rather fuddenly, and without a paf-
£age through him ; his pulfe was then weak, though
not very quick ; but as nothing Which he fwallowed
would continue in bis ftomach many minutes, I con*
eluded that the bowel was mortified -r he died on
the next day. It is ufual for patients finking under
the fmall-pox w7ith mortified puilules, and with
purple fpots intermixed, to complain of no pain,
but to fay they are pretty well to the laft momeut.

IV. When the motions of any part of the fyftem,
in confequence of previous torpor, are performed
with more energy than in the irritative fevers, a
difagreeable lenfation is produced, and new a&ions
of fome part of the fyftem commence in confequence
of this fenfation conjointly w ith the irritation : which
motions conftitute inflammation. If the fever be
attended with a flrong pulfe, as in pkurify, or rheu-
rnatifm, it is termed fynocha fenfitiva, or fenfuive
fever with ftrong pulfe ; which is ufually termed in-
flammatory fever. If it be attended with weak
pulfe, it is termed typhus feniitivus, or fenfitive. fever
with weak pulfe, or typhus gravior, or putrid ma-
lignant fever.

The fynocha fenfitiva, or fenfitive fever with
ftrong pulfe, is generally attended with fome topical
inflammation, as in peripneumony, hepatitis, and is-

accompanied

DISEASES OF SENSATION. SECT. XXXIII. 4,

accompanied with much coagulable lymph, or fize ;
which rifes to the furface of the blood, when taken
into a bafon, as it cools ; and which is believed to
be the increafed mucous fecretion from the coats of
the arteries, infpiffated hy a greater abforption of its
aqueous and faline parts, and perhaps changed by
its delay in the circulation.

The typhus fenfuivus, or fenfitive fever with weak
pulfe, is frequently attended with delirium, which
is caufed by the deficiency of the quantity of fenfo«-
rial power, and with variety of cutaneous erup*
tions.

Inflammation is caufed by the pains occafioned
by excefs of aftion, and not by thofe pains which
are occafioned by defect of action, Thefe morbid
actions, which are thus produced by two fenforial
powers, viz. by irritation and fenfation, fecrete new
living fibres, which elongate the old veflels, or form
new ones, and at the fame time much heat is evolved
from thefe combinations. By the rupture of thefe
velfels, or by a new conftruclion of their apertures,
purulent matters are fecreted of various kinds ; which
are infectious the firft time they are applied to the
fkin beneath the cuticle, or fwallowed with the fa-
liva into the ftomach. This conragion acts not by
its being abforbed into the circulation, but by the
fympathies, or aflbciated actions, between the part
firft Simulated by the contagious mattsr and the
other parts of the fyftem. Thus in the natural
fmall-pox the contagion is fwallowed with the faliva,
and by its flimulus inflames the ftomach ^ this vari-
oloos inflammation of the ftomach increafes every
day, like the circle round the pundlure of an ino-
culated arm, till it becomes great enough to difordef
the circles of irritative and fenfitive motions, and
thus produces fever-fits, with ficknefs and vomiting.
Laftly, after the cold paroxyfm, or fit of torpor, of
the ftomach has increafed for two or three fuccef-

live

SHOT. XXXIII. 4. DISEASES OF SENSATION. 473

five days, an inflammation of the fkin commences
in points ; which generally firft appear upon the
face, as the aflbciated addons between the fkin of
the face and that of the ftomach have been more
frequently exerted together than thofe of any other
parts of the external furface.

Contagious matters, as thofe of the meafles and
fmall-pox, do not ad upon the fyftem at the fame
time ; but the progrefs of that which was laft re-
ceived is delayed, till the a&ion of the former in-
fedion ceafes. All kinds of matter, even that from
common ulcers, are probably contagious the firfl
time they are inferted beneath the cuticle or fwal-
lowed into the ftomach ; that is, as they were form-
ed by certain morbid actions of the extremities of
the veflels, they have the power to excite fimilar
morbid actions in the extremities of other veflels,
to which they are applied ; and thefe by fympathy,
or affociafions of motion, excite fimilar morbid ac-
tions in diftant parts of the fyflem, without entering
the circulation -9 and hence the blood of a patient
in the {mall-pox will not give that difeafeby inocu-
lation to others.

When the new fibres or veflels become again ab-
forbed into the circulation, the inflammation ceafes ;
which is promoted, after fufficient evacuations, by
external flimuiants and bandages: but where the
aclion of the veflels is very great, a mortification of
the part is liable to enfue, owing to the exhaufiioiji
of fenforial power ; which however occurs in weak
people without much pain., and without very violent
previous inflammation ; and, like partial paralyfis,
may be efteemed one mode of natural death of old
people, a part dying before the whole.

SECT.

474 DISEASES OF VOLITION. SECT. XXXIV.

SECT, xxxivi

DISEASES OF

j. i. Volition defined. Motions termed involuntary
are caused by volition* Defires oppofed to each other.
Deliberation, 4fs between two hay -cocks. Saliva
fwallow'ed again/I Qn£$ defire. Voluntary motions
dijlinguijhed from thofe ajjociated with /enfttive mo-
tions. 2. Pains from excefs, and from defect of
motion* No pain is felt during vehement voluntary
exertion ; as in cold Jits of ague, laboitr -pains, Jlran-
gury, tenefmus, vomiting, rejllejjnefs in fevers, con-
vuljion of a wounded mufcle. 3. Of holding the
breath and f creaming in pain ; why fwine and dogj
cry out in pain y and not Jheep and horfes. Of grin-
ning and biting in pain ; why mad animals bite others,
4. Epileptic convulfions explained, why the jits begin
with, quivering of the under jaw, biting the tongue,
andfetting the teeth ; why the convuljive motions art
alternately relaxed* The phenomenon of laughter1
explained. Why children cannot tickle themf elves.
How fome have died from immoderate laughter., 5.
Of cataleptic fpafms, of the locked jaw, of painful
cramps. 6. Syncope explained. Why no external
objecls are perceived in fyncope. 7. Of pal fy and
apoplexy from violent exertions. Cafe of Mrs. Scot*
From dancing, f eating, fwimming. Cafe of Mr*>
Nairn. Why palfies are not always immediately pre-
ceded by violent exertions. Palfy and epilepfy from
difeafed livers. Why the right arm more frequently
paralytic than the left. How paralytic limbs regain
their motions. II. . Dif safes of the fenfual motions

from

SECT. XXXIV. i. DISEASES OF VOLITION. 47*

from excefs or defeft of voluntary exertion. I. Mud-
nefs. 2. Diftinguifhed from delirium. 3. Why man-
kind more liable to infanity than brutes. 4. Sufpicion.
Want of Jhame, and of cleanliness. 5. They bear
cold, hunger, and fatigue. Charles XII. of Sweden.
6. Pleasurable delirium, and infanity. Child riding
on ajiick. Pains of martyrdom not felt. 7. Dropfy.
8. Injlammation cured by infanity. III. I. Pain re-
lieved by reverie. Reverie is an exertion of volun-
tary and fenfttive motions, z. Cafe of reverie. 3.
Lady fuppofed to have two fouls. 4. Methods of
relieving fain.

I. i. BEFORE we commence this Seftion on
Difeafed Voluntary Motions, it may be neceffary to
premife, that the word volition is not ufed in this
work exactly in its common acceptation. Volition
is faid in Seftion V. to bear the fame analogy to
defire and averfion, which fenfation does to pleafure
and pain. And hence that, when deiire or averfion
produces any action of the mufcular fibres, or of
the organs of fenfe, they are termed volition ; and
the actions produced in confequence are termed vo-
luntary actions. Whence it appears, that motions
of our mufcles or ideas may be produced in confe-
quence of defire or averfion without our having the
power to prevent them, and yet thefe motions may
be termed voluntary, according to our definition of
the word ; though in common language they would
be called involuntary.

The objects of defire and averfion are generally
at a diftance, whereas thofe of pleafure and pain
are immediately acUng upon our organs. Hence,
befoie defire or averfion are exerted, fo as to caufe
any actions, there is generally time for deliberation ;
which confifts in difcovering the means to obtain
the object of defire, or to avoid the object of aver-
fion ; or in examining the good or bad confequences

VOL. I. I i which

476 DISEASES OF VOLITION. SECT. XXXIV. i>

which may refuh from them. In this cafe it is
evident, that we have a power to delay the pro-
pofed adion, or to perform it ; and this power of
choofmg, whether we (hall aft or not, is in com-
mon language expreflfed by the word volition, or
will. Whereas in this work the word volition means
fimpty the active ftate of the fenforial faculty in pro-
ducing mqtion in confequence of defire or averfion :
Whether we have the power of reftraining that ac-
tion, or not ; that is, whether we exert any actions
in confeque^ee of oppofite defires, or averfions,. or
not.

For if the objects of defire or averfion are pre-
fent, there is no neceflity to inveftigate or compare
the means of obtaining them, nor do we always de-
liberate about their confequences ; that is, no deli-
beration neceflarily intervenes, and in confequenee
the power of choofing to aft or not is not exerted.
It is probable, that this twofold ufe of the word
volition in all languages has confounded the meta-
phyficians, who have difputed about free will and
neceflity. Whereas from the above analyfis it would
appear, that during our fleep, we ufe no voluntary
exertions at all ; and in our waking hours, that they
are the confequenee of defire or averfion.

To will is to aft in confequenee of defire ; but
to defire means to defire fomething, even if that
fomething be only to become free from the pain,
which caufes the defire ; for to defire nothing is
not to defire ; the word defire, therefore, includes
both the adtion and the objedl or motive ; for the
objeft and motive of defire are the fame thing.
Hence to defire without an object, that is, without
a motive, is a folecifm in language. As if one fhould
afk, if you could eat without food, or breathe with-
out air.

From this account of volition it appears, that con-
vulfions of the mufcles, as in epileptic fits, may in
the tommon fenfc of that word be termed involun- •

taryj

SECT. XXXIV. i. DISEASES OF VOLITION. 477

tary ; becaufe no deliberation is interpofed between
the defire or averfion and the confequent a&ion ^
but in the fenfe of the word, as above defined, they
belong to the clafs of voluntary motions, as deli-
vered in Vol. II. Clafs III. If this ufe of the word
be difcoidant to the ear of the reader, the terra
morbid voluntary motions, or motions in confe-
quence of averfion, may be fubftituted in its (lead.

If a perfon has a delire to be cured of the ague,
and has at the fame time an averfion (or contrary
defire) to fwallowing an ounce of Peruvian bark; he
balances defire againft defire, or averfion againft
averfion; and thus he acquires the power of choof-
ing, which is the common acceptation of the word
willing. But in the cold fit of ague, after having
difcovered that the a6l of fhuddering, or exerting
the fubcutaneous mufcles, relieves the pain of cold;
he immediately exerts this aclof volition, andfhud-
ders, as foon as the pain and confequent averfion
return, without any deliberation intervening ; yet is
this aci, as well as that of fwallowing an ounce of the
bark, caufed by volition ; and that even though he
endeavours in vain to prevent it by a weaker con-
trary volition. This recalls to our mind the ftory
of the hungry 'afs between two hay-ftacks, where
the two defires are fuppofed fo exactly to counteract
each other, that he goes to neither of the flacks,
but perifhes by want. Now as two equal and op-
pofite defires are thus fuppofed to balance each
other, and prevent all action, it follows, that if one
of thefe hay-ftacks was fuddenly removed, the afs
would irrefiftibly be hurried to the other, which
in the common ufe of the word might be called an
involuntary a& ; but which, in our acceptation of
it, would be clalfed amongft voluntary adlions, as
above explained.

Hence to deliberate is to compare oppofmg defires
or averfions, and that which is the mod intereiling

Ii 3 at

47§ DISEASES OF VOLITION. SECT. XXXIV. i.

at length prevails, and produces a$ion. Similar
to this, where two pains oppofe each other, the
ftronger or more interefting one produces adion ;
as in pleuiify the pain from fuffocation would pro-
duce expanfion of the lungs, but the pain occafi-
oned by extending the inflamed membrane, which
lines the c heft, oppofes this expanfion, and one or
the other alternately prevails.

When any one moves his hand quickly near ano-
ther perf©n's eyes, the eye-lids inftantly clofe ; this
a& in common language is termed involuntary, as
we have not time to deliberate or to exert any con*
trary defire or averfion, but in this work it would
be termed a voluntary aft, becaufe it is caufed by
the faculty of volition, and after a few trials the
niclitation can be prevented by a contrary or op*
pofing volition.

The power of oppofing volitions is beft exem-
plified in the ftory of Mutius Scaevola, who is faid
to have thrufl his hand into the fire before Por-
fenna, and to have fuffered it to be confumed for
having failed him in his attempt on the life of that
prince. Here the averfion for the lofs of fame,
or the unfatisfied defire to ferve his country, the
two prevalent enthufiafms at that time, were more
powerful than the defire of withdrawing his hand,
which muft be occafioned by the pain of combufti-
on j of thefe oppofing volitions

Vicit amor patriac, laudumque immenfa cupi do.

If any one is told not to fwallow his faliva for
a minute, he foon fwallows it contrary to his will,
in the common fenfe of that word ; but this alfo is
a voluntary a&ion, as it is performed by the faculty
of volition, and is thus to be underllood. When
the power of volition is exerted on any of our fenfes,
they become more acute, as in our attempts to hear

7 fmall

SECT. XXXIV. i. DISEASES OF VOLITION. 479

fmall noifes in the night. As explained in Section
XIX. 6. Hence by. our attention to the fauces from
our defire not to fwallow our laliva ; the fauces be-
come more ferifible ; and the flimulus of the faliva
is followed by greater fenfation, and confequent de-
fire of fwallowing it. So that the defire or volition
in confequence of the increafed fenfation of the fa-
liva is more powerful, than the previous defire not
to fwallow it. See Vol. II. Deglutitio invita. In
the fame manner if a modeft man wifhes not to
want to make water, when he is coiifined with
ladies in a coach or an aiTembly-room ; that very
act of volition induces the circumflance, which he
wifhes to avoid, as above explained ; infomuch that
I once faw a partial infanity, which might be called
a voluntary diabetes, which was occafioned by the
fear (and confequent averfion) of not being able to
make water at all.

It is further neceiTary to obferve here, to prevent
any confufion of voluntary, with fenlitive, or affo-
ciate motions, that in all the inflances of violent
efforts to relieve pain, thofe efforts are at firft vo-
luntary exertions ; but after they have been fre-
quently repeated for the purpofe of relieving certain
pains, they become affociated with thofe pains, and
ceafe at thofe times to be fubfervient to the will ; as
in coughing, fneezing, and flrangury. Of thefe mo-
tions thofe which contribute to remove of diflodge
the offending caufe, as the actions of the abdominal
mufcles in parturition or in vomiting, though they
were originally excited by volition, are in this work
termed fenfuive motions ; but thofe actions of the
mufcles or organs of fcnfe, which do not contri-
bute to remove the offending caufe, as in general
convulfions or in madnefs are in this work termed
voluntary motions, or motions in confequence of
averfion, though in common language they are call-
ed involuntary ones. Thofe fenfitive unreftraiuable

actions,

480 DISEASES OF VOLITION. SECT. XXXIV. i,

actions, which contribute to remove the caufe of
pain are uniformly and invariably exerted, as in
coughing or fneezing ; but thofe motions which are
exerted in confequence of averfion without contri-
buting to remove the painful caufe, but only to pre-
Srent the fenfation of it, as in epileptic, or catalep-
tic fits are not uniformly and invariably exerted,
but change from one fet of mufcles to ano-
ther, as will be further explained; and may by this
criterion alfo'be diflinguifhed from the former.

At the lame time thofe motions, which are ex-
cited by perpetual ftimulus, or by aflbciation with
each other, or immediately by pleafurable or pain-
ful fenfation, may properly be termed involuntary
motions, as thofe of the heart and arteries ; as the.
faculty of volition feldom affects thofe, except when
it exifts in unnatural quantity, as in maniacal peo-
ple.

2. It was obferved in Section IV. on the Produc-
tion of Ideas, that thofe parts of the fyftem, which
are ufually termed the organs of fenfe, are liable
to be excited into pain by the excels of the ftimu-
lus of thofe objects, which are by nature adapted
to affeft them ; as of too great light, found, or
preflure. But that thefe organs receive no pain
from the defect or abfence of thefe ftimuli, as in
darknefs or filence. But that our other organs of
perception, which have generally been called appe-
tites, as of hunger, thirft, want of heat, want of
freih air, are liable to be affected with pain by the
defect, as well as by the excefs of their appropri-
ated ftimulL

This excefs or defect of itimulus is however to
be confidered only as the remote caufe of the pain,
the immediate caufe being the excefs or defe6t of the
natural action of the affected part, according to
Sect, IV. 5. Hence all the pains of the body may

be

SECT. XXXIV. i. DISEASES OF VOLITION. 481

foe divided into thofe from excefs of motion, and
thofe from deleft of motion ; which diftin&ion is
of great importance in the knowledge and the cure
of many diieafes. For as the pains from excefs of
motion either gradually fublide, or are in general
fucceeded by inflammation ; fo thofe from deredt of
motion either gradually fubfide, or are in general
fucceeded by convulfion, or madnefs. Thefe pains
are eaiily diftinguifhable from each other by this
circumftance, that the former are atr^n Jed with heat
of the pained part, or of the whole body; whereas
the latter exifts without increafe of heat in the
pained part, and is generally attended with coldnefs
of the extremities of the body ; which is the true
criterion of what have been called nervous pains.

Thus when any acrid material, as muff or lime,
falls into the eye, pain and inflammation and heat
are produced from the excefs of ftimulus ; but vio-
lent hunger, hemicrania, or the clavus hyftericus,
are attended with coldnefs of the extremities, and
defecl: of circulation. When we are expofed to
great cold, the pain we experience from the defi-
ciency of heat is attended with a quiefcence of the
motions of the vafcular fyftem ; fo that no inflam-
mation is produced, but a great defire of heat, and
a tremulous motion of the fubcutaneous mufcles,
which is properly a convulfion in confequence of
this pain from defecl: of the itimulus of heat*

It was before mentioned, that as fenfation con-
fifts in certain movements of the fenforium, beginr
ning at fome of the extremities of it, and propa-
gated to the central parts of it ; fo volition con-
fids of certain other movements of the fenforium,
commencing in the central parts of it, and propa-
gated to fome of its extremities. This idea of
thefe two great powers of motion in the animal
machine is confirmed from obferving, that they ne-
ver

48a DISEASES OF VOLITION. SECT. XXXIV. i.

ver exift in a great degree or univerfally at the
fame time ; for while we ilrongly exert our volun-
tary motions, we ceaie to feel the pains or uneafi-
nefles, which occafioned us to exert them.

Hence during the time of fighting with fids or
fwords no pain is felt by the combatants, till they
ceafe to exert themfelves. Thus in the beginning
of ague fits the painful fenfation of cold is dimi-
nifhed, while the patient exerts himfelf in the fhi-
vering and gnafhing of his teeth. He then ceafes
to exert himfelf, and the pain of cold returns ; and
he is thus perpetually induced to reiterate thefe
exertions, from which he experiences a temporary
relief. The fame occurs in labour-pains, the exer-
tion of the parturient woman relieves the violence
of the pains for a time, which recur again foon after
fhe has ceafed to ufe thofe exertions. The fame
is true in many other painful difeafes, as in the
ftrangury, tenefmus, and the efforts of vomiting ; all
thefe difagreeable fenfations are diminifhed or re-
moved for a time by the various exertions they
occafioo, and recur alternately with thofe exerti-
ons.

The reftleffnefs in fome fevers is an almoft perpe-
tual exertion of this kind, excited to relieve fome
difagreeable fenfations ; the reciprocal oppofite exer-
tions of a wounded worm, the alternate emproftho-
tonos and opifthotonos of fome fpafmodic difeafes,
and the intervals of all convulfions, from whatever
caufe, feem to be owing to this circumflauce of the
laws of animation ; that great or univerfal exertion
cannot exift at the fame time with great or uni-
verfal fenfation, though they can exift reciprocally ;
which is probably refolvable into the more general
law, that the whole ienforial power being expended
in one mode of exertion, there is none to fpare for
any other. Whence fyncope, or temporary apo-
plexy, fucceeds to epileptic convulfions.

3. Hence

SECT.XXXtV. i. DISEASES OF VOLITION, 4«5

3. Hence when any violent pain afflicts us, of
which we can neither avoid nor remove the caufe,
we foon learn to endeavour to alleviate it, by ex-
erting fome violent voluntaiy effort, as mentioned
above ; and are naturally induced to ufe thofe muf-
cles for this purpofe, which have been in the early
periods of our lives mod frequently or mod power-
fully exerted.

Now the firft mufcles, which infants ufe moft
frequently, ate thofe oi: refpi ration ; and on this ac-
count we gain a habit of hoU iug our breath, at
the fame time that we ufe great efforts to exclude
it, for this purpofe of alleviaiing unavoidable pain;
or we prefs out our breath through a fmall aperture
of the larynx, and fcream violently, when the pain
is greater than is relievable by the former mode of
exertion. Thus children fcream to relieve any pain
either of body or mind, as from anger, or fear of
being beaten.

Hence it is curious to obferve, that thofe animals,
who have more frequently exerted their mufcles of
refpiration violently, as in talking, barking, or
grunting, as children, dogs, hogs, fcream much
more, when they are in pain, than thofe other ani-
mals, who ufe little or no language in their com-
mon modes of life ; as horfes, iheep, and cows.

The next moft frequent or mod powerful efforts,
which infants are firft tempted to produce, are thofe
with the mufcles in biting hard fubitances ; indeed
the exertion of thefe mufcles is very powerful in
common maftication, as appears from the pain.
we receive, if a bit of bone is unexpectedly
found amongft our fofter food ; and further ap-
pears from their a&ing to fo fo great mechanical
difadvantage, particularly when we bite with the
incilores, or canine teeth, which are firft formed,
and thence are firft ufed to violent exertion.

Hence

484 DISEASES OF VOLITION. SECT. XXXIV. K

Henee when a perfon is in great pain, the caufe
of which he cannot remove, he fets his teeth firmly
together, or bites fome fubftance between them with
great vehemence, as another mode of violent exer-
tion to produce a temporary relief. Thus we have
a proverb where no help can be had in pain, «' to
grin and abide;" and the tortures of hell are faid
to be attended with " gnafhing of teeth."

Hence in violent fpafmodic pains I have feen peo-
ple bite not only their tongues, but their arms or
fingers, or thofe of the attendants, or any object
which was near them ; and alfo ftrike, pinch, or
tear, others or themfelves, particularly the part of
their own body, which is painful at the time. Sol-
diers, who die of painful wounds in battle, are faid
in Homer to bite the ground. Thus alfo in the
bellon, or colica faturnina, tr\e patients are faid to
bite their own flefh, and dogs in this difeafe to bite
tip the ground they lie upon. It is probable that
the great endeavours to bite in mad dogs, and the
violence of other mad animals, is owing to the fame
caufe.

4. If the efforts of our voluntary motions are
exerted with ftill greater energy for the relief of
fome difagreeable fenfation, convulfions are produc-
ed ; as the various kinds of epilepfy, and in fome
hyfteric paroxyfms. In all thefe difeafes a pain or
difagreeable fenfation is produced, frequently by
worms, or acidity in the bowels, or by a difeafed
nerve in the fide, or head, or by the pain of a dif-
eafed liver.

In fome coaftitutions a more intolerable degree
of pain is produced in fome p^rt at a diflance from
the caufe by feniitive affociation, as before explain-
ed ; thefe pains in fuch conilitutions arife to fo great
a degree, that I verily believe no artificial tortures
could equal fome, which I have witneffed ; and am
confid-ent life would not have long been preferved,

unlefs

SECT. XXXIV. i. DISEASES OF VOLITION. 4.^5

unlefs they had been foon diminifhed or removed
by the univerfal convulfion of the voluntary moti-
ons, or by temporary rnadnefs.

In fome of the unfortunate patients I have ob-
ferved, the pain has rifen to an inexpreflible degree,
as above defcribed, before the convulfions have fu-
pervened ; and which were preceded by fcreaming,
and grinning j in others, a$ in the common epilepfy,
the convulfion has immediately fucceeded the com-
mencement of the difagreeable fenfations ; and as
a ftupor frequently fucceeds the convulficns, they
only feemed to remember that a pain at the ftomach
preceded the fit, or fome other uneafy feel ; or
more frequently retained no memory at all of the
immediate caufe of the paroxyfni. But even in this
kind of epilepfy, where the patient does not recol-
lect any preceding pain, the paroxyfms generally are
preceded by a quivering motion of the under jaw,
with a biting of the tongue; the teeth afterwards
become prefled together with vehemence, and the
eyes are then convulfed, before the commencement
of the univerfal convulfion ; which are all efforts to
relieve pain.

The reafon why thefe convulfive motions are al-
ternately exerted and remitted, was mentioned above,
and in Se&. XII. j. 3. when the exertions are fuch
as give a temporary relief to the pain, which ex-
cites them, they ceafe for a time, till the pain is
again perceived; and then new exertions are pro-
duced for its relief. We fee daily examples of this
in the loud reiterated laughter of fome people ; the
pleafurable fenfation, which excites this laughter,
arifes for a time fo high as to change its name and
become painful : the convulfive motions of the re-
fpiratory mufcles relieve the pain for a time ; we
are, however, unwilling to lofe the pleafure, and
prefently put a flop to this exertion, and immedi-
ately the pleafure recurs, and again as inftantly rifes

into

486 DISEASES OF VOLITION. SECT. XXXIV. i.

into pain. All of us have felt the pain of immo-
derate laughter; children have been tickled into con-
vulfions or the whole body ; and others have died
in the act of laughing; probably from a paralyhs
fucceeding the long continued actions of the mufcles
of refpiration.

Hence we learn the reafon, why children, who
are fo eafily excited to laugh by the tickling of other
people's fingers, cannot tickle themfelves into laugh-
ter. The exertion of their hands in the endeavour
to tickle themfelves prevents the neceffity of any
exertion of the refpiratory mufcles to relieve the ex-
cefs of pleafarable atfedion. See Sect. XVII. 3. 5.

Chryfippus is recorded to have died laughing,
when an afs was invited to fup with him. The fame
is related of one of the popes, who, when he was
ill, faw a tame monkey at his bedfide put on the
holy tiara. Hall. Phyf. T. III. p. 306.

There are inilances of epilepfy being produced by
laughing recorded by Van^Swieten, T. III. 402 and
308. And it is well known, that many people have
died inftantaneoufly from the painful excefs of joy,
which probably might have been prevented by the
pcertions of laughter.

Every combination of ideas, which we attend to,
pccafions pain or pleafure; thofe which occaiion
pleafure, furnifh either focial or felfifh pleafure, ei-
^her malicious or friendly, or lafcivious, or fublime
pleafure; that is, they give us pleafure mixed with
Other emotions, or they give us unmixed pleafure,
without occasioning any other emotions or exertions
at the fame-time. This unmixed pleafure, if it be
great, becomes painful, like all other animal motions
from flimuli of" every kiad ; and if no other exer-
tions are occafioned at the fame time, we ufe the
exertioa of laughter to relieve this pain. Hence
laughter is occafioned by fuch wit as excites fimple
pleafure without any othex emotion, fuch as pity,

love,

SECT. XXXI V.i. DISEASES OF VOLITION.

love, reverence. For fublime ideas are mixed with
admiration, beautiful ones with love, new ones with
lurprife ; and thefe exertions of our ideas prevent
the aclion of laughter from being neceflary to re-
lieve the painful pleafure above defcribed. Whence
laughable wit confifts of frivolous ideas, without con-
nections of any confequence, fuch as puns on words,
or on phrafes, incongruous junctions of ideas; on
which account laughter is fo frequent in children.

Unmixed pleafure lefs than that, which taufes
laughter, caufes fleep, as in linging children to fleep,
or in flight intoxication from wine or food. See Se&.
XVIII. 12.

5. If the pains, or difagreeable fenfations, above
defcribed, do not obtain a temporary relief from
thefe convulfive exertions of the mufcles, thofe con-
vuliive exertions continue without remiilion,and one
kind of catalepfy is produced. Thus when a nerve
or tendon produces great pain by its being inflamed
or wounded, the patient fets his teeth firmly toge-
ther, and grins violently, to diminilh the pain ; and
if the pain is not relieved by this exertion, no relax-
ation of the maxillary mufcles takes place, as in the
convulfions above defcribed, but the jaws remain
firmly fixed together. This locked jaw is the mofl
frequent inftance of cataleptic fpafm, becaufe we are
more inclined to exert the mufcles fubfervient to
maftication from their early obedience to violent
efforts of volition.

But in the cafe related in Se&. XIX. on Reverie,
the cataleptic lady had pain in her upper teeth ; and
preffing one of her hands vehemently again ft her
cheek-bone to diminifh this pain, it remained in that
attitude for about half an hour twice a day, till the
painful paroxyfm was over.

I have this very day feen a young lady in this
difeafe, (with which me has frequently been affiift-
ed,) Ibe began to-day with violent pain mooting from

one

483 DISEASES OF VOLITION. SECT. XXXIV. r.

one fide of the forehead to the occiput, and after
various fkuggles lay on the bed with her fingers and
wrifts bent and fliif for about two hours ; in other
refpedts fhe feemed in a fyncope with a natural pulfe.
She then had intervals of pain and of fpafm, and
took three grains of opium every hour till fhe had
taken nine grains, before the pains and fpafm ceafed.

There is, however, another fpecies of fixed fpafm,
which differs from the former, as the pain exifts in
the contra&ed mufcle, and would feem rather to
be the confequence than the caufe of the contrac-
tion, as in the cramp in the calf of the leg, and in
many other parts of the body.

In thefe fpafms it fhould feetn, that the mufcle
itfelf is firft thrown into contraction by fome.difa-
greeable fenfation, as of cold ; and that then the
violent pain is produced by the great contraction
of the mufcular fibres extending its own tendons,
which are faid to be fenfible to extenfion only j and
is further explained in Sect. XVIII. 15.

6. Many inftances have been given in this work,
•where after violent motions excited by irritation,
the organ has become quiefcent to lefs, and even to
the great irritation, which induced it into violent
motion ; as after looking long at the fun or any
bright colour, they ceafe to be feen ; and after re-
moving from bright day-light into a gloomy room,
the eye cannot at firft perceive the objects, which
ftirnulate it lefs. Similar to this is the fyncope,
which fucceeds after the violent exertions of our,
voluntary motions, as after epileptic fits, for the
power of volition acts in this cafe as the ftimulus in
the other. , This fyncope is a temporary palfy, or
apoplexy, which ceafes after a time, the mufcles re-
covering their power of being excited into action
by the efforts of volition ; as the eye in the circum-
ftance above mentioned recovers in a little time its
power of feeing objects in a gloomy room, which

were

SF.CT. XXXIV. i. DISEASES OF VOLITION*

were invifible immediately after coming out of a
ftronger light. This is owing to an accumulation of
fenforial power during the inaction of thofe fibres,
which were before accuftomed to perpetual exerti-
ons, as explained in Seel. XII. 7. I. A ilighter de-
gree of this difeafe is experienced by every one
after great fatigue, when the mufcles gain fuch in-
ability to further adlion, that we are obliged to reft
them for a while, or to fummon a greater power
of volition to continue their motions.

In all the fyncopes, which I have feen induced
after convulfive fits, the pulfe has continued natu-
ral, though _the organs of fenfe, as well as the loco<-
motive mufcles, have ceafed to perform their func-
tions ; for it is necefifavy for the perception of ob-
jecls, that the external organs of fenfe fhould be
properly excited by the voluntary power, as the eye-
lids muft be open, and perhaps the mufcles of the
eye put into aclion to diftend, and thence give
greater pellucidity to the cornea, which in fyncoper
as in death, appears flat and lefs tranfparent. The
tympanum of the ear alfo feems to require a volun-
tary exertion of its mufcles, to gain its due tenfion,
and it is probable the other external organs of
fenfe require a (imilar voluntary exertion to adapt
them to the diftincl perception of objedls. Hence
in fyncope as in fleep, as the power of volition is
fufpended, no external objecls are perceived. See
Seel. XVIII. 5. During the time which the patient
lies in a fainting fit, the fpirit of animation becomes
accumulated ; and hence the mufcles in a while be-
come irritable by their ufual Simulation, and the
fainting fit ceafes. See Seel. XII. 7. i.

7. If the exertion of the voluntary motions has
been dill more energetic, the quiefcence, which fuc-
ceeds, is fo complete, that they cannot again be
excited into aclion by the efforts of the will. In
this manner the palfy, and apoplexy (which is an

univerfal

490 DISEASES OF VOLITION. SECT. XXXIV. i.

universal palfy) are frequently produced after con-
vulfions, or other violent exertions ; of this I (hall
add a few inftances.

Platernus mentions fome, who have died apoplec-
tic from violent exertions in dancing ; and Dr.
Mead, in his Effay on Poifons, records a patient in
ihe hydrophobia, who at one effort broke the cords
which bound him, and at the fame inftant expired,
And it is probable, that thofe, who have expired
from immoderate laughter, have died from this
paralyfis confequent to violent exertion. Mrs.
Scott of Stafford was walking in her garden in per-
fect health with her neighbour Mrs. ; the lat-
ter accidentally fell into a muddy rivulet, and tried
in vain to difengage herfelf by the affiltance of Mrs.
Scott's hand. Mrs. Scott exerted her utmoft power
for many minutes, firft to aflift her ffiend, and next
to pi event herfelf from being pulled into the mo-
rafs, as her diftreffed companion would not difen-
gage her hand. After other affiftance was procured
by their united fcreams, Mrs. Scott walked to a
chair about twenty yards from the brook, and was
feized with an apoplectic flroke: which continued
many days, and terminated in a total lofs of her
right arm, and her fpeech ;• neither of which me
ever after perfectly recovered.

It is faid, that many people in Holland have died
after fkating too long or too violently on their fro-
zen canals ; it is probable the death of thefe, and
of others, who have died fuddenly in fwimming, has
been owing to this great quiefcence or paralyfis j
which has fucceeded very violent exertions, added
to the concomitant cold, which has had greater
effect after the fufferers had been heated and ex-
haufted by previous exercife.

I remember a young man of the name of Nairne
at Cambridge, who walking on the edge of a barge
fell into the river. • His coufm and fellow-ftudent of

the

SECT. XXXIV. i: DISEASES OF ^VOLITION. 491

the fame name, knowing the other could not fwim,
plunged into the water after him, caught him by
his clothes, and approaching the bank by a vehe-
ment exertion propelled him fafe to the land, but
that iuftant, feized, as was fuppofed, by the cramp,
or paralyfis, funk to rife no more. The reafon why
the cramp of the mufcles, which compofe the calf
of the leg, is fo liable to afte£ fwimmers, is, be-
caufe thefe mufcles have very weak antagonifls, and
are in walking generally elongated again after their
contraction by the weight of the body on the ball
of the toe, which is very much greater than the re-
fiftance of the water in fwimming. See Section
XVIII. 15.

It does not follow that every apoplectic or para-
lytic attack is immediately preceded by vehement
exertion ; the quiefcence, which fucceeds exertion,
and which is not fo great as to be termed paralyfis,
frequently recurs afterwards at certain periods ; and
by other caufes of quiefcence, occurring with thofe
periods, as was explained in treating of the pa-
roxyfms of intermitting fevers ; the quiefcence at
length becomes fo great as to be incapable of again
being removed by the efforts of volition, and com-
plete paralyfis is formed. See Section XXXII. 3. 2.

Many of the paralytic patients, whom I have feen,
have evidently had difeafed livers from the too fre-
quent potation of fpirituous liquors ; fome of them
have had the gutta rofea on their faces and breads ;
which has in fome degree receded either fpontane-
oufly, or by the ufe of external remedies, and the
paralytic ftroke has fucceeded ; and as in feveral
perfons, who have drank much vinous fpirits, I have
obferved epileptic fits to commence at about forty
or fifty years of age, without any hereditary taint,
from the flimulus, as I believed, of a difeafed liver ;
I was induced to afcribe many paralytic cafes to the
famefource; which were not evidently the effect:

VOL. I. K k of

DISEASES OF VOLITION. SECT.XX^XIY. *

of age, or of unacquired debility. And the account
given before of d replies, which very frequently are
owing to a paralyfis of the abforbent fyftem, and
are generally attendant on free drinkers of fpiritu-
ous liquors, confirmed me in this opi-nion.

The difagreeable irritation of a difeafed liver pro-
duces exertions and confequent quiefcenee ; thefe by
the accidental concurrence of other caufes of qui-
efcence, as cold, folar or lunar periods, inanition,
the want of their ufual portion of fpirit of wine>
at length produces paralyfis.

This is further confirmed by obferving, that the
x mufcies, we moft frequently, or moll powerfully
exert, are mod liable to palfy ; as thofe oi the voice
and of articulation, and of thofe paralytics which
I have- feen, a much greater proportion have loft
the ufe of their right arm; which is fo much more
generally exerted than the left.

I cannot difmifs this fubje£fc without obfervingy
that after a paralytic ftroke, if the vital powers are
not much injured, the patient has all the move*
mems of the affecled limb to learn over again, jufl
as in early infancy ; the limb is firft moved by the
irritation of its mufcies, as in flretching, (of which
a cafe was related in Sedlion VII. i. 3.) or by the
eleftrie concuifion ; a1 terwards it becomes obedient
to fenfation, as in violent danger or fear ; and laftly,
the mufcies become again aflociated with volition,
and gradually acquire their ufual habits of adliiig
together.

Another phsenomenon in palfies is, that when the
limbs of one fide are difabled, thofe of the other
are in perpetual motion. This can only be explain-
ed from conceiving that the power of motion, what-
ever it is, or wherever it refides, and which is ca-
pable of being exhaufted by fatigue, and accumu-
lated in reft, is now lefs expended, whilfl one half
of the body is capable of receiving its due propor-

tion

SECT. XXXiV.2. DISEASES OF VOLITION. 493

tion of it, and is hence derived with greater cafe or
in greater abundance into the limbs, which remain
unaffected.

II. i. Theexcefsor defect of voluntary exertion
produces fimilar effects upon the fenfual motions, or
ideas of the mind, as thofe already mentioned up-
on the mufcular fibres. Thus when any violent
pain, ariiing from the defect of fome peculiar fli-
mulus, exiils either in the mufcular or fenfual fyf-
tems of fibres, and which cannot be removed by
acquiring the defective ftimulus } as in fome confti-
tutions convulfions of the mufcles are produced to
procure a temporary relief, fo in other conftitutions
vehement voluntary exertions of the ideas of the
mind are produced for the fame purpofe; for dur-
ing this exertion, like that of the mufcles, the pain
either vanifhes or is diminifhed : this violent exer-
tion conflitutes madnefs ; and in many cafes I have
ieen the madnefs take place, and the convulfions
ceafe, and reciprocally the madnefs ceafe, and the
convulfions fupervene. See Sect. III. 5. 8.

2. Madnefs is diftiuguifhable from delirium, as
in the latter the patient knows not the place where
he refides, nor the perfons of his friends or attend-
ants, nor is confcious of any external objects, ex-
cept when fpoken to with a louder voice, or Simu-
lated with unufual force, and even then he foon
relapfes into a ftate of inattention to every thing
about him. VVhilit in the former he is perfectly
ienlible to every thing external, but has the volun-
tary powers of his mind intenfely exerted n fome
particular object of his defire or averfion, he har-
bours in his thoughts a fufpicion of all mankind,
left they mould counteract his defigns ; and while
he keeps his intentions and the motives of his ac-
tions profoundly fecret ; he is perpetually (tudying
the means of acquiring the object of his wifh, or of
preventing or revenging the injuries hefufpedts.

Kk 2 3. A

DISEASES OF VOLITION. SECT. XXXIV. '».

3. A late French philofopher, Mr» Helvet'ms, has
deduced almoft all our adlions from this principle
of their relieving us from the ennui or taedium vitas ;
and true it is, that our defires or aver lions are the
motives of all our voluntary a&ions ; and human
nature feems to excel other animals in the more
facil ufe of this voluntary power, and on that ac-
count is more liable to infanity than other animals.
But in mania this violent exertion of volition is
expended on miftaken objects, and would not be re-
lieved, though we were to gain or efcape the ob-
jects, that excite it. Thus I have feen two instances
of madmen, who conceived that they had the itchy
and feveral have believed they had the venereal in-
fection, without in reality having a fymptom of
either of them. They have been perpetually think-
ing upon this fubject, and fome of them were in
vain falivated with defign of convincing them to
the contrary.

4. In the minds of mad people thofe volitions
alone exift, which are unmixed with fenfation; im-
moderate fufpieion is generally the firft fymptom,
and want of fhame, and want of delicacy about
cleanlinefs* Sufpicion is a voluntary exertion of
the mind, arifing from the pain of fear, which it is
exerted to relieve : Ihame is the name of a peculiar
difagreeable fenfation, fee Fable of the Bees, and deli-
cacy about cleanlraefs arifes from another difagree-
able fenfation. And therefore ate not found in the
minds of maniacs, which are employed folely in
voluntary exertions. Hence the moil modeft wo-
men in this difeafe walk naked arnongft men with-
out any kind of concern, ufe obfcene difcourfe, and
have no delicacy about their natural evacuations.

5. Nor are maniacal people more attentive to
their natural appetites, or to the irritations which
furround them, except as far as may refpecl their
fufpicions or defignsj for the violent and perpetual

exertions

SECT. XXXIV. 2. DISEASES OF VOLITION. 495

exertions of their voluntary powers of mind prevent
their perception of almoft every other object, either
of irritation or of fenfation. Hence it is that they
bear cold, hunger, and fatigue, with much greater
pertinacity than in their fober hours, and are left*
injured by them in refpect to their general health.
Thus it is afierted by hiftoiians, that Charles the
Twelfth of Sweden flept on the fnow, wrapped only
in his cloak, at the liege of Frederick ft ad, and bore
extremes of cold, and hunger, and fatigue, under
which numbers of his foldiers perimed; becaufe the
king was infane with ambition, but the foldier had
no fuch powerful ftimulus to preferve his fyftem
from debility and death.

6. Befides the infanities arifing from exertions in
ronfequence of pain, there is alfo a pleafurable in-
fanity, as well as a pleafurable delirium ; as the in*
fanity of perfonal vanity, and that of religious fana-
ticifm. When agreeable ideas excite into motion
the fenforial power of fenfation, and this again
caufes other trains of agreeable ideas, a conftant
ftream of pleafurable ideas fucceeds, and produces
pleafurable delirium. So when the fenforial power
of volition excites agreeable ideas, and the pleafure
thus produced excites more volition in its turn, a
conftant flow of agreeable voluntary ideas fucceeds ;
which when thus exerted in the extreme conftitutes
infanity.

Thus when our mufcular a&ions are excited by
our fenfations of pleafure, it is termed play; when
they are excited by our volition, it is termed work ;
and the former of thefe is attended with lefs fa-
tigue, becaufe the mufcular actions in play produce
in their turn more pleafurable fenfation ; which
again has the property of producing more mufcular
acuon. An agreeable inftance of this I faw this
morning. A little boy, who was tifed with walk-
ing, begged of his papa to carry him. " Here,"

fays

DISEASES OF VOLITION. Spcr. XXXIV. a.

fays the reverend doctor, " ride upon my gold-
headed cane ;" and the pleafed child, putting it
between his legs, galloped away with delight, and
complained no more of his fatigue. Here the aid
of another fenforial power, that of pleafurable fen-
fation, fuperadded vigour to the exertion of exhauft-
ed volition. Which could otherwife only have been
excited by additional pain, as by the laih of flavery.
On this account, where the whole fenforial power
has been exerted on the contemplation of the pro?
mifed joys of heaven, the faints of all perfecuted
religions have borne the tortures of martyrdom with
otheiwife unaccountable firmnefs.

7. There are fome difeafes, which obtain at leaft
a temporary relief from the exertions of infanity j
many inftances of diopfies being thus for a time
cured are recorded. An elderly woman labouring
•with afcites I twice faw relieved for fome weeks by
infanity, the dropfy ceafed fpr feveial weeks, an4
recurred again, alternating with the infanity. A man
afflicted with difficult refpiration on lying down,
with very irregular pulfe, and cedematous legs,
whom I faw this day, has for above a week been,
much relieved in refpect to all thofe fymptoms by
the accefiion of infanity, which is fhewn by inordi:
nate fufpicion, and great anger.

Jn cales of Common temporary anger the increaf-
ed action of the arterial fyftem is feen by the re4
Ikin, and increafed pulfe., with the immediate in*
creafe of mufcular activity. A friend of mine, when
he was painfully fatigued by riding on horfeback,
•was accuftomed to, call up ideas into his mind,
which ufed to excite his anger pr indignation, and
thus for a time at leaft relieved the 'pain of fatigue.
By this temporary infanity, the effecl of the volun-
tary power upon the whole of his fyftem was in-
creafed ; as in the cafes of dropfy above mentioned,
it would appear, that the increafed action of the

voluntary

SECT. XXXIV. 2. DISEASES OF VOLITION. 497

voluntary faculty of the feriforium affetfed the ab-
forbent fyitem, as well as the fecerning one.

8. In refpect to relieving inBammatory pains, and
removing fever, I have feen many mftances, as men-
tioned in Seel XII. 2. 4. One lady, whom I at-
tended, had twice at fome years interval a locked
jaw, which relieved a pain on her fternum with pe-
ripneumony. -Two other ladies I faw, who towards
the end of violent peripneumony, in which they
frequently loft blood, were at length cured by infa-
nity fupervening. In the former the increafed vo-
luntary exertion of the mufcles of the jaw, in the
latter that of the organs of fenfe, removed the dif-
eafe ; that is, the dilagreeable fenfation, which had
produced the inflammation, now excited the volun-
tary power, and thefe new voluntary exertions em-
ployed or expended the fuperabundant fenforial pow-
er, which had previoufly been exerted on the arte-
rial fyitem, and, caufed inflammation.

Another cafe, which I think worth relating, was
of a young man about twenty ; he had laboured
under an irritative fever with debility for three or
four weeks, with very quick and very feeble pulfe,
and other ufual fymptorns of that fpecies of typhus,
but at this time complained much and frequently
of pain of his legs and feet. When thole who at-
tended him were nearly in defpair of his recovery, I
obferved with pleafure an inlanity of mind fuper-
yene: which was totally different from delirium as
he knew his friends, calling them by their names,
and the room in which he lay, but became vio-
lently fufpicious of his attendants, and calumniated
with vehement oaths his tender mother, who fat
weeping by his bed. On this his pulfe became
flower and firmer, but the quicknefs did not for
fome time intirely ceafe, and he gradually recovered.
In this cafe the introduction of an increafed quan-
tity of the power of volition gave vigour to thofe

movements

498 DISEASES OF VOLITION. SECT. XXXIV. 3,

movements of the fyftem, which are generally only
a^uated by the power of irritation, and of affocia-
tion.

Another cafe I recollect of a young man, about
twenty-five, who had the fcarlet-fever, with very
quick pulfe, and an univerfal eruption on his (kin,
and was not without reafon efteemed to be in great
danger of his life. After a few days an infanity
fupervened, which his friends miftook for delirium,
and he gradually recovered, and the cuticle peele4
off. From thefe and a few other cafes I have always
efteemed infanity to be a favourable llgn in fevers,
and have cautioufly diftinguifhed it from delirium.

III. Another mode of merital exertion to relieve
pain, is by producing a train of ideas not only by
the efforts of volition, as in infanity ; but by thofe
of fenfation likewife, as in delirium and deep. This
mental effort is termed reverie, or fomnambulation,
and is defcribed more at large in Seel. XIX. on that
fubject. But I fhall here relate another cafe of that
wonderful difeafe, which fell yefterday under my
eye, and to which I have feen many analogous ali-
enations of mind, though not exadlly fimilar in all
circurriftances. But as all of them either began or;
terminated with pain or convulfion, there can be no
doubt but that they are of epileptic origin, and
conftitute another mode of mental exertion to re-
lieve fome painful fenfation.

i. Mafter A. about nine years old, had been
feized at feven every morning fpr ten days ttith un-
common fits, and had had flight returns in the after-
noon. They were fuppofed to originate from worms,
and had been in vain attempted to be removed by
vermifuge purges. As his fit was expected at feven
yefterday morning, I faw him before that hour ; he
was aileep, feemed free from pain, and his pulfe
natural. About feven he began to complain of pain
about his navel, or more to the left fide, and in a

few

SECT.XXX1V.3, DISEASES OF VOLITION. 499

few minutes had exertions of his arms and legs like
fwimming. He then for half an hour hunted a
pack of hounds ; as appeared by his hallooing, and
calling the dogs by their names, and difcourfing
with the attendants of the chafe, clefciibing exadly
a day of hunting, which (I was informed) he had
witnefled a year before, going through all the moft
minute circumftances of it ; calling to people, \vho
\vere then prelent, and lamenting the abfence of
others, who were then alfo abfent. After this fcene
he imitated, as he lay in bed, fome of the plays of
boys, as fwimming and jumping. He then fung
an Englifh and then an Italian fong ; part of which
with his eyes open, and part with the.m clofed, but
could not be .awakened or excited by any violence,
which it was proper to ufe.

After about an hour he came fuddenly to him-
felf with apparent furprife, and feemed quite igno-
rant of any part of what had paffed, and after bein^
apparently well for half an hour, he fuddenly fell
into a great ftupor, with flower pulfe than natural,
and a flow moaning refpiration, in which he conti-
nued about another half hour, and then recovered.

The fequel of this difeafe was favourable ; he was
direcled one grain of opium at fix every morning,
and then to rife out of bed ; at half paft fix he was
directed fifteen drops of laudanum in a glafs of wine
and water. The fit ft day the paroxyfm became
fhorter, and lefs violent. The dofe of opium was
increafed to one-half more, and in three or four
days the fits left him. The bark and filings of iron
were alfo exhibited twice a day ; and I believe the
complaint returned no more

2. In this paroxyfm it muft be obfcrved, that he
began with pain, and ended with ftupor, in both
circumftances refcmbling a fit of epilepfy. And
that therefore the exertions both of mind and body,
both the voluntary ones, and thofe immediately ex-
cited

5oo DISEASES OF VOLITION. SECT. XXXIV. j.

cited by pleafurable fenfation, were exertions to re-
lieve pain.

Tbe hunting fcene appeared to be rather an aft
of memory than of imagination, and was therefore
rather a voluntary exertion, though attended with
the pleafarable eagernefs, which was the confe-
quence of thofe ideas recalled by recollection, and
not the caufe of them.

Thefe ideas thus voluntarily recolle&ed were fuc-
ceeded by fenfations of pleafure, though his fenfes
\vere unaffected by the ftimuli of vifible or audible
obje&s ; or fo weakly excited by them as not to
produce fenfation or attention. And the pleafure
thus excited by volition produced other ideas and
other motions in confequence of the tentbrial power
of fenfation. Whence the mixed catenations of vo^
luntary and fenfitive ideas and mufcular motions in
reverie ; which, like every other kind of vehement
exertion, contribute to relieve pain, by expending a
{arge quantity of fenforial power.

Thofe fits geneialiy commence during fieep, from,
whence I fuppofe they have been thought to have,
fome connection with ileep, and have thence been
termed Somnambulifm ; but their commencement
during ileep is owing to our increafed excitability
by internal fenfations at that time, as explained in
Sect XVIII. 14 and 15, and nof to any fimilitude
between reverie and deep.

3. I was once concerned for a very elegant and
ingenious young lady, who had a reverie on alter-
nate days, which continued nearly the whole day ;
and as in her days of difeafe (lie took up the fame
kind of ideas, which (he had convened about on the
alternate day before, and could recollecl nothing of
them on her well-day ; fhe appeared to her friend $
to poffefs two minds. This cafe alfo was of epi-
leptic kind, and was cured, with fome relapfes, by

ppium.

3. DISEASES OF VOLITION. 501

opium adminiftered before the commencement of
the paroxyfm.

4. Whence it appears, that the methods of re*
lieving inflammatory pains, is by removing all fli-
mulus, as by venefe&ion, cool air, mucilaginous
diet, aqueous potation, filence, darknefs.

The methods of relieving pains from defect of fli-
mulus is by fupplying the peculiar Himulus required,
as of food, or warmth.

And the general method of relieving pain is by
exciting into adtion fome great part of the fyftem,
for the purpofe of expending a part of the fenfona!
power. This is done either by the exertion of the
voluntary ideas and mufcles, as in infanity and con-
vulfion y or by exerting both voluntary and fenfitive
motions, as in reverie; or by exciting the irritative
motions by wine or opium internally, and by the
warm bath or blifters externally ; pr laftly, by exr
citing the fenlitive ideas by good news^ affe&ing
, or agreeable paflions.

SECT.

DISEASES OF ASSOCIATION. SECT, XXXV. i,

SECT. XXXV*

DISEASES OF ASSOCIATION

i . Sympathy or confent of parts. Primary and ft*
condary parts of an aflbciated train of motions reci-
procally affeft each other. Parts of irritative trains
of motion ajfeft each other in four ways. Sympa-
thies of the Jkin and jlomach. Flujhing of the face
after a meal. Eruption of the fmall-pox on the face.
Chillnefs after a meaL 2. Per tigo from intoxication.
3. Absorption from the lungs aqd pericardium by
emetics. In vomiting the a&ions of the jlomach are
decreafed, not increafsd. Digejlionjlrengthened after
an emetic. Vomiting from clejiciency of fenforial
power. 4. 'Dyfpnceafrom cold bathing. Slow pulfe
from digitalis. Death from gout in the flomack.
1 1. i. Primary and fzcondary parts of fenfitwe affo-
ciations affect each other. Pain from gall-Jlone,froi%
urinary Jlone. Ifemicrania. Painful epilepfy. 2.
Gout and red face from injlamed liver. Shingles
from inflamed kidney. ^. Cory za from cold applied
to the feet. Pleurify, ^Hepatitis. 4. Pain of fhoul-
ders from injlamed liu$r. III. Difeafes from the
ajjbciations of

I. i. MANY fynchronous and fucceffive motions
of our mufcular fibres, and of our organs of fenfe,
or ideas, become affociated fo as to form indiflblu-
ble tribes or trains of action, as fhewn in Se6tion
X. on Aflbciate Motions. Some conftitutions more
cafily edablifh thefe afibciadons, whether by volun-
tary, fenfitive, or irritative repetitions, and fome

more

SECT. XXXV. i. DISEASES OF ASSOCIATION. 503

more eafily lofe them again, as fhewn in Se&ion .
XXXI. on Temperaments.

When the beginning of fuch a train of actions be-
comes by any means difordered, the fucceeding pare
is liable to become disturbed in confequence, and
this is commonly termed fympathy or confent of
parts by the writers of medicine. For the more
clear undemanding of thefe fympathies we mult
confider a tribe or train of a&ions as divided into
two parts, and call one of them the primary or
original motions, and the other the fecondary or
fym pathetic ones.

The primary and fecondary parts of a train of
irritative a&ions may reciprocally affe& each other
in four different manners, i. They may both be
exerted with greater energy than natural* 2. The
former may aft with greater, and the latter with
lefs energy. 3. The former may aft with lefs, and
the latter with greater energy. 4. They may both
act with lefs energy than natural. I fhall now give
an example of each kind of thefe modes of adhon,
and endeavour to mew, that though the primary
and fecondary parts of thefe trains or tribes of mo-
tion are conne&ed by irritative affociation, or their
previous habits of acting together, as defcribed in
Sect. XX. on Vertigo. Yet that their a&ing wLh
fimilar or diffimilar degrees of energy, depends on
the greater or lefs quantity of fenforial power, which
the primary part of the train expends in its exer-
tions.

The actions of the ftomach conftitute fo important
a part of the affbciaiions of both irritative and fen-
fitive motions, that it is faid to fympathize with
alrnoft every part of the body; the firft example,
which I ffiall adduce to fhew that both the primary
and fecondary parts of a train of irritative affocia-
tions of motion ael with increaled energy, is taken
from the confent of the fkin with this organ. When

the

$»4 DISEASES OF ASSOCIATION. SECT. XX&V. t.

the adlion of the -fibres of die ftomach is increafed,
as by the fHmulus of a full meal, the exertions of
the cutaneous arteries of the face become in creafed
by their irritative afibciafions with thofe of the fto-
mach, and a glow or flaming of the face fucceeds.
For the fmall veflels of the fkin of the face having
been more accultomed to the varieties* of action,
from their frequent expofure to various degrees of
cold and heat become more eafily excited into in-
creafed a&ion, than thofe of the covered parts of
our bodies* aad thus aft with more energy from
their irritative or fentltive altbciations with the fto-
mach. On this account in fmall-pox the eruption
in confequence of the previous affection of the Ito-
mach breaks out a day fooner on the face than on
the hands, and two days fooner than on the trunk,
and recedes in fimilar times after maturation.

But fecondly, in weaker confutations, that is, in
thofe who poffefs lefs fenforial power, fo much of
it is expended in the increafed a6lions of the fibres
of the ilomach excited by the ftimulus of a meal,
that a fenfe of chilnefs fucceeds inflead of the uni-
verfal glow above mentioned ; and thus the fecon-
dary part of the affociated train of motions is dimi-
nilhed in energy, in confequence of the increafed
activity of the primary part of it.

2, Another inftance of a fimilar kind, where the
fecondary part of the train ads with lefs energy in
confequence of the greater exertions of the primary
part, is the vertigo attending intoxication ; in this
circumflance fo much fenforial power is expended
on the Romach, and on its neareft or more ihongly
affociated motions, as thofe of the fubcutaneous vef-
fels, and probably of ths membranes of fome inter-
nal vifcera, that the irritative motions of the retina
become imperfectly exerted from deficiency of fen-
forial power, as explained in Seel. XX. and XXI. 3.
pn Vertigo and on Drunkennefs, and hence the dag-
gering

SECT. xxxv. i. DISEASES OF ASSOCIATION. 505

gering inebriate cannot completely balance himfelf
by fuch indiftinft vifion.

3. An inftance of the third circumftance, where
the primary part of a train of irritative motions ads
with lefs, and the fecondary part with greater ener-
gy, may be obferved by making the following ex-
periment. If a perfon lies with his arms and fhoul-
ders out of bed, till they become cold, a temporary
coryza or catarrh is produced ; fo that the paflage
of the noftrils becomes totally obftruded ; at lead
this happens to many people ; and then on covering
the arms and fhoulders, till they become warm,
the paflage of the noftrils ceafes again to be ob-
ftru&ed, and a quantity of mucus is difcharged from
them. In this cafe the quiefcence of the veflels of
the (kin of the arms and moulders, occafioned by
expofute to cold air, produces by irritative aflbci-
ation an increafed action of the veflels of the mem-
brane of the noftrils ; and the accumulation of fen-
foriai power during the torpor of the arms and
(houlders is thus expended in producing a temporary
coryza or catarrh.

Another inftance may be adduced from the fym-
pathy or confent of the motions of the ftomach
with other more diftant links of the very extenlive
tribes or trains of irritative motions affociated with
them, defcribcd in Seel. XX. on Vertigo. When
the actions of the fibres of the ftomach are dimi-
nifhed or inverted, the adions of the abforbent
veflels, which take up the mucus from the lungs,
pericardium, and other cells of the body, become
increafed, and abfoib the fluids accumulated in them
with greater avidity, as appears from the exhibition
of foxglove, antimony, or other emetics in cafes of
anafarca, attended with unequal pulfe and difficult
ref pi ration.

That the act of naufea and vomiting is a decreaf-
ed exertipn of the fibres of the ftomach may be thus

deduced ;

So6 DISEASES OF ASSOCIATION. SECT. XXXV. i;

deduced j when an emetic medicine is adminiflered,
it produces the pain of ficknefs, as a difagreeable
tafte in the mouth produces the pain of naufea ;
thefe patns, like thofe of hunger, or of cold, or
like thofe, which are ufually termed nervous, as the
headrach or hemicrama, do not excite the organ in-
to greater aclion ; but in this cafe I imagine the
pains of ficknefs or of naufea counteracl or deflroy
the pleafurable fenfation. which feems neceffary to
digeition, as fhewn in Sett. XXXIII. i. f. The pe-
riftaltic motions of the fibres of the ftomach be-
come enfeebled by the \vant of this ilimulus of
pleafurable fenfation, and in confequence flop for a
time, and then become inverted ; for they cannot
become inverted without being previoufly flopped.
Now that this inverfion of the trains of motion of
the fibres of the ftomach is owing to the deficiency .
of pleafurable fenfation is evinced from this circum-
fiance, that a naufeous idea excited by words wilt
produce vomiting as effectually as a naufeotis drug.

Hence it appears, that the act of naufea or vo*
miting expends lefs fenforial power than the ufual
periflaltic motions of the ftomach in the digeftion
of our aliment ; and that hence there is a greater
quantity of fenforial power becomes accumulated
in the fibres of the flomach, and more of it in
confequence to fpare for the action of thofe parts
of the fyftem, which are thus affociated with the
ilomach, as of the whole abforbent feries of veflels,
and which are at the fame time excited by their
ufual flimuli.

From this we can underftand, how after the ope-
ration of an emetic the flomach becomes more irri-
table and fenfible to the ftimulus, and the pleafure
of food ; fince as the fenforial power becomes ac-
cumulated during the naufea and vomiting, the
digeftive power is afterwards exerted more forcibly
for a time. It mould, however, be here remarked,

that

SECT. XXXV. a. DISEASES OF ASSOCIATION. 507

that though vomiting is in general produced by the
defect of this ftimulus of pleafurable fenfation, as
When a naufeous drug is adminiftered ; yet in long
continued vomiting, as in fea-ficknefs, or from habi-
tual dram-drinking, it arifes from deficiency of fen-
foii.il power, "which in the former cafe is exhaufted
by the increafed exertion of the irritative ideas of
vifion, and in the latter by the frequent application
of an unnatural ftimulus.

4. An example of the fourth circumftance above
mentioned, where both the primary arid fecondary
parts of a train of motions proceed with energy lefs
than natural, may be obferved in the dyfpncea, which
occurs in going into a very cold bath, and which
has been defcribed and explained in Seel. XXXII. 3. 2*

And by the increafed debility of the pulfations of
the heart and arteries during the operation of an
emetic. Secondly, from the flownefs and intermif-
fion of the pulfations of the heart from the inceffant
efforts to vomit occafioned by an overdofe of digi-
talis. And thirdly, from the total floppage of the
motions of the heart, or death, in confequence of
the torpor of the ftomaeh, when affected with the
commencement or cold paroxyfm of the gout. See
Sea. XXV. 17.

II. i. The primary and fecondary parts of the
trains of fenfitive affociadon reciprocally affect each
other in different manners, i. The increafed fen-
fation of the primary part may eeafe, when that of
the fecondary part commences. 2. The increafed
action of the primary part may ceafe, when that of
the feeondary part commences. 3. The primary
part may have increafed fenfation, and the fecon-
dary part increafed action. 4. The primary part
may have increafed action, and the fecondary part
increafed fenfation.

Examples of the firft mode, where the increafed
fenfation of the primary part of a.irain of fenfitive
afTociation ceafes, when that of the fecondary part
I. LI commences?

DISEASES OF ASSOCIATION. SECT. XXXV. 2.

commences, are not unfrequent ; as this is the ge-
neral origin of thofe pains, which continue fome
time without being attended with inflammation, fuch
as the pain at the pic of the ftomach from a ftone
at the neck of the gall-bladder, and the pain of
ftrangury in the glans penis from a ftone at the neck
of the urinary bladder. In both thefe cafes the
part, which is alfecled fecondarily, is believed to
be much more fenfible than the part primarily af-
fected, as defcribed in the catalogue of difeafes,
ClafsJI. i. i. H. and IV. 2. 2.2. and IV. 2. 2. 4.

The hemicrania, or nervous heau-ach, as it is
called, when it originates from a decaying tooth,
is another difeafe of this kind ; as the pain of the
carious tooth always ceafes, when the pain over one
• eye and temple commences. And it is probable,
that the violent pains, which induce convulfions in
painful epilepfies, are produced in the fame man-
ner, from a more fenfible part fympathizing with a
difeafed one of lefs fenfibility. See Catalogue of
Difeafes, Clafs IV. 2. 2. 8. and III. i. i. 6.

The laft tooth, or dens fapientise, of the upper
jaw moft frequently decays firft, and is liable to
produce pain over the eye and temple of that fide.
The laft tooth of the under jaw is alfo liable to
produce a fimilar hemicrania, when it begins to de-
cay. When a tooth in the upper jaw is the caufe
of the beadach, a (lighter pain is fometimes per-
ceived on the cheek-bone. And when a tooth in
the lower-jaw is the caufe of headach, a pain fome-
times affects the tendons of the mufcles of the neck,
which are attached near the jaws. But the clavus
hyilericus, or pain about the middle of the parietal
bone on one fide of the head, I have feen produced
by the fecond of the molares, or grinders, of the
under jaw; of which I (hall relate the following
cafe. See Clafs iV. 2. 2. 8.

Mrs.

ECT. XXXV. 2. DISEASES OF ASSOCIATION.

Mrs. •, about 30 years of age, was feized

with great pain about the middle of the right pa-
rietal bone, which had continued a whole day be-
fore I faw her, and was fo violent as to threaten,
to occafion convulfions. Not being able to detect
a decaying tooth, or a tender one, by examination
with my eye, or by ftriking them with a tea-fpoon,
and fearing bad confequences from her tendency to
convulfion, I advifed her to extract the laft tooth of
the under-jaw on the affected iide ; which was done
without any good effect. She was then directed to
lofe blood, and to take a brifk cathartic ; and after
that had operated, about 60 drops of laudanum
were given her, with large dofes of bark ; by which
the pain was removed. In about a fortnight flie
took a cathartic medicine by ill advice, and the
pain returned with greater violence in the fame place,
and, before I could arrive, as (he lived 30 miles from,
me, (he fuffered a paralytic firoke; which affected
her limbs and her face on one iide, and relieved
the pain of her head.

About a year afterwards I was again called to
her on account of a pain as violent as before, ex-
actly on the fame part of the other parietal bone.
On examining her mouth I found the fecond molaris
of the under-jaw on the fide before affected was
now decayed, and concluded, that this tooth had
occafioned the ftroke of the palfy by the pain and
confequent exertion it had caufed. On this account
I earneftly entreated her to allow the found molaris
of the fame jaw oppofite to the decayed one to be
extracted ; which was forthwith done, and the pain
of her head immediately ceafed, to the aiionilhment
of her attendants.

In the cafes above related of the pain exifting in
a part diflant from the feat of the difeafe, the pain
is owing to defeft of the ufual motions of the pain-
ful part. This appears from the coldnefs, palenefs,

LI 3 and

$IQ DISEASES OF ASSOCIATION. SECT, XXXV. 2.

and emptinefs of the affe&ed veffels, or of the ex-
tremities of the body in general, and from there
being no tendency to jcn flam mar ion-. The increafed
action of the primary part of thefe aiTociated mo-
tions, as of the hepatic termination of the bik-du&
from the ftimulus of a gall-ftone, or of the interior
termination of die urethra from the ftimulos of a
flone in the bladder, or laftlv, of a decaying tooth
in hemicrania, deprives the fecondary part of thefe
affociated motions, namely, the exterior terminati-
ons of the bile-duel or urethra, or the pained mern-
fcranes of the head in hemicrania, of their narural
fhare of fenforial power : and hence the fecondary
parts of thefe fenfttive trains of aiTociation become
pained from the deficiency of their ufaal motions,
which is accompanied with deficiency of fecretions
and of heat. See Sett. IV. 5. XII 5. 3. XXXIV. u

Why does the pain of the primary part of the
affociation ceafe, when that of the fecondary part
commences ? This is a queftion of intricacy, but'
perhaps not inexplicable. The pain of the primary
part of thefe affociated trains of motion was owing
to too great fUmutus, as of the flone at the neck of
the bladder, and was consequently caufed by too-
great a&ion of the pained part. This greater ac-
tion than natural of the primary part of thefe affo-
eiated motions, by employing or expending the fen-
forial power of irritation belonging to the whole
affociated train of motions, occafioned torpor, and
confequent pain in the fecondary part of the affoci-
ated train ; which was poffeffed of greater feniibility
than the primary part of it. Now the great pain
of the fecondary part of the train, as foon as it
commences, employs or expends the fenforial pow-
er of fenfation belonging to the whole affociated
train of motions ; and in confequence the motions
of the primary part, though increafed by the ftimu-
lus

Stc-r.XXXV. 2. DISEASES OF ASSOCIATION. 511

lus of an extianeousbody, ceafe to be accompanied
with pain or fecfation.

If this mode of reafoning bejuft, it explains a
curious fact, why when two parts of the body are
ftrongly ftimulated, the pain is felt only in one of
them, though it is polEble by voluntary attention
it may be alternately perceived in them both. In
the fame manner, when two new ideas are prefent-
ed to us from the IHmulus of external bodies, we
attend to but one of them at a time. In other
words, when one fet of fibres, whether of the muf-
cles or organs of fenfe, contract fo ftrongly as to
excite much fenfation ; another fet of fibres con-
tracting more weakly do not excite fenfaiion at all,
becaufe the fenforial power of fenfation is pre-occu-
pied by the firft fet of fibres. So we cannot will
more than one effect at once, though by aflbciations
previoufly formed we can inove many fibres in corn-
bin a tiofi.

Thus in the inftances above related, the termina-
tion of the bile duel: in the duodenum, and the ex-
terior extremity of the urethra, are more fenfible
than their other terminations. When thefe parts
are deprived of their ufual motions by deficiency of
fenforial power, as above explained, they become
painful according to law the fiah in Section IV. and
the lefs pain, originally excited by the ftimulus of
concreted bile, or of a ftone at their other extre-
mities, ceafes to be perceived. Afterwards, howe-
ver, when the concretions of bile, or the ftone on
the urinary bladder, become more numerous or
larger, the pain from their increafed flimulus be-
comes gieater than the aflbciated pain ; and is then
felt at the neck of the gall bladder or urinary blad-
der ; and the pain of the glans penis, or at the pit
of the nomach ceafes to be perceived.

2. Examples of the fecond mode, where the in-
creafed action of the primary part of a train of

fenfnive

$ra DISEASES OF ASSOCIATION. SECT. XXXV. 2.

fenfitive aflbciation ceafes, when that of the fecon-
dary part commences, are alfo n.ot unfrequent ; as
this is the ufual manner of the tranflation of in*
flammations from internal to external parts of the
fyftem, fuch as when an inflammation of the liver
or ftomach is tranflated to the membranes of the
foot, and forms the gout ; or to the (kin of the
face, and forms the rofy drop ; or when an inflam-
mation of the membranes of the kidneys is tranf-
lated to the ikin of the loins, and forms one kind
of herpes, called (hingles ; in thefe cafes, by whate-
ver caufe the original inflammation may have been
produced, as the fecondary part of the train of fen.
iitive aflbciation is more fenfible, it becomes ex-
erted with greater violence than the firft part of it j
and by both its increafed pain, and the increafed
motion of its fibres, fo far diminifhes or exhaufts
the fenforial power of fenfation, that the primary
part of the train being lefs fenfible ceafes both to
feel pain, and to aft with unnatural energy.

3. Examples of the third mode, where the pri-
mary part of a train of fenfitive aflbciation of mo*
lions may experience increafed fenfaiion, and the
fecondary parr increafed action, are likewife not un-
frequent ; as it is in this manner that moil inflam-
mations commence. Thus, after ftanding fome time
in fnow, the feet become affected with the pain of
cold, and a common coryza, or inflammation of the
membrane of the noftrik, fucceeds. It is probable
that the internal inflammations, as pleurifies, or he-
patitis, which are produced after the cold paroxyfm
of fever, originate in the fame manner from the
Sympathy of .thof$ parts with fome others, which
were previoufly pained from quiefcence ; as hap-
pens to various parts of the fyftem during the cold
fits of fevers. In thefe cafes it would feem, that
the fenforial power of fenfation becomes accumu-
lated during the pain of cold, as the torpor of the

veffeli

SKCT. XXXV. 3. DISEASES OF ASSOCIATION. -513

veflels occafioned by the defect of heat contributes
to theincreafe or accumulation of the fenforial pow-
er, of irritation, and that both thefe become exerted
on fome internal part, which was not rendered tor-
pid by the cold which affected the external parts,
nor by its aflbciation with them ; or which fooner
recovered its fenfibility. This requires further con-
fideration.

4. An example of the fourth mode, or where the
primary part of a feniitive affociation of motions
may have increafed action, and the fecondary part
increafed fenfation, may be taken from the pain of
the fhoulder, which attends inflammation of the
membranes of the liver, fee Clafs IV. 2. 2. 9. ; in
this circumftance fo much fenforial power feems to
be expended in the violent actions and fenfations of
the inflamed membranes of the liver, that the mem-
branes affociatcd with them become quiefcent to their
ufual ftirnuli, and painful in coufequence.

There may be other modes in which the primary
and fecondary parts of the train of aflbciated fenii-
tive motions may reciprocally affect each other, as
may be feen by looking over Clafs IV. in the cata-
logue of difeafes ; all which may probably be re-
folved into the plus and minus of fenforial power,
but we have not yet had fufficient obfervations made
upon them with a view to this doctrine.

III. The aflbciated trains of our ideas may have
fympathies, and their primary and fecondary parts
affect each other in fome manner fimilar .to thofe
above defcribed ; and may thus occafion various cu-
rious phenomena not yet adverted to, befides thofe
explained in the Sections on Dreams, Reveries, Ver-
tigo, and Drunkennefs ; and may thus difturb the
deductions of our reafonings, as well as the dreams
of our imaginations ; prefent us with falfe degrees
of fear, attach unfounded value to trivial circum-
itances ; give occafion to our eaily prejudices and

antipathies ;

$14 PERIODS OF DISEASES. SECT. XXXVI. ,.

antipathies; and thus embarrafs the happinefs of our
lives. A copious and curious harveft might be reap,
ed from this province of fcience, in which, howe-
ver, I ihall not at prefent wield my fickle.

SECT. XXXVI.

OF THK PERIODS OF DISEASES.

J. Mufcles excited by volition foon ceafe to contraB, ot
by fenfation, or by irritation, owing to the exhauf*
tjon of fenforial power. Mufcles fubjefled to /eft

Jtimulus have tJieir fen fur ia/ power accumulated^
Hence the periods of fame fevers. Want of irrita-
bility after intoxication. II. i. Natural afiions cate-
nated with daily habits of Life, z . With folar periods.
Periods of Jleep. Of evacuating the bowels. 3. Na-
tural aftions. catenated* with lunar periods. Men-

Jlr nation. Venereal or gafm of animals. Barrennefs.

III. Periods of difeafed animal aclions from flated
returns of no&urnal col-d, from folar and lunar in-
fluence. Periods of diurnal fever, heQic fever , quo-
tidian , tertian, quartan f ever. Periods of gout ,
fleurify, of fevers with arterial, debility, and with
Arterial ftrength- Periods of rhaphania, of nervous
cough, hemicrania, arteria( hemorrhages, hemorr-
hoids, hcemoptoe, epilepfy, palfy, apoplexy, madnefs.

IV. Critical days depend on limar periods. Lunar
periods in the fmall po%.

I. IF any of our mufcles be made to contract
viqlently by the power pf volition, as ihofe of th$

fingers,

SECT. XXXVI. i. PERIODS OF DISEASES. 515

lingers, when any one hangs by his hands on a
iwing, fatigue foon enfu.es ; and the mufcl.es ccafe
to act, owing to the temporary exhauftion of the
fphit of animation ; as foon as this is again accu-
mulated in the mufcles, they are ready to contract
again by the efforts of volition.

Thofe violent mufcular actions induced by pain
become in the fame manner intermitted and recur-
rent ; as in labour-pains, vomiting, tenefmus, ftran-
gury ; owing likcwife to the temporary exhauftion
of the fpirit of animation, as above mentioned.

When any ftimulus continues long to act writh
unnatural violence, fo as to produce too energetic
action of any of our moving organs, thofe motions
foon ceafe, though the flimulus continues to act;
as in looking long on a bright object, as on an
jnch-fquare of red filk laid on white paper in the
jfunfhine. See Plate I. in Sect. IIL i. '

On the contrary, \vhere lefs of the flimulus of
volition, fenfation, or imitation, have been ap-
plied to a mufcle than ufual ; there appears to be
an accumulation of the fpirit of animation in the
jnoving organ ; by which it is liable to a£t with
greater energy from lefs quantity of flimulus, than
was previoufly neceflary to excite it into fo great
action ; as after having been imrnerfed in fnow the
cutaneous veffels of our hands are excited imp
ilronger action by the flimulus of a lefs degree of
heat, than would previously have produced that
effea.

From hence the periods of fome fever-fits may
take their origin, either fimply, or by their acci-
dental coincidence with lunar and folar r.^riofls, or
with the diurnal periods of heat and cold, to be
treated of below ; for during the cold fit at the
commencement of a fever, from whatever caufe that
cold fit may be induced, it follows, i. That the
fpirit of animation muft become accumulated in

the

PERIODS OF DISEASES. SECT. XXXVl-a,

the parts, which exert during this cold fit lefs than
their natural quantity of adion. 2. If the caufe
producing the cold fit does not increafe, or becomes
Siminifhed ; the parts before benumbed or inadive
become now excitable by fmaller ftimulus, and are
thence thrown into more violent a6Uon than is na-
tural; that is, a hot fitfucceeds the cold one. 3.
By the energetic a6tion of the fyftem during the
hot fit, if it continues long, an exhauftion of the
fprit of animation takes place, and another cold fit
is liable to fucceed, from the moving fyftem not
being excitable into a&ion from its uiual ftimulus.
This inirritability of the fyftem from a too great
previous ftimulus, and confequent exhauftion of
fenforial power, is the caufe of , the general debi-
lity, and ficknefs, and head ach, fonie hours after
intoxication. And hence we fee one of the caufes
of the periods of fever-fits ; which however are fre-
quently combined with the periods of our diurnal
habits^ or of heat and cold, or of folar or lunar pe-
riods.

When befides the tendency to quiefcence occa-
iioned by the expenditure of ienforial power during
the hot fit of fever, fome other caufe of torpor, as
the folar or lunar periods, is neceffary to the in-
troduction of a fecond cold fit ; the fever becomes
of the intermittent kind ; that is, there is atfpace of
time intervenes between the end of the hot fit, and
the commencement of the next cold one. But where
BO exteriour caufe is neceflfary to the introduction
of the fecond cold fit ; no fuch interval of health
intervenes ; but the fecond cold fit commences, as
foon as the fenforial power is fufficiently exhaufted
by the hot fit ; and the fever becomes continual.

II. i. The following are natural animal a&ions,
•which are frequently catenated with our daily habits
of life, as well as excited by their natural irritati-
ons» The periods of hunger and thirft become

catenated

SECT. XXXVI. a. PERIODS OF DISEASES. 517

catenated \vith certain portions of time, or degrees
of exhauftion, or other diurnal habits of life. And
if the pain of hunger be not relieved by taking
food at the ufual time, it is liable to ceafe till the
next period of time or other habits recur , this is
not only true in refpec~l to our general deiire of
food, but the kinds of it alfo are governed by this
periodical habit ; infomuch that beer taken to break-
fail will diilurb the digeftion of thofe, who have
been accuftomed to tea ; and tea taken at dinner
will difagree with thofe, who have been accuftomed
to beer. Whence it happens, that thofe, who have
weak ftomachs, will be able to digeft more food, if
they take their meals at regular hours; becaufe they
have both the ftimulus of the aliment they take, and
the periodical habit, to aflat their digeftion.

The periods of emptying the bladder are not only
dependent on the acrimony or diflention of the
water in it, but are frequently catenated with ex-
ternal cold applied to the ikin, as in cold bathing,
or wafhing the hands ; or with other habits of life,
as many are accuftomed to empty the bladder be-
fore going to bed, or into the houfe after a journey,
and this whether it be full or not.

Our times of refpiration are not only governed
by the ftimulus of the blood in the lungs, or our
defire of frefh air, but alfo by our attention to the
hourly objecls before us. Hence when a perfon is
earneiily contemplating an idea of grief, he forgets
to breathe, till the fenfation in his lungs becomes
very urgent ; and then a figh fuccecds for the pur-
pofe of more forcibly pufhing forwards the blood,
which is accumulated in the lungs.

Our times of refpiration are alfo frequently go-
verned in part by our want of a fteady fupport for
the a6lions of our arms, and hands, as in threading
a needle, or hewing wood, or in fwimming; when
we are intent upon thefe objefts, we breathe at

the

PERIODS OF DISEASES. SECT. XXXVI. a.

«he intervals of the exertion of the petforal muf-
,cles.

2. The following natural animal a&ions are influ-
enced by folar periods. The periods of fleep and
of waking depend much on the folar period, for we
are inclined to fleep at a certain hour, and to awake
at a certain hour, whether we have had more or
lefs fatigue during the day, if within certain limits ;
and are liable to wake at a certain hour, whether
we went to bed earlier or later, within certain li-
mits. Hence it appears, that thofe who complain
of want of fleep, will be liable to fleep better or
longer, if they accuftom themfeives to go to reft,
and to rife, at certain hours.

The periods of evacuating the bowels are gene-
rally connected with feme part of the folar day, as
well as with the acrimony or diftenlion occafioned
by the feces. Hence one method of corre&ing cof-
tivenefs is by endeavouring to eftablifli a habit of
evacuation at a certain hour of ,the day, as recom-
mended by Mr. Locke, which may be accomplifhed
by ufing daily voluntary efforts at thofe times, join-
ed with the ufual flimulus of the material to be eva-
cuated.

3. The following natural animal actions are con-
netted with lunar periods, i. The periods of fe-
male menftruation are connected with lunar periods
to great exaclnefs, in fome inftances even to a few
hours. Thefe do not commence or terminate at
the full or change, or at any other particular part of
the lunation, but after they have commenced at any
part of it, they continue to recur at that part with
great regularity, unlefs difturbed by fome violent
circumftance, as explained in Se&. XXXII. No. 6.^
their return is immediately caufed by deficient ve-
nous abforption, which is owing to the want of the
flimulus, ciefigned by nature, of amatorial copula-
tion, or of the growing fetus. When the catamenia

returns

SacT. XXXVI. 3. PERIODS OF DISEASES. 5*9

returns fooner than the period of lunation, it fhews
a tendency of the conftitution to inirritability ; that
is, to debility, or deficiency of fenforial power, and
is to be relieved by fmali dofes of fleet and opium.

The venereal oigafm of birds and quadrupeds
feems to commence, or return about the moft pow-
erful luna-tions at the vernal OF autumnal equinoxes;
but if it be difappointed of its object, it is faid to
recur at monthly periods; in this refpect refembling
the female catamenia. Whence it is believed, that
women are more liable to become pregnant at or
about the time of their catamenia, than at the in-
termediate times ; and on this account they are fel-
dom much mrftaken in their reckoning of nine lunar
periods from the laft menftruation ; the inattention
to this may fometimes have been the caufe of fup-
pofed barrennefs, and is therefore worth the Obfer-
vauon of thofe, who wifli to have children.

III. We now come to. the periods of difeafed ani-
mal actions. The periods of fever-fits, which de-
pend on the dated returns of no&urnal cold, are
difcufled in Sect. XXXII. 3. Thole, which originate
or recur at folar or lunar peiiods, are alfo explain-
ed in Section XXXII. 6. Thefe we (hall here enu-
merate ; obferving, however, that it is not more fur-
prifing, that the influence of the varying attradlions
of the fun and moon, mould raife the ocean into
mountains, than that -it fhould affect the nice fenfi-
bilities of animal bodies ; though the manner of its
operation on them is difficult to be underftood. It
is probable however, that as this influence gradually
leflens during the courfe of the day, or of the luna-
tion, or of the year, fome actions of our fyftem be-
come lefs and lefs ; till at length a total quiefcence of
fome part is induced ; which is the commencement
of the paroxyfms of fever, of menftruation, of pain
\\ith decreafed action of the affected organ, and of
confequent convulfion,

I. A

PERIODS OF DISEASES. SECT. XXXVI. 5,

1. A diurnal fever in fome weak people is diftinft-
!y obferved to come on towards evening, and to
ceafe with a moift (kin early in the morning, obey-
ing the folar periods. Perfons of weak conftituti-
ons aie liable to get into better fpirits at the accefs
of the hot fit of this evening fever; and are thence
inclined to fit up late ; which by further enfeebling
them increafes the difeafe ; whence they lofe their
ftrength and their colour.

2. The periods of hectic fever, fuppofed to arife
from abforptionof matter, obeys the diurnal periods
like the above, having the exacerbefcence towards
evening, and its remifiion early in the morning, with
fweats, or diarrhoea, or urine with white fediment.

3. The periods of quotidian fever are either cate-
nated with folar time, and return at the intervals of
twenty-four hours ; or with lunar time, recurring
at the intervals of about twenty-five hours. There
is great ufe in knowing with what circumftances the
periodical return or new morbid motions are con-
joined, as the moil effectual times of exhibiting the
proper medicines are thus determined. So if the
torpor, which ufhers in an ague fit, is catenated
with the lunar day : it is known, when the bark or
opium mud be given, fo as to exert its principal
effect about the time of the expected return. Solid
opium mould be given about an hour before the
expected cold fit ; liquid opium and wine about half
an hour ; the bark repeatedly for fix or eight hours
previous to the expected return.

4. The periods of tertian fevers, reckoned from
the commencement of one cold fit to the commence-
ment of the next cold fit, recur with folar intervals
of forty-eight hours, or with lunar ones of about
fifty hours. When thefe of recurrence begin one
or two hours earlier than the folar period, it (hews,
that the torpor or cold fit is produced by lefs ex-
ternal influence ; and therefore that it is more liable

to

SECT. XXXVI. 3. PERIODS OF DISEASES. 521

to degenerate into a fever with only remiffions ; fo
when menftruation recurs fooner than the period of
lunation, it (hews a tendency of the habit to torpor
or inirritability.

5* The periods of quartan fevers return at folar
intervals of feventy-two hours, or at lunar ones of
about feventy-four hours and an half. This kind of
ague appears mod in moid cold autumns, and in
cold countries replete with marfhes. It is attended
with greater debility, and its cold accefs more dif-
ficult to prevent. For where there is previoufly
a deficiency of fenforial power, the conftitution is
liable to run into greater torpor from any further
diminution of it ; two ounces of bark and fome
fteel fhould be given on the day before the retutn
of the cold paroxyfm, and a pint of wine by de-
grees a few hours before its return, and thirty drops
of laudanum one hour before the expected cold fit.

6. The periods of the gout generally commence
about an hour before fun-rife, which is ufually the
coldeft part of the twenty-four hours. The greater
periods of the gout fee in alfo to obferve the folar
influence, returning about the fame feafon of the
year.

7. The periods of the pleurify recur with exacer-
bation of the pain and fever about fun-fet, at which
time venefeclion is of moft fervice. The fame may
be obferved of the inflammatory rheumatifm, and
other fevers with arterial ftrength, which feem to
obey folar periods ; and thofe with debility feem to
obey lunar ones.

8. The periods of fevers with arterial debility
feem to obey the lunar day, having their accefs daily
nearly an hour later ; and have fometimes two ac-
cefles in a day, refembling the lunar efJe&s upon the
tides.

9. The periods of rhaphania, or convulfions of
the limbs from rheumatic pains, feem to be con-

$si PERIODS OF DISEASES. SECT, xxxvr. £

fie&ed with fblar influence, returning at nearly the
fame hour for weeks together, unlefs difturbed by
the exhibition of powerful dofes of opium.

So the periods of Tuflis ferina, or viokrit cough
with flow pulfe, called nervou's cough, recurs by fo-
lar periods. Five grains of opium given at the time
the cough commenced di fturbed the period, from
feven in the evening to eleven, at which time it re-
gularly returned for fome days, during 'which time
the opium was gradually omitted. Then 120 drops
of laudanum were given an hour before the accefs
of the cough, and it totally ceafed. The laudanum
was continued a fortnight, and then gradually dif-
continued.

10. The periods: of herrricranra, and of painful
epilepfy, are liable to obey lunar periods, both in;
their diurnal returns, and in their greater periods of
•weeks, but are a4fo induced by other exciting
caufes,

ir. The periods of arterial haemorrhages feem ta
return at folar periods about the fame hour of the
evening or morning. Perhaps the venous haemorr-
hages obey the lunar periods, as the catamenia, and
haemorrhoids.

12. The periods of the haemorrhoids, or piles,
in fome fecur monthly, in others only at the greater
lunar influence about the equinoxes.

13-. The periods of hsemoptoe fomefimes obey
folar influence, recurring early in the morning for
feveral days; and fomettmes lanar periods, recur-
ring monthly ; and fometimes depend on our hours
of fleep.' See Clafs I. 2, i. 9.

14. Many of the fifft periods of epileprtic fits obey
the monthly lunation with fome degree of accuracy;
others recur only at the mod powerful lunations
before the vernal equinox, and after the autumnal
one ; but when the conftitution has gained a habit

of

SEC*. XXXVt. 4. ^ERIOtfS OF DISEASES. 523

of relieving difagreeable fenfations by this kind of
exertion, the fit recurs from any flight caufe.

15. The attack of the palfy and apoplexy are
known to recur with great frequency about the equi-
noxes.

1 6. There are numerous inflances of the effect of
the lunations upon the periods of infamty, whence
the name of lunatic has been given to thdfe afflicted
with this difeafe.

IV. The critical days, in which fevers are fup-
pofed to terminate, have employed the attention of
medical philofophefs from the days of Hippocrates
to the prefent time. In whatever part of a lunation
a fever commences, which owes either its whole
caufe to folar and lunar influence, or to this in
conjunction with other caufes ; it would feem, that
the effect would be the greateft at the full and new
moon, as the tides rife higheft at thofe times, and
tvould be the leaft at the quadratures ; thus if a
fever- fit fhould commence at the new or full moon,
occafioned by the folar and lunar attraction dimi-
nifhing fome chemical affinity of the particles of
blood, and thence decfeafing their ftimulus on our
fanguifefous fyftem, as mentioned in Sect. XXXIL
6. this effect will daily decreafe for the firft feven
days, and will then increafe till about the fourteenth
day, and will again decreafe till about the twenty-
firlt day, and increafe again till the end of the lu-
nation. If a fever-fit from the above caufe fhould
commence on the feventh day after either lunation,
the reverfe of the above circumftances would hap-*
pen. Now it is probable, that thofe fevers, whofe
crifis of terminations are influenced by lunations,
may begin at one or other of the above times,
namely at the changes or quadratures ; though fuf-
ficient obfervations have not been made to afcer-
tain this circumftanee. Hence I conclude* that the
fmall-pox and mealies have their critical days, not

VOL. I. Mm governed

KRIODS OF DISEASES SECT. XXXVI. 4,

governed by the times required for certain chemical
changes in the blood, which affect or alter the fti-
mulus of the contagious matter, but from the daily
increafing or decreafing effect of this lunar link of
catenation, as explained in Section XVII. 3. 3. And
as other fevers terminate moil frequently about the
feventh, fourteenth, twenty-firft, or about the end
of four weeks, when no medical afliftance has dif-
turbed their periods, I conclude, that thefe crifes,
or terminations, are governed by periods of the lu-
nations, though we are ftill ignorant of their manner
of operation.

In the diflinft fmall-pox the veftiges of lunation
are very apparent, after inoculation a quarter of a
lunation precedes the commencement of the fever,
another quarter terminates with the complete erup-
tion, another quarter with the complete maturation,,
and another quarter terminates the complete abforp~
tion of a material now rendered inoffenfive to the
confiitution*

SECT,

. XXXViL i DIGESTION, SECRETION, £c.

SECT. XXXVII.

OF DIGESTION, SEC&ETtdtf,

j. Cryflals increase by the greater attraction of their
jutes. Accretion by chemical precipitations, by weld-
ing, by preffure, by agglutination. II. Hunger, di-
gejlion, why it cannot be imitated out of the body.
Lacleals abforb by animal feleflion, or appetency. III.
The glands and pores abforb nutritious particles by
an ima I feleflio n . Organ ic p a r tides of Buffon . Nu-
trition applied at the time of elongation of fbres.
Like inflammation. IV. // feems eafier to have pre-
ferred animals than to reproduce them.. Old age and
death from, inirr liability. Three caufes of this. Ori-
ginal fibres of the organs of fenfe and mufcles un-
changed. - V. Art of producing long life.

I. -THE larger cryftals of faline bodies may be
Conceived to arife from the combination of fmaller
Cryftals of the fame form, owing to the greater at-
tractions of their fides than of their angte. Thus
if four cubes were floating in a fluid, whofe friction
or refinance is nothing, it is certain the fides, of
thefe cubes would attract each other ftronger than
their angles; and hence that thefe four fmaller
cubes would fo arrange themfelves as to produce one
larger one.

There are other means of chemical accretion,

fuch as the depofitions of diflblved calcareous or

filiceous particles, as are feen in the formation of

the ftala&ites of limeftone in Derbyfhire, or of cal-

M m 2 ccdone

S*6 DIGESTION, SECRETION, &c. SECT. XXXVII. *,

cedonc in Cornwall. Other means of adhefion ace
produced by heat and preffure, as in the welding.
of iron bars ; and other means by fimple preffure,
as in forcing two pieces of caoutchou, or elaftic
gum, to adhere ; and lafrly, by the agglutination of
a third fubftance penetrating the pores of the other
two, as in the agglutination of wood by means of
animal gluten. Though the ultimate particles of
animal bodies are held together during life, as welt
as after death, by their J'pecifie attraction of cohe-
fion, like ail other matter; yet it does not appear,
that their original organization was produced by
chemical laws, and their production and-« increafe
muft therefore only be looked for from the laws of
animation.

II. When the pain of hunger requires relief, cer-
tain parts of the material world, which furround;
us, when applied to our palates, excite into action
the mufcles of deglutition ; and the material is
fwallowed into the ftamach. Here the new aliment
becomes mixed with certain animal fluids, and un-
dergoes & chemical procefs, termed digeftion; which
however eherniftry has not yet learnt to imitate out
of the bodies of living animals or vegetables. This
procefs feems very fimilar to the facchasine proeefs
in the lobes of farinaceous feeds, as of barley, when
it begins to germinate; except that, along with
the fugar, oil and mucilage are alfo produced;
which form the chyle of animals, which is very
fimilar to their milk.

The reafon, I imagine, why tBis chyle -making,
or faccharine proeefs, has not yet been imitated by
chemical operations, is owing to the materials be-
ing in fuch a fituation in refpect to warmth, moif-
ture, and motion ; that they will immediately change
into the vinous or acetous fermentation ; except
the new fugar be abforbed by the numerous lac-
teal

»ECT. xxxvii. 3. DIGESTION; SECRETION, &c. 527

teal or lymphatic vefiels, as foon as it is produced .;
which is not eafy to imitate in the laboratory.

Thefc ladeal veffels have mouths, which are ir-
ritated into aflion by the ftimuliis of the fluid,
which fur rounds them ; and t>y animal feledion,
or appetency, they abforb fucli part of the fluid as
is agreeable to their palate ; thofe parts, for in-
ftance, wljich are already converted into chyle, be-
fore they have time to undergo another change by
a vinous or acetous fermentation. This animal ab-
forption of fluid is almoft vifible to the naked eye in
the a&ion of the pun6la lacrymalia ; which im-
bibe the tears from the eye, and difcharge them
again into ihe noftrils.

III. The arteries conftitute another refervoir of a
changeful fluid; from which, after its recent oxy-
genation in the lungs, a further animal feleclion
of various fluids is abforbed by the numerous glands ;
thefe fek(S their refpe&ive fluids from the blood,
which is perpetually undergoing a chemical change ;
but the fele&ion by thefe glands, like that of the
ladleals, which open their mouths into the digefting
aliment in the ftomach, is from animal appetency,
not from chemical affinity ; fecretion cannot there-
fore be imitated in the laboratory, as it con lifts in
a fele&ion of part of a fluid during the cheiiiical
change of that fluid.

The mouths of th£ la&eals, and lymphatics, and
the ultimate terminations of the glands, are finer
than can eafily be .conceived ; yet it is probable,
that the pores, jpr imerllices of ihe parts^ or coats^
which conftitute thefe ultimate veffels, may ftill
have greater tenuity ; and that thefe pores from
the above analogy mu ft poffefs a fimilar power of
irritability, and abforb by their living energy the
particles of fluid adapted to their purpofes, whether
to replace the parts abraded or diffolved, or to
elongate and enlarge themfelves. Not only every

kind

p8 DIGESTION, SECRETION, &c. SECT. XXXVII. 3.

kind of gland is thus endued with its peculiar ap-
petency, and felects the material agreeable to its
tafte from the blood, but every individual pore ac-
quires by animal fele&ion the material, which it
wants ; and thus putrition feems to be performed in
a manner To fimilar tbfecretion, that they only dif-
fer in the one retaining, and the other parting again
with the particles, which they have {elected from
the blood.

This way of accounting for nutrition from fti-
mulus, and the confequent animal feledtion of par-
ticles, is much more analogous to other phenomena
of the animal microcofm, than by having recourfe
to the mierofcopic ariimalcula, or organic particle?
of Buffon andNeedham ; which being already com-
pounded muft themfelves require nutritive particles
to continue their own exiftence. ' And muft be
liable to undergo a change by our digeftive or fe-
cretory organs ; otherwife mankind would foon re-
femble by their theory the animals, which they
feed upon. He, who is nourifhed by beef or ve-
nifon, would in time become horned ; and he, who
feeds on pork or bacon, would gain a nofe proper
for rooting into the earth, as well as for the percep-
tion of odours,

The whole animal fyftem may be confidered as
confiding of the extremities of the nerves, or as
having been produced from them ; if we except
perhaps the medullary part of the brain redding in
the head and fpine, and in the trunks of jhe nerves.
Thefe extremities of the nerves are either of thofe
of locomotion, which aVe termed mufcular fibres;
or of thofe of fenfation, which confti tut e the im-
inediate organs of fenfe, and which have alfo their
peculiar motions. Now as the fibres, which con-
ftitute the bones and membranes, poflefs originally
fenfation and motion ; and are liable again to pof-
fefs them, when tliey become inflamed ; it follows,

that

M. XXXVIf. 3. DIGESTION, SECRETION, &c. 529

that thofe were, when fir ft formed, appendages to
the nerves of fenfation or locomotion, or were form-
ed from them. And that hence all thefe folid parts
of the body, as they have originally confifted of
extremities of nerves, require an apportion of nu-
tritive particles of a fimilar kind, contrary to the
opinion of Buffon and Needham above recited.

Laftly, as all thefe filaments have poffefTed, or
do poffefs, the power of contra&ion, and of confe-
quent inertion or elongation ; it feems probable,
that the nutritive particles are applied during their
times of elongation ; when their original conftitu-
ent particles are removed to a greater diftance from
each other. For each mufeular or fenfual fibre
may be coniidered as a row or firing of beads ;
which approach, when in contraction, and recede
during its reft or elongation ; and our daily expe-
rience fhews us, that great action emaciates the fyf-
tem, and that it is repaired during reft.

Something like this is feen out of the body; for
if a hair, or a fingle untwifted fibre of flax or {ilk,
be foaked in water ; it becomes longer and thicker
by the water, which is abforbed into its pores. Now
if a hair could be fuppofed to be thus immerfed
in a folution of particles fimilar to thofe, which
compofe it ; one may imagine, that it might be
thus increafed in weight and magnitude ; as the par-
ticles of oak- bark increafe the fubftance of the hides
of beafts in the procefs of making leather. I men-
tion theft not as philofophic analogies, but as fi-
miles to facilitate our ideas, how an accretion of
parts may be effected by animal appetences, or fe-
ie&ions, in a manner fomewhat fimilar to mechani-
cal or chemical attractions.

If thole new particles of matter, previoufly pre-
pared by digeflion and fanguification, only fupply
the places of thofe, which have been abraded by
the actions of die fyftem, it is properly termed nu-
trition.

DIGESTION, SECRETION, &c. SECT, XXXVII. 4.

trition. If they arc applied to the extremities qf
the nervous fibrils, or in fuch quantity as to in:-
creafe the length or praifitude of them, the body
becomes at the fame time enlarged, and its growth
is Jncreafed, as well as its deficiencies repaired.

Jr* this laft cafe fqmething more than a fimple.
apportion or feleftion of particles feems to be ne-
cefTary ; as many parts of the fyflem during its
growth are caufect to recede from thofe, with which
they were before in contact ; as the ends of the
bones, or cartilages, recede from each other, as
their growth advances: this procefs refembles in-
flammation, as appears in ophthalmy, or in the
production of new flefh in ulcers, where old veffels
are enlarged, and new ones produced ; and like that
is attended with fenfation. In this fuuation the
veffels become diixcnded with blood, and acquire
greater fenfibility, and may thus be compared to the
erection of the penis, or of the nipples of the breads
of women ; while new particles become added at
the fame time; as in the procefs of nutrition above
defcribed.

When only the natural growth of the various
parts of the Ipody is produced, a pleafurable fenfa-
tion Attends it, as in -youth, and perhaps in thofe,
who are in the progrefs of becoming fat. When
an unnatural growth is the confequence, as in in-
flammatory difeafes, a painful fenfation attends the
enlargement of the fyftem.

IV. This appofition of new parts, a,s the old ones
difappear, felefted from the aliment we talce, firft
enlarges and flrengtheris our bodies for twenty
years, for another twenty years it keeps us in health
and vigour, and adds ftrength knd folidity to the
iyftem ; and then gradually ceafes to nourifli us pro-
perly, and for another twenty years we gradually
link into decay, and finally ceafe to act, and tot
exifL

On

SECT. XXXVII. 4. DIGESTION, SECRETION, &c. $31

On confidering this fubject one ftiould have ima-
gined at firfl view, that it might have been eafier
for nature to have fupportcd her progeny for ever
in health and life, than to have perpetually repro-
duced them by the wonderful and myfterious pro-
cefs of generation. But it feems our bodies by
long habit ceafe to obey the ftimulus of the aliment,
which fhould fupport us. After we have acquired
our height and folidity we make no more new
parts, and the fyftem obeys the irritations, fenfati-
ons, volitions, and aflbciations, with lefs and lefs
energy, till the whole finks into inaction.

Three caufes may confpire to render our nerves
lefs excitable, which have been already mentione<J.
I. If a flimulus be greater than natural, it produces
too great an exertion of the ilimulated organ, and
in confequence exhaufts the fpirit of animation ;
and the moving organ ceafes to act, even though
the ftimulus be continued. And though reft will
recruit this exhauflion, yet fome degree of perma-
nent injury remains, as is evident after expofing the
jeyes long to too ftrong a light. 2. If excitations
weaker than natural be applied, fo as not to excite
the organ into action, (as when frnall dofes of aloe
pr rhubarb are exhibited,) they may be gradually
increafed, without exciting the organ into action ;
which will thus acquire a habit of difobedience to
the ftimulus ; thus by increafing the dofe by de-
grees, great quantities of opium or wine may be
taken without intoxication. See SJfcSt. XII. 3. T.

3. Another mode, by which life is gradually un-
dermined, is when irritative motions continue to
be produced in confequence of ftiinulus, but are
not fucceeded by fenfation ; hence the ftimulus of
contagious matter is not capable of producing fever
•a fecond time, becaufe it is not fucceeded by fen-
fation. See Sect. XII. 3.6. And hence, owing to
the want of the general pleafurable fenfation, which

ought

53* DIGESTION, SECRETION, &c. SECT, XXXVII. 4.

ought to attend digeftion and glandular fecretion,
an irkfomenefs of life enfues ; and, where this is
in greater excefs, the melancholy of old age occurs,
with torpor or debility.

From hence I conclude, that it is probable that
the fibrillas, or moving filaments at the extremities
of the nerves of fenfe, and the fibres which con-
ftitute the mufcles (which are perhaps the only
parts of the fyftem that are endued with contractile
life) are not changed, as we advance in years, like
the other parts of the body ; but only enlarged or
'elongated wiih our growth; and in confequence they
become lefs and lels excitable into adlion. Whence,
inftead of gradually changing the old animal, the
generation of a totally new one becomes neeeffary
with undiminifhed excitability ; which many years
will continue to excite new parts, or new folidity,
and then lofing its excitability in time, periih like
, its parent.

V. From this idea the art of preferving long
health and life may be deduced ; which muft con-
iift in uling no greater flimulus, whether of the
quantity or kind of our food and drink, or of ex-
ternal c ire urn ftances, fuch as heat, and exercife, and
wakefulnefs, than is fufficient to preferve us in vi-
gour ; and gradually, as we grow old, to increafe the
JlimuJus of our aliment, as the inirritabiliiy of our
fyftem increases.

The debilitating effects afcribed by the poet
MARTIAL to the exccffive ufe of warm, bathing in
Italy, may with equal propriety be applied to the
warm rooms of England ; which, wiih the general
exceflive ftirmvlus of fptrituous or fermented liquors-,-
and in fome inftances of immoderate" venery, con-
tribute to fhorten our lives.

Balnea, vina, .venus, corrumpunt corpora noftra,

J-lt fnctunt vitam ba'nca, -vina, •vtnu's !

Wine, women, warmth, againft our lives combi'ne ;

But what is life without waimth, women, wine-!

SECT,

SECT. XXXVIII. i. OXYGEXATION OF BLOQD. jj|

SECT. XXXVIII.

pf THE OXYGENATION OF THE BLOOD !J* TH$
LUNGS, AND IN THE PLACENTA.

f. Blood abforbs oxygene from the air, whence phofpho-
ric acid changes its colour, gives out heat, and fomc
phlogiftic material, and' acquires an ether ial fpirit,
which is dijjipated in fbrous motion. II. The placen-
ta is a pulmonary organ like the gills of fjh. Oxy*
genation of the blood from air, Jrom water, by lungs*
by gills, by the placenta ; necejjity of this oxygena-
tion to quadrupeds, to fjh, to the fatus in utero.
Placenta/ vejfels infer ted into the arteries of the mo-
ther. Ufe of cotyledons in cows. Why quadrupeds
have not fanguiferous lochia. Oxygenation of the
thick in the egg, of feeds. III. The liquor amnii is
not excrementitious. It is nutritious. It is found in
the efophagus and Jtomach, and forms the meconium.
Monftrous births without heads. Q^eflion of Dr.
Harvey.

I. FROM the recent difcoveries of many ingeni-
ous philofophers it appears, that during refpiration
the blood imbibes the vital part of the air, called
oxygene, through the membranes of the lungs ; and
that hence refpiration may be aptly compared to
a flow combuftion. As in combuftion the oxygene
of the atmofphere unites with fome phlogiftic or
inflammable body, and forms an acid (as in the
production of vitriolic acid from fulphur, or car-
bonic acid from charcoal^) giving out at the fame
time a quantity of. the matter of heat ; fo in refpi-
ration

534 OXYGENATION OF BLOOD. SECT. XXXVIII. i.

ration the oxygene of the air unites with the phlo-
giftic part of the blood, and probably produces
phofphoric or animal acid, changing the colour of
the blood from a dark to a bright red ; and proba-
bly fome of the matter of heat is at the fame time
given put according to the theory of Pr. Craw-
ibrd. But as the evolution of heat attends almoft
all chemical combinations, it is probable, that it
alfo attends the fecrerions of the various fluids from
the blood ; and that the conftant combinations or
productions of new fluids by mearjs of the glands
conftitute the more general fource of animal beat ;
this feems evinced by the univerfal evolution of the
matter of heat in the blufh of fharne or of anger ; in
which at the fame time an increafed fecretion of the
perfpirable matter occurs ; and the partial evolution
of it from topical inflammations, as in gout or rheu-
matifm, }n which there is a fecretion of new blood-
veffels.

Some medical philofophers have ^fcribed the beat
of animal bodies to the friction of the particles of
the blood againft the iides of the vefiels. But no
perceptible heat has ever been produced by the agi-
tation of water, or oil, or quickfilver, or other
fluids ; except thofe fluids have undergone at the
fame time fome chemical change, as in agitating
milk or wine, till they become four.

Befides the fuppofed production of phofphorie
acid, and change of .colpur of the blood, and the
production of carbonic acM, there would appear to
be fomething of a more ftjbtile nature perpetually
acquired from the atrnofphere ; which is too fine
to be long contained in animal veffels, and there-
fore requires perpetual renovation ; and without
which life cannot continue longer than a minute or
two ; this ethereal fluid is probably fecreted from
the blood by the brain, and perpetually diflipated
in the aclions of ihe mufcles and organs of fenfe.

That

SICT. XXXVIII i. OXYGENATION O? BLOOD. 535

That the blood requires fomething from the air,
which is immediately neceffary to life, appears from
an experiment of Dr. Hare (Philof.Tranfadt. abridg-
ed, Vol. III. p. 239.) who found, " that birds, mice,
&c. would live as long again in a veffel, where he had
crowded in double the quantity of air by a condenf-
ing engine, than they did when confined in air of
the common denfity." Whereas if fome kind of
deleterious vapour only was exhaled from the blood
in refpiration ; the air, when condenfed into half
ks compafs, could not be fuppofed to receive fcf
much of it.

II. Sir Edward Hulfe, a phyfician of reputation
at the beginning of the prefent century, was of
opinion, that the placenta was a refpiratory organ,
like the gills of nfh, and not an organ to fupply
nutriment to the foetus ; as mentioned in Derham's
Phyfico-theology. Many other phyficians feem to
have efpoufed the fame opinion, as noticed by Ha!*
ler. Elem. Phyfiologise, T. r. Dr. Gipfon publifhed
a defence of this theory in the Medical Eflays of
Edinburgh, Vol. I. and II. which doctrine is there
controverted at large by the late Alexander Monro,
and fince that time the general opinion has been,
that the placenta is an organ of nutrition only,
owing perhaps ra-ther to the authority of fo great a
name, than to the validity of the arguments adduced
in its fupport. The fubjeft has lately been refum-ed
by Dr. James Jeffray, and by Dr. Forefter French-,
in their inaugural diflertations at Edinburgh and at
Cambridge ; who have defended the contrary opi-
nion in an able and ingenious manner ; and from
-whofe Thefes I have extracted many of the follow-
ing remarks*

Firft, by the late difcoveries of Dr. Prieftley, M.
Lavoifier, and other philofophers, it appears, that
the bafis of atmofpherical air, called oxygene, rs-
received by the blood through the membranes of

the

OXYGENATION OF BLOOD. SECT. XXXVlir. i.

the lungs; and that by this addition the colour of
the blood is changed from a dark to a light red.
Secondly, that waier poilefies oxygene alfo as a part
of its compofition, and contains air likewife in its
p:>res; whence the blood of rifh receives oxygene
from the water, or from the air it contains, by
means of their gills, in the fame manner as the
blood is oxygenated in the lungs of air-breathing
animals; it changes its colour at the fame time
from a dark to a light red in the vefTels of their
gills, which- constitute a. pulmonary organ adapted
TO the medium in which they live. Thirdly, that
the placenta- confifts of arteries carrying the blood
to its extremities, and a vein bringing it back, rc-
fembling exactly in ftru£ture the lungs and gills
above mentioned ; and that the blood changes ife
colour from a dark to a light red in palling through
thefe veifels.

This! analogy between the lungs and gills of ani-
mals', and the placenta of the fetus, extends through
a great variety of other circumflances ; thus air-
breathing creatures and fifh can live but a few mr-
nutes without air or water ; or when they are con-
fined in fuch air or water, as has been fpoiled by
rheir own refpiration ; the fame happens to the
fetus, which, as foon as the placenta is feparated
from the uterus, muft either expand its lungs, and
receive air, or die. Hence from the ftructure, as
well as the ufe of tire placema, it appears to be
a refpiratory organ, like the gills of fifh, by which
the blood in the fetus becomes oxygenated.

From the terminations of the placemal veffels not
being obferved to bleed after being torn from the
uterus, while thofe of the uterus effufe a great quan-
tity of florid arterial blood, the terminations of the
plaeental veffels would feem to be inferted into the
arterial ones of the mother 5 and to receive- oxyge-

natioa

2. OXYGEN ATION OF BLOOTJ. $37

nation from the pafling currents of her blood
through their coats or membranes ; which oxyge-
nation is proved by the change of the colour of
the blood irom dark to light red in its paifage from
the placental arteries to the placental vein.

The curious ftrudure of the cavities or lacunas
of the placenta, demonftrated by Mr. J. Hunter,
explain this eircumftance. That ingenious philofo*
pher has fliewn, that there are numerous cavities or
lacunae formed on that iide of the placenta, which
is in contact with the uterus ; thofe cavities or
cells are filled with blood from the maternal arte-
ries, which open into them ; which blood is again
taken up by the maternal veins, and is thus per-
petually changed. While the terminations of the
placental arteries and veins are fpread in tine reticu-
lation on the fides of thefe cells. And thus, as the
growing fetus requires greater oxygenation, an ap-
paratus is produced refembling exactly the air-cells
of the lungs.

In cows, and other ruminating animals, the in-
ternal furface of the uterus is unequal like hollow
cups, which have been called cotyledons ; and into
thefe cavities the prominencies of the numerous pla-
centas, with which the fetus of thofe animals is
furnifhed, are inferted, and ftrictly adhere ; though
they may be extracted without efFufion of blood.
Thefe inequalities of the uterus, and the numerous
placentas in confequence, feern to be defigned for
the purpofe of expanding a greater furface for the
terminations of the placental veflels for the purpofe
of receiving oxygenation from the uterine ones; as
the progeny of this clafs of animals are more com-
pletely formed before their nativity, than that of
the carnivorous clafles, and muft thence in the lat-
ter weeks of pregnancy require greater oxygenation.
Thus calves and lambs can walk about in a few

minutes

#3 OXYGENATIOtt OF BLOOD. SECT. XXXVIIX. $.

minutes after their birth ; while puppies and kittens
remain many days without opening their eyes. And
though on the reparation of the cotyledons of ru-
minating animals no blood is effufed, yet this is
owing clearly to the greater power of con trad ion
of their uterine lacunas or alveoli. See Medical
Mays, Vol. V, page 144. And from the fame caufe
they are not liable to a fangurfer^us menftruation.

The neceffity of the oxygenation of the blood in
the fetus is farther illuflrated by the analogy of the
chick in the egg ; which appears to have its blood
oxygenated at the extremities of the veffels fur-
rounding the yolk j which are fpread on the air-bag
at the broad end of the egg, and may abforb oxy-
gene through that moift membrane from the air
confined behind it ; and which is fhewn by experi-
ments in- the exhaufled receiver to be changeable
though the (hell.

This analogy may eve^n be extended to the grow-
ing feeds of vegetables ; which were fhewn by Mr.
Scheele tor require a renovation of the air over the
water, in w'hicb they were confined. Many vege-
table feeds are furrounded with air in their pods or
receptacles, as peas, the fruit of ftaphylea, and lich-
nis veficaria1 ; but it is probable* that thofe feeds,
after they are fried, as well as the fpawn of fifh, by
the fituation of the former on or near the moid and
aerated furface of the earth, and of the latter in the
ever-changing and ventilated water, may not be in
need of an apparatus for the oxygenation of their
firft blood, before the leaves of one, and the gill*
of the other, are produced for this purpofe*

III. j. There .are many arguments, befides tfie
ltri& analogy between the liquor amnii and the
albumen ovi, which mew the former to be a nutri-
tive fluid ; and that the fetus in the latter months
ef pregnancy takes it into its ftomach j and that

in

SECT. XXX VIII. 3. OXYGEN ATION OF BLOOD. 539

In confequence the placenta is produced for fome
other important purpofe.

Firft, that the liquor amnii is riot an excrementi-
tious fluid is evinced, becaufe it is found in greater
quantity, when the fetus is young, decreafmg after
a certain period till birth. Haller alTerts, " that
in fome animals but a frriall quantity of this fluid
lemains at the birth. In the eggs of hens it is
confumed on the eighteenth day, fo that at the ex-
clufion of the chick fcarcely any remains. In rab-
bits before birth there is none." Elern. Phyfiol.
Had this been an excrerrientitious fluid, the contrary
would probably have occurred. Secondly, the fkin
of the fetus is covered with a whitifh cruft or pel-
licle, which would feem to preclude any idea of the
liquor amnii being produced by any exfudation of
perfpirable matter. And it camiot confift of urine,
becaufe in brute animals the urachus pafles from
the bladder to the alantois for the exprefs purpofe
of carrying off that fluid ; which however in the
human fetus feems to be retained in the diftended
bladder, as the feces are accumulated in the bowels
of all animals.

i. The nutritious quality of the liquid, which
furrounds the fetus, appears from the following con-
fiderations. I. It is coagulable by heat, by nitrous
acid, and by fpirit of wine, like milk, ferum of blood,
and other fluids, which daily experience evinces to
be nutritious. 2. It has a faltifh tafte according to
the accurate Baron Haller, not unlike the whey of
milk, which it even referable* in fmell. 3. The
white -of the egg which conftitutes the food of the
chick, is fhewn to be nutriiious by our daily expe-
rience ; befides the experiment of its nutritidus ef-
fects mentioned by Dr. Fordyce in his late Treatife
on Digeftion, p. 178; who adds, that it much re-
fembles the eflential parts of the ferum of blood.

VOL. I. Nn 3. A

540 OXYGENATION OF BLOOD. SF.CT. XXXVIII. 3.

3. A fluid iimilar to the fluid, with which the
fetus is funounded, except what little change may
be produced by a beginning digeftion, is found in,
the flomach of the f<:tus; and the white of the egg
is found in the fame manner in the llomach of the
chick.

Numerous hairs, fimilar to thofe of its fkin, are
perpetually found among the contents of the (to*
mach in new-bom calves ; which mufl therefore
have licked themfelves before their nativity. Blalii
Anatom. See SedL-XVl. 2. on Inftincl,

The chick in the egg is feen gently to move in
its furrounding fluid, and to open and Onit its mouth
alternately. The fame has been obferved in puppies.
Bailer's El. Phyf. I. 3. p. 201.

A column of ice has been feen to reach down the
cefophagus from the mouth to the ftomach in a fro-
#en fetus ; and this ice was the liquor amnii frozen.

The meconium, or firft faeces, in the bowels of
new-born infants evince, that fomething has been
digefted ; and what could this be but the liquor
amnii together with the recrements of the gaftric
juice and gall, which were neceflary for its digef-
tion ?

There have been recorded fome monftrous births
of animals without heads, and confequently without
mouths, which feem to have been delivered on
doubtful authority, or from inaccurate obfervation.
There are two of fuch monflrous productions how-
ever better attefted ; one of a human fetus, menti-
oned by Gipfon in the Scots Medical EfTays ; which
having the gula impervious was furnifhed with an
aperture into the wind-pipe, which communicated
below into the gullet ; by means of which the liquor
amnii might be taken into the ftomach before nati-
vity without danger of fuffocation, while the fetus
had no occalion to breathe. The other monftrous
fetus is defcribed by Vander Wiel, who afferts, that

he

SECT. XXXVIII.*. OXYGENATION OF BLOOD. $41

he faw a monftrous lamb, which had no mouth, but
initead of it was furnifhed with an opening in the
lower part of the neck into the ftomach. Both
thefe inftances evidently favour the do&rine of the
fetus being nouriilied by the mouth ; as otherwife
there had b^en no neceflity for new or unnatural
apertures into the flomach, when the natural ones
were deficient.

From thefe facls and obfervations we may fafely
infer, that the fetus in the womb is nourifhed by the
fluid which furrounds it; which during the firft
period of geftation is abforbed by the naked lac-
teals ; and is afterwards fvvallowed into the ftomach
and bowels, when thefe organs are perfected ; and
laftly that the placenta is an organ for the purpofe
of giving due oxygenation to the blood of the fetus ;
which is more neceffary, or at lead more frequently
neceflfary, than even the fupply of food.

The queltion of the great Harvey becomes thus
eafily anfwered. <c Why is not the fetus in the
womb fuiTocated for want of air, when it remains
there even to the tenth month without lefpiration;
yet if it be born in the feventh or eighth month,
and has once refpired, it becomes immediately fuf-
focated for want of air, if its refpi ration be ob-
ftruded ?"

For further information on this fubjeft, the reader
is referred to the Tentamen Medicum of Dr. JefFray,
printed at Edinburgh in 1786. And it is hoped
that Dr. French will fome time give his thefes on
this fubjedt to the public.

Nn a SECT

$4* GENERATION. SECT. XXXLX

SECT. XXXIX.

Op GENERATION.

Felix, qui caufas alia crfligihe merfas

Fanclit, et evolvit teuuiilfifta vmcula reru.n. ANO#.

I. Habits of a fling and feeling of individuals attend the font
Into a future life, and attend the new embtyon at the time of
its production J/ie new /peck of entity abforbs nutriment, and
receives oxjgene. Spreads the terminations of its vcjjels on
cells, which communicate with- the arteries of the uterus ;
Jometimet with thofe of the peritoneum. Afterwards It [wal-
lows the liquor amnll, which It produces by its irritation front
the uterus, or peritoneum Like infitis in the heads of
calves and JJieep. Why the white of eg? is of two conjjjlen-
cies. Why nothing Is found In quadrupeds fimllar to the
yolk, nor in mo ft vegetable feeds. II. T. Eggs of frogs and
fijli impregnated out of their bodies Eggs of fowls which art
ndt fecundated, contain only the nutriment for the embryon.
The embryon it produced by the male, and the nutriment bf
the female. Animalcula In femlne. Prcfujton of nature's
births. 2. Vegetables viviparous. Buds and bulbs have each
a father , but no mother. Vcjjcts of the lea£ and bud inofcu-
late. The paternal offspring exaftly refembles the parent. 3,-
Infefls impregnated for Jix generations. Polypus branches like
buds. Creeping roots. Viviparous flowers. Tama, volvox.
Eve from Adarn s rib. Semen not aftimulus to the egg. III.
I. Embryons not originally created within other cmbryons. Or-
ganized matter is not fo minute. 2. Ail the parts of the
embryon are not formed in the male parent. Crabs produce
their legs, worms produce their heads and tails. In wens,
cancers, and inflammations, new veffe/s are formed. Mules
partake of the forms of both parents. Hair and nails grow
by elongation, not by diflention. 3. Organic particles of
Euffon. 1 V. I . Rudiment of the embryon a Jimple living
filament^ becomes a living ringy and then a living tube. 2.

SECT. XXXTX. i. GENE R A. T I O N. 545

// acqui> es nciv in it abilities, and fenfilnlities with new or-
ganizations, as in wnmded f nails, polypi, moths, gna's, tad-
poles. Hence new parts are acquired by addition not by dif+
tcntir.n 3. All parts of the body giow if not confined. 4.
Faujes deficient at their extremities, or have a auplicaturs of
parts. Monfiious bi>th*. Double parts of vegetables. 5.
Afulfs cannot be formed by diftention of ttit feminal ens.
6. Families of animals ft om a mixture of their orders. Mules
impcrfeft. 7. Animal appetency like chemical affinity. Vis
fabricatrix and mcdicatrix of nature. 8. 'I he changes of ani-
mah before and after nativity. Similarity ef their Jlruclure.
Changes in them from luft, hunger, and danger. All warm-
blooded animals derived from one living filament. Cold-blooded
animals, infefls, worms, vegetables, derived alfo from one
living fibmtnt. A'fale animals have teats. Male pigeon
gives milk The world iff elf generated. The caufe of caufcs.
A ftate of probation and rcfpon fib dity. V. I. Efficient cauje
of the colours of birds eggs, and of hair and feathers, which
become white in fnoivy countries. Imagination of the female
colours tie egg Ideas or motions of the retina imitated by the
extremities of the nerves of touch, or rete mucofum. 2. Nu-
triment fupplied by the female of three kinds. Her imagina-
tion can only affefl the fir Jl kind. Mules how produced, and
mulattocs. Organs of reproduction why deficient in mules.
Eggs with double yolks. VI. I. Parlous fecretisns produced
by the extremities of the veffels, as in tJie glands. Contagious
matter. Atfany glands affetted by plcafurable ideas, as thofe
ichich fecreie the Jemcn 2. Snails and worms are herma-
phrodite, yet cannot impregnate themfelves. Final caufe of
this. 3. The imagination of th$ male forms ifa fex. Ideas >
or motions of the nerves of vifwn or of touch, are imitated by
the ultimate etch emitie$ of the glands of the tejies, which mark
the fex. This effefl of the imagination belongs only to the
male. The fex of the embryon is not owing to accident. 4.
•C.aufes of the changes it$ animals from imagination as in mon-
fiers. Frem the male. From the female. 5. Mifcarriages.
from fear. §. Power of the imagination of the male over
the colour, form, and fex of the progeny. An injlance of.
7. Aft of generation accompanied with ideas of the male or .
fcmalejotm. Art of begetting beautiful children of either fex.
VII. Recapitulation. Vlil. Conclujion. Of caufe and ef-
fect. The atomic phi'ofophy leads to a fir ft caufe.

I. THE ingenious Dr. Hartley in his work on
ail;, and ibme other philofophers, have been of

opinion

$44 GENERATION. SECT. XXXIX. i,

opinion, that our immortal part acquires during this
life certain habits of action or of fentiment, which
become for ever indiffoluble, continuing after death
in a future ftate of exiftence j and add, that if thefe
habits are of the malevolent kind, they muft ren-
der the porTeflbr miferable even in heaven. I would
apply this ingenious idea to the ^generation or pro-
duction of the embryon, or new animal, which par-
takes fo much of the form and propenfities of the
parent.

Owing to the imperfection of language the off-
spring is termed a new animal, but is in truth a
branch or elongation of the parent ; fmce a part of
the embryon-animal is, or was, a part of the par
rent; and therefoie in ftiicl: language it cannot be
faid to be entirely new at the time of its produc-
tion; and therefoie it may' retain fome of the habits
of the parent-fyilem.

At the earlieft period of its exiftence the embryon,
as fecreted from the blood of the male, would feem
to confift of a living filament with certain capabi-
lities of irritation, fenfation, volition, and aflbciati-
on ; and alfo with fome acquired habits or propenfi-
ties peculiar to the parent : the former of theie are
in common with other animals ; the latter feem to
diftinguifh or produce the kind of animal, whether
man or quadruped, with the fimilarity of feature
or form to the parent. It is difficult to be conceiv-
ed, that a living entity can be feparated or produced
from the blood by the action of a gland ; and which
fhall afterwards become an animal iimilar to that in,
\vhofe velfels it is formed ; even though we mould
fuppofe with fome modern theories, that the blood
is alive ; yet every other hypothecs concerning ge-
neration refts on principles dill more difficult to our
comprehenlion.

At the time of procreation this fpeck of entity
h received into an appropriated nidus, in which it

mufl

i, GENERATION. 54$

mud acquire two circumftances neceffary to its life
and growth ; one of thefe is food or fuftenance,
which is to be received by the abforberit mouths of
its veffels ; and the other is that pait of atmolphe-
rical air, or of water, which by the new chemiliry
is termed oxygene, and which affecls the blood by
pafiing through the coats of the veffels which con-
tain it. The, fluid furrounding the embryon in its
new habitation, which is called liquor amnii, fup-
plies it with nourilhment ; and as feme air cannot
but be introduced into the uterus along with a new
embryon, it would feem that this fame fluid would
for a fhort time, fuppofe for a tew hours, fupply
likewife a iufficient quantity of the oxygene for its
immediate exiftence.

On this account the vegetable impregnation of
aquatic plants is performed in the air; and it is
probable that the honey-cup or ne&ary of vegetables
requires to be open to the air, that the anthers and
ftigmas of the flower may have food of a more
oxygenated kind than the common vegetable fap-
juice.

On the in'roduclion of this primordium of en-
tity into the uterus, the irritation of the liquor amnii,
which fui rounds it, excites the abibrbent mouths
of the new veffels into action ; they drink up a part
of it, and a pleafurable fenfation accompanies this
new adtion ; at the fame time the chemical affinity
of the oxygene acts through the veffels of the ru*
befcent blood ; and a previous want, or difagreeable
fenfaiion, is relieved by this procefs.

As the want of this oxygenation of the blood is
perpetual, (as appears from the inceffant neceffity
of breathing by lungs or gills,) the veffels become
extended by the efforts of pain or defne to feek
this neceffary object of oxygenation, and to remove
the difagreeable fenfation, which that want occafi-
ons. At the fame time new panicles of matter are

abforbed

GENERATION. SECT. XXXtX. r.

abforbed, or applied to thefe extended veffels, and
they become permanently elongated, as the fluid in.
cPnta& with them foon lofes the oxygenous part,
which it at firft pofTeffed, which was owing to the
introduction of air along with the embryon. Thefe
new blood-veifels approach the fides of the uterus,
and penetrate with their fine terminations into the
veflelsof the mother; or adhere to them, acquiring
oxygene through their coats from the paffmg cur-
rents of the arterial blood of the mother. See SedU

xxxyiii. 2.

This attachment of the placenta! veffels to the irj*
ternal fide of the uterus by their own proper efforts
appears furthe.r illuflrated by the many inftances of
extra-uterine fetufes, which have thus attached or
infer ted tneir veflels into the peritoneum; or on
the vifcera, exadUy in the fame manner as they na-*
turally infert or attach them to the uterus.

The abforbent veflels of the embryon continue to
drink up nourifhment from the fluid in which they
fvvim, or liquor amnii ; and which at firft needs no
previous digeftive preparation ; but which, when the
whole apparatus of digeftion becomes complete, is
fwallowed by the mouth into the ftomach, and be-
ing mixed with faliva, gaftric juice, bile, pancrea-
tic juice, and mucus of the interlines, Becomes di*
gefted, and leaves % recrement, which produces the
firft feces of the infant, called mecpnjum.

The liquor amnii is fecreted into the uterus, as
the fetus requires it, and may proba^y be produced
by the irritation of the fetus as an extraneous body ;
fince a fimilar fluid h acquired from the peritoneum
in cafes of extra-uterine geftatipn. 'The young ca-
terpillars of the gadfly 'placed in the fkins of cows,
3nd the young of the ichneumon-fly placed in the
backs of the caterpillars on cabbages, feem to pro-
duce their nourifhment by their irritating the fides
of their nidus. A vegetable fecretion and concre-
tion is thus produced on oak-leaves by the gall-

infedl,

SECT, XXXIX. i. GENERATION. 54?

infeft, and by the cynips in the bedeguar of the
role; and by the young giafshopper on many plants,
by which the animal luirounds itfelf with froth.
But in no circumllance is extra-uterine geilation fo
cxa&ly refembled as by the eggs of a fly, which are
depofited in the frontal finus of flieep and calves.
Thefe eggs float in fome ounces of fluid collected
in a thin pellicle or hydatide. This bag of fluid
comprefles the optic nerve on one licje, by which
the vifion being lefs diiHncl in that eye, the animal
lurns in perpetual circles towards the fide affecled,
in order to get a more accurate view of objecls ;
for the fame reafon as in fquinting the affected eye
is turned away from the object contemplated. Sheep
in the warm months keep their nofes clofe to the
ground to prevent this fly from fo readily getting
into their noftrils.

The liquor amnii is fecrcted into the womb as it
is required, not only in refpcdl to quantity, but, as
the digcftive ppwers of the fetus become formed, this
jfluid becomes of a different confidence and quality,
till it is exchanged for milk after nativity. Haller-
Phyfiol. V. i. In the egg the white part, which
js analogous to the liquor amnii of quadrupeds,
cpniifls of two jdiftincl: parts ; one of which is more
vifcid, and probably more difficult of digeftion, ^nd
more nutritive than the other ; and this latter is uied
in the lafl week of incubation. r\ he yolk of an egg
is (till a flronger or more nutritive fluid, which is
drawn up into the bowels of the chick juft at its
exclufion from the fhell, and ferves it for nourilh-
rnent for a day or two, till it is able to digeft and
has learnt to choofe the harder feeds or grains,
which are to afford it fuftenance. Nothing analogous
to this yolk is found in the fetus of lactiferous
animals, as the milk is another nutritive fluid ready-
prepared for the young progeny.

The yolk therefore is not neceffary to the fpawn
of fifh, the eggs of infedls, or for the feeds of vege-
tables ;

GENERATION. SECT. XXXTX. a.

tables ; as their embryons have probably their
food prefented to them as foon as they are ex-
cluded from their fhells, or have extended their
roots. Whence it happens that fome infe&s pro-
duce a living progeny in the fpring and fummer,
and eggs in the autumn ; and fome vegetables have
living roots or buds produced in the place of feeds,
as the polygonum viviparum, and magical onions.
See Botanic Garden, p. ii, art. anthoxanthum.

There feems however to be a refervoir of nutri-
ment prepared for fome feeds beiides their catyle-
dons or feed leaves, which may be fuppofed in fome
meafure analogous to the yolk of the egg. Such are
the faccharine juices of apples, grapes and other
fruits, which fupply nutrition to the feeds after they
fall on the ground. And fuch is the milky juice in
the centre of the cocoa-nut, and part of the kernel of
it; the fame I fuppofe of all other monocotyledon
feeds, as of the palms, grafles, and lilies.

II. i. The procefs of generation is full involved
in impenetrable obfcurity, conje&ures may never-
thelefs be formed concerning fome of its circum-
ftances. Firfl, the eggs of fifl\ and frogs are im-
pregnated, after they leave the body of the female,
becaufe they are depofited in a fluid, and are not
therefore covered with a hard {hell. ; It is however
remarkable, that neither frogs nor fifh will part
with their fpawn without the prefence of the male;
on which account female carp and gold-fifh in fmall
ponds, where there are no males, frequently die
from the diftention of their growing fpawn. 2.
The eggs of fowls, which are laid without being
impregLared, aie feen to contain only the yolk and
•white, which are evidently the food or fultenance
for the future chick. 3. As the cicatricula of thefe
eggs is given by the cock, and is evidently the ru-
diment of the new animal, we may conclude, that the
embryon is produced by the male, and the proper food

and

SF.CT. XXXIX. a. GENERATION.

and nidus by the female. For if the female be
fuppofed to form an equal part of the embryon,
why fhould fhe form the whole of the apparatus for
nutriment and for oxygenation ? the male in many
animals is larger, ihonger, and digefls more food
than the female, and therefore mould contribute as
much or more towards the reprodu&ion of the fpe-
cies ; but if he contributes only half the embvyon and
none of the apparatues for fuiienance and oxygena-
tion, the diviiion is ui equal ; the itrength ot trie
male, and his confumption of food are too great
for the effect, compared with that of the female,
which is contrary to the ufual courle of nature.

In objection to this theory of generation it may
be faid, if the animalcula in femine, as feen by the
microfcope, be all of them rudiments of homunculi,
when but one of them can find a nidus, what a
wafte nature has made of her productions ? I do not
aflert that thefe moving particles, vilible by the mir
crofcope, are homunciones ; perhaps they may be
the creatures of ftagnation or putridity, or perhaps
no creatures at all ; but if they are fuppofed to be
rudiments of hoinunculi, or embryons, fuch a pro-
fufion of them correfponds with the general effort
of natufe to provide for the continuance of her
fpecies of animals. Every individual tree produces
innumerable feeds, and every individual fifh innume-
rable fpawn, in fuch inconceivable abundance as
would in a fhort fpace of time ciov.d the earth and
ocean with inhabitants, and thefe are much more
perfect animals than the animalcula in femine can
be fuppofed to be, and perifh in uncounted milli-
ons. This argument only fhevvs, that the producti-
ons of nature are governed by general laws, and
that by a wife fuperfluity of provifion fhe has en-
fured their continuance.

2. That the embryon is fecreted or produced by
the male, and not by the conjunction of fluids from
t>oth male and female, appears from the analogy of

vegetable

GENERATION. SECT. XXX IX. a.

vegetable feeds. In the large flowers, as the tulip,
there is no fimilarity of apparatus between the an-
thers and the ftigma : the feed is produced accord-
ing to the obfervations of Spallanzani long before
the flowers open, and in confequence long before it
can be impregnated, like the egg in the pullet. And
after the prolific duft is {hed on the ftigma, the feed
becomes coagula'ed in one point firft, like the catri-
cula of the impregnated egg> See Botanic Garden,
Part I. additional note 38. Now in thefe fimple
produces of nature, if the female contributed to
produce the new embryon equally with the male,
there would probably have been fome vilible fimi-
larity of parts for this purpofe, befides thofe necef-
fary for the nidus and fuftenance of the new pro-
geny. Befides in many flowers the males are more
numerous than the females, or than the feparate ute-
rine cells in their germs, which would (hew, that
the office of the male was at lead as important as
that of the female ; whereas if the female, befides
producing the egg or feed, was to produce an equal
part of the embryon, the office of reproduction,
would be unequally divided between them.

Add to this, that in the moft fimple kind of ve-
getable reproduction, I mean the buds of trees,
which are their viviparous offspring, the leaf is evi-
dently the parent of the bud, which rifes in its
bofom, according to the obfervation of Linnaeus.
This leaf confifts of abforbent veffels, and pulmo-
nary ones, to obtain its nutriment, and to impreg-
nate it with oxygene. This fimple piece of living
organization is allo furnifhed with a power of re-
production ; and as the new offspring is thus fup-
ported adhering to its father, it needs no mother
to fupply it with a nidus, and nutriment, and axy-
genation; and hence no female leaf has exiftence.

I conceive that the veffels between the bud and
the leaf communicate or inofculate ; and that the
bud is thus ferved with vegetable blood, that is,

with

S^cr. XXXIX. 2. GENERATION. 551

with both nutriment and oxygenation, till the death
of the parent-leaf in autumn. And in this refpeft
it differs from the fetus of viviparous animals. Se-
condly, that then the bark-verTels belonging to the
dead-leaf, and in which I fuppofe a kind of manna
to have been depofited, become now the placenta!
veflcls, if they may be fo called, of the new bud.
Irom the vernal fap thus produced of one fugar-
maple-ffee in New York and in Pennfylvania, five
or fix pounds of good fugar may be made annually
without defhoying the tree. Account of maple-fugar
by B. Ruirr. London, Phillips. (See Botanic Garden,
Part I. additional note on vegetable placentation.)

Thefe veflels, when the warmth of the vernal fun
hatches the young bud, ferve it with a faccharine
nutriment, till it acquires leaves of its own, and
{hoots a new fyftem of abforbents down the bark
and root of the tree, juft as the farinaceous or oily
matter in feeds, and the faccharine matter in fruits,
ferve their embryons with nutriment, till they ac-
quire leaves and roots. This analogy is as foiceable
in fo obfcure a fubject, as it is curious, and may in
large buds, as of the horfe-chefnut, be almoft feen
by the naked eye ; if with a pen-knife the remain-
ing rudiment of the lad year's leaf, and of the
new bud in its bofom, be cut away flice by flice.
The feven ribs of the laft year's leaif will be feen to
have arifen from the pith in feven diflindl points
making a curve ; and the new bud to have been
produced in their centre, and to have pierced the
alburnum and cortex, and grown without the afiiit*
ance of a mother. A fimilar procefs may be feen
oa differing a tulip root in winter ; the leaves, which
inclofed the la(t year's flower-ftalk, were not necef-
fary for the flower ; but each of thefe was the father
of a new bud, which may be now found at its bafe ; and
which, as it adheres to the parent,requiredno mother.

This paternal offspring of vegetables, I mean their
buds and bulbs, is attended with a very curious cir-

cumftance ;

GENERATION. SECT. XXXIX. *.

ctimftance ; and that is, that they exaftly referable
their parents, as is obfeivable in grafting fruit-trees,
and in propagating flower-roots ; whereas the femi-
nal offspring of plants, being fupplied with nutri-
ment by the mother, is liable to perpetual variation.
Thus alfo in the vegetable clafs dioicia, where the
male flowers are produced on one tree, and the fe-
male ones on another, the buds of the male trees
uniformly produce either male flowers, or other
buds fimilar to themfelve^ ; and the buds of the fe-
male trees produce either female flowers, or other
buds fimilar to themfelves ; whereas the feeds of
thefe trees produce either male or female plants.
From this analogy of the production of vegetable
buds without a mother, I contend that the mother
<foes not contribute to the formation of the living
ens in animal generation, but is neceflary only for
fupplying its nutriment and oxygenation.

There is another vegetable fadt publifhed by M.
Koelreuter, which he calls " a complete metamor-
phofis of one natural fpecies of plants into ano-
ther/* which (hews, that in feeds as well as in buds,
the embryon proceeds from the male parent, though
the form of the fubfequent mature plant is in part
dependant on the female. M. Koelreuter impreg-
nated a ftigma of the nicotiana ruftica with the fa-
rina of the nicotiana paniculata, and obtained pro-
lific feeds from it. With the plants which fpiung
from thefe feeds, he repeated the experiment, im-
pregnating them with the farina of the nicotiana
paniculata. As the mule plants which he thus pro-
duced were prolific, he continued to impregnate
them for many generations with the farina of the
nicotiana paniculata, and they became more and more
like the male parent, till he at length obtained fix
plants in every refpedt perfectly fimilar to the nico-
tiana paniculata , and iij no refpeft refembling their

female

SECT. XXXIX. 2. GENERATION. 553

female parent the nicotiana ruftica. Blumenbach on
Generation.

3. It is probable that the infects, which are faid
to require but one impregnation for fix generations,
ar. the aphis (fee Amenit. Academ.) produce their
progeny in the manner above dtfcribed, that is,
without a mother, and not without a father ; and
thus experience a lucina fine concubitu. Thofe who
have atten ed to the habits of the polypus, which
is found in the ftagnant water of our ditches in
July, affirm, that the young ones branch out from
the ficle of the parent like the buds of trees, and
after a time feparate themfelves from them. This
is fo analogous to the manner in which the buds of
trees appear to be produced, that thefe polypi maybe
confitiered as all male animals, producing embryons,
which require no mother to fupply them with a nidus,
or with nutriment, and oxygenation.

This lateral or lineal generation of plants, not
only obtains in the buds of trees, which continue
to adhere to them, but is beautifully feen in the
wires of knot-grafs, polygonum aviculare, and in
thofe of ftraw berries, fragaria vefca. In thefe an
elongated creeping bud is protruded, and, where it
touches the ground, takes root, and produces a new
plant derived from its father, from which it acquires
both nutriment and oxygenation; and in confe-
quence needs no maternal apparatus for thefe pur-
pofes. In viviparous flowers, as thofe of allium
magicum, and polygonum viviparum, the anthers
and the ftigmas become effete and perifh ; and the
lateral or paternal offspring fucceeds inftead of feeds,
which adhere till they are fufficiently mature, and
then fall upon the ground, and take root like other
bulbs.

The lateral production of plants by wires, while
each new plant is thus chained to its parent, and
continues to put forth another and another, as the.

wire

$44 G E Nf £ R A T I O &. SECT. XXXIX z,

wire creep's onward on the ground, is exactly re-
fembled by the tape-worm, or taenia, fo often foirnd
In the bowels, ftretching itfelf in a chain quite from
the ftomach to the rec~lum. Linnaeus aflerts, " that
it grows old at one extremity, while it continues to
generate young 6nes at the other, proceeding ad
hifinitum, like a root of graft. The feparate joints
are called gourd-worms,' and propagate new joints
like the parent without end, each joint being fur*
mined with its' proper mouth, and organs of digef-
fion." Syflema naturae. Vermes tenia. In this
animal there evidently appears a power of reproduc-
tion without ally maternal apparatus for the purpofe
6f fupplying nutriment and oxygenation to the em-
bryon, as it remains attached to hs father till its
irraturrty. The volvox globator, which is a tranf-
parent animal, is faM by Linnaeus to bear within it
fons and grand- fons fo the fifth generation;. Thefe
are probably living fetufes, produced by the father,
of different degrees of maturity, to be detruded at
different periods of time, like the unimpregnated
eggs of various fizes, which are found m poultry ;
and as they are produced without any known co-
pulation, contribute to evince, that the living em-
bryon i:n other orders of animals is formed by the
male-parent, and not by the mother, as one parent
has the power to produce it.

Thrs idea of the reproduction of animals from a
iingle living filament of their fathers, appears to
have been fhadowed or allegorized in the curious
account in facred writ of the formation of Eve from
a rib of Adam.

From all thefe analogies I conclude, that the em-
bryon is produced folely by the male, and that the
female fupplies it with a proper nidus, with fufte-
nance, and with oxygjenation ; and that the idea of
the femen of the male conflitutirig only a flimulus
to the egg of the female, exciting it into life, (as

bdtt

SECT. XXXIX. 3- GENERATION. 555

held by fome philofophcrs) has no fupport from ex-
periment or analogy.

III. i. Many ingenious philofophers have found
fo great difficulty in conceiving the manner of the
reproduction of animals, that they have fuppofed
all the numerous progeny to have exifted in minia-
ture in the animal originally created ; and that thefe
infinitely minute forms are only evolved or diftend-
cd, as the embryon increafes in the womb. This
idea, befides its being unfupported by any analogy
we are acquainted with, afcribes a greater tenuity
to organized matter, than we can readily admit ; as
thefe included embryons are fuppofed each of them
to confift of the various and complicate parts of ani-
mal bodies; they muft poflefsa much greater degree
of minutenefs, than that which was afcribed to the
devils that tempted St. Anthony ; of whom 20,000
were faid to have been able to dance a faraband on
the point of the fineft needle without incommoding
each other.

2. Others have fuppofed, that all the parts of the
embryon are formed in the male, previous to its
being depofited in the egg or uterus ; and that it is
then only to have its parts evolved or diftended as
mentioned above ; but this is only to get rid of one
difficulty by propoiing another equally incompre-
hcnfible : they found it difficult to conceive, how
the embryon could be formed in the uterus or egg,
and therefore wifhed it to be formed before it came
thither. In anfwer to both thefe doctrines it may
be obferved, ift, that fome animals, as the crab-
fifli, can reproduce a whole lirnb, as a leg which
has been broken off; others, as worms and fnails,
can reproduce a head or a tail, when either of them
has been cut away ; and that hence in thefe animals
at lead a part can be formed anew, which cannot be
fuppofed to have exifted previouily in miniature.

VOL. I. O o Secondly,

55* GENERATION. S*CT. XXXIX.

Secondly, there are new pans or new vefTels pro*
duced in many difeafes, as on the cornea of the
eye in ophthalmy, in wens and cancers, which can-
not be fuppofed to have had a prototype or original
miniature in the embryon.

. Thirdly, how coutd mule-animals be produced',
which partake of the forms of both the parents, if"
the original embryon was a* miniature exifting in the
femen of the male parent ?' if an embryon of the-
male afs was only expanded, no- refsmblance to the
mare could exift hi the mule.*

This miftaken idea of the extenfion of parts feems
to have had its rife from the mature man "refemblingf
the general form of the fetus ; and from thence it-
Was believed, that the parts of the fetus were dif-
tended into the man ; whereas they have increafed
loo times in weight, as well as TOO times in fize ;
BOW no one will call the additional 99 parts a dif-
tendon of the original one part in refpecl: to weight.
Thus the uterus during pregnancy is greatly en-
larged in thicknefs and folidity as well as in capa-
city, and hence muft have acquired thisx additional
fize by accretion of new parts, not by an extenfion
•f the old ones ; the familiar a& of blowing up
the bladder of an animal recently flaughtered has
led our imaginations to apply this idea of diftention
to the increafe of fize from natural growth; whicb
however muft be owing to the apportion of new
parts ; as it is evinced from the increafe of weight
along with the increafe of dimenfion ; and is even
vifible to our eyes in the elongation of our hair
from the colour of its ends ; or when it has been
dyed on th£ head ; and in the growth of our nails
from the fpecks fometimes obfervable on them ; and
in the inereafe of the white crefcent at their roots,
and in the growth of new flefh in wounds, which
eonfifts of new nerves as well as of new blood-vef-
fels.

SECT. XXXIX. 4: GENERATION. 557

3. Laftly, Mr. Buffon has with great ingenuity
imagined the exiftence of certain organic particles,
which are fuppofed to be partly alive, and partly
mechanic fprings. The latter of thefe were difco-
vered by Mr. Needham in the milt or male organ
of a fpecies of cuttle fifh, called calmar ; the for-
mer, or living animalcula, are found in both male
and female fecretions, in the infulions of feeds, as
of pepper, in the jelly of roafted veal, and in all
other animal and vegetable fubftances. Thefe orga-
nic particles he fuppofes to exift in the fpermatic
fluids of both fexes, and that they are derived thi-
ther from every part of the body, and muft there-
fore referable, as he fuppofes, the parts from whence
they are derived. Thele organic particles he be-
lieves to be in conftant activity, till they become
mixed in the womb, and then they inftantly join
and produce an embryon or fetus fimilar to the two
parents.

Many objections might be adduced to this fanci*
ful theory ; I fhall only mention two. Firft, that
it is analogous to no known animal laws. And
fecondly, that as thefe fluids, replete with organic
particles derived both from the male and female or-
gans, are fuppofed to be firnilar; there is no reafon
why the mother Ihould not produce a female em-
bryon without the afliftance of the male, ?rd real-
ize the lucina fine concubitu.

IV. i. I conceive the primordium, orfrudiment
of the embryon, as fecreted from the blood of the
parent, to confift of a fimple living filament as a
mufcular fibre ; which I fuppofe 10 be an extremity
of a nerve of loco-motion, as a fibre of the retina is
an extremity of a nerve of fenfation ^ as for inftance
one of the fibrils, which eompofe the mouth of an
abforbent veflel ; I fuppofe this living filament, of
whatever form it may be, whether fphere, cube, or
cylinder, to be endued with the capability of being
O o 2 excited

GENERATION. SECT. XXXIX. 4.

excited into a&ion by certain kinds of ftimulus.
By the ftimulus of the furrounding fluid, in which
it is received from the male, it may bend into a
ring, and thus form the beginning of a tube. Such
moving filaments, and fuch rings, are defcribed by
thofe, who have attended to microfcopic animalcule.
This living ring may now embrace or abforb a nu-
tritive particle of the fluid, in which it fwims ; and
by drawing it into its pores, or joining it by com-
preflion to its extremities, may increafe its own
length or eraffuude ; and by degrees the living ring
may become a living tube.

2. With this new organization, or accretion of
parts, new kinds of irritability may commence ; for
fo long as there was but one living organ, it could
only be fuppofed to pofiefs irritability ; fmce fenfi-
bility may be conceived to be an extenfion of the
effect of irritability over the reft of the fyftem.
Thefe new kinds of irritability and of fenfibility in
confequence of new organization, appear from va-
riety of fadls in the more mature animal ; thus the
formation of the teftes, and confequent fecretion of
the femen, occaiion the paffion of lufl ; the lungs
muft be previoufly formed before their exertions to
obtain frefh air can exift ; the throat or oefophagus
muft be formed previous to the fenfation or appe-
tites a& hunger and thirft ; one of which feems to
refide at the upper end, and the other at the lower
end of that canal.

Thus alfo the glans penis, which is diftended
with blood, acquires a new fenfibility, and a new
appetency. The fame occurs to the nipples of the
breafts of female animals, when they are diftended
with blood, they acquire the new appetency of
giving milk. So inflamed tendons and membranes,
and even bones, acquire new fenfations ; and the
parts of mutilated animals, as of wounded fnails,
and polypi, and crabs, are reproduced ; and at the

fame

SECT. XXXIX. 4. GENERATION. 559

fame time acquire fenfations adapted to their fuua-
tions. Thus when the head of a fnail is reproduced
after decollation with a fharp rafor, thofe carious
telefcopic eyes are alfo reproduced, and acquire
their fenfibility to light, as well as their adapted
mufcles for retra6lion on the approach of injury.

With every new change, therefore, of organic
form, or addition of organic parts, I fuppofe a new
kind of irritability or of fenfibility to be produced ;
fuch varieties of irritability or of fenfibility exifl
in our adult (late in the glands : every one of which
is furnifhed with an irritability, or a tafte, or ap-
petency, and a confequent mode of adlion peculiar
to itfelf.

In this manner I conceive the veffels of the- jaws
to produce thofe of the teeth, thofe of the fingers
to produce the nails, thofe of the (kin to produce
the hair ; in the fame manner as afterwards about
the age of puberty the beard and other great changes
in the form of the body, and difpofition of the
mind, are produced in confequence of the new fe-
cretion of femen ; for if the animal is deprived of
this fecretion thofe changes do not take place. Thefe
changes I conceive to be formed not by elongation
or diftention of primeval ftamina, but by appofition
of parts ; as the mature crab-fifh, when deprived of
a limb, in a certain fpace of time has power to re-
generate it ; and the tadpole puts forth its feet long
after its exclufion from the fpawn ; and the cater-
pillar in changing into a butterfly acquires a new
form, with new powers, new fenfations, and new
defires.

The natural hiftory of butterflies, and moths, and
beetles, and gnats, is full of curiofity ; fome of
them pafs many months, and others even years, in
their caterpillar or grub flate ; they then reft many
weeks without food, fufpended in the air, buried
in the earth, or fubmerfed in water ; and change

themfelves

$6o GENERATION. SJ.CT. XXXIX. 4,

themfelves during this time into an animal appa-
rently of a different nature ; the ftomachs of fome
of them, which before digefted vegetable leaves or
roots, now only digeft honey ; they have acquired
wings for the purpofe of feeking this new food, and
a long probofcis to collecl it from flowers, and I
fuppofe a fenfe of fmeli to detect the fee ret places
in flowers, where it is formed. The moths, which
fly by night, have a much longer probofcis rolled
up under their chins like a watch fpring ; which
they extend to collecl the honey from flowers in
their fleeping ftate ; when they are clofed, and the
neclaries in confequence more difficult to be plun-
dered. The beetle kind are furnifhed with an ex-
ternal covering of a hard material lo 'their wings,
that they may occafionally again make holes in the
earth, in which they pafled the former ftate of their
exiilence.

But what moft of all diftinguifhes thefe new ani-
mals is, that they arc new furnifhed with the powers
of reproduction ; an<J that they now differ from
each other in fex, which does not appear in
their caterpillar or grub ftate. In fome of them the
change from a caterpillar into a butterfly or moth
feems to be accomplifhed for the fole purpofe of
their propagation ; iince they immediately die after
this is finifhed, and take no food in the interim, as
the lilk-worm in this climate ; though it is poflible,
it might take honey as food, if it was prefented no
it. For in general it would feem, that food of a
more ftimulating kind, the honey of vegetables in-
ftead of their leaves, was necefiary for the purpofe
of the feminal reprodu&ion of thefe animals, ex-
a6tly iimilar to what happens in vegetables ; in
thefe the juices of the earth are fufficient for their
purpofe of reproduction by buds or bulbs; in which
the new plant feems to be formed by irritative mo-
tions, like the growth of their other parts, as their

leaves

SECT. XXXIX. 4. GENERATION, 561

leaves or roots ; but for the purpoie of feminal or
amatorial reproduction, where fenfution is required,
a ,more flimulating food becomes neceflary for the
anther, and fligma ; and this food is honey ; as ex-
plained in Sect. XIII. on Vegetable Animation.

The gnat and the tadpole referable each other in
.their change from natant animals with gills into
-aerial animals with lungs ; and in their change of
the element in which they live; and probably of the
food, with which they are fupported; and laftly,
with their acquiring in their new Mate the difference
of fex, and the organs of feminal or amatorial re-
production. While the polypus, who is their com-
panion in their former itate of life* not being al-
lowed to change bis form and element, can only
propagate like vegetable buds by the fame kind of
irritative motions, which produces the growth of
Jiis own body, without the feminal or amatorial
propagation, which requires fenfation, and which
•in gnats and tadpoles feemsto require a change both
of food and of refpiratiou.

From hence I conclude, that with the aequifitiGa
of new pans, new fenfations., and .new detires, as
well as new powers, are produced; and this by ac^
cretion to xhe old orues, and not by diitention of
them. And finally, that the rnoft effential parts of
the fyftem, as the brain for the purpofe of diitri-
buting the power of life, and the placenta for the
purpofe of oxygenating the blood, and the additi-
onal abforbent veffels for the purpofe of acquiring
aliment, are firft formed by the irritations above
mentioned, and by the pleafurable fenfations attend-
ing thoie irritations, and by the exertions in confe-
quence of painful fenfations, fimilar to thofe of
hunger and fufFocation. After thefe an apparatus of
limbs for future ufes, or for the purpofe of moving
.the body in its prefent natant itate, and of lungs for
future refpiration, and of teltes for future repro-

duclion,

564 GENERATION. SECT. XXXIX. 4.

duction, are foj^ned by the irritations and fenfations,
and confequent exertions of the parts previoufly ex-
ifting, and to which the new parts are to be at-
tached.

3. In confirmation of thefe ideas it may be ob-
ferved, that all the parts of the body endeavour to
grow, or to make additional parts to theinfelyes
throughout our lives ; but are reftrained by the parts
immediately containing them ; thus, if the fkin be
taken away, the flefhy parts beneath foon moot out
new granulations, called by the vulgar proud flefh.
If the periofteum be removed, a fimjlar growth com-
mences from the bone. Now in the cafe of the
imperfect embryon, the containing or confining parts
are not yet fuppofed to be formed, and hence there
is nothing to reftrain its growth.

4. By the parts of the embryon being thus pro-
duced by new apportions, many phenomena both
of animal and vegetable productions receive an ea-
iier explanation ; fuch as that many fetufes are defi-
cient at the extremities, as in a finger or a toe, or
in the end of the tongue, or in what is called a
hare-lip with deficiency of the palate. Por if there
fhould bq a. deficiency in the quantity of the firft
nutritive particles laid up in the egg for the recep-
tion of the firft living filament, the extreme parts,
as being lad formed, muft fhe\y this deficiency by
their being imperfect.

This idea of the growth of the embryon accord*
alfo with the' production of fome monftrqus girths,
which confift of a duplicature of the limbs, as chick-
ens with four legs ; which could not occur, if the
fetus was formed by the diftentioi} of an original
ftamen, or miniature. For if there fhould be a fu-
perfluity of the firft nutritive particles laid up in the
egg for the firft living filament ; it is eafy to con-
ceive, that a duplicature of fome parts may be form-
ed. And that fuch fuperfluous nourifhment fome-

times

S*CT. XXXIX. 4. GENERATION. 563

times exifts, is evinced by the double yolks in fome
eggs, which I fuppofe were thus formed previous to
their impregnation by the exuberant nutriment of
the hen.

This idea is confirmed by the analogy of the mon-
flers in the vegetable world alfo ; in which a dupli-
cate or triplicate production of various parts of the
flower is obfervable, as a triple pedtary in fome co-
lumbines, and a triple petal in fome primrofes ; and
which are fuppofed to be produced by abundant nou-
rimment.

5. If the embryon be received into a fluid, whofc
ftimulus is different in fome degree from the natu-
ral, as in the production of mule-animals, the new
irritabilities or fenfibilities acquired by the increaf-
ing ©r growing organized parts may differ, and
thence produce parts not fimilar to the father, but
of a kind belonging in part tp .the mother ; and thus,
though the original ilamen or living ens was de-
rived totally from the father, yet new irritabilities or
fenfibilities being excited, a change of form corref-
ponding with them ^will be produced. Nor could
the production of mules exift, if the flamen or
miniature of all the parts of the embryon is previ-
ouily formed in the male femen, and is only dif-
tended by nou rimment in the female uterus. Where-
as this difficulty ceafes, if the embryon be fuppofed
to confift of a living filament, which acquires or
makes new parts with new irritabilities, as it ad-
vances in its growth.

The form, folidity, and colour, of the particles
of nutriment laid up for the reception of the firft
living filament, as well as their peculiar kind of
ftimulus, may contribute to produce a difference in
the form, folidity, and colour of the fetus, fo as
to referable the mother, as it advances in life. This
alfo may efpecially happen during the firft ftate of
the exiftence of the embryon, before it has ac-
quired

5^4 GENERATION. SECT. XXXIX. 4.

quired organs, which can change thefe firft nutritive
particles, as explained in No. 5. 2. of this Section.
And as thefe nutritive particles are fuppofed to be
fimilar to thofe, which are formed for her own nu-
trition, it follows that the fetus fhould fo far refem-
ble the mother.

This explains, why hereditary difeafes may be de-
rived either from the male or female parent, as well
as the peculiar form of either of their bodies. Some
of thefe hereditary difeafes are fimply owing to a
deficient activity of a part of the fyftem, as of the
abibrbent veifels, which open into the cells or cavi-
ties of the body, and thus occalion dropiies. Others
are at the fame time owing to an increafe of fenfa-
tion, as in fcropbula and confumption ; in thefe the
obstruction of the fluids is firft caufed by the inirri-
lability of the vefiels, and the inflammation and ul-
cers which fucceed, are caufed by the confequent
increafe of fenfation in the obftructed part. Other
hereditary difeafes, as the epilepfy, and other con-
vulfions, confiil in too great voluntary exertions in
confequence of difagreeable fenfation in fome parti-
cular difeafed part. Mow as the pains, which oc-
cafio& thefe convulfions, are owing to defect of the
action of the difeafed part, as (hewn in Sect. XXXIV.
it is plain, that all thefe hereditary difeafes may have
their origin either from defective irritability derived
from the father, or from deficiency of the ftimulus
of the nutriment derived from the mother. In ei-
ther cafe the effect would be fimilar ; as a fcrophu*
lous race is frequently produced among the poor
from the deficient (limulus of bad diet, or of hun-.
ger ; and among the rich, by a deficient irritability
from their having beeii long accuftomed to* too
great ftimulufl, as of vinous fpirit.

6. From this account of reproduction it appears,
that all animals have a fimilar origin, viz. from a
Tingle living filament 5 and that the difference of

their

Sicr. XXXIX. 4. GENERATION. 565

their forms and qualities has arifen only fromthe
different irritabilities and fenfibilities, or volunta-
rities, or afTociabilities, of this original living fila-
ment; and perhaps in fome degree from the differ*
ent forms of the particles of the fluids, by which
}t has been at firft Simulated into a&ivity. And
that from hence, as Linnseus has conjectured in re-
ipecl to the vegetable world, it is not impoffible,
but the great variety of fpecies of animals, which
now tenant tjie earth, may have had their origin
from the mixture of a few natural orders. And
that thofe animal and vegetable mules, which could
continue their fpecies, have done fo, and conftitute
the numerous families of animals and vegetables
which now exift ; and that thofe mules, which were
produced with imperfrcl organs of generation, pe-
rifhed without reproduction, according to the ob-
fervation of Ariftotle; and are the animals, which
we now call mules. See Botanic Garden, Part IL
Note on Diamhus.

Such a promifcuous intercourfe of animals is faid
$o exift at this day in New South Wales by Captain
Hunter. And that not only aoiongft the quadru-
peds and birds of different kinds, but even amongft
the fifh, and, as he believes, amongft the vegetablest
He fpeaks of an Animal between the opoffum and
the kangaroo, from the fize of a fheep to that of a
rat. Many fifh feemed to partake of the (hark;
fome ivith a Ikait's head and (houlders, and the
hind part *of a fhark ; others with a fhark's head
and the body of a mullet ; and fome with a fhark's
head and the flat body of a ii ing-ray. Many birds
partake of the parrot ; fome have the head, neck,
and bill of a parrot, with long ftraight feet and legs;
others with legs and feet of a parrot, w Lh head and
neck of a fea gull. Voyage to South Wales by
Captain John Hunter, p. 68.

7. All

566 GENERATION. SECT. XXXIX. 4t

7. All animals therefore, I contend, have a fimi-
lar caufe of their organization, originating from a
fingle living filament, endued indeed with different
kinds of irritabilities and fenfibilities, 'or of animal
appetencies ; which exift in every gland, and in
every moving organ of the body, and are as eflen-
tial to living organization as chemical affinities are
to certain combinations of inanimate matter.

If I might be indulged to make a firnile in a phi-
lofophical work, I fhould fay, that the animal ap-
petencies are not only perhaps lefs numerous ori-
ginally than the chemical affinities ; but that like
thefe latter, they change with every new combina-
tion ; thus vital air and azote, when combined,
produce nitrous acid ; which now acquires the
property of diflblving filver ; fo with every new-
additional part to the embryon, as of the throat or
lungs, I fuppofe a new animal appetency to be pro-
duced.

In this early formation of the embryon from the
irritabilities, fenfibilities, and affociabilities, and
confequent appetencies, the faculty of volition can
fcarcely be fuppofed to have had its birth. ; For
about what cannhe fetus deliberate, when it has not
choice of objects ? But in the more advanced flate
of the fetus, it evidently poffeffes volition ; as it
frequently changes its attitude, though it feems to
ileep the greateft part of its time; and afterwards
the power of volition contributes to change or alter
many parts of the body during its growth to man-
hood, by our early modes of exertion in the vari-
ous departments of life. All thefe faculties then
conftitute the vis fabricatrix, and the vis conferva-
trix, as well as the vis medicatrix of nature, fo
much fpoken of, but fo little underflood by philo-?
fophers.

8. When we revolve in our minds, firft> the great
changes, which we fee naturally produced in ani-
mals

SECT. XXXIX, 4- GENERATION. 567

mals after their nativity, as in the preclusion of
the butterfly with painted wings from the crawling
caterpillar ; or of the refpiring frog from the fubna-
tant tadpole ; from the feminine body to the bearded
man, and from the infant girl to the la&efcent wo-
man ; both which changes may be prevented by
certain mutilations of the glands neceffary to repro-
duction.

Secondly, when we think over the great changes
introduced into various animals by artificial or ac-
cidental cultivation, as in horfes, which we have
exercifed for the different purpofes of ftrength or
fwiftnefs, in carrying burthens or in running races ;
or in dogs, which have been cultivated for ftrength
and courage, as the bull-dog ; or for acutenefs of
his fenfe or fmell, as the hound and fpaniel ; or
for the fwiftnefs of his foot, as the grey-hound ; or
for his fwimming in the water, or for drawing fnow-
iledges, as the rough-haired dogs of the north ;
or laftly, as a play-dog for children, as the lap-dog ;
with the changes of the forms of the cattle, which
have been domefticated from the greateft antiquity,
as camels, and fheep ; which have undergone fo
total a transformation, that we are now ignorant from
what fpecies of \vild animals they had their ori-
gin. Add to thefe the great changes of lhape and
colour, which we daily fee produced in fmaller ani-
mals from our domeftication of them, as rabbits,
or pigeons ; or from the difference of climates and
even of feafons ; thus the fheep of warm climates
are covered with hair inftead of wool ; and the
hares and partridges of the latitudes, which are long
buried in fnow, become white during the winter
months ; add to thefe the various changes produced
in the forms of mankind, by their early modes of
exertion ; or by the difeafes occalioned by their
habits of life ; both of which became hereditary,
and that through many generations. Thofe who

labour

568 GENERATION. SECT. XXXIX. 4.

labour at the anvil, the oar, or the loom, as well
as thofe who carry fedan-chairs, or who have been
educated to dance upon the rope, are diftinguifh-
able by the fhape of their limbs ; and the difeafes
occafioned by intoxication deform the countenance
with leprous eruptions, or the body with tumid
vifcera, or the joints with knots and diftortions.

Thirdly, when we enumerate the great changes
produced in the fpecies of animals before their na-
tivity ; thefe are fuch as referable the form or co-
lour of their parents, which have been altered by
the cultivation or accidents above related, and are
thus continued to their pofterity. Or they are
changes produced by the mixture of fpecies, as in
mules ; or changes produced probably by the exu-
berance of nourishment fupplied to the fetus, as in
monftrous births with additional limbs; many of
thefe enormities of fhape are propagated, and con-
tinued as a variety at leaft, if not as a new fpecies
of animal. I have feen a breed of cats with an ad-
ditional claw on every foot ; of poultry alfo with
an additional claw, and with wings to their feet ;
and of others without rumps* Mr. Buffon menti-
ons a breed of dogs without tails, which are com-
mon at Rome and at Naples, which he fuppofes to
have been produced by a cuftorn long eftablifhed
of cutting their tails clofe off. There are many
kinds of pigeons, admired for their peculiarities,
which are monflers thus produced and propagated,
And to thefe muft be added, the changes produced
by the imagination of the male parent, as will be
treated of more at large in No. VI. of this Section*

When we confider all thefe changes of animal
form, and innumerable others, which may be col-
lected from the books of natural hiftory ; we can-
not but be convinced, that the fetus or embryon is
formed by apportion of new parts, and not by the

diftention

SECT. XXXIX. 4. GENERATION. 5^

diftention of a primordial neft of germs, included
one within another, like the cups of a conjurer.

Fourthly, when we revolve in our minds the
great fimilarity of ftrudure, which obtains in all
the warm-blooded animals, as well quadrupeds,
birds, and amphibious animals, as in mankind ;
from the moufe and bat to the elephant and whale ;
one is led to conclude, that they have alike been
produced from a fimilar living filament. In fome
this filament in its advance to maturity has acquired
hands and fingers, with a fine fenfe of touch, as in
mankind. In others it has acquired claws or talons,
as in tigers and eagles. In others, toes with an
intervening web or membrane, as in feals and geefe*
In others it has acquired cloven hoofs, as in cows
and fwine ; and whole hoofs in others, as in the
horfe. While in the bird kind, this original living
filament has put forth wings inftead of arms or legs,
and feathers inftead of hair. In fome it has pro-
truded horns on the forehead inftead of teeth in the
forepart of the upper jaw ; in others tufhes inftead
of horns ; and in others beaks inftead of either.
And all this exactly as is daily fcen in the tranf-
mutations of the tadpole, which acquires legs and
lungs, when he wants them ; and lofes his tail,
when it is no longer of fervice to him.

Fifthly, from their firft rudiment, or primordium,
to the termination of their lives, all animals under-
go perpetual transformations ; which are in part
produced by their own exertions in confequence of
their deiires and averfions, of their pleafures and
their pains, or of irritations, or of affociations; and
many of thefe acquired forms or propenfuies are
transmitted to their pofterity. See Sect, XXXI. j.

As air and water are fupplied to animals in fuffi-
cient profufion, the three great objecls of defire,
which have changed the forms of many animals by
tfyeir exertions to gratify them, are thofe of luft,

hunger^

GENERATION. SECT. XXXIZ- 4.

hunger, and fecurity. A great want of one part
of the animal world has confifted in the defire of
the exclufive pofleflion of the females ; and thefe
have acquired weapons to combat each other for
this purpofe, as the very thick, fhield-like, horny
fkin on the fhoulder of the boar is a defence only
againft animals of his own fpecies, who ftrike ob-
liquely upwards, nor are his tufhes for other pur-
pofes, except to defend himfelf, as he is not natu-
rally a carnivorous animal. So the horns of the
Hag are fharp to offend his adverfary,but are branch-
ed for the purpofe of parrying or receiving the
thrufts of horns fimilar to his own, and have there-
fore been formed for the purpofe of combating other
flags for the exclufive pofleffion of the females; who
are obferved, like the ladies in the times of chi-
valry, to attend the car of the victor.

The birds, which do not carry food to their
young, and do not therefore marry, are armed with
fpurs for the purpofe of fighting for4:he exclufive
pofleflion of the females, as cocks and quails. It
is certain that thefe weapons are not provided for
their defence againft other adverfaries, becaufe the
females of thefe fpecies are without this armour.
The final caufe of this conteft amongft the males
feems to be, that the ftrongeft and moft active ani-
mal fhould propagate the fpecies, which fhould
thence become improved.

Another great want confifts in the means of pro-
curing food, which has diverfified the forms of all
fpecies of animals. Thus the nofe of the fwine has
become hard, for the purpofe of turning up the
foil in fcarch of infects and of roots. The trunk
of the elephant is an elongation of the nofe for
the purpofe of pulling down the branches of trees
for his food, and for taking up wateV without bend-
ing his knees. Beafts of prey have acquired ftrong
jaws or talons. Cattle have acquired a rough tongue

and

SECT. XXXIX. 4. GENERATION. 571

and a rough palate to pull off the blades of grafs,
as cows and fheep. Some birds have acquired hard-
er beaks to crack nuts, as the parrot. Others have
acquired beaks adapted to break the harder feeds,
as fparrows. Others for the fofter feeds of flowers,
or the buds of trees, as the finches. Other birds
have acquired long beaks to penetrate the moifter
foils in fearch of infects or roots, as woodcocks •
and others broad ones to filtrate the water of lakes,
and to retain aquatic infects. All which feem to
have been gradually produced during many gene-
rations by the perpetual endeavour of the creatures
to fupply the want of food, and to have been de-
livered to their pofterity with conftant improvement
of them for the purpofes required.

The third great want amongft animals is that of
lecurity, which feems much to have diverfified the
forms of their bodies and the colour of them ; thefe
confift in the means of efcaping other animals more
powerful than themfelves. Hence fome animals
have acquired wings inftead of legs, as the fmaller
birds, for the^purpofe of efcape. Others great length
of fin, or of membrane, as the flying fifh, and the
bat. Others great fwiftnefs of foot, as the hare.
Others have acquired hard, or armed fjiells, as the
tortoife and echinus marinus.

Mr. Ofbeck, a pupil of Linnaeus, mentions the
American frogfifhj Lophius Hiftrio, which inhabits
the large floating iflands of fea weed about the Cape
of Good Hope, and has fulcra refemblin-g leaves,
that the fifhes of prey may miftake it for the fea-
weed, which it inhabits. Voyage to China, p. 1 13.

The contrivances for the purpofes of fecurity ex-
tend even to vegetables, as is feen in the wonderful
and various means of their concealing or defending
their honey from infects, and their feeds from birds.
On the other hand fwiftnefs of wing has been ac-
quired by hawks and fwallows to purfue their prey;

VOL. I. P p and

j<i GENERATION. SECT. XXXIX. 4.

and a probofcis of admirable ftruc~lure has been
acquired by the bee, the moth, and the humming
bird, for the purpofe of plundering the nedlaries of
flowers. All which feern to have been formed by
the original living filament, cxciied into aclion by
the neceflhies of the creattfresf, which poflefs them,
and on whicH their eXiilence depends.

From thus meditating on the great fimilarity of
the flrudure of 'the warm-blocdcd animals, and at
tfte fame time of the 'great changes they undergo
both before and after their nativity ; and by conii-
dering in htMv'rninme a portion of time many of
the changes of animals above described have been
produced;, would it be too bold to imagine, that in
the great, length of time, fincc the earth began to
exift, perhaps miHions of ages before the commence-
ment of the hiflory of -mankind, would it be too
bofd to imagine, that all warm-blooded animals have
arifen from one living filament, which the GREAT
FIRST CAUSE endued with animality, with the pow-
er of acquiring new pahs, attended with new pro-
penfities, directed by irritations, fenfations, voliti-
ons, and affociations ; and thus pofieffing the faculty
of ecJiitinuinf t6 improve by its own inherent acli-
vity, and of deliTc:ri-ng down thofe improvements by-
generation to its pofterity, world without end !

Sixthly, The cold-blooded animals, as the fifh-
tribes, which are furnifhcd with but one ventricle
of the heart, and with gills inftead of lungs, and
with fins inftead of feet or wings, bear a great fimi-
larity to ea(ch other ; but tfiey differ, fteverthelcfs,
fo Hiuch in their general ft r.u 61 u re from the warm-
blooded animals, that it may not feem probable at
firfl view, that the fame living filament could have
given origin to this kingdom of animals, as to the
former. Yet are there fome creatures, which unite
or partake of both thefe orders of animation,. as the
whales and feals ; and more particularly the frog,

' ^mo

SECT. XXXIX. 4. GENERATION. 573

who changes from an aquatic animal furnifhcd with
gills to an aerial one furnilhed with lungs.

The numerous tribes of infedls without wings,
from the fpider to the fcorpion, from the flea to the
lobfter ; or with wings, from the gnat and the ant
to the wafp and the dragon-fly, differ fo totally from
each other, and from the red-blooded clafles above
defcribed, both in the forms of their bodies, and
their modes of life; befides the organ of fenfc,
which they fecm to poiTefs in their antennas or
horns, to which it has been thought by fome natu-
ralifts, that other creatures have nothing fimilar ;
ihat it can fcarccly be fuppofed that this nation of
animals could have been produced by the fame kind
of living filament, as the red-blooded claifes above
mentioned. And yet the changes which many of
them undergo in their early ftate to that of their
maturity, are as different, as one animal can be from
another. As thofe of the gnat, which pafles his
early ftate in water, and then ftretching out his new
wings, and expanding his new lungs, rifes in the
air ; as of the caterpillar, and bee-nymph, which
feed on vegetable leaves or farina, and at length
burfting from their felf-formed graves, become beau-
tiful winged inhabitants of the ikies, journeying
from flower to flower, and nourifhed by the ambro-
fial food of honey.

There is ftill another clafs of animals, which are
termed vcrmes by Linnaeus, which are without feet.,
or brain, and are hermaphrodites, as worms, leeches;
fnailsjfhell-fifti, coralline infecls, and fponges ; which:
poifefs the fimpleft itrudure of all animals, and ap-
pear totally different from thofe already defcribctL
The fimplicity of their ftrudure, however, can af-
ford no argument againft their having been produced
from a living filament as above contended.

Lail of all the various tribes of vegetables arc to

'V enumerated amongft the inferior orders of arii-

P p 2 vnals,

574 (GENERATION. SECT. XXXIX 4.

tnz\s. Of thefe the anthers and fligmas have al-
ready been (hewn to poffefs fome organs of fenfe,
to be nourifhed by honey, and to have the power
of generation like infe&s, and have thence been
announced amongft the animal kingdom in Sed.
XIII. and to thefe muft be added the buds and
bulbs which conilitute the viviparous offspring of
vegetation. The former J fuppofe to be beholden
to a fingle living filament for their feminal or ama-
torial procreation ; and the latter to the fame caufe
for their lateral or branching generation, which
they poffefs in common with the polypus, tsenia>and
volvox ; and the fimplicity of which is an argument
in favour of the iimilarity of its caufe.

Linnaeus fuppofes, in the Introduction to his Na-
tural Orders, that very few vegetables were at tirft
created, and that their numbers were iucreafed by
their intermarriages, and adds, fuadent hsec Crea*
toris leges a fimplicibus ad compofita. Many other
changes feem to have arifen in them by their per-
petual conteft for light and air above ground, and
for food or moifture beneath the foil. As noted in
Botanic Garden, Part II. Note on Cufcuta. Other
changes of vegetables from climate, or other caufes,
are remarked in the Note on Curcuma in the fame
work. From thefe one might be led to imagine,
that each plant at fiift confilted of a fingle bulb,
or flower to each root, as the gentianella and daify j
and that in the conteft for air and light, new buds
grew on the old decaying flower item, fhooting
down their elongated roots to the ground, and that
in procefs of ages tall trees were thus formed, and
an individual bulb became a fwarm of vegetables.
Other plants, which in this conteft for light and air
were too flender to rife by their own ftrength, learn-
ed by degrees to adhere to their neighbours, either
by putting forth roots like the ivy, or by tendrils
like the vine, or by fpiral contortions like the honey-

fuckle;

SECT. XXXIX. 4 GENERATION. 575

fuckle ; or by growing upon them like the mifleto,
and taking nourifhment from their barks ; or by
only lodging or adhering on them, and deriving
nourifhment from the air, as tillandfia.

Shall we then fay the vegetable living filament
was originally different from that of each tribe of
animals above defcribed ? And that the productive
living filament of each of thofe tribes was diffeient
originally from the other? Or, as the earth and
ocean were probably peopled with vegetable pro-
ductions long before me exiftence of animals ; and
many families of thefe animals long before other
families of them, fhall we conje&ure that one and
the fame kind of living filaments is and has been
the caufe of all organic life ?

This idea of the gradual formation and improve-
ment of the animal world accords with the obfer-
vaiions of fome modern philofophers, who have fup-
pofed ihat the continent of America has been raifed
out of the ocean at a later period of time than the
other three quarters of the globe, which they de-
duce from the greater comparative heights of its
mountains, and the confequent greater coldnefs of
its refpeftive climates, and from the lefs fize and
ftrength of its animals, as the tigers and alligators
compared with thofe of Afia or Africa. And laftly,
from the lefs progrefs in the improvements of the
mind of its inhabitants in refpeft to voluntary excr-
cions.

This idea of the gradual formation and improve-
ment of the animal world feems not to have been
unknown to the ancient philofophers. Plato having
probably obferved the reciprocal generation of in-
ferior animals, as fnails and worms, was of opinion,
that mankind with all other animals were originally
hermaphrodites during the infancy of the world>
and were in procefs of time feparated into male and
female. The brealls and teats of all male quadru-

576 G E ¥ EjSL AT JO N. SECT. XXXIX. 4.

peds, to which no ufe can now.be affigned, adds
perhaps forac fhadpw of probability to this opinion.
Linnaeus excepts the horfe from the male quadru-
peds, who have teats ; which might have Qiewn the
earlier origin of his exiftence ; but Mr. J. Hunter
aliens, that he has discovered the veftiges of them
jon his fheatb, and has at the fame time enriched
natural hiflory with a very curious fa& concerning
the male pigeon ; at the time of hatching the eggs
both the male and female pigeon undergo 3 great
change in their crops ; which thicken and become
corrugated, and fecrete a kind of milky fluid, which
coagulates, and with which alone they for a few
days feed t)ieir young, and afterwards feed them
with this coagulated fluid mixed with other foodc
How this refembles the breafts of female quadru-
peds after the production of their young ! and how
extraordinary, that the male fhould at this time give
piilk as 'well as the female I See Botanic Garden,
Part II. Note on Curcuma.

The late Mr. David Hume, in his pofthurnous
works, places the powers of generation much above
thofe of our boafted reafoh ; and adds, that reafon
can only make a machine, as a clock or a fhip, but
the power of generation makes the maker of the
•machine ; and probably from having obfervcd, that
the greateft part of the earth has been formed out
of organic recrements ; as the immenfe beds of lime-
ftone, chalk, marble, from the fhells of fifh ; and
the extenfive provinces of clay, fandfione, ironftone,
coals, from decompofed vegetables ; all which have
-been firft produced by generation, or by the fecre-
tions of organic life ; he concludes that the world
itfelf might have been generated, rather than cre-
ated; that is, it might have been gradually pro-
duced from very fmall beginnings, increaiing by
the aelivity of its' inherent principles, rather than
by a fuddcn evolution of the whole by the Ai-
afrtf mighty

SECT. XXXIX. 5. G E N E R A T 1 O N'. j-;;;

mighty fire. — What a magniiiccnt idea of ihc infinite
power of THE GREAT AR CHITECT ! TntCA USE
OF C A u s LS ! PA R i: N T OF PARENTS! ENS E x T iu M 1

For if we may compare infinities, it would feern
to require .a greater infinity of power to caufe the
caufes of effects, than to caufe the efieds them-
felves. This idea is analogous to the improving ex-
cellence ofoiervable in every part of the creation ;
fuch as in the progrcffive increafe of the folid or
habitable parts of the earth from waier ; and in the
progreflive increafe of the wifdom and happinefs of
its inhabitants ; and is confonant to the idea of our
prefent fituation beingaiiate of probation, which
by ojr exertions we may improve, and arc confe-
quently refponfible for our adtions.

V.i. The efficient caufe of the various colours of the
eggs of birds, and of the hair and feathers of animals,
is a fubjcct fo curious, that I fhall beg to introduce
it in this place. The colours of many animals feem.
adapted to their purpofes of concealing themfelves
cither to avoid danger, or to fpring upon their prey.
Thus the fnake and wild cat, and leopard, are
fo coloured as to referable dark leaves and their
lighter interfaces ; birds refemble the colour of the
brown ground, or the green hedges, which they
frequent ; and moths and butterflies are coloured
like the flowers which they rob of their honey.
Many inflances are mentioned of this kind in Bo-
tanic Garden, p. 2. Note on Rubia.

Thcfe colours have, however, in fome inflances
another ufe, as the black diverging area from the
eyes of the fwan ; which, as his eyes are placed
lefs prominent than thofe of other birds, for the
convenience of putting down his head under water,
prevents the rays of light from being reflected into
his eye, and thus dazzling his fight, both in air and
beneath the water ; which mufl have happened, if

tha

578 GENERATION. SECT. XXXIX. 5,

that furface had been white like the reft of his
feathers.

There is a ftill more wonderful thing concerning
thefe colours adapted to the piirpofe of conceal-
ment ; which is, that the eggs of birds are fo co-
l6ured as to refemble the colour of the adjacent
objects and their interftices. The eggs of hedge-
birds are greenifh with dark fpots ; thofe of crows
and magpies, which are feen from beneath through
wicker nefts> are white with dark fpots; and thofe
of larks and partridges are ruflet or brown, like
tiheir nefts or fituations.

A thing ftill more aftonifhing is, that many ani-
mals in countries covered with fnow become white
in winter, and are faid to change their colour again
in the warmer months, as bears, hares, and par-
tridges. Our domefticated animals lofe their natu-
ral colours, and break into great variety, as horfes,
dogs, pigeons. The final caufe of thefe colours is
eafily underftood, as they ferve fom'e purpofes of
the animal, but the efficient caufe would feem al-
triQft beyond conjecture.

Firft, the choroid coat of the eye, on which the
femitranfparent retina is expanded, is of different
colour in different animals ; in thofe which feed on
grafs it is green ; from hence there wbuld appear
fome connexion between the colour of the choroid
coat and of that conftantly painted on the retina by
the green grafs. Now, wheri the ground becomes
covered with fnow,' it would feem, that that action
of the retina, which is called whitenefs, being con-
ftantly excited in the' eye, maybe gradually imi-
tated by the extremities of the nerves of touch, or
rete m'ucofum of the fkin.; And if it be fuppofed,
that the a&ion of the retina in 'producing the per-
fception of any colour confifts in fo difpofing its
own fibres or furface, as to refl^cl thofe coloured
rays only, and tranfmit the others like foap-bub-

bles;

SECT. XXXIX. $. GENERATION, 579

bles ; then that part of the retina, which gives us
the perception of fnow, muft at that time be white ;
and that which gives us the perception of grafs,
mull be green.

Then if by the laws of imitation, as explained
in Section XIL 33. and XXXIX. 6. the extremities
of the nerves of touch in the rete muKZofum be in-
duced intofimilar action, the fkin or feathers, or
hair, may in like manner fo difpofc their extreme
fibres, as to reflect white ; for it is evident, that all
thefe parts were originally obedient to irritative mo-
tions during their growth, and probably continue
to be fo ; that thofe irritative motions are not liable
in a healthy ftate to be fucceedcd by fenfation ;
which however is no uncommon thing in their dif-
eafed ftate, or in their infant ftate, as in plica po-
lonica, and in very young pen-feathers, which are
ftill full of blood.

It was fhewn in Section XV. on the Production of
Ideas, that the moving organ of fenfe in fome cir-
cumflances refembled the object which produced
that motion. Hence it may be conceived, that the
rete mucofum, which is the extremity of the nerves
of touch, may by imitating the motions of there-
tina become coloured. And thus, like the fable
of the camelion, all animals may poflefs a tendency
to be coloured fomewhat like the colours they moil
frequently infpect ; and finally, that colours may
be thus given to the egg-fhell by the imagination of
the female parent ; which fhell is previoufly a mu-
£ous membrane, indued with irritability, without
which it could not circulate its fluids, and incre^fe
in its bulk. Nor is this more wonderful than that
a fingle idea of imagination fliould in an inftant co-
lour the whole furface of the body of a bright fear-
let, as in the blufh of fhame, though by a very*
different procefs. In this intricate fubject nothing
loofe analogical conjectures can be had, which

roay

S^o G E N $ R A T I O N. SECT. XXXIX. 5

may however lead to future difcoveries; but certain
it is that both the change of the colour of animals
to- white in the winters of fnowy countries, and the
fpots on birds eggs, muft have fome efficient caufe ;
fince the uniformity of their production ftiews it
cannot arife from a fortuitous concurrence of cir-
cumftances ; and how is this efficient caufe to be
detected, or explained, but from its analogy to other
animal fads ?

2. The nutriment fupplied by the female parent
in viviparous animals to their young progeny may
be divided into three kinds, correfponding with the
age of the new creature, i. The nutriment con-
tained in the ovum as previoufly prepared for the
embryon in the ovary. 2. The liquor amnii pre-
pared for the fetus in the uterus, and in which it
fwims ; and laftly, the milk prepared in the peclo-
ral glands for the new born child. There is reafon
to conclude, thaft variety of changes may be pro-
duced in the new animal from all thefe iburces of
nutriment, but particularly from the firft of them.

The organs of digeftion and of fanguification in
adults, and afterwards thofe of fecretion, prepare
or feparate the particles proper for nourifhment
from other combinations of matter, or recombine
them into new kinds of matter, proper to excite in-
to action the filaments, which abforb or attract them
by animal appetency. In this procefs we muft at-
tend not only to the action of the living filament,
which receives a nutritive particle to its bofom, but
alfo to the kind of particle, in refpect to form, or
fize, or colour, or hardnefs, which is thus previ-
oufly prepared for it by. digeftion, fanguificaiion,
and fecretion. Now as the firft filament of entity
cannot be furnifhcd with the preparative organs
above mentioned, the nutritive particles, whiehare
at firft to be received by it, are prepared by the
'mother; and dcpofned in the ovum ready for its

reception

SECT. XXXIX. 5. G E NT E R A T I O N. 581

reception. Thefe nutritive particles mufi be fup-
pofed to differ in fome refpc&s, when thus prepared
by different animals. They may differ in f:ze, co-
lour, and form ; and yet may he fufficiently con-
genial to the living filament, to which they arc ap-
plied, as to excite its activity by their flimulus, and
its animal appetency to receive them, and U) com-
bine them with it fell' into organization.

By this firft nutriment thus prepared for the cm-
5bryon is not meant the liquor amnii, which is af-
terwards produced, nor the larger exterior parts of
the white of the egg ; but the fluid prepared, I
Juppofe, in the ovary of viviparous animals, and
that which immediately furrounds the cicatricula of
an impregnated egg, and is vifible to the eye in a
boiled one.

Now thefe ultimate particles of animal matter pre-
pared by the glands of the mother may be fuppofed
to refemble the fimilar uliimate particles, which
were prepared for her own nourifhment ; tjiat is, to
the ultimate particles of which her own organiza-
tion confifts. And that hence when thefe become
combined with a new embryon, which in its early
flate is not furnifhed with ftomach, or glands, to
alter them ; that ncwr embryon will bear fome rc-
femblance to the mother.

This feems to be the origin of the compound
forms of mules, which evidently panake of both
parents, but principally of the male parent. In
this production of chimeras the anticms fecin lo
have indulged their fancies, whence the fphinxcs,
griffins, dragons, centaurs, and minotaurs, which
are vanifhed from modern credulity.

It would fcem, that in thefe unnatural conjucc-
tions, when the nutriment depofitcd by the female
was fo ill adapted to Simulate the living filament
derived from the male into a6lion, and to be re-
ceived, or embraced by it, and combined wiih it

into

$8* GENERATION. SECT. XXXIX. 5,

into organization, as not to produce the organs ne-
ceflary to life, as the brain, or heart, or ftomach,
that no mule was produced. Where all ihe parts
ncceflary to life in thefe compound animals were
formed fufficiemly perfect, except the parts of ge-
neration, thofe animals were produced which are
now called mules.

The formation of the organs of fexual genera^
lion, in comradiftin6tion to that by lateral buds, in
vegetables, and in forne animals, as the polypus,
the tasnia, and the volvox, feems the chef d'oeuvre,
the matter- piece of nature ; as appears from many
flying infers, as in moths and butterflies, who feem
to undergo a general change of their forms folely
for the purpofe of fexual reproduction, and in all
other animals this organ is not complete till the
maturity of the creature. Whence it happens that,
in the copulation of animals of different fpecies, the
parts neceflary to life are frequently completely-
formed ; but thofe for the purpofe of generation are
defective, as requiring a nicer organization; or more
exa& coincidence of the particles of nutriment to
the irritabilities or appetencies of the original living
filament. Whereas thofe mules, where all the parts
could be perfectly formed, may have been produced
in earlier periods of time, and may have added to
the numbers of our various fpecies of animals, $s
before obferved.

As this production of mules is a conftant effect
from the conjun&ion of two different fpecies of ani-
mals, thofe between the horfe and the female afs always
r^fembling the horfe more than the afs; and thofe,
on the contrary, between the male afs and the mare,
always refembling the afs more than the mare ; it
cannot be afcribed to the imagination, of the male
animal which cannot be fuppoicd to operate fo uni-
formly ; but to the form of the firft nutritive par-
ticles, and to their peculiar flimulus exciting the

living

£*CT. XXXIX. 5. GENERATION. 5*3

living filament to fele<5l and combine them with it-
felf. There is a fimilar qntfonmii of effect in rc-

fped to the colour of the progeny produced be-
tween a white man, and a black woman, which, if
I am well informed, is always of the mulatto kind,
or a mixture of the two ; which may perhaps be
imputed to the peculiar form of the particles of
nutriment fupplied to the embryon by the mother
at the early period of its exiftence, and their pecu-
liar ilimulus; as this effect, like that of the mule
progeny above treated of, is uniform and confident,
and cannot therefore be afcribed to the imagination
of either of the parents.

Dr. Thunberg obferves, in his Journey to the
Cape of Good Hope, that there are fome families,
which have defcended from blacks in the female
kne for three generations. The firft generation pro-
ceeding from an European, who married a tawny
Have, remains tawny, but approaches to a white com-
plexipn y but ihe children of the third generation,
Anixed with Europeans, become quite white, and
are often remarkably beautiful. V. i. p. 112.

When the embryon has produced a placenta, and
furnifhed itfelf wiih veiFels for [election of nutri-
tious particles, and for oxygcnation of them, no
great change in its form or colour is likely to be
produced by the particles of fuftenancc it now takes
from the fluid, in which it is immerfed ; becaufe
it has now acquired organs to alter or new combine
them. Hence it continues to grow, whether this
fluid, in which it fwims, be formed by the uterus
or by any other cavity of the body, as in extra-
uterine. geftation ; and which would feem to be pro-
duced by the ilimulus of the fetus on the fides of
the cavity, where it is found, as mentioned before.
And thirdly, there is ftiJl lefs reafon to expect any
unnatural change to happen to the child after its
birth from the difference of the milk it now takes ;

beeaufe

GENERATION. SECT. XXXIX. 5.

becaufe it has acquired a ftomach, and lungs, and
glands, of fufficient power to decompofe and re-
combine the milk ; and thus to prepare from it the
various kinds of nutritious particles, which the ap-
petencies of the various fibrils or nerves may re-
quire.

From all this reafoning I would conclude, that
though the imagination of the female may be fup«
pofed to affecl: the embryon by producing a differ-
ence in its early nutriment ; yet that no fuch pow-
er can affcft it after it has obtained a placenta, and
other organs ; which may fele6l or change the food,
which is prefemcd to it either in the liquor amnii,
or in the milk. Now as the eggs in pullets, like
the feed> in vegetables, are produced gradually, long
before they are' impregnated, it does not appear how
any fudden effect of imagination of the mother,
at the time of impregnation, can produce any confiv
derable change in the nutriment already thus laid
up for the expected or defired embryon. And that
hence any changes of the embryon, except thofe
uniform ones in the production of mules and mu-
lattoes, more probably depend on the imagination
of the male parent. At the fame time it feems ma-
nifeft, that thofe monftrous births, which confift in
fome deficiencies only, or fome redundancies of
parts, originate from the deficiency or redundance
of the firit nutriment prepared in the ovary, or in
the part of the egg immediately furrounding the
cicatricula, as defcribed above; and which continues
fome time to excite the firft living filament into
action, after the fimple animal is completed ; or
ceafes to excite it, before the complete form is ac-
complifhed. The former of thefe circumftances is
evinced by the eggs with double yolks, which fre-
quently happen to our domefticated poultry, and
which, I believe, are fo formed before impregna-
tion, but which would be well worth attending to,

both

. XXXIX. 6. GENERATION. 585

both before and after impregnation ; as it is proba-
ble, fomething valuable on this fubject might be
learnt from them. The latter circumftancc, or that
of deficiency of original nutriment, may be deduced
from reverfe analogy.

There are, however, other kinds of monftrcus
births, which neither depend on deficiency of parts,
or fupernumerary ones ; nor are owing to the con-
junction of animals of different fpecies ; but which
appear to be new conformations, or new difpofiii-
ons of parts in refpeft to each other, and which, like
the variation of colours and forms of our domefti-
catecl animals, and probably the fexual parts of all
animals, may depend on the imagination of the male
parent, which we now come to confider.

VI. i. The nice actions of the extremities of our-
Carious glands are exhibited in their various pro*
duclions, which are believed to be made by the
gland, and not previoufly to exift as fuch in the
blood. Thus the glands, which conftitute the liver,
make bile ; thole of the ftomach make gaftric acid ;
thofc beneath the jaw, faliva; thofe of the ears,
ear-wax, and the like. Every kind of gland muft
poffefs a peculiar irritability, and probably a
i'enfibiliiy, at the early fiate of its exigence ; and
in eft be furnifhed with a nerve of fenfe, or of mo-
tion, to perceive, and to felecl, and to combine
the particles, which compofe the fluid it fecretes.
And this nerve of fenfc which perceives the differ-
ent articles which compofe the blood, muft at leaft
be conceived to be as fine and fubtle an organ, as
the opiic or auditory nerve, which perceive light or
fo'irid. See Sea. XIV. 9.

But in nothing is this nice action of the extremi-
of the blood-veffels fo wonderful, as in the pro-
duction of contagious matter. A fmall drop of
variolous contagion diffufed in the blood, or per-
haps only by being inferted beneath the cuticle,

after

586 O E N E R A T I O N. SECT. XXXIX. 6.

after a time, (as about a quarter of a lunation,) ex-
cites the extreme veflels of the fkin into certain
motions, which produce a fimilar contagious mate-
rial, rilling with it a thoufand puftules. So that by
irritation, or by ienfation in confequence of irri-
tation, or by affociation of motions, a material is
formed by the extremities of certain cutaneous vef-
fels, exadly fimilar to the ft imulating material, which
caufed the irritation, or eonfequent fenfation, or
affociation.

Many glands of the body have their motions, and
in confequence their fecreted fluids, affe&ed by
pleafurable or painful ideas, fince they are in many
instances influenced by fenfitive affociations, as well
as by the irritations of the particles of the palling
blood. Thus the idea of meat, excited in the minds
of hungry dogs, by their fenfe of vifion, or of
fmell, increafes the difcharge of faliva, both in quan-
tity and vifcidity ; as is feen in its hanging down in
threads from their mouths, as they ftand round a
dinner-table. The fenfations of pleafure, or of pain,
of peculiar kinds, excite in the fame manner a great
difcharge of fears ; which appear alfo to be more
faline at the time of their fecretion, from their in-
flaming the eyes and eye-lids. The palenefs from
fear, and the blufh of fhame, and of joy, are other
inftances of the effects of painful, or pleafurable
fenfations, on the extremities of the arterial fyftem.

It is probable, that the pleafurable fenfation ex-
cited in the ftomach by food, as well as its irrita-
tion, contributes to excite into a6lion the gaftric
glands, and to produce a greater fecretion of their
fluids. The fame probably occurs in the fecretion
of bile ; that is, that the pleafurable fenfation ex-
cited in the ftomach, afTecls this fecretion by fenfi-
tive affociation, as well as by irritative affociation.

And laftly it would feem, that all the glands in
the body have their fecreted fluids affected, in quan-

tity

Siicr.XXXlX. 6. GENERATION. 587

thy and quality, by the pleafurable or painful fen-
fations, which produce or accompany thofe fecre-
tions. And that the pleafurable fenfations arifing
from thefe fecretions may conftitute the unnamed
pleafure of exiftence, which is contrary to what is
meant by taedium vitse, or ennui ; and by which we
fometimes feel ourfelves happy, without being able
to afcribe it to any mental caufe, as after an agree-
able meal, or in the beginningoof intoxication.

Now it would appear, that no fecretion or excre-
tion of fluid is attended with Ib much agreeable
fenfation, as that of the femen ; and it would thence
follow, that the glands, which perform this fecre-
tion, are more likely to be much affected by their
catenations with pleafurable fenfations. This cir-
cumftance is certain, that much more of this fluid
is produced in a given time, when the objedl of its
excluiion is agreeable to the mind.

2. A forcible argument, which fhews the necef-
fity of pleafurable fenfation to copulation, is, that
the a£t cannot be performed without it ; it is eafily
interrupted by the pain of fear or bafhfulnefs ; and
no efforts of volition or of irritation can eflec-l this
procefs, except fuch as induce pleafurable ideas of
fenfations. See Sea. XXXIII. I. i.

A curious analogical circtimflance attending her-
maphrodite infers, as fnails and worms, ftill fur-
ther illuftrates this thueory; if the fnail or worm
could have impregnated itfelf, there might have
been a faving of a large male apparatus ; but as
this is not fo ordered by nature, but each fnail and
worm receives and gives impregnation, it appears,
that a pleafurable excitation feems alfo to have been
required.

'1 his wonderful circumftance of many infecls be-
ing hermaphrodites, and at the fame time not hav-
ing power to impregnate themfelves, is attended to
by Dr. Lifter, in his Exeicitationes Anatom. de

VOL. I. Q^q Liinacibus,

588 GENERATION. SECT. XXXIX. 6.

Limacibus, p. 145; who, amongft many other final
caufes, which he adduces to account for it, adds,
ut tarn triflibus et frigidis animalibus majori cum
voluptate perficiatnr venus.

1 here is, however, another final caufe, to which
this circumftance may be imputed : it was obferved
above, that vegetable buds and bulbs, which are
produced without a mother, are always exaft re-
iemblances of thei* parent ; as appears in grafting
fruit-trees, and in the flower-buds of the dioiceous
plants, which aie always of the fame lex on the
fame tree; hence thofe hermaphrodite infects, if
they could have produced young without a mother,
would not have been capable of that change or im-
provement, which is feen in all other animals, and
in thofe vegetables, which are procreated by the
male embryon received and nourished by the female.
And it is hence probable, if vegetables could
only have been produced by buds and bulbs, and
not by fexual generation, that there would not at
this time have exifted one thoufandth part of their
ptefent number of fpecies ; which have probably
been originally mule-prpJudtions; nor could any
kind of improvement or change have happened to
them, except by the difference of foil or climate.

3. I conclude, that the imagination of the male
at the time of copulation, or at the time of the fe*
cretion of the femen, may fo affeci this fecretion by
irritative or fenfitive affociation, as defcribed in No.
q. i. of this Section, as to caufe the production of
fimilarity of form and of features, with the diftinc-
tion of lex ; as the motions of the chifiel of the
turner imitate or correfpond with thofe of the ideas
of the artift. It is not here to be underftood, that
the firft living fibre, which is to form an animal, is
produced with any fimilarity of form to the future
animal ; but with propenfities, or appetences, which
fnall produce by accretion of parts the fimilarity of

form,

. XXXIX. 6. GENERATION. 589

form, feature, or fex, correfponding to the imagin-
ation of the father.

Our ideas are movements of the nerves of fenfe,
as of the optic nerve in recollecting vifible ideas,
fuppofe of a triangular piece of ivory* The fine
moving fibres of the retina ad in a manner to which
I give the name of white \ and this action is con-
fined to a defined part of it ; to which figure I give
the name of triangle. And it is a preceding plea-
furable ienfatton exifting in my mind, which occa-
lions me to produce this particular motion of the-
retina, when no triangle is preient. Now it is pro-
bable, that the acting fibres of the ultimate termin-
ations of the fecreting apertures of the veffels of tho
teftes, are as fine as thoTe of the retina; and that they are
liable to be thrown into that peculiar action, which
marks the fex of the fecreted embryon, by fympa-
thy with the pleafurable motions of the nerves of
vifion or of touch ; that is, with certain ideas of
imagination. From hence it would appear, that the
world has been long miilaken in afcribing great pow-
er to the imagination of the female, whereas from
this account of it, the real power of imagination,
in the act of generation, belongs folely to the male.
See Sea. XII. 3. 3.

It may be objected to this theory, that a man
may be fuppofed to have in his mind, the idea of
the form and features of the female, rather than his
own, and therefore there ihould be a greater num-
ber of female births. On the contrary, the general
idea of our own form occurs to every one almoft
perpetually, and is termed confcioufnefs of our ex-
iftence, and thus may effect, that the number of
males furpaffes that of females. See Sect. XV. 3. 4*
and XVIII. 13. And what farther confirms this
idea is, that the male children molt frequently re^
femble the father in form, or feature, as well as in
fex ; and the female mod frequently refemble the

mother,

590 GENERATION. SECT. XXXIX. 6.

mother, in feature, and form, as well as iu
fex.

It may again be obje&ed, if a female child fome-
rimes refenvbles the father, and a male child the mo-
ther, the ideas of the father, at the time of procie-
ation, mud fuddenly change from himfelf to the
mother, at the very inflant, when the embryon is
fecreted or formed. This difficulty ceafes when we
coniider, that it is as eafy to form an idea of femi-
nine featuies with male organs of le production, or
of male features with female ones, as the contrary;
as we conceive the idea of a fphinx or mermaid as
eafily and as diftinctly as of a woman. Add to this,
that at the time of procreation the idea of the male
organs, and of the female features, are often both
excited at the fame time, by contact, or by vifion.

I afk, in my turn, is the fex of the embryon pro-
duced by accident ? Certainly whatever is produced
has a caufe; but when this caufe is too minute for
our comprehenilon, the effect is faid in common lan-
guage to happen by chance, as in throw ing a certain
number on dice. Now what caufe can occafionally
produce the male or female cha racier of the embry-
on, but the peculiar actions of thole glands, which
form the embryon ? And what can influence or go-
vern the'fe actions of the gland, but its affociations
or catenations with other ienfitive motions ? Nor is
this more extraordinary, than that the catenations of
irritative motions with the apparent vibrations of
objedls at fea fhould produce ficknefs of the ftomach,
or that a naufeous flory fhould occafion vomiting.

4. An argument, which evinces the effecl of ima-
gination on the firft rudiment of the embryon, may
be deduced from the production of fome peculiar
monfteis. Such, for infbnce, as thofe which have
i wo heads joined to one body, and thofe which have
two bodies joined to one head ; of w:hich frequent
t.xarnples occur amongft our clomefticaUd quadiu-

peds,

JLCT. XXXIX. 6. GENERATION. 591

peds, and poultry. It is abfurd to fuppofe, that
luch forms could exift in primordial germs, as ex-
plained in No. IV. 4. of this Section. Nor is it
poflible, thut fuch deformities could be produced by
the growth of two embryons, or living filaments 5
which fhould afterwards adhere together; as the
head and tail part of different polypi are faid to do
(Blumenbach on Generation, Cadel, London) ; fince
in that cafe one embryon, or living filament, muft
have begun to form one part fir It, and the other
another part fir ft. But fuch monlhous conforma-
tions become lefs difficult to comprehend, when
they are conlldered as an effect of the imagination,
as before explained, on the living filament at the
time of its fecretion ; and that fuch duplicature of
limbs were produced by accretion of new parts, in
confequence of propenlities, or animal appetencies
thus acquired from the female parent.

For inilance, I can conceive, if a turkey-cock
fhould behold a rabbit, or a frog, at the time of pro-
creation,-'that it might happen, that a forcible or
even a pieafurable idea of the form of a quadruped
might fo occupy his imagination, as to caufe a ten-
dency in the nafcent filament to refemble fuch a
form, by the apportion of a duplicature of limbs.
Experiments on the production of mules and mon-
fters would be worthy the attention of a Spallan-
zani, and might throw much light upon this fubjecl,
which at pieient mud be explained by conjectural
analogies.

The wonderful effect of imagination, both in the
male and female paicnt, is fhewn in the production
of a kind of -milk in the crops both of the male and
female pigeons after the birth of their young, as
obferved by Mr. Hunter, and mentioned before. To
this mould be added, that there are fome inftances
ot men having had milk fecreted in their breads,
and who have given fuck to children, as recorded

$9* GENERATION. SECT. XXXIX. 6.

by Mr. BufFon. This efFccl of imagination, of both
the male and female parent, feems to have been at-
tended loin very early times ; Jacob is faid not only
to have placed rods of trees, in part ftripped of their
bark, fo as to appear fpotted, but ajfo to have placed
fpotted lambs before the flocks, at the time of their
copulation. Genefis, chap. xxx. vei fe 40.

5. In refpedl to the imagination of the mother., it
is difficult to comprehend, how this can produce any
al eration in the fetus, except by affie6Ung the nutri-
ment laid up for its nrft reception, as defcribed in No.
V. 2. of this fedlion, or by affe&ing the nourifhment
or oxygenation \' ith which {he fuppliesit afterwards.
Perpetual anxiety may probably affeft the fecretion
of the liquor amnii into the uterus, as it enfeebles
the whole fyftem; andfudden fear is a frequent caufe
of mifcarriage ; for fear, contrary to joy, decreafes
for a time the action of the extremities of the arterial
fyftem ; hence Hidden palenefs fucceeds, and a
fhrinking or contraction of the veffels of the ikin,
and other membranes. By this circumitance, I
imagine, the terminations of the placenul veflels are
detached from their adhefions, or infertions, into
the membrane of the uterus ; and the death of the
child fucceeds, and confequent mifcarnage.

Of this I recoiled! a remarkable inftance, which
could be afcribed'to no other caufe, and which I
fhall therefore relate in few words. A healthy young
woman, about twenty years of age, had been about
five months pregnant, and going down into her
cellar to draw fome beer, was frighted by a fervaut
boy ftarting up from behind the barrel, wheie he
had concealed himfelf with defign to alarm the
maid fervant, tor whom he miflook his miftrefs*
She came with difficulty up flairs, began to flood im-
mediately, and mifcarried in a few hours. She has
fince borne feveral children, nor- ever had any ten-
dency to mifcarry of any of them.

In

. XXXIX. 6. GENERATION. 595

In refpeft to the power of the imagination of the
male over the form, colour, and fex of the progeny,
the following inilances have fallen under my obfer-
vation, and may perhaps be found not very unfre-
quent, if they were more attended to. I am ac-
quainted with a gentleman, who has one child with
dark hair and eyes, though his lady and hnnfelf
have light hair and eyes ; and their other four child-
lenare like their parents. On obferviug this difli-
milarity of or.e child to the others he affured me,
that he believed it was his own imagination, that
produced the difference; and related to me the fol-
lowing itory. He faid, that when his lady lay in of
her third child, he became attached to a daughter of
one of his inferior tenants, and offered her a bribe
for her favours in vain; and afterwards a greater
bribe, and was equally -unfuccefsful; that the form
of this girl dwelt much in his mind for fome weeks,
and ihat the next child, which was the dark-ey'd
young lady above mentioned, was exceedingly like,
in both features and colour, to the young woman
\vho refilled his addreiles.

To this inihince I muft add, that I have known
two families, in which, on account of an intailed
eftate in expectation, a male heir was molt eagerly
defired by the father; and on the contrary, girls
were produced to the feventh in one, and to the
ninth in another ; and then they had each of them
a fon. I conclude, that the great defire of a male
heir by the father produced rather 3 diiagreeable
than an agreeable fenfation ; and that his ideas dwelt
more on the fear of generating a female, than on the
pleafurable fenfationsor ideas of his own male form
or organs at the time of copulation, or of the fecre-
tion of the femen ; and that hence the idea of the
female charader was more prefect to his mind than
that of the rnale one ; till at length in defpair of ge-
nerating

594 GENERATION. SECT. XXXIX. 7.

nerating a male thefe ideas ceafed, and thofe of the
male character prefided at the genial hour.

7. Hence I conclude, that the aft of generation
cannot exift without being accompanied with ideas,
and that a man muft have at that time either a gene-
ral idea of his own male form, or of the form of his
male organs ; or an idea of the female form, or of
her organs; and that this marks the fex, and the pe-
culiar refemblances of the child to either parent.
From whence it would appear, that the phalli, which
were hung round the necks of the Roman ladies, or
worn in their hair, might have efTeti in producing a
greater proportion of male children; and that the
callipsedia, or art of begetting beautiful children, and
of procreating either males or females, may be taught
by affecting the imagination of the male-parent ;
that is, by the fine extremities of the feminal glands
imitating the actions of the organs of fenfe either of
fight or touch. But the manner of accomplifhing
this cannot be unfolded with fufficient delicacy for
the public eye; but may be worth the attention of
thofe, who are ferioufly interefled in the procreation
of a male or female child.

Recapitulation •

VII. I. A certain quantity of nutritive particles
are produced by the female parent before impregna-
tion, which require no further digeltion, fecretion,
or oxygenation. Such are feen in the unimpregnated
eggs of birds, and in the unimpregnated feed-veifels
of vegetables.

2. A living filament is produced by the male,
which being inferted amidfl thefe firft nutritive parti-
cles, is fUmulated into action by them; and in con-
fequence of this action, fome of the nutritive parti-
cles are embraced, and added to the original living

filament ;

S£CT. XXXIX. 7. GENERATION. 595

filament ; in the fame manner as common nutrition
is performed in the adult animal.

3. Then this new organization, or additional part,
becomes ftimulated by the nutritive particles in its
vicinity, and fenfation is now fuperadded to irritati-
on; and other particles are in confequence embra-
ced, and added to the living filament ; as is fcen in
the new granulations of fiefh in ulcers.

By the power of affociation, or by irritation, the
parts already produced continue their motions, and
new ones are added by fenfation, as above mention-
ed ; and laftly by volition, which laft fenforial power
is proved to exift in the fetus in its maturer age,
becaufe it has evidently periods of activity and of
fleeping ; which laft is another word for a tempora-
ry iufpenfion of volition.

The original living filament may be conceived to
poflefs a power of repulfing the particles applied to
certain parts of it, as well as of embracing others,
which flirnulate other parts of it ; as thefe powers
exifl in different parts of the mature animal ; thus
the mouth of every gland embraces the particles or
fluid, which fuits its appetency ; and its excretory
duel: repulfes thofe particles, which are difagrecable
to it.

4. Thus the outline or miniature of the new ani-
mal is produced gradually, but in no great length of
time ; becaufe the original nutritive particles require
no previous preparation by digeftion, fecretion, and
oxygenation : but require fimply the feieclion and
appofition, which is performed by the lining filament.
Mr. Blumenbach fays, that he poflefles a human
fetus of only five weeks old, which is the fize of a
common bee, and has all the features of the face,
every finger, and every toe, complete ; and in which
the organs of generation are diftindily feen. P. 76.
In another fetus, whofe head was not larger than a
pea, the whole of the bafis of the fkull with all its

depreilions,

GENERATION. SIOT. XXXIX. 7.

depreffions, apertures, and procefTes, were marked
in the mo'l fharp and diftindt manner, though with-
out any offification. Ib.

5. In fome cafes by the nutriment originally do-
pofited by the mother the filament acquires parts not
exactly firnilar to thofe of the father, as in the pro-
du&ion of mules and mulattoes. In other cafes, the
deficiency of this original nutriment caufes deficien-
cies of the extreme parts of the fetus, which are laft
formed; as the fingers, toes, lips. In other cafes,
a duplicature of limbs are caufed by the fuper-
abundance of this original nutritive fluid, as in the
double yolks of eggs, and the chickens from them
with four legs and four wings. But the production
of other monfters, as thole with two heads, or with
parts placed in wrong fituations, feems to arife from
the imagination of the father being in lome manner
imitated by the extreme veflels of the feminal
glands ; as the colours of the fpots on eggs, and the
change of the colour of the hair and feathers of ani-
mals by domeftication, may be caufed in the fame
manner by the imagination ot the mother.

6- The living filament is a part of the father, and
has therefore certain propenfnies, or appetencies,
which belong to him ; which may have been gradu-
ally acquired during a million of generations, even
from rhe infancy of the habitable earth ; and which
now poifeiTes fuch properties, as would render, by
the appofition of nutritious particles, the new fetus
exadtiy fimilar to the father ; as occurs in the buds
and bulbs of vegetables, and in the polypus, and
tsenia or tape-worm. But as the fii ft nutriment is
fupplied by the mother, and therefore refembles fuch
nutritive particles, as have been ufed for her own
nutriment or growth, the progeny takes in part of
the likenefs of the mother.

Other fimilarity of the excitability, or of the form
of the male parent, fuch as '.he broad or narrow

(boulders,

SECT. XXXIX. 7. GENERATION. 597

fhoulders, or fuch as conftitute certain hereditary
difeafes, as icrophula, epilepfy, infanity, have their
origin produced in one or perhaps two geneiations;
as in the progeny of thole who drink much vinous
fpirits; and thofe hereditary propeniities ceafe again,
as I have obferved, if one or two ibber generations
fucceed ; otherwife the family becomes extinct.

This living filament from the lather is alib liable
to have its propeniuies, or appetencies, altered :\t
the time of its production by the imagination of the
male parent; the extremities of the feminal glands
imitating the motions of the organs of fenfe ; and
thus the fex of the embryon is produced ; which
may be thus made a male or a female by affeding
the imagination of the father at the time of impreg-
nation. See Sedl. XXXIX. 6. 3. and 7.

7. After the fetus is thus completely formed to-
gether with its umbilical veflels and placenta, it is
now fupplied with a different kind of food, as ap-
pears by the difference of coniiftency of the differ-
ent parts of the white of the egg, and of the liquor
amnii, for it has now acquired organs for digeition
or fecretion, and for oxygenation, though they aie
as yet feeble ; which can in fome degree change, as
well as felcdt, the nutritive particles, which are nou'
prefented to it. But may yet be aifected by the
deficiency of the quantity of nutrition fupplied by
the mother, or by the degree of oxygenation fup-
plied to its placenta by the maternal blood.

The augmentation of the complete fetus by ad-
ditional particles of nutriment is not accomplished
by diftention only, but by apportion to every part
both external and internal ; each of which acquires
by animal appetencies the new addition of the par-
tides which it wants. And hence the enlarged paits
are kept iimilar to their prototypes, and may be
faid to be extended ; but their extenfion muit be
conceived only as a neceffary confequence of the

enlargement

GENERATION. SECT. XXXIX. 7.

enlargement of all their parts by apportion of new
pai tides.

Hence the new apportion of parts is not produced
by capillary attraction, becaufe the whole is ex-
tended ; whereas capillary attraction would rather
tend to bring the fides of flexible tubes together, and
nut to diilend them. Nor is it produced by che-
mical affinities, for then a folution of continuity
would fucceed, as when fugar is diffolved in water ;
but it is produced by an animal procefs, which is
the confequence of irritation, or fenfation ; and
which may be termed animal appetency.

This is further evinced from experiments, which
have been instituted to fhew, that a living mufcle of
an animal body requires greater force to break it,
than a fimilar mufcle of a dead body. Which
evinces, that befides the attraction of coheiion, which
all- matter poifeffes, and befides the chemical attrac-
tions of affinities, which hold many bodies together,
there is an animal aciheiion, which adds vigour to
thefe common laws of the inanimate world.

8. At the nativity of the child it depofits the
placenta or gills, and by expanding its lungs ac-
quires more plentiful oxygenation from the currents
of air, which it murt now continue perpetually to
refpire to the end of its Hie ; as it now quits the
liquid element, in which it was produced, and like
'the tadpole, when it changes into a frog, becomes

an aciial animal.

9. As the habitable parts of the earth have been,
and continue to be, perpetually increafing by the
production of fea-fhells and corallines, and by the
recrements of other animals, and vegetables ; fo from
the beginning of the exiflence of this terraqueous
fjlobe, the animals, which inhabit it, have conftant-
fy improved, and are dill in a flare of progreffive
iajproveinept.

This

SECT. XXXIX. 8. GENERATION. 599

This idea of the gradual generation of all things
feems to have been as familiar to the ancient philo-
fophers as to the modern ones ; and to hav7e given
i ife to the beautiful hieroglyphic figure of the ^TOV
«ov, or fir II great egg, produced by NIGHT, that is,
whofe origin is involved in obfcuritya and animated
by E£O-, that is, by DIVINE LOVE j from whence
proceeded all things which exift.

Conclufton.

VIIL i. CAUSE AND EFFECT may be confidered
as the progreflion,or fucceflive motions, of the parts
of the great fyftem of Nature. The ilate of things
at this moment is the effect of the (late of things,
which exiiled in the preceding moment; and the
caule of the ftate of things, which fhall exiit in the
next moment.

Thefe caufes and effects may be more eafily com-
prehended, if motion be conlidered as a change of
the figure of a group of bodies, as piopofed in Seel:.
XIV. 2. 2. inafmuch as our ideas of vilible or tan-
gible objects are more diflinct, than our abilracled
ideas of their motions. Now the change of the
configuration of the fyrlem of nature at this mo-
ment niu ft be an efFect of the preceding configura-
tion, for a change of configuration cannot exift
without a previous configuration ; ?nd the proxi-
mate caufe of every effect mud immediately precede
that effect. For example, a moving ivory ball could
not proceed onwaids, unlefs it had previously began
to proceed ; or unlefs an impulfe had been previ-
oufly given it ; which previous motion or impulfe
conttitutes a part of the laft lunation of things.

As the effects produced in this moment of time
become caufes in the next, we may confider the pro-
grefilve motions of objects as a chain of caufes

only;

GENERATION. S*CT. XXXIX. 8.

/

only; whofe firft link proceeded frorn the great Crea-
tor, and which ha\e exifted from the beginning of the
cieated univerfe, and are perpetually proceeding.

2. Thefe caufes may be conveniently divided into-
two kinds, efficient and inert caufes, according with
the two kinds of entity fuppofed to exifl in the na-
tural world, which may be termed matter and fpirit,
as propofed in Sect. I. and further treated of in
Sect. XIV. The efficient caufes of motion, or new
configuration, confift either of the principle of gra-
vnatioa, which a6tuares the fun and planets ; or of
the principle of particular gravitation, as in elec-
tricity, magnetifm, heat ; or of the principle of che-
mical affinity, as in combuftion, fermentation, com-
bination ; or of the principle of organic life, as in
the contraction of vegetable and animal fibres. The
inert caufes of motion, or new configuration, con-
fift of the parts of matter^ which are introduced
tvithin the fpheres of activity of the principles above
tlcfcribed. Thus, when an apple falls on the ground,
the principle of gravitation is the efficient caufe,
and the matter of the apple the inert caufe. If a
bar of iron be approximated to a magnet, it may be
termed the inert caufe of the motion, which brings
thcfe two bodies into contact; while the magnetic
principle may be termed the efficient caufe. In the
lame manner the fibres, which conftitute the retina,
may be called the inert caufe of the motions of that
0rg*n in vifion, while the fenforial power may be
termed the efficient caufe.

3. Another moie common diftiibution of the per-*
peural chain of caufes and effedts, which conftitute
the motions, or changing configurations, of the na-
tural world, is into active and paflive. Thus, if a
ball in motion impinges againft another ball at reft,
and communicates its motion to it, the former ball
is faid to act, and the latter to be a6led upon. In
this fenfe of the words a ningnet is faid to attract

iron ;

SECT. XXXIX 8. GENERATION. 601

iron ; and the prick of a fpur to ftimulate a horfe
inio exertion ; fo that in this view of the works of
nature all things may be faid either limply to exift,
or to exift as caufes, or to exift as effects ; that is,
to exift either in an a&ive or paflive itate.

Ihis diftribution of objects, and their motions,
or changes of pofition, has been found fo conveni-
ent for the purpofes of common li:e, that on this
foundation refts the whole conftru&ion or theory of
language. The names of the things thernfelves are
termed by grammarians Nouns, and their modes
of exiftence are termed Verhs The nouns are di-
vided into fubftantives, which denote the principal
things fpoken of; and into adjectives, which denote
forae circumftances, or lefs kinds of things, belong-
ing to the former. The verbs are divided into three
kinds, fuch as denote the exiflence of things fimply,
as, to be ; or their exiftence in an a&Ive ftate, as,
to eat ; or their exiftence in a paflive ftate, as, to be
eaten. Whence it appears, that all languages con-
fift only of nouns and verbs, with their abbreviati*
ons for the greater expedition of communicating our
thoughts ; as explained in the ingenious work of
Mr. HorneTooke, who has unfolded by a fingle flafh
of light the whole theory oF language, which has
fo long lain buried beneath the learned lumber of
the fchools. Diverfions of Purley. Johnfon. Lon-
don.

4. A third divifion of caufes has been into proxi-
mate and remote ; thefe have been much fpoken of
oy the writers on medical fubjecls, but without fuf-
ficient precifion. If to proximate and remote caufes
\ve add proximate and remote effecls, we fhall in-
clude four links of the perpetual chain of caufation ;
which will be more convenient for the difculllon of
many philofophical fubjecls.

Thus if a particle of chyle be applied to the mouth
of a lafteal veffel>it may be termed the remote caufe

of

6os GENERATION. SECT. XXXIX. 8.

of the motions of the fibres, which Oompofe the
mouth of that lacteal veffel ; the fenforial power is
the proximate caufe ; the contraction of the fibres
of the mouth of the veffel is the proximate effect ;
and their embracing the particle of chyle is the re-
mote effect ; and thefe.four links of caufation con-
f lit me abforption.

Thus when we attend to the rifing fan, firft the
yellow rays of light ftimulate the fenforial power
refiding in the extremities of the optic nerve, this
is the remote caufe. 2. The fenforial power is ex-
cited into a (late of activity, this is the proximate
caufe. 3. The fibrous extremities of the optic nerve
arc contracted, this is the proximate effect. 4. A
pleafsrable or painful fenfation is produced in con-
fequencc of the contraction of thefe fibres of the
optic nerve, this is the remote effect ; and thefe four
links of the chain of caufation conflitute the fenfi-
live idea, or what is commonly termed the fenfa-
tion of the rifing fun.

5. Other caufcs have been announced by medi-
cal writers under the names of caufa procatarctica,
and caufa proegumina, and caufa fine qu3. non. All
which are links more or lefs diflant of the chain of
remote caufes.

To thefe mufl be added the final caufe, fo called
by many authors, which means the motive, for the
accomplifhment of which the preceding chain of
caufes was put into acYion. The idea of a final
caufe, therefore, includes that of a rational mind,
which employs means to effect its purpofes ; thus
the deiire of preferving himfelf from the pain of
cold, which he has frequently experienced, induces
the favage to conftrudt his hut ; the fixing flakes
into the ground for walls, branches of trees for raf-
ters, and turf for a cover, are a feries of fucceffive
voluntary exertions ; which are fo many means to
produce a certain effect. This effect of preferving

himfelf

SECT. XXXIX. 8. GENERATION. 603

himfelf from cold, is termed the final caufe ; the
conftru&ion of the hut is the remote effect ; the ac-
tion of the mufcular fibres of the man, is the prox-
imate effect ; the volition., or activity of deiire to
preferve himfelf from cold, is the proximate caufe;
and the pain of cold, which excited that defire, is
the remote caufe.

6. This perpetual chain of caufes and effecls,
whofe firft link is rivetted to the throne of GOD,
divides itfelf into innumerable diverging branches,
which, like the nerves arifing from the brain, per-
meate the molt minute and moft remote extremities
of the fyftem, diffafing motion and fenfation to the
whole. As every caufe is fuperior in power to the
effect, which it has produced, fo our idea of the
power of the Almighty Creator becomes more ele-
vated and fublime, as we trace the operations of na-
ture from caufe to caufe, climbing up the links of
thefe chains of being, till We afcend to the Great
Source of all things,

Hence the modern difcoveries in chemiflry and
in geology, by having traced the caufes of the com-
binations of bodies to remoter origins, as well as
thofe in aftronomy, which dignify the prefent age,
contribute to enlarge and amplify our ideas of the
power of the Great Firft Caufe. And had thofe
ancient philofophers, who contended that the world
was formed from atoms, afcribed their combinations
to certain immutable properties received from the
hand of the Creator, fuch as general gravitation,
chemical affinity, or animal appetency, inftead of
afcribing them to blind chance ; the doctrine of
atoms, as constituting or compoiing the material
world by the variety of their combinations, fo far
from leading the mind to atheifm, would ftrengthen
the demonftration of the exigence of a Deity, as the
firft caufe of all things ; becaufe the analogy re-
fulting from our perpetual experience of caufe and

VOL. I. Rr effed

££NERATICfN. SECT. XXXIX. «.

efle& xvould have thus been exemplified through
univerfal nature.

The heavens declare the glory of GOD, and the fr~
mament foewetk his handy work! One day telleth ano-
ther, and one night certijietk another ; they have neither
ffeechnor language, yet their voice is gone forth into
all lands, and their words into the ends of the world.
Manifold are thy works, O LORD ! in wifdom kaji thou
wade them all. Pfal. xix. civ,

SECX

SLCT. XL. i. OCULAR SPECTRA.

SEC T. XL.

On the OCUIAR SPECTRA of Light and Colours,
by Dr. R. W. Darwin, of Shrevvfbury. Re-
printed by Permiflion, frtfrn the Philofophical
Tranfadions, Vol. LXXVI. p. 3*3.

Speclra of four kinds. I . Activity of the retina in vi-
fwn. 2. Speflrafrom def eft of fenfibility. 3. Spec-
tra from exccfs of fenfibility. 4. Of dire ft ocular
Spedra. 5. Greater Jlimulus excites the retina into
fpafmodic aclion. 6. Of reverfe ocular fpeclra. 7.
Greater flimulus excites the retina into various fuc-
cejjiye fpafmodic aclions. 8. Into fixed fpafmodic
atJion. 9. Into temporary paralyjis. 10. Mifcef-
laneoiis remarks ; i. DirecJ and reverfe fpeclra at
the fame time. Afpeflral halo. Rule to predeter-
mine the colours of fpeflra. 2. Variation of fpeftra
from extraneous light. 3. Variation of fpeflra in
number, figure, and remij/ion. 4. Circulation of
the b/oo i in the eye is vijtble. 5. A new way of mag-
nifying objects. Conclufion.

WHEN any one has long and attentively looked
at a bright object, as at the fetting fun, on cloiing
his eyes, or removing them, an image, which re-
fembles in form the objeft he was attending to,
continues fome time to be vifible ; this appearance-
in the eye we fhall call the ocular fpe&rum of that
objetl.

Thefc ocular fpe6^ra are of four kinds : ift, Such
as are owing to a lefs fenfibility of a defined pare
of the retina ; or fpeflra from defeB of fenfibility.
zd, Such as are owing to a greater fenfibility of a

R r 2 defined

6o6 OCULAR SPECTRA. SECT. XL, i.

defined part of the retina ; or fpefira from excefs of
fallibility. 3d, Such as referable their object in its
colour as well as ioi m ; which may be termed direft
ocular ffe&ra. 4th, Such as are of. a colour con-
trary to that of their object ; which may be termed
rewrfe ocular fpeftra.

The laws of light have been moft fuccefsfully ex-
plained by the great Newton, and the perception of
vifible objects has been ably investigated by the in-
genious Dr. Berkeley and M. Malebranche ; but
thefe minute phenomena ot vifion have yet been
thought reducible to no theory, though man) philo-
fophers have employed a conliderable degree of at-
tention upon them : among thefe are Dr. Jurin, at
the end of Dr. Smith's Optics; M. jEpinus, in the
Mov. Com. Petropol. V. 10, ; M. Beguelin, in the
Berlin Memoires, V. II 1771 , M. D'Arcy, in the
Hiftoire de 1'Acad. des Scienc. 1765 ; M. de la
Hire; and laflly, the celebrated M. de Button, in
the Memoires de 1'Acad des Seien. who has termed
them accidental colours, as if fubje&ed to no eftab-
Jiflied laws, Ac. Par. 1743. M p. 215.

I muft here apprize the reader, that it is very dif-
ficult for different people to give the fame names to
various fhades of colouis ; whence, in the following
pages, fomething muft be allowed, if on repeating
the experiments the colours here mentioned mould
not accurately correfpond with his own names of
them.

I. A&faity of the Retina in Vifion*

FROM the fubfequent experiments it appears, that
the retina is in an a£iive not in a paflive Hate during
the exiftence of thefe ocular fpe&ra; and it is thence
to be concluded, that all viiion is owing to the ac-
tivity of this organ.

i. Place

Ecr.XL. j. OCULAR SPECTRA. 697

1. Place a piece of red filk, about an inch in di-
ameter, as in plate i, at Seel. III. i, on a fheet of
white paper, in a ftrong light ; look fteadily upon
it from about the dilhinceof half a yard f}r a mi.
nute; then doling your eyelids cover them with
your hands, and a green fpeitrum will be feen in
your eyes, refembiing in form the piece of red filk :
after foine time, this fpeclrum will difappear and
fhortly re-appear ^ and this alternately three or four
times, if the experiment is well made, till at length
it vanifhes entirely.

2. Place on a Iheet of white paper a circular piece
of blue filk, about four inches in diameter, in the
funmine ; cover the center of this with a circular
piece of yellow filk, about three inches in diameter j
and the center of the yellow filk with a circle of
pink filk, about two inches in diameter; and the
center of the pink filk with a circle of green filk,
about one inch in diameter ; and the centre of this
with a circle of indigo, about half an inch in dia-
meter ; make a fmall fpeck with ink in the very
centre of the whole, as in plate 3, at Seel. III. 3.
6. ; look iteadily for a minute on this central fpot,
and then doling your eyes, and applying your hand
at about an inch diftance before them, fo as to
prevent too much or too little light from patting
through the eyelids, you will fee the moft beauti-
ful circles of colours that imagination can conceive,
which are molt reieinbled by the colours occationed
by pouring a drop or two of oil on a Hill lake in a
bright day ; but thefe circular irifes of colours are
not only different from the colours of the filks above
mentioned, but are at the fame time perpetually
changing as long as they exift.

3. When any one in the dark preflfes either cor-
ner of his eye with his ringer, and turns his eye
away from his finger, he will fee a circle of colours
like thofe in a peacock's tail: and a fudden flafh of

light

608 OCULAR SPECTRA. SECT. XL. i,

light is excited in the eye by a ftroke on it. (New-
ton's Opt. Q.^16.)

4. When any one turns round rapidly on one
foot, till he becomes dizzy, and falls upon the
ground, the fpe&ra of the ambient objects continue
to prefent themfelves in rotation, or appear to li-
brate, and he feems to behold them for fome time
ftill in motion.

From all thefe experiments it appears, that the
fpe&ra in the eye are not owing to the mechanical
impulfe of light impreffed on the retina, nor to its
chemical combination with that organ, nor to the
abforption and emiflion of light, as is obferved in
many bodies ; for in all thefe cafes the fpectra muft
either remain uniformly, or gradually diminifh; and
neither their alternate prefence and evanefcence as
in the firft experiment, nor the perpetual changes of
their colours as in the fecond, nor the flafh of light
or colours in the prefTed eye as in the third, nor
the rotation or libration of the fpeclra as in the
fourth, could exift.

It is noi abfurd to conceive, that the retina may
be ftimulated into motion, as well as the red and
white mufcles which ferm our limbs and veffels ;
iince it conlifts of fibres, like thofe, intermixed with
its medullary fubftance. To evince this ftru&ure,
the retina of an ox's eye was fufpended in a glafs of
warm water, and forcibly torn in a few places ; the
edges of thefe parts appeared jagged and hairy, and
did not contract, and become fmooth like fimple
mucus, when it is diftended till it breaks ; which
fhews that it confifts of fibres ; and that its fibrous
conduction became Hill more diftindt to the fight,
by adding fome cauftic alkali to the water, as the
adhering mucus was firft eroded, and the hair-like
fibres remained floating in the veflel. Nor docs the
degree of tranfparency of the retina invalidate the
evidence of its fibrous ftrudure, fince Leeuwenhoek

has

SECT. XL. 2. OCULAR SPECTRA. 609

has fhewn that the cryftallinc humour itfelf confifts
of fibres* (Arcana IS at urse, V. i. p. 70.)

Hence it appears, that as the mufcles have larger
fibres intermixed with a larger quantity of nervous
medulla, the organ of vifion has a greater quantity
of nervous medulla intermixed with fmaller fibres ;
and it is probable that the locomotive mufcles, as
well as the vafcular ones, of microfcopic animals
have much greater tenuity than thcfe of the retina.

And bcfides the iimilarlaws, which will be fhewn
in this paper to govern alike the actions of the re-
tina and of the mufcles, there are many other ana-
logies which exift between them. 1 hey are both
originally excited into action by irritations, both
aft nearly in the fame quantity of time, are alike
ftrengthened or fatigued by exertion, are alike pain-
ful if excited into action when they are in an in-
flamed ftate, are alike liable to paralyiis, and to the
torpor of old age.

II, OF SPECTRA FROM DEFECT OF SENSIBILITY.

The retina is not fo eafily excited into aft'wn by lefs irri-
tation after having been lately fttbje&ed to greater.

I. WHEN any one paffes from the bright daylight
into a darkened room, the irifes of his eyes expand
themfehes to their utmoft extent in a few feconds of
time; but it is very long before the optic nerve,,
after having been ftimulated by the greater light of
the day, becomes fenfible of the lefs degree of it in
the room ; and, if the room is not too obfcure, the
irifes will again contract themfelvcs in foiue degree,
as the fenfibility of the retina returns.

2. Place about half an inch fquare of white paper
on a black hat, and looking fteadily on the center
of it for a minute, remove your eyes to a fheet of

white

6co OCULAR SPECTRA. SECT. XL. a,

white paper ; and after a fecond or two a dark fquare
will be feen on the white paper, which will conti-
nue fome time. A iimilar dark fquare will be feen
in the clofed eye., if light be admitted through the
eyelids.

So after looking at any luminous object of a fmall
fize, as at the fun, for a fliort time, fo as not much
to faiigue the eyes, this part of the retina becomes
lefs fen fib le to fmaller quantities of light ; hence,
when the eyes are turned on other lefs luminous
parts of the fky, a dark fpot is feen refembling the
fliape of the fun, or other luminous object which
we laft beheld. This is the fource of one kind of
the dark-coloured mufca vplitantes. If this dark fpot
lies above the cepter of tlfe eye, we turn our eyes
that way, expecting to bring it into the center of
the eye, that we may view it more distinctly ; and
in this cafe the dark fpectrum feems to move up-
wards. If the dark fpectrum is found beneath the
centre of the eye, we purfue it from the fame mo-
tive, and it fee ins to move downwards. This has
given rife to various conjectures of fomething float-
ing in the aqueous humours of the eyes ; but who-
ever, in attending to thefe fpots, keeps his eyes
•unmoved by looking fteadily at the corner of a
cloud, at the fame time that he obferves the dark
fpectra, will be thoroughly convinced, that they
have no motion but what is given to them by the
movement of our eyes in purfuit of them. Si>me-
times the form of the fpectrurn, when it has been
received from a circular luminous body, will be-
come oblong ; and fometimes it will be divided into
two circular fpectra, which is not owing to our
changing the angle made by the two optic axifes,
according to the diftance of the clouds or other
bodies to which the fpectrum is fuppofed to be
contiguous, but to other caufes mentioned in ISo.

Xo
• J

XL.a. OCULAR SPECTRA. /

X. 3. of this fedtion. The apparent fize of U
alfo be variable according to its fuppofed diftance.

As thefe fpe&ra are more eafily obfervable when (
our eyes are a little weakened by fatigue, it has
frequently happened, that people of delicate confti-
tutions have been much alarmed at them, fearing a
beginning decay of their light, and have thence
fallen into the hands of ignorant oculifts ; but I be-
lieve they never are a prelude to any other difeafe
of the eye, and that it is from habit alone, and
our want of attention to them, that we do not fee
them on all objects every hour of our lives. But
as the nerves of very weak people lofe their fen(i-
bility, in the fame manner as their mufcles lofe their
activity, by a fmall time of exertion, it frequently
happens, that fick people in the extreme debility
of fevers are perpetually employed in picking fome-
thing from the bed-clothes, occafioned by their mif-
taking the appearance of thefe mufca wlitantes in
their eyes. Benvenuto Celini, an Italian artilt, a
man of ftrong abilities, relates, that having paifed
the whole night on a diftant mountain with fome
companions and a conjurer, and performed many
ceremonies to raife the devil, on their return in the
morning to Rome, and looking up when the fun
began to rife, they faw numerous devils run on tfee
tops of the houfes, as they pafled along \ fo much
were the fpectra of their weakened eyes magnified
by fear, and made fubfervient to the purpofes of
fraud or fuperftition. (Life of Ben. Celini.)

3. Placeafquare inch of white paper on a large
piece of ftraw-coloured filk; look fleadily fome time
on the white paper, and then move the centre of
your eyes on the filk, and a fpectrum of the form
of the paper will appear on the (ilk, of a deeper
yellow than the other part of it : for the central
part of the retina, having been fome time expofed
to the ftimulus of a greater quantity of white light,

is

6x* OCULAR SPECTRA. SECT. XL. $,

is become lefs fenfible to a fmaller quantity of it,
and therefore fees only the yellow rays in that pars
of the ftraw-coioured lilk.

Facts fimilar to thefe are obfervable in ottar parts
of our fyftem : thus* if one hand be made warm*
arid the other expofed to the cold, and then both
of them intrncffed in fubtepid water, the water is
perceived warm to one hand, and cold to the other ;
and we are not able to hear weak founds for forne
time after we have been expofed to loud ones ;
and we feel a chillinefs on coming into an atmof-
phere of temperate warmth, after having been fome
time confined in a very warm room : and he,,ce the
ftotnaeh, and other organs of digeilion, of thofe who
have been habituated to the greater ftimulus of fpi-
fituous liquor, are not excited into their due action
by the left ftimulus of common food alone ; of
which the immediate conference is indigeftion and
hypochondriacifm-

III. OF SPECTRA FROIvi EXCESS OF SENSIBILITY,

The retina is more eafity. excited into a&'wn by greater
irritation after having been lately fitbjefted to lefs.

f, IF the eyes are clofed, and covered perfectly
With a hat, for a minute or two, in a bright day j
on femoving the' hat, a1 red or crirufon light Js feen
through the eyelids, la this experiment the retina,
after being fome time kept in the dark, becomes fo
fenfible to a fmall quantity of light., as to perceive
ciiiiinctly the greater quantity of red rays than of
others \vhich pafs through the eyelids* A limilar
toioufed light is feen to pafs through the edges of
the fingers, when the open hand is oppofed to the
fiame of a candle,

2. If

SECT. XL. 3. OCULAR SPECTRA. 615

2. If you look for fome minutes ileadily on a
window in the beginning of the evening twilight, or
in a dark day, and then move your eyes a little, fo
that thofe parts of the retina, on which the dark
frame-work of the window was delineated, may now
fall on the glafs part of it, many luminous lines,
reprefenting the frame-work, will appear to lie
acrofs the glafs panes : for thofe parts of the retina,
which were before Icafl ftimulated by the dark
frame-work, are now more fenfible to light than
the other parts of the retina which were expofed to
the more luminous parts of the window.

3. M^ke with ink on white paper a very black
fpot, about half an inch in diameter, with a tail
about an inch in length, fo as to reprefent a tad-
pole, as in plate 2, at Sec~l. III. 8. 3. ; look fteadily
for a minute on this fpot, and, on moving the eye
a little, the figure of the tadpole will be feen on the
white part of the paper, which figure of the tad-
pole will appear whiter or more luminous than the
other parts of the white paper ; for the part of the
retina on which the tadpole was delineated, is now
more fenfible to light than the other parts of it,
which were expofed to the white paper. This ex-
periment is mentioned by Dr. Irwin, but is not by
him afcribed to the true caufe, namely, the greater
fenfibility of that part of the retina which has been
expofed to the black fpot, than of the other parts
which had received the white field of paper, which
is put beyond a doubt by the next experiment.

4. On clofing the eyes afier viewing 'the black
fpot on the white paper, as in the foregoing expe-
riment, a red fpot is fecn of the form of the black
fpot : for that part of the retina, on which the black
fpot was delineated, being now more fenfible to
light than the other parts of it, which were more
expofed to the white paper, is capable of perceiv-
ing the red rays which penetrate the eyelids. If

this.

614 Q GUI, A 11 SPECTRA. StcrP XL. j,

this experiment be made by the light of a tallow
candle, the ipot will be yellow in (lead of red ; fur
tallow candles abound much' with yellow light,
which pafles in greater quantity and force through
the eyelids than blue light ; hence the difficulty of
diflinguifhing blue and green by this kind of candle
light. 1 he colour of the fpeclrtim may poffibly
vary in the daylight, according to the different co-
Iptir of the meridian or the morning or evening
light.

M. Bcguelin, in the Berlin Memoires, V. IL
1771, obie-rves, that, when he held a book, fo that
the fun fhone upon his half-clofed eyelids, the
black letters, \vhich he had long infpedlcd, became
red, which mud have been thus occaiioncd- 1 hole
parts of the retina which had received for fome
time the black letters, were fo much more fenfible
than thofe parts which had been oppofed to the
white paper, that to the former the red light, which
paffed through the eyelids, was perceptible. There
is a finiilar (lory told, 1 think, in M. de Voltaire's
Hiftorical Works, of a Duke of Tufcany, who was
playing at dice with the general of a foreign army,
and, believing he faw bloody fpots upon the dice,
portended dreadful events, and retired in confufion.
The obferver, afier looking for a minute on the
black fpots of a die, and carelefsly clpfing his eyes,
on a bright day, would fee the image of a die with
red fpots upon it, as above explained.

5. On emerging from a dark cavern, where we
liave long continued, the light of a bright day be-
comes intolerable to the eye fora confiderable time,
owing to the excefs of fenfibility exifting in the eye,
af.er having been long expofed to little or no ftimuT
lus. This occafions us immediately to contract the
iris to its fmalleft aperture, which becomes again
gradually dilated, as the retina becomes accuflomed
to the greater ftimulus of the daylight.

The

S*CT. XL. 3. OCULAR SPECTRA. 61$

The twinkling of a bright ftar, or of a diftant
candle in the night, is perhaps owing to the lame
caufe. While we continue to look upon thcfe lu-
minous objects, their central parts gradually appear
paler, owing to the decreafing fenfibili.y of ihe part
of ihe retina expofcd to their light ; whilft, at ihe
fame time, by the unfteadinefs of the eye, the edges
of them are perj etually falling on parts of the re-
tina that were jufl before cxpofed to the darknefs of
the uighr, and therefore tenfold more fenfible to light
than the fart on which the i at* or candle had I cen for
fome time delineated. 1 his pains the eye in a fimilar
manner as when we come fuddcnly from a dark room
into bright day-light, and gives the appearance of
bright fcintillations. Hence the flars twinkle moft
when ihe night is darkeft, and do not twinkle through
telefcopes, as cbferved by Muficherbroeck ; and it
will afterwards be feen why this twinkling is fome-
times of different colours when the object is very
bright, as Mr. Melvill obferved in looking at Sirius.
For the opinions of others on this fubjecl, fee Dr.
Prieftley's valuable Hiftory of Light and Colours,
p. 494.

Many facls obfervable in the animal fyftem are
fimilar to thefe ; as the hot glow occafioned by the
ufual warmth of the air, or our clothes, on coming
out of a cold bath ; the pain of the fingers on ap-
proaching the fire after having handled fnow; and
the inflamed heels from walking in fnow. Hence
thofe v\ho have been expofed to much cold have
died on being brought to a fire, or their limbs have
become fo much inflamed as to mortify. Hence
much food or wine given fuddenly to thofe who have
almoft perifhed by hunger has deftroyed them ; for
all the organs of the famifhed body are now become
fo much more irritable to the ftimulus of food and
wine, which they have long been deprived of, that

inflammation

\

OCULAR SPECTRA. SECT. XL. 4

inflammation is excited, which terminates in gan-
grene or fever.

IV. OF DIRECT OCULAR SPECTRA.

A quantity of Jlimulus fomewhat greater than natural
excites the retina into fpafmodic adion, which ceafes
in> ajewfecondf.

A certain duration and energy of the ilimulus
of light and colours excites the perfe6l a6tion of the
retina in viiion ; for very quick motions are imper-
ceptible to us, as well as very flow ones, as the
whirling of a top, or the fhadow on a fun-dial. So
perfe6t darknefs does not affedl the eye at all ; and
excels of light produces pain, not viiion.

I. When a fire-coal is whirled round in the dark,
& lucid circle remains a confiderable time in die
eye ; and that with fo much vivacity of light, that
it is mi (taken for a continuance of the irritation of
the objeft. In the fame manner, when a fiery me-
t'Cor fhoots acrofe the night, it appears to leave a
Jong lucid train behind it, part of which, and per-
haps fometimes the whole, is owing to the conti-
nuance of the a6lion of the retina after having been
thus vividly excited. This is beautifully illuflrated
by the following experiment : fix a paper fail, three
or four inches in diameter, and made like that of
a fmoke jack, in a tube of pafteboard ; on looking
through the tube at a diftant profpedl, fome dis-
iornted parts of it will be feen through the narrow
intervals between the fails ; but as the fly begins to
fevolve, thefe intervals appear larger ; and when it
revolves quicker, the whole profpeft is feen quite
as diftinft as if nothing intervened, though lefs lu-
minous*

2. Look

SECT. XL. 4. OCULAR SPECTRA. 61;

2. Look through a dark tube, about half a yard
long, at the area of a yellow circle of half an inch
diameter, lying upon a blue area of double that di-
ameter, for half a minute ; and on clofing your eyes
the colours of the fpectrum will appear fimilar to
the two areas, as in fig. 3. ; but if the eye is kept
too long upon them, the colours of the fpectrum
will be the reverfe of thofe upon the paper, that
is, the internal circle will become blue, and the ex-
ternal area yellow ; hence fome attention is required
in making this experiment.

3. Place the bright flame of a fpermaceti candle
before a black object in the night ; look fteadilyat it
for a fhort time, till it is obferved to become fome-
what paler ; and on clofing the eyes, and covering
them carefully, but not fo as to comprefs them, the
image of the blazing candle will continue diftindtly
to be vifible.

4. Look fteadily, for a fhort time, at a window
in a black day, as in Exp. 2. Se&.III. and then clofing
your eyes, and covering them with your hands, an
exaft delineation of the window remains for fome
time vifible in the eye. This experiment requires a
little practice to make it fucceed well ; lince, if the
eyes are fatigued by looking too long on the win-
dow, or the day be too bright, the luminous parts
of the window will appear dark in the fpectrum, and
the dark parts of the frame-work will appear lumin-
ous, as in Exp. 2. Sect. III. And it is even diffi-
cult for many, who firft try this experiment, to
perceive the fpectrum at all ; for any hurry of mind,,
or even too great attention to the fpectrum itfelf,
will difappoint them, till they have had a little ex-
perience in attending to fuch finall fenfations.

The fpectra defcribed in this fedtion, termed direct
ocular fpectra, are produced without much fatigue
of the eye ; the irritation of the luminous object be-
ing foon withdrawn, or its quantity of light being

VOL. I, S s not

6i8 OCULAR SPECTRA. SECT. XL. 5

not fo great as to produce any degree of uneafinef^.
in the organ of vifion ; which diftinguifhes therri
from the next clafs of ocular fpectra, which are the
confcquence of fatigue. Thefe direct fpectra are
beft obferved in fuch c ire urn fiances that no light,
but what comes from the object, can fall upon the
eye ; as in looking through a tube, of half a yard
long, and an inch wide, at a yellow paper on the
fide of a room, the direct fpectrum was eafily pro-
duced on clofing the eye without taking it from the
tube; but if the lateral light is admitted through
the eyelids, or by throwing the fpectvum on white
paper, it becomes a reverfe fpectrum, as will be
explained below.

The other fenfes alfo retain for a time the impref-
fions that have been made upon them, or the ac-
tions they have been excited into. So if a hard
body is prefled upon the palm of the hand, as is
practifed in tricks of legerdemain, it is not eafy to
diftinguifh for a few feconds whether it remains or
is removed ; and taftes continue long to exift vividly
in the mouth, as the fmoke of tobacco, or the tafte
of gentian, after the fapid material is withdrawn.

V. A quantity of Jlimulus fomewhat greater than ikt
lajl mentioned excites the retina into ffafmodic aflion,
which ceafes and recurs alternately.

I. ON looking for a time on the fetting fun, fo
as not greatly to fatigue the fight, a yellow fpectrum
is feen when the eyes are clofed and covered, which
continues for a time, and then difappears and re-
curs repeatedly before it entirely vanifhes. This
yellow fpectrum of the fun when the eyelids are
opened becomes blue ; and if it is made to fall on
the green grafs, or on other coloured objects, it

varies

SECT. XL. 6. OCULAR SPECTRA, 619

varies its own colour by an intermixture of theirs,
as will be explained in another place.

2. Place a lighted fpermaceti candle in the night
about one foot from your eye, and lookfleadily on
the centre of the flame, till your eye becomes much
more fatigued than in Sect. IV. Exp. 3. ; and on
clofing your eyes a rcddifh fpectrum will be per-
ceived, which will ceafe and return alternately.

The action of vomiting in like manner ceafes, and
is renewed by intervals, although the emetic drug
is thrown up with the firft effort : fo after-pains con-
tinue fome time after parturition; and the alternate
pulfations of the heart of a viper are renewed for
fome time after it is cleared from its blood.

VI. OF REVERSE OCULAR SPECTRA.

The retina, after having been excited into aftion by a
Jlimulus fomewhat greater than the lajl mentioned,
falls into oppofite fpafmodic aflion.

THE actions of every part of animal bodies may
be advantageoufly compared with each other. This
ftrict analogy contributes much to the investigation
of truth ; while thofe loofer analogies, which com-
pare the phenomena of animal life with thofe of
chemiftry or mechanics, only ferve to miilead our
inquiries.

When any of our larger mufcles have been in
long or in violent action, and their antagonifts have
been at the fame time extended,as foon as the adlion ot
the former ceafes, the limb is ftretched the contrary
way for our eafe, and a pandiculation or yawning
takes place.

By the following obfervation it appears, that a

iimilar circumftance obtains in the organ of vifion ;

S s 2 after

620 OCULAR SPECTRA. SEcf . AL. 6.

after it has been fatigued by one kind of action, it
fpontaneouily falls into the oppofite kind.

i. Place a piece of coloured filk, about an inch
in diameter, on a fheet of white paper, about half
a yard from your eyes ; look fteadily upon it for a
minute ; then remove your eyes upon another part
of the white paper, and a fpedtrum will be feen of
the form of the filk thus infpe&cd, but of a colour
oppofite to it. A fpectruui nearly fimilar will ap-
pear if the eyes are clohd, and the eyelids fhaded
by approaching the hand near them, fo as to permit
fome, but to prevent too much light falling on
them.

Red filk produced a green fpe&rum.

Green produced a red one.

Orange produced blue.

Blue produced orange.

Yellow produced violet.

Violet produced yellow.

That in thefe experiments the colours of the fpec-
tra are the reverfe of the colours which occafioned
them, may be feen by examining the third figure in
Sir Ifaac Newton's Optics, L. II. p. i, where ihofe
thin laminae of air, which reflected yellow, tranf-'
mined violet ; thofe which reflected red, tranfmitted
a blue green ; and foof the reft, agreeing with the
experiments above related.

2. Thefe reverfe fpe&ra are fimilar to a colour,
formed by a combination of all the primary colours
except that with which the eye has been fatigued in
making the experiment : thus the reverfe fpedruni
of red muft be fuch a green as would be produced
by a combination of all the other prifmatic colours.
To evince this fact the following fatisfactory expe-
riment was made. The prifmatic colours were laid
on a circular pafteboard wheel, about four inches in
diameter, in the proportions defcribed in Dr. Prieft
ley's Hiftory of Light and Colours, pi. iz. fig. 83

excep

SECT. XL. 6. OCULAR SPECTRA. 621

except that the red compartment was entirely left
out, and the others proportionably extended fo as
to complete the circle. Then, as the orange is a
mixture of red and yellow, and as the violet is a
mixture of red and indigo, it became neccflary 10
put yellow on the wheel inftead of orange, and
indigo inftead of violet, that the experiment might
more exactly quadrate with the theory it was de-
figned to eftabliih or confute ; becaufe in gaining a
green fpcctrum from a red object, the eye is fup-
pofed to have become infenfible to red light. This
wheel, by means of an axis, was made to whirl like
a top ; and on its being put in motion, a green co-
lour was produced, correfponding with great exact-
nefs to the reverfe fpedtrum of red.

3. In contemplating any one of thefe reverfe fpec-
tra in the clofed and covered eye, it difappears and
re-appears feveral times fucceflively, till at length it
entirely vanifhes, like the direct fpectra in Sect. V.;
but with this additional circumftance, that when the
fpectrum becomes feint or evanefcent, it is inftantly
Tevivcd by removing the hand from before the eye-
lids, fo as to admit more light : becaufe then not
only the fatigued part of the retina is inclined fpon-
taneoufly to fall into motions of a contrary direc-
tion, but being (till fenfible to all other rays of
light, except that with which it was lately fatigued,
is by thefe rays at the fame time Simulated into
thofe motions which form the reverfe fpeftrum.

From thefe experiments there is rcafon to con-
clude, that the fatigued part of the retina throws
itfelf into a contrary mode of action, like ofcitation
or pandiculation, as foon as the ftimulus which has
fatigued it is withdrawn ; and that it ftill remains
fenfible, that is, liable to be excited into action by
any other colours at the fame time, except the co-
lour with which it has been fatigued,

VII. The

622 OCULAR SPECTRA. Seer. XL.

VII. Tfe r£//>fl tf//*r having been excited into aflion by
• a Jlimulus fomewhat greater than the lajl mentioned
falls into various fuccejfive fpafmodic aflions.

1. ON looking at the meridian fun as long as the
eyes can well bear its brightnefs, the difk firft be-
comes pale, with a luminous crefcent, which feems
to librate from one edge of it to the other, owing
to the unfteadinefs of the eye ; then the whole
phafis of the fun becomes blue, furrounded with a
white halo ; and on doling the eyes, and covering
them with the hands, a yellow fpectrum is feen,
which in a little time changes into a blue one.

M. de la Hire obferved, after looking at the bright
fun, that the impreflion in his eye firft affumed a
yellow appearance, and then green, and then blue ;
and wifhes to afcribe thefe appearances to fome
affection of the nerves. (Porterfield on the eye, Vol.

I* P-343-)

2. After looking fteadily on about an inch fquare

of pink filk, placed on white paper, in a bright
funfhine, at the diftance of a foot from my eyes, and
clofing and covering my eyelids, the fpcdtrum of
the lilk was at firft a dark green, and the fpectrum
of the white paper became of a pink. The fpec-
tra then both difappeared ; and then the internal
fpectrum was blue ; and then, after a fecond difap-
pearance, became . yellow, and laftly pink, whilft
the fpectrum of the field varied into red and green.

Thefe fucceflions of different coloured fpectra
were not exactly the fame in the different experi-
ments, though obferved, as near as could be, with
the fame quantity of light, and other fimilar cir-
cumftanccs ; owing, I fuppofe, to trying too many
experiments at a time ; fo that the eye was not quite
free from the fpectra of the colours which were pre-
vioufly attended to.

The

ECT. XL. 8. OCULAR SPECTRA. 623

The alternate exertions of the retina in the pre-
ceding fection refembled the ofcitation or pandicu-
lation of the mufcles, as they were performed in
directions contrary to each other, and were the con-
fequence of fatigue rather than of pain. And' in
this they differ from the fucceffive diffimilar exerti-
ons of the retina, mentioned in thi^ fection, which
referable in miniature the more violent agitations of
the limbs in con vu Hive difeafes, as epilepfy, chorea
S. Viti, and opifthotonos; all which difeafes are per-
haps, at firfl, the confequence of pain, and have
their periods afterwards eftabliihed by habit.

VIII. The retina, after having been excited into aclion
by ajlimulus fomewhat greater than the laft menti-
onedy falls into a fxed fpafawdic affwn, which con-
tinuesfor fome days.

i. AFTER having looked long at the meridian
fun, in making fome of the preceding experiments,
till the difks faded into a pale blue, 1 frequently ob-
ferved a bright blue fpectrum of the fun on other
objects all the next and the fucceeding day, which
conftamly occurred when I attended to it, and fre-
quently when I did not previoufly attend to it.
When I clofed and covered my eyes, this appeared
of a dull yellow ; and at other times mixed with
the colours of other objects on which it was thrown.
It may be imagined, that this part of the retina was
become infenfible to white light, and thence a blu-
ifh fpectrum became vifible on all luminous objects;
but as a yellowifh fpectrum was alfo feen in the
clofed and covered eye, there can remain no doubt
of this being the fpectrum of the fun. A fimilar
appearance was obferved by M. ^pinus, which he
acknowledges he could give no account of. (Nov.
Com. Petrop. V. 10. p. 2. and 6.)

The

614 OCULAR SPECTRA. Stcj. XL 9, 10.

The locked jaw, and fotne cataleptic fpafms, are
refembled by this phenomenon ; and from hence
we may learn the danger to the eye by infpecling
very luminous objects too long a time.

IX. A quantity of Jlimulus greater tlian the preceding
induces a temporary paralyfis of the organ ofvijion.

1. PLACE a circular piece of bright red filk,
about half an inch in diameter, on the middle of a
fheet of white paper ; lay them on the fioor in a
bright funfhine, and fixing your eyes (teadily on the
center of the red circle, for three or four minutes,
at the diftance of four or fix feet from the object,
the red filk will gradually become paler, and finally
ceafe to appear red at all.

2. Similar to thefe are many other animal facts ;
as purges, opiates, and even poifons, and contagi-
ous matter, ceafe to fUrriulate our fyftem, after we
have been habituated to their ufe. So fome people
fleep undifturbed by a clock, or even by a forge
hammer in their neighbourhood : and not only con-
tinued irritations, but violent exertions of any kind,
are fucceeded by temporary paralyfis. The arm
drops down after violent action, and continues for
a time ufelefs ; and it is probable, that thofe who
have perifhed fuddenly in fwimming, or in fcating
on the ice, have owed their deaths to the paralyfis,
or extreme fatigue, which fucceeds every violent and
continued exertion.

X. MISCELLANEOUS REMARKS.

THERE were fome circumftances occurred in
making thefe experiments, which were liable to alter
the refults of them, and which I fhall here mention

for

SECT. XL. io. OCULAR SPECTRA, ft 5

for the afliftance of others, who may xvifh to repeat
them.

I, Of dire ft and mverfe fpeflra exlflwg at the Jaws
time ; of reciprocal dlrstl fpedra ; of a combination
of direft and inverfe fpeftra ; of a fpeflral halo ;
rules to predetermine the colours of fpeftra.

a. When an area, about fix inches fquare, of
bright pink Indian paper, had been viewed on aa
area, about a foot fquare, of white writing paper,
the internal fpectrum in the clofed eye was green,
being the reverfe fpectrum of the pink paper; and
the external fpeetrum was pink, being the direct
fpectrum of the pink paper. The fame circum-
ftance happened when the internal area was white,
and external one pink ; that is, the internal fpectrum
was pink, and the external one green. All the
fame appearances occurred when the { ink paper
was laid on a black hat.

b. When fix inches fquare of deep violet polifhed
paper was viewed oh a foot fquare of white writing
paper, the internal fpectrum was yellow, being the
reverfe fpectrum of the violet paper, and the exter-
nal one was violet, being the direct fpectrum of the
violet paper.

c. When fix inches fquare of pink paper was
viewed on a foot fquare of blue paper, the internal
fpectrum was blue, and the external fpectrum was
pink ; that is, the internal one was the direct fpec-
trum of the external object, and the external one was
the direct fpedtrum of the internal object, inflead of
their being each the reverfe fpectrum of the objects
they belonged to.

d. When fix inches fquare of blue paper were
viewed on a foot fquare of yellow paper, the inte-
rior fpectrum became a brilliant yellow, and the
exterior one a brilliant blue. The vivacity of the

fpectra

626 OCULAR SPECTRA. SECT. XL. 10.

fpectra was owing to their being excited both by the
ftimuius of the interior and exterior objects ; fo that
the interior yellow fpectrurn was both the reverfe
fpectrum of the blue paper, and the direct one of
the yellow paper ; and the exterior blue fpectrum
was both the reverfe fpectrum of the yellow paper,
and the direct one of the blue paper.

e. When the internal area was only a fquare half-
inch of red paper, laid on a fquare foot of dark
violet paper, the internal fpectrum was green, with
a reddifh-bluc halo. When the red internal paper
was two inches fquare, the internal fpectrum was
a deeper green, and the external one redder. When
the internal paper was fix inches fquare, the fpec-
trum of it became blue, and the fpectrum of the
external paper was red.

f. When a fquare half-inch of blue paper was
laid on a fix-inch fquare of yellow paper, the fpec-
trum of the central paper in the clofed eye was
yellow, incircled with a blue halo. On looking
long on the meridian fun, the difk fades into a pale
blue furrounded with a whitifh halo.

Thefe circumftances, though they very much
perplexed the experiments till they were invefti-
gated, admit of a fatisfa&ory explanation ; for while
the rays from the bright internal object in exp. a.
fall with their full force on the center of the retina,
and, by fatiguing that part of it, induce the reverfe
fpectrum, many fcattered rays, from the fame in-
ternal pink paper, fall on the more external parts
of the retina, but not in fuch quantity as to occa-
lion much fatigue, and hence induce the direct fpec-
trum of the pink colour in thofe parts of the eye.
The fame reverfe and direct fpectra occur from the
violet paper in exp. b. : and in exp. c. the fcattered
rays from the central pink paper produce a direcl fpec-
trum of this colour on the external parts of the eye,
while the fcattered rays from the external blue paper
produce a direct fpectrum of that colour on the cen-

tral

SECT. XL. io. OCULAR SPECTRA. 627

tral part oftheeye,inftead of thefe parts of the retina
falling reciprocally into their reverfe fpectra. In exp.
*/.the colours being the reverfe of each other, the fcat-
tered rays from the exterior object falling on the cen-
tral parts of the eye, and there exciting their direct
fpectrum, at the fame time that the retina was ex-
cited into a reverfe fpectrum by the central object,
and this direct and reverfe fpedrum being of fimi-
lar colour, the fuperior brilliancy of this fpectrum
was produced. In exp. e. the effect of various quan-
tities of ftimulus on the retina, from the different
refpedtive fizes of the internal and external areas,
induced a fpedrum of the internal area in the center
of the eye, combined of the reverfe fpectrum of
that internal area and the direct one of the external
area, in various fhades of colour, from a pale green
to a deep blue, with fimilar changes in the fpec-
trum of the external area. For the fame reafons,
when an internal bright object was frnall, as in exp.
f. inftead of the wrhole of the fpectrum of the ex-
ternal object being reverfe to the colour of the in-
ternal object, only a kind of halo, or radiation of
colour, fimilar to that of the internal object, was
fpread a little way on the external fpectrum. For
this internal blue area being fo fmall, the fcattercd
rays from it extended but a little way on the image
of the external area of yellow paper, and could
therefore produce only a blue halo round the yel-
low fpectrum in the center.

If any one mould fufpedl that the fcattercd rays
from the exterior coloured object do not intermix
with the rays from the interior coloured object, and
thus affect the central part of the eye, let him look
through an opake tube, about two feet in length,
and an inch in diameter, at a coloured wall of a
room with one eye, and with the other eye naked ;
and he will find, that by fhutting out the lateral
light, the area of the wall feen through a tube ap-
pears as if illuminated by the funfhine, compared

with

6a8 OCULAR SPECTRA. SECT. -XL. jo,

with the other parts of it ; from whence arifes the
advantage of looking through a dark tube at diftant
paintings.

Hence we may fafely deduce the following rules
to deter mine before hand the colours of all fpeclra.
j. The direct fpedtnim w'thout any lateral light is
an evanefcent repre fen ration of its ohjett in the un-
fatigued eye. 2. With fome lateral light it becomes
of a colour combined of the dire6t fpetfrnm of the
central objeft, and of the circumjacent objects, in
proportion to their refpe&ive quantity and brillian-
cy. 3. The reverfe fpedrum without lateral light is
a reprefentaticn in the fatigued eye of the form of
its objects, with fuch a colour as would be pro-
duced by all the primary colours, except that of
the object. 4. With lateral light the colour is
compounded 'of the reverfe fpectrurh of the central
object, and the idireft fpe&rurn of the circumjacent
objects, in propoition to their refpective quantity
and brilliancy.

2. Variation and vivacity of the jpe&ra occafioned by
extraneous light.

The reverfe fpectrum, as has been before explain-
ed, is fimilar to a colour, formed by a combina-
tion of all the primary colours, except that with
which the e\e lus been fatigued in making the ex-
periment : fo the reverfe fpectrum of red is fuch a
green as would be produced by a combination of all
fhe other prifmatic colours Now it muft be ob-
ferved, that this reverfe fpe-flrum of red ia there-
fore the direft fpeclrum of a combination of all the
other prifmatic colours, except the red; whence, on
removing the* eye from a piece of red (ilk to a fheet
of white paper, the green fpectrum, which is per-
ceived, may either be called the reverfe fpectrum of

the

SECT. XL. 10. OCULAR SPECTRA. 629

the red filk, or the dired fpeclrum of all the rays
from the white paper, except the red ; for in truth
it is both. Hence we fee the reafon why it is not
eafy to gain a direct fpectrum of any coloured ob-
ject in the day -time, where there is much lateral
light, except of very bright objects, as of the fetting
fun, or by looking through an opake tube ; becaufe
the lateral external light falling alfo on the central
part of ihe retina, contributes to induce the reverfe
fpectrum, which is at the fame time the direct fpec-
trum of that lateral light, deducting only the colour
of the central object which we have been viewing.
And for the fame reafon, it is difficult to gain the
reverfe fpectrum, where there is no lateral light to
Contribute to its formation. Thus, in looking
through an opake tube on a yellow wall, and clofing
my eye, without admitting any lateral light, thefpec-
tra were all at firft yellow ; but at length changed
into blue. And on looking in the fame manner on
red paper, I did at length .get a green fpectrum ; but
they were all <at firft red ones : and the fame after
looking at a candle in the night.

Ihe reveife fpectrum was formed with greater fa-
cility when the eye was thrown from the object on
a iheet of white paper, or when light was admitted
through the clofcd eyelids ; becaufe not only the
fatigued part of the retina was inclined fpomane-
ouily to fall into motions of a contrary direction ;
but being Rill fenfible to all other rays of light ex-
cept that with w:hich it was lately fatigued, was by
thefe rays flimulated at the fa ne time into thofe mo-
tions which form the reverie fpectrum. Hence,
when the reverfe fpecirum of any colour became
faint, it was wonderfully revived by admitting more
light through ihe eyelids, by removing the hand
from before them : and hence, on covering the clofed
eyelids, the fpectrum would often ceafe for a time,
till the retina became fenfible :Q. the flimulus of the

fmaller

630 OCULAR SPECTRA. SECT. XL. 19,

fmaller quantity of light, and then it recurred. Nor
was the fpectrum only changed into vivacity, or in
degree, by this admiffion of light through the eye-
lids ; but it frequently happened, after having view-
ed bright objects, that the fpectrum in the clofed
and covered eye was changed into a third fpectrum,
when light was admitted through the eyelids : which
third fpectrum was compofed of fuch colours as
could pafs through the eyelids3 except thofe of the
object. Thus, when an area of half an inch dia-
meter of pink paper was viewed on a meet of white
paper in the funmine, the fpectrum with clofed and
covered eyes was green ; b\it on removing the hands
from before the clofed eyelids, the fpectrum became
yellow, and returned inftantly again to green, as
often as the hands were applied to cover the eye-
lids, or removed from them : for the retina being
now infenfible to red light, the yellow rays pafling
through the eyelids in greater quantity than the
other colours, induced a yellow fpeclrum ; whereas
if the fpe&rum was thrown on white paper, with
the eyes open, it became only a lighter green.

Though a certain quantity of light facilitates the
formation of the reverfe fpeclrum, a greater quan-
tity prevents its formation, as the more powerful
fthnulus excites even the fatigued parts of the eye
into acYion ; otherwife we (liould fee the fpeclrum
of the laft viewed object as often as we turn our
eyes. Hence the reverfe fpedlra are beft feen by gra-
dually approaching the hand near the clofed eyelids
to a certain diftance only, which mud be varied with
the brightnefs of the day, or the energy of the fpec-
trum. Add to this, that all dark 'fpedha, as black,
blue, or green, if light be admitted through the
eyelids, after they have been fome time covered,
give reddifh fpe&ra, for the reafons given in Seel.
III. Exp. i.

From

SECT. XL, io. OCULAR SPECTRA. 631

From thefe circumftances of the extraneous light
coinciding with the fpontaneous efforts of the fa-
tigued retina to produce a reverfe fpeclrum, as was
obferved before, it is not eafy to gain a direct fpec-
trum, except of objects brighter than the ambient
light; fuch as a candle in the night, the fetting fun,
or viewing a bright object through an opake tube ;
and then the reverfe fpeftrum is inftantaneoufly pro-
duced by the admiflion of fome external light ; and
is as inftantly converted again to the direct fpec-
trum by the exclufion of it. Thus, on looking at
the fetting fun, on clofing the eyes, and covering
them, a yellow fpedlrum is feen, which is the direct
fpectrum of the fetting fun ; but on opening the
eyes on the fky, the yellow fpectrum is immediately
changed into a blue one, which is the reverfe fpec-
trum of the yellow fun, or the direct fpectrum of
the blue fky, or a combination of both. And this
is again transformed into a yellow one on clofing
the eyes, and fo reciprocally, as quick as the mo-
tions of the opening and clofing eyelids. Hence,
when Mr. Melvill obferved the feint illations of the
ftar Sirius to be fometimes coloured, thefe were pro-
bably the direct fpectrum of the blue fky on the
parts of the retina fatigued by the white light of the
ftar. (Eifays Phyfical and Literary, p. 81. V. 2.)

When a direct fpectrum is thrown on colours
darker than itfelf, it mixes with them j as the yel-
low fpectrum of the fetting fun, thrown on the
green grafs, becomes a greener yellow. But when
a direct fpectrum is thrown on colours brighter
than itfelf, it becomes inilantly changed into the re-
verfe fpectrum, which mixes with thofe brighter
colours. So the yellow fpectrum of the fetting fun
thrown on the luminous fky becomes blue, and
changes with the colour or brightnefs of the clouds
on which it appears. But the reverfe fpectrum mixes
with every kind of colour on which it is thrown,

whether

63i OCULAR SPECTRA. SECT. XL. ia.

whether brighter than itfelf or not : thus the reverfe
fpectrum, obtained by viewing a piece of yellow
filk, when thrown on white paper, was a lucid blue
green ; when thrown on black Turkey leather, be-
comes a deep violet. And the fpectrum of blue
iilk, thrown on while paper, was a light yellow ;
on black (ilk was an obfcure orange ; and the blue
fpectrum, obtained from orange-coLured filk, thrown
on yellow, became a green.

In thefe cafes the retina is thrown into activity or
fenfation by the (timulus of external colours, at the
fame time that it continues the activity or fenfation
which forms the fpectra ; in the fame manner as
the prifmatic colours, painted on a whirling top, are
feen to mix together. When tbefe colours of ex-
ternal objects are brighter than the direct fpectrum
which is thrown upon them, they change it into
the reverfe fpectrum, like the admiflion of external
light on a direct fpectrum, as explained above.
When they are darker than the direct fpectrum, they
mix with it, their weaker ftimulus being inefficient
to induce the reverfe fpectrum.

3. Variation of fpeffra In refpeft to number^ and fgurey
and remifllon.

When we look long and attentively at any ob-
je<5t, the eye cannot always be kept entirely motion-
lefs ; hence, on infpecting a circular area of red
filk placed on white paper, a lucid crefcent or edge
is feen to librate on one fide or other of the red
circle : for the exterior parts of the retina fome-
times falling on the edge of the central filk, and
fometimes on the white paper, are lefs fatigued with
red light than the central part of the retina, which
is conftantly expofed to it ; and therefore, when
they fall on the edge of the red filk, they perceive

it

VOL. I.

Tt

SECT. XL. 19. OCULAR SPECTRA. 633

it more vividly. Afterwards, when the eye becomes
fatigued, a green fpectrum in the form of a crefcent
is feen to librate on one fide or other of the central
circle, as by the unfteadinefs of the eye a part of
the fatigued retina falls on the white paper; and as
by the increafing fatigue of the eye the central part
of the iilk appears paler, the edge on which the
unfatigued part of the retina occasionally falls will
appear of a deeper red than the original filk, be-
caufe it is compared with the pale internal part of
it. M. deBuffon in making this experiment obferv-
ed, that the red edge of the filk was not only deeper
coloured than the original filk; but, on his retreat
ing a little from it, it became oblong, and at length
divided into two, which mud have been owing to
his obferving it either before or behind the point of
intersection of the two optic axifes. Thus, if a pen
is held up before a diftant candle, when we look in-
tenfely at the pen, two candles are feen behind it ;
when we look intenfely at the candle, two pens are
feen. If the fight be unfteady at the time of be-
holding the fun, even though one eye only be ufed,
many images of the fun will appear, or luminous
lines, when the eye is clofed. And as fome parts
of thefe will be more vivid than others, and fome
parts of them will be produced nearer the centre of
the eye than others, thefe will difappear fooner than
the others ; and hence the number and fhane of
ihefe fpectra of the fun will continually vary, as
long as they exift. The caufe of fome being more
.vivid than others, is the unfteaciinefs of the eye of
the beholder, fo that fome parts of the retina have
been longer expofed to the funbeams. That fome
parts of a complicated fptctrum fade and return be-
lore other parrs of it, the following experiment
evinces. Diaw three concentric circles ; the exter-
nal one an inch and a half in diameter, the middle
one an inch, and the internal one half an inch j co-
T t 2 lour

634 OCULAR SPECTRA. SECT; XL. 10.

lour the external and internal areas blue, as in Fig.
4. ; after having looked about a minute on the cen-
tre of thefe circles, in a bright light, the fpectrum
of the external area appears firft in the clofed eye,
then ihe middle area, andlaftly the central one; and
then the central one difappears, and the others in
inverted order. If concentric circles of more colours
are added, it produces the beautiful ever changing
fpectrum in Sect. I. Exp. 2.

From hence it would feern, that the centre of the
eye produces quicker remiffions of fpectra, owing
perhaps to its greater fenfibility ; that is, to its more
enei getic exertions. Thefe remiflious of fpectra bear
fome analogy to the tremors of the hands, and pal-
pitations of the heart, of weak people : and perhaps
a criterion of the ftrength of any mufcle or nerve
may be taken from the time it can be continued in
exertion.

4. Variation offpe&ra in refpefl to brilliancy ; the vifi-
bility of the circulation of the blood in the eye.

1. The meridian or evening light makes a differ-
ence in the colours of fome fpectra ; for as the fun
defcends, the red rays, which are lefs refrangible by
the convex atmofphere, abound in great quantity.
Whence the fpectrum of the light parts of a window
at this time, or early in the morning, is red ; and
becorhes blue either a little later or earlier ; and
white in the meridian day ; and is alfo variable from
the colour of the clouds or fky which are oppofed to
the window.

2. All thefe experiments are liable to be con-
founded, if they are made too foon after each other,
as the remaining fpectrum will mix with the new
ones. This is a very troublefome circumftance to
painters, who are obliged to look long upon the fame

colou;

SicT.XL. io. OCULAR SPECTRA. 63$

colour ; and in particular to thofe whofe eyes, from
natural debility, cannot long continue the fame kind
of exertion. For the fame reafon, in making thefe
experiments, the refult becomes much varied if the
eyes, after viewing any object, are removed on other
objects for but an inftant of time, before we clofe
them to view the fpe&rum ; for the light from the
object, of which we had only a transient view, in
the very time of clofing our eyes acts as a flimulus
on the fatigued retina; and for a time prevents the
defircd fpeclrum from appearing, or mixes its own
fpe&rum with it. Whence, after the eyelids are
clofed, either a dark field, or fome unexpected co-
lours, are beheld for a few feconds, before the de-
fired fpectrum becomes diftindlly vifible.

3. The length of time taken up in viewing an
object, of which we are to obferve the fpe&rum,
makes a great difference in the appearance of the
fpeclrum, not only in its vivacity, but in its colour ;
as the direct fpe&rum of the central object, or of
the circumjacent ones, and alfo the reverfe fpectra
of both, with their various combinations, as well as
the time of their duration in the eye, and of their
remimons or alternations, depend upon the degree
of iatigue the retina is fubjected to. The Chevalier
d'Arcy conftructed a machine by which a coal of
fire was whirled round in the dark, and found, that
when a luminous body made a revolution in eight
thirds of time, it prefented to the eye a complete
circle of fire ; from whence he concludes, that the
impreflion continues on the organ about the feventh
part of a fecond. (Mem. de 1'Acad. des Sc. 1765.)
This, however, is only to be conlidered as the fhort-
eft time of the duration of thefe direct fpectra ;
fince in the fatigued eye both the direct and reverfe
fpectra, with their intermirlions, appear to take up
many feconds of time, and feem very variable ia
proportion to the circumftances of fatigue or energy.

4. it

636 OCULAR SPECTRA. SECT. XL. 10.

4. It fometimes happens, if the eyeballs have been
rubbed hard with the fingers, that lucid fparks are
feen in quick motion amidft the fpe&rum we are
attending to. This is fimilar to the flafhes of fire
from a ftroke on the eye in fighting, and is refem-
bled by the warmth and glow, which appears upon
the ikin after friction, and is probably owing to an
acceleration of the arterial blood into the veflels
emptied by the previous preflure. By being accuf-
tomed to obferve fuch fmall fenfations in the eye, it
is eafy to fee the circulation of the blood in this or-
gan. I have attended to this frequently, when I
have obferved my eyes more than commonly fenfi-
ble to other fpedra. The circulation may be feen
either in both eyes at a time, or only in one of
them ; for as a certain quantity of light is neceflkry
to produce this curious phenomenon, if one hand
be brought nearer the clofed eyelids than the other,
the circulation in that eye will for a time difappear.
For the eafier viewing the circulation, it is fome-
times neceflkry to rub the eyes with a certain de-
gree of force after they are clofed, and to hold the
breaih rather longer than is agreeable, which, by
accumulating more blood in the eye, facilitates the
experiment ; but in general it may be feen diftincl-
ly after having examined other fpe&ra with your
back to the light, till the eyes become weary ;
then having covered your clofed eyelids for half a
ininuie, till ihe fpe&rum is faded away which you
were examining, turn your'face to the light, and
removing your hands from the eyelids, by and by
again fhade theih a little, and the circulation be-
comes curioufly <iiiHn&. The dreams of blood are
however generally feen to uniie, which fhews it to
be the venous circulation, owing, I fuppofe, to the
greater opacity of the colour of the blood in thefe
. vcfllis ; for ihis venous circulation is alfo much
mo'.-c eafily feen by the microfcope in the tail of a
tadpole-

SECT. XL. io. OCULAR SPECTRA. 637

5. Variation offpeflra in refpeft to dijlinftnefs andjlze ;
with a new way of magnifying objefts.

i. It was before obferved, that when the two co-
lours viewed together were oppofite to each other,
as ydlow and blue, red and green, &c. according
to the table of reflections and tranfmiflions of light
in Sir Ifaac Newton's Optics, B. II. Fig. 3. the fpec-
tra of thofe colours were of all others the moft bril-
liant, and beft defined ; becaufe they were combined
of the reverfe fpectrum of one colour, and of the
direct fpectrum of the other. Hence, in books print-
ed with fmall types, or in the minute gradation of
thermometers, or of clock-faces, which are to be
feen at a diftance, if the letters or figures are colour-,
ed with orange, and the ground with indigo ; or the
letters with red, and the ground with green ; or any
other lucid colour is ufed for the letters, the fpec-
trum of which is fitnilar to the colour of the ground,
fuch letters will be feen much more diftinctly, and
with lefs confufion, than in black or white: for as
the fpectrum of the letter is the fame colour with
the ground on which they are feen, the unfteadinefs
of the eye in long attending to them will not pro-
duce coloured lines by the edges of the letters,
which is the principal caufe of their confufion.
The beauty of colours lying in vicinity to each
other, whofe fpectra are thus reciprocally fimilar to
each colour, is owing to this greater eafe that the eye
experiences in beholding them diftin&ly ; and it is
probable, in the organ of hearing, a fimilar circum-
ftance may conftitute the pleafure of melody. Sir
Ifaac Newton obferves, that gold and indigo were
agreeable when viewed together ; and thinks there
may be fome analogy between the fenfations of light
and found. (Optics, Qu. 14.)

In

<5 C U L A & S f E C T R A, SECT. XL. 20.

In viewing the fpectra of bright objects, as of a®
area cff red filk of half an inch diameter on white
paper, it is eafy to magnify it to tenfold its fize : for
if, when the fpectrum is formed, you (till keep your
eye fixed on the filk area, and remove it a few inch-
es further from you, a green circle is feen round
the redfilk; for the angle now fub tended by the
iiik Is Ids than it was when the fpedrurn was form-
ed, b«t that of the fpeclrum continues the fame,
and our imagination places them at the fame -dif-
tance Thus when you view a fpectrum on a fheet
<jf white paper, if you approach the paper to the
eye, you may diminifh it to a point ; and if the pa-
per is made to recede from the eye, the £pe$rurn
will appear magnified in proportion to the diftance.

I was furprifede and agreeably amufed, with the
following experiment. I covered a paper about four
inches fquare with yellow, and with a pea filled
with a blue colour wrote upon the middle of it the
word BANKS ki capitals, a* in Fig. 5, and fitting
with my back to the fun, fixed sny eyes for a minute
exactly on the center of the letter N ia the middle
of the word; after clofing ray eyes* and (hading
them fomewbat with my hand, the word was di£
ttndtly feen in the fpedlrura io yellow letters on a
blue field ; and tken, on opening my eyes on a yellow*
ifh wall at tweo.ty feet diftance, the magnified name
of BANKS appeared written on the wall in golde®
characters.

IT was ©bferved by the leaf tied IVL Sauvage (N©-
fol. Method. €1. VIII. OrcL j.) that the pulfations
of the optic artery might be perceived by looking
attetttnrdy on a ^-hite wall w^tl illuminatfid, A kind
of metrWorktfa&jep thao the oilier paris of the wall,

appear*

SECT. XL. io OCULAR SPECTRA. 639

appears and vaniflies alternately with every pupati-
on. This change of the colour of the wall he well
afcribes to the cotnpreffionof the retina by the diailole
of the artery. The various colours produced in the
eye by the preflure of the ringer, or by a ftroke on
it, as mentioned by Sir Ifaac Newton, feem likewife
to originate from the unequal preflure on various
parts of the retina. Now as Sir Ifaac Newton has
fhewn, that all the different colours are reflected or
tranfmitred by the laminse of foap bubbles, or of
air, according to their different thicknefs or thinnefs,
is it not probable, that the effect of the activity of
the retina may be to alter its thicknefs or thinnefs,
fo as better to adapt it to reflect or tranfmit the co-
lours which ftimulate it into action ? May not muf-
cular fibres exift in the retina for this purpofe, which
may be lefs minute than the locomotive mufcles of
microfcopic animals ? May not thefe mufcular acti-
ons of the retina conflitute the fenfation of light
and colours ; and the voluntary repetitions of them,
when the object is withdrawn, conftitute our memo-
ry of them ? And laftly, may not the laws of the
fenfations of light, here inveftigated, be applicable to
all our other fenfes, and much contribute to elucidate
many phenomena of animal bodies both in their
healthy and difeafed ftate ; and thus render this in-
veftigation well worthy the attention of the phyfician,
the nietaphyfician, and the natural philoibpher ?

November i, 1785.

ADDITION.

ADDITION.

Atiit tonal Observations on VERTIGO, which ought to
haw been infer ted in Sefi. XX. 6. after the Words
" cplic nerve," at the End of the fecond Paragraph.

AFTER revolving with your eyes open till you
become vertiginous, as loon as you ceafe to revolve,
not only the circum-ambient objedts appear to circu-
late round you in a direction contrary to that, in
which you have been turning, but you are liable to
roll your eyes forwards and backwards ; as is well
obierved, and ingenioufly ilemonft rated by Dr. Wells
in a late publication on vifion. The fame occurs,
if you revolve with your eyes clofed, and open them
immediately at the time of your ceafmg to turn;
and even during the whole time of revolving, as
may be felt by your hand prefled lightly on your
clofed eyelids. To thefe movements of the eyes, of
which he fuppofes the obferver to be inconfcious,
Dr. Wells afcribes the apparent circumgyration of
objects on ceafiug to revolve.

The caufe of thus turning our eyes forwards, and
then back again, after our body is at reft, depends,
I imagine, on the fame circumilance, which induces
us to follow the indiftinct fpectra, which are formed
on one fide of the center of the retina, when we
obierve them apparently on clouds, as defcribed in
Sect. XL. 2. 2. ; and then not being able to gain a
more diflinct vifion of them, we turn our eyes back,
and again and again purfue the flying fhade.

But

ADDITION. 6.;i

But this rolling of the eyes, after revolving till
we become vertiginous, cannot caufe the apparent
circumgyration of objects, in a direction contrary
to that in which we have been revolving, for the fol-
lowing reafons. I. Becaufe in purfuing a fpectrum
in the iky, or on the ground, as above mentioned,
we perceive no retrograde motions of objects. 2.
Becaufe the apparent retrograde motions of objects,
when we have revolved till we are vertiginous, conti-
nues much longer than the rolling of the eyes above
defcribed.

3. When we have revolved from right to left, the
apparent motion of objects, when we flop, is from
left to right ; and when we have revolved from left
to right, the apparent circulation of objects is from
right to left ; yet in both thefe cafes the eyes of the
revolver are feen equally to roll forwards and back-
wards.

4. Becaufe this rolling of the eyes backwards and
forwards takes place during our revolving, as may
be perceived by the hand lightly prefled on the
clofed eyelids, and therefore exifts before the effect
afcribed to it.

And fifthly, I EOW come to relate an experiment,
in which the rolling of the eyes does not take place
at all after revolving, and yet the vertigo is morg
diftrefling than in the fituations above mentioned*
If any one looks fteadily at a fpot in the ceiling over
his head, or indeed at his own finger held up high
over his head, and in that fituation turns round till
he becomes giddy ; and then (lops, and looks hori-
zontally ; he now finds, that the apparent rota i ion
of objects is from above downwards, or from below
upwards; that is, that the apparent circulation of
objects is now vertical inftead of hotizontal, making
part of a circle round the axis of his eye ; and this
without any rolling of his eyeballs. The reafon of
there being no rolling of the eyeballs peiceived after

this

ADDITION,

this experiment, is, becaufe the images of objects
are fanned in rotation round the axis of the eye,
and not from one fide to the other of the axis of
k y fo that, as the eyeball has not power to turn in
its focket round its own axis, k cannot follow the
apparent motions of thefe evarrefceru fpectra, either
before or alter the body is at reft. From all which
arguments it is manifefty that thefe apparent retro-
grade gyrations of objects are not caufed by the roll-
ing of the eye-balls ; ftrft, becaufe no apparent re-
trogreilion of objects is obferved in other rollings
of the eyes : fecondly, becaufe the apparent retro-
greffion of objects continues many feconds after the
Foil ing of the eyeballs ceafes. Thirdly, becaufe the
apparent retrogreilion of objects i& fometimes one
wayr and fomctimes another, yet the rolling of the
eyeballs is the lame. Fourthly, becaufe the rolling
of the eyeballs exitts before the apparent retrograde
motion of objects is obferved ; that is, before the
revolving peifon flops. And fifthly, becaufe the ap-
parent retrograde gyration of objects is produced,
when there is no rolling of the eyeballs at all.

Doctor Wells imagines, that no fpectra can be
gained in the eye, it a per on levolves with his eye-
lids do fed, and thinks this a fufficient argument
sgainft the opinion, that the apparent progrcffion
of the fj.c&ra of light or colours in the eye can
caufe the apparent retrogreflion of objects in
i he vertigo above defcribccl ; but it is certain,
when any perfon revolves in a light room with
his eyes clofed, that he nevertheleis perceives dif-
erenees of light both in quantity and colour
through his eyelids, as he turns round; and readily
gains Ipeclra of thofe differences. And thefe fpec-
tra are not very d'Hercnt except in Vivacity from
thofe, which he acquire*, when he. revolves wilh
uBelofed eyes, fince if he ihcn revolves very rapidly

the

ADDITION. 643

the colours and forms of furrounding objects are
as it were mixed together in his eye ; as when the
prifmatic colours are painted on a wheel, they ap-
pear white as they revolve. The truth of this is
evinced by the ftaggering or vertigo of men per-
fectly blind, when they turn round ; which is not
attended with apparent circulation of objects, but
is a vertiginous diforder of the fenfe of touch.
Blind men balance themfelves by their fenfe of
touch ; which, being lefs adapted for perceiving
fmall deviations from their perpendicular, occafions
them to carry themfelves more erect in walking.
This method of balancing themfelves by the direc-
tion of their preffure againft the floor, becomes dif-
ordered by the unufual mode of action in turning
round, and they begin to lofe their perpendicula-
rity, that is, they become vertiginous ; but without
any apparent circular motions of viiible objects.

It will appear from the following experiments,
that the apparent progreflion of the ocular fpectra
of light or colours is the caufe of the apparent re-
trogreflion of objects, after a perfon has revolved,
till he is vertiginous.

Firft, when a perfon turns round in a light room
with his eyes open, but clofes them before he (lops,
he will feem to be carried forwards in the direction
he was turning for a fhort time after he flops. But
if he opens his eyes again, the objects before him
inflantly appear to move in a retrograde direction,
and he lofes the fenfation of being carried forwards.
The fame occurs if a perfon revolves in a light room
with his eyes clofed ; when he flops, he feerns to
be for a time carried forward, if his eyes are ftill
clofed ; but the inftant he opens them, the furround-
ing objects appear to move in retrograde gyration.
From hence it may be concluded, that it is the
fenfation or imagination of our continuing to go
forwards in the direction in which we were turning,

that

ADDITION.

caufes the apparent retrograde circulation of
objects.

Secondly, though there is an audible vertigo, as
is known by the battement, or undulations of found
in the ears, which many vertiginous people expe-
rience ; and though there is alfo a tangible vertigo,
as when a blind perfon turns round, as mentioned
above ; yet as this circumgyration of objects is an
Hallucination or deception of the fenfe of frght, we
are to look for the caufe of our appearing to move
forward, when we ftop with our eyes elofed after gy-
ration, to fome affeftion of this fenfe. Now, thirdly,
if the fpeftra formed in the eye during our rota-
tion, continue to change, when we ftand ftill, like
the fpeftra- defcribed in Seft. III. 3. 6. fuch changes
muft fuggeft to us the idea or fenfation of our ftill
continuing to turn round ; as is the cafe, when we
revolve in a light room, and clofe our eyes before
we ftop. And laftly, on opening our eyes in the
iituation above defcribedj the objects we chance to
view amid thefe changing fpectra in the eye, muft
fee m to move in a contrary direction ; as the moon
fometimes appears to move retrograde, when fwift-
gliding clouds are paifing forwards fo much nearer
tfce eye of the beholder,

To make obfervations on faint ocular fpectra re-
quires fome degree of habit, and compofure of
mind, and even patience ; fome of thofe defcribed
in Sect. XL. were found difficult to fee, by many,
who tried them ; now it happens, that the mind,
during the confulion of vertigo, when all the other
irritative tribes of motion, as well as thofe of vi-
fion, are in fome degree difturbed, together with
the fear of falling, is in a very unfit ftate for the
contemplation of fnch weak fenfations, as are oc-
cafioned by faint ocu lar fpectra. Yet afier frequent-
ly revolving, boih with my eyes elofed, and with
operi, and auendin-g to the fpectra remaining

in

ADDITION. 645

In them, by fhading the light from my eyelids more
or lefs with my hand, I at length ceafed to have the
idea of going forward, after I flopped with my eyes
clofed ; and faw changing fpectra in my eyes,
which feemed to move, as it were, over the field of
vifion ; till at length, by repeated trials on funny
days, I perfuaded myfelf, on opening my eyes, after
revolving fome time, on a fhelf of gilded books in
my library, that I could perceive the fpectra Jn my
eyes move forwards over one or two of the books,
like the vapours in the air of a fummer's day ; and
could fo far undeceive myfelf, as to perceive the
books to ftand ftill. After more trials I fometimes
brought myfelf to believe, that I faw changing fpec-
tra of lights and fhades moving in my eyes, after
turning round for fome time, but did not imagine
either the fpectra or the objects to be in a ftate of
gyration. I fpcak, however, with diffidence of thefe
facts, as I could not always make the experiments
fucceed, when there was not a ftrong light in my
room, or when my eyes were not in the moft pro-
per ftate for fiich obfervations.

The ingenious and learned M. Sauvage has men-
tioned other theories to account for the apparent cir-
cumgyration of objects in vertiginous people. As
the retrograde motions of the particles of blood in
the optic arteries, by fpafm, or by fear, as is feen
in the tails of tadpoles, and membranes between the
fingers of frogs. Another caufe he thinks may be
from the librations to one fide, and to the other, of
the cryftalline lens in the eye, by means of involun-
tary actions -of the mufcles, which conjlitute the
ciliary procefs, Both thefe theories lie under the
fame objection as that of Dr. Wells before men-
tioned ; namely, that the apparent motions of ob-
jects, after the obferver has revolved for fome time,
ihould appear to vibrate this way jind that ; and not
VOL, I. \J u to

646 ADDITION.

to circulate uniformly in a direction contrary t6
that, in which the obferver had revolved.

M. Sauvage has, laftly, mentioned the theory of
colours left in the eye, which he has termed im-
preflions on the retina. He fays, " Experience
teaches us, that impreffions made on the retina by
a viiible object remain ibme feconds after the object
is removed ; as appears from the circle of fire which
we fee, when a fire-ftick is whirled round in the
dark; therefore when we are carried round our own
axis in a circle, we undergo a temp@rary vertigo,-
when we ftop ; becaufe the impreffions of the cir-
cumjacent objects remain for a time afterwards on
the retina." Nofolog. Method. Claf. VIII. I. i. We
have before obferved, that the changes of thefc
colours remaining in the eye, evinces them to be
motions of the fine terminations of the retina, and
not impreffions on it ; as impreffions on a paflive
fubftance muft either remain, or ceafe intirely. See
an additional note at the end of the fecond volume,

Dura, Liber ! aftra petis volitans trepidantibtrs alls,
Irruis imniemori, parvula gutta, mari.

Me quoque, rne currente fota revolubilis setas
Volverit in tenebras,— i, Liber, ipfe fequor.

INDEX

INDEX

TO THE

SECTIONS OF PART FIRST.

A.

ABORTION from fear, xxxix. 6. 5.
Abforption of folids, xxxiii, 3. i. xxxvii.

of fluids in anafarca, xxxv. i. 3.
Abforbent vefTels, xxii. 2. xxix. i.

regurgitate their fluids, xxix. I.
their valves, xxix. 2.

communicate with vena portarum, xxvii. 2.
Accumulation of fenforial power, iv. 2. xii. 5. 2.
Adivity of fyftem too great, cure of, xii. 6.

too final!, cure of, xx. 7.
Age, old, xii. 3. i. xxxvii. 4.
Ague-fit, xii. 7. i. xxxii. 3. 4. xxxii. 9.
how cured by bark, xii. 3. 4.

periods, how occafioned, xii. 2. 3. xxxii. 3. 4. xvii. 3. 6,
Ague cakes, xxxii. 7. xxxii. 9.
Air, fenfe of frefh, xiv. 8.
injures ulcers, xxviii. 2.
injecled into veins, xxxii. 5.
Alcohol deleterious, xxx. 3.
Alliterations, why agreeable, xxii. 2.
Aloes inleflened dofes, xii. 3. i.
American natives indolent, xxxi. 2.

narrow mouldered, xxxi. x.

Analogy

INDEX.

Analogy intuitive, xvii. 3. 7.
Animals lefs liable tomadnefs, xxxiii. i.
lefs liable to contagion, xxxiii. i.
how to teach, xxii. 3. 2.
their fimilarity to each other, xxxix. 4. 8.
their changes after nativity, xxxix. 4. 8.
their changes before nativity, xxxix. 4. 8.
lefs liable to contagious difeafes, why, xxxiii. 1 . 5«
lefs liable to delirium and infanity, why, xxxiii. I. £•
eafier to preferve than to reproduce, xxxvii.
food, diftafteof, xxxviii. i.
appetency, xxxix. 4. 7.
Antipathy, x. 2. 2.
Appetites, xi. 2. 2.xiv. 8.
Aphthse, xxviii.
Apoplexy, xxxiv. 1.7.

not from deficient irritation, xxxii. 2. I.
Architecture, xii. 3. 3. xvi. 10.
Arts, fine, xxii. 2.
Afparagus, its fmell in urine, xxix.
Aftociation defined, ii. n.iv. 7. v. 2.
afFociate motions, x.
ftronger than irritative ones, xxiv. 2. 8.
formed before nativity, xi. 3.
with irritative ones, xxiv. 8.
with retrograde ones, xxv. 7. XXT. 10. xxv. 15-
difeafes from, xxxv.
Aflhma, xviii. 15.
Attention, language of, xvi. 8. 6.
Atrophy, xxviii.
Averfion, origin of, xi. 2. 3.

B.

Balance ourfelves by vifion, xx. J.
Bandage increafes abforption, xxxiii. 3. 2.
Barrennefs, xxxvi. 2. 3.
Battement of founds, xx. 7.
Bath, cold. See Cold Bath.
Beauty, fenfe of, xvi. 6. xxii. 2.
Bile-duels, xxx.

ftones, xxx. 3.

regurgitates into the blood, xxiv. 2, 7.

vomiting of, xxx. 3.
Birds of paflage, xvi. 12.
neftsof, xvi. 13.

colour of their eggs, xxxix. 5.

Biting

INDEX.

Biting in pain, xxxiv. 1.3.

of mad animals, xxxiv. I. 3.
Black fpots on dice appear red, xl. 3.
Bladder, communication of with the inteftines, Xxix. 3.

of fifh, xxiv. i, 4.
Blood, transfufion of in nervous fevers, xxxii. 4.

deficiency of, xxxii. 2. and 4.

from the vena portarum into the inteftines, xxvii.

its" momentum, xxxii. 5. 2.

momentum increafed by venefeftion, xxxii. 5. 4.

drawn in nervous pains, xxxii. 5. 4.

its oxygenation, xxxviii.
Breathing, how learnt, xv. 4.
Breafts of men, xiv. 8.
Brutes differ from men, xi. 2. 3. xvi. 1 7.
Brutes. See Animals.
Buxton bath, why it feels warm, xii. 2. I. xxxii. 3. 3-

Capillary veflels are glands, xxvi. I .

Catalepfy, xxxiv. 1.5.

Catarrh from cold fkin, xxxv. I. 3. xxxv. 2. 3.

from thin caps in fleep, xviii. 15.
Catenation of motions defined, ii. n. iv. 7.

caufe of them, xvii. I. 3-

defcribed, xvii.

continue fome time after their production, xvii I. 3.

voluntary ones difTevered in fleep, xvii. i. 12. xrii. 3,

*3-

Cathartics, external, their operation, xxix. 7. 6.
Caufation, animal, defined, it. n.iv. 7.
Caufe of caufes, xxxix. 4. 8.
Caufes inert and efficient, xxxix. 8. 2.
active andpaflive, xxxix. 8. 3.
proximate and remote, xxxix. 8. 4.
Chick in the egg, oxygenation of, xxxviii. 2.
Child riding on a flick, xxxiv. 2. 6.
Child riding on a ftick, xxxiv. 2. 6.
Chilnefs after meals, xxi. 3. xxxv. i. i.
Cholera, cafe of, xxv. 13.
Circulation in the eye vifible, xl. i o. 4.
Cold in the head, xii. 7. 5.

perceived by the teeth, xxxii. 3. I. xiv. 6.

air, ufes of in fevers, xxxii. 3. 3.

feet, produces coryza, xxxv. 2. 3. xxxv. I. 3.

bath, why it flrengthens, xxxii. 3. 2.

fliort

INDEX, j

fTiortand cold breathing in it, xxxii. 3. 2.
produces a fever-fit, xxxii. 3. 2.
fit of fever the confequence of hot fit, xxxii. 9. 3,
bathing in pulmonary haemorrhage, xxvii. I.
fits of fever, xxxii. 4. xxxii. 9. xvii. 3.3.
Comparing ideas, xv. 3.
Confcioufnefs, xv. 3. 4.
Confcioufnefs in dreams, xviii. 13.
Confumption, its temperament, xxxi. i. and 2.
of dark-eyed patients, xxvii. 2.
of light-eyed patients, xxviii. 2.
is contagious, xxxiii. 2. 7.
Confent of parts. See Sympathy.

Contagion, xii. 3. 6. xix. 9. xxxiii. 2. 6. and 8. xxii. 3. 3.
does not enter the blood, xxxiii. 2. 10. xxii. 3. 3.
Contraction and attraction, iv. i.

of fibres produces fenfation, iv. 5. xii. I. 6.
continues fome time, xii. 1.5.
alternates with relaxation, xii. 1.3.
Conrulfion, xvii. i. 8. xxxiv. i. i. and 4. iii. 5. 8.
of particular mufcles, xvii. i. 8.
periods of, xxxvi. 3. 9.
Colours of animals, efficient caufe of, xxxix. 5. i.

of eggs from female imagination, xxxix. 5. i.
of the choroid coat of the eye, xxxix. 5.1.
of birds nefts, xvi. 1 3.
Coryza. See Catarrh.
Cough, nervous, periods of, xxxvi. 3.9.
Cramp, xviii. 15. xxiv. i. 7.
Critical days from lunations, xxxvi. 4.

D.

Darkiftiroom, why we fee well in it, xii. 2. I.
Debility fenforial and (limu)atory, xii. 2. i.

direct and indirect of Dr. Brown, xii. 2. i. xxxii. 3. 2,

See Weaknefs.

from drinking fpirits, cure of, xii. 7. 8.

in fevers, cure of, xii. 7. 8.
Deliberation, what, xxxiv. i.
Defire, origin of, xi. 2. 3.
Diabetes explained, xxix. 4.

with bloody urine, xxvii. 2.

in the night, xviii. 15.
Diarrhoea, xxix, 4.
Digeflion, xxxiii. i. xxxvii.

ftrengthened by emetics, xxxv. i. 3.

ftrengthened

INDEX.

ftrengthened by regular hours, why, xxxvi. 2. i.
Digitalis, ufe of in dropfy, xxix. 5. 2.
Dilirium, two kinds of, xxxiii. 1.4. xxxiv. 2. 2.
cafes of, iii. 5. 8.
prevented by dreams, xviii. 2.
Diftention acts as a ftimulus, xxxii. 4.

See Extenfion.
Diftinguifliing, xv. 3.
Diurnal circle of actions, xxv. 4.
Doubting, xv. 3.
Dreams, viii. 1.2. xiv. 2. 5.

their inconfiftency, xviii. 16.
no furprife in them, xviii. 17.
much novelty of combination, xviii. 9.
Dropfies explained, xxh. 5. i.
Dropfy cured by infanity, xxxiv. 2. 7.

cure of, xxix. 5.2.
Drunkennefs. See Intoxication, xxi.

diminimed by attention, xxi. 8.
Drunkards weak till ne-.tday, xvii. i. 7.

ftammer, and ftagger, and weep, xii. 4. i . xxi. 4,
fee objects double, why, xxi. 7.
become delirious, fleepy, ftupid, xxi. 5.
Dyfpnoea in cold bath, xxxii 3. 2.

Ear, a good one, xvi. 10.

noife in, xx. 7.
Eggs of frogs, fifh, fowl, xxxix. 2.

of birds, why fpotted, xxxix. 5.
with double yolk, xxxix. 4. 4.
Electricity, xii. i . xiv. 9.

jaundice cured by it, x.xx. 2.
Embryon produced by the male, xxxix. 2.
confifts of a living fibre, xxxix. 4.
abforbs nutriment, receives oxygen, xxxix. i.
its actions and fenfations, xvi. 2.
Emetic. See Vomiting.

Emotions, xi. 2. 2. .

Ennui, or tsedium vita:, xxxiv. 2. 3. xxxiii. i. i. xxxix. 6.
Epileptic fits explained, xxxiv. 1.4.. xxvii. 2.

in deep, why, xviii. 14»& 15.
Equinoctial lunations, xxxii. 6.
Excitability perpetually varies, xii. 1.7.

fynonymous to quantity of fenforial power, xii. l. 7.
Exercife, its ufe, xxxii. 5. 3. _

INDEX.

Exertion o/ fenforial power defined, xii. 2. I.

Exigence in fpace, xiv. 2. 5.

Extenfion, fenfe of, xiv. 7.

Eyes become black in fome epilepfies, xxvii. 2.

Face, Burning of after dinner, xxxv. I. i.

why firft affefted in fmall-pox, xxxv. I. T.
red from inflamed liver, xxxv. 2. 2
Fainting fits, xii. 5. i. xiv. 7.
Fear, language of, xvi. 8. i.

a caufe of fever, xxxii. 8.
caufe of, xvii. 3. 7.

Fetus. ' See Embryon, xvi. 2. x: xix. i.
Fevers, irritative, xxxii. i.

intermittent, xxxii. i. xxxii. 3.

fenfitive, xxxiii. i.

not an effort of nature for relief, xxxii. 10*

parcr-yfms of, xii. 7. i . xii. 2. 3. xii. 3. 5.

•why fome intermit and not others, xxxvi. I.

cold fits of, xxxii. 4. xxxii. 9. xvii. 3.3.

periods of, xxxvi. 3.

have folar or lunar periods, xxxii. 6.

fource of the fymptoms of, xxxii. i.

proftration of ftrength in, xii. 4* I. xxxii. 3. 2.
X cure of, xii. 6. i.

how cured by the bark, xii. 3. 4.

cured byincreafed volition, xii. 2.4. xxxiv* 2. 8.

beft quantity of flimulus in, xii. 7. 8.
Fibres. See Mufcles.

their mobility, xii. i. 7. xii. i. I.

contractions of, vL xii i. i.

four clafles of their morions, vi.

their motions diftinguifheo* from fenforial ones, v. 3.
Figure, xiv. 2. 2. iii. I.
Fifti, their knowledge, xvi. 14.
Foxglove, its ufe in dropjfies, xxix. 5. 2.

overdofe of, xxv. 17.
Free-will, xv. 3. 7.

G.

Gall-ftone, xxv. 1 7. See Bile-ftones.
Generation, xxxiii. i . jcxxix.
Gills of Fifh, xxxviii. 2.

Glands,

INDEX.

Glands, xxii. i. conglobate glands, xxii. 2.
have their peculiar ftimulus, xi. i.
their fenfes, xiv. 9. xxxix. 6.
invert their motions, xxv. 7.
increafe their motions, xxv. 7.
Golden rule for exhibiting wine, xii. 7. 8.
for leaving off wine, >:ii. 7. 8.

Gout from inflamed liver, xxxv. 2. 2. xviii. 15. xxiv. 2. &
in the ftomach, xxiv. 2. 8. xxv. 17.
why it returns after evacuations, xxxii. 4.
owing to vinous fpiritonly, xxi. 10.
periods of, xxxvi. 3. 6.
Grinning in pain, xxxiv. i. 3:
Gyration on one foot, xx. 5. and 6.

H.

Habit defined, ii. u. iv. 7.
Haemorrhages, periods of, xxxvi. 3. 1 1.

from paralyfis of veins, xxyii. I, and 2.
Hair and nails, xxxix. 3. 2.
colour of, xxxix. 5. i.
Harmony, xxii. 2.
Head-achs, xxxv. 2. I.
Hearing, xiv. 4.
Heat, fenfe of, xiv. 6. xxxii 3. r.

produced by the glands, xxxii. 3.

external and internal, xxxii. 3. i.

atmofphere of heat, xxxii. 3. i.

increafes during fleep, xviii. 15.
Hemicrania, xxxv. 2. i.
Hemicrania from decaying teeth, xxxv. 2. I.
Hepatitis, caufe of, xxxv. 2. 3.
Hereditary difeafes, xxxix. 7. 6.
Hermaphrodite infects, xxxix. 5.
Herpes, xxviii. 2.

from inflamed kidney, xxxv. 2. 2.
Hilarity from diurnal fever, xxxvi. 3. i.
Hunger, fenfe of, xiv. 8.
Hydrophobia, xxii. 3. 3.
Hypochondriacifm, xxxiii. i. i. xxxiv. 2. 3.

I.

Ideas defined, ii. 7.

aie motions of the organs of fenfe, iii, 4. xviii. 5, xviii. 10.
i. 6,

Ideas

INDEX.

Ideas analogous to mufcular motions, iii. 5.
continue fome time, xx. 6.
new ones cannot be invented, iii. 6. I.
abftracted ones, iii. 7. 4.
inconfiftent trains of, xviii. 1 6.
perifh with the organ of fenfe, iii. 4. 4.
painful from inflammation of the organ, iii. 5. 5.
irritative ones, vii. i. 4. vii. 3. 2. xv. 2. xx. 7.
of refemblance, contiguity, caufation, viii. 3. 2. x. 3. 3.
refemble the figure and other properties of bodies, xiv. t. 2.
received in tribes, xv. i.
of the fame fenfe eafier combined, xv. i. i.
of reflection, xv. i. 6. ii. 12.
Ideal prefence, xv. i . 7.
Identity, xv. 3.5. xviii. 13.
Iliac paflion, xxv. 15, >

Imagination, viii. i. 2. xv. i. 7. xr. 2. 2.

of the male forms the fex, xxxix. 6.
Immaterial beings, xiv. i. xiv. 2. 4.
Imitation, origin of, xii. 3. 3. xxxix. 5. xxii. 3. xvi. 7.
Impediment of fpeech, xvii. i. 10. xvii. 2. 10.
Infection. See Contagion.
Inflammation, xii. 2. 3. xxxiii. 2. 2.

great vafcular exertion in, xii. 2. I.
Hot from pains from defect of ftimulus, xxxiii. 2. 3.
of parts previoufly infenfible, xii. 3. 7.
often diflant from its caufe, xxiv. 8.
obferves folar days, xxxii. 6.
of the eye, xxxiii. 3. i .

of the bowels prevented by their continued action in
- fleep, xviii. 2.

Inoculation with blood, xxxiii. 2. 10.
Infane people*, their great ftrength, xii. i.
Infanity (fee Madnefs) pleafurable one, xxxiv. 2. 6.
Infects, their knowledge, xvi. 1 5. and 1 6.
in the heads of calves, xxxix. i .
clafs of, xxxix. 4. 8.
Inftinctive actions defined, xvi. i .
Inteftines, xxv. 3.
Intoxication relieves pain, why, xxi. 3.

from food after fatigue, xxi. 2.
difeafes from it, xxi. 10.
See Drunkennefs.
Intuitive analogy, xvii. 3. 7.
Invention, xv. 3. 3.

Irritability increafes during fleep, xviii. !£•
Itching, xiv. 9.

Jaw-locked,

INDEX.

J.

Jaw-locked, xxxiv. i. 5.

Jaundice from paralyfis of the liver, xxx. 2.

cured by electricity, xxx. 2.
Judgment, xv. 3.

K.

Knowledge of various animals, xvi. 1 1.

L.

Lacrymal fack, xvi. 8. xxiv. 2. and 7.
Lacleals, paralyfis of, xxviii. See Abforbents.
Lady playing on the harpfichord, xvii. 2.

diftrefled for her dying bird, xvii. 2. 10.
Language, natural, its origin, xvi, 7. and 8.

of various paflions defcribed, xvi. 8.
artificial, • of various animals, xvi. 9.
theory of, xxxix. 8. 3.
Lapping of puppies, xvi. 4.
Laughter explained, xxxiv. 1.4.

from tickling, xvii. 3.5. xxxiv. 1.4.
from frivolous ideas, xxxiv. 1.4. xviii. 12.
Life, long, art of producing, xxxvii.
Light has no momemtum, iii. 3. i.
Liquor amnii, xvi. xxxviii. 2.
is nutritious, xxxviii. 3.
frozen, xxxviii. 3.
Liver, paralyfis of, xxx. i . 4.

large of geefe, xxx. i. 6.
Love, fentimental, its origin, xvi. 6.

animal, xiv. 8. xvi. 5.
Lunar periods affect difeafes, xxxii. 6.
Luft, xiv. 8. xvi. 5.
Lymphatics, paralyfis of, xxviii. See Abforbents.

M.

Mad-dog, bite of, xxii. 3.3.

Madnefs, xxxiv. 2. I. xii. 2. i.

Magnetifm, xii. i. i.

Magnifying objects, new way of, xl. 10. 5.

Male animals have teats, xxxix 4. 8.

pigeons give milk, xxxix. 4. 8.
Man diftinguifhed from brutes, xi. 2. 3. xvi. 17.
Material world, xiv. i. xiv. 2. 5. xviii. 7.
Matter, penetrability of, xiv. 2. 3,

purulent, xxxiii. 2. 4.
Meafles, xxxiii. 2. 9.

c Membranes*

INDEX.

Membranes, xxvi. 2.
Memory defined, ii. 10. xv. I. 7. xv. 3.
Menftruation by lunar periods, xxxii. 6,
Mifcarriage from fear, xxxix. 6. 5.
Mobility of fibres, xii. i. 7.
Momentum of the blood, xxxii. 5. 2.

fometimes increafed by venefeftion, xxxii. 5. 4.
Monfters, xxxix. 4. 4. and 5. 2.

without heads, xxxviii. 3.
Moon and fun, their influence, xxxii. 6.
Mortification, xxxiii. 3. 3.
Motion is either caufe or effect, i. xiv. 2. 2.

primary and fecondary, L

animal, i. iii. i .

propenfity to, xxii. i.

animal, continue ibmctirae after their production, xvii. 1.3.

defined, a variation of figure, iii. i. xiv. 2. 2. xxxix. 7.
Mucus, experiments on, xxvi. i.

fecretion of, xxvi. 2.
Mules, xxxix. 4. 5. and 6. xxxix. 5. 2.
Mule plants, xxxix. 2.
Mufcae volitantes, xl. 2.
Mufcles conftitute an organ of fenfe, xiv. 7. ii. j.

ftimulated by extenfioD, xi. i. xiv. 7.

contra® by fpirit of animation, xii. i . I . and 3.
Mufic, xvi. 10. xxii. 2.
Mufical time, why agreeable, xii. 3. £.

N.

Naufea, xxv. 6.
Nerves and brain, ii,-2. 3.

extremities of, form the whole fyflem, xxxvii. 3.
are not changed with age, xxxvii. 4,
Nervous pains defined, xxxiv. i. I.
Number defined, xiv. 2. 2.
Nutriment for the embryon, xxxix. 5. 2.
Nutrition owing to ftimulus, xxxvii. 3.
by animal feleition, xxxvii. 3.
when the fibres are elongated, xxxvii. 3.
like inflammation, xxxvii. 3.

O.

Objects long viewed become faint, iii. 3. 2.
Ocular fpeclra, xl.
Oil externally in diabetes, xxix. 4.
Did age from inirritability, xxxvii.
Opium is ftimulant, xxxii. 2. 2.

promotes abforption after evacuation, xxxiii. 2. 10.

in increafing dofes> xii. 3. i.

Organs

INDEX.

Organs of fenfe, ii. 5. and 6.

Organs when deftroyed ceafe to produce ideas, iii. 4. 4.

Organic particles of Buffon, xxxvii. 3. xxxix. 3, 3.

Organ-pipes, xx. 7.

Oxygenation of the blood, xxxviii.

P.

Pain from excefs and defect of motion, 17*5. xii. 5. 3. xxxiv. l»
xxxv. 2. i.

not felt during exertion, xxxiv. I. 2.
from greater contraction of fibres, xii. J. 6.
from accumulation of fenforial power, xii. 5. 3. xxiii. 3. l->
from light, prefTure, heat, cauflics, xiv. 9.
in epilepfy, xxxv. 2. i.
diftant from its caufe, xxiv. 8.
from itone in the bladder, xxxv. 2. i.
of head and back from defect, xxxii. 3.
from a gall-ftone, xxxv. 2. i. xxv. 17.
of the ftomach in gout, xxv. 17.
of moulder in hepatites, xxxv. 2. 4.
produces volition, iv, 6.
Palenefs in cold fit, xxxii. 3. 2.
Palfies explained, xxxiv. i. 7.
Paralytic limbs ftretch from irritation, vii. I. J.

patients move their found limb much, xii. 5. i.
Paralyfis from great exertion, xii. 4. 6.
from lefs exertion, xii. 5. 6.
of the lacteals, xxviii.
of the liver, xxx. 4.
of the right arm, why, xxxiv. I. 7.
of the veins, xxvii. 2.

Particles of matter will not approach, xii. i . I.
Paffions, xi. 2. 2.

connate, xvi. I.
Pecking of chickens, xvi. 4.
Perception defined, ii. 8. xv. 3. i.
Periods of agues, how formed, xxxii. 3. 4.
of difeafes, xxxvi.

of natural actions and of difeafed actions, xxxvi.
Perfpiration in fever-fits, xxxii. 9. See Sweat.
Petechiz, xxvii. 2.

Pigeons fecrete milk in their ftomachs, xxxix. 4. 8.
Piles, xxvii. 2.

Placenta a pulmonary organ, xxxviii. 2.
Pleafure of life, xxxiii. i. xxxix 5.

from greater fibrous contractions, xii. I. 6.
what kind caufes laughter, xxxiv. i . 4.
what kind caufes fleep, xxxiv. I. 4.
Pleurify, periods of, xxxvi. 3. 7.
caufe of, xxxv. 2. 3.

c 2 Prometheus

INDEX.

Prometheus, ftory of, xxx. 3.

Proftration of ftrength in fevers, xii. 4« '•

Pupils of the eyes large, xxxi. i .

Pulfe quick in fevers with debility, xii. I. 4. xii. 5. 4. xxxii. 2. *.

in fevers with ftrength, xxxii. 2.

from defect of blood, xxxii. 2. 3. xii. I. 4.

weak from emetics, xxv. 17.

CL

Quack advertifements injurious. Preface.
Quadrupeds have no fanguiferous lochia, xxxviii. 2.

have nothing fimilar to the yolk of egg, xxxix. I.

R.

Rhaphania, periods of, xxxvi. 3. 9.
Reafon, ix. i. 2. xv. 3.
Reafoning, xv. 3.

Recollection, ii. 10. ix. i. 2. xv. 2. 3.
Relaxation and bracing, xxxii. 3. 2.
Repetition, why agreeable, xii. 3. 3. xxii. 2.
Refpiration affected by attention, xxxvi. 2. i.
Reftleflhefs in fevers, xxxiv. i . 2.
Retrograde motions, xii. 5. 5. xxv. 6. xxix. n.
of the ftomach, xxv. 6.
of the fkin, xxv. 9.
of fluids, how. diftinguifhed, xxix. 8.
how caufed, xxix n. 5.
vegetable motions, xxix. 9.
Retina is fibrous, iii. 2. xl. i.

is active in vifion, iii. 3. xl. i.

excited into fpafmodic motions, xl. 7.

is fenfible during fleep, xviii. 5. xix. 8.
Reverie, xix. i. xxxiv. 3.

cafe of a fleep-walker, xix. 2. * ^ }

is an epileptic difeafe, xix. 9.
Rhymes in poetry, why agreeable, xxii. 2.
K.heumatifm, three kinds of, xxvi. 3,
Rocking young children, xxi. 4.
Rot in fheep, xxxii. 7.
Ruminating animals, xxv. I.

S.

Saliva produced by mercury, xxiii?
by food, xxiii. i.
by ideas, xxiii. 2. and 5.
by difordered volition, xxiii. 7,
Schirrous tumours revive, xii. 2. 2.
Screaming in pain, xxxiv. i. 2.
Scrophula, its temperament, xxxi. i.
xxviii. 2. xxxix. 4. 5.

Scurvy,

INDEX.

Scurvy of the lungs, xxvii. 2.
Sea-ficknefs, xx. 4.

flopped by attention, xx. 5.
Secretion, xxxiii. i. xxxvii.

increafed during deep, xviii. 16.
Seeds require oxygenation, xxxviii. 2.
Senfation defined, ii. 9. v. 2. xxxix. 8. 4.
difeafes of, xxxiii.

from fibious contractions, iv. 5. xii. i. 6.
in an amputated limb, iii. 7. 3.
affects the whole fenforium, xi. 2.
produces volition, iv. 6.
Senfibility increafes during fleep, xviii. 1 5.
Senfitive motions, viii. xxxiii. 2. xxxiv. i.
fevers of two kinds, xxxiii. i. 2.
ideas, xv. 2. 2.
Senforium defined, ii. i.
Senfes correct one another, xviii. 7.

diftinguifhed from appetites, xxxiv. I. I,
Senforial power. See Spirit of Animation.

great expence of in the vital motions, xxxii. 3. 2.
two kinds of exerted in fenfitive fevers, xxxiii. i. 3.
powers defined, v. i *

motions diftinguifhed from fibrous motions, v. 3.
not much accumulated in fleep, xviii. 2.
powers, accumulation of, xii. 5.. i.
exhauftion of, xiii. 4. i.
wafted below natural in hot fits, xxxii. 9. 3.
lefs exertion of produces pain, xii. 5. 3.
lefs quantity of it, xii. 5. 4.
Senfual motions diftinguifhed from mufcular, ii. 7.
Sex owing to the imagination of the father, xxxiv. 5;

xxxix. 7. 6. xxxix. 6. 3. xxxix. 6. 7.
Shingles from inflamed kidney, xxxv. 2. 2.
Shoulders broad, xxxi. i. xxxix. 7.6.
Shuddering from cold, xxxiv. I., i. and 2.
Sight, its accuracy in men, xvi. 6.
Skin, fkurf on it, xxvi. i .
Sleep fufpends volition, xviii. I.
defined, xviii. 21.
remote caufes, xviii. 20.
fenfation continues in it, xviii. 2,.
from food, xxi. i.

from rocking, uniform, founds, xxi. 3.
from wine and opium, xxi. i.
why it invigorates, xii. 5. i.
pulfe flower and fuller, xxxii. 2. 2.
interrupted, xxvii. 2.
from breathing lefs oxygene, xviii. 20.
from being whirled on a millltone, zxiii. 20.

Sleep

INDEX.

Sleep from application of cold, xviii. 20. *' •/•*'*

' induced by regular hours, xxxvi. 2. 2;
Sleeping animals, xxi. 2. 2.
Sleep-walkers. See Reverie, xix. i.
Small-pox, xxxiii. 2. 6. xxxiv. 6. 1.

eruption firft on the face, why, xxxv. I. i. xxxiii. 2. 10.
the blood will not infect, xxxiii. 2.10.
obeys lunations, xxxvi. 4.
Smell, xiv. 5. xvi* 5.
Smiling, origin of, xvi. 8. 4.
Solidity, xiv. 2. i.

Somnambulation. See Reverie, xix. i.
Space, xiv. 2. 2.
Spafm, doctrine of, xxxii. 10.
Spectra, ocular, xl.

miftaken for fpectres, xl. 2.
vary from long infpection, iii. 3.5,
Spirit of animation. See Senforial Power.

of animation caufes fibrous contraction, iv. 2. fi. I. xiv. 2^4.
pofTefTes folidity, figure, and other properties of matter, xiv.

2-5-

Spirits and angels^ xiv. 2. 4.

Stammering explained, xvii. i. 10. xvii. 2. 10.
Stimulus defined, ii. 13. iv. 4. xii. 2. I.

of various kinds, xi. i.

with leflened effect, xii. 3. i.

with greater effect, xii. 3. 3.

ceafes to produce fenfation, xii. 3. 3.
Stomach and inteftines, xxv.

inverted by great ftimulus, xxv. 6.

its actions decreafed in vomiting, xxxv. i. 3.

a blow on it occalions death, xxv. 17.
Stools bkck, xxvii. 2.

Strangury, xxxv. 2. I. • j

Sucking before nativity, xvi. 4.
Suckling children, fenfe of, xiv. 8.
Suggeftion defined, ii. 10. xv. 2. 4.
Sun and Moon, their influence, xxxii. 6.
Surprife, xvii. 3. 7. xviii. 17.
Sufpicion attends madnefs, xxxiv. 2. 4.
Swallowing, act of, xxv. I . xvi. 4.
Sweat, cold, xxv. 9. xxix. 6.

in hot fit of fever, xxxii. 9.
in a morning, why, xviii. 5.
Sweaty hands cured by lime, xxix. 4. 9.
Swinging and rocking, why agreeable, xxi. 3*
Sympathy, xxxv. i.
Syncope, xii. i* xxxiv. 7. 6.

Tape-worm,

INDEX.

Tape-worm, xxxix. 2, 3.
Tafte, fenfe of, xiv. 5.
Tears, fecretion of, xxiv.

from grief, xvi. 8. 2.

from tender pleafure, xvi 8. 5.

from ftimulus of naful duct, xvi. 8. xxiv. 4.

by volition, xxiv. 6.

Teeth decaying caufe head-achs, xxxv. 2. I.
Temperaments, xxxi.
Theory of medicine, wanted. Preface.
Third, fenfe of, xiv. 8.

why in dropfies, xxix. 5.
Tickle themfelves, children cannot, xvii. 3^5.
Tickling, xiv. 9.
Time, xiv. 2. 2! xviii. 12.

lapfe of, xv. 3. 6.

poetic and mufical, why agreeable, xxii. 2.

dramatic, xviii. 12.
Tsedium vitae. See Ennui.
Tooth-edge, xvi. 10. iii. 4. 3. xii. 3. 3.
Touch, fenfe of, xiv. 2. i.

liable to vertigo, xxi. 9. *

of various animals, xvi. 6.
Trains of motions inverted, xii. 5. 5.
Transfufion of blood in nervous fever, xxxii. 4.
Tranflations of matter, xxix. 7.
Typhus, beft quantity of flimulus in, xii. 7. 8.
periods of obferve lunar days, xxxii. 6.

U.
Ulcers, art of healing, xxxiii. 3* 2.

of the lungs, why difficult to heal, xxviii. 2.
Uniformity in the fine arts, why agreeable, xxii. 2.
Urine pale in intoxication, xxi. 6.

paucity of in anafarca, why, xxix. 5.

its paflage from inteftines to bladder, xxix. 3,

copious during fleep, xviii. 15.

V.

Variation, perpetual, of irritability, xri. 2. I.
Vegetable buds are inferior animals, xiii. I.

exactly referable their parents, xxxix.

pofTefs fenfation and volition, xiii. 2.

have aflbciate and retrograde motions, xiii. 4. xxix. 9.

their anthers and ftigmas are alive, xiii. 5.
Vegetables have organs of fenfe and ideas, xiii. 5. •

contend for light and air, xxxix. 4. 8.

duplicature of their flowers, xxxix. 4. 4.

Veins

INDEX.

Veins are abforbents, xxvii. I.

paralyfis of, xxvii. I.
Venereal orgafm of brutes, xxxii. 6.
Venxfeclion in nervous pains, xxxii. 5. 4.
Verbs of three kinds, xv. 3. 4.
Verfes, their meafure, xxii. 2.
Vertigo, xx. defined, xx. n.

in looking from a tower, xx. I.
in a fhip at fea, xx. 4.
of all the fenfes, xxi. 9.
by intoxication, xxxv. I. 2.

Vibratory^notions perceived after failing, xx.5» xx. 10.
Vinegar makes the lips pale, xxvii. I.
Vis medicatrix of nature, xxxix. 4. 7.
Vifion, fenfe of, xiv. 3,
Volition defined, v. 2. xxxiv. I.

affects the whole fenforium, xi. 2.
difeafes of, xxxiv.
Voluntarily, x. 2. 4.
Voluntary motions, ix. xxxiv. I.
ideas, xv. 2. 3.

criterion of, xi. 2. 3. xxxiv. I.
Vomiting from vertigo, xv. 8.

from drunkennefs, xx. 8. xxi. 6.

by intervals, xxv. 8.

by voluntary efforts, xxv. 6.

of two kinds, xxxv. I. 3.

in cold fit of fever, xxxii. 9. I.

flopped by quickfilver, xxv. 16,

weakens the pulfe, xxv. 17.

W.

Waking, how, xviii. 14.

Walking, how learnt, xvi. 3.

Warmth in fleep, why, xviii. 15.

Weaknefs defined, ?ii. I. 3. xii, 2. I. xxxii. 3. 2.

cure of, xii. 7. 8. See Debility.
Wit producing laughter, xxxiv. 1.4.
World generated, xxxix. 4. 8.
Worm-fluke, xxxii. 7.

END OF THE FIRST VOLVMS,

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