the

anatomy

OF T H

human bones, nerve sr

AND

LACTEAL SAC and DUCT.

Jv Alexander Monro, femor, M. D. and F. R. Ss.
"Fellow of rhe Royal College of Phyfitians, and
Profeflor of Medicine and Anatomy in the •
Cniverfity of Edinburgh.

A NEW EDITION.

TO WHICH IS ADDED,

A N

ESSAY

\

O N

COMPARATIVE ANATOMY.

EDINBURGH*:

Printed for W. GORDON, Parliament-Square, acd
J. DICKSON, Front of the Exchange,

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TO THE

STUDENTS of ANATOMY

IN THE

University of EDINBURGH.

Gentlemen,

WHEN this Oncology was fir ft printed in
1726, I did not know that Albinus,
Winfxow, and Palfyn, were to pabiiih defcrip-
tions of the bones ; othenvife, my papers pro-
bably would have remained yet undelivered to
the printers. I however flatter myfelf, that
this ejjhy has been of ufe to the gentlemen
who did me the honour to attend my lectures,
by aflifting them to underftand my fenfe and
reprefentation of things in this fundamental
part of anatomy ; and that it has poiflbly been
of more advantage to them than a more com-
plete work from an abler hand, unlefs my de-
monftrations had been in the order and method
of fuch an author.

This view of your improvement, Gentlemen,
is a prevailing argument with me to caufe this
eflay to be reprinted ; and you cannot reafon-
ably blame me, if I like wife acknowledge an-
other motive for it, which more particularly re-
lates to myfelf. In a new edition, an author

A 2 has

( iv )

has an opportunity of making his works more
correct, complete, and confequently acceptable
to the public, who may perhaps be indulgent
enough to think this little treatife not altoge-
ther ufelefs ; fince more reafoning on the ftruc-
ture and morbid phenomena of bones is to be
found in it, thau in the other writers, who have
confined themfeives almoft entirely to the de-
feriptive or proper anatomical part of the ojleo-

k W-

1 have here kept to the plan of the former
editions, by firft confidering, in the order that
feemed to me mod natural and methodical, every
thing which I thought necefiary to be known
concerning bones in general ; and, in the fe-
cond parr, I have described the fcveral bones
compofing the fkeleton.

The bones of adults are what I principally
endeavour to defer .'be ; but I have added as
much of the ofleogenca as I think ferviccable in
the practice of phyfic and forgery.

That little might be omitted of hr.t was
formerly done on this fubjeft, I have taken all
the afiiftance 1 could from books ; but have
never ailcrtcd any anatomical faft on then* au-
thority, without confulting nature, from which
all the defer iptions are made ; and therefore, the
quotations from fuch books ferve only to do
juftice to the authors, who have remarked any
thing in the lirufture of the parts that was
commonly omitted, and to initiate you in the
hiftory of anatomy ; which I once propefed to
make complete, fo far as related to this fubjeft:
But not being able to procure fe?eral books,

onn

■; ‘ ( v )

and being fenfible how many more may have
never come to my knowledge, I laid afide this
defign, of purpofe omitted many I could have
inferted, and in fome places 1 have changed an
older author for a later one, who has more ful-
ly or clearly defcribed what I treated of. Be-
fide anatomifts, I have alfo named feveral other
authors to confirm my reafoning by pra&ical
cafes ; of which it is not to be fuppofed my
own experience could furnifh. a fufficient va-
riety.

You will readily obferve, that I quote no
paffages with a view to criticife or condemn
them. This precaution of giving no offence,
is very neceffary in thofe who are fufificiently
confcious of their being liable to lay themfelves
open to juft cenfure ; and it prevents occafions
of ufelefs wrangling, in which generally both
parties are lofers, and the public has little ad-
vantage.

In this treatife I always make ufe of the moft
common name of each part, and have put the
fynonimous names to be met writh in books at
tiie foot of the page, that the reading might
be fmoother, and you might confult them at
your leifure to affift you in underftanding dif-
ferent authors.

The deferiptions and reafoning, are here
blended, without which I always find young ana-
tomifts are foon difgufted with authors: Their
imaginations cannot follow a long chain of de-
feriptions, efpecially when they are not taught
at the fame time the ufes which the defcribed
parts ferve : Their minds muft have fome re-

a 3 laxation,

( Vi )

laxation, by a mixture of reafoning, which ne-
ver miffes to Strike the fancy agreeably, and
raifes a ftrong defire to understand the prin-
ciples on which it depends.

The phenomena of difeafes are all deduced
in this ellay from the Structure of the parts, by
way of corollaries and questions ; which Such
an anatomical work confined me to. And this
method has otherwife a good effect: For, when
one meets with an ufeful propofition, and is
obliged to employ a little thought to find out
its Solution, the impreflion it makes is deeper,
and he acquires a fondnefs for it, as being, in
part, his own difcovery. My pupils have fre-
quently allured me, that they could, with very
fmall reflection, trace out the whole reafoning
from which my conclufions were drawn ; I hope
their fucceffors will alfo think this an agree-
able manner of being inftruCted.

Thofe gentlemen who defired I would add
the leCtures which 1 pronounce in my colleges
as a commentary upon the text, where the dif-
eafes are mentioned, will, I perfuade myfelf,
excufe me for not complying with their defire,
when they confider the defign of this is to be a
fchool-book, and how great the difference is
between inftruCting youth in private, and pre-
tending to inform the public. Art. xxiv. vol. v.
of Medical Effays and Observations, publifhed
in this place, is one of thefe leCtures which I
gave as a commentary on the paragraph (p. 9.)
concerning the diiferent kinds of caries.

In this edition, I have corrected the miflakes
and obfeure paffages which I difeovered in the

former ;

( ™ )

former ; and, in fome places, I have made the
defcriptions more full and exa<ft, aiming all I
could to (hun unneceffary minutenefs on the one
hand, and a blameahle inaccuracy on the other :
Whether I have hit that juft medium, is what
you and the public muft now judge.

I am ftill of opinion, that figures of the bones
would at any rate have been unneceffary in a
book that is intended to be illuftrated and ex-
plained by the originals themfelves ; but would
be much more fo now, when my late ingenious
friend Mr. Chefelden, Dr. Albinus, and Mr.
Sue ( a ), have publifhed fuch elegant ones.

You have advantageous opportunities in this
place of ftudying all parts of medicine, under
the profeflors of its different branches in the
Univerfity, and of feeing the practice of phar-
macy, furgery, and phyfic, with our furgeon-
apothecaries, and in the Royal Infirmary, where
the difeafed poor are carefully treated. Thefe,
your intereft, and, I hope, your inclinations,
will lead you, Gentlemen, fo to improve, as
that they may become the happy means of your
making a confiderable figure in your feveral
ftations. Whatever afliftance is in my power
towards fuch a defirable event, {hall be given
with the greateft pleafure by

Your humble fervant,

ALEX. MONRO.

(a) Traite d’ofteologie, traduit de l’Anglois de
M. Monko, feconde partie.

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THE

ANATOMY

OF THE

HUMAN BONES.

PART I.

Of the BONES in general.

BONES are covered by a membrane, named,
on that account, Periosteum*, which is
fo neceffary to them, that we mud examine
its texture and uies, before we can underdand their
drudhure. •

The periojleum, as well as mod other membranes,
can be divided into layers of fibres. The exterior
ones, compofed of the fibres of the mufcles con-
nected to the bones, vary in their number, fize, and.
direction, and confequently, occafion a very great
difference in the thicknefs and drength of the perio -
Jleum of different bones, and even of the different
parts of the fame bone. The internal layer is every
where nearly of a fimilar drudture, and has its fibres
in the fame direction with thofe of the bone to
which they are contiguous. Ought nob' then the
name per iojleum to be applied, dridtly fpeaking, only
to this internal layer, to which the others are joined
in an uncertain manner and number ? #

A Some

* Membrana circtunoflalis, omentum ofCbus impofitum.

2 Of the BONES in GENERAL.

Some authors (a) endeavour to prove the internal
layer of fibres ot the pariojieum to be derived from
the dura mater : For, fay they, fince the membrane
covering the fcull is plainly a produ&ion or conti-
nuation of the dura matery which paffes out between
the futures ; and fince there are mufcles on the head,
as well as in other parts, which might furnifh a pe~
ricjleumt it is needlefs to afiign different origins to
membranes which have the fame texture an<J ufes.
They add further, in proof of this do&rine, that
the periojleum extends itfelf along the ligaments of
the articulations from one bone to another; and
therefore is continued from its origin over all the
bones of the body. — While anatomills were fond of
the hypothefis of all membranes being derived from
one or other of the two that cover the brain, a dif-
pute of this kind might be thought of confequence :
But, now that the hypothefis is negte&ed as ufelefs,
it is needlefs to examine the arguments for or a-
gainft it. ,

Except where mufcles, cartilages, or ligaments,
are inferted into the periojleum , its external furface is
connected to the furrounding parts by thin cellular
membranes, which can eafily be ftretched confider-
ably, but fiiorten themfelv** whenever the ftretching
force is removed. When thefe membranes are cut
off or broken, they collapfe into fuch a fmall fpace,
that the furface of the periofttum feems fmooth and
equal.

When we attempt to tear off the periojleuni from
bones, we fee a great number of white threads pro-
duced from the membrane into them; and, after at
fuccefsful inje&ion of the arteries with a red liquor,,
numerous veffels are not only feen on the perio-
Jicum ( b ), but mod of the fibres fent from the mem-
brane to the bone, fhew themfelves to be veffels en-
tering it, with the inje&ed liquor in them ; and!
when they are broken, by tearing off the perioJleumt

the

(a) Havers Ofteolog. nov. dife. I. p. l6.

(i) Ruyfch. cpift. j. tab. 5, fig- I, l, cpift, 8. tab. 9. fis- I, ?•

Of the BONES in GENERAL. 3

the furface of the bone is almoft covered with red
points.

The veins correfponding to thefe arteries are
fometimes to be feen in fubje&s that die with their
veflels full of blood ; though l'uch numerous ramifi-
cations of them, as of the arteries, can feldom be
demon ftrated, becaufe few of them naturally con-
tain coloured liquors, and fuch liquors can difficult-
ly be injected into them. This, however, is lome-
times done (a).

The great lenfibility of the periojleum in the deep-
feated fpecies of paronychia , in exojlofes, nodi, tophi ,
and gummata, from a lues venerea, or whenever this
membrane is in an inflamed ftate, is a fufficient
proof that it is well provided with nerves, though
they are perhaps too fmall to be traced upon it ;
and therefore, one cannot well determine, whether
they are fent alon£ with the arteries in the common
way, or are derived from the tendinous fibres of the
mufcles expanded on the perio/leum (b).

Veflels alfo pafs through the periojleum to the
marrow ; of which more hereafter. And frequently
mufcles, ligaments, or cartilages, pierce through the
periojleum , to be inferred into the bones.

The chief ufes of the periojleum are, r. To al-
low the mufcles, when they contract or are ftretch-
ed, to move and Aide eafily upon the bones ; the
l'mooth furface of this membrane preventing any ill
effe&s of their friCtion upon each other. 2. To
keep in due order, and to fupport the veflels in their
paflage to the bones. 3. By being firmly braced on
the bones, to affift in fetting limits to their increafe,
and to check their overgrowth. 4. To ftrengthen
the conjunction of the bones with their epiphytes , li-
gaments, and cartilages, which are eafilv ie para ted

A 2 in

(a) Sue traite d’oftcologie, traduit de I’Anglois dc Mr. Monro.
Note in page y.

(A) See the dilpute about the fenfbility of this and of other mem-
branes in Zimmerman. Diflert. de irritabilit. — Adt. Gotting. vol. I —
Haller fur la nature l'enfible et irritable. — Whytt’s phyllolog. cllay II.
— Renwr. dillcrt. dc fungo articulor. § a6. 34.

4 Of the BONES in GENERAL.

in young creatures, when this membrane is taken a-
way. 5. To afford convenient origin and infertion
to leveral muicles which are fixed to this membrane.
And, lajlly, To warn us when any injury is offered to
the parts it covers ; which, being infenfible, might
otherwife be deftroyed without our knowledge, or
endeavouring to procure a remedy.

When the cellular fubftance conne&ing th c perio-
jleum to the furrounding parts is deftroyed, tbefe
parts are fixed to that membrane, and lofe the Hiding
motion they had upon it ; as we fee daily in iffues,
or any other tedious fuppurations near a bone. —
When the veffels which go from the periojleum to
the bones are broken or eroded, a collection of li-
quor is made between them, which produces a for-
did ulcer or rotten bone. This often is the cafe af-
ter fraCtures of bones, and inflammations of the
periojleum y or after fmall pox , meafies^ f potted fevers ,
and erftpelas. — Do not the diforders of the perioJleumt
coming rather along with, or foon after the cutaneous
than other difeafes, indicate fome fimilarity of flruc-
ture in the periojleum and fkin ?

The Bones are the mod hard and folid parts of
the body, and, as all other parts where large veflels
do not enter, are generally of a white colour ; only-
in a living creatqre they are blutifh, which is owing
to the blood in the fmall veflels under their furface.
The lefs, therefore, and fewer the veffels are, and the
thicker and firmer the bony furface covering the vef-
fels is, the bones are whiter. Hence the bones of
adults are whiter than thofe of children ; and, in
both young and old, the white colour of different
bones, or of the feveral parts of the fame bone, is
always in proportion to their veffels and folidi ties ;
which circumftances ought to be regarded by fur-
geons, when they are to judge of the condition of
bones laid bare.

Bones are compofed of a great many plates *, each
of which is made up of fibres or firings united by

fmaller

* Squamae, braftez, laminae.

Of the BONES in GENERAL. 5

Smaller fibrils (a) ; which being irregularly difpofed,
and interwoven with the other larger fibres, make a
reticular work. — This texture is plainly feen in the
bohes of foetufes,»which have not their parts clofely
compared, and in the bones of adults which have
been burnt, long expofed to the weather, or whofe
compofition has been made loofe by difeafes. — The
chinks which are generally made, according to the
dire&ion of the larger fibres of bones that have un-
dergone the a&ion of fire, or of the weather, Shew
the greater ftrength of thefe than of the fibres which
conneft them. — Numerous accurate observations of
the different times in which exfoliations are made
from the fides or ends of Similar bones, might bid
fair to determine what is the proportional force of co-
hefion in the two forts of fibres.

The plates are Said (b) to be firmly joined to each
other by a great number of claviaili , or Small bony
procefles, which, rifing from the inner plates, pierce
through fome, and are fixed into the more external
ones. Of thefe nails four kinds, viz. the perpendicu-
lar, oblique , headed , and crooked , have been defcribed :
But in bones fitly prepared, I could only See nume-
rous irregular procefles rifing out from the plates ( c ).

Though the exterior part of bones is compofed of
firm compact plates, yet they are aH more or lefs ca-
vernous internally. In fome (e. g. middle thin part
of the fcapula and os ilium ) the Solid fides are brought
fo near, that little cavity can be feen ; and in others
(middle of os humeri , femoris , &c.) the cavities are
fo large, that Such bones are generally efteemed to be
hollow or fiftular. But the internal Spongy texture
is evident in young animals •, and fome of it may be
feen to remain in thofe of gceatell age, when bones
are cautioufly opened after they have been kept fo
long as to be free of the oil they contain, or after
being burnt.

A 3 This

(a) Malpigh. Anat. plant, et oper. pofth.

(b) Gagliard. Anat. offinm, nov. invent. iUuftrat. cap. I.. cb£ 2..

(c) Malpigh, oper. polthuou.

6 Of the BONES in GENERAL.

This fpongy cavernous internal part of bones* is
generally called their cancelli or Lattice-work,
and is formed in the following manner. The plates
are firmly joined about the middle of the bone: but
as they are extended towards its ends, the more in-
ternal plates feparate from the exterior, and flretch
out their fibres towards the axis of the bone, where
they are interwoven with the fibres of other plates
that have been fent off in the fame way. Seeing the
plates are thus conflantly going off, the folid fides of
the bones mull become thinner, and the lattice- work
mull be thicker and fironger towards their ends.
This is evident in many of them, where the folid
fides of their middle are very thick, and the cancelFi
are fcarcc obfervable j whereas, at the ends, where
their diameter is greatefl, the folid walls or fides are
not thicker than paper, and the cancelli are numerous
and large enough to fill up the whole fpace left be-
tween the fides.

The twilling and windings which thefe cancelli
make, and the interflices which they leave, differ
confiderably in figure, number, and fize; and there-
fore form little cells, which are as different, but com-
municate with each other. Some writers (a) mi-
nutely remark thefe different appearances of the can -
celliy after they begin to feparate from the plates ;
and from thence diuinguifh them into wrinkled , per-
foratedy and net -like.

The cancelli fuflain the membranous bags of the
marrow which are flretched upon them, and thereby
hinder thefe membranous parts to be torn or remov-
ed out of their proper places, in the violent motions
and different poflures which the bones are employed
in. This fupport which the cancelli afford the mat-
row, alfo faves its membranes and veffels, in the
lower parts of the bones, from being comprefTed by
the weight of the marrow above.

The depreffions between the fibres of the external
plates of bones appear like f<5 many furrows on their

furface,

(a) Gag liar, Anat. offium, cap. I. obf. 4, 5, 6, 7,

Of the BONES in GENERAL. 7

furface, into each of which the periojleum enters ; by
which the furface of contact, confequently the
cohefion, between it and the bone, is confiderably
increafed, and a greater number of vefiels is fent
from it into the bone, than if it was a plain furface.

Both on the ridges and furrows, numerous little
pits or orifices of canals are to be feen, by which the
vefiels pafs to and from the bones.

After a fuccefsful injection, the arteries can be
traced in their courfe from the pits to the plates and
fibres; and, in fawing, cutting, or rafping the bones
of living creatures, thefe vefiels difcover themfelves,
by the fmall drops of blood which then ooze out
from the mod folid part of the bones. But the clear-
eft demonftration of theiDtimate diflribution of thefe
fmall arteries, is, to obferve the effect of fuch a tin-
ging fubftance as can retain its colour, when fwallow-
ed, digefted, and mixed with the blood of any living
animal, and at the fame time has particles fmall e-
nough to be conveyed into the vefiels of the bones;
fuch is rubia tinftorum, madder root (<?) : For we fee
the gradual advances which this tinfture makes from
the periojleum into the more internal parts of the
bones, and how univerfally the diflribution of the li-
quors is made, the whole bony fubftance being tin-
ged. Whether the time in which this tinged liquor
pafies from the outer to the internal plates, till all
the plates are made of its colour, and the time which
the difappearing of the dye, after giving the creature
no more of this fort of food, makes us think it takes
to return, are the fame in which the natural liquors
circulate, is uncertain ; becaufe this tinging fub-
ftance may move more flowly, or may pafs more

quickly, than the natural liquors do The arteries

are larger near each end than at the middle of the
large bones that are much moved; becaufe they not
only ferve the bony plates near the ends, but pafs
through them to the marrow. — As animals advance

in

(a) Philofoph. tranfaft. Num. 44a. art. 8. Num. 443. art. %.
Isum. 43 7. art. 4.— Mem. de l’Acad. des fcicnces, 1739, 174a.

8 Of the BONES in GENERAL.

in age, the arteries of the bones become lefs capa-
cious; as is evident, i. From the bones of adults
having lefs blood in them than thofe of children have.
2. From many of them becoming incapable in old
age of admitting the coloured powders ufed in injec-
tions, which eafily pafs in youth. And, 3. From the
bones of old creatures being more difficultly tinged
with madder than thofe of young ones. — If authors
have not miftaken, the arteries of bones have fome-
times become very large (a).

We may conclude from arteries being accompanied
with veins fo far as we can trace them in every other
part of the body, that' the're are alfo veins in the
bones; and the difappeaimg of the tin&ure of mad-
der , after bones of living 'animals are coloured with
it, could not be without fuch veins to carry it away ;
nay, the veins of bones can fometimes be injected,
and then feen (bj. %

The bones of a living animal are fo infenfible, that
they can be cut, rafped, or burnt, without putting
the creature to pain, and the nerves diftributed in
their fubltance cannot be (hewn by diflettion ; from
which it might be inferred that they have no nerves
diflributed to them : But the general tenor of nature,
which bellows nerves to all the other parts, fhould
prevent our di awing fuch a conclufion. And if fen-
fibility is a fure proof of nerves entering into the
compofition 'of any part, as it is generally allowed to
be, we have fufficient evidence of nerves here in the
bones ; for the granulated red fleffi which fprouts out
from them, after an amputation of a limb, or per-
forming the operation of the trepan , or after an ex -
foliation , is exquifitely fenfible : And, in fome ulcers
of bones, where the periojleum was all feparated, the
patient fuffered racking pain, if the bone was touch-
ed with a rough inftruinent ; nor was he free of pain
after the. bone was perforated (a)— The reafon why.

the

(a) Diemerbroek Anat. lib. 9. cap. 1. — Mery. Iiift. dc l’Acad,.
ics fciences, 1704.

(i) Sue trad, d’ofteolog. p 9.

{a) Nicol. Mafia lib. iotxod. anat.. cap. 3.0*.

9

Of the BONES in GENERAL.

the nerves of rigid hard bones become infenfible, is.
That all nerves rnuft have a confiderable degree of
flexibility at the part where obje£ts are applied, other-
wife it cannot be affefted by their impreffions. We
fee this illuftrated in a very common analogous cafe,
the growth of a-new nail : When the former one has
fuppurated off, the thin membrane which firft ap-
pears, is exquifitely fenfible ; but gradually becomes
dull in its fenfation, till it can be cut or fcraped,
without caufing pain, after it is formed into a hard nail.

From what has been faid of the veflels of bones,
it is evident, that there is a conftant circulation of
fluids in every part of them ; and that there is a per-
petual wade and renewal of the particles which com-
pofe the folid fibres of bones, as well as of other
parts of the body ; the addition from the fluids ex-
ceeding the wafte during the growth of the bones;
the renewal and wafte keeping pretty near par in ad-
ult middle age ; and the wafte exceeding the fupply
from the liquors in old age ; as is demonftrable from
their weight i For each bone increafes in weight, as
a perfon approaches to maturity ; continues of nearly
the fame weight till old age begins, and then be-
comes lighter. — The fpecific gravity of the folid fides,
on the contrary, increafes by age; for then they be-
come more hard, compact, and denfe. In confequence
of this, the bones of old people are thinner and
firmer in their fides, and have larger cavities thaa
thofe of young perfons.

The vafcular texture of bones muft make them
fubjtct to obJlruBions , eccbymofes , ulcers , gangrenes ,
and moft other difeafes which the fofter parts are af-
fe&ed with ; and therefore there may be a greater va-
riety of caries than is commonly defcribed (a).

Hence we can account for the following appear-
ances.

Heemorrhagies from fungous flelh riling out from the
molt folid part of jt cut bone ( b ).

The

(a) Edinburgh Medical e flays and obi", vol. 5. art. 2j.

(4) Medical ellays, vol. 4. art. 21. i

IO Of the BONES in GENERAL*

The regular alternate elevation and fubfiding, or
apparent pulfation, frequently to be feen in fome of
the cells of a carious bone.

Cells refembling cancelliy fometimes feen in the
part of a bone, which, in a natural ftate, is the mod
folid and firm (c).

A bone as a tube including another bone within
it (d).

On the internal furfacc of the folid parts of bones,
there are orifices of canals, which pafs outwards
through the plates to open into other canals that are
in a longitudinal dire&ion, from which other tranf-
verfe paflages go out to terminate in other longitudinal
canals ; and this ftru&ure is continued through the
whole fubftance of bones, both thefe kinds of canals
becoming fmaller gradually as they approach the outer
furfacc (a). — Thefe canals are to be feen to the bell
advantage in a bone burnt till it is white: When it
is broken tranfverfely, the orifices of the longitudinal
canals are in view; and when we feparate the plates, the
tranfverfe ones are to be obferved. Here however we
are in danger of believing both thefe forts of canals
more numerous than they really are ; becaufe the
holes made by the procefl'es conne&ing the plates of
bones, have the appearance of the tranfverfe ( b ), and
the paflages for the blood-veffels refemble the longitu-
dinal canals. I do not know how we are to keep free
of error about the tranfverfe canals ; but think we
may diftinguilh between the two kinds of longitudinal
ones ; for the paflages of the vefiels are largeft near
the external fuxface of the bone, and every tranfverfe
fettion of them is circular ; whereas the longitudinal
canals are largeft near the cancelli , and their tranfverfe
fe&ions appear to me of a flat oval figure, which
may be owing to the different momentum of the fluids
conveyed in them. — The fituation of the larger Ion*
gitudinal canals, and of the paflages of the larger

yeflels.

[i) Rnyfch. Thef. 8. num. 8. Thcf. 10. num. i;6»

( d ) Mem, ibid

(a) Havers Olteolog. nov. p. 43.

(i) Morgagn. Advert". 3. aniaiad, IJ.

II

Of the BONES in GENERAL.

veftels, makes a bone appear more denfe and compaft
in the middle of its folid Tides, than towards its outer
and inner furfaces, where it is fpongy.

We fee marrow contained in the larger tranfverfe
and longitudinal canals juft now defcribed, and from
thence judge that it paffes alfo into the fmaller ones.
The drops of oil which we difcover with a microfcope
every where on the furface of a recent bone, fra£tu-
red tranfverfely, and the oozing of oil through the
moll folid bones of a Ikeleton, which renders them
greafy and yellow, are a confirmation of the ufe of
thefe canals. Of what advantage this diftribution
of the marrow through the fubftance of bones is, will
be mentioned when the nature and ufe of this animal
oil is inquired into.

Moft bones have one or more large oblique canals
formed through their Tides for the paflage of the me-
dullary veftels, which are to be defcribed afterwards.

Bones expofed to a ftrong fire in chemical veftels,
are refolved, in the fame manner as the other parts
of animals, into phlegm, fpirit, volatile fait , fetid oil ,
and a black eaput mortuum. But the proportion of
thefe principles varies according to the age, folidities,
and other circumftanees of bones. Young bones
yield the largeft proportion of phlegm ; fpongy bones
afford moft oil, and folid ones give moft fait and

black refidnum. Though this refduum can fcarce

be changed by the force of fire while it is in clofe
veftels ; yet, when it is burnt in an open fire, the te-
nacious oil, to which it owes its black colour, is for-
ceu away, and a white earth is left that has little or
no fixed fait in it. This earth feems to be the proper
conllituent folid part of bones, and the other princi-
ples give it firmnefs and tenacity : For the quantity of
the earth is fo great, that, after all the other princi-
ples are feparated from a bone, its former (hape and
fize remain (a) j but it is very brittle till it is moif-
tened with water or oil, when it recovers fome tena-
city.— The increafe of the proportion of earth in old

people’s

{«) Havers Oftcolog. nov, difc, x. p. 31,

12 Of THE BONES IK GENERAL.

people’s bones is one reafon of their being more brit-
tle than thofe of young people are.

Left any imagine the falts and oils of bones, while
in a natural ftate, to be of the fame arrid kind with
thofe obtained from them by the chemical analyfis,
it is to be obferved, that thefe principles may be ex-
tracted from bones in the form of a very mild jelly,
by boiling them in water.

The bones fuftain and defend the other parts of the
body.

Bones are lined within, as well as covered exter-
nally, with a membrane ; which is therefore com-
monly called Periosteum Internum.

The internal periofteum is an extremely fine mem-
brane ; nay, frequently it has a loofe reticular tex-
ture ; and therefore it is compared by fome to the a-
rachnoid coat of the fpinal marrow : fo that we cannot
expeCl to divide it into layers as we can divide the ex-
ternal peritjleunu We can however obferve its procefles
entering into the tranfverfe pores of the bones, where
probably they are continued to form the immediate
canals for the marrow diftributed through the fub-
ftance of the bones ; and along with them veflels are
fent, as from the external periofteum , into the bone (/>).
Thefe proceftes being of a very delicate texture, the
adhefion of this membrane to the bone is fo fmall, that
it feparates commonly more eafily from the bone than
from the marrow which it contains : Wherefore, one
might call it the common membrane of the marrow,
rather than by the name it now has. But whether
the one or the other defignation ought to be given it,
is not worthy a difpute.

From the internal furface of the internal pericjleum,
a great number of thin membranes are produced ;
which, pafling acrofs the cavity, unite with others
of the fame kind, and form fo many diftinCl bags,
which communicate with each other ; and thefe a-
gain are fubdivided into communicating veficular
cells, in which the marrow is contained. Hence it

is,

( b ) Window Expodtion anat. dcs os frais, § 8a, 8j.

»3

Of the BONES in GENERAL.

is, that the marrow, when hardened, and viewed
with a microicope, appears like a duller of fmall
pearl ; and that the hardened marrow of bones buried
tong under ground, or laid fome time in water,
and* then dried, is granulcus (a). This texture is
much the fame with what obtains in the other cellu-
lar parts of the body, where fat is colleded ; only
that the cells containing the marrow are fmaller than
thofe of the tunica adipofa or cellttlofa elfewhere, which
probably is owing to their being inclofed in the bones,
where they are not fo much dretched or extended as
in other parts.

The Marrow is the oily part of the blood, fepa-
rated by fmall arteries, and depofirated in thefe cells.
Its colour and confidence may therefore vary accord-
ing to the date of the •vefiels, and their didi ibution on
the membranes of the cells.

The marrow, as well as the other fat of the body
chemically analyfed, yields, befides oil and water, a
confiderable proportion of an acid liquor, but no r.l-
cali (b). This may be the reafon of its being lei's pu-
trefeent than the blood or mod other parts of animals
(e), which is a net diary quality in a fubltance that
is condantly expofed to a confiderable degree of heat,
and is fcuvre in a dagnating condition than the other
liquors.

Befides the arteries, which I mentioned already
(p. 7.), to be fent from the bones to the marrow,
there is at lead one artery for each bone ■, feveral bones
have more, whole principal ufe is to convey and ie-
cern this oily matter. After thefe arteries have pier-
ced the folid fide of a bone, they are divided into fe-
veral branches ; which foon are didributed every where
on the internal periojbeutn, and afterwards fpread their
branches inwards on the medullary cells, and out-
wards through the tables of the bone.

< B The

(") Ruyfch. Thcfaur. 9. num. a. et Adverf. dee. in. obi 9.

(J) Grutzmaker Difiert. de oflium medulla.— Haller Element. phy-
fiolog. lib. 4. left. 4.

(0 Pringle Append, to camp diicalcs, exper. 47.

14 Of the BONES in GENERAL.

The blood which remains after the fecretion of the
marrow, is returned by proper veins, which are col-
lected from the membranes into one or two large
trunks, to pafs out at the fame holes or palTages at
which the artery or arteries enter.

The general rule of the fmall vefTels decreafing in
their capacities as animals advance in age, to which
many phaenomena in the animal oeconomy are owing,
obtains here : For though the trunks of the medulla-
ry vefTels enlarge as animals turn older; yet the fmall
branches become fmaller ; as is evident from injec-
tions, which cannot be made to pafs near fo far in
thele vefTels of adults as of children. Hence the
marrow is bloody in children, oily and balmy in
middle age, and thin and watery in old people.

By experiments made on the marrow, when bones
of living animals are opened or cut through (a), and
from the racking pain with which fuppurations within
bones are frequently attended, we have fufficient
proof that the membranes here are fenfible, and con-
fequently have nerves diflributcd to them. Hippo-
crates ( b ) might therefore fay juflly, that a wound pe-
netrating into the cavity of a bone may produce a de-
lirium.

The vefTels of the marrow, wrapt up in oim com-
mon coat from the per iofieumy pafs through the bones
by proper canals ; the molt confiderable of which are
about the middle of each bone, and are very oblique.
Sometimes thefe vefTels continue at a little diflance
in their pafTage when the canal is divided by a fmall
bony partition or two.

From the flrudure of the contents of the bones,
we may judge how thefe parts, as well as others, may
be fubje£t to oidema, phlegmon, eryfipelas, fchir-
rhus, tsV. and may thence be led to a cure of each,
before the common confequence, putrefa&ion, takes
place, and frequently occaGons the lofs of the limb,
if not of the patient.

' The

(j) Du Verney Memoires dc l’ Acad, dcs fcicnccs, 1 7 00.

(i) Aphorifin. § 7. aph, 24.

*5

Of the BONES in GENERAL.

The marrow is of very confiderable ufe to the
bones; for, by entering their tranfverfe canals, and
pa fling from them into the longitudinal ones, it is
communicated to all the plates, to foften and connect
their fibres, whereby they are preferved from becom-
ing too brittle ; as we fee they do in burnt bones, or
thofe long expofed to the air; in people labouring un-
der old age, pox, or fcurvy : In all which cafes, the
oil is either in too little quantity, or has its natural
good qualities changed for worfe ones.

Befides this advantage which the fu'oflance of bones
has from the marrow, their articulations are faid (a)
to receive no lefs benefit from it : for it is thought
that the marrow pafles into the articular cavities,
through the holes which are in the bones near the
large joints. And, as a proof of this, it is alledged,
that butchers, upon feeing the greater or Jcfl'er quan-
tity of marrow, in the bones of cows, can tell whe-
ther they have travelled far or little before they were
flaughtered.

When the marrow, after having ferved the ufest
mentioned, is reafi'umed into the mafs of blood, (as it
is continually, in common with all other fecreted li-
quors that have not pafl’ages formed for conveying
them out of the body), it corrects the too great acri-
mony communicated to the faline particles of our
fluids by their circulation and heat ; in the fame
manner as lixivial falts are blunted by oil in making
foap. Hence, in acute difeafes, the marrow, as well
as the other fat of the body, is quickly wafted, but
muft be immediately fupplied by liquors from the
vefiels ; feeing the cells within the bones, which have,
no afliftance to their contraction from che preiTure
of the atmofphere, cannot collapfe, as the tela cel~
lularis under the fkin does, when the liquor in its
cells is abforbed ; the bones therefore are always lull.

Since it is the nature of all oil to become thin and
rancid when expofed long to heat, and bones hare

B 2 much

(a) Joan dc Murallo Vade mccum scat, exercit. 5,. § 3,— Have;;
Ofteolog. nov. elite, j. p. 179.

16 Of the BONES in GENERAL.

much oil in their firm hard fubdance, we may know
why an ungrateful l'mell, and dark coloured thin
ichor, proceed more from corrupted bones than from
other parts of the body ; and we can underfland the
reaion of the changes of colour which bones undergo-,
according to their different degrees of mortification. —
Hence likewife we may learn the caufe of a Jpitia
ventofa , and of the difficulty of curing all caries
of bones proceeding from an obdruCfion, and con-
sequent putrefatfion of the marrow ; and of the
quick pulfe, third, and heBic paroxyfms, fo often at-
tending thefe difeafes. Thefe phenomena alfo teach
us the reafon of the fatal prognofis taken from black
fetid urine in fevers.

Though bones fo far agree in their dru&ure and
annexed parts, yet we may obferve a confiderable
difference among them in their magnitude, figure,
iituation, fubltance, connection, ufes, &c. From
•which authors have taken occalion to didinguifh them
into as many claffes as they could enumerate of thefe
different circumdancesi But thefe being obvious to
every perfon that looks on bones, I fliall only men-
tion one of them; which comprehends very near the
whole bones of the body, and at the fame time leads
us to examine the mod confiderable variety that is to
be found in the difpofition of their condituent parts,
and in their ufes. It is this, that fome bones are
broad and_//u/, while others are long and round .

The broad bones have thin fides, by the plates
being foon and equally fent off to form the lattice-
work ; which therefore is thicker, and nearly of an
equal form ail through. By this dru&ure, they are
Avell adapted to their ufes, of affording a large e-
nough furface for the mufcles to rife from, and move
upon, and of defending fudiciently the parts which
they inclofe.

The round bones have thick drong walls in the mid-
dle, and become very thin towards their ends, which
is owing to very few plates feparating at their mid-
dle ; where, on that account, the cancelli are fo fine

and

*7

Of the BONES in GENERAL.

and fmall, that they are not taken notice of: But
fuch bones are faid to have a large refervoir of
oil in this place. Towards their ends the lattice-
work becomes very thick, and rather more complete
than in the other l'ort of bonCs. — i hefe round bones
! having ftrong forces naturally applied to them, and
being otherwil'e expofed to violent injuries, have need
of a cylindrical figure to refill external prefiure, and
of a confiderable quantity of oil to preferve them
from becoming too brittle. Befides which, they are
advantageoufly provided with thick fides towards their
middle, where the greateft forces are applied to in-
jure them ; while their hollownefs increafes their
diameter, and confequently their ftrength to refill:
forces applied to break them tranfverfely (a). Thus,
for inftance, in eflimating the proportional refiftance
of two cylindrical bones of unequal diameters, but
confifting of an equal number of fimilar fibres uni-
formly difpofed round each, it is plain,

1. That the abfolute force of thefe two bones is
equal, becaule they confift of equal numbers of fimi~
lar fibres.

2. That the abfolute forces of all the fibres in
each bone have the fame efie<fl in refilling any power
applied to break them, as if the fum of all their forces
was united in the refpe&ive centres of the tranfverfe
fetlions where the fratlures are to be made. For, by
hypothefis, the fibres being uniformly difpoled in each,
there is not any fibre in either bone that has not a
correfponding fibre ; the fum of both whale ilillances
from the axis of revolution (about which all the parts
of the bone mull revolve in breaking), is equal to two
femidiameters of the bone: Confequently each fibre,
and all the fibres, may be regarded as refilling, at the
dillance of one femidiameter or radius from this axis,
that is, in the centre.

3. Since the united force of all the fibres is to be
regarded' as refilling at a diflance from the centre of
motion equal to the femidiameter, it follows, that

B 3 the:

(a) Galilei Mechanic, dialog. 3*

18 Of the BONES in GENERAL.

the total refinance of all thefe fibres, or the flrength
of the bone, is proportional to its femidiameter, and
confequently to its diameter.

I have here taken for an example one of the molt
fimple cafes for calculating the proportional forces of
bones. But, was it not too foreign to the prefent
defign, it might be univerfally demonflrated, that, of
whatever figure bones are, and in whatever manner
their fibres are difpofed, their flrength muft always
be in a ratio, compounded of the area of their tranf-
verfe feflions, or of their quantity of bony matter,
and of the diftance of the centre of gravity of thefe
f?£lions from the centre of motion or fulcrum, on
which the bone is fuppofed to be broken (a).

Since therefore the flrength of bones depends on
their number of fibres, or quantity of matter, and
the largencfs of their diameters, one may conclude,
that the part of a bone formerly fratlured, and re-
united by a callus, mull be flronger than it was be-
fore the fra&ure happened •, becaufe both thefe ad-
vantages are obtained by a callus ; which is a wife
provision, fince bones are never fet in fuch a good
direction as they were naturally of ; and then, where-
ever a callus is formed, there is fuch an obftru&ion
of the veffels, that if the bone was again brokeH in
the fame place, the oj/ific matter could not fo eafily be
conveyed to reunite it. This callus may indeed, for
want of comprefhon, be allowed to form into a
fpongv cellular fubflance (b) •, but even in this cafe,
the flrength of the bone is here increafed by one or
both the caufes above-mentioned.

Many bones have protuberances, or procejfes*, riling
out from them. If a proeefs Hands out in a roundilh
ball, it is called caput, or head. — If the head is flatted,
it obtains the appellation of condyle . — A rough unequal

protuberance,

(o) See the (lemon Oration ot this theorem by Dr Porterfield in
the Edinburgh Mcuical elTays, vol. I. art. io.

(£) Ruyfch. Thefaur. 8. n. 49- Muf. anat. thee. B. repofit. a. n. 2.

* Awofuirdf, (xyuTtif, irpotitKi, •arpofiMfia, Excetlus, ex-

planatio, tuberculum, gibbus, cnimcutia, produdtio, extuberantia,
projettura, cnalcentia.

r9

Of the BONES in GENER.AL.

protuberance, is called tuberofity. — When a prccefs
riles narrow, and then beomes large, the narrow or
fmall part is named cervix , or neck. — Long ridges of
bones, are called /pines. — Such procefles as terminate
in a lharp point, have the general name of cor once f,
or coronoid , bellowed on them, though moll of them
receive particular names from the refemblance they
have, or are imagined to have, to other fubllances,
e. g. majloid, flyloid, anchoroid , coracoid , fpinaly &c. —
Such procefles as form brims of cavities, are called
fupercilia (a).

Procefles ferve for the advantageous origin and in-
fertion of mufcles, and render the articulations firm
and liable.

Before leaving this fubje£l, we mull remark, that
much the greater number of what are called procefles
in adult bones, difcover themfelvcs in children to be
epiphyfes , or diflindl bones, which are afterwards
united to the other parts ; fuch are the Jlylcid procef-
fes of the temporal bones, procefles of the vertebra,
trochanters of the thigh, &c. However, as I defigs*
to infill chiefly on the defcription of the adult fkele-
ton, in which the union of thefe parts is fo intimate,
that fcarce any vellige remains of their former fepa-
ration, I lhall retain the common appellation of apo -
phyfe, or procefs, to all fuch protuberances ; but fhall
remark the principal ones, that have no juft title to
this name, when they occur in the defcription of
particular bones.

On the furfaces of a great many of the bones there
are cavities, or depreflions : If thefe are deep, with
large brims, authors name them cotylce [h). — If they
are fuperficial, they obtain the defignation of glena,
or glenoid. Thefe general clajfes are again divided
into fbveral fpecies : — Of which pits are fmall round-
ilh channels funk perpendicularly into the bone ; —
furrows are long narrow canals, formed in the fur-
face; — nitchesy oinotcheSy fmall breaches in the bone;— -

fmuofitieSy

t Roftra, glandes.

(a) Ttui f, ofpvtc, u/uQovti, x«\», Labra.

{b) K oTvhtitf, Acetabula, pixides, buccellx.

to Of the BONES in GENERAL.

fmiiofities, broad, but fuperficial depreflions without
brims foffee, large deep cavities, which are not e-
qually furrounded by high brims \—finufes, large ca-
vities within the fubftance of the bones, with fmall
apertures ; — - foramina , or holes, canals that pierce
quite through the fubftance of the bones. — When
this laft fort of cavity is extended any long way with-
in a bone, the middle part retains the name of canal,
and its ends are called holes.

The cavities allow the heads of bones to play in
them •, they lodge and defend other parts ; they af-
ford fafe paflage to vellels, mufcles, &c. To mention
more, would engage us too much in the hiftory of
particular bones, which more properly belongs to the
demonftration of the fkeleton, where we fhall have
occafion to obferve thefe feveral fpecies of cavities.

To far the greater number of bones, whofe ends
are not joined to other bones by an immoveable arti-
culation, there are fmaller ones annexed, which af-
terwards become fcarce diftinguiftiable from the fub-
. ftance of the bone itfelf. Thefe are called epiphyfes,
or appendices ( c ). Some bones have one, others have
two, three, or four of thefe appendices annexed, by the
means of cartilages, which are of a confiderable
thicknefs in children, but by age become thinner ;
the offilication proceeding from the end of the bone
on one fide, and from the epiphyfes on, the other, till
at laft, in adults, the place of their conjunction can
fcarcely be feen on the external furface •, and it is on-
ly fometimes that we can then fee any mark of di-
ItinCtion in the cancelli (d).

Several procefles (e. g. trochanters of the thigh,
fpine of the /cupula, £*)V.) have epiphyfes ; and procef-
fes frequently rife out from epiphyfes ; for example, at
the lower end of the femur , ulna , tibia, &c. (ef.

The epiphyfes are united chiefly to fuch bones as are
deftined for frequent and violent motion ; and for

this

(c) Applantatio, additamentum, adnafeentia, adnexum, perone.

' (</) Window Expofition anatomique de corps hunlain, traitc. des.

os fees, § n6.

(f) Yeial, i>c human, corp. fabrics, lib, I. cap. 3,

Of the BONES in GENERAL. 21

this purpofe they are wifely framed of a larger dia-
meter than the bone they belong to ; for by this
means, the furface of contact between the two bones
of any articulation being increafed, their conjunction
becomes firmer, and the mufcles inferted into them
atf with greater force, by reafon of their axes being
further removed from the centre of motion. Thefe
advantages might indeed have been obtained by the
expanfion of the end of the bone itfelf, to a thick-
nefs equal to that of the epiphyfes ; but then the con-
flant feparation of new plates to form fo wide a cel-
lular ftru&ure, muft have left the folid fides of the
bones fo thin, as to yield eafily, either to the action
of the mufcles fixed to them, and palling over them,
to the weight feveral of them are obliged to fupport,
or to the application of any other external force.

Several anatomifts (f) thought that the epiphyfes
ferve other purpofes : fuch as, fecuring the ligaments
of the articulations which rife out from between the
bones and them ; for, as foon as thefe parts are inti-
mately jcined, the ligaments infinuated betwixt them
muft have a much ftronger connexion than they
could have to the fmooth furface of the bones. Such
an interception of the ligament between the body of
the bone and its epipkyfe is not to be feen ; but as, at
this place, the bone remains longer foft than any
.where elfe, and the adhefion of the periojleum , and
of ligaments to bones, is always ftronger in propor-
tion to the bones being neareft to the confidence of
thofe parts, which is, being lbfteft, the opinion of
thefe writers concerning the ftronger connexion of
the ligaments, where the bones and epiphyfes join, is
not without fome foundation.

Poffibly, too, by the fibres of epiphyfes not extend-
ing themfelves fo longitudinally as thofe of the bones,
there may be lefs chance of the former running into
.each other, than of the latter.

The

(f) Collumb. De re anatomica, lib. r. cap. J. — Fallcp. Expel.
<*e oflibus, cap. 11.

22 Of the BONES in GENERAL.

The foftnefs of .the ends of bones may be of fome
advantage in the womb, and at birth, after which
the oflification begins at different points to form epi-
phyfes , before the oflification can extend from the
middle to the ends of the bones (g).

However folid and compaft adult bones are, yet
they were once cartilages, membranes', nay, a mere
jelly. This needs no further proof, than repeated
obfervations of embryos when differed : And how
much more tender muff the bones be before that
time, when neither knife nor eye is capable to dif-
cover the lead rudiments of them ? By degrees they
become more folid, then aflume the nature of griflles,
and at lad oflify ; the cohefion of their plates and
fibres always increafing in proportion, to their increaf-
ed folidities ; as is evident from the time neceffary
to unravel the texture of bones of people of different
ages, or of denfe and of fpongy bones, or of the dif-
ferent parts of the fame bone, and from the more
tedious exfoliations of the bones of adults than of
children.

After any part of a bone is fully odified, its fibres
are extended little more in length at that part,
though they increafe there in thicknefs, and though
their fofter parts continue to become longer ( h ).

As the folidity of bones increafes, their periojleum
more eafily feparates from them. When bones are
membranous, the periojleum and they cannot be di-
flinguifhed ; thev appear to be the fame fubdance.
"When they are cartilages, their membrane adhere fo
firmly to them, that it is difficult to feparate it from
them. Where the rigid bony fibres are, the periojle-
um is eafdy taken off. Is the fimilarity of drutture
and confequent greater attra£lion of the membrane
and fubdance it inclofes, while they are both flexible,
the caufe of their greater adhefion ? or is it owing to
the velTels that go from the one to the other be-
ing

(g) Haller de Audio medic, p. 267.

(h) Hales’s Vegetable ftatics, p. 293. — Da Hamel Mcmoires <ic
t'acad. dcsfciences, 174a.

Of the BONES in GENERAL. 23

ing then larger ? or do both thefe caufes combine to
produce this efleft? Oris the membrane or cartilage,
which becomes bone afterwards, to be confidered as
the fame fubftance with the periojieum (t) ? and mufl
all thefe plates of bones be therefore faid to be
layers of the periojletim hardened ( k ) ?

The oflification of bones depends principally on
their veflels being fo difpofed, and of fuch diameters,
as to feparate a liquor, which may eafily turn into a
bony fubftance, when it is deprived of its thinner
parts; as feems plain from the obfervation of the cal-
lous matter feparated after fra&ures and ulcers, where
pait of the bone is taken out : For in thefe cafes, the
veflels extending themfelves, and the liquors added
to them, are gradually formed into granulated flefli ;
which fills up all the fpace where the bone is taken
from, then hardens, till it becomes as firm as any
other part of the bone. This happens frequently,
even when the ends of the difeafed bone are at a
confiderable diftance from each other (/).

The induration of bones is alfo greatly aflifted by
their being expofed, more than any other parts, to the
ftrong prefl'ure of the great weights they fupport, to
the violent contra&ion of the mufcles fixed to them,
and to the force of the parts they contain, which en-
deavour to make way for their own further growth.
By all this prefling force, the folid fibres and veflels
of bones are thruft clofer ; and fuch particles of the
fluids conveyed in thefe veflels as are fit to be united
to the fibres, are fooner and more firmly incorporat-
ed with them, while the remaining fluids are forcibly
driven out by the veins, to be mixed with the mafs
of blood. In confequcnce of this, the veflels gradu-
ally diminifh as the bones harden. From which a-
gain we can underftand one reaion, why the bones of
young animals fooner reunite after a fra&ure than

thofe

(i) Memoires de l’acad. des fcienees, 1 744.

(f) Memoires de l’acad. des fcienees, 1743.

CO Hildan. de vuln. jravif. — Med. eflays, vol. I. art. 23. — Job a
Mcckren obf. 69. — Mem. de l’acad. des fcienees, 1742.— Sec a col*
leftion of fuch cafes in Bochmcr de odium callo,

?4 Of the BONES in GENERAL.

thofe of old, and why cattle that are put too foon to
hard labour feldom are of fuch large fize as others of
the fame brood who are longer kept from labour.

That the oflifying of bones greatly depends on
preflure, feems to be evinced from the frequent ex-
amples we meet with of other parts turning bony,
when long expofed to the prefling force of the fur-
rounding parts, or when they are fubjetted to the
like circumfiances by their own frequent and violent
contra&ion. Witnefs, the bones found frequently
near the bafe of the heart in fome old men (>»), and
in Several other creatures. Nay, the mufcular fub-
flance of the heart has been oflified in fuch («), and
the arteries of old men often become bony. — The
cartilages of the larynx are generally oflified in ad-'
lilts. — In beafts of burden, the cartilages between
the vertebra of the back very often change into com-
plete bones •, and, being intimately united with the
vertebra, the whole appears one continued bone : —
Nor is the periojleum exempted from -fuch an indura-
tion [o).

To confirm this argument flill farther, we may
obferve, that bones begin their offification at the
places where they are moft expofed to thefe caufes,
viz. in the cylindrical bones from a middle ring,
and in the broad ones, at or near their centre, from
one or more diftindb points. The reafon of which
is, that thefe parts are contiguous to the bellies of
the mufcles annexed to the bones, where the dwel-
ling of thefe moving powers is greatefl:. What the
effe&s of this may be, let any judge, who view fome
of the bones, as the fcapula , and ojfa ilium , which are
covered with mufcles on each fide j how compact
and thin they are in adults, where the bellies of the
mufcles were lodged', whereas in children they are
thicker. But this being the middle part of thefe

bones,

(») Riolan. Comment, de oflib. cap. 3a. — Bartholin. Hi ft. med.
cent. 1. hilt. 50. — Ibid. cent. a. hilt. 45.

(») Chefelden’s Anatomy, book I. introd. — Garengeot Hitt, de
1'aoad. des fciences, I7a6.

(0) Peycr. Ephcmerid. German, dccur. 2. anil. 7. obferv. 20J.

Of the BONES in GENERAL. 25

bones, where the greateft number of fibres is, this
particular place would have been much thicker in
adults, had not this forcible caufe been applied,
which has not had luch effe&s in children, whofe
mufcles have not been much exercifed. — Befides, if
we allow that all the parts of a bone are equally in-
creafed by the conftant fupply of new particles, each
fibre, and every particle of a fibre, endeavours to
make way for its own growth, by pufliing the one
next to it •, aiid confequently by far the greateft pref-
fure is on the middle, to make the particles firm, and
therefore to begin their ofiification there. Lafily , The
pulfation of the medullary arteries, which enter the
bones near to this middle part, may, as authors have al-
ledged, contribute perhaps fomewhat to this induration.

From the effe£ls of prelfure only it is, that we can
account for the bones of old people having their
fides much thinner, yet more denfe and folid, while
the cavities are much larger than in thofe of young
people ; and for the prints of mufcles, vefiels, 5sV.
being fo much more ftrongly marked on the furfaces
of the former than of the latter, if they belong to
people of near the fame condition in life. — Prelfure
mull likewife be the caufe which, in people of equal
ages, makes thefe prints ftronger in the bones of thofe
wrho had much labour and exercife, than they are in
people who have led an indolent inactive life.

Perhaps both the caules of ofiification above men-
tioned, may be aflifted by the nature of the climate
people live in, and the food they ufe. Whence, in
hot countries, the inhabitants fooner come to their
height of ftature than in the northerly cold regions :
And thence feems to have arifen the common prac-
tice among the ladies, of making puppies drink
brandy or fpirit of wine, and of bathing them in
thefe liquors, to prevent their growing big. Nay, it
has been obferved, that much ufe of fuch fpirits has
occafioned parts, naturally foft, to petrify in fome,
and to oflify in other people of no great age (/>).

C From

{p) Littre Hiftoire de l’acad. des fcienccs, 1706.— Geoffroy Me-
moires dc Vacad. des fcienccs, 1706.

2 6 Of the BONES in GENERAL.

From the foregoing account of the ftrufture of
bones, and of their ofiification, we may underftand
the reafons of the following phenomena.

How the natural colour of bones may be changed
by fome forts of food ( q ).

Why the bones of fome people are fo long in har-
dening, and in others never completely indurate.

Why, in fuch whofe ofiification is flow, the bones
are generally thicker in proportion to their lengths,
efpecially at their ends ; as in the rickets.

How hard firm bones have become foft and pliable
by difeafes (r).

Why in fome difeafes, epiphyfes feparate from
bones (s), and the ends of frattured bones come afun-
der many years after their fradlures appeared to be
cured (r).

How bones may wafle and diminifh -(//).

How bones may become folid all through, without
any appearance or cancetli (at).

How nodes , tophi , and exojiofes , happen after the e-
rofion of the external plates of bones in the lues ve-
nerea,/curvy, rheumatifm, and gout.

How bones exfoliate by the rifing of granulated
flefh from their furface.

How, and from what callus is formed after a frac-
ture (y).

Philofoph. Tranfaft. Num. 44*- art. 8. Num. 443. art. 3.
Num. 457. art. 4.— Mem de l’acad. des fciences, 1739. I74i-

(r) Hiftoire de l’acad. des fcienccs, X700. — Mem. 1722.— Gagli-
ardi Anat. odium; cap. 2. obfcrv. 3. — Ephcm. Germ, decur. 1.
ann. I. obf. 37. et fchol. decur. 2. anil. 7. obf. 212, 235. decur. 3.
ann. 2. obf. 3. — Philof. Tranf. Num. 470. § 3. — Ibid. vol. 40. § 4»
and 44*

(j) Mcmoires de l’acad. des fciences, 1699.— Diemerbroek Anat.
lib. 9. cap. 19. — Cowper’s Anat. explic. tab. 96. fig. I.

(/) Anfon’s Voyage.

(a) Chefclden’s Anat. book I. introd. — Hift. de l’acad. des fciences,

J\x) Ruyfch. Thefaur. 2. nrc. 5. thef. 3. loc. I. Num. 5. thef. 9.
Num. 2. not. 3. — Boehmer de callo odium.

(y) Mcmoires de I'acad. des fgitnccs, 1741.— Delitlcef dc ofliiun
callo.

Of the BONES in GENERAL. 27

Why callus appears to be rather the continued fub-
fiance of the periofleum than of the bone, while it
remains foft and flexible ; but feems continued witb
the bone after it oflifies (2).

Why callus is fenfible, while it is foft, but becomes
infenfible when it hardens.

What occafions fometimes fuch difficulty in cur-
ing fractured bones ; or why they never reunite,
though they are reduced, and all proper means to-
wards a cure are ufed (a). — Are the bones of women
with child more tedious in reuniting than thofe of o-
ther people ( b ) ?

Why callufcsy after fra&ures, are fometimes very
thick and protuberant.

What difference there ought to be in the applica-
tion of bandages to fractures of the bones of old and
of young patients.

How bones, remaining long unreduced after a
luxation, may have their form fo changed as to make
their reduction very difficult, if not impoffible (r).

Whoever is defirous to know, in what time and or-
der each bone and its feveral parts begin to afl'ume a
bony nature, let him confult Kerckingius (<f), who
gives us the delineations of abortions from three
days after conception, and traces the offification of
the bones from three weeks, and a month, till the
time of the birth : To whom fhould be added Coite-
rus ( e ) and EyJJonius ( f )• An account of this fub-
je£t might alfo be collected out of Ruyfch’s works,
where 1'ome of the miftakes committed by the for-
mer authors are corrected : And feveral more parti-
. C 2 culars,

(z) Mem. de l’acad. 1 741.

(a) Meckren Obferv. medico-chimrg. obf. 71. — Ruyicb. Advert*,
dec. 2. § 2. oblerv. anat. chir. obi'. 4. — Van Swieten in Boerhaave
Aphor. § 354.

(b) Hitdan. centur. 5. obf. 87. et cent. 6. obf. 68.— Philof. Tranf.
No. 494- § 41.

(0 Saltzman. Obf. dccur. obf. 6. — Memoires de l’acad. dc cbirur.
tom. 2. p. 1 55. Bochiner Inftit. ofteolog. § 596.

(d) Anthropograph. ichnograph. et olteogenea fee tutus.

(0 De dflibus ftetus atiortivi.

(f) De oflibub infant, ccgnofcend. et curand.

28 Of the. BONES in GENERAL.

culars, to make the hiftory of the ojleogenea more ac-
curate, have fince been added by Nejbit ( g ) and Al-
bmus (h).

I muft refer to the authors now quoted for the
more curious part of the human ofteogeny ; not
having preparations enough to give fuch a full hiftory
of it as is done by them. But I {hall endeavour to
explain the more ufeful and neceflary part of the
ofteogeny, by fubjoining to the defcription of each
hone of an adult, its condition in ripe children ; that
is, in fuch as are born at the ordinary time j and
{ball point out what parts of each are afterwards
joined in form of epiphyfes. This, with the following
general rules, feem to me fufficient for underftand-
ing what of this fubjedt is neceflary in the pradtice of
phy lie and furgery.

1. Wherever I mention any parts being cartila-
ginous, or their being (till feparabie from the other
parts of the bone to which they belong, I would be
underftood to hint, that, about feven or eight years
of age, fuch parts arc oflified and united to their pro-
per bones, unlefs when it is faid, that they are after-
wards formed into epiphyfes.

2. Such as become epiphyfes, are generally oftified
at feven or eight years of age ■, but, being for the,
moft part moiftened by fynovia , their external furface
is ftill fomewbat cartilaginous, and they are not yet
united to their bones.

3. At eighteen or twenty years of age the epiphyfes
arc entirely oflified, and have blended their fibres fo
with the body of the bone, as to make them infepa-
jrable without violence.

The knowledge of this part of the ojltogeny I think
neceflary, to prevent dangerous miftakes in the cure
of feveral difeafes. As for example: Without this
knowledge, the reparation of an epiphyfc might be
miftaken for a firadture or luxation. — The interftice of
two parts of a bone not yet joined, might be judged

to

(g) Human Ofteogeny explained.

\h) leones oflium foetus humani ; acccdit oftcogenece brevis liifto-
ria.

Of the B O N E S in G E N E R A L. 29

to be a A fl u re. — A diaflafis , or reparation of fuch ciif-
joined pieces of a bone, might be thought a fra&ure.
— The protrufion of one piece, or its overlopping
any other, could be miftaken for an excrefcence or
exojlofis. — Such errors about the nature of a difeafe
would give one very different indications of cure,
from what he would have, if he really underftood
his patient’s cafe. And very often the knowledge of
the different inequalities on the furfaces of bones,
muft dire£t us in the execution of what is proper to
be done to cure feveral of their difeafes.

Having thus confldered the bones when Angle, we
ought next to fhew the different manner of their con-
jun£tions f. To exprefs thefe, anatomifls have con-
trived a great number of technical terms ; about the
meaning, propriety, and clafling of which, there has
unluckily been variety of opinions. Some of thefe
terms it is neceflary to retain, Ance they ferve to ex-
prefs the various circum fiances of the articulations,
and to underftand the writers on this fubjeft.

The Articulations are moft commonly divid-
ed into three claffes, viz. fytnphyftSy fynarthrojis , and
diarthrofts.

Symphyfts , which properly Agnifles the concretion
or growing together of parts, when ufed to exprefs
the articulations of bones, does not feem to compre-
hend, under the meanihg generally given to it, any
thing relating to the form or motion of the conjoined
bones ; but by it moft authors only denote the bones
to be connc&ed by fome other fubflance •, and as there
are different fubftances which ferve this purpofe,
therefore they divide it into the three following
fpecies :

1. Synchondrofis when a cartilage is the connec-
ting fubflance : Thus the ribs are joined'to the Jltr-
twm ; thus the bodies of the vertebra are counseled
to each other j as are likewife the ojfa pubis.

C 3 2. Sytmeurc/tSf

t trvvicmi, e-u^/3oxJi, o/xi \ia, compofitio, conncxio,

articulatio, conjur.dtio, nodus, coramillura, (tiuctura, compares.

i Arophiarthrofis,

30 Of the BONES in GENERAL.

2. Synneurofs , or fyndefmefts , when ligaments are
the connecting bodies, as they are in all the moveable
articulations.

3. SyJJareo/is, when mufcles are flretched from one
bone to another, as they muft be where there are
moveable joints.

The fecond clafs of articulations, the fynarthrofs t
which is faid to be the general term by which the
immoveable conjunction of bones is exprefled, is di-
vided into three kinds.

1. The future f is that articulation where two
bones are mutually indented into each other, or as if
they were l'ewed together, and is formed by the fibres
of two bones meeting while they are yet flexible and
vielding, and have not come to their full extent of
growth ; fo that they mutually force into the inter-
llices of each other, till, meeting with fuch refiftance
as they are not able to overcome, they are flopped
from fprouting out farther, or a;e reflected ; and
therefore thefe indentations are very different both in
figure and magnitude : Thus the bones of the head
are joined ; thus cpiphyfes are joined to the bones, be-
fore their full connexion and union with them.

Under this title of future , the hannoma of the an-
cients may be comprehended •, fcarce any unmoved
bones being joined by plain furfaces (a).

2. Gomphofts f is the fixing one bone into another,
as a nail is fixed in a board : Thus the teeth are fe-
cured in their fockets.

3. Shitidylefis or ploughing (d), when a thin lamella
of one bone is received into a long narrow furrow of
another : Thus the proceffus azygos of the fphenoid, and
the nal'al procefs of the ethmoid bone, are received by
the vomer.

The third clafs, or diarthrofis (b), is the articula-
tion where the bones are fo loofely connected as to al-
low

f 'p it*.

(a) Vefal. Obfcrv. Fallop. Exatncn.

} Conclavatio.

( d) Kt-U Anat. chap 5. feft. 3.

(J>) Axtcpfyuns, dearticulatio, abarticulatio.

Of THfe BONES in GENERAL. 31

low large motion. This is fubdivided into three kinds.

The firft is enarthrojis, or the ball and focket, when
a large head is received into a deep cavity ; as the
head of the os femor'ts is into the acetabulum coxendicis.

The fecond is arthrodia , when a round head is re-
ceived into a fuperficial cavity ; as in the articulation
of the arm-bone and fcapula . Thefe two fpccies of
diarthrojts allow motion to all fides.

The third is ginglimus (c), which properly fignifies
the hinge of a door or window ; in it the parts of the
bones mutually receive and are received, and allow
of motion two ways : Workmen call it churned.

The ging/imus is generally divided into three kinds,
to which fome (d) give the names of contiguous («•),
dijlant (f)i and compound (g).

The firft kind of ginglimus is, when a bone has fe-
veral protuberances and cavities, which anfwer to as
many cavities and proceflcs of the other bone, with
which it is articnlated : as in the conjunction of the
femur with the tibia.

The fecond fpecies is, when a bone receives ano-
ther at one end, and is received by the fame bone at
the other end •, as in the radius and ulna.

The laft fort is, when a bone receives another, and
is received by a third ; as in the oblique proceflts of
the vertebrae.

When I firft mentioned the articulations of bones,
I faid there were different opinions concerning the
ufe of their technical names; e. g. It has been faid,
that fymphyfts fhould be the name for the immoveable
articulations, and fynarthrofs fhould be underllood to
be the conjunction of bones by fome connecting me-
dium— Thofe who have taken fympkfis in the fenfe I
did, of its exprefling the conjunction of bones with
a connecting fubftance, have difagrecd in their defi-
nition of it ; fome inferting, and others leaving out,

its

(f) Articulatio mutua.

(d) Baker Curf. oftcolog. demonftr. I.

(f) Proximus.

(f) Longus.

Cj) Compofitus.

3*2 Of the BONES in GENERAL.

its allowing motion. — "Where they have agreed in
their definition, they have not been of the fame mind
concerning the fpecies of it. For feveral think the
Syffdrcoftsznd. fytidefmofts applicable to fo many joints
which are univerfally allowed to be clalTed under the
diarthreftSy that it mud create confufion to name them
by any fpecies of the fymphyfts. — Few keep to fuch a
general definition of the fynchondro/is as 1 have done ;
and, whether they determine it to allow no motion,
or an obfcure or a manifeft one, bring themfelves in-
to difficulties, becaufe there are examples of all thefe
three kinds. — Some again, by too nicely diftinguiffi-
ing obfcure and manifeft motions of bones, have
blended ihtfynnrthrofis and diarthrofis y and from thence
have branched out the different compound fpecies of
articulations that may be formed of them, fo far, that
they could find no examples in the body to illuftrate
them by. — It would be tedious to enumerate more of
the jarring opinions, and it would be far more fo to
give a detail of the arguments ufed by the difputants.
It is fufficient for my purpofe, rhat it is underftood
in what fenfe I take thefe technical terms ; which I
do in the following manner :

When I mention the fymphyJJs or fynarthrofis, or
any fpecies of them, I fhall always uuderftand them ac-
cording to the explication already given of them. But
though the preceding account of the diarthrofisy or
articulation of moveable bones, has been almoft uni-
verfally received; yet, feeing it does not comprehend
all the moveable articulations of the body, and one
of its fpecies does not anfwer to any notion we can
have ot the conjunction of two bones, I muft beg
leave to change the definitions and kinds of thefe
joints. 4

I would call diarthrnfis that conjunction of bones,
whereby they are fitted tor motion, being- each co-
vered with a fmooth cartilage, connected by one or
more common ligaments, and lubricated with liquor
at the conjoined parts. In which definition, I hare
no regard to the quantity of motion which they real-

Of the B 0 N E S in G E NER A L. 33

ly do perform ; the motion being often confined or
enlarged by fome other caufe not immediately depen-
ding on the frame of the two furfaces of the bones
forming the particular joint which then is confidered.

The firft fpecies of the diarthrofis, viz. the enar-
throfis , or ball and foclcet, I would define more gene-
rally than above, That articulation where a round
head of one bone is received into a cavity of ano-
ther, and confequently, without fome foreign impedi-
ment, is capable of motion to all fides. Examples of
this kind are to be feen in the articulation of the thigh-
bone and offa innominata ; arm-bone and fcapula ;
aflragalus and os naviculare ; magnum of the wrift,
with the fcaphoides and lunare ; firft bone of the thumb
with the fecond, &c.

The fecond fort, or the arthrodia, differing from
the enarthrojis , in the preceding account, only in the
cavity’s being more fuperficial, which makes no ef-
fential difference, efpecially that, in the recent fub-
je£t, cartilages or ligaments fupply the deficiency of
bone, ought, in my opinion, to be called with Vefa -
lius (a), that articulation of two bones adapted for
motion, where it is not at firft fight obvious which of
the two has the head or cavity, or where they are
joined by plain furfaces, or nearly fo ; fuch is the
conjunction of the clavicle with the fcapula ; offa cunei -
for mi a with the os naviculare; metatarfal bones with
the offa cuneiformia, &c. From the nature of thi3
fort of joint, it is plain, that very great motion cannot
be allowed, without the bones going farther out of
their natural fituation, than is convenient or i'afe.

Ginglimi/s, 1 would reckon that articulation by the
form ol which the motion of the joined bones muft
be chiefly confined to two directions, which hinges
of doors are.

The firft fpecies of this is the trochoides, when one
bone turns on another, as a wheel does on its axis :
rJ hus the fiilt vertebra of the neck moves on the

tooths

00 De corp. human, fabrics, lib. I. cap. 4.

34 Of the BONES in GENER AL.

tooth-like procefs of the fecond. This is the moft
proper kind of ginglimus.

The fecond fpecies fhould be efteemed that articu-
lation where feveral prominent and hollow furfaces of
two hones move on each other, within the fame com-
mon ligament; as in the knee, elbow, &c.

The third fort of ginglimus is, when two bones are
articulated to each other at different parts, with a
diftind: apparatus of the motory machines at each ;
fuch is the articulation of the os occipitis with the firft;
vertebra of the neck ; of any two contiguous vertebra ,
by their oblique procefles ; of the ribs with the bo-
dies and traofverfe procefles of the vertebra ; of the ra-
dius with the ulna, tibia with the fibula , ajlragalus
with the calcaneum , fsV.

I would entirely throw out what is commonly
called the third kind of ginglimus : For, in examining
the conjunction of a bone with two others, as in the
common example of a vertebra joined with the one a-
bove and below, the connection of the middle one
with each of the other two ought to be confidered fe-
parately ; otherwife we might with the fame proprie-
ty efteem the articulations that the long bones, the
femur , tibia , humerus , CsV. have at their different
ends, as one articulation ; which is abfurd.

If the moveable bones are not connected and kept
firm by fome itrong fubftance, they would be lux-
ated at every motion of the joints : and if their hard,
rough unequal furfaces were to play on each other,
their motion would not only be difficult, but the lofs
of fubftance from attrition would be great. There-
fore ligaments are made to obviate the firft, and carti-
lages to prevent the other inconveniency. But be-
caufe ligaments and cartilages turn rigid, inflexible,
and rough, unlefs they are kept moift, a fufficient
quantity of proper liquors is fupplied for their lubri-
cation, and to preferve them in a flexible ftate. Seeing
then thefe parts are fo neceflary to the articulations,
I fhall next conftder their ftruCfture, fituation, and

ufes,

Of the BONES in GENERAL. 35

tifes, fo far as they are fubfervient to the bones, and
their motions.

Ligaments (a) are white flexible bodies, thick-
er and firmer than membranes, and not fo hard or
firm as cartilages, without any remarkable cavity in
their fubflance, difficultly ftretcbed, and with little
elafticity ; ferving to connett one part to another, or
to prevent the parts to which they are fixed from
being removed out of that fituation which is ufeful
and fafe.

After maceration in water, the ligaments can ea-
fily be divided •, and each ligamentous layer appears
compofed of fibres, the largeft of which are difpofed
in a longitudinal direction.

The arteries of ligaments are very confpicuous af-
ter a tolerable injeftion, and the larger trunks of .
their veins are fometimes to be feen full of blood.

Such ligaments as form the fides of cavities, have
numerous orifices of their arteries opening upon their
internal furface, which keep it always moift : If we
rub off that moifture, and then prefs the ligament,
we can fee the liquor oozing out from fmall pores ;
and we can force thin liquors inje£led by the arteries
into the cavities formed by ligaments.

Thefe exhalent arteries mull have correfponding
abfoibent veins , otherwife the cavities w ould foon be
too full of liquor.

Ligaments then muft be fubjeft to the difeafes
common to other parts, where there is a circulation
of fluids, allowance always being made for the fize
of veffels, nature of the fluids, and firmnefs of the
texture of each part.

Authors generally fay, that ligaments are infenfi-
hle : and conlequently it may be inferred, that they
have no nerves bellowed on them. But the violent
racking_pain felt on the lead motion of a joint la-
bouring under a rheumatifm , the feat of which difeafe
feems often to be in the ligaments, and the infuflerable
torture occafioned by incifions of ligaments, and by

a col-

(*) copulse, vinculai

36 Of the BONES in GEN ER AL.

a colleCHon of acrid matter in a joint, or by tophi in
the gout, would perfuade us, that they are abundant-
ly fupplied with nerves.

The ligaments which conneCt the moveable bones
commonly rife from the conjunction of the epiphyfis of
the one bone, and are inferted into the fame place of
the other •, or where epiphyfes are not, they come out
from the cervix, and beyond the fupercilia of the ar-
ticulated bones ; and after fuch a manner, in both
cafes, as to include the articulation in a purfe or bag,
with this difference, depending on their different mo-
tions, that where the motion is only to be in two di-
rections, the ligaments are ftrongeft on thofe Tides
towards which the bones are not moved ; and when
a great variety of motions is defigned to be allowed,
the ligaments are weaker than in the former fort of
articulations, and are nearly of the fame ftrength all
round.

Part of the capfular ligaments is compofed of the
periojleutn, continued from one bone to another, as
was obferved p. 2. and their internal layer is conti-
nued on the parts of the bone or cartilage which the
ligament includes ( a ).

Befides thefe common capfular ligaments of the
joints, there are particular ones in feveral places,
either for the firmer connection of the articulated
bones, or for reftraining and confining the motion to
fome one fide; fuch are the crofs and lateral ligaments
of the knee, the round one of the thigh, &C.

From this account of the ligaments, we may con-
clude, that, cateris paribus, in whatever articulation
the ligaments are few, long, and weak, the motion
is more free and quick ; but luxations happen fre-
quently : And, on the contrary, where the ligaments
are numerous, fhort, and ftrong, the motion is more
confined ; but fuch a joint is lefs expofed to luxations
(£). — Whence we may judge how neceffary it is to
attend to the different ligaments, and the changes

which

(d) Nefbit Ofleogen. — Philof. tranfaA. No. 470. feet 6.

( b ) Fabric, ab. Aquapcnd. 4c articul. part, utilit. pars 3.

0* the BONES in GENERAL. 37

which have been made on them by a luxation, when
it is to be reduced.

Ligaments alfo fupplf the place of bones in feveral
cafes to advantage : Thus the parts in the pelvis are

more fafely fupported below by ligaments than tney
could have been by bone. — The ligaments placed in
the great holes of the offa innominata , and between
the bones of the fore-arm and leg, afford convenient
origin to mufcles. — Immoveable bones are firmly con-
verted by them; of which the conjunction of the
os facrum and inmminatum is an example. — They
afford a focket for moveable bones to play in, as we
fee part of the ajlragalus does on the ligament ftretch-
ed from the heel-bone to the fcaphoid.

Numerous inconveniencic- may arife from too long
or (liort, flrong or weak, lax or rigid ligaments.

Cartilages * are foiid, fmooth, white, elafiic
fubftances, between the haidnefs of bones and liga-
ments, and covered with a membrane, named peri-
chondrium, which is of the fame flructure and ufe to
them as the periajieum is to the bones.

Cartilages are compofed of plates, which are form-
ed of fibres, difpofed much in the fame way as
thofe of bones are; as might be reafonably concluded,
from obferving bones in a cartilaginous ftate before
they oflify, and from feeing, on the other hand, fo
many cartilages become bony. This may be dill
further confirmed by the exfoliation which cartilages
are fubjeCf to as well as bones.

The perichondrium of. feveral cartilages, for exam-
ple, thofe of the ribs and larynx , has arteries which
can be equally well injected with thofe of the peri-
ojleum ; but the veffels of that membrane in other
parts, e. g. the articular cartilages, are fmaller, and
in none of them does injection enter deep into the
fubflance of the cartilages ; nay, madder, mixed with
the food of animals, does not change the colour of
cartilages as it does that of bones (a).

D The

* XovJ 'pat,

(a) Philof. Tranfaft. No. 442. art. 8. No. 443. art. 3. No. 457.
art. 4.— Mem. tie l'acad. dcs fences, 1739 ct 174*.— Dditlccf Jc
■0 ilium c:llo.

38 Of the BONES xn GENERAL.

The granulated flc(h which rifes from the ends of
metacarpal or metatarfal bones, when the cartilage
exfoliates, after a finger or toe has been taken off at
the firfl joint, is very fenfible, from which the ex-
iftence of nerves in cartilages may be inferred.

While cartilages are in a natural ftate, it is to be
remarked, firjl , That they have no cavity in their
middle for marrow. Secondly, That their outer fur-
face is fofteft, which renders them more flexible.
Thirdly , That they do not appear to change their
texture near fo much by acids as bones do. And,
laJHy , That as the fpecific gravity of cartilages is near
a third lefs than that of bones ; fo the cohefion of
their feveral plates is not fo ftrong as in bones ;
whence cartilages laid bare in wounds or ulcers, are
not only more liable to corrupt, but exfoliate much
fooner than bones do.

Cartilages feem to be principally kept from offifying,
either by being fubje&ed to alternate motions of flexion
and extenfion, the effe&s of which are very different
from any kind of Ample preffure, or by being con-
ftantly moiftened (a); Thus, the cartilages on the
articulated ends of the great bones of the limbs, and
the moveable ones placed between the moving bones
in fome articulations, which are obliged to fuffer
many and different flexions, and are plentifully moift-
ened, fcarce ever change into bone ; while thofe of
the ribs and larynx are often oflified. — The middle
angular part of the cartilages of the ribs, which is
conftantly in an alternate (fate of flexion and exten-
fion, by being moved in refpiration, is always the lad
of becoming bony. — In the larynx , the epiglottis, which
is oftener bended and more moiftened than the other
four cartilages, fcldom is oflified, while the others as
feldom efcape it in adults.

The cartilages fubfervient to bones, are fometimes
found on the ends of bones which are joined to no
other ; but are never wanting on the ends, and in the
cavities of fuch bones as are defigned for motion ( b ).

Cartilages

(<j) Havers Ofteolog. nov.

Celf, de rc medic, lib, 8, cap. r.

Of the BONES in GENERAL. 391

Cartilages alfo are interpofed between fuch other car-
tilages as cover the heads and cavities of articulated
bones; nay, they are alfo placed between immoveable

bones.

The ufes of cartilages, fo far as they regard bones,,
are, to allow, by their fmoothnefs, fuch bones as are
defigned for motion, to Hide eafily without detrition,
while, by their flexibility, they accommodate them-
felves to the feveral figures neceffary in different mo-
tions, and, by their elafticity, they recover their na-
tural pofition and fhape as foon as the preffure is re-
moved.— This fpringy force may alio affift the motion
of the joint to be more expeditious, and may render
fhocks in running, jumping, &c. lefs. — To thefe
cartilages we chiefly owe the fecurity of the moveable
articulations : For without them, the bony fibres would
fprout out, and intimately coalefce with the adjoin-
ing bone ; whence a true anchylojts muft necefl’arily^
follow ; which never fails to happen when the carti-
lages are eroded by acrid matter, or oflified from want
of motion or defeat of liquor, as we fee often hap-
pens after wounds of the joints, paidarthrocace , fcro-
J>hulay and fpina ventofa} or from old age, and long
immobility of joints (a) ■ — Hence we may know what
the annihilation is which is faid to be made of the
head of a bone, and of the cavity for lodging it, af-
ter an unreduced frafture (b). The moveable carti-
lages interpofed in joints, ferve to make the motions
both freer and more fafe than they would otherwife
be. — 1 hofe placed on the ends of bones that are not
articulated, as on the J pine of the os ilium , bafe of
the fcapula , &c. ferve to prevent the bony fibres from
growing out too far. — Cartilages fometimes ferve as
ligaments, either to faften together bones that are
immoveably joined, fuch are the cartilages between
the osfacrum and ojfa ilfum, the ojfa pubisi &c. or to

2 connect

(a) Columb. de re anat. lib. 15.— Deflaades Hid. de I'acad. des^
fcicnces, 1716. — Phil, traalaft. No. 215. — Ibid. No. 461. § 16.

(b) Hildas, de ichor, et mclicer. acri Celfi, cap. 5.— Ruyfch,
Tihef. 8. No. 103. — Salesman in aft. Pctropolit. tom. 3. p. 275,

40 Of the BONES in GENERAL.

connect bones that enjoy manifeft motion, as thole-
do which are placed between the bodies of the true
vertebra, &c. — Cartilages very often do the office of
bones to greater advantage than thefc laft could, as.
in the cartilages of the ribs, thofe which fupply brims
to cavities, fsV.

Too great thicknefs or thinnefs, length or fhort-
nefs, hardnefs or fupplenefs of cartilages, may there*
fore caufe great diforders in the body.

The liquor, which principally ferves to moifteir the
ligaments and cartilages of the articulations, is lup-
plied by glands, which are commonly fituated in the
joint, after fuch a manner as to be gently preffed,
but not deflroyed by its motion. By this means,
•when there is the greateft neceffity for this liquor,
that is, when the molt frequent motions are perform-
ed, the greateft quantity of it mult be feparated.
Thefc glands are foft and pappy, but not friable: In
fome of the large joints they are of the conglomerate
kind, or a great number of fmall glandules are wrapt
up in one common membrane. Their excretory
du£ts arc long, and hang loofe, like fo many fringes,,
•within the articulation; which, by its motion and
prefTure, prevents obllrudlions in the body of the
gland or its excretories, and promotes the return of
this liquor, when fit to be taken up by the abforbent
velfels, which muft be in the joints, as well as in
the other cavities of the body ; and, at the fame time,
the prefTure on the excretory du£ts hinders a fuper-
fluous unnecefl'ary fecretion, while the fimbriated dif-
pofition of thefe excretories does not allow any of
the fecreted liquor to be pufhed back again by thefe
canals towards the glands (r).

Very often thefe fountains of flimy liquor appear
only as a net-work of vefl'ds. — Frequently they are
almoft concealed by cellular membranes containing,
the fat — and fometimes fmall fimple mucous follicu/i
may be feen (d).

The

(c) Cowpcr Anat. explicat. tab. 79. lit. E. E.

(dj Morgaga. Advcrfar. 2. animad. 23,

41

Of the BONES in GENERAL.

The different joints have thefe organs in different
numbers and fizes; the conglomerate ones do not
vary much, efpecially as to fituation, in the (imilar
joints of different bodies but the others are more
uncertain.

Upon preffing any of thefe glands with the finger,
one can l'queeze out of their excretories a mucilagi-
nous liquor, which fomewhat refembles the white of
on egg, or feritm of the blood ; but it is manifeftly
fait to the tafte. It does not coagulate by acids, or
by heat, as the ferum does, but by the latter turns,
firft thinner, and, when evaporated, leaves only a
thin fait film.

The quantity of this mucilage conftantly fupplied,.
muff be very confiderable, fince we fee what a plen-
tiful troublefome difcharge of glary matter follows a ,
wound or ulcer of any joint ; of which liquor the
mucilage is a confiderable part.

The veffels which fupply liquors for making the
fecretion of this mucilage, and the veins which bring
back the blood remaining after the fecretion, are to
be feen without any preparation ; and, after a tole-
rable injection of the arteries, the glands are cover-
ed with them.

In a found- date, we are not confcious of any fen-
fibility in thofe glands ; but,: in fome cafes which I
have feen, when they inflame and fuppurate, the molt
racking pain is felt in them : a melancholy, though,
a fure proof that they have nerves.

Thefe mucilaginous glands are commonly lodged
in a cellular fubdance ; which is alio to be obferved
in other parts of the bag formed by the ligaments of
the articulation ; and contains a fatty matter, that
mud necefl'arily be attenuated, and forced through
the including memhranes into the cavity of the joint,
by the prefl'ure which it fuffers from the moving
bones.

If then the oil is conveyed from this cellular fub-
llanceand if the attenuated marrow paffts from the
sancelli of the bones by the large pores near their

D 3, ends„

42 Of riTE BONES in GENERAL.

ends, or in their cavities, and fweats through the
cartilages there into the articulations; which it may,
when a (lifted by the conftant heat and a&ion of the
body, more eafily do, than when it efcapes through
the compact fubftance of the bones in a fkeleton : If,
I fay, this oil is fent to a joint, and is incorporated
with the mucilage, and with the fine lymph that is
conftantly oozing out at the extremities of the fmall
arteries diflributed to the ligaments, one of the fitted
liniments imaginable mud be produced ; for the mu-
cus diluted by the lymph, contributes greatly to its
lubricity, and the oil preferves it from hardening.
How well fuch a mixture ferves the purpofe it is de-
figned for, Boyle ( e ) tells us he experienced in work-
ing his air-pump; for the fucker could be moved
with much lefs force after being moiftened with wa-
ter and oil, than when he ufed either one or other of
thefe liquors : And I believe every one, at firft view,
will allow the diluted mucilage to be much preferable
to fimple water. The fynovia (f), as this liquor com-
pofed of oil, mucilage, and lymph, is commonly
now called, while in a found date, effeftually pre-
ferves all the parts concerned in the articulations foft
and flexible, and makes them Aide eafily on each o*
iher, by which their mutual detrition and overheat-
ing is prevented, in the manner daily pradlifed in
coach and cart wheels, by befmearing them with
greafe and tar.

After the liquor of the articulations becomes too
thin and unferviceable, by being conftantly pounded
and rubbed between the moving bones, it is reaflum-
ed into the mafs of blood by the abforbent vefiels.

When the fynovia is not rubbed betwixt the bones,
it infpiflates. And fometimes, when the head of
a bone has been long out of its cavity, this liquor is
faid to fill up the place of the bone, and hinder its
reduction ; or if a joint continues long unmoved, it
is alfo faid to cement the bones, and occafion a true

anchylofts .

( e ) Phyfico-mechanic. experim.

(fj MvJ*, mucus, axungia.

Of the BONES in GENERAL. 43.

anchylofts (g). — If the fyrnvia becomes too acrid, it e-
rodes the cartilages and bones \ as frequently happens-
to thofe who labour under the lues venerea , /curvy, ,
fcrophula , or fpina ventofa.— If this liquor is leparated
in too fmall quantity, the joint becomes ftifF; and
when with difficulty it is moved, a crackling noife is.
heard, as people advanced in years frequently expe-
rience (A).— If the mucilage and lymph are depofited.
in too great quantity, and the abforbent veffiels do not
perform their office fufficiently, they may occafion a
dropfy of the joints (i). — From this fame caufe alfo
the ligaments are often fo much relaxed, as to make
the conjunction of the bones very weak : Thence a-
rife the luxations from an internal caufe, which are
eafily reduced, but difficultly cured (*).— Frequent-
ly, when fuch a fuperfluous quantity of this liquor is
pent up, it becomes very acrid, and occafions a great
train of bad fymptoms fuch as fwelling and pain of
the joints, long finuous ulcers, and fiftulx, rotten
bones, immobility of the joints, marcor and atrophia
of the whole body, heCtic fevers* bV. (/). — From a
depravity in the blood, or difeafes in the organs that
furniffi the fyrnvia of the joints, it may be greatly
changed from its natural ftate; it may be purulent
after inflammation, mucous in the white fwelling,
gelatinous in the rheumatifm, chalky from the gout,
bV. ; hence a great variety of diforders in the

joints ( m ),

THE

(g) Pare Chirurgie, lirre Ig. chap. 1 8. et livre 16. chap. 5.

(/;) Galen de ufu part. lib. I a. cap. a. — Fabric, ab Aquapend. de
1 articul. part, utilitat. pars 3. — Bartholin. Hift. medic, cent. 3. hift. II.
(i) Hildan. de ichore et meliceria acri Cclfi.

(k) Hippocrat. de locis in homine, § 14. et de articul*

(/) Hildan. de ichore et meliceria acri Cclfi.

(/«) See Reimar, Didert. de fungo articulor.

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THE

M Y

A N A T O

OF THE

HUMAN BONES.

PART II.

Of the SKELETON.

THOUGH any dry fubftance may be called
Jkeleton, yet, among anatomifls, this word is
universally underftood to fignify the bones of
animals connefted together, after the teguments,
mufcles, bowels, glands, nerves, and vefl'els are taken
away (a).

A fkeleton is faid to be a natural one, when the
bones are kept together by their own ligaments ; and
it is called artificial, when the bones are joined with
wire, or any other fubftance which is not part of the
creature to which they belonged. Small fubjefls,
and fuch whole bones are not fully oflified, are com-
monly prepared the firlt way ; becaufe, were all their
parts divided, the niceft artift could not rejoin them,
by rcafon of their fmallnefs, and of the feparation of
their unolTified parts j whereas the bones of large adr*
ult animals are foonelt and moll conveniently clean-
ed when fingle, and are eafily reftored to, and kept
in their natural fituation. — Sometimes the lkele$on

of

{a\ Cadavcris crates.

4<5 Of the SKELETON".

of the fame animal is prepared in both thefe ways ;
that is, the fmaller bones are kept together by their
natural ligaments, and the larger ones are connected
by wires, or fome fuch fubftances.

Before we proceed to the divifion and particular
defcription of the fkeleton, it is worth while to re-
mark, that when the bones are put into their natural
fituation, fcarce any of them is placed in a perpen-
dicular bearing to another ; though the fabric com-
pofed of them is fo contrived, that, in an ereCk po-
flure, a perpeivdicular line, from their common centre
of gravity, falls in the middle of their common
bafe ( b ). On this account, we can fupport ourfelves
as firmly, as if the axis of all the bones had been a
ftraight line perpendicular to the horizon •, and we
have much greater quicknefs, eafe, and llrength, in
feveral of the moft neceffary motions we perform.
It is true, indeed, that where-ever the bones, on
which any part of our body is fuftained, decline, from
a ftraight line, the force required in the mufcles, to
counteract the gravity of that part, is greater than,
otherwife it needed to have been : But then this is
effectually provided for in fuch places by the number
and ftrength of the mufcles. So long therefore as
•we remain in the fame pofture, a confiderable num-
ber of mufcles muft be in a conftant ftate of contrac-
tion; which, we know, both from reafon and expe-
rience, muft foon create an uneafy fenfation. This
we call, being weary of one pofture : An inconveni-
ence that we fhould not have had in Handing ereCt,
if the bearing of all the bones to each other had been
perpendicular; but is more than compenfated by the
advantages above mentioned.

The human fkeleton is generally divided into the
Head, the Trunk, the Superior, and the In-
ferior Extremities.

Of

(J) Cowpcr's Aaat of human bodies, cxplic. of tab. 87, 88.

Of the SKELETON.

47

Of the HEAD.

BY the HEAD, is meant all that fpheroidal part
which is placed above the firft bone of the neck.
It therefore comprehends the cranium and bones of
the face.

The cranium (c), helmet, or brain-cafe, confifts of
feveral pieces, which form a vaulted cavity, for lodg-
ing and defending the brain and cerebellum , with
their membranes, veffels, and nerves.

The cavity of the cranium is proportioned to its
contents.1- Hence fuch a variety of its Gze is obferv-
ed in different fubjeOs •, and hence it is neither fo
broad nor fo deep at its fore-part, in which the an-
terior lobes of the brain are lodged, as it is behind,
where the large poflerior lobes of the brain, and the
whole cerebellum , are contained.

The roundifh figure of the fkull, which makes it
more capacious, and better able to defend its con-
tents from external injuries, is chiefly owing to the
equal preffure of thefe contained parts as they grow
and increafe before it is entirely offfied. — It is to be
obferved, however, that the fides of the cranium are
depreffed below a fpherical furface by the ftrong tem-
poral mufcles, whofe a£lion hinders here the uniform
protrufion of the bones, which is more equally perform-
ed in other parts, where no fuch large mufcles are.
In children, whofe mufcles have not adled much, and
confequently have not had great effefts on the bones,
this depreffion is not fo remarkable ; and therefore
their heads are much rounder than in adults. Thefe
natural caufes, differently difpofed in different peo-
ple, produce a great variety in the fhapes of fkulls,
which is flill increafed by the different management
of the heads of children when very young : So that
one may know a Turk* s fkull by its globular figure, a
German’s by its breadth and flatnefs of the occiput ,

Dutch

(0 hvtoc, cruapioy, calva, calvaria, cerebri galea,

! theca et oUa capitis, tefta capitis, icutella capitis.

Of the SKELETON.

Dutch and E>igli/b by their oblong fhapes, &c. ( d ).
Two advantages are reaped from this flatnefs of the
Tides of the cranium , viz. the enlargement of our
fphere of vifion, and more advantageous fituation of
our ears, for receiving a greater quantity of found,
and for being lefs expofed to injuries.

The external furface of the upper part of the cra-
nium is very fmooth, and equal, being only covered
with the periojleum , (common to all the bones ; but
in the fkull, diftinguifhed by the name of pericra-
niumJ, the thin frontal and occipital mufcles, their
tendinous apotieurofs, and with the common tegu-
ments of the body ; while the external furface of its
lower part has numerous rifings, deprefhons, and
holes, which afford convenient origin and infertion
to the mufcles that are connected to it, and allow
fafe paffage for the veffels and nerves that run through
and near it.

The internal furface of the upper part of the fkull
is commonly fmooth, except where the veffels of the
dura mater have made furrows in it, while the bones
were foft. — Surgeons fhould be cautious when they
trepan here, lelt, in Tawing or raifing the bone
where fuch furrows are, they wound thefe veffels.—
In the upper part of the internal furface of feveral
fkulls, there are likewife pits of different magnitudes
and figures, which feem to be formed, by fome parts
of the brain being more luxuriant and prominent
than others. Where thefe pits arc, the fkull is fo
much thinner than any where elfe, that it is often
rendered diaphanous, the two tables being clofely
compacted without a diploe ; the want of which is
fupplied by veffels going from the dura mater into a
great many fmall holes obfervable in the pits. Thefe
veffels are larger, and much more confpicuous than
any others that are fent from the dura mater to the
fkull ; as evidently appears from the drops of blood
they pour out, when the fkull is raifed from the dura
mater in a recent fubjeft ; and therefore they may

furnifh

(4) Vcfal. lib. 1. c.J.

49

Of the SKELETON.

furnifh a fuflicient quantity of liquors neceuary to
prevent the brittlenefs of this thin pait. — The know-
ledge of thefe pits fhould teach furgeons to faw cau-
tioully and llowly through the external table of the
fkull, when they are performing the operation of the
trepan s fince, in a patient whofe cranium has thefe
pits, the dura mater and brain may be injured, be-
fore the inftrument has pierced near the ordinary
thickneis of a table of the fkull. — The internal bafe
of the fkull is extremely unequal, for lodging the fe-
veral parts and appendices of the brain and cerebellum ,
and allowing paflage and defence to the veflels and
nerves that go into, or come out from thefe parts.

The bones of the cranium are compofed of two
tables, and intermediate cancelli , commonly call-
ed their diploe (e). The external table is thickefl ;
the inner, from its thinnefs and confequent brittle-
nefs, has got the name of vitnea. Whence we may
fee the reafon of thofe mifehievous confequences
which fo often attend a collection of matter in the
diploe , either from an external or internal caufe, be-
fore any fign of fuch a collection appears in the te-
guments that cover the part of the fkull where it is
lodged {/).

The diploe has much the fame texture and ufes in
the fkull, as the cancelli have in other bones.

The diploe of feveral old fubiects is fo obliterated,
that fcarce any veftige of it can be feen ; neither is
it obfervable in fome of the hard craggy bones at the
bafe of the fkull. Hence an ufeful caution to fur-
geons who trufl to the bleeding, want of reft fiance,
and change of found, as certain marks in the opera-
tion of the trepan, for knowing when their inflru-
ment has fawed through the firil table, and reached
the diploe (g). In other people, the diploe becomes
of a monftrou5 tbicknefs, while the tables of the
lkull are thinner than paper.

E The

(#) Mcditullium, commiflura.

CfJ Bonct. Sepulchret. anat. lib. I. § I. obC 96.— IOJ-

(g) Bartholin, Anat, reform, lib. 4. cap, 4,

50

Of the SKELETON.

The cranium confifts of eight bones, fix of which
are faid to be proper, and the other two are reckoned
common to it and to the face. — — The fix proper are,
the os frontis, two ojfa parietctlia , .two ojfa temporum,
and the os occipitis. — The common are the os ethmoides
and fphen aides.

The os frontis forms the whole fore part of- the
vault ; the two ojfa parietalia form the upper and
middle part of it; the ojfa temporum , compofe the
lower part of the fides; the os occipitis makes the
whole hinder part, and fome of the bafe ; the os eth-
vnidcs is placed in the fore part of the bafe, and the
os fphenoides is in the middle of it.

Thefe bones are joined to each other by five futures ;
the names of which are, the coronal , lambdoid,Jaggit-
tal , and two fquamous.

The coronal (h) future is extended over the head,
from within an inch or fo of the external canthus of
one eye, to the like diftance from the other; which
being near the place where the ancients wore their
vitt.r, corona, or garlands, this future has hence got
its name. — Though the indentations of this future
are confpicuous in its upper part, yet an inch or
more of its end on each fide has none of them ; for
it is fquamous and fmooth there. ’

The Unr.bdoidal (i) future begins fome way below,
and farther back than the vertex or crown of the
head, whence its two legs are llretched obliquely
downwards, and to each fide, in form of the Greek
letter a, and are now generally faid to extend them-
felves to the bafe of the fkull ; but formerly anato-
mies (l) reckoned the proper lambdoid future to ter-
minate at the fquamous futures, and what is extended
at an angle down from that on each fide, where the
indentations are lefs confpicuoos than in the upper
part of the future, they called additamentum futura
lambdoidis (/).

’ This

( b ) XrtfancTa, arcualis, puppis.

(i) Lauda;, prora, hypfyloidcs.

(*) Vefal. Anat. Ub. I. cap. 6.

(/) Lamb4oi4« harmonialisj lamb4oi4cs inferior, occipitis corona.

Of the SKELETON. 51

This future is fometimes very irregular, being made
up of a great many fmall futures, which furround fo
many little bones that are generally larger and more
confpicuous on the external furface of the fkull, than
internally- Thefe bones are generally called tri-
quetra , or Wormiana; but fome other name ought to
be given them, for they are not always of a triangu-
lar figure ; and older anatomifls ( m ) than Olaus
Wormius (;/) have defcribed them. — The fpecific vir-
tue which thefe bones were once thought to have in
the cure of the epilepfy ( 0 ) is not now aferibed to
them ; and anatomifts generally agree, that their for-
mation is owing to a greater number of points than
ordinary of ofhfication in the fkull, or to the ordinary
bones pf the cranium not extending their ofhfication
far enough or foon enough ; in which cafe, the un-
offified interflice between fuch bones begins a feparate
ofhfication in one or more points : from which the
ofhfication is extended to form as many diflindf bones
as there were points that are indented into the large
ordinary bones, and into each other. — Probably thofe
children who have a largs opening in this place at

their birth, will have the largeft ojfa triquetra. To

confirm this account of the formation of thefe little
bones, we may remark, that fuch bones are fome-
times feen in other futures, as well as in the lamh~
doid. (/), and they are fometimes in one table of the
ficull, and not in the other (7.)

The JhgittaJ future (r) is placed longitudinally in
the middle of the upper part of the fkull, and com-
bi 2 monly

(m) Euftach. Odium examen. — Bauhin. Thcat. anat. lib. 3<
cap- 5- — Paaw in Hippocrat. de vulncr. cap. p. 56.

( n ) Mufatum, lib. 3. cap. 16.

(0) Bauhin. ct Paaw. ibid. — Baitholin.- Anat. reform, lib. 4.
cap. 5. — Hihlan. Epift. 65.

(/>) See E samples in Vcfol. lib. 1. cap. 6. fig. 4.— Paaw in Hip-i
pocrat. dc cap. vuln. — Bartholin. Hifl. anat. cent. I. hift. 51.—
Ruyfch. Muf. anat. — Sue Trad, d’ofteolog. p. 47.

(7) Ilunaul.l Me m. dc l’acad. des. (cicncts, 1730.

(r) ’Pa/Sd'ofiJ'nf, oCfAaia, (\tj£iu ywaa, Inftar virgse, ncrvaKs, inftar
tcli, inffar vei n, fccundum capitis loagitiuuucm proreperu, copiungcns,
cnlumnalis, retfa, acualis.

52

Of the SKELETON

monly terminates at the middle of the coro?ml, and of
the lambdoid futures; between which it is faid to be
placed, as an arrow is between the firing and bow. —
However, this future is frequently continued through
the middle of the os front is , down to the root of the
nofe ; which, fome (s) fay, oftener happens in women
than men ; but others ( 1 ) alledge, that it is to be
met with more frequently in male fkulls than in fe-
male : Among the flaills which I have feen thus di-
vided, the female are the mofl numerous. — Several
(u) have delineated and deferibed the fagittal future,
femetimes dividing the occipital bone as far down a3
the great hole through which the medulla fpinalis paf-
ies. This 1 never faw. "

In fome old fculls that are in my pofleflion, there
is fcarce a veflige of any of the three futures which I
have now deferibed. In other heads, one or two of
the futures only difappear ; but I never could difeo-
ver any reafon for thinking them difpofed in fueh dif-
ferent manners in fculls of different fhapes, as fome
ancients alledge they are (r/).

The / quamous agglutinations , or falfe futures (e), are
one on each fide, a little above the ear, of a femicir-
cular figure, formed by the ovcrlopping (like one fcale
upon another) of the upper part of the temporal bones
on the lower part of the parietal, where, in both
bones, there are a great many fmall rifings and fur-
rows, which are indented into each other; though
.thelc inequalities do not appear till the bones are fe*
parated- In fome fculls indeed the indentations here
are as confpicuous externally as in other futures (f) ;
and what is commonly called the pofterior part of this

t fquamoua

( s ) Riolan. Comment, dcortib cap. 8.

(/) Vefal. lib. i. cap. 6. et in epitome.

(;<) Vefal. lib. i. cap. j. fig 4. et in text. cap. 6. Paaw in

Celf. de re medic, cap. r. — Laurent.' Hid. anat. lib. 2. cap. 16.

(</) Hippocrat. de vulner. capitis, fe£t. I. — Galen de oflib. et de
ufu part.'lib. 9. cap. 17.

(e) AirHatHu, ■xfonoWnfjLxra,, Kporupixi, temporalcs, corticales,
mendofac, harmonialcs, commiflurse in uiiguem.

( f ) Columb. de re anat. lib. X. cap. 4.— Diouis Anat. 3. de-
moult, des os.

53

Of the SKELETON.

fquamous future, always has the evident ferrated
form ; and therefore is reckoned by fome (g ), a dif-
tin£t future, under the name of cidditamentutn pcjte-
rius futura fquamofte. — I have feen two fquamous fu-
tures on the fame temple, with a femicircular piece of
bone between them (h).

We ought here to remark, that the tiue fquamous
fort of future is not confined to the conjunction of
the temporal and parietal bones, but is made ule of
to join all the edges of the hones on which each tem-
poral mufcle is placed (/) : For the two parts of the
fphenoidal future which are continued from the ante-
rior end of the common fquamous future juft now
defcribed, of rvhich one runs perpendicularly down-
wards, and the other horizontally forwards, and alio
the lower part of the coronal future already taken no-
tice of, may all be juftly faid to pertain to the fqua-
mous future. — The manner how 1 imagine this fort of
future is formed at thefe places, is, That by the ac-
tion of the ftrong temporal mufcles on one fide, and
by the preflure of the brain on the other, the bones
are made fo thin, that they have not large enough
furfaces oppofed to each other to flop the extenfion of
their fibres in length, and thus to caufe the common
ferrated appearance of futures explained in p. 3c. but'
the narrow edge of the one bone Hides over the other.
The fquamous form is alfo more convenient here ; be-
caule iuch thin edges of bones, when accurately ap^
plied one to another, have fcarce any rough furface,
to obftruCt or hurt the mufclc in its contraction j
which is Rill further provided for, by the manner of
laying thefe edges on each' other ; for in viewing their
outfide, w£ fee the temporal bones covering the fphe--
noidal and parietal, and this laft fupporting the fphe-
noidal, while both mount on the ficntal : from which
difpofition it is evident, that while the temporal muf-
cle is contracting, which is the- only time it preffes

E 3 ftrongl^i

(S) Alhin.de cffib. fcft. 54.

(h) Sue r] tad. dVfteolog. p. 48.

(i) ,Vefal. Anat. lib. I. cap. 6. Window Mem. de 1’acad. des

Kiences, 1730.

54

Of the SKELETON.

ftrongly in its motion on the bones, its fibres Aide-
ealily over the external edges. Another advantage
ftill in this is, that all this bony part is made ftronger
by the bones thus fupporting each other.

The bones of the fcull are joined to thofe of the
face, by fckymlelefis and futures. — The fchyndelefts is in
the partition of the nofe. — The futures faid to be
common to the cranium and face are five, viz. the
ethmoidal , fphenoidal, tranfverfe , and two zygomatic. —

' Parts however of thefe futures are at the jun&ion of
only the bones of the fcull.

The ethmoidal and fphenoidal futures furround the
bones of thefe names ; and in fome places help to
make up other futures, particularly the fquamous and
tranfverfe \ and in other parts there is but one future
common to thefe two bones.

The tranfverfe future is extended quite crofs the
face, from the external canthus of one orbit to the
fame place of the other, by finkinc from the canthus
down the out fide of the orbit to its bottom \ then
mounting upon its infide, it is continued by the root
of the nofe down the internal part of theother orbit, and
rifes up again on its outfide to the other canthus. It
may be here remarked, that there are fome interrup-
tions of this future in the courfe I have deferibed ; for
the bones are not contiguous every where, but are
feparated, to leave holes and apertures, to be men-
tioned hereafter.

The zygomatic futures are one on each fide, being
fliort, and flaming from above obliquely downwards
and backwards, to join a procef9 of the cheek-bone
to one of the temporal bones, which advances towards
the face ; fo that the two procefles thus uiiited, form
a fort of bridge, or jugum, under which the temporal
mufcle pafles ; on which account the procefles, and
future joining them, have been called zygomatic.

It muff be obferved, that the indentations of the
futures do not appear on the infide of the cranium , by
much fo ftrong as on the outfide : but the bones
feem almoft joined in a llraight line ; nay, in fome

fculls.

Of the SKELETON. 55

fculls, the internal furface is found entire, while the
futures are manifeft without ; which may poflibly be
owing to the lefs extent of the concave than of the
convex furface of the cranium , whereby the fibres of
the internal fide would be ftretched farther out at the
edges of the bones, than the exterior ones, if they
were not refilled. The refinances are the fibres of
the oppofire bone, the parts within the fcull, and the
diplae ; of which the fall being the weakeft, the molt
advanced fibres or ferree run into it, and leave the
contiguous edges equal, and more ready to unite :
whereas the ferret of the external table have fpace e-
nough for their ad mi (lion between the fibres of the
oppofite bone, and therefore remain of the indented
form, and are lefs liable to the concretion, whereby the
futures are obliterated (a). — By this mechanifm, there
is no rifle of the Tharp points pf the bones growing
inwards, fince the external ferra of each of the con-
joined bones reft upon the internal fmooth edged table
of the other \ and external forces applied to thefe
parts are ftrongly refilled, becaufe the futures cannot
yield, unlefs the ferrated edges of the one bone, and
tjae plain internal plate of the other, are broken ( b ).

The advantages of the futures of the cranium are
thefe : 1. That this capfula is more eaGly formed and
extended into a lpherical figure, than if it had been
one continued bone. 2. That the bones which are
at fome diftance from each other at birth, might then
yield, and allow to the head a change of fhape, ac-
commodated to the paflage it is engaged in. "Whence,
in hard labour of child-bed, the bones of the cranium^
inflead of being only brought into cornadl, are fome-
times made to mount one upon the other. 3. It is
alledged, that, through the futures, there is a tran-
fpiration of fleams from the brain, which was the old
do6lrine •, or fome communication of the veffels with-
out, and of thofe within the fcull, larger here than
in any other part of the cranium , according to fome

moderns j

(-0 Hutiauld Memoires de 1’acad. des feienees, 1730.

(b) Window Memoires de I’acad. des feienees, 1720,

S<s Of the SKELETO N;

moderns; and therefore cucuphte, fomentations, cata-
plafms, cephalic plajlers , hlijhrs , are applied, and
ijfues are eroded, or cut in the head, at thofe places'
where the futures are longeft in forming, and where
the connexion of the bones is afterwards loofeft, for
the cure of a phfenitis , mania , inveterate headachy e-
pilep/y, apoplexy , and other difeafes of the head. The
favourers of the doctrine of tranfpiration, or commu-
nication of veftels at the futures, endeavour to fup-
port it by obfervations of perfons fubjeCt to headachs
which caufed death, from the futures being too clofe-
ly united (a). 4. That the dura mater may be more

firmly fdfpended by its procefles, which infinuate
themfelves into this conjunction of the bones ; for
doing this equally, and where the greateft neceffity
of adhefion is, the fu;« res are difpofed at nearly e-
qual diftan'ces, and the large refervoirs of blood, the
Jinufes, are under or near them. 5. That fradtures
might be prevented from reaching fo far as they
would in a continued bony fubftance. 6. That the
connection at the futures being capable of yielding,
the bones might be allowed to feparate ; which has
given great relief to patients from the violent fvmp-
toms which they had before this feparation happened
(d). And it feems reafonable to believe, that the o-
pening of the futures was of great benefit to feveral o-
thers w*ho were rather judged to have been hurt by it
(h) : for we muft think, that the confequences of fuch a
force aCting upon the brain, as was capable of thruft-
ing the bones afunder, muft have been fatal, unlefs
it had been thus yielded to.

Having gone through the general ftruCture of the
craniumt I now proceed to examine each bone of

which*

(a) Columb. de re an at; lib. I. cap. j. — Verduc. nouvelle ofteolo*-
gje, chap. 14.— Dionis Anat. 3. demonftr. des os.

( d ) Ephcmcrid. Germanic, dec. I. ann. 4. ct j. obfarv. 33.

( b ) Ephemerid. Germ dec. 2. ann. 9. obf. 230. Ibid cent. 10.
obf. 31. — Vandcr Linden Medicin. phyt; cap. 8. art. 4. § 16. —
Hildan. Oblerv. cent. X. obf. I. cent. 2. old. 7.---Bauhin, Tksat.
anat. lib. 3. cap. 6. — Mechlin. Obfcrv. lib. a. obferv. 39.

Of the SKELETON. 57

of which that brain-cafe confifts, in the order in
•which I firft named them.

The OS FRONTIS (c) has its name from its being
the only bone of that part of the face we call the fore-
heady though it reaches a good deal farther. It has
fome refemblance in fhape to the fhell of the concha
hevalvis, commonly called the cockle j for the greateft
part of it is convex externally, and concave internal-
ly, with a ferrated circular edge ; while the fmaller
part has procefles and depreffions, which make it of
an irregular figure.

The external furface of the os frontis is fmooth gt
its upper convex part ; but feveral procefles and cavi-
ties aie obfervable below: for, at each angle of each
orbit, the bone juts out, to form four procefles, two
interna], and as many external ; which, from this
fituation, may well enough be named angular. Be-
tween the internal and external angular procefles on
each fide, an arched ridge is extended, on which the
eye-brows are placed. Very little above the inter-

nal end of each of thefe fuperciliary ridges, a protube-
rance may be remarked, in moft fculls, where there
are large cavities, called finufesy within the bone ; of
which hereafter. — Betwixt the internal angular pro-
cefles, a fmall procefs rifes, which forms fome fhare

of the nofe, and thence is named nafdl. Some ob-

ferve a protuberant part on the edge of the bone be-
hind each external angular procefs, which they call

temporal procefles ; but thefe are inconfiderable.

From the under part of the fuperciliary ridges, the
frcHtal bone runs a great way backwards : which
parts may juftly enough be called orbitar procefles.
Thefe, contrary to the relt of this bone, are concave
externally, for receiving the globes of the eyes, with
their mufeles, fat, £sV.

In each of the orbitar procefles, behind the middle
of the fuperciliary ridges, a confidcrable finuofity is
obferved, where the glandula innominata Galeni or la-
, chrymalik

• (c) htirwru, ttr.lyuct, coronale, inverecundum, puppii, fenfus com-’
munis, tincipitis.

$3 Of the SKELETON.

chry malls is lodged. — Behind each internal angular
procefs, a fmall pit may be remarked, where the car-
tilaginous pully of the mufculus obliquus major of the
eye is fixed. — Betwixt the two orbitar procefles, there
is a large difeontinuation of the bone, into which the
cribriform part of the os ethmoides is incafed. — The
frontal bone frequently has little caverns formed in

it here where it is joined to the ethmoid bone.

Behind each external angular procefs, the furface of
the frontal bone is confiderably depreffed where part
of the temporal nuifcle is placed.

The foramina , or holes, obfervable on the external
furface of the frontal bone, are three in each fide. —
One in each fuperciliary ridge, a little removed from
its middle towards the nofe ; through which a twig of
the ophthalmic branch of the fifth pair of nerves pafi'es
out of the orbit, with a fmall artery from the inter-
nal carotid, to be diflributed to the teguments and
mufcles of the forehead. — Thefe veflels in lome fculls
make furrows in the osfrontis, efpecially in the bones
of children, as has alfo been obferved of another con-
fiderable veffel of this bone near its middle (a) ; and
therefore we ought to beware of tranfverfe incifions
on either fide of the os frontisi which might either
open thefe veflels or hurt the nerves, while they are
yet in part within the bone; for, when veflels are
thus wounded, it is difficult to flop the haemorrbagy,
becaufe the adhefion of a part of the artery to the
bone hinders its contra&ion, and confequently ftyptics
can have little effect ; the lides of the furrow keep off
compreffing fubltances from the artery ; and we would
wiffi to fhun cauteries or efcharorics, becaufe they
make the bone carious, and nerves, when thus hurt*
fometimes produce violent fymptoms. — But, to re-
turn to the fuperciliary foramina , we mull remark,
that often, inftead of a hole, a notch only is to be
feen : Nay, in fome fculls, fcarcc a veflige even of
this is left; in others, both hole and notch are ob-
fervable, when the nerve and ajtery run feparately.

Frequently

(a) Ruyfch. Muf. anat. theca D. rcpoGt. 4. No. 3.

Of the SKELETON. 59

Frequently a hole is found on one fide, and a notch
on the other; at other times we fee two holes; or
there is a common hole without, and two diftind
entries internally. The reafon of this variety of a
hole, notch, deprefiion, or fmoothnefs in the fuper-
ciliary ridge, is the different length and tenfion of
the nerves and veflels ; the (horter they are, the more
they are funk into the bone as it grows. — Near the
middle of the infide of each orbit, hard by, or in the
tranfverfe future , there is a fmall hole for the pafiage
of the nafal twig of the firfl branch of the fifth pair
of nerves, and of a branch of the ophthalmic artery.
This hole is fometimes entirely formed in the osfrontis ;
in other fculls, the Tides of it are compofed of this
laft bone, and of the os planum. It is com-
monly known by the name of orbitarium inter-
num,, though anterius fhould be added, becaufe of
tine next, which is commonly omitted. — This, which
may be called orbitarium internum pojltr'tus , is fuch
another as the former ; only fmaller, and about
an inch deeper in the orbit : through it a fmall
branch of the ocular artery pafles to the nofe. —
Befides thcfe fix, there are a great number of fmall
holes obfervable on the outer furface of this bone,
particularly in the two protuberances above the eye-
brows. Moll of thefe penetrate no further than the
JtnufeSj or than the diploe , if the finufes aie wanting;
though fometimes I have feen this bone fo perforated
by a vafi. number of thefe fmall holes, that, placed
between the eye and a clear light, it appeared like a
fieve. — In the orbit of the generality of Jkeletons , we
may obferve one, two, or more holes, which allow
a pafiage to a hog’s bridle through the fcull. The
place, fize, and number of thefe, are however un-
certain : They generally ferve for the tranfmiflion of
fmall arteries or nerves.

The internal furface of the os front is is concave,
except at the orbitar procefies, which are convex, to
fupport the anterior lobes of the brain. This furface
is not fo fmooth as the external ; for the larger branches

of

Go

Of the SKELETON.

of the arteries of the aura water make fome furrows
in its fules and hack parts. The finuofities froth the
luxuriant rifings of the brain, mentioned when de-
scribing the general ftru&ure of the cranium, are of-
ten very cbfervable on its upper part ; and its lower
and fore parts are marked with the contortions of the
anterior lobes of the brain. — Through the middle of
this internal furface, where always in children, and
Sometimes in old people, the bone is divided, either
a ridge Hands out, to which the upper edge of the
falx is faftened, or a furrow runs, in which the up-
per fide of the fuperior longitudinal ftnus is lodged ; on
both thefe accounts chirurgical authors juffly difcharge
the application of the trepan here. — The reafon of
this difference in fculls, is alledged by fome authors
to be this, That in thin fculls the ridge ftrength-
ens the bones, and in thick ones there is no occafion
for it. To this way of accounting for this phoeno-
menon, it may juftly be obje&ed, that generally very
thick fculls have a large fpine here, and frequently
thin ones have only a furrow. Perhaps this variety
may be owing to the different times of compleat of-
fification of thofe parts in different fubjecls ; for if the
two fules of this bone meet before they arrive at
their utmoff extent of growth, they unite very firm-
ly, and all their fibres endeavour to ftretch themfelves
out where the leaft refiftance is, that is, between the
hemifphercs of the brain. To lupport this reafoning,
we m^y remark, that thofe adults, whofe frontal bone
is divided by the fagittal future, never have a ridge in
this place.

Immediately at the root of this ridge or furrow,
there is a fmall hole, which fometimes pierces through
the firft table, and, in other fculls, opens into the
fuperior finus of the ethmoid bone within the nofe.
In it a little procefs of the falx is lodged, and a fmall
artery, and fometimes a vein, runs (a) ; and the fupe-
rior longitudinal finus begins here. — This hole, how-
ever, is often not entirely proper to the os frontis j for,

in

. (a) Morgagn. Advcrfar. 6. animad. jr.

Or THE SKELETON. 6t

ki feveral fculls, the lower part of it is formed in the
upper part of the bafe of the crijla galli, which is a
proeefs of the ethmoid bone (z).

The os frontis is convpofed of two tables, and an
intermediate diploe, as the other bones of the cranium
are, and in a middle degree of t'nicknefs between
the os occipitis and the parietal bones ; is pretty equal-
ly denfe all through, except at the orbitar proceffes,
where, by the adtion of the eye on one fide, and
prefTure of the lobes of the brain on the other, it is
made extremely thin and diaphanous, and the ntedi-
tullium is entirely obliterated. Since in this place
there is fo weak a defence for the brain, the rcafon
appears, why fencers elteem a pufli in the eye mor-
tal (a).

The diploe is alfo exhaufted in that part above the
eye-brows, where the two tables of the bone fepa-
rate, by the external being protruded outwards, to
form two large cavities called Jin as fr on tales. — Thefe
are divided by a middle perpendicular bony partition.
— Their capacities in the fame fubjeef are leldom e-
qual ; in fome the right, in others the left is largeft. —
And in different bones their fize is as inconffant;
nay, 1 have examined fome, where they were entire-
ly wanting; which oftener happens in fuch as have
a flat forehead, and whofe fagittal future is continu-
ed down to the nofe, than in others (h). — In fome
fculls, befldes the large perpendicular feptum , there
are feveral bony pillars, or (liort partitions, found in
each firms; in others thefe are wanting. — For the
moll part, the feptum is entire; at other times it is
difeontinued, and the two finufes communicate. —
When the Jinufes are feen in fuch fculls as have the
frontal bone divided by the fagittal future, the parti-
tion dividing thefe cavities is evidently compofed of
two plates, which eafily feparate. — Each firms com-

E monly

(;) IngialT. Comment, in Galen, de ofllb. cap. I. comment. 8.

(a) Ruyfch. Obferv. anat. chir. obferv. 54. — Diemerbroek Ana?,
lib. 3. cap. 10. — Bonct. Sepulch. anat. lib. 4. § 3. obferv. 17.

{!') 1; allop. Expofit. de ollibus, cap. 13.

6 2

Of the SKELETON.

monly opens by a roundiffi fmall hole, at the inner
and lower part of the internal angular procefles, uto
- a Jinus formed in the nofe, at the upper and b ok
part of the os unguis ; near to which there are aifo
lome other fmall ftmt/es of this bone (r), the great i •
part of which open feparately, nearer the feptum n. •
rium , and often they terminate in the fame commo;
canal with the large ones.

In a natural and found (late, t’ ' cavities are c r
confiderable advantage: for the organ of fmelling b; -
ing thus enlarged, the effluvia of odorous bodies mo.c
difficultly efcape it$ and their impreffions being more
numerous, are therefore ftronger, and affedl the or-
gan more. That odorous particles may be applied to
the membrane of the finufes , is evident from the pain
felt in this part of the forehead, when the effluvia of
volatile fpirits, or of llrong aromatics, are drawn up
into the nofe by a quick infpiration. — Th£fe and the
other cavities which open into the nofe, increafe the
found of our voice, and render it more melodious,
by ferving as fo many vaults to refound the notes. —
I Ience people labouring under a coryza, or ftoppage
of the nofe, from any other caufe, when they are by
the vulgar, though falfely, faid to lpeak through their
r.ofe, have fuch a difagreeable harffi voice. — The li-
quor feparated in the membrane of thefe (inufes, drills
down upon the membrane of the nofe to keep it
moift.

From the defcription of thefe finufes , it is evident,
how ufeleft, nay, how pernicious it mull be, to ap-
ply a trepan on this part of the fcull ; for this inltru-
ment, inllcad of piercing into the cavity of the cra-
nium, would reach no further than the finufes ; or, if
the inner table was perforated, any extravafated blood

• that happened to be within the fcull, would not be
difeharged outwardly, but would fall into the finufes ,
there to llagnate, corrupt, and ftimulate the fenfible
membranes ; from which alfo there would be fuch a
conflant flow of glary mucus, as would retard, if

not

(f) Cowper in Drake’s Ajothrqpolog. book 3. chap. 10,

Of the SKELETO N. 63

not hinder a cure, and would make the fore degene-
rate into an incurable fffula. Befides, as it would
be almoft impoflible in this cafe to prevent the air,
paiTing through the nofe, from having conftant accefs
-to the dura mater , or brain ; fucb a corruption would
bt biought on thefe parts as would be attended with
great danger. Further, in refpiration, the air ruffl-
ing violently into thefe cavities of the os frontis , and
pacing through the external orifice, whenever it was-
not v. *11 covered and defended, would not only pre-
vent che clofing up of the external orifice, but might
otherwife bring on bad confequences (d). — The mem-
brane lining thefe ftnufes is fo fenfible, that inflam-
mations of it mult create violent torture (e) •, and
worms, or other infects crawling there, mult give
great uneafinefs (f).

The upper circular part of the os frontis t is joined
to the ojj'a par iet allay from one temple to the other,
by the coronal future. From the termination of the
coronal future, to the external angular procefies, this
bone is connedted to the fphenoid by the fphenoidal fu-
ture. At the external canthi of the eyes, its angular
procefles are joined by the tranfverfe future to the
qffa malaruiriy to which it adheres one third down the
outfide of the orbits whence to the bottom of thefe
cavities, and a little up on their internal fides, thefe
orbitar procefles are connetted to the fphenoidal bone
by that fame future. — In fome few fculls, however,
a difcontinuation of thefe two bones appears at the
upper part of the long flit, near the bottom of the
orbit. — On the infide of each orbit, the orbitar pro-
cefs is indented between the cribriform part of the
ethmoid bone, and the os planum and unguis. — The
tranfverfe future afterwards joins the frontal bone to
the fuperior nafal procefTes of the offa maxillaria [upe-

F 2 rioretf

W Paaw <!e offibus, pars i. cap. 7.— Palfync Anat. ch:r. trait ' 4.
chap- 15- — Nouvelle oltco logic, partie 2. chap. 3,

(r ) Fernel. Puthalog. lib. 5. cap. 7. — Saltzman. Decur. obf. ia.

( l ) l'crncl. Pathclog. lib. 5. cap. 7. — Bartholin. Epiftol. nit lie,
ccat. 2. cpill. 74. — Hit!, dc l’acad. Ucs lcieaccs, & 1733.

64

Of the SKELETON.

flora, and to the nafa! bones. And, laf/\, its nafal
procefs is connected to the nafal lamella of the
ethmoid bone.

The frontal bone ferves to defend and fupport the
anterior lobes of the brain. It forms a considerable
part of the cavities that contain the globes of the
eyes, helps to make lip the feptum mriurn , organ of
fmelliug, fsV. From the description of the Several
parts, the other ufes of this bone are evident.

In a ripe child, the fjantal bone is divided through
the middle ; the fuperciliary holes are not formed ;
often a fmall round piece of each orbitar procefs, be-
hind the fuperciliary ridge, is not oflified, and there
is no finus to be feen within its fubftance.

Each of the two OSSA PARIETALIA (g), or
bones ferving as walls to the encephalon, is an irregu-
lar fquare •, its upper and fore fides being longer than
ihe one behind or below. The inferior fide is a con-
cave arch-, the middle part receiving the upper round

part of the temporal bone. The angle formed by

this tipper fide, and the fore one, is fo extended, as
to have the appearance of a procefs.

The external furface of each os parietale is convex.
Upon it, fomewhat below the middle height of the
bone, there is a tranfverfc arched ridge, of a whiter
colour generally than any other part of the bone \
from which, in bones that have flrong prints of
rmifclcs, we fee a great many converging furrows,
like fo many radii drawn from a circnai^wence to-
wards a centre. From this ridge -each bone the
temporal mufcle rifes ; and, by tVe preflure of its

fibres, oceafions the furrows juft now mentioned.

Below thefe, we obfeive near the femicircular edges,
a great many rifings and deprefiions, which are join-
ed to like inequalities on the infide of the temporal
bone, to form the fquamous future. The temporal
bone may therefore ferve here as a buttrefs, to pre-
vent

(£; Ko[.v pn;, paria, fyncipitis, vertiris, arcualia, nervalia, cojita-
tlonis, rationis, Jjregraatis, madefaftioais.

jOf the SKELETON. "6$

vent the lower fide of the parietal from ftarting out-
wards when its upper part is prefled or (truck (A).

Near the upper lides of thefe bones, towards the
hind part, is a fmaLl hole in each, through which a
vein pafles from the teguments of the head to the
longitudinal ftnus. Sometimes I have feen a branch
of the temporal artery pafs through this hole, to be
diftributed to the upper part of the falx , and to the
dura mater at its fides, where it had frequent anafto-
mofes with the branches of the arteries derived from
the external carotids, which commonly have the name
of the arteries of the dura mater , and with the
branches of the internal carotids which ferve the falx.
In feveral fculls, one of the ojfa parietalia has not this
hole : in others, there are two in one bone *, and in
fome not one in either. Moft frequently this hole is
through both tables; at other times the external table
is only perforated. — The knowledge of the courfe of
thefe veflels may be of ufe to furgeons, when they
make any incifion near this part of the head, left,
if the veflels are rathly cut near the hole, they fhrink
within the fubftance of the bone, and fo caufe an
obftinate haemorrhagy, which neither ligatures nor
medicines can flop.

On the inner concave furface of the parietal bones,-
we fee a great many deep furrow's, difpofed fomew hat
like the branches of trees : The furrow's are largeft
and deepeft at the lower edge of each os parietale>
efpecially near its anterior angle, where fometimes a
full canal is formed. They afterwards divide into
fmall furrows, in their progrefs upwards — In fome
fculls a large furrow begins at the hole neai the up-
per edge, and divides into branches, which join with
thofe which come upwards, fhew'ing the communica-
tions of the upper and lower veflels of the dura ma-
ter. — In thefe furrows we frequently fee paflages into
the diploc ; and fometimes I have obferved canals go-
ing off, which allowed a fmall "probe to pafs :e

F 3 inches

(J>) Hunauld Mem. de l’acad. dcs fciences, 1730.

66

Of the SKELETON.

inches into the bony fubftance Some ( i ) tell us*
that they have obferved thefe canals piercing the bone
towards the occiput. — On the infide of the upper edge
of the ojfa parietalia, there is a large finuofity, fre-
quently larger in the bone of one fide than of the o-
ther, where the upper part of the falx is fattened,
and the fuperior longitudinal ftnus is lodged. — Gene-
rally part of the latter finufcs makes a depreflion near
the angle, formed by the lower and pofterior fides of
thefe bones ; and the pits made by the prominent
parts of the brain are to be feen in. no part of the
fcull more frequent, or more confiderable, than in.
the internal furface of the parietal bones.

The ojfa parietalia are amongft the thinneft bones
of the cranium ; but enjoy the general ftru£ture of
two tables and diploe the complete!!, and are the mod
equal and fmooth.

Thefe bones are joined at their fore-fide to the os
frorrtis by the coronal future ; at their long inferior
angles, to the fphenoid bene , by part of the future of
this name ; at their lower edge, to the ojfa temporum,
by the fquamous future, and its pofterior additament-
am ; behind, to the os occipitis , or ojfa triquetra , by
the Jambdoid future j and above, to one another, by
the fagittal future.

They have no particular ufes befides thofe men-
tioned in the defeription of their feveral parts, except
what are included in the account of the general ttruc-
ture of the cranium.

In a child born at the full time, none of the fides
of this bone are completed ; and there never is a hole
in the ollified part of it near to the fagittal future.

The large unoffified ligamentous part of the crani-
um obfervable between the parietal bones, and the
middle of the divided os frontis of new-born children,
called by the vulgar the open of the h ad, was imagin-
ed by the ancients tc ferve for the evacuation of the
fuperfluous moifture of the brain ; and therefore they

named

(i) Cowpcr's Anatom, exp lie. of 90 tab. fig. 2.

Of the S K E L E T O N». 67

named it bregma (/), or the fountain ; fometimes add-
ing the epithet pulfatilis^ or beating, on account of
the pulfation of the brain felt through this flexible
ligamento-cartilaginous fubftance. Hence very fre-
quently the parietal bones are called ojfa bregmatis.

The upper middle part of the head of a child, in
a natural birth, being what prefents itfelf firft at the
os uteri ( m ), an accoucheur may reach the bregma
with his finger, when the os uteri is a little opened..
If the bregma is flretched, and the pulfation of the
brain is felt through it, the child is certainly alive
But if it is fhrivelled and flaccid, without any ob-
feivable pulfation in it, there is fome reafon to fufpe£t:
the child to be very weak, or dead. Thofe who prac-
tice midwifery fhould therefore examine the ftate of
the bregma accurately.

All the bregma is generally oflified before feven
years of age. Several authors ( n ) fay, they have ob-
served it unoffified in adults ; and phyficians, who
order the application of medicines at the meeting of
the coronal and fagittal futures, feem yet to think,
that a derivation of noxious humours from the ence-
phalon is more eafily procured at this part than any
other of the fcull * and that medicines have a greater
efiett here than elfcwhere, in the internal diforders
of the head.

OSSA TEMPORUM (0), fo named, fay authors,
from the hair’s firft becoming gray on the temples,
and thus difcovering peoples ages, are each of them
equal and fmooth above, with a very thin femicircu-
lar edge ; which, from the manner of its connection
with the neighbouring bones, is diftinguilhed by the

name of os J'quamoJum. Behind this the upper part

of

(/) Palpitans vertex, foliolum, folium, triangularis lacuna.

(m) Burton’s Midwifery, § j I Smellic’s Midwilery, book r,
chap. 1 § 5.

(«) Bartholin. Anat. reform, lib. 4. cap. 6 — Dicmerbroek Anat.
lib. 9. cap. 6. — Kerckring Ofteogen cap. a.

(0) KofTAji!», xopa-un, xop pav, Xt-riSn liti, rtWufn, \idonS», tem-
poralis, lapidofa, memiofa, dura, arcualia, tympanum, armalia, iaxea,
parietal!*,

68

Of the SKELETON.

of the temporal bone is thicker, and more unequal,
and is fometimes defcribed as a diftintt part, under
the name of pars mammillaris (p). — Towards the bafe
of the fcull, the temporal bone appears very irregu-
lar and unequal ; and this part, inflead of being
broad, and placed perpendicularly, as the others are,
is contracted into an oblong very hard fubltance, ex-
tended horizontally forwards and inwards, which in
its progrefs becomes fmaller, and is commonly called
os petrofum.

Three external procefles of each temporal bone are
generally defcribed. — The firft placed at the lower and'
hind part of the bone, from its refemblance to a nip-
ple, is called tnaftoides, or mammillaris . It is not fo-
] id, but within is compofed of cancelli , or fmall cells,
which have a communication with the large cavity of
the ear, the drum ; and therefore founds, being mul-
tiplied in this vaulted labyrinth, are increafed, before
they are applied to the immediate organ of hearing.
Into the maftoid procefs, the JlenomaJloideus mufcle is
inferted ; and to its back part, where the furface is
rough, the trachelomajloideus , and part of the fplenius
are fixed. — About an inch farther forward, the fecond
procefs begins to rife out from the bone ; and having
its origin continued obliquely downwards and for-
wards for fome way, it becomes fmaller ; and is
ftretched forwards to join with the os mala-, they to-
gether forming the bony jugum, under which the
temporal mufcle pafies. Hence this procefs has been
named zygomatic (a). Its upper edge has the ftrong'
aponeurolis of the temporal mufcle fixed into it; and
its lower part gives rife to a fhare of the majfeter. —
The fore part of the bafe of this procefs is an oblong
tubercle, which in a recent fubjeft is covered with a
fmooth polilhed cartilage, continued from that which
lines the cavity immediately behind this tubercle —
From the under craggy part of the os temporum, the

third

(p) Alhin. de oflib. fe£t. 26.

(a) Kuyr.po(, pans, anlac oflium temporum, ofla arcualia, paria,.
jugalia, conjugalia.

Of the SKELETON. 69

third prooefs ftands out obliquely forwards. The
fhape of it is generally faid to refemble the ancient
Jlylos fcriptorius ; and therefore it is called the Jlyloid
"procefs (b). Some authors ( c ) however contend, that
it ought to be named Jleloid , from its being more like
to a pillar. Several mufcles have their origin from
this procefs, and borrow one half of their name from
it ; as Jlylo-gloJJhs, Jlylo-hyoideus, Jly/o-pharyngeus ; to it
a ligament of the os hyoides is fometimes fixed ; and ano-
ther is extended from it to the infide of the angle of
the lower jaw. This procefs is often, even in adults,
not entirely offified, but is ligamentous at its root,
and fometimes is compofed of two or three diftincfc

pieces. R.ound the root of it, efpecially at the

fore-part, there is a remarkable rifing of the os peiro-
funty which fome have efteemed a procefs ; and, frcm
the appearance it makes with the Jlyliform , have
named it vaginalis. — Others again have, under the
name of auditory procefs, reckoned among the exter-
nal proceffes that femicircular ridge, which, running
between the root of the majloid and zygomatic procef-
fes, forms the under part of the external meatus audi -
tonus.

The finuofities or depreffions on the external fur-
face of each os temporutn, are thefe : — A \or\g fojfa at
the inner and back part of the root of the mammary
procefs, where the poflerior head of the digajlric muf-
cle has its origin. — Immediately before thtroot of the
zygomatic procefs, a confiderable hollow is left, for
lodging the crotaphite mufcle. — Between the zygoma -
tic, auditory , and vaginal proceffes, a large cavity is
formed ; through the middle of which, from top to
bottom, a fifluie is obfervable, into which part of the
ligament that fecures the articulation of the lower
jaw with this bone is fixed. The fore-part of the ca-
vity being lined with the fame cartilage which covers
the tubercle before it, receives the condyle of the jaw ;

and

vO T paiipotifn, (Zt\ovotiSr, xKMTpov, os calaminum, fagitt.ale, da-
vale, acuale, calcar capitis.

C-) Galen, «lc ufu part. lib. 2. cap 4. Fallop. obferr. anatom.

7o Of the S K E L E T O N.

and in the back part a fmall fhare of the parotid ■
gland and a cellular fatty fubflance, are lodged. — . |
At the infide of the root of th t Jiyloid apophyfe, there
is a thimble-like cavity, where the beginning of the
internal jugular vein, or end of the lateral fnus is
lodged. — And as the finufes of the two lides are fre-
quently of unequal fize ; fo one of thefe cavities is
as often larger than the other (d). — Round the exter-
nal meatus auditorius , feveral finuofities are formed
for receiving the cartilages and ligaments of the car,
and for their firm adhelion.

The holes that commonly appear on the outfide of
each of thefe bones, and are proper to each of them,
are five. — The frfy fituated between the zygomatic
and majioid procefies, is the orifice of a large tunnel-
like canal, which leads to the organ of hearing ;
therefore is called meatus auditorius extemus (e). —
The fecond gives paffage to the portio dura of the fe-
venth pair of nerves, ami from its fituation between'
the majloid and Jiyloid procefies, is called foramen fiylo -
tnajloideum (g). — Some way before, and to the infide
of the Jiyloid procefs, is the third hole ; the canal from
which runs firfl upwards, then forwards, and re-
ceives into it the internal carotid artery, and the be-
ginning of the intercoftal nerve; where this canal is
about to make the turn forwards, one, or fometimes
two very fmall holes go off towards the cavity of the
ear, called tympanum j through thefe Valfalva (h) af-
firms the proper artery or arteries of that cavity are
fent. — On the anterior edge of this bone, near the
former, a fourth hole is obfervable, being the orifice
of a canal which runs outwards and backwards, in a.
horizontal direflion, till it terminates in the tympa-
num. This, in the recent fubjedt, is continued for-
ward and inward, from the parts which I mentioned
juft now as its orifice in the lkeleton, to the fide o£

(rf) Ilunauld Mem. de l'acad. drs fciences, 1730.
(e) Tltpe ; rup ok#k. ra> tra*, tcncftra aurium.
(g) Aquacduftus Fallopii.

Dc aure Humana, cap 3. § 22. ct tab. 7. fig. 1.

Of the SKELETON. 71

%

tbenoftrils; being partly cartilaginous, and partly li-
gamentous. The whole canal is named, Iter a pala~
to adauretn , or Eufiachian tube . — On the external fide
of the bony part of this canal, and a-top of the
chink in the cavity that receives the condyle of the
lower jaw, is the.courfe of the little nerve faid com-
monly to be reflected from the lingual branch of the
“fifth pair, till it enters the tympanum , to run acrofs
this cavity, and to have the name of chorda tympanic
— The fifth hole is very uncertain, appearing fome-
times behind the mafioid procefs ; fometimes it is
common to the temporal and occipital bones ; and
in feveral fculls there is no fuch hole. The ufe of it,
when found, is for the tranfmifiion of a vein from
the external teguments to the lateral fitnus : But, in
fome fubje&s, a branch of the occipital artery pafles
through this hole, to ferve the back part of the dura
mater ; in others,! have feen two or three fuch holes:
But they are oftener wanting than found. And we
may, once for all, in general remark, That the large-
iefs, number, fituation, and exiftence of all fuch
ides, that for the mod part allow only a pafiage for
/eins from without to the internal receptacles, are
;ery uncertain.

The internal furface of the ojfia temporum is une-
qual j the upper circular edge of the fquamous part
laving numerous fmall ridges and furrows for its con-
un&ion with the parietal bones ; and the reft of it is
rregularly marked with the convolutions of the mid-
lie part of the brain, and with furrows made by the
[tranches of the ateries of the dura mater.

From the under part of this internal furface, a
arger tranfverfe hard craggy protuberance runs hori-
:ontally inwards and forwards, with a fharp edge a-
•ove, and two flat fides, one facing obliquely for-
wards and outwards, and the other as much back-
yards and inwards. To the ridge between thefe two
ides, the large lateral procefs of the dura mater is
xed.

Sometimes a fmall bone, akin to the fefamoidt is

found

Of the SKELETON.

72

found between the fmail end of this petrous procefs
and the fphenoid bone (a).

Towards the back part of the infide of the os tem-
porum , a large deep fojfa is confpicuous, where the
lateral firms lies ; and frequently on the top of the
petrous . ridge, a furrow may be obferved, where a
fmail Gnus is fituated.

The internal proper foramina of each of thefe
bones ar e,frf, the internal meatus auditorius in the
pofterior plain fide of the petrous procefs. This
hole foon divides into two ; one of which is the be-
ginning of the aqueedudl of Fallopius ; the other ends
in feveral very fmail canals (b) that allow a pafiage to
the branches of the portio mollis of the feventh pair
of nerves, into the ve/tibule and cochlea. Through it
alfo an artery is lent, to be dillributed to the organ
of hearing. — The fecotid hole, which is on the ante-
rior plain fide of the craggy procefs, gives pafiage to
a relieved branch of the fecond branch of the fifth
pair of nerves, which joins the portio dura of the au-
ditory nerve, while it is in the aquaduEl (c), fmail
branches of blood- vefiels accompanying the nfcrves or
palling through fmaller holes near this one. — The
pafiage of the cutaneous vein into the lateral fnustl
or of a branch of the occipital artery, is feen about
the middle of the larg t fojfa for that firms ; and the
orifice of the canal of the carotid artery is evident at
the under part of the point of the petrous procefs.

Befides thefe proper holes of the temporal bones
■which appear on their external and internal furfaces,.
there are two others in each fide that are common to
this bone and to the occipital and fphenoidal bones ;
which fhall be mentioned afterwards in the delcrip-
tion of thefe bones.

The upper round part of the fquamous bones is
thin, but equal ; while the low petrous part is thick

and

(a) Riolan. Comment, de offib. cap. 31. — Window Expofition a-
natomique du corps humain, traitc dcs os fees, § 266.

(b) Valfalv. De aurc humana, cap. 3. § II,

(c) Valfalv. de aure, cap. 3. § 10.

Of the SKELETON.

73

and flrong, but irregular and unequal, having the di-
ftinftion of tables and diploe confounded, with feve-
ral cavities, procelTes, and bones within its fubftance,
which are parts of the organ of hearing. That a
clear idea may be had of this beautiful, but intricate
organ, anatomifts generally choofe to demonstrate all
its parts together. I think the method good ; and
therefore, Since it would be improper to infert a com-
plete treatife on the ear here, mall omit the descrip-
tion of the parts contained within the os petrofum of
the Skeleton.

The temporal bones are joined above to the parie-
tal bones by the Squamous futures, and their polte-
rior additamenta : Before, to the fphenoid bone by the
future of that name ; to the cheek-bones by the zy-
gomatic futures : Behind, to the occipital bone, by the
lambdoid future and its additamenta ; and they are ar-
ticulated with the lower jaw , in the manner which
Shall be deferibed when this bone is examined.

The purpofes wh'ich thefe two bones ferve, are ea-
fily collected, from the general ufe of the cranium ,
and from what has been faid in the defeription of
their Several parts.

In an infant, a fmall fiffiire is to be obferved be-
tween the thin upper part, and the lower craggy
part of each of thefe bones •, which points out the
recent union of thefe parts. — Neither majloid nor Jly-
loid procelTes are yet to be Seen. — Inftead of a bony
funnel-like external meatus auditcrius, there is only a
fmooth bony ring, within which the membrane of
the drum is faltened. — At the entry of the Eujlachian

tube, the fide of the tympanum is not completed A

little more outward than the internal auditory canal,
there is a deep pit, over the upper part of whofe ori-
fice the interior femicircular canal of the ear is
flretched ; and fome way below this, the polteiior fe-
micircular canal alfo appears manifeftly.

OS OCCIPITIS (d), fo called from its fitua-

G tion,

(<0 1 voir, bafilare, proras, memorise, pixidis, fibrofuin, nervofum,
lambde.

74

Of the SKELETON.

tion, is convex on the outfide, and concave internal-
ly. Its figure is an irregular fquare, or rather rhom-
boid ; of which rhe angle above is generally a little
rounded ; the two lateral angles are more finifhed,
but obtufe ; and the lower one is ftretched forward
in form of a wedge, and thence is called by fome the
cuneiform procefs. — If onfc would, however, be very
nice in obferving the feveral turns which the edges
of the os occipitis make, five or feven Tides, and as ma-
ny angles of this bone might be defcribed.

The external furface is convex, except at the cu-
neiform apophyfe, where it is flatted. At the bafe
of this triangular piocefs, on each fide of the great
hole, but more advanced forwards than the middle of
it, the large oblong protuberances, named the cot i-
dy/es , appear, to ferve for the articulation of this bone
•with the firft vertebra of the neck. The fmooth fur-
face of each of thefe condyloid procelfes is longed:
from behind forwards, where, by their oblique fitua-
tion, they come much nearer to each other than they
are at their back part. Their inner Tides are lower
than the external, by which they are prevented from
Hiding to either fide out of the cavities of the firft
vertebra ( e ). In fome fubjeCts each of thefe plain
fmooth furfaces Teems to be divided by a fmall riling
in its middle ; and the lower edge of each condyle,
next the great foramen , is difcontinucd about the
middle, by an intervening notch : Whence fome (f)
alledge, that each of thefe apophyfes is made up of
two protuberances. — Round their root a fmall depref-
fion and fpongy roughnefs is ohfervable, where the
ligaments for furrounding and fecuring their articu-
lations adhere. — Though the motion of the head is
performed on the condyles, yet the centre of gravi-
ty of that globe does not fall between them, but is a
good way further forward ; from which mechanifm
it is evident, that the mufcles which pull the head
back, mult be in a conftant Rate of contraction ;

which

(*) Galen, de ufu part. lib. II. cap. 7.

(f) Diemerbrotk Anat. lib. 9. cap. 6.

which is ftronger than the natural contraction or the
proper flexors, elfe the head would always fall for-
wards, as it does when a man is afleep, or labours
under a palfy, as well as in infants, where the weight
of the head far exceeds the proportional ftrength of
thele mufcles. This feeming difad vantageous fitua-
tion of the condyles, is however of good ufe to us,
by allowing fufficient fpace for the cavities of the
mouth and fauces , and for lodging a fufficient num-
ber of mufcles, which commonly ferve for other
ufes ; but may at pleafure be directed to act on the
head, and then have an advantageous lever to a£t
with, fo as to be able to fuflain a confiderable weight
appended, or other force applied, to pull the head back.

Somewhat more externally than the condyles , there
is a fmall rifing and femilunated hollow in each fide,
which make part of the holes, common to the occipi-
tal and petrous bones. — Immediately behind this, on
each fide, a fcabrous ridge is extended from the mid-
dle of the condyle, towards the root of the mafoid
procefs. Into this ridge the mufculus lateralis , com-
monly aferibed to Fallopius , is inferted. — About the
middle of the external convex furface, a large arch
runs crofs the bone ; from the upper lateral parts of
which the occipital mufcles have their rife ; to its
middle the trapezii are attached : And half way be-
tween this and the great hole, a Idler arch is extend-
ed.— In the hollows between the middle of thefe
aiches the complexi are inferted ; and in the depref-
fions more external and further forward than thefe,
the fplpnii are inferted. — Between the middle of the
leffer arch and. the great hole, the little hollow marks
of the reEli minores appear ; and on each fide of thefe
the flefhy infertions of the obliqui fuperiores and reefi
majores make depreflions. — Through the middle of
the two arches a fmall fharp Jpir.e is placed, which
ferves as fome fort of partition between the mufcles
of different fides, or rather is owing to the action o‘f
the mufcles deprdlirfg the bone on each fide of it,
■uhile this part is free from their compreflion. — Thefe

G 2 prinis-

7 6

Of the SKELETON.

prints of the mufcles on this bone are very ftrong and
plain in fome fubjects, but are not fo diftinCt in others.
— All round the great foramen, the edges are unequal,
for the firmer adhefion of the ftrong circular liga-
ment, which goes thence to the firft vertebra. — One
end of each lateral or moderator ligament of the head,
is fixed to a rough furface at the fore part of each
condyle, and the perpendicular one is connected to a
rough part of the edge of the great hole between the
two condyles. — Immediately before the condyles,
two little depreffions are made in the external furface
of the cuneiform procefs, for the infertion of the
recli anteriores minores mufcles which are unjuftly a-
fcribed to Coivper : And ftill further forward, near
the fphenoid bone, are two other fuch depielfions, for
the reception of the refti anteriores majores. — When
we confider the fize of the prints of mufcles on the
occipital bone, before and behind its condyles, and,
at the fame time, compare their diftances from thefe
centres of motion of the head, we muft fee how-
much ftronger the mufcles are t which pull the head
backwards, than thofc are which bend it forward ;
and how much greater force the former acquire by
the long lever they att with, than the latter which
are inferted fo near the condyles. This great force
in the extenfor mufcles is altogether neceflary, that
they might not only keep the head from falling for-
ward in an erecl pofture, but that they might fupport
it when we bow forward in the moft necelfary offices
of focial life, when the weight of the head comes to
aCt at right angles on the vertebree of the neck, and
obtains a long lever to a£t with.

On the inner furface of the os occipitis we fee two
ridges; one ftanding perpendicular, the other run-
ning horizontally acrofs the firft. The upper part of
the perpendicular limb of the crofs, to which the
falx is fixed, is hollowed in the middle, or often on
one fide, for the reception of the fuperior longitudinal
ftnusy and the lower part of it has the fmall or third
procefs of the dura mater faflened to it, and is fome-

times

j*

77

Of the SKELETON.

times hollowed by the occipital ftnus. Each fide of
the horizontal limb is made hollow by the lateral fi-
nufes inclofed in the tranfverfe procefs of the d ura
mater ; the foffa in the right fide being generally a
continuation of the one made by the longitudinal fi-
nus in the perpendicular limb, and therefore is larger
than the left one (g). — Round the middle of the crofi?
there are four large deprellions feparated by its limbs ;
the two upper ones being formed by the back parr
of the brain, and the two lower ones by the cerebel-
lum.— Farther forward than the lad mentioned de-
preflions, is the lower part of the fojfa for the lateral
ftnus on each fide. — The inner furface of the cunei-
form apophyfe is made concave for the reception of
the medulla oblongata , and of the bafilar artery. — A-
furrow is made on each fide, near the edges of this-
procefs, by a firms of the dura mater , which empties-
itfelf into the lateral ftnus ( h ).

The holes of this bone are commonly five proper,
and two common to it and to the temporal bones. —
The firfi: of the proper holes, called foramen mag -
num (/), from its fize, is immediately behind the
wedge-like procefs, and allows a pafl'age to the me-
dulla oblongata , nervi accefforii , to the vertebral arte-
ries, and fometimes to the vertebral veins- — At each
fide of this great hole, near its fore part* ami imme-
diately above the condyles, we always find a hole,
fometimes two, which loon unite again into one that
opens externally ; through thefe the ninth pair of'
nerves go out of the fkull. — The fourth and fifth
holes pierce from behind the condyle of each fide into*
the fojja of the lateral fnujes ; they lerve for the
pafl'age of the cervical veins to thefe finufes. Often
one of thefe holes is wanting, fometimes both, when
the veins pafs through the great foramen. — Belides
thele five, we frequently meet with other holts near
the edges of this bone, for the tranlmillion of veins ,

G 3 but:

C?) Morgagn. Adverf. anat. 6. a aim ad. X,

(6) Albin. de offib. § 6'.

Rachitidb nudullit iginalis.

Of the SKELETON,

but their number and diameter are very uncertain.
The two common foramina are the large irregular
holes, one in each fide, between the fides of the cu-
neiform procefs, anil the edges of the petrous bones.
In a recent fubjedl, a ftrong membrane runs crofs
from one fide to the other of each of thefe holesr ; in
fome heads I have feen this membrane oflified, or a
bony partirion dividing each hole ; and in the greater
number of adult fkulls, there is a fmal! fiiarp-pointed
procefs Hands out from the os petrofum, and a more
obtufe riling in the occipital bone, between which the
partition is ilretched. Behind this partition, where
the largellfpace is left, the lateral ftnus has its pafiage ;
and before it the eighth pair of nerves and accejforius
make their exit out of the lkull ; and fome authors
fay, an artery paiVes through this hole, to be bellowed
on the dura via ter.

The occipital bone is among the thickeft of the
cranium , though unequally fo ; for it is llronger a-
bove, where it has no other defence than the com-
mon teguments, than it is below, where, being pref-
ft'd by the lobes of the brain and cerebellum on one
fide, and by the a£lion of the mufcles on the o-
ther, it is fo very thin, as to be diaphanous in many
fkulls : But then thefe mufcles ward off injuries, and
the ridges and fpines, which are frequent here, make
it fulliciently ftrong to refill ordinary forces. The
tables and diploe are tolerably diftimfl in this bone>
except where it is fo thin as to become diaphanous.

The occipital bone is joined above to the ojfa pa -
rietalia and triquetra when prefent, by the lambdoid
future ; — laterally to the tempoial bones, by the ad -
ditamenta of the lambdoid future ; — below to the /phe-
nol d bone, by the end of its cuneiform procefs, in the
fame way that epiphyfes and ‘heir bones are joined :
Tor in childi en, a ligamentous cartilage is imerpoted
between : he occipital and fphenoid bones, which
gradually turns thinner, as each of the bones ad-
vances, till their fibres at lalt run into each other;
and, about fixteen or eighteen years of age, the union

Of the SKELETO N.

7?

of thefe two bones becomes fo intimate, that a repa-
ration cannot be made without violence. — The os oc -
cipitis is -joined by a double articulation to the firft
vertebra of the neck, each condyle being received in-
to a fuperior oblique procefs of that vertebra. What
motion is allowed here, we fhall confider afterwards,,
where the vertebra are defciibed.

The ul'es of this bone appear from the preceding
defcription, and therefore need not be repeated.

An infant born at the full time, has this bone di-
vided, by unoflified cartilages, into four parts. — The
firft of thefe is larger than the other three, is of a?
triangular fhape, and conftitutes all the part of the
bone above the.great foramen. Generally fifiures ap-
pear in the upper part and fides of this triangulap
bone, when all the cartilage is feparated by macera-
tion •, and fometimes little diftin£t bones are feen to-
wards the edges o-f it. — The fecond and third pieces
of this bone are exactly alike, and fituated on each
fide of the great foramen ; from which very near the
whole condyle6 are produced ; and they are extend-
ed forwards aim oft to the fore part of the hole fop
the ninth pair of nerves. — The fourth piece is the
cuneiform procefs, which forms a fmall {hare of the
great hole, ami of thefe for the ninth pair of nerves,
and of the condyles : Betwixt it and the fphenoid bone,
a cartilage is interpofed.

Of the eight bones which belong to the cranium ,
there are only two which are not yet defcribed, viz*.
the ethmoid and fphenoid. Thefe we already mention-
ed, in complaifance to the generality of writers on
this iubjedf, as bones common to the cranium and
face, becaufe they enter into the eompofirion of both :
But the fame reafon might equally be ufed for calling
the frontal bone a common one too. I (ball, how-
ever, pals any idle difpute about the propriety of
ranging them, and proceed to examine the ftru&ure
of the bones themfelves.

OS ETHMOIDES (h), or the fieve-like bone,

has

W Cribriformc, rroyyoufoi, fpongifocmc, criflatum.

So

Of the SKELETON.

has got its name from the great number of fmall>
holes with which that part of it firffc taken notice of
is pierced. When this bone is entire, the figure of.
it is not eafily defcrihed ; but, by a detail of its fe-
veral parts, fome idea may be afforded of the whole j
and therefore I fliall diflinguifh it into the cribriform
lamella with its procefs, the nafal lamellay. cellulce , and
off a fpongicfa.

The thin horizontal lamella , is all (except its back,
part) pierced obliquely by a great number of fmall
holes, through which the filaments of the olfa£tory
nerves pafs. In a recent fubjett, thefe holes are fo
clofely lined by the dura mater , that they are much
lefs confpicuous than in the fkeleton . — From the mid-
dle of the internal fide of this plate, a thick procefs
rifes upwards, and, being higheft at che fore part,,
gradually becomes lower, as it is extended back-
wards. From fome refemblance which this procefs
was imagined to have to a cock’s comb, it has been
called crijla galli (/). The falx is connected to its
ridge, and to the unperforated part of the cribriform
plate. — When the crijla is broke, its bafe is fomc-
times found to be hollow, with its cavity opening in-
to the nofe (m). — Immediately before the higheft
part of this procefs, is the blind hole of the frontal
bone, which, as was formerly remarked, is often in a
good meafure formed by a notch in the fore part of
the root of the crijla.

From the middle of the outer furface of the cribri-
form lamellay a thin folid plate is extended down-
wards and forwards, having the fame common bafe
with the crijla galli. Generally it is not exactly per-
pendicular, but is inclined to one fide or other,,
and therefore divides the cavity of the nofe unequal-
ly. Its inclination to one fide, and flexure in. the
middle, is fometimes fo great, that it fills up a large-
Ihare of one of the noftrils, and has been miitook for
a polypus there. — It is thin at its rife, and rather ftill.

thinner.

(/) Verruca rraedura, feptum oflls fpongiofi.

(m) Paifyn Auat. chir. tr. 4. chap, ij.

Of the SKELETON.

8i

thinner in its middle; yet afterwards, towards its
lower edge, it becomes thicker, that its conjunction
with the bones and middle cartilage of the nofe might
be firmer.

At a little difiance from each fide of this external
procefs, a cellular and fpongy bony fubfiance depends
from the cribriform plate. The number and figure
of the cells in this irregular procefs of each fide, are
very uncertain, and not to be reprefented in words ;
only the cells open into each other, and into the ca-
vity of the nofe : The uppermoft, which are below
the aperture of the frontal finufes , are formed like

funnels. The outer furface ot thefe cells is fmooth

and plain, where this bone affifts in compofing the
orbit ; at which place, on each fide, it has got the
name of os planum ; on the upper edge of which, a,
fmall notch or two may fometimes be obferved, which
go to the formation of the internal orbitar holes ; as
was remarked in the defcription of the frontal bone.

Below the cells of each fide, a thin plate is extend-
ed inwards, and then, bending down, it becomes
thick and of a fpongy texture. — This fpongy part is
triangular, with a ftraight upper edge placed hori-
zontally, an anterior one flanting from above* down-
wards and forwards, and with a pendulous convex
one below. — The upper and lower edges terminate in a
fharp point behind.— The fide of this pendulous fpon-
gy part next to the feptum narium is convex, and its ex-
ternal fide is concave. — Thefe two procefi'es of th zeth-
moidbotic have got the nameof offa Jpongiofa, or Uirlinata
fuperiora, from their fubfiance, figure, and fituation.

All the prominences, cavities, and meanders t .his
ethmoid bone, are covered with a continuation ol the
membrane ol the nofinis, in a recent fubjedf. — Its
hoiizontal cribriform plate is lodged between the or-
bitar procefies of the frontal bone, to which it is join-
ed by the ethmoid future, except at the ‘. back-part,
where at is conne£led with the cuneiform bone, by a
a future common to both thefe bones, though it is
generally efieemed part of 4. he fphenoidol. — Where the

offa.

82

Of the SKELETON.

ojfa plana are contiguous to the frontal bone within
the orbit, their conjundion is reckoned part of the
tranfverfe future.— Farther forward than the ojfa plana ,
the cells are covered by the ojfa unguis, which are not
only contiguous to thele cells, but cannot be feparat-
ed from them, without breaking the bony fubftance ;
and therefore, in juftice, thofe bones ought to be de-
monftrated as part of the ethmoid bone. — Below the
ojfa unguis and plana, thefe cells and ojfa fpongiofi are
overlopped by the maxillary bones. — The cellular part
of each palate bone is contiguous to each os planum
and cells backwards. — The lower edge of the nafal
perpendicular plate is received into the furrow of the
vomer. — Its pofterior edge is joined to the fore-part of
the procejfus azygos of the J'phenoid bone. — Its upper
edge joines the nafal procefs of the frontal and nafal
bones, and its anterior one is conneded to the mid-
dle cartilage of the nole.

From all which, the ufes of this bone are evident,
viz. to fuitain the anterior lobes of the brain j to give
palfage to the olfadory nerves, and attachment to
the falx ; to enlarge the organ of fmelling, by allow-
-ing the membrane of the nofe a great extent ; to
-ftraiten the paflage of the air through the nofe, by
leaving only a narrow winding canal, on the fenfible
membranous fides of which the fubftances conveyed
along with the air mull Itrike ; to form part of the
orbit of the eyes and feptum narium j while all its
parts are fo light as not to be in hazard of feparating
by their weight ; and they are fo thin, as to form a
large furface, without occupying much fpace. This
brittle fubftance, however, is fulRciently proteded
from external injuries by the firm bones which co-
ver it.

If this bone is feized on by any corroding matter,
■we may eafily conceive what deltrudion may enfue.
Hence it is, that an ozaena is difficult to cure -x and
that, in violent feurvies, or in the lues venerea, the fa-
bric of the nofe, the eyes, and life itfelf are in dan-
ger.— The fituation of the nafal plate may fiiew us,
* bow

Of the SKELETON. - 83

how dangerous a fra&ure of the bones of the nofc
may be, when made by a force applied to their middle
fore part, of a perfon in- whom this nafal plate is per-
pendicular.

The ethmoid bone of ripe children is divided into
two, by a perpendicular cartilage, which, when ofli-
fied, is the crtfta galli, and nafal plate : but its o-
ther parts are oflified and complete.

OS SPHENOIDES *, or wedge-like bone, fo
called becaufe of its fituation in the middle of the
bones of the cranium and face, is of fuch an irregular
figure, that I know not any thing to which it may be
likened, unlefs, perhaps, it bear fome faint referft-
blance to a bat with its wings extended.

When we view the external furface of the os fphe-
noirfes, two or three remarkable procefles from each
fide of it may be obferved, which are all of them a-
gain fubdivided. — The firfh pair is the two large la-
teral procefies or wings j the upper part of each of
which is called the temporal procefs ^ becaufe they join
with the temporal bones in forming the temples, and
the feat for fome fliare of the crotaphite mufcles.
That part of the wings which juts out towards the
inlide, fomewhat lower than the temporal apopbyfes ,
and is fmooth and hollowed, where it makes up part
of the orbit, is thence named orbitar procejfes. Be-
hind the edge, feparating thefe two procefi'es, there
is often a fmall groove, made by a branch of the fu-
perior maxillary nerve, in its pafiage to the temporal
mufcle. The lowed; and back part of each wing,
which runs out (harp to meet the ojfa petrofa, has been
ftyled the fpinous procefs: From near the point of
which a lliarp pointed procefs is frequently produced
downwards, which fome call Jlyliform , that affords
origin to the ptery-Jlaphylinus externus mufcle. From
this ftyloid procels a very fmall groove is extended a-
long the edge of the bone to the hollow at the root
of the internal plate of the following proceifes, which

forms

• Cnnelfornje, *okv^opjov, multiforme, paxillnm, cribratum pa-
lati, colatorii, cavilla, balilarc.

84 Of the SKELETON.

forms part of the Eujiachian tube (a). — The fecond
pair of external procefles of the cuneiform hone is
the two which Hand out almoft perpendicular to the
bafe of the fcull. Each of them has two plates, and
a middle fojja facing backwards, and ftiould, to carry-
on our comparifon, be likened to the bat’s legs, but
are commonly faid to refemble the wings of that
creature ; and therefore are named pterygoid or ali-
form * procefles. The external plates are broadeft,
and the internal are longeft. From each fide of the
external plates the pterygoid mufcles take their rife.
At the root of each internal plate, a fmall hollow
may be' remarked, where the tnufculus ptery-Jlaphy-
linus internus , or circumjlexus palati rifes, and fome
fhare of the cartilaginous end of the Eujiachian tube
refts •, atid, at the lower end of the fame plate, is a
hook-like rifing or procefs, round which the tendon
of the laft-named mufcle, plays as on a pulley.
From the edge of the external plate fome fmall fharp
fpikcs Hand out ■, but their number and bulk are un-
certain. To thefe another pair may be added, to
wit, the little triangular thin procefs, which comes
from each fide of the body of the fphenoid bone, •
where the pterygoid procefles are rifing from it, and
are extended over the lower part of the aperture of
the ftnus as far as to join the ethmoid bone, while their
body hangs down into the nares (It). — Befides thefe
pairs of procefles, there is a {harp ridge which {lands*
out from the middle of its bafe : Becaufe it wants a
fellow, it may be called procejfus azygos. The lower
part of this procefs, where it is received into the
• vomer , is thick, and often not quite perpendicular,
but inclining more to one fide than the other. The
fore part of this procefs, where it joins the nafal
plate of the os ethmoides , is thin and liraight. Thefe

two
*. 4

(a) Window Expofition anatomiquc du corps humain, traitc des
os fees, § 233.

* Naviculares.

(i) Albin. Tab. ofT. 5'. fig 2. 6. A A.— Berth Mem. de l’acad.
des fcienccs, 1744. — Sue, planchc viii. fig. %. 3. 4. 6.

Of the SKELETON. . 8;

two parts have been defcribed as two diflincb precedes
by tome.

The depreffions, finuofities, and fojfae , on the ex-
ternal furface of this fphenoid bone, may be reckoned
up to a great number, viz. two on the temporal
apophyfes where the crotaphyte mufcles lodge. — Two
on the orbitar precedes, to make way for the globes
of the eyes. — Two between the temporal and fpincns
precedes, for receiving the temporal bones. — Two
between the plates of the pterygoid precedes, where
th tmufeuli pterygoidei intend and ptcry-ftnphylini inter id
are placed. — Two between the pterygoid and orbitar
precedes, for forming the holes common to this and
to the cheek and maxillary bones. — Two on the lower
ends of the aliform precedes, which the palate bones
enter into. — Two at the roots of the temporal and
pterygoid precedes, where the larged fliare of the ex-
ternal pterygoid mufcles have their rife. — Two at the
ddes of the procejfus azygos, for forming part of the
nofe, &c.

What I defcribed under the name of temporal and
Jpinous protejjes on the outfide of the fcull, are like-
wife feen on its infide, where they are concave, for
receiving part of the brain; and commonly three
apophyfes on the internal furface of the fphenoid bone
are only mentioned. Two riling broad from the
fore-part of its body, become final! er as they are ex-
tended obliquely backwards. — The third (landing on
a long tranfverfe bafe, near the back-part of the body
of this bone, rifes nearly eredl, and of an equal
breadth, terminating often in a little knob on each
fide. 'I he three are called clinoid, from fome refem-
blance which they were thought to have to the fup-
porters of a bed. Sometimes one or both the ante-
rior clinoid precedes are joined to the fides of the po-

fterior one, or the body of the bone itfelf From the

roots of the anterior clinoid precedes the bone is ex-
tended on each fide outwards and forwards, till it
ends in a fliarp point, which may have the name of
the tranfverfe Jpinous precedes — Between, but a little

H farther

86

Of the SKELETON.

farther back than the two anterior clinoid procefles,
we fee a protuberance confiderably fmaller than the

poftcrior clinoid procefs, but of its fliape Another

procefs from between the tranfverfe procefles, often
forces itfelf forwards into the os ethmoides.

Within the fcull, there are two finuofities in the
internal part of each wing of the fphemid bone, for
receiving the middle part of the brain. — One between
the tranfverfe fpinous procefles, for lodging the part
of the brain where the crura mtdullae oblongatae are. —
Immediately before the third or middle clinoid procefs,
a Angle pit generally may be remarked, from which
a fojja goes out on each fide to the holes through
which the optic nerves pafs. The pit is formed by
the conjoined optic nerves ; and in the foffx thefe
nerves are lodged, as they run divided within the
fcull. — Between that third protuberance and the po-
lder ior clinoid procefs, the larger pit for the glatidula
pituitaria may be remarked, l'his cavity, becaufe of
its refemblance to a TurkifJj faddle, is always deferib-
ed under the name of fella ’Turcica , or epbippium. —
On the fides of the poftcrior clinoid procefs, a foffa may
be remarked, that ftretches upwards, then is con-
tinued forwards along the Tides of the fella Turcica ,
near to the anterior clinoid procefles, where a pit on
each fide is made. Thefe foffx point out the courfe
of the two internal carotid arteries, after they have
entered the fcull. — Befides all thefe, feveral other
foffa may be obferved, leading to the feveral holes,
and imprinted by the nerves and blood -veflels.

The holes on each fide of the os fpbenoides are fix
proper, and three common. — The fitjl is the round
One immediately below the anterior clinoid procefles,
for the paflage of the optic nerve, and of the branch
of the internal carotid artery that is fent to the eye. —
The fecond is the foramen lacerumy or large flit be-
tween the tranfverfe fpinous and orbitar procefles :
The interior end of which flit is large ; and, as it is
extended outwards, it becomes narrower. The outer
cud of it is formed in the os frontis -7 and therefore

Of the SKELETON. 87

this might be reckoned among the common foramina.
Through it the third, fourth, the firft branch of the
fifth, and the greater fhare of the Gxthpairof nerves,
and an artery from the internal carotid, go into the
orbit. Sometimes a fmall branch of the external ca-
rotid enters near its end, to be diftributed to the dura
mater (a) \ and a vein, fome call it the venous ducl>
or, NucVs aqtueduB , returns through it to the ca-'
vernous finus. — The third hole, fituated a little below
the one juft now defcribed, is called rotundurff'i from
its fhape. It allows paffage to the feccn^i branch of
the fifth pair of nerves, or fuperior maxillary nerve,
into the bottom of the orbit. The fourth is the fora-
men ovale , about half an inch behind the round hole*
Through it the third branch of the fifth pair, or in-
ferior maxillary nerve, goes out ; and fometitnes a
vein from the dura mater pafies out here ( h ). — Very
near the point of the fpinous procefs is the fifth hole
of this bone: It is fmall and round, for a paflage to
the largeft artery of the dura mater , which often is
accompanied with a vein. The fixth proper hole (c)
cannot be well feen, till the cuneiform bone is fepa-
ratcd from all the other bones of the cranium ; for
one end of it is hid by a fmall protuberance of the in-
ternal plate of the pterygoid procefs, and by the point
of the proceffus petrcfus of the temporal bone. Its ca-
nal is extended above the inner plate of the pterygoid
procefs i and where it opens into the cavity of the
nofe, it is concealed by the thin laminous part of the
palate bone. Through it a confiderable branch of the
fecond branch of the ffth pair of nerves is refletff-
ed. — Often in the middle of the fella Turcica a fmall
hole or two pierce as far as the cellular i'ubftartce of
the bone) and fometimes at the fides of this fellay
one or more fmall holes penetrate into the fphenoidah

H 2 ftnufei.

(a) Window Expofition anatomique du corps hijmain, traite d<*
arteries, § 60. et de la tete, § %t>.

(b) Ingral!’. Com men tar. in Galen, de odib. lib. I. comment. 8.

fc) Vela I . Anat. lib. i. cap. ra.— Euftach. tab. 46. fig, 13. &

16 — Vidus Viuius Anat. lib. a. cap. a. explicate tab. 5. & tab. 5.
i>g. 8. 9. 10. lit. O.

88

Of the SKELETON.

fmufes. Thefe obfervations afforded fome an ato miffs
(<?) an argument of weight in their days in defence
of Galen (b), who afferted the defeent of the pituita
that way into the JmuJes below.

The frjl of the common holes is that unequal fif-
fure at the fide of the fella ‘Turcica , between the ex-
treme point of the os petrofum and the fpinous procefs
of the cuneiform bone. This hole only appears after
the bones are boiled ; for in a recent fubjedl its back
part is covered by a thin bony plate that lies over the
internal carotid artery, and further forward it is filled
with a cartilaginous ligament, under which the car-
tilaginous part of the Eujiachian tube is placed : It
was by this paflage that the ancients believed the f imy
matter was conveyed from the eumuinftory of the
brain, the glandula piluitaria, to the fauces. — The fe-
cond common hole is the large difeontinuation of the
external fide of the orbit, left between the orbitar
proceffes of the cuneiform bone, the os maxillare , ma-
lee, and palati. In this large hole the fat for lubrica-
ting the globe of the eye and temporal mufcle is.
lodged, and branches of the fuperior maxillary nerve,
with fmall ateries from the carotid and veins pafs. —
The third hole is formed between the bafe of this
bone and the root of the orbitar procefs of the palate
bone of each fide. Through this a branch of the
external carotid artery, and of the fecond branch of
the fifth pair of nerves, are allowed a paflage to the
noflrils, and a returning vein accompanies them.
Sometimes, however, this hole is proper to the palate
bone, being entirely formed out of its fubftance.

Under the fella Turcica , and fome way farther for-
ward, but within the fubftance of thefphenoid bone,
are two fnufes, Teparated by a bony plate. Each of
them is lined with a membrane, and opens into the
upper and back-part of each noltril by a round hole,
which is at their upper fore-part. This .hole is not

formed

(u) Jac. Sylv. Calumniac fccurulx amolitio.— Laurent. flirt. anat.
lib. ?■ queft. i I.

( b ) Galen De ufu part. lib. 9. cap. 1.

Of the SKELETON. 8g

formed only by the os fphenoides, which has an aper-
ture near as large as any tranfverfe fecLion of they?-
mts, but alio by the palate bones which are applied to
the fore-part of thefe finufes , and clofe them up, that
hole only excepted, which was already mentioned.
Frequently the vno finufes are of unequal dimenfions,
and fometimes there is only one large cavity, with an
opening into one noftril. Thefe cavities are likewife
faid \a) to be extended fometimes as far back as the
great foramen of the occipital bone. In other fub-
jc£ts they are not to be found, when the bone is
compofed of large cells ( b ). Some ( c ) mention a ca-
vity within the partition of the finufes ; but it is ffriall.
— The fphenoidal finufes ferve the lame ules as the
frontal do.

As this bone is extremely ragged and unequal, fo
its fubftance is of very different thicknefs, being in
fome places diaphanous ; in others it is of a middle
thicknefs, and its middle back-part furpaffes the
greatefl: lhare of the cranium in thicknefs.

The os fpbenoides is joined, by its wings, to the pa-
rietal bones above, to the os frontis and ojfa malarum
before, to the temporal bones behind ; — by the fore-
part of its body and fpinous proceffes, to the frontal
and ethmoid bones; — by its back-part, behind the two-
ftnufes , to the occipital , where it looks Like a bone
with the epiphyfes taken off, and, as was formerly ob-
ferved in the defeription of the occipital bone, it
cannot be feparated without violence in adults; — to
the palate bones, by the ends of the pterygoid procef-
fes, and Hill more by the fore-part of the internal
plates of the pterygoid proceffes, and of the finuf-
es ; — to the maxillary bones, by the fore-part of
the external pterygoid plates ; — to the vomer and
nafal plate of the os ethmoides , by the proceffes
, azygos. All thefe conjunctions, except the lall,
which is a fchyndelfs, are faid to be by the futurG
proper to this bone ; though it is at Hi fl fight evident,

H 3 that

(a) Albin. tie ofTib. § 39.

( i ) VeltJ. lib. 1. cap. 6.

(c) let. ibid.

. • J- ^ •' ■-** • -

po Of thr SKELETON.

that feveral other futures, as the tranfverfe , ethmoidal,
&c. are confounded with it.

We fee now how this bone is joined to all the bones
of the cranium , and to moil of the upper jaw ; and
therefore obtained the name of the wedge like bone.

The ufes are fo blended with the defeription, as to
leave nothing new to be added concerning them.

The fphenoidal bone is almoft compleat i n a foetus
of ninth months ; only the great alee feparate after
maceration from the body of the bone. — Th e procef-
fus azygos is very large and hollow ; — the thin trian-
gular precedes are not oflified ; — the internal furface of
the body is unequal and porous •, — the fmufes do not
appear.

Whoever is acquainted with each bone of the cra-
nium, can, without difficulty, examine them as they
Hand united, fo as to know the thapes, fizes, dis-
tances, Isle. of their feveral parts, and the forms,
capacities, iffc. of the cavities formed by them,
•which is of great ufe towards underftauding the ana-
tomy of the parts contiguous to, contained within,
or conne&ed to them. Such a review is neceflarv,
after confidering each clafs of bones. Thus the or-
bits, noflrils, mouth, face, head, fpine, thorax, pel-
vis, trunk, extremities, and fkeleton, ought likewife
to be examined.

The FACE is the irregular pile of bones, compof-
ing the fore and under part of the head, which is di-
vided, by authors, into the upper and lower maxilU
or jaws.

The fuperior maxilla (J) is the common defignation
given to the upper immoveable fhare of the face}
though, if we would follow Celfus (e), we fhould ap-
ply the word maxilla to the lower jaw only, and the
name mala to this upper jaw. In coinplaifance to
prevailing cuftom, I fhall, however, ufe the terms as
now commonly employed. The fhape of the fupe-
rior jaw cannot eafily be exprefled nor is it necefla-

*7>

(</) 2 1 tryai, yivo(, mandibula.

(r) L.ib. 8. cap. J.

Of the SKELETON.

9l

ry, provided the fhape and fituation of all the bones
which compofe it are defcribed. It is bounded above
by the tranfverfe future, behind by the fore-part of
the Jphenoid bone, and below by the mouth.

The upper jaw confifls of fix bones on each fide,,
of a thirteenth bone which has no fellow, placed in
the middle, and of fixteen teeth. The thirteen bones
are, two ojfa naft, two ojfa unguis, two ojfa malar um,
two ojfa tnaxillaria , two ojfa palati, two ojfa Jpongioja
inferiora , and the vomer.

The ojfa nafi are placed at the upper part of the
nofe ; — the ojfa unguw are at the internal canthi of the
orbits ; — ojfa malarum form the prominence of the
cheeks ; — ojfa tnaxillaria form the fide of the nofe,
with the whole lower and fore-part of the upper jaw,
and the greateft fhare of the roof of the mouth ; —
ojfa palati are fituated at the back-part of the palate,
nourils, and orbit; — ojfa jpongioja are feen in the
Itower part of the nares ; — and the "joiner helps to fe-
parate thefe two cavities.

The bones of the upper jaw are joined to the bones of
the fcull by the Jchyndelefis and futures already defcrib-
ed as common to the cranium an ftface, and they are
connected to each other by gomphefts and fifteen fu-
tures.

The gomphefts only is where the teeth are fixed in
their fockets, and the JchytideleJts is only where the
edges of the vomer are joined to other bone9.

The futures are generally diftinguifhed by numbers,
which have been differently applied ; and therefore I
join thofe (f) who prefer the giving names to each,
which may be eafily contrived from their fituation,
or from the bones which they conneft.

The firft is the anterior najal ( g ), which is ftraight,
and placed longitudinally in the middle fore-part o£
the nofe.

The

(f) Vander Linden. Medicin. phyfiolog. cap. 13. art 2. fe<ft. 10.
— Rolfinc. A.nat. lib. 3. cap. 2j. — Schenk, Schol. part, ft it. ult. par.
a. cap. 5.

(£) Na&Usiedta.

-T

92 Ob the S K E L:'E T O N.

The fecond and third are the lateral nafal [h\
which are at each fide of the nofe, and almoft paral-
lel to the firft future.

Each of the two lacrymal is almofl femicircular,
and is placed round the lacrymal groove.

• The iixrh and feventh are the internal orbitar : each
of which is extended obliquely from the middle of
the lower fide of an orbit to the edge of its bafe.

The two external orbitars are continued, each from
the end of the internal orbitar, to the under and
fore-part of the cheek.

The tenth is the tnxjlachial, which reaches only
from the lower part of the feptum narium to between
the two middle dentes incifores.

The longitudinal palatefi) future flretches from the
middle of the foremolt teeth through the middle of
alhthe palate.

The tranfverfe palate one (f) runs acrofs the palate,
nearer the back than the fore-part of it.

Each of the two pa/ato-ma,xillary is at the back part
of the fide of each noflril.

The fifteenth is the fpinous , which is in the middle
of the lower part of the noflrils. This may perhaps
be rather thought a double fchyndelefs.

The connexion of the ojfa fpongiofa to the fide of
each noflril, is fo much by a membrane in young
fubjedts, by a fort of hook, and afterwards by con-
cretion or union of fubftance in adults, that I did not
know well how to rank it : But if any choofes to call
it a future, the addition of two tranfverfe nafal
futures may be made to thofe above named.

Thefe futures of the face (formerly called harmonise )
have not fuch confpicuous indentations as thofe of the
fcull have ; the bones here not having fubftance e-
nough for forming large indentations, and there
being lefs neceffity for fecurity againft exremal inju-
ries, or any internal protruding force, than in the

cranium. —

(£) Nafalij obliqua.

(i) Laquearis, palataria refta.
(it) Arcuata, palatina p^ftica.

Of the SKELETON.

93

cranium. — Thefe futures often difapear in old people,
by the bones running into each other ; which can da
little prejudice, becaufe the principal ufe of the bones
being fo numerous here, is to allow them to be ex-
tended into a proper form.

It is evident, from the manner of the conjunction
of thefe bones, that they can have no motion, except
in common with the cranium.

The purpofes which this pile of bones ferves, will
be fliewn in the defcription which I am to give of
each of them.

• OSSA NASI , fo named from their fituation at the
root of the nofe, are each of an irregular oblong
fauare figure, being broaded at their lower end, nar-
rowed: a little higher than their middle, and becom-
ing fomewhat larger at the top, where they are ragged
and thicked, and have a curvature forwards, that
their connection with the yrertta/bonehnight be drong-
er. — Thefe bones are convex externally, and there-
by better refill any violence from without ; and they
are
the

The lower edge of thefe bones is unequal, and is
dretched outwards and backwards, to join the carti-
lages of the nodrils. — Their anterior fide is thick,
efpecially above, and unequal, that their conjun£tion
to each other might be dronger; and a fmall riling
may be remarked on their inner edge, where they are
fudained by the jeptum narium. — Their poderior fide,
at its upper half, has externally a deprefiion, where
it is overlopped fome way by the maxillary bones,
while its lower half covers thefe bones : By which
contrivance, they do not yield eafily to prelfure ap-
plied to their fore-part or fides.

A fmall hole is frequently to be obferved on their
external furface, into which two, three, or four holes,
which appear internally, terminate for the tranfmif-
fion of fmall veins; fometimes the holes go no fur-
ther than the cancclli of the bones.

concave internally, for enlarging the cavity of
nofe.

The

9 4

Of the SKELETON.

The nafal bones are firm and folid, with very few
cells or cancelli in them ; the thin fubftance of which
they confift, not requiring much marrow.*

. They are joined above the frontal bone, by the
middle of the tranfverfe future ; — behind, to the max-
illary bones, by the lateral nafal futures; — below, to
the cartilages of the nofe ; — before, tQ one another,
by the anterior nafal future ; — internally, to the fep-
tum narium.

Thefe bones ferve to cover and defend the root of
the nofe.

In an infant the nafal bones are proportionally {hott-
er, and lefs thick at their upper part, than in an ad-
ult, but are otherwife compleat.

OSSA UNGUIS, or LACRTMAL1A, are fo na-
med, becaufe their figure and magnitude are fome-
thing near to thofe of a nail of one’s finger, and be-
caufe the tears pafs upon them into the nofe.

Their external furface is compofed of two fmooth
concavities and a middle ridge. — The depreflion be-
hind forms a fmall {hare of the orbit for the eye-ball
to move on, and the one before is a deep perpendi-
cular canal, or foffa , larger above than below, con-
taining part of the lacrymal fac and This is the

part that ought to be pierced in the great operation
for the fijlula lacrymalis. — This foffa of the bone is
cribriform, or has a great number of fmall holes
through it, that the filaments from the membrane
which lines it, infinuating themfelves into thefe holes,
might prevent a feparation of the membrane, and fe-
cure the bone in its natural fituation. — The ridge be-
tween thefe two cavities of the os unguis , is the pro-
per boundary of the orbit at its internal canthus ; and
beyond which furgeons fliould not proceed backwards
in performing opeiations here. — The internal or pof-
terior furface of this bone confifls of a furrow in the
middle of two convexities.

The fubtlance of the os unguis is as thin as paper,
and very brittle ; which is the xeafon that thefe bones

a.ra

Of the SKELETON. 9£

are often wanting in fkeletons, and need little force
to pierce them in living fubje£b.

Each of thefe bones is joined, above, to the frontal
bone, by part of the tranfverfe future ; — behind, to
the os planum of the ethmoid bone, by the fame fu-
ture ; — before, and below, to the maxillary bone, by
the lacrymal future ; — internally, the offa unguis cover
fome of the fimis ethmoidales ; nay, are really conti-
nuous with the bony lamella which make up the fides
of thefe cells ; fo that they are as much part of the
ethmoid bone as the offa plana.

Thefe unguiform bones compofe the anterior in-
ternal parts of the orbits, lodge a (hare of the lacry-
mal fac and du£t, and cover the ethmoid cells. — Their
fituation and tender fubftance make a rafh operator
in danger of deftroying a confiderable fhare of the or-
gan of fmelling, when he is performing the operation
of the fflula lacrymalis ; but when thefe bones are
hurt, they call off without much difficulty, and con-
fequently the wound is foon cured, unlefs the patient
labours under a general cacoethes , or there is a predif-
pofition in the bones to caries \ in which cafe, a large
train of bad fymptoms follow, or, at beft, the cure
proves tedious.

Thefe bones are fully formed in a new-born child.

OSSA MALARU M ( c ) was the name given by
Celfusy as was already remarked, to all the upper jaw ;
but is now appropriated to the prominent fquare bones
which form the cheek on each fide. — Before, their
furface is convex and fmooth ; backward, it is une-
qual and concave, for lodging part of the crotaphyte
mufcles.

The four angles of each of thefe bones have been
reckoned procefles by fome. — The one at the external
canthus of the orbit, called the fuperior orbit ar procefs,
is the longeft and thickell. — The fecond terminates
near the middle of the lower edge of the orbit in a
lharp point, and is named the inferior orbitar procefs.
—The third, placed near the lower part of the cheek,

and

(0 Jugalia vel zygomatica, hypopia, ffabocularla.

Of the SKELETON.

96

and thence called maxillary , is the fhorteft, and near-
eft to a right angle — The fourth, which is called zy-
gomatic, becaufe it is extended backwards to the zy-
goma of the temporal bone, ends in a point, and has
one fide ftraight, and the other floping. — Between
the two orbitar angles there is a concave arch, which
makes about a third of the external circumference of
the orbit, from which a fifth procefs is extended back-
wards within the orbit, to form near one third of
that cavity j and hence it may be called the internal
orbitar procefs. — From the lower edge of each of the
ojfa malarum , which is between the maxillary and zy-
gomatic proceftes, the majfeter mufcle takes its ori-
gin j and from the exterior part of the zygomatic pro-
cefs, th t tnufculus dijlortor oris rifes ; in both which
places the furface of the bone is rough.

On the external furface of each cheek-bone, one
or more fmall holes are commonly found, for the
tranfmii&on of ftnall nerves or blood-vefl'els from, and
fometimes iuto the orbit. — On the internal furface
are the holes for the paflage of the nutricious veffels
of thefe bones. — A notch on the outfide of the inter-
nal orbitar procefs of each of thefe bones, allifts to
form the great Hit common to this bone and to the
fphenoid, maxillary, and palate bones.

The fubftance of thefe bones is, in proportion to
their bulk, thick, hard, and folid, with fome cancelli.

Each of the ojfa malarum is joined, by its fuperior
and internal orbitar proceftes, to the os frontis , and
to the orbitar procels of the fphenoid bone, by the
tranfvcrfe future. — By the edge between the internal
and inferior orbitar proceftes, to the maxillary bone, by
the internal orbitar future. — By the fide between the
maxillary and inferior orbitar procefs, again to the
maxillary bone, by the external orbitar future. — By
the zygomatic procefs, to the os temporum , by the zy-
gomatic future.

The cheek-bones are entire, and fully offified in all
their parts in infants.

0SS4

97

Of the S K E L E T O N.

OSSA MAXILLARIA SUPERIOR A, are the
largeft bones, and conflitute the far greater part of
the upper jaw, which has appropriated the name of
in axillana to them. JThe figure of one of them, or
of the two when joined, is fo irregular, that words
can fcarce give an idea of it.

The procelles of each os maxillare may be reckon-
ed fcven. — The firjl is the long nafal one at its upper
and fore-part, which is broad below, and turns
fmaller, as it rifes upwards, to make the fide of the
nofe. — At the root of this, a tranfverfe ridge may be
obferved within the noftrils, which fupports the fore-
part of the upper edge of the os fpongioftim tnferius. —
The feeotid is produced backwards and outwards, from
the root of the nafal procefs, to form the lower fide

of the orbit, and therefore may be called orbitar.

The edge of this orbitar procefs, and the ridge of
the nafal one, which is continued from it, make a
confiderable portion of the external circumference of
the crbit. — From the proper orbitar procefs, a very-
rough triangular furface is extended downwards and
outwards, to be conne&ed to the cheek-bone ; and
therefore may be called the malar procefs, from the
loweft protuberant part of which fome fhare of the
mafieter mufcle takes its rife. — Behind the orbitar
procefs, a large tuberolity or bulge of the bone ap-
pears, which is efteemed the fourth procefs. — On the
internal part of this we often meet with a ridge, al-
moft of the fame height with that in the nafal pro-
cefs, which runs tranfverfely, and is covered by a.
fimilar ridge of the palate bene, on which the back-
,part of the upper edge of the os fpongifum infer: us

refts. The convex back-part of this tuberolity is

rough for the origin of part of the external pterygoid
mufcle (a), and more internally is fcabrous, where

the palate and fphenoid bones are joined to it.

That fpongy protuberance (b) at the lower circum-
ference of this bone, where the fockets for the teeth

I

(<0 Albin. dc olfib. § 79.
(i>)

arc

Of the SKELETON.

ys

are formed, is reckoned the fifth. — The fixth is the
horizontal plate, which forms the greater part of the
bafe offthe noflrils, and roof of the mouth-, its up-
per furface, which belongs to the noflrils, is very
fmooth, but the other below is arched and rough,
for the flronger adhefion of the membrane of the
mouth, which is flretched upon it, and in chewing,
fpeaking, life, might otherwife be liable to be fepa-
rated. — The feventb rifes like a fpine from the inner
edge of the laft, and forms a fmall part of the par-
tition of the nollrils.

The deprefTions in each maxillary bone are, i. A
finuofity behind the orbitar procefs, made by the
temporal mufcle. 2. A pit immediately before the
fame procefs, where the origin of the mufculus eleva-
tor lahiorum communis, and elevator labii fuperioris,
with a branch of the fifth pair of nerves, are lodged
fecurely. 3. The hollow arch of the palate. 4. The
femicircular great notch, or entry to the lower part of
the noflrils, betwixt the root of the nafal procefs and
fpine of the palate-plate. — Below this, the fore-part
of the bone is flatted, or fometimes hollowed by the
mufculus depreffor labii fuperioris. 5. Sockets for the
teeth u) : The number of thefe fockets is uncertain;
for the, fame number of teeth is not in all people,
and the four backmofl teeth of each fide of each jaw
vary greatly in their number of roots; and when the
teeth of a living perfon fall out, or are taken away,
the fockets fill up with an offeous net-work, which
becomes folid afterwards. 6. The lacrymal foffa in
the nafal procefs, which afiifls the os unguis to form a
pillage for the lacrymal duel. This part of the bone
forming this foffa , is lb firm and flrong, that a furgeon
fcarce can perforate it with the ordinary inflruments
for ihcfifiula laerymalis, and therefore ought to avoid
it in doing this operation. — Immediately on the out-
fide of this, there is a fmall depreffion, from which
the inferior or lefTer oblique mufcle of the eye has its

origin.

(c-) Bofyia, oxftirxoi, alveoli, foflulK, mortariola, frauia, locclli, ca-
va;, pralltpiola, loculamenta.

f

99

Of the SKELETON.

origin {d). 7. The canal on the upper part of the

great tuberofity within the orbit, which is almoft a
complete hole ; in this a branch of the fuperior max-
illary nerve pafles. — Befides thefe, the fuperior fur-
face of the great bulge is concave, to receive the un-
der part of the eye. — Immediately above the tranf-
verfe ridge in the nafal procefs, a fmall hollow is

formed by the os fpongiofum. In fome fubjects, the

nafal procefs has a fmall round pit above the lacrymal
dudb, where 'the little tendon or ligament of the or-
bicular mufcle of the eye-lids is inserted. It is this
tendon, and not the tendon of the larger oblique
mufcle of the eye, which there is fome hazard of
cutting in the operation of the fifula lacrymalis.

The holes of this bone are, two proper and two
common, which are always to be found ; befides fc-
veral others, whofe magnitude, number, £tY. are un-
certain.— The firll of the proper is the external orbi-
tary immediately below the orbit, -by which the infra-
Orbitar branch of the fecond branch of the fifth pair
of nerves, and a fmall artery, come out, after hav-
ing paffed in the canal, at the bottom of the orbit,
defcribed numb. 7. of the depreffions. — This hole is
often double, and that when the nerve has happened
to fplit before it has efcaped from the bone. — The
fecond is the foramen incifivum , jufi: behind the fore-
teeth, which, at its under part, is one irregular hole
common to both the maxillary bones when they are
joined; but, as it afcends, loon divides into two,
three, or fometimes more holes : fome of which open
into each nofiril. Through them fmall arteries and
veins, and a twig of the fecond branch of the fifth
pair of nerves pals, and make a communication be-
tween, or join the lining coats of tbe nofe and
mouth. In fome fubjefts Steno’s du<ft may be traced
fome way on the fide of thefe paflages next to the
nofe, and fmall orifices may be obferved opening in-
to the mouth.

I 2 The

V) Winflow Expofitioa arutomique dcs os fees, § 2 ; 6.

Joo Of the SKELETON.

The firft common hole is that which appears at the
inner fide of the back-part of the tuberofty and of the
fockets of the teeth, and is formed by a fojfa in this
bone, and a corresponding one in the os palati :
through it a nerve, which is a branch of the i'econd
branch of the fifth pair, runs to the palate. — The
other common hole is the great flit in the outfide of
the orbit dtferibed already, as the fecond common
hole of the fphenoid bone.

On the nafal procefs often holes may be obferved
for the paflage of vcflels to the fubftance of the bones;
and, at the back-part of each tuberofity, feveral fora-
m'rna are placed, for the tranfmiflion of nerves to the
cavity within : but thefe are uncertain.

All the body of the maxillary bone is hollow, and
leaves a large firms akin to the frontal and fphenoid ,
which is commonly, but unjuftly called antrum High-
inorianum (e). When the os maxi Hare is fingle, or fe-
parated from all the other bones of a fkeleton, its
antrum appears to have a large aperture into the
noflrils ; but, in a recent fubje£t, it is fo covered at
its back-part, by the palate bone; in the middle, by
the os fpongiofum infer ius ; before, by a Urong mem-
brane, that one, or fometimes two holes, fcarce larger
than a crow-quill, are only left at the upper part;
which, after a fhort winding progrefs, open into the
noltrils between the two ofa fponginfa. — At the bottom
of this cavity, we may often obierve fome protube-
rances, in which the l'mall points of the roots of the
teeth are contained (f). — This cavern and the fock-
ets of the teeth are often divided by the interpofition
only of a very thin bony plate, which is liable to be
eroded by acrid matter collected in the antrum , or to
be broke in drawing a tooth ( g ). The fymptoms of
a collection of matter here, naturally led us to the
pra£tice of pulling out the teeth, and piercing
through this plate into the antrum , to procure an e-

vacuation

( c ) Gena?.

(f) Highmore Difquif anat. lib. 3. par. 2. cap. I.

(j;) Highmore, il id.

IOI

Of the SKELETON.

vacuatiori of the colle&ed matter ; by which confide-
rable fervice is frequently done ( h ).

The maxillary ftnufes have the fame ufes as the
frontal and fpheuoidal ; and the fituation of the fmufes
is fuch, that the liquor drilling from them, from the
cells of the ethmoid and palate bones, and from the
lacrymal du£ts, may always moiflen all the parts of
the membrane of the nares in the different fituations
which the head is in.

Though the membranes which line the frontal y
fphenoidal, and maxillary finufe s, are continuations ot
the one which covers the bones within the nofe; yet
they are much thinner than it is, and have fo much
fmaller veffels, that the inject ion which makes the
membrane of the nofe red all over, fills only fome
few vtfTels of the maxillary finufes , and fcarce is ob-
ferved in the frontal and fpheuoidal. Are not the
larger veffels intended for a more plentiful fecretion
of a vifcid liquor to defend the membrane from the
effe£ls of the perflatus , which is conftantly through
the nofe ? Are not the membranes which have the
fmallefl veffels, cateris paribus , the mofl fenfible ?
Are not many phaenomena of fmelling, inflamma-
tions of thefe parts, megrim, polypi , £jV. depending
on this ftru&ure of thefe membranes?

The fubflance of the of a maxillaria is compa£l: and.
firm, except at the inferior proceffes, in which the
teeth are lodged, where it is very fpongy.

The maxillary bones are joined above by the upper-
ends of their nafal proceffes to the os frontis , by the
tranfverfe future ; — at the fides of thefe proceffes, to
the ojfa unguis, by the lacrymal futures ; — to the nafal
bones, by the lateral nafal futures; — by their orbitar
proceffes, to the cheek bones, by the external orbitar
futures; — by the internal fides of the internal orbitar
proceffes, to the of'a plana, by part of the ethmoidal
future; — by the back-part of the tuberofities, to the
palate bones, by the futures palato-maxillares ; — by the

I 3 pcflcrior

(S) Cowpcr in Drake’s anthropol, book 3. chap, ro.— Medicaf
Mays and obferv. vol. j. art. 30.

102 Of the SKELETON.

pofterior edges of their palatine lamella , to the o/Jh
palati , by the tran/ver/e palate future ; — by their nafal
/pities to the vomer , by the fpinous future ; — by their
fockets, to theteeth,by gomphb/is ; — by the internaledge
of the palate-plate, to one another, by the longitudinal J
palate future*, on the upper and fore-part of which a
furrow is left for receiving the cartilage which forms
the partition of the noftrils *, — between the fore-part
of the noliiils and mouth, to each other, by the >wy-
(lachial future ; — fometimes they are connected to the
cjfa fpongio/a inferiora , by a plain concretion or union
of fubftance.

Thefe bones form the greater part of the nofe and
of the roof of the mouth, and a confiderable {hare
of the orbit. They contain fixteen teeth, give rife
to mufcles, tranfmillion to nerves, l&c. as mention-
ed in the description of their feveral parts.

In each of the maxillary bones of a new-born
child, the external orbitar procefs is hollow, with re-
markable holes in it ; — there are five fockets for the
teeth, of which the two polterior are very large, and,
when divided by a fecond crofs partition, make the
number of fockets fix (/). — The palate-plate is cribri-
form about the middle. — The great tuberofity is not
formed ; — inftead of the antrum , there is only an ob-
long depreflion at the fide of the noftrils.

OSSA PALATI are commonly deferibed as two
fmall fquare bones, at the back-part of the palate or
i oof of the mouth, though they are of much greater
extent, being continued up the back-part of the no-
itrils to the orbit (k). Each palate-bone may there-
fore be divided into four parts, the palate fquare
bone, the pterygoid procefs, nafal lamella, and orbi-
tar procefs.

* The

(i) Albin. Oftcologen. tab. J. fig. 45.— Ungebav. de dentit. fecund,
jun. § x.

(4) Euflach. tab. 47- fig- *>3. 6> 7. 8;— Vidus Vidius dc Anat.
lib. 2. cap. 2. explicat. tab. 6. fig. 19. — Winilow Memoircs dc 1 acad.
dcs fciences, 1720.

Of the SKELETON.

103

The fquare-bone is unequally concave, for enlar-
ging both the mouth and cavity of the nofe. The
upper part of its internal edge rifes in a fpine, after
the fame manner as the palate-plate of the maxillary
bone does, to be joined with the vomer. — Its anterior
edge is unequally ragged, for its firmer connection
with the palate procefs of the os maxillare. — The in-
ternal edge is thicker than the reft, and of an equal
furface, for its conjuhftion with its fellow of the o-
ther fide. — Behind, this bone is fomewhat in form of
a crefceni, and thick, for the firm connexion of the
velum pendulum palati ; the internal point being pro-
duced backwards, to afford origin to the palatc-flaphy -
linns or azygos mufcle. — This fquare bone is well di-
ftinguifhed from the pterygoid procefs by a perpendi-
cular fojpi, which, applied to fuch another in the
maxillary bone, forms a paffage for the palatine branch
of the fifth pair of nerves ; and by ano.ther fmall hole
behind this, through which a twig of the fame nerve
pafi'es.

The pterygoid procefs is fomewhat triangular, hav-
ing a broad bafe, and ending fmaller above. The
back-part of this proqefs has three fojfe formed in it;
the two lateral receive the ends of the two plates of
the fphenoid bone, that are commonly compared to a
hat’s wing ; the middley^^ makes up a part of what
is commonly called thej^ri pteryge)idia\ the fore-Gde
of this palatine pterygoid procefs is an irregular con-
cave, where it receives the back-part of the great tu-

beroftty of the maxillary bone. Frequently feveral

fmall holes may be obferved in this triangular prb-
cefs, particularly one nefar the middle ’of ij^s bafe,
which a little above communicates with the common
and proper holes of this bone already taken no-
tice of.

The nafal lamella of this bone is extremely thin
and brittle, and rifes upwards from the upper fide of
the external edge of the fquare bone, and from the
narrow extremity of the pterygoid procefs ; where it
is fo weak, and, at the fame time, fo firmly fixed to

the.

104

Of tite SKELETO N.

the maxillary hone, as to be very liable to be broken-
in feparating the bones. — From the part where the
plate rifes, it runs up broad on the infide of the tube-
rqfity of the maxillary bone, to form a confiderable
(bare of the Tides of the maxillary Jim/s, and to clofe
up the fpace between the fphenoid and the great bulge
of the maxillary bone, where there would otherwife
be a large flit opening into the noftrils (/). From the
middle internal fide of this thin plate, a crofs-ridge
placed on fuch another of the maxillary bone is-
extended ; on it, the back-part of, the os fpongiofum.
inferius refts. — Along the outfide of this plate, the
perpendicular fojfa made by the palate nerve is ob- >
fervable.

At the upper part of this nafal plate, the palate-
bone divides into two procefles, which I already nam-
ed orbitar ; — between which and the body of the fphe-
noid bone, that hole is formed, which I mentioned as

the lad of the holes common to the fphenoid bone.

Sometimes this hole is wholly formed in the os palatiy ,
by a crofs plate going from the one orbitar procefs to
the other. A nerve, artery, and vein belonging to
the noftrils pafs here. — The anterior of the two orbi-
tar procefles is the largeft, and has its fore-part con-
tiguous to the back-part of the maxillary fnus , and
its upper furface appears in the bottom of the orbit,
behind the back-part of the os maxillare and planum. —

It has cells behind, refembling thofe of the eth-
moid bone, to which it is contiguous ; it is placed on
the aperture of the Jinus fphenoidalisy fo as to leave
only a round hole at its upper fore-part. — The other
part of the orbitar procefs is extended along the in-
ternal fide of the upper back-part of the maxillary
tuberqfity, to the bafe of the fphenoid bone, between
the root of the procejfus azygos and the pterygoid pro-
cefs.

The palate fquare part of this palate-bone, and its-
pterygoid procefs, are firm and ftrong, with fome

cancelli j

(/) Altjiji, <Je oflib. § 88.

Of the SKELETON. 105

canceili; but the nafal plate and orbitar procefles are
very thin and brittle.

The palate-bones are joined to the maxillary , by
the fore-edge of the palate fquare-bone, by the tranj-
verfe palate future : — By their thin nafal plates, and
part of their orbitar procefles, to the fame bones, by
the palato-maxillares futures : — By their pterygoid pro-
cefles, and back-part of the nafal plates , to the alz
vefpertilionum, by the fphenoid future : — By the tranf-
verfe ridges of the nafal plates, to the offa fpongiofa
inferior a , by conta£t ; hence frequently there is an
intimate union of the fubftance of thefe bones in old
fculls : — By the orbitar procefles, to the offa plana and
celluLz ethmoidexy by the ethmoid future : — To the body
of the fphenoid bone by the fphenoid future : — By the
internal edge of the fquare bones, to each other, by
the longitudinal palate future •, and by their nafal
fpines, to the vomer , by the fpinous future.

The palate-bones form part of the palate, noftrils,
orbits, and foffee pterygoidex, and they cover part of
the firms maxillares , fphenoidales , and ethmoidei.

Thefe bones are very complete in a new-born in-
fant, the nafal plates being then thicker and ilronger
than in adults *, but the orbitar procefles have not the
cells which appear in the bones of adults.

When we are acquainted with the hiftory of thefe
bones, the reafon is evident, why the eyes are fo
much affefted in ulcers of the palate, as to be often
attended with blindnefs, which frequently happens in
an ill-managed lues venerea ; or why, on the other
hand, the palate fuffers from an eegylops ( m ).

OSSA TURBIN AT A, or fpongiofa inferiora , re-
femble the fuperior offa fpongiofa in fhape and fub-
flance, but have their anterior and upper edges con-
tiguous to the tranfverfe ridges of the nafal procefles

of the maxillary and palate hones. From their upper

ftraight edge, two fmall procefles Hand out : the poste-
rior, which is the broadeft, defcends to cover fome of
the antrum Highmorianum ; the anterior rifes up to

join

(«) Hoffman in Ephcmcrid. German, cent. I. and a. obferv. 13.5.

io6 Of the SKELETON.

join the os unguis , and to make part of the lacrymai
tluEl.

Below the fpongy bones already mentioned, there
are fometimes two others, one in each noftril, which
feem to be a produftion of the fides of the maxillary
ftnus turned downwards («). Wlien this third fort of
fpongy bones is found, the middle one of the three
in each nodril is the larged, and the lowed is the
fmalled. — Befides all thefe, there are often feveral o-
ther fmall bones danding out into the nodrils, that,
from their fhape, might alfo deferve the name of
turbinata , but are uncertain in their bulk, fituation,
and number (c).

The names of thefe bones fufficiently declare their
fpongy fubdance, which has no firm external plate
covering it.

They are joined to the ojfa maxillaria palati , and
unguis in old fubjects, by a firm union of fubdance :
And as this happens alfo frequently in people of no
great age, fome (/>) are of opinion, that they fhould
be edeemed part of the palate-bones ; others (7)
-think, that fince their upper edge is continued by a
plate to a part of the os ctkmoides , they ought to be e-
fteemcd to be a part of this bone.

Their ufe is, to draiten the nodrils, to afford a
largo furface for extending the organ of fmelling, to
cover part of the antra maxiltaria , and to aflid in
forming the under part of the lacrymal duffs, the
orifices of which into the nofc are concealed by thefe
•bones.

The oJa turbinata are nearly complete in a new-
born infant.

VOMER, or bone refembling a plough-fhare, is
the thirteenth of the upper jaw, without a fellow,
forming the lower and back parts of the partition of
the nofe (r).

The

(») Covper in Drake’s Anthropolog. book 3- chap. TO.

(0) Santorin. Obfcrvat. anatomic, cap. 5. § 9.

iP) Id. ibid. cap. 5. § 7.

( q ) Hunauld Mcmoires de l’acad. dcs kicnccs, 1 730>

(r) Columb. dc re anat. lib. I. cap. 8. — Fallop. Oblirvvat anatom.

Of the SKELETON.

lot

. The figure of this bone is an irregular rhom-
boid.— Its fides are flat and fmooth. — Its pofterior
edge appears in an oblique direction at the back-part
of the noftrils. — The upper one is firmly united to
the bafe of the fphenoid bone, and to the nafal plate
of the ethmoid ; and, when ft can be got feparated,
is hollow, for receiving the procejfus azygos of the
fphenoid. — The anterior edge has a long furrow in it,
where the middle cartilage of the nofe enters. — The
lower edge is firmly united to the nafal fpines of the
maxillary and palate bones. — Thefe edges of this
bone are much thicker than its middle, which is as
thin as the fineft paper ; by which, and the firm u-
nion or connection this bone has above and below,
it can very feldom be feparated entire in adults : But,
in a child, it is much more eafily feparated entire,
and its ftru&ure is more diflin&ly feen : Wherefore
I fhall examine all its parts of fuch a fubjeft.

Its fituation is not always perpendicular, but often
inclined and bended to one fide, as well as the nafal
plate of the ethmoid bone.

The vomer is convex at its upper part, and then is
ftraight, as it is extended downwards and forwards,
where it is compofed of two plates ; the edges of
which have a great number of fmall procefles, dif-
pofed fomewhat like the teeth of a faw, but more ir-
regularly, and feveral of them are reflected back.
Between thefe plates a deep fojfa is left, which, fo far
as the top of the curvature, is wide, and has ftrong
fides, for receiving the procejfus azygos of the fphenoid
bone. Beyond the arch forwards, the fojfa is nar-
rower and fhallower gradually to the point of the
bone, receiving for feme way the nafal lamella eth -
moidea; which, after the ofiification is complete, is
fo clofely united to the vomer by the little procefles
piercing into its fubftance, as to prevent any fepara-
tion •, on which account, it has been efteemed by
fome (s) a part of the ethmoid bone. The middle
cartilage of the nofe fills up what remains of the

/#

(r) Lieutaud. ElTais anatomiques I. fe£t, l’os ctLmcidc.

io8 Op the SKELETON.

fcjja at its fore-part. — Tlie pofterior edge of the w-
mery which appears above the back-part of the palate
bones, is broader above ; but as it defcends forwards,"
becomes thinner, though it is ftill folid and firm. —
The lower edge of this bone, which refts on the na-
fal fpine of the palate and maxillary bones, has a lit-
tle furrow on each fide of a fmall middle ridge, an-
fwering to the fpines of the bones of different fides,
and the interffices between them. This edge, and
the upper one, meet in the pointed fere-end of this
bone.

The body of the vomer has a fmooth furface, and
folid, but thin fubftance ; and towards its fides, where
it is thickeff, fome cancelli may be obferved, when the
bone is broken.

It is joined above to the fphenoid and cthmoidbones,
and to the middle cartilage of the nofe by fchyndele-
fis ; — below, to the maxillary and palate bones, by
the fpinous future.

The vomer divides the noftrils, enlarges the organ
of fmelling, by allowing place for expanding the
membrane of the nofe on its fides, and fuftains the
palate-plates of the maxillary and palate bones,
which otherwife might be in hazard of being prefled
into the noftrils ; while the vomer is fecured from
(huffling to one fide or other by the double fchyndclc-
ftSy by which it is joined to the bones above and be-
low.

Thefe, then, are all the bones which compofe the
upper jaw, except the teeth, which are fo much akin
to thofe of the lower jaw, that I choofe to make one
defeription ferve for both, in which the differences
obfervable in them fhall be remarked, after the fe-
cond part of the face, the lower jaw, is examined ;
becaufe the ftru&ure of the teeth cannot be well
underftood, until the cafe in which they are fet is ex-
plained.

MAXILLA INFERIOR (t), the lower jaw, con— i

fills

(/) Tr V0t, o-/«y»y, mandibula, fades.

fifts only of one moveable bone, and fixteen teeth in-
cafed into it.

This bone, which is fomewhat of the figure of the
Greek letter is fituated at the lower part of the
face, fo as its convex middle part is forwards, and its
legs are ftretched back. It is commonly divided into
the chin, fides, and proceffes. — The chin is the mid-
dle fore-part, the extent of which to each Gde is
marked on the external furface by the holes obferv-
able there, and internally by the beginning of an ob-
lique ridge. — Beyond thefe the j ides appear, and are
continued till the bone, by bending upwards, begins
to form the proceffes.

On the fore-part of the chin, a tranfverfe ridge ap-
pears in the middle, on each fide of which the mufcu~
li quadrati , or deprejfores iahii inferiority and the leva-
tores Iahii inferiority deprefs the bone : And below
thefe prints, a fmall rifing may be obferved, where
the deprejfores commence. — On the back-part of the
chin, fometinies three, always two, fmall protube-
rances appear in the middle. To the uppermoft,
when it is feen, the franuin of the tongue is con-
nected. From the middle one, the mufeuii genio-g/of-
fi rife ; and from the lowelt, the genio-hyoidei have their
origin. Below the laft, we fee two rough finuofities
formed by the diga/iric mufcles.

At the lower and fore-part of the external furface
of each fide of the lower jaw, a fmall eminence may
be obferved, where the deprejfor labiorum communis
rifes. Near the upper edge of the fide, a ridge runs
length-ways, to which the under-part of the mufculus
buccinator is connedted. — Internally, towards the up-
per edge of each fide, another ridge appears, from
which the tnylo-hyoidei have their origin, and to which
the internal membrane of the gums adheres.

In the upper edge of both chin and fides are z
great many deep pits or fockets, for receiving the
roots of the teeth. The number and magnitude of
thefe fockets are various, becaufe of the different
number, as well of the teeth themfelves, as of their

K , roots,

r io

Of the skeleton.

roots, in different people. Thefe fockets in this
lower jaw, as well as in the upper one, are Jefs deep
as old age comes on •, when freed from the teeth by
any means, they are fome time after filled up with
an offeous net-work, which at laft becomes entirely
folid, and as fmooth as any other part of the bone ;
fo that in a great many old jaws, one cannot obferve
a veftige of the fockets: But then the jaw becomes
lefs, and much narrower (r<). — Hence we may know
why the chin and nofe of edentulous people are much
nearer than before the teeth were loft; while their
lips either fall in towards the mouth, or (land promi-
nent forwards. — When new teeth are protruded, new
fockets are formed (at). — The lower edge of the chin
and fides is fmooth and equal, and is commonly call-
ed the bafe of the lower jaw. — The ends of the bafe,
where the jaw turns upwards, are called its angles;
the external furface of each of which has feveral in-
equalities upon it, where the majfeter mufcle is in-
ferted ; as the internal furface alfo has, where the
pterygoideus internus is inferred, and a ligament ex-
tended from the Jlyloid procefs of the temporal bone
js fixed.

The proceffes are two on each fide. — The anterior
fharp thin corotioid ones have the crctaphyte mufcles
inferted into them. — The pofterior proceffes or con-
dyles (y) terminate in an oblong fmooth head, fup-
ported by a cervix. The heads, whofegreateft length
is tranfverfe, and whofe convexity is turned forwards,
are tipped with a cartilage, as the articulated parts
of all other moved bones are. — The fore-part of the
root and neck of thefe condyloid proceffes are a little
hollow and rough, where the external pterygoid muf-
cles are inferted.

The holes of the lower jaw are two on each fide;
one at the root of the proceffes internally, where a
large branch of the third branch of the fifth pair of

nerves

(a) Vefal. Anat. lib. I. cap. IO,
(at) Fallop. Obferv. anat.

(yj Articulatorii.

Of the SKELETON. mi

nerves enters with an artery, and a vein returns. A
fmall fhaip procefs frequently juts out backwards
from the edge at the fore-part of this hole, to which
a ligament extended from the temporal bone is fixed
( y ), which faves the nerve and veflels from being
too much prefled by the pterygoid mufcles. — From the
lower fide of this hole, either a fmall fuperficial ca-
nal or a furrow defeends, where a branch of the
nerve is lodged, in its way td the mylo-hyoideus
mufcle and fublingual gland The other hole is

external, at the confines of the chin, where branches
of the nerve and veflels come out. — The canal be-
twixt thefe two holes is formed in the middle of the
fubftarice of the bone, and is pierced by a great num-
ber of fmall holes, by which the nerves and blood-
vefiels of the cancelli and teeth pafs. — This canal is
continued a little further than the external hole at
the chin. — On account of the veflels and nerves- in
the lower jaw, fradhures of it may be attended with
dangerous fymptoms.

The furface of the lower jaw is hard and firm, ex-
cept at the fpongy fockets, where however it is ftronger
than the upper jaw. — Its internal fubftance is cellular,
without any folid partition between the cancelli in its
middle. — At the bafe, efpecially of the chin, where
this bone is molt expofed to injuries, the folid fides
of' it are thick, compadh, and hard.

The lower jaw generally receives the roots of fix-
teen teeth into its fockets, by gompheju ; and its con-
dyloid procefles, covered with cartilage, are articulated
with the temporal bones, in a manner that is not com-
monly deferibed right : For, as was already mentioned
in the defeription of the temporal bones, not only the
fore-part of the cavity between the zygomatic , auditory ,
and vaginal procefles, but alfo the adjoining tubercle at
the root of the zygomatic procefs of each os temporum is
covered with a fmooth cartilage, for this articulation.
Here alfo an intermediate moveable cartilage is pla-

K 2 ced,

(y) Weitbrecht Sy ndcfmolog. fig. 32. r.

(x) Palfyn. Anat. cbirur. traite j. chap. 6.

1 11

Of the SKELETON.

ced, which being thin in the middle, and thick at the
edges, is concave on both Tides ; and is connected To
firmly by ligaments to each condyle , as to follow the
motions of the condyle ; and fo loofely to the temporal
bone, as readily to change its fituation from the ca-
vity to the tubercle, and to return again ; while the
common ligament of the articulation affords fpace e-
nough for fuch a change of place backwards and
forwards; but, like other ligaments of the joints by
ginglimus, is ftrong and fbort at the fide3, to confine
the lateral motions.

When therefore the teeth of both jaws coincide,
the condyles are lodged fecurely in the temporal cavi-
ties, but their motions to either Tide muff be- confin-
ed both by the firmnefs of the ligaments, and the
riling brims which are on each fide of the cavities. —
When the jaw is brought dire£Uy forwards, the con-
dyle and intermediate cartilages dcfcend and advance
forwards upon the tubercles. — In this fituation the
lateral motions are a little more free than in the for-
mer one, from the want of rifing brims to flop the
condyles. — When the fore-teeth of the lower jaw are
moved forwards, and to a fide, the condyle of the
oppofite fide is either advanced from the cavity to the
tubercle, while the condyle of the fame fide remains
in the cavity ; or if both condyles are on the tu-
bercles, when the jaw is moved obliquely to a fide,
the condyle of the fide to which the motion is made,
Hides back from the tubercle to the cavity — When
the mouth is opened by the defeent of the lower jaw,
the fore-part of it, where the dcprejjing mufcles are
fixed, is drawn backwards, as well as downwards,
while refinance is made to the angles moving back-
wards by the majjeter and internal pterygoid mufcles,
and, at the fame time, the external pterygoid draw the.
condyles and their moveable cartilages forwards ; and
therefore, when the mouth is opened, the condyles
are carried forwards upon the tubercles, and the axis
of motion of the bone is a little above its angles.
But in this fituation there is lefs refinance than in

any

Of the SKELETON.

”3

any other, to the condyles luxating forwards ; a dif-
eafe which feldom happens, except when people are
gaping too wide j and therefore the common pradtice
of nurfes, who fupport the jaw of infants when they
are yawning, is reafonable. — In chewing there is a
fuccefiion of the rations above defcribed (a).

Here a general remark may be made, That w'here-
ever moveable cartilages are found in joints, either
the articulated bones are of fuch a figure, or fo join-
ed and fixed by their ligaments, that little motion
would be allowed without fuch cartilages ; or elfe
fome motions are neceffary to the right ufe of the
member, which the form of the articulation would,
not otherwife admit of. This will more fully appear
after the other joints with fuch cartilages are de-
fcribed.

In a child born to the full time, the low-er jaw is
compofed of two bones, connected by a thin carti-
lage in the middle of the chin, which gradually ofli-
fies, and the two bones intimately unite. — In each of
thefe bones there are five or fix fockets for teeth, as in
the upper jaw.

After I have thus defcribed the incafement of the
teeth, the infertion of fo many mufclesof the tongue,,
and of the os hyoides , the connection of the mem-
brane of the tongue to the maxillary bone, and the
motions of this bone ; it is eafy to fee, that the lower
jaw mult be a principal inftrument in manducation,
deglutition, and fpeech.

The TEETH are the hard white bodies placed in
the fockets of both jaws. Their number is general-
ly fixteen above, and as many below j though fome
people have more, others have fewer.

The broad thick part of each tooth which appears
without the focket, is the bafe or body (b). — The
fmaller procefles funk into the maxilla: , are the roots

K 3 or

(a) For a more full account of this articulation, vide Edinburgh
Medical E flays and oblerv. xol. I. art, XI, and vol. 3. art. 13. —
Memcircs de l’acad, des fcicnces, 1744.

(!’) Coronal

1 14 Of the SKELETON.

or fangs, which become gradually fmaller towards the
end fartheft from the bafe, or are nearly conical, by
which the ftirface of their fides divides the preffure
made on the bafes, to prevent the foft parts, which
are at the fmall points of the fockets, to’ be hurt by
fuch preflure. — At the place where the bafe ends,
and the roots begin, there is generally a fmall circu-
lar depreflion, which fome call the neck or collar.

"Without the gums, the teeth are covered with no
membrane, and they are faid to have no proper perio-
Jleum within the fockets •, but that is fupplied by the
refle£led membrane of the gums ; which, after a
good injection, mav be evidently feen in a young
fubject, with the veffels from it penetrating into the
fubftance of the teeth •, and it may be difcovered in
any tooth recently pulled, by macerating it in wa-
ter (r). The adhetion of this membrane to thefe
roots is ftrengthened by the fmall furrows obfervable
on them.

Each tooth is compofed of its cor/ex, or enamel ,
and an internal bony fubftance. The cortex has no
cavity or place for marrow ; and is fo folid and hard,
that faws or files can with difficulty make imprelfion
on it. It is thickeft upon the bafe, and gradually,
as the roots turn fmaller, becomes thinner, but not
proportionally to the difference of the fize of the bafe
and roots. — The fibres of this enamel are all perpen-
dicular to the internal fubflance, and are ftraight on
the bafe, but at the fides are arched with a convex
part towards the roots ( d ) ; which makes the teeth
refill the compreffion of any hard body between the
jaws, with lefs danger of breaking thefe fibres, than
if they had been fituatcd tranfverfely. The fpongy
fockets in which the teeth are placed, likewife ferve
better to prevent fuch an injury, than a more folid
bafe would have done. — Notwithflanding the great
hardnefs of this cortex , it is wafted by manducation.

Hence

(c) Cowper Anatom, explicat. tab. 93, fig. 7. lit, E,

(d) Haver’s Oftcoloj. nov. dife. 1.

Of the SKELETON.

**S

Hence the {harp edges of fome teeth are blunted,
and made broad, while the rough furfaces of others
are made fmooth and flat, as people advance in life.

The bony part of the teeth has its fibres running
ftrnight, according to the length of the teeth. When
it is expofed to the air, by the breaking or falling off
of the hard cortex , it loon corrupts. And thence ca-
rious teeth are often all hollow within, when a very
ftnall hole appears only externally.

The teeth have canals formed in their middle,
wherein their nerves and blood-veflels are lodged ;
which they certainly need, being conftantly wafted
by the attrition they are fubje&ed to in manduca-
tion, and for their further growth, not only after
they firft appear, but even in adults ; as is evident
when a tooth is taken out : For then the oppofite one
becomes longer, and thofe on each fide of the empty
focket turn broader ; fo that when the jaws are
brought together, it is fcarce obfervable where the
tooth is wanting (a).

The veflels are eafily traced fo long as they are in
the large canal, but can fcarce be obferved in their
diftribution from that to the fubftance of the teeth of
adults. Ruyfch (£) however affirms, that after injec-
tion, he could trace the arteries into the hardeft part
of the teeth : And Leewenhoek (r) fufpefted the fi-
bres of the cortex to be veflels. In children I have
frequently inje&ed the veflels of the teeth as far as
their bafe : And in fuch as are not intirely offified,
one can with a lucky injection fill fo many veflels, as
to make both the outfide and infide of the cortical
part appear perfe&ly red. — This plentiful fupply of
veflels muft expofe the teeth to the fame diforders
that attack other vafcular parts ; and fuch teeth as
have the greateft: number of veflels, muft; have the
moft numerous chances of being feized with thefe
difeafes.

Every root of each tooth has fuch a diftinft canal,

with

0) Ingraf. de tumor, cap. i. p. 24. 15. 26.

( b ) Thefaur. 10. num. 27.

(c) Arcan. natur. continual, epifl. p. 3.

ii 6 Of the SKELETON.

with vefl'els and nerves in it. Thefe canals in the
teeth with more than one root, come nearer each o-
ther, as they approach the bafe of the tooth ; and at
laft are only feparated by very thin plates, which be-
ing generally incompleat, allow a communication of
all the canals ; and frequently one common cavity
only appears within the bafe, in which a pulpy fub-
ftance compofed of nerves and vefl'els is lodged. The
condition therefore of the nerves here, bears a ftrong
analogy to that of the cutaneous nerves which ferve
for the fenfation of touching.

The entry of the canals for thefe vefl'els is a fmall
hole placed a little to a fide of the extreme point of
each root ; fometimes, efpecially in old people, this
hole is entirely clofed up, and confequently the nerves
and blood-veffels are deftroyed (d).

The teeth are feen for a confiderable time in form
of mucus contained in a membrane, afterwards a thin
cortical plate, and fome few ofleous layers appear
within the membrane, with a large cavity filled with
mucus in the middle ; and gradually this exterior {hell
turns thicker, the cavity decreafes, the quantity of
mucus is leflened, and this induration proceeds till all
the body is formed ; from which the roots are after-
wards produced.

In young fubje&s, different Jiamina or rudiments
of teeth are to be obferved. Thofe next the gums
hinder ordinarily the deeper feated ones from making
their way out, while thefe prevent the former from
fending out roots, or from entering deep into ’the bo-
ny fockets of the jaws ; by which they come to belefs
fixed.

Children are feldom born with teeth •, but at two
years of age they have twenty ; and their number
does not increafe till they are about feven years old,
when the teeth that fii ft made their way through the
pums are thrufl: out by others that have been formed
deeper in the jaw, and fome more of the teeth begin
to difeover themfelves farther back in the mouth. ,

About

(J) De la Hire Hiftoire de L’acad. dcs fciences,

Of the SKELETON. 117

About fourteen years of age, fome more of the firfl
crop are ffied, and the number is increafed. — This
fhedding of the teeth is of good ufe ; for if the firffc
had remained, they would have ftood at a great dis-
tance one from another ; becaufe the teeth are too
hard in their outer cruft, to increafe fo faft as the
jaws do. Whereas both the fecond layer, and the
teeth that come out lace, meeting, while they are
foft, with a confiderable refiftance to their growth iu
length, from thofe fituated upon them, neceffarily
come out broad, and fit to make that clofe guard to
the mouth ( e ), which they now form.

The teeth are joined to the fockets by gotnphofts, and
the gums contribute to fix them there ; as is evident
by the teeth falling out when the gums are any way
deftroyed, or made too fpongy ; as in the fcurvy or
falivations : whence fome (g) clafs this articulation
with the fyffarcofis.

The ufes of the teeth are to mafticate our aliment,
and to aflift us in the pionunciation of feveral let-
ters.

Though the teeth fo far agree in their ftru£lure,
yet, becaufe of fome things wherein they differ, they
are generally divided into three clafTes, viz. incifores ,
caniniy and molares.

The incifores (h) are the four fore-teeth in each jaw,
receiving their name from their office of cutting our
aliment j for which they are excellently adapted, being
each formed into a {harp cutting edge at their bafey
by their fore-fide turning inwards there, while they
are Hoped down and hollowed behind (i) ; fo that
they have the form of wedges ; and therefore, their
power of acting muft be confiderably increafed. — ■
Seeing in the action of the incifores , a perpendicular
comprtffiqn is only necelfary, without any lateral
motion, they are not fo firmly fixed in their fockets

as

(r) frpayy-tc-

(g) Drake’s Anthropolog. book 4. chap. 3.

{k) T Toy.ix.n, Topitit^ rpotxrBtfi,

niorii, quaterii, prinii, primores, antcriorcs, acuti.

(>)

1 1 8 Of the SKELETON.

as the other teeth are, each having only one fhort
root, but that is broader from before backwards, than
to either fide, to have the greatefl flrength where it
is expofed to the ftrongeft force applied to it (£).

The incifores of the upper jaw, efpecially the two
middle ones (/), are broader and longer generally than
thofe of the under jaw.

In a new-born infant, the outer fheli of the body
of thefe teeth is only hardened. — Afterwards, when
the Jiamina of two fets are formed, each has its own
focket, thofe neareft to the edge of the gums being
placed more forward, and the others are lodged far-
ther back within the jaw-bones.

Canini (m), from the refemblance to dogs tufks,
are one on each fide of the incifores in each jaw. —
The two in the upper jaw are called eye-teeth , from
the communication of nerves which is faid to be be-
twixt them and the eyes — The two in the lower jaw
are named angular or ivike-teeth, becaufe they fupport
the angles of the mouth.

The canini are broader, longer, and ftronger, than
the incifores. — Their bafes are formed into a fharp
edge, as the incifores are ; only that the edge rifes in-
to a point in the middle. — Each of them has gene-
rally but one long root, though fometimes they have
two («). The roots are crooked towards the end. —
The canini of the upper jaw are larger, longer, and
with more crooked roots, than thofe of the under
jaw. — The form of their bafe is fit both for piercing
and cutting, and the long crooked root of each makes
it fecure in the focket.

The canini of a child are in much the fame condi-
tion as the incifores are.

The dentes molares, or grinders (o), which have got
their name becaufe they grind our food, are general-

(k) Lettre fur l’ofteologie, aferibed to Du Vcrney.

(/) Duales.

(m) KuhJovtjc, riforii, fraftorii, collateralcs, collamellares.

(*) Fauchard, Chirurgien dentifte, chap. I.

(e) y.u\oi, ' fl'XdTsic, fpxfvpiCi maxillarcs, mea-

Gilcs, clavales, buccarum.

Or the SKELETON. 119

ly five in each fide of each jaw; in all twenty. Their
bafes are broader, more fcabrous, and with a thinner
cortical fubftance, than the other teeth. They have
alfo more roots, and as thefe roots generally divari-
cate from each other, the partitions of the fockets
between them bear a large fliare of the great preffure
they fuffer, and hinder it to a£l on their points (/>).

The bafe of the firfh grinder has an edge pointed
in the middle, on its outfide, refembling the catiitii ;
from which it Hopes inwards till it rifes again into a
point. — It has generally but one root, which fome-
times is long and crooked at its point.

The fecond dens molaris has two points on its bafe,
rifing near equally on its out and infide. — It has two
roots, either ieparate or run together, but Ihorter than
the root of the firft. — Thefe two anterior grinders are
much fmaller than the three that are placed farther
back in the mouth.

The third and fourth are very broad in their bafes,
with four or five points Handing out ; and they have
three or more roots.

The fifth, called commonly dens fapientiee ( q ), from
its coming through the gums later than the other
grinders, has four points on its bafe, which is not
io large as the bale of the third and fourth, and its
roots are lefs numerous.

The incifores of the upper jaw, being broader than
thofe of the lower jaw, make the fuperior grinders to
be placed fo much farther back than the lower ones,
that when they are brought together, by {hutting the
mouth, the points of the grinders of the one jaw en-
ter into the depreffions of the oppofite grinders, and
they are all equally applied to each other, notwith-
ftanding the inequality of their furface.

The numerous roots of the dentes molares prevent
their loofening by the lateral preflure they fuffer in
grinding; and as the fockets in the upper jaw are

more

(p) I.ettre fur rofteologie.

(?) xpavT»ip«f, •4-ryovot, fenfus, intellettus, ferotini,

KUtem complcntes, genuiiji, moderatores.

120

Of the SKELETON.

more fpongy, and the teeth are more liable, by their
(ituation, to fall out (r), the grinders there have more
numerous and more feparated roots than in the lower
jaw (j). The number however of the roots of the
teeth of both jaws is very uncertain ; fometimes they
are more, fometimes fewer •, frequently feveral roots
are joined together -, at other times they are all dif-
tin£L The difpofition of fuch as are diftind is al[o
various ; for in fome the roots (land out flraight, in
others they feparate, and in others again they are
crooked inwards. When the roots are united, we
can ftill diftinguiih them, by remarking the number
of fmall holes at their points, which determine the
number of roots each tooth ought to be reckoned to

have. * ,

At the time of birth only two dentes molares in

each jaw have begun to oflify, and that at little more
than the bafe which has feveral (harp points (land-
ing out from it.— The temporaneous grinders are
placed more diredly upon the internal fet than the
other two clafles are •, fometimes there is a piece of
the bone of the jaws between the two fets ; in other
children, the two fets have no bone interpofed be-

tween them. . ,

From what has been faid, the anfwers to the follow-
ing queries may be given. .

vVhy are children fubjeft to fahvation, fever, con-
vulfion, vomiting, purging, &c. when their teeth

are breeding or cutting the gums . ,

Why in children do the dentes incifores hrit cut the
gums, the canini next, and molares lad?

Why do children (hed their teeth ?

Wherefore have thefc temporaneous teeth generally

no roots, or very fmall ones ? _

Why have thefe firft teeth fometimes roots, and
that more frequently in teeth pulled by art than in
thofe which are (bedded by nature (a) . ^

(r) Calen. de ofiib. cap. S-

(t) Fauchard. Chirurg. dent. chap. I.

(<) Fauchard. Chirurgien dcntifte, p. 7.

m

Of the SKELETON.

Why do thefe roots frequently come outwards
through the gums ?

Whence come butter or buck teeth ?

How do thefe teeth fometimes go into the natural
row with the others, after pulling a rotten tooth near
them ?

How have fome people got two rows of teeth in
one or both jaws (b) ?

Why do the teeth of old people loofen, and then
drop out entire ?

Whence arife the new fets of teeth which feveral
old people obtain (c) ?

Why are not the gums of toothlefs old people torn
by the hard foc^ets in chewing ?

Why are th<fte£th infenfible when flightly filed or
rafped ?

How come they to befenfible of heat or cold, to
be fet on edge by acids, or to give an uneafy fenfa-
tion when gritty or fandy fubilances are rubbed be-
tween them ?

Why does a perfon who has a pained tooth imagine
it longer than any other ?

What is the reafon of fome perfons dying convul-
fed, upon rafping or filing down an overgrown tooth (d) ?

How do the teeth break and moulder awav with-
out any pain in fome people, and not in others?

What parts are affetted in the tooth-ach ?

What are the caufes of the tooth-ach ?

May worms be reckoned among thefe caufes (e) ?

Why are the dentes molares moil fubjedl to that
difeafe ?

In what different manners ought the feveral clafles
of teeth to be extracted when fuch an operation is
Heceflary ?

Whence proceeds the violent obilinate hetnorrhagy

K which

(h) Blaf comment, ad Veiling. Syntagm. cap. i. 3.

(c) Hoffman, in Van Horn, microcofm. p. 38.

( d) Bartholin. Anat. reformat, lib. 4. cap. ia.

U) Jacob, in Aft. Hafn. vol. j. obf. 107. — Pechlin. Obferv. me-
dic. lib. 2. obf. 36. — Bartholin. Hid. medic, cent. 3. hid. 96.

122

Of' the SKELETON.

which fometimes attends the drawing of teeth (c) ?

Why is it more difficult and dangerous to draw the
eye-teeth than any other ?

What makes it impoffible frequently to draw £•/•/'/;-
ders without bringing away part of the jaw-bone with
them, or breaking the fangs ?

Why do teeth foon replaced after being extracted,
become again fixed in the fockets ( d ) ?

According to the divifion made of the flceleton, we
fhould now proceed to the defcription of the trunk
of the body. But mull firft confider a bone, which
cannot well be faid to belong to either the head or
the trunk *, nor is it immediately joined to any other,
and therefore is very feldom preferved with Ikeletons.
However, it is generally defcribecfrvby authors after
the bones of the face : In obedience therefore to the
prevailing method, I ffiall next examine the ftru&ure
of

The OS HTOIDES (e), which is fituated horizon-
tally between the root of the tongue and the larynx.
It is properly enough named hyoidcs, from the relem-
blance it bears to the Greek letter u, and may, for a
clearer demonftration of its ftrutfure, be diftinguilh-
cd into its /Wy, cornua , and appendices.

The body is the middle broad part, convex before,
and hollow behind. — The convex fore-part is divided
into two, by a ridge, into the middle of which the
mylo-hyoidei , and into the fides the Jlylo-byoidei, mul-
cles are inferted. — Above the ridge, the bone is hori-
zontal, but pitted in the middle by the infertion of
the two gcnio-hyoulei mufcles, and a little hollowed
more laterally by the bafto-glojfi. — Below the ridge, it
is convex, but a little flatted in the middle by the
Jhrno-hyoidei, and pitted more externally by the coraco-

hyoidei. —

(c) Pare, livre 6. chap. 2.— Rolfinc. lib. 2. cap. 27. ct 30. — Moe-
bii Fundam. median, cap. 9. — Ephemerid. German, dec. I. ann. 3.
obf. 319.— Faucb. Chirurg. dentifte, tom. I. chap. 23. obferv. 7.

( i ) De la Motte Chirurgie, tom. r. chap. 4. obf. 2. — Fauchard,
Chirurg ien dentifte, tom. I. chap. 29.

(e) Hypfyloid'es, Lambdoidcs, xapxiaTV, fK/niyyiripov, OS guttuns,
os lingua:, os morfus Adami, afleflbr, os laude, bicorne.

*23

Of the SKELETON.

byoidei.- — The concavity behind faces backwards and
downwards to receive the thyroid cartilage, when the
laru/x and the os hyoides are pulled towards each other
by the a&ion of the flerm~hyoidei and hyo-thyroidei
mufcles; and to its upper edge, the ligamentous
membranes of the epiglottis, tongue, and thyroid car-
tilage, are fixed.

The cornua of the (i) os hyoides are ftretched back-
wards from each fide of its body, where often a fmall
furrow points out the former feparation •, for in young
fubjedls, the body and cornua are not one continued
fubftance, as they come afterwards to be in adults. —
Thefe cornua are not always flraight, nor of equal
length; their two plain furfaces Hand obliquely Hop-
ing from above outwards and downwards. — Into the
external, the cerato-glojfus is inferted above, and the
thyro-hyoideus mufcle below ; and to the one behind,
the ligamentous membrane of the tongue and larynx
adheres. Each of the cornua becomes gradually fmall -
er, as it is extended from the bale ; but ends in a
round tubercle, from which a moveable cartilage Hands
out, which is connefred to the upper procefs of the
ca rti lago-thyroidta.

Where the body of the os hyoides joins on each fide
with its cornua , a fmall ftyliform proccfs, called
appendix (g), rifes upwards and backwards, into which
the mttfciiH fylo-hyoidei alteri , and part of the hyo-glojji
mufcles are fixed. From each of them a ligament is
fometimes extended to the Jlylcid precedes of the tem-
poral bones, to keep the os hyoides from being drawn
too much forwards or downwards. The part of this
ligament next to thefe proceiles fometimes forms into
feveral cartilages, which afterwards ofiify in old peo-
ple. Ruyfch (h) fays, that he has fecn this oifification
continued as far up as the ilyioid proceffes, which
were therefore joined to the os hyoides by archy lofts.

The fubftance of the os hyoides is cellular, but co-
vered with a firm external plate, which is of fufficient

L 2 ftrength

( i ) Crura, latera inferiora.

(g) Crura fuperiora, latera fuperiora, cfTa grar.iforrr.ia.

(A) Advcrf. auat. dec. 3. § 9.

124

Of the SKELETON..

flrength to bear the aftions of fo many mufcles as
are inferted into it.

It is not articulated with any bone of the body, ex-
cept by means of the mufcles and ligaments men-
tioned.

The ufe of the os hyoides, is to ferve as a folid le-
aver for the mufcles to aft with, in raifing or depref-
fing the tongue and larynx, or in enlarging and di-
minifhing the capacity of the fauces. .

At birth, this bone is in a cartilaginous date*, ex-
cepting a ftnall point of bone in the middle of its
body, and in each of the cornua. — The appendices
frequently remain cartilaginous many years.

OF THE TRUNK.

THE TRUNK confifts of the /pine, pelvis , and
thorax.

The SPINE (a) is the long pile of bones extended
from the condyles of the occiput to the end of the rump.
It fomewhat refembles two unequal pyramids joined
in a common bafe. It is not, however, ftraight ; for
its upper part being drawn backwards by flrong muf-
clcs, it gradually advances forwards, to fupport the
c [fophagus , veilels of the head, life. Then it turns
backwards, to make place enough for the heart and
lungs. It is next bended forwards, to fupport the
vifccra of the abdomen. It afterwards turns back-
wards, for the enlargement of the pelvis. And laft-
]y, it is reflefted forwards, for fuftaining the lowed
great gut.

The J'pine is commonly divided into true and falfe
vertebr * ■, the former conflicting the long upper py-
ramid, which has its bafe below ; while th esfalfe ver-
tebra make the fhorter lower pyramid, whole bafe is

ab°’,e- The

(a) V*#{ vutct ax«<6«, »/>« rvpO’% > <ra^r> tergura, hojninis Carina.

125

Or the SKELETON.

The TRUE FERTEBRM (b) are the twenty four
upper bones of the / pine , on which the feveral mo-
tions of the trunk of our bodies are performed ; from
which ufe they have juftly got their name.

Each of thefe vertebra is compofed of its body and
procefles.

The body is the thick fpongy fore-part, which is
convex before, concave backwards, horizontal and
plain in moil of them above and below. — Numerous
fmall holes, efpecially on the fore and back part of
their furface, give pafiage to their veffels, and allow'
the ligaments to enter their fubftance. — The edges of
the body of each vertebra are covered, efpecially at
the fore-part, with a ring of bone firmer and more
folid than the fubftance of the body any where elle.
Thefe rings feem to be joined to the vertebra in the
form of epiphyfesy but are alledged by fome (e) to be
the ligaments oflified. They are of great ufe in pre-
venting the fpongy bodies from being broken in the
motions of the trunk.

Between the bodies of each two adjoining vertebra ,
a fubftance between the nature of ligament and car-
tilage is interpofed ; which feems to confift of con-
centrical curve fibres, when it is cut horizontally ;
but when it is divided perpendicularly, the fibres ap-
pear oblique and decufl'ating each other ( d ) — 1 he
outer part of the intervertebral ligaments is the molt
folid and hard ; and they gradually become fofter till
they are almoft in the form of a glairy liquor in the
centre ; and therefore thefe fubftances were not im-
properly called mucous ligaments by the ancients (e).
The external fibrous part of each is capable of being
greatly extended, and of being comprefled into a ve-
ry fmall ipace, while the middle fluid part is fncom-
preflible, or nearly fo ; and the parts of this ligament

L 3 between

(i) ’Srpopif, crpopyyef, fpondvli, ofla orbiculata, ofla vertebrata,

verticula.

(c) Fallop. Obfervat. anatom.

(/) Blancard, Anat.. reform, cap. jz. — Wcitbrecht, Synddnso-
l°g. fc£t. 4. § ij.

W Galcu de ufu part. lib. £2. cap; 16,

126

Of the SKELETO N.

between the circumference and centre approach in
their properties to either, in proportion to their more
folicl or more fluid texture. The middle point is
therefore a fulcrum , or pivot , on which the motion of
a ball and focket may be made, with fuch a gradual
yielding of the fubftance of the ligament, in which-
ever direction our fpines are moved, as faves the bo-
dy from violent (hocks, and their dangerous con-
fequences (f). — This ligamento-cartilaginous fub-
ftance is firmly fixed to the horizontal furfaces of the
bodies of the vertebra, to conneft them, in which it
is affilted by a ftrong membranous ligament, which
lines all their concave furface, and by (till a ftrong-
er ligament that covers all their anterior convex fur-
face.

AVe may lay it down as a general rule, notwith-
ft a tiding fonte exceptions, That the bodies of the ver-
tebra are fmaller, and more folid above ; but as they
defeend, they appear larger and more fpongy ; and
that the cartilages between them are thick, and the
furrounding ligaments ftrong, in proportion to the
largenefs of the vertebra , and to the quantity of mo-
tion they perform : By which difpofition, the greater
weight is fupported on the broadeft bell fecured bafe,
and the middle of our body is allowed a large and fe-
cure motion.

From each fide of the body of each vertebra , a bo-
ny bridge is produced backwards, and to a fide ; from
the pofterior end of which, one flaming procefs rifes,
and another defeends ; the fmooth, and what is ge-
nerally the flatted fide of each of thefe four procefles,
which are called the oblique ( g ), is covered with a
fmooth cartilage ; and the two lower ones of each
vertebra are fitted to, and articulated with, the two
upper or afeending oblique procefles of the vertebra
below, having their articular ligaments fixed into the
rough line round their edges.

From

(/) Medical eflays and obferr. v*l, J. art 3?.
(g) Articulatorii, minimi.

127

Of the SKELETON.

From between the oblique procefles of each fide,
the vertebra is ftretched out laterally into a procefs
that is named travfverfe.

From the back- part of the roots of the two ob-
lique, and of the tranfverfe procefs of each fide, a
broad oblique bony plate is extended backwards ; where
thefe meet, the feventh proeefs of the vertebra takes
its rife, and Hands out backwards : This being gene-
ially fiiarp pointed and narrow edged, has therefore
been called fpinal procefs ; from which this whole chain
of bones has got its name.

Befides the common ligament which lines all the
internal furface of the fpinal procefTts, as well as of
the bodies, there are particular ligaments that con-
nett the bony bridges and procefles of the contiguous
-vertebra together.

The fabftance of the procefles is confiderably ftrong-
er and firmer, and has a thicker external plate than
the bodies of the vertebra have.

The feven procefles form a concavity at their fore-
part, which, joined to the one at the back-part of the
bodies, makes a great hole; and the holes of all the
vertebra form a long large conduit ( h), for contain-
ing the fpinal marrow . — In the upper and lower edge
of each lateral bridge , there is a notch. Thefe are fo
adapted to each other in the contiguous vertebra, as
to form a round hole in each fide between each two
vertebra , through which the nerves that proceed from
the fpinal marrow and its blood-veflels pals.

The articulations then of thefe true vertebra are
plainly double ; for their bodies are joined, by the
intervening cartilage above deferibed ; and their ob-
lique procefles being tipped with cartilages, are fo
connetted by their ligaments, as to allow a fmall de-
gree of motion to all fides. Hence it is evident, that
their centre of motion is altered in different pofitions
of the trunk : For when we bow forwards, the up-
per moved part bears entirely on the bodies of the
vertebra : If we bend back, the oblique procefles fup-

port

W Up* rvpyZ, reA; i», Caaalis.

123

Of the SKELETON.

port the weight : If we recline to one fide, we reft
upon the oblique procefies of that fide and part of the
bodies : If we ftand ereX, all the bodies and oblique
procefies have their fhare in our fupport.

Hence it follows, I. That becaufe the joints of
which the fpine is compofed are fo numerous, the fpi-
tial marrow, nerves, blood-vefiels, Zs V. are not liable
to fuch comprefiion and over-ftretching in the motion
of the trunk of the body, as they would otherwife be,,
fince feveral vertebra mull be concerned in every mo-
tion of the fpine ; and therefore a very fmall curva-
ture is made at the conjunXion of any two vertebra
(J). 2. That an ereX pofture is the fureft and firm-

eft, becaufe the furface of contact of the fulcra is
largeft, and the weight is moft perpendicular to them
( k ). 3. That the mufcles which move the fpine, act

with greater force in bringing the trunk to an ereX
pofture, than in drawing it to any other: for in bend-
ing forwards, backwards, or to a fide, the mufcles
which perform any of thefe aXions are nearer the
centre of motion \ confequently the lever with which
they aX is fhorter, than when the centre of motion
is on the part of the vertebra , oppofite to that where
thefe mufcles are inferted ; which is the cafe in raif-
ing the trunk. This is extremely neceflary ; fince, in
the defleXions of the fpine from a perpendicular
bearing, the weight of the body foon inclines it
which way we defign j whereas, in raifing us ereX,
this great weight muft be more than counteraXed.
4. In calculating the force exerted by the mufcles
which move the fpine, we fhould always make allow-
ance for the aXion of the cartilages between the ver-
tebrcey which, in every motion from an ereX pofture,
muft be ftretched on one fide, and comprefied on the
other, to both which they refill ; whereas, in raifing
the trunk, thefe cartilages aflift by their fpringy force
(/). 5. We are hence naturally led into the reafon

of

(i) Galen de ufu part. lib. 12. cap. ia.

( k ) Paaw dc ollib. par. a. cap. a.

(/) Borelli de motu animal, pars 1. fchol. ad propof. 58. — Fa~
rcat. liiftoirc de l’ avail, des fcicnces, 1702, : ;;j

129

Of the SKELETO N.

of our height of flature increafing in the morning,
and diminifhing at night (;;/) : for the intermediate
cartilages of the vertebra being preffed all day long
by the weight of our body, become more compact
and thin in the evening ; but when they are relieved
from this preffure in the night, they again expand
themfelves to their former thicknefs ; and feeing the
bulk of any part muft vary according to the different
diftenfion or repletion of the veffels compofing it, we
may underftand how we become taller after a plenti-
ful meal, and decreafe after faffing or evacuations
(«). 6. From the different articulations of the bo-

dies, and oblique proceffes of the vertebra , and the
different flrength of the ligaments, it is plain, that
they are formed fo as to allow much larger motion
forwards than backwards*, this lafl being of much
lefs ufe, and might be dangerous, by overftretching
the large blood-veffels that are contiguous to the bo-
dies of the vertebra (o). 7. The intervertebral carti-

lages fhrivelling as they become more folid by age, is
the caufe why old people generally bow forwards,
and cannot raife their bodies to fuch an ere£t poflure
as they had in their youth.

The true vertebra ferve to give us an ere£f poflure \
to allow fufficient and fecure motion to the head,
neck, and trunk of the body j and to fupport and de-
fend the bowels, and other foft parts.

At the ordinary time of birth, each vertebra con-
fifls of three bony pieces, connected by cartilages \
to wit, the body , which is not fully oflified, and a
long crooked bone on each fide : on which we fee a
fmall fhare of the bony bridge, the oblique procefTes
compleat, the beginning tranfverfe proceffes, ajid the
oblique plate, but no fpinal proceffes ; fo that the te-
guments are in no danger of being hurt by the fharp
ends of thefe fpinal procefTes, while a child is in its

bended

(in') Wafle Philofoph. tranfatt. numb. 383. art. I.

(«) Abbe Fontenu Hiftoirc de l'acad. des iciences, 1 725.
(e) Galen dc ulu part. lib. 1. cap. 46.

Of the SKELETON.

130

bended pofture in the womb, nor while it is fqueezed
in the birth.

From this general mechanifm of the fpine, an ac-
count is eafily deduced of all the different preterna-
tural curvatures which the fpine is capable of: for if
one or more vertebra, or their cartilages, are of un-
equal thicknefs in oppofite fides, the fpine muft be
reclined over to the thinner fide ; which now fuftain-
ing the greateft fhare of the weight, mufl flill be
more compreffed, confequently hindered from extend-
^ng itfelf in proportion to the other fide, which, be-
ing too much freed of its burden, has liberty to en-
joy a luxuriant growth. The caufes on which fuch an
inequality of thicknefs in different fides of the ver-
tebra depends, may vary : for, either it may be owing
to an over-diftenfion of the veffels of one fide, and
from thence a preternatural increafe of the thicknefs
of that part ; or, which more commonly is the cafe,
it may proceed from an obllruftion of the veffels, by
which tne application of proper nourifhment to the
bony fubftance is hindered, whether that obftru£lion
depends on the faulty difpofition of the veffels or fluids ;
or if it is produced by an unequal mechanical pref-
fure, occafioned by a paralytic weaknefs of the muf-
clcs and ligaments, or by a fpafmodic over-a£lion of
the mufcles on any fide of the fpine, or by people
continuing long, or putting themfelves frequently into
any pofture declining from the ere£t one : In all thefc
cafes, one common etfe£l follows, to wit, the vertebra ,
or their cartilages, or both, turn thick on that fide
•where the veffels are free, and remain thin on the 0-
ther fide where the veffels are ftraitened or obftrudted.
— Whenever any morbid curvature is thus made, a
fecond turn, but in an oppofite direction to the former,
mufl be formed ; both becaufe the mufcles on the
convex fide of the fpine being ftretched, mufl have
a ftronger natural contradlion to draw the parts to
which their ends are fixed, and becaufe the patient
makes efforts to keep the centre of gravity of the bo-
dy perpendicular to its bate, that the mufcles may be

relieved

Of the SKELETON. 131

relieved from aconftant violent contractile ftate, which
always creates uneafinefs and pain.

When once we underftand how thefe crooked fpines
are produced, there is little difficulty in forming a
juft prognofis ; and a proper method of cure may be
eafilv contrived, which muft vary as to the internal
medicines, according to the different caufes on which
the difeafe depends. But one general indication muft
be purfued by furgeons ; which is, to counteract the
bending force, by increafing the compreffion on the
convex part of the curvature, and diminiffiing it on
the concave fide ; the manner of executing which
in particular cafes muft be different, and requires a
very accurate examination of the circumftances both
of the difeafe and patient. In many fuch cafes, I
have found fome fimple directions, as to poftures in
which the patient’s body ffiould be kept, of very great
advantage.

Though the true vertebra agree in the general ftruc-
ture which I have hitherto defcribed ; yet, becaufe of
feveral fpccialities proper to a particular number, they
are commonly divided into three claffes, viz. cervical ,
dcrfaly and lumbar.

The cervical ( a ) are the feven uppermoft vertebra ;
which are diftinguiffied from the reft by thefe marks. —
Their bodies are fmaller and more folid than any others,
and flatted on the fore- part, to make way for the oefo-
phagus ; or rather this flat figure is owing to the pref-
fure of that pipe, and to the aCtion of the longi colli
and anterior reclt mufcles. — They are alfo flat behind,
where fmall proceffes rife, to which the internal liga-
ments are fixed. — The upper furface of the body of
each vertebra is made hollow, by a flaming thin pro
cefs which is railed on each fide : — The lower furface
is alfo excavated, but in a different manner ; for here,
the poflerior edge is raifed a little, and the one before
is produced a confiderable way. — Hence we fee how
the cartilages between thofe bones are firmly con-
nected, and their articulations are fecure.

The

(«) avgyi;, colli.

I32

Of the SKELETON.

The cartilages between thefe. vertebra are thick, e-
fpecially at their fore-part ; which is one reafon why
the vertebra advance forward as they defcend, and
have larger motion.

The oblique procefles of thefe bones of the neck
more juflly deferve that name than thofe of any other
vertebra. They are fituated flanting ; the upper ones'
having their fmooth and almoft flat furfaces facing o-
bliquely backwards and upwards, while the inferior
oblique procefles have thefe furfaces facing obliquely
forwards and downwards.

The tranfverfe procefles of thefe vertebra are fram-
ed in a different manner from thofe of any other
bones of the fpine : For, befides the common tranf-
verfe procefs rifing from between the oblique procef-
fes of each fide, there is a fecond one that comes out
from the fide of the body of each vertebra \ and thefe
two procefles, after leaving a circular hole for the paf-
fage of the cervical artery and vein, unite, and are
confiderably hollowed at their upper part, with rifing
fides, to proteft the nerves that pafs in the hollow ;
and at laft each fide terminates in an obtufe point,
for the infertion of mufcles.

The fpinal procefles of thefe cervical bones ftand
neaily ftraight backwards, are fliorter than thofe of
any other vertebra , and are forked or double at their
ends ; and hence allow a more convenient infertion
to mufcles.

The thick cartilages between the bodies of thefe
cervical vertebra , the obliquity of their oblique procef-
fes, and the fhortnefs and horizontal fituation of theic
fpinal procefles, all confpire to allow them large mo-
tion.

The holes between the bony crofs bridges, for the
paflage of the nerves from the fpinal marrow , have
their largeft fhare formed in the lowefl: of the two
vertebra, to which they are common.

So far moll of the cervical vertebra agree ; but
they have fome particular differences, which oblige
us to confider them feparately.

The

Of the SKELETON.

*3J

The firft, from its ufe of fupporting the head, has
the name of atlas (a) ; and is alio called epiftrophea ,
from the motion it performs on the fecond.

The alias, contrary to all the other vertebra: of the
fpine, has no body ; but, iullead of it, there is a bo-
ny arch. — In the convex fore-part of which, a fmall
rifing appears, where the mufculi longi colli are infert-
ed ; and, on each fide of this protuberance, a fmall
cavity may be obferved, where the recli interne mino-
res take their rife. — The upper and lower parts of the
arch are rough and unequal, where the ligaments that
connect this vertebra to the os occipitis, and to the fe-
cond vertebra , are fixed. — The back-part of the arch
is concave, fmooth, and covered with a cartilage, in a
recent fubjed!, to receive' the tooth-like procefs of
the fecond vertebra. — In a firft vertebra , from which
the fecond has been feparated, this hollow makes the
paffage for the fpinal marrow to feem much larger
than it really is: On each fide of it a fmall rough fi-
nuoGty may be remarked, where the ligaments going
to the fides of the tooth-like procefs of the following
vertebra are fattened ; and on each fide, a fmall rough
protuberance and depreflion is obfervablc, where the
tranfverfc ligament, which fecures the tooth-like pro-
cefs in the finuofity, is fixed, and hinders that pro-
cefs from injuring the medulla fpinalis in the flections
of the head.

The atlas has as little fpinal procefs as body ; but,
in Head thereof, there is a large bony arch, that the
mufcles which pafs over this vertebra at that place
might not be hurt in extending the head. On the
back and upper part of this arch there are two de-
preifions where the recli p9/lici minores take their rife';
and at the lower part are two other finuofities, into
which the ligaments which conned! this bone to the
following one are fixed.

The fuperior oblique procefies of this atlas are large,
oblong, hollow’, and more horizontal than in any other
vertebra — They rife more in their external thaninter-

M nal

ArfeiyaKof.

*34

Of the SKELETON.

rial brim ; by which their articulations with the condyloid
procefl'es of the os occipitis are firmer. — Lender the ex-
ternal edge of each of thefe oblique procefl'es, is the
foffa or deep open channel, in which 4)e vertebral ar-
teries make the circular turn, as they are about to
enter the great foramen of the occipital bone, and
where the tenth pair of nerves goes out. — In feveral
bodies, I have feen this foffa covered with bone.—
The inferior oblique procefl’es extending from within
outwards and downwards, are large, concave, and
circular. So that this vertebra , contrary to the other
fix, receives the bones with which it is articulated
both above and below.

The tranfverfe procefl'es here are not much hollowed
or forked, but are longer and larger than thofe of any
other vertebra of the neck, for the origin and infertion
of feveral mufcles; of which thofe that ferve to
move this vertebra on the fecond, have a confiderable
lever to a£i with, becaufe of the diftance of their in-
fertion from the axis of 'revolution.

The hole for the fpinal marrow is larger in this
than in any other vertebra , not only on account of
the marrow being largeft here, but alfo to prevent its
being hurt by the motions of this vertebra on the fe-
cond one. — This large hole, and the long tranfverfe
procefl'es, make this the broadefl vertebra of the neck.

The condyles of the os occipitis move forwards and
backwards in the fuperior oblique procefl'es of this
vertebra; but from the figure of the bones forming
thefe joints, it appears, that very little motion can
here be allowed to either fide; and there mufl be
ftill lefs circular motion.

In new-born children, this vei-tebra has only the
two lateral pieces offified ; the arch, which it has at
its fore-part inftead of a body, being cartilaginous.

The fecond vertebra colli is called dentata , from the
tooth-like procefs on the upper part of its body.
Some authors call it epiJ1ropheay but improperly, fince
this defignation is only applicable to the flrft, which
moves on this as on an axis.

The

Of the SKELETON.

*35

The body of this vertebra is fomewhat of a pyra-
midal figure, being large, and produced downwards,
efpecially at its fore-fide, to enter into a hollow of
the vertebra below ; while the upper part has a fquare
procefs with a fmall point Handing out from it. This
it is that is imagined to refemble a tooth {a}r and
has given name to the vertebra. — The fide of this
procefs, on which the hollow of the anterior arch of
the firft vertebra plays, is convex, ‘fmooth, and cover-
ed with a cartilage ; and it is of the fame form be-
hind, for the ligament, which is extended tranfverfe -
]y from one rough protuberance of the firft vertebra
to the other, and is cartilaginous in the middle, to
move on it. — A ligament likewife goes out in an ob-
lique tranfverfe direction, from each fide of the/ro-
cejjus dentatus , to be fixed at its other end to the firit
vertebra , and to the occipital bone: And another li-
gament rifes up from near the point of the procefs to
the os occipitis.

The luperior oblique procefi'es of this vertebra den -
tata are large, circular, very nearly in an horizontal
pofition, and flightly convex, to be adapted to the
inferior oblique procefTes of the firft vertebra. — A
moveable cartilage is faid by fome authors to be in-
terpofed between thefe oblique procefles of the firft
and fecond vertebra ; but I could never find it. —
The inferior oblique procefles of this vertebra dentata
anfwer exactly to the defeription given of thole com-
mon to all the cervical vertebra.

The tranfverfe procefles of the vertebra dentata are
fliort, very little hollowed at their upper part, and
not forked at their ends ; and the canals through
which the cervical arteries pais, are reflected out-
wards about the middle fubftance of each procefs ;
fo that the courfe of thefe veflels may be directed to-
wards the tranfverfe procefles of the firft vertebra.

Had this curvature of the arteries been made in a
part fo moveable as the neck is, while they were not
defended by a bone, and fixed to that bone, fcarce a

2 motion

(a) Conoidcs, pyrenoidcs, odwitoides.

136 Of the SKELETON.

motion could have been performed without the ut-
moft hazard of compreffion, and a Hop put to the
courfe of the liquids, with all its train of bad confe-
quences. Hence we obferve this fame mechanifm
feveral times made ufe of, when there is any occa-
1'ion for a fudden curvature of a large artery. This
is the third remarkable inftance of it we have feen.
The firft was the pafiage of the carotids through the
temporal bones ; and the fecond was that lately de-
fcribed in the vertebral arteries, turning round the
oblique proceftes of the firft vertebra, to come at the
great hole of the occipital bone.

The fpinal procefs of this vertebra de/itata is thick,
ffrong, and fihort, to give fufficient origin to the
mufeuli recti majores, and obliqui itiferiores , and to pre-
vent the contuiion of thefe and other mufcles in pull-
ing the head back.

This fecond vertebra confifls, at the birth, of four
benv pieces : For, befidcs the three which I already
mentioned as common to all the vertebra: , the tooth-
like procefs of this bone is begun at this time to be
ofTifted in its middle, and is joined as an appendix to
the body of the bone. — Left this appendix be bend-
ed or difplaced, nurfes ought to keep the heads of
new-born children from falling too far backwards by
/lay-bands, or fome fuch means, till the mufcles at-
tain ftrength fufficient to prevent that dangerous mo-
tion.

When we are acquainted with the ftru£ture and
articulations of the firft and fecond vertebra , and
know exactly the ftrength and connection of their
ligaments, there is no difficulty in underftanding the
motions that are performed upon or by the firft \
though this fubjeCt was formerly matter of hot dis-
pute among fome of the greateft anatomifts {b). It
is none of my purpofe at prefent to enter into a de-
tail of the rcafons advanced by either party ; but to
explain the fact, as any one may fee it, who will re-
move the mufcles, which, in a recent fubjedt, hinder

( b ) See E attach, de motu capitis,

137

Of the SKELETON.

the view of thefe two joints, and then will turn the
head into all the different pofitions it is capable oi.
The head may then be feen to move forwards and
backwards on the firft vertebra, as was already fain,
while the atlas performs the circumgyratio upon the -
fecond vertebra ; the inferior oblique procefies of the
firft vertebra fhufHing eafily in a circular way on the
fuperior oblique procefies of the fecond, and its bo-
dy or anterior arch having a rotation on the tooth-
like procefs, by which the perpendicular ligament
that is fent from the point of the tooth-like procefs
to the occipital bone is twilled, while the lateral li-
gaments, that fix th t procejfus dentatus to the Tides of
the firft vertebra, and to the os oceipitis, are very dif-
ferently affected ; for the one upon the fide towards
which the face is turned by the circumgyratio , is
much fhortened and lax, while the oppofite one is
ftretched and made tenfe, and, yielding at laft no
more, prevents the head from turning any farther
round on this axis. So that thefe lateral ligaments
are the proper moderators of the circumgyratio of the
head here, which mull be larger or ImaJler, as thefe
ligaments are weaker or ftronger, longer or fhorter,
and more or lefs capable of being ftretched. — Befides
the revolution on this axis, the firft vertebra can
move a fmall way to either fide -y but is prevented
from moving backwards and foi wards, by its ante-
rior arch, and by the crofs ligament, which are both
clofely applied to the tooth-like procefs. Motion for-
wards here, would have been of very bad eonfe-
quence, as it would have brought the beginning of
the fpinal marrow upon the point of the tooth-like
procefs.

The rotatory motion of the head is of great ufe to
us on many accounts, by allowing us to apply quick-
ly our organs of the fenfes to objeifts : And the axis
of rotation was altogether proper to be at this place \
for, if it had been at a greater diftance from the
head, the weight of the head, if it had at any time
been removed from a perpendicular bearing to the

M 3 fmall

138 Of the SKELETON.

fmall very moveable joint, and thereby had acquired
a long lever, would have broke the ligaments at every
turn irrconfiderately performed ; or thefe ligaments
mull have been formed much flronger than could
have been connedled to fuch fmall bones. Neither
could this circular motion be performed on the firll
•uertebra without danger, becaufe the immoveable
part of the medulla oblongata is fo near, as at each
large turn, the beginning of the fpinal marrow would
have been in danger of being twilled, and of fuffer-
rng by the compreflion this would have made on its
tender fibrils.

It is neccfiary to obferve, that the lateral or mode-
rator ligaments confine fo much the motion of the
firll vertebra upon the fecond, that, though this joint
may ferve us on feveral occafions, yet we are often
obliged to turn our faces farther round, than could
he done by this joint alone, without the greateft
danger of twilling the fpinal marrow too much, and
alio of luxating the oblique procefles ; therefore, in
large turns of this kind, the rotation is affilled by all
the vertebra of the neck and loins ; and if this is not
fufiicient, we employ moll of the joints of the lower
extremities. — -This combination of a great many
joints towards the performance of one motion, is al-
io to be obferved in feveral other parts of the body;
notwithflanding fuch motions being generally faid to
be performed by fome fingle joint only.

The third vertebra of the neck is by fome called
axis ; but this name is applied to it with much lefs
reafon than to the fecond — This third, and the three
below', have nothing particular in their ftrudlure ;
but all their parts come under the general defeription
formerly given, each of them being larger as they
defeend.

The feventh ( c ) vertebra of the neck is near to the
form of thofe of the back, having the upper and
lower furfaces of its body lefe hollow than the 0-
thers ; — The oblique procefles are more perpendicu-
lar j,

(r) Atlas quibufdam, maxima, magaa vertebra, promiaens.

Of the SKELETON. 139

hr ; — neither fpinal nor tranfverfe procefles are fork-
ed.— This feventh and the fixth vertebra of the neck
have the hole in each of their tranfverfe procefles
more frequently divided by a fmall crofs bridge, that
goes between the cervical vein and artery, than any
of the other vertebra.

The twelve clorfal ( d ) may be diftinguifhed from
the other vertebra of the fpine by the following
marks.

Their bodies are of a middle fize, betwixt thofe of
the neck and loins ; — they are more convex before
than either of the other two forts •, and are flatted
laterally by the prefiure of the ribs, which are infert-
ed into fmall cavities formed in their Tides. This
flatting on their fides, which makes the figure of
thefe vertebra almoft an half oval, is of good ufe ; as
it affords a firm articulation to the ribs, allows the
trachea arteria to divide at a fmall angle, and the o-
ther large vefl'els to run fecure from the aCtion of the
vital organs. — Thefe bodies are more concave behind
than any of the other two clafles. — Their upper and
lower furfaces are horizontal.

'the cartilages interpofed between the bodies of
thefe vertebra are thinner than in any other of the
true vertebrae ; and contribute to the concavity of
the fpine in the thorax, by being thinned at their
fore-part.

The oblique procefles are placed almoft perpendicu-
lar -, the upper ones flaming but a little forwards,
and the lower ones flaming as much backwards. —
They have not as much convexity or concavity as is
worth remarking. — Between the oblique procefles of
oppofite fides, feveral fharp procefles ftand out from
the upper and lower parts of the plates which join to
form the fpinal procefs ; into thefe fharp procefles
ftrong ligaments are fixed, for connecting the ver-
tebra.

0 The

(*0 QufdMf , vutv, vs’oroa antifterni, pettoris,

tergi.

140 Of the SKELETON.

The tranfverfe procefles of the dorfal vertebrae are
long, thicker at their ends than in the middle, and
turned obliquely backwards ; which may be owing
to the preffure of the ribs, the tubercles of which are
inferted into a deprefiion near the end of thcfe pro-
cefles.

The fpinal procefles are long, fmall-pointed, and
floping downwards and backwards ; from their up-
per and back-part a ridge rifes, which is received by
a fmall channel in the fore-part of the fpinal pro-
cefs immediately above, which is here conneXed to it
by a ligament.

The conduit of the fpinal marrow is here more cir-
cular, but, correfponding to the fize of that cord, is
fmaller than in any of the other vertebrae , and a larger
fhare of the holes in the bony bridges, for the tranf-
miflion of the nerves, is formed in the vertebra above,
than in the one below.

The connection of the dorfal vertebrae to the ribs,
the thinnefs of their cartilages, the ereX fituation of
the oblique procefles, the length, floping, and con-
nexion of the fpinal procefles, all contribute to re-
ftrain thefe vertebrae from much motion, which
might difturb the aXions of the heart and lungs ;
and, in confequence of the little motion allowed
here, the intervertebral cartilages fooner fluivel, by
becoming more folid : And therefore, the firft re-
markable curvature of the fpine obferved, as people
advance to old age, is in the leaft-ftretched vertebrae
of the back \ or old people firft become round-
fhouldered.

The bodies of the four uppermoft dorfal vertebra
deviate from the rule of the vertebra becoming larger
as they defcend ; for the firft of the four is the lar-
geft, and the other three below gradually become
fmaller, to allow the trachea and large veflels to. di-
vide at fmaller angles.

The two uppermoft vertebra of the back, inftead
of being very prominent forwards, are flatted by the
aXion of the mufculi longi colli and recti majores.

Th&

Of the SKELETON. 141

The proportional fize of the two little depreflions
in the body of each vertebra , for receiving the heads
of the ribs, feems to vary in the following manner;
the deprellion on the upper edge of each vertebra de-
creafes as far down as the fourth, and after that in-
creafes.

The tranfverfe procelTes are longer in each lower
vertebra to the feventh or eighth, with their fmooth
furfaces, for the tubercles of the ribs, facing gradu-
ally more downwards ; but afterwards as they defcend
they become fhorter, and the fmooth furfaces are di-
rected more upwards.

The fpinous procefles of the vertebra of the back
become gradually longer and more flanting from the
firft, as far down as the eighth or ninth vertebra ;
from which they manifeftly turn Ihorter and more
ere£t.

The firft (f) vertebra , befides an oblong hollow in
its lower edge, that aflifts in forming the cavity
wherein the fecond rib is received, has the whole ca-
vity for the head of the firft rib formed in it.

The fecond has the name of axillary (g), without
any thing particular in its ftru£ture.

The eleventh ( h ) often has the whole cavity for the
eleventh rib in its body, and wants the fmooth fur-
face on each tranfverfe procefs.

The twelfth (/) always receives the whole head of
the laft rib, and has no fmooth furface on its tranf-
verfe procefles, which are very fhort. The fmooth

furfaces of its inferior oblique procefles face outwards
as the lumbar do. — And we may fay, in general, that
the upper vertebra of the back lole gradually their
refemblance to thofe of the neck, and the lower ones
come nearer to the figure of the lumbar.

'I he articulation of the vertebra of the back with
the ribs, fhall be more particularly confidered, after
the ribs are defcribed. Only it may be proper now

to

(f) Korpia, guttural is.

(£) Mao'^'KX.ic’rc^.

( b ) A/>prx>,<, in neutrain partem inclinans.

CO Aia<rcoj-r«j>, praecingcns.

Of the SKELETON.

14*

to remark, that the ligaments which ferve that arti-
culation aflift in connecting the vertebra.

The loweft order of the true vertebra is the lum-
bar (ir), which are five bones, that may be diftinguifh-
ed from any others by thefe marks: i. Their bodies,
though of a circular form at their fore-part, are
fomewhat oblong from one fide to the other ; which,
may be occafioned by the prefiure of the large vefl'els,
the aorta and cava , and of the vifccra. The epiphyfes
on their edges are larger, and therefore the upper
and lower furfaces of their bodies are more concave
than in the vertebra of the back. 2. The cartilages
between thefe vertebra are much the thickeft of any,
and render the fpine convex within the abdomen, by
their greateft thicknefs being at their fore-part. 3. The
oblique procefles are ftrong and deep; thofe in oppo-
site Sides being almoft placed in parallel planes ; the
Superior, which are concave, facing inwards, and
the convex inferior ones facing outwards: and there-
fore each of thefe vertebra receives the one above it,
and is received by the one below ; which is not fo e-
vident in the other two dalles already deferibed.
4. Their tranfverfe procefles are Small, long, and al-
moft ered, for allowing large motion to each bone,
and Sufficient infertion to mufcles, and for Supporting
and defending the internal parts. 5. Betwixt the
roots of the Superior oblique and tr anfverfe procefles,
a Small protuberance may be obferved, where fomc
of the mufcles that raife the trunk of the body are
inferted. 6. Their fpinal procefles are ftrong, ftraight,
and horizontal, with broad flat Gdes, and a narrow
edge above and below; this laft being deprefled on
each fide by mufcles. And at the root of thefe
edges, we fee rough furfaces for fixing the ligaments.
7. The canal for the numerous cords, called cauda
equina, into which the fpinal marrow divides, is ra-
ther larger in thefe bones than what contains that
marrow in the vertebra of the back. 8. The holes
for the pafl'uge of the nerves are more equally form-
ed

(i) o<rfi>5f i^vec, 4-iiuf) renum, lumbonim.

Of the SKELETON.

*43

ed out of both the contiguous vertebra than in the
other clafies ; the upper one furnifhes however the
larger fhare of each hole.

The thick cartilages between thefe lumbar vertebra ,
their deep oblique procefies, and their erect fpinal
procefies, are all fit for allowing large motion ; though
it is not fo great as what is performed in the neck ;
which appears from comparing the arches which the
head defcribes when moving on the neck, or the loins
only.

The lumbar vertebra as they defcend, have their
oblique procefies at a greater diftance from each o-
ther, and facing more backwards and forwards.

Both tranfverfe and fpinal procefies of the middle-
moft vertebra of the loins are longell: and thickeft;
in the vertebra above and below they are lefs : So
that thefe procefies of the firft (/) and fifth (m) are
the lead, to prevent their flriking on the ribs or ojfa
rlii/m, or their biuifing the mufcles in the motions of
the fpine.

'1 he epiphyfes round the edges of the bodies of the
lumbar vertebra are moft raifed in the two lowed,
which confequently make them appear hollower in
the middle than the others are.

The body of the fifth vertebra is rather thinner
than that of the fourth. — The fpinal procefs of this
fifth is fmaller, and the oblique procefies face more
backwards and forwards than in any other lumbar
vertebra.

After confidering the flructure of the particular
vertebra , and their mutual connection, we may ob-
ferve a folicitous care taken that they {hall not be
disjoined, but with great difficulty; for befides being
connected by ftrong ligaments proportioned to the
forces which are to be refilled, their bodies either en-
ter fo into each other, as to prevent their being dis-
placed any way, as in the vertebrae of the neck ; or
they are propped on all Tides, as thefe of the back are

by

(/) Njtyurwf, rcnalis.

(m) Atr^ecKirtif, fukiens.

*44

Of the skeleton.

by the ribs ; or their furfaces of contaft are fo broad,
as to render the reparation almoft impratticable, as
in the loins ; while the depth and articulation of the
oblique procefles are exactly proportioned to the
quantity of motion which the other parts of the
bones allow, or the mul'cles can perform: Yet, as
thefe oblique procefles are fmall, and therefore not
capable of fo fecure a conjun&ion, as the larger bo-
dies, they mayfooner yield to a disjoining force-, but
then their diflocation is not of near fo bad confe-
quence as the reparation of the bodies would be.
For, by the oblique procefles being diflocated, the
mufcles, ligaments, and fpinal marrow, are indeed
ftretched ; but this marrow mud be comprefled, or
entirely deftroyed, when the body of the vertebra is
removed out of its place.

The FALSE VERTEBRAE compofe the under
pyramid of the fpine. They are diftinguifhed from
the bones already defcribed juftly enough by this epi-
thet of falfe ; becaufe though each bone into which
they can be divided in young people, refembles the
true vertebrae in figure, yet none of them contribute
to the motion of the trunk of the body; they being
intimately united to each other in adults, except at
the lower part, where they are moveable ; whence
they are commonly divided into two bones, os facrum
and coccygis.

OS SACRUM («), is fo called, from being offered
in facrifice by the ancients, or rather becaufe of its

largenefs in refpe£t of the other vertebrae. This

bone is of an irregular triangular fhape, broad above,
narrow below, convex behind, for the advantageous
origin of the mufcles that move the fpine and thigh
backwards; and concave behind, for enlarging the
cavity of the pelvis. — Four tranfverfe lines, of a co-
lour different from the reft of the bone which are
feen on its fore-part, are ^ie marks of divifion of the

five

{») ltpiv, rrorS'vx.t ( fityae Hippocrat. vnoeifnS oribas.
n*«rv, latum, os dunium, davium,

Of the ’SKELETON. 145

five different bones of which it confifls in young per-

fons. r

The fore-part of the os facrum , analogous to the
bodies of the true vertebrae , is fmooth and fl2t, to al-
low a larger fpace for the contained bowels, without
any danger of hurting them ; or this flat figure may
be owing to the equal preflure of thefe bowels, par-
ticularly of the laft gut. — The back-part of it is al-
mofl ftraight, without fo large a cavity as the verte-
brae have ; becaufe the fpinal marrow, now feparated
into the catida equina , isfmall. — 1 he bridges between
the bodies and procefles of this bone, are much
thicker, and in proportion fhorter, than in the former
clafs of bones. — The ftrength of thefe crofs bridges
is very remarkable in the three upper bones, and is
well proportioned to the incumbent weight of the
trunk of the body, which thefe bridges fuftain in a
tranfverfe, confequently an unfavourable fituation,
when the body is eredt.

There are only two oblique procefles of the os fi-
c'rum\ one (landing out on each Title from the upper

part of the firft bone. Their plain ere£l furfaces

face backwards, and are articulated with the inferior
oblique procefles of the laft vertebra of the loins, to
which each of thefe procefles is connected by a ftrong
ligament, which rifes from a fcabrous cavity round
their roots, where mucilaginous glands are alfo lodg-
ed.— Inftead of the other oblique procefles of this
bone, four rough tubercles are to be feen on each
fide of its furface behind, from which the mufculus
facer has its origin.

The tranfverfe procefles here are all grown toge-
ther into one large ftrong oblong procefs on each
fide, which, fo far as it anfwers to the fiift three
bones, is very .thick, and divided into two irregular
cavities, by a long perpendicular ridge. — The fore-
moft of the two cavities has commonly a thin carti-
laginous Ikin covering it in the recent fubje£l, and is
adapted to the unequal protuberance of the os ilium ;
and a ftrong ligament conne&s the circumference of
!• . 1 . N thefe

t<\6 Of the SKELETON.

thefe furfaces of the two bones. — The cavity behind
is divided by a tranfverfe ridge into two, where ftrong
ligamentous firings that go from this bone to the os
ilium, with a cellular fubftance containing mucus, are
lodged.

The tranfverfe procefles of the two lad bones of
the os facrum are much fmaller than the former. — At
their back-part, near their edge, a knob and oblong
flat fui face give rife to two ftrong ligaments which
are extended to the os ifibiutn ; and are therefore call-
ed facro-fciatic .

The fpinal procefles of the three uppernioft bones
of the os facrum appear fhort, (harp, and almoft erc£f,
while the two lower ones are open behind ; and fome-
times a little knob is to be feen on the fourth, though
generally it is bifurcated, without the two legs meet-
ing into a fpine ; in which condition alfo the fiift is
often to be feen ; and fometimes none of them meet,
but leave a t Jinus, or rather fojfa, in (lead of a canal {o'). —
The mufculus latiffmus and longtfjimus dorft, facro-lum-
halts and glutacus maximus , have part of their origins
from thefe fpinal procefles.

The canal between the bodies and procefles of this
bone, for the cauda equina, is triangular j and be-
comes fmaller as it defeends, as th e cauda alfo does. —
Below the third bone, this paflage is no more a com-
pletejxmy canal, but is open behind ; and is only there
defended by a ftrong ligamentous membrane ftrercbed
over it, which, with the mufcles that cover it, and
are very prominent on each fide, is a fuflicient de-
fence for the bundle of nerves within.

At the root of each oblique procefs of this bone,
the notch is confpicuous, by which, and fuch another
in the laft vertebra of the loins, a paflage is left for
the twenty-fourth fpinal nerve ; and, in viewing the
os facrum, either before or behind, four large hole6
appear in each fide, in much the fame height, as
where the marks of the union of its feveral bones re-:
main. Some of the largeft nerves of the body pafe

through

(*) Vcrheyen Anat. traft. J. cap. 9.— Sue Trad, d’ofteol. p. 127.

Of the SKELETON. 147

through the anterior holes; and fuperfici&I grooves run-
ning outwards from them in different directions, fhew

the courfe of thefe nerves. From the intervals of

thefe grooves, the pyriformis mufcle chiefly rifes.
The holes in the back-part of the bone are covered
by membrane's which allow fmall nerves to pals
through them. — The two upperrnoft of thefe holes,
efpecially on the fore-fide, are the largelt ; and as the
bone defcends, the holes turn fmaller. Sometimes a
notch is only formed at the lower part in each fide of
this bone; and in other fubjeCts there is a hole com-
mon to it and the os coccygis , through which the
twenty-ninth pair of fpinal nerves paffies ; and fre-
quently a bony bridge is formed on the back-part of
each fide by a prooefs fent up from the back-part of
the os coccygis , and joined to the little knobs which
the laft bone of the os facrum has inftead of a fpinal
procefs. Under this bridge or jugum , the twenty-
ninth pair of fpinal nerves runs tn its courfe to the
common holes juft now defcribed.

The upper part of the body of the firft bone re-
fembles the vertebrae of the loins; but the fmall fifth
bone is oblong tranfverfely, and hollow in the middle
of its lower lurface.

The fubftance of the os facrum is very fpongy,
without any confiderable folid external plates, and is
lighter proportionally to its bulk than any other bone
in the body ; but is fee u red from injuries by the thick
mufcles that cover it behind, and by the flrong liga-
mentous membranes that clofelv adhere to it. — As
this is one of the moft remarkable inftances of this
fort of defence afforded a foft weak bone, we may-
make the general obfervation, That, vvhere-ever we
meet with fuch a bone, one or other, or both thefe
defences are made ufe of, the firft to ward off in-
juries, and the fecond to keep the fubftance of the
bone from yielding too eafily.

This bone is articulated above to the laft verti bra
of the loins, in the manner that the lumbar vertebrae
are joined ; and therefore the fame motions mav be ver-

N 2 fcrrrsd

*48 . Of the SKELETON.

formed here. — The articulation of the lower part of
the osfacrum to the os coccygis, feems well enough ad-
apted for allowing confiderable motion to this laft
bone, was it not much confined by ligaments. La-
terally, the os Jacrum is joined to the ojja ilium by an
immoveable Jynchondrofts , or what almoft deferves the
name of a future ; for the cartilaginous cruft on the
furface of the bones is very thin, and both their fur-
faccs are fo fcabrous and unequal, as to be indented
into each other : which makes fuch a ftrong connec-
tion, that great force is required to feparate them,
after all the mufcles and ligaments are cut. — Fre-
quently the two bones grow together in old fubje&s.

The ufes of the os Jacrum are, to ferve as the com-
mon bafe and fupport of the trunk of the body, to
guard the nerves proceeding from the end of the fpi-
nal marrow, to defend the back-part of the pelvis ,
and to afford fufficient origin to the mufcles which
move the trunk and thigh.

The bones that compofe the os Jacrum of infants,
have their bodies feparated from each other by a thick
cartilage; and, in the fame manner as the true ver-
tebraey each of them confifts of a body and two la-
teral plates, connefted together by cartilages ; the
ends of the plates feldom being contiguous behind.

OS COCCY'GIS (a), or rump-bone , is that trian-
gular chain of bones depending from the os Jacrum ;
each bone becoming fmaller as they defeend, till the
lall ends almoft in a point. The os coccygis is convex
behind, and concave before; from which crooked
pyramidal figure, which was thought to refemble a
cuckoo’s beak, it has got its name.

This bone confifts ol four pieces in people of mid-
dle age : — In children, very near the whole of it is car-
tilage : In old fubje&s, all the bones are united, and
become frequently one continued bone with the os
Jacrum.

The higheft of the four bones is the largeft, with
•fhoulders extended farther to each fide than the end

of

(a) Ofperuym ippo;, caudae oSj-ipoadylium, os cuenii.

l49

Of the SKELETON".

of the o» facrttm ; which enlargement fhould, in my
opinion, ferve as a diftinguifhing mark to fix the
limits of either bone; and therefore fhould takeaway
all difpute about reckoning the number of bones,
of which one or other of thefe two parts of the falfe
i vertebrae , is compofed ; which difpute mud ftill be
kept up, fo Jong as the numbering five or fix bones
in the os facrum depends upon the uncertain accident
of this broad-fhouldered little bone being united to
or feparated from it. — The upper furface of this bone
is a little hollow. — From the back of that bulbous
part called its fhoulders , a procefs often rifes up on
each fide, to join with the bifurcated fpine of the
fourth and fifth bones of the os facrum , to form the
bony bridge mentioned in the defcription of the os
facrum. — Sometimes thefe fhoulders are joined to the
fides of the fifth bone of the os facrum , to form the
hole in each fide common to thefe two bones, for the
pafl'age of the twenty ninth pair of fpinal nerves. —
Immediately below the fhoulders ot the os coccygis , a
notch may be remarked in each fide, where the thir-
tieth pair of the fpinal nerves pafTes. — The lower end
of this bone is formed into a fmali head, which very
often is hollow in the middle.

The three lower bones gradually become fmaller,
»nd are fpongy ; but are ftrengthened by a ftrong liga-
ment which covers and conne&s them. — Their ends,
by which they are articulated, are formed in the fame
manner as thofie of the firft bone are.

Between each of thefe four bones of young fub-
je£ts, a cartilage is interpofed ; therefore their articul-
ation is analogous to that of the bodies of the ver-
tebrae of the neck : For, as has been above remark-
ed, the lower end of the os facrum , and of each of
the three fuperior bones of the os coccygis , has a fmali
depreffion in the middle ; and the upper part of all
the bones of the os coccygis is a little concave, and
confequently the interpofed cartilages are tbickefl in
the middle, to fill up both cavities; by which they
connect the bones more firmly — When the cartilages

N 3 oflify.

15a Of the SKELETON.

oflify, the upper end of each bone is formed into a
cavity, exa-Tly adapted to the protuberant lower end
of the bone immediately above. — From this fort of
articulation, it is evident, that, unlels when thefe
bones grow together, all of them are capable of mo-
tion •, of which, the firft and fecond, especially this
laft, enjoys the largefl (hare.

The lower end of the fourth bone terminates in a
rough point, to which a cartilage is appended.

To the fules of thefe bones of the os coccygis , the
coccygaei mufcles (b), and part of the Ievatores anit
and of the glutaei maximi , are fixed.

The fubllance of thefe bones is very fpongy, and
in children cartilaginous ; there being only a part of
the firft bone offified in a new-born infant. — Since
therefore the intejlinum rectum of children is not fo
firmly fupported as it is in adults, this may be one
reafon why they are more fubje£t to a procidentia ani
than old people (c).

From the defer iption of this bone, we fee how lit-
tle it refembles the vertebrae ; fince it feldom has
procefles, never has any cavity for the fpinal marrow,
nor holes for the paflage of nerves. — Its connection
hinders it to be moved to either fide; and its motion
backwards and forwards is much confined: Yet as
its ligaments can be ltretched by a confiderable force,
it is a great advantage in the excretion of the foeces
alvinae, and much more in child-bearing, that this
bone fiiould remain moveable : and the right manage-
ment of it, in delivering women, may be of great
benefit to them ( d ). — Ihe mobility of the os coccygis
diminifiiing as people advance in age, efpecially when
its ligaments and cartilages have not been kept flex-
ible by being Ilretched, is probably one reafon why
the women, who are old maids before they marry,
have generally hard labour in child-bed.

The

(i) Douglas, Myograph, chap. 40.— Euftach. tab. 36. No. 45. 20.

(c) Spipcl. dc humani corp. fabric, lib. 2. jeap. 22. — Paaw, dc
•flib. par. 2. cap. 3

(d) Paaw, ibid.— Deventer, Operat. chirurg. cap. 27.

Of the SKELETON. 151

The os coccygis ferves to fudain the inteJUnum rec-
tum ; and, in order to perform this office more effec-
tually, it is made to turn with a curve forwards; by
which alfo the bone itfelf, as well as the muffles and
teguments, is preferved from any injury, when we
fit with our body reclined back.

The fecond part of the trunk of the Ikeleton, the
PELVIS , is the cylindrical cavity at the lower part
of the abdomen , formed by the os facrum, os coccygis ,
and ojfa innominata ; which lad therefore fall now in
courle to be examined.

Though the name of OSSA INNOMINATA (e)
contributes nothing to the knowledge of their fitu-
ation, ftru&ure or office; yet they have been fo long
and univerfally known by it, that there is no occafion
for changing it. — They are two large broad bones,
w’hich form the fore-part and fides of the pelvis , and
the lower part of the (ides of the abdomen. — In child-
ren each of tbefe bones is evidently divided into three ;
which are afterwards fo intimately united, that fcarce
the lead mark of their former Separation remains:
This notwithdanding, they are described as confid-
ing each of three bones, to wit, the os ilium, ifchium ,
and pubis ; which I ffiall fird defcribe Separately, and
then ffiall confider what is common to any two of
them, or to all the three.

OS ILIUM (f), or haunch-bone , is Gtuated higheft
of the three, and reaches as far down as one third
of the great cavity into which the head of the thigh-
bone is received.

The external fide of this bone is unequally convex,
and is called its dorfum ; — the internal concave fur-
face is by fome (but improperly) named its cojla. — The
femicircular edge at the highed part of this bone,
which is tipped with a cartilage in the recent fubjett,
is named the J pine , into which the external or descen-
ding oblique mufcle of the abdomen is inferted ; and
from it the internal afcending oblique and the tranf-
m., * *r*ri ' “ verfe

(e) Xxcxtov, XfotQvo-t if, facro eonjunfta.

(/) A<t/oy«vj fcaphium, lumbarc, clunium, eluvium, anchas.

*5*

Or THE SKELETON.

verfe mufcles of the belly, with the gluteus maximum , ‘
qnadratus lumborum, and latiffimus dorfi , have their o-
rigin. Some ( a ) are of opinion, that it is only the
tendinous cruft of all thefe mufcles, and not a carti-
lage, as commonly alledged, that covers this bony
edge — The ends of the fpine are more prominent
than the furface of the bone below them ; therefore
are reckoned procefles. — From the anterior fpinal pro-
cefs, the fartorius and fa/d alts mufcles have their rife,
and the outer end of the doubled tendon of the ex-
ternal oblique mufcle of the abdomen , commonly call-
ed Fallopius's or Poupart' s ligament, is fixed to it. —
The infide of the pofterior fpinal procefs, and of part
of the fpine forward from that, is made flat and
rough where the facro-lumbalis and longiffimus dorfi
rife; and to its outfide ligaments, extended to the os
Jacrum and tranfverfe procefles of the fifth and fourth
vertebrae of the loins, ate fixed ( b ). — Below the an-
terior fpinal procefs another protuberance ftands out,
which, by its fituation, may be diftinguifhed from
the former, by adding the epithet of inferior., where
the mufculus reSus tibiae has its origin (c). — Betwixt
thefe two anterior procefles the bone is hollowed
where the beginning of the fartorius mufcle is lodg-
ed.— Below the pofterior fpinal procefs, a fecond
protuberance of the edge of this bone is in like man-
ner obfervable, which is clofely applied to the os fa -
erum. — Under this laft procefs a confiderable large
niche is obfervable in the os ilium ; between the
fides of which and the ftrong ligament that is ftretched
over from the os facrum to the (harp-pointed procefs of
the os ifehium of the recent fubjeft, a large hole is
formed, through which the mufculus pyrfortnis, the
great fciatic nerve, and the pofterior crural veflels
pafs, and are prote£led from comprefTion.

The external broad fide or dorfum of the os ilium is

a little

(a) Window, Expofition anatomique du corps humain, traitc dcs
os frals, § 96.

(b) Weitbrecht, Syndcfmolog. feft. 4. § 39. 40. 46. 47.

(rj Baker, Curf. efteoleg. demouftx. 3.

Of the S K E L E T O N.

*53

a little hollow towards the fore-part ; farther back it
is as much raifed ; then is confiderably concave ; and,
laftly, it is convex. Thefe inequalities are occafion-
ed by the actions of the mufcles that are fituated on
this furface. — From behind the uppermoft of the two
anterior fpinal procefl'es, in fuch bones as are ftrong-
ly marked by the mufcles, a femicircular ridge is ex-
tended to the hollow pafl'age of the fciatic nerve.
Between the fpine and this ridge, the glutaeus medius
takes its rife. Immediately from above the lowed of
the anterior fpinal procefl'es, a fecond ridge is ftretch-
ed to the niche. Between this and the former ridge,
the glutaeus minimus has its origin. — On the outfide
of the poderior fpinal procefl'es, the dorfum of the os
ilium is flat and rough, where part of the mufculus
glutaeus maxim us and pyriformis rifes. — The lowed
part of this bone is the thicked, and is formed into a
large cavity with high brims, to aflid in compofing
the great acetabulum ; which fhall be conCdered, after
all the three bones that conditute the os innominatum%
are deferibed.

The internal furface of the os ilium is concave in
its broaded fore-part, where the internal iliac mufcle
has its origin, and fome fhare of the inttjlinum ilium
and colon is lodged. — From this large hollow, a fmall
finuofity is continued obliquely forwards, at the in-
fide of the anterior inferior fpinal procefs, where part
of the pj'oas and iliacus mufcles, with the crural vef-
fels and nerves, pafs. — The large concavity is bound-
ed below by a lharp ridge, which runs from behind
forwards; and being continued with fuch another ridge
of the os pubis , forms a line of partition between the
abdomen and pelvis. — Into this ridge the broad tendon
of the pfoas parvus is inlerted.

All the internal furface of the os ilium , behind this
lidge, is very unequal: For the upper part is flat,
but fpongy, where the facro-lumbalis and longijfunus
dorji rife — Lower down, there is a tranfverle ridge
from which ligaments go out to the os facrum. —
Immediately below this ridge, the rough unequal cavi-
ties

154 Of the SKELETON.

ties and prominences are placed, which are exaCHy
adapted to thofe defcribed on the fide of the os fa-
trum. — In the lame manner, the upper part of this
rough furface is porous, for the firmer adhefion of
the ligamentous cellular fubftance ; while the lower
part is more folid, and covered with a thin cartilagi-
nous fkin, for its immoveable articulation with the
as fctcrum. — From all the circumference of this large
unequal furface, ligaments are extended to the os fa -
crum , to fecurc more firmly the conjunction of thefe
bones.

The paftages of the medullary vefiels are very con-
fpicuous, both in the dorfum and cojla of many ojfa
ilium ; but in others they are inconfiderable.

The pofterior and lower parts of thefe bones are
thick; but they are generally exceeding thin and
compaCt at their middle, where they are expofed to
the aCtions of the mufculi glutaei and iliacus interims ,
and to the preffure of the bowels contained in the
belly. — The fubftance of the ojfa ilium is moftly cellu-
lar, except a thin external table.

In a ripe child, the fpine of the os ilium is cartila-
ginous, and is afterwards joined to the bone in form
of an epipbyfe. The large lower end of this bone is
not compleatly offified.

OS ISCHIUM (d) or lotp-bont, is of a middle bulk
between the two other parts of the os innominatum , is
fituated loweft of the three, and is of a very irregular
figure. — Its extent might be marked by an horizon-
tal line drawn near through the middle of the aceta -
bulum ; for the upper bulbous part of this bone forms
fome lefs than the lower half of that great cavity, and
the fmall leg of it rifes to much the fame height on
the other fide of the great hole common to this bone
and the os pubis.

Front the upper thick part of the os ifehium , a fharp
procefs, called by fome fpinous , (lands out backwards,
from which chietly the mufculus ccccjgteus and fuperior
gemellus , and part of the levator ani} rife ; and the

anterios

{!) Coxz, coxendicis, pixis.

Of the SKELETON. 155

anterior or internal faero-fciatic ligament is fixed to
it. — Between the upper part of this ligament and
the bones, it was formerly obferved that the pyriform
mufclc, the porterior crural vefiels, and the fciatic

nerve, pafs out of the pel-vis . Immediately below

this procefs a finuofity is formed for the tendon of

the vtufculus obturator internus. In a recent fubje£l,

this part of the bone, which ferves as a pully on
which the obturator mufcle plays, is covered with a
ligamentous cartilage, that, by two or three finall
.ridges, points out the interftices of the fibres in the

tendon of this mufcle. The outer furface of the

bone at the root of this fpinous procefs is made •hol-
low by the pyriformis or iliacus exiernus mufcle.

Below the finuofity for the obturator mufcle, 16 the
great knob or - tuberofity , covered with cartilage or
tendon («). — The upper part of the tuberofity gives

rife to the inferior gemellus mufcle. To a ridge at

the infide of this, the external or porter ior facro-fciirt-k
ligament is fo fixed, that between it, the internal li-
gament, and the finuofity of the os ifchiutn , a paffage
is left for the internal obturator mufcle. — The upper
thick fmooth part of the tuber , called by fome its
dorfum , has two oblique impreflions on it. The in-
ner one gives origin to the long head of the biceps
flexor tibia and feminervofus mufcles, and the femi-
membranofus riles fioni the exterior one, which reaches

higher and nearer the acetabulum than the other.

The lower, thinner, more fcabrous part of the knob
which bends forwards, is alfo marked with two flat
furfaces, whereof the internal is what we lean upon
in fitting, and the external gives rife to the largert;
head ot the triceps adduBor femoris. — Between the ex-
ternal margin of the tuberofity and the great hole of
the os imtominatum, there is frequently an obtufe ridge
extended down from the acetabulum , which gives
origin to the quadratus femoris. As the tuber ad-

vances forwards, it becomes fmaller, and is rcugh,
for the origin of the mufculus tranfuerfalis and ereBar

penis .

f<») WiafloH' Exposition anat. dcs os frais, § 96,

156 Of the SKELETON.

penis. — The fmall leg of it, which mounts upwards
to join the os pubis , is rough and prominent at its
edge, where the two lower heads of the triceps or
quadriceps adduBor femoris take their rife.

The upper and back-part of the os ifchium is broad
and thick ; but its lower and fore-part is narrower
and thinner. Its fubftance is of the ftru£lure com-

mon to broad bones.

The os ilium and pubis of the fame fide are the on-
ly bones which are contiguous to the os ifchium.

The part of the os ifchium which forms the acetabu-
lum , the fpinous procefs, the great tuber , and the re-
curved leg, are all cartilaginous at birth. — The tuber ,
with part of the leg, or procefs above it, becomes an
epiphyfe before this bone is fully formed.

The OS PUBIS (b), or flare-bone, is the leaf! of
the three parts of the os innominatum , and is placed
at the upper fore-part of it. — The thick largelt part
of this bone is employed in forming the acetabulum ;
from which becoming much fmaller, it is ftretched
inwards to its fellow of the other fide, where again
it grows larger, and fends a fmall branch downwards
to join the end of the fmall leg of the os ifchium. —
The upper fore-part of each os pubis is tuberous and
rough where the mufculus reBus and pyramidalis are

inferted. From this a ridge is extended along the

upper edge of the bone, in a continued line with fuch
another of the os ilium, which divides the abdomen
and pelvis. The ligament of Fallopius is fixed to the
internal end of this ridge ; and the fmooth hollow
below it, is made by the pfoas and iliacus inter nils
mufcles palling with the anterior crural veflels and
nerves behind the ligament. — Some way below the
former ridge, another is extended from the tuberous
part of the os pubis downwards and outwards towards
the acetabulum; between thefe two ridges the bone is
hollow and fmooth, for lodging the head of the

peBineus mufcle- Immediately below, where the

lower ridge is to take the turn downwards, a winding

niche

(i) pe<ftinis, penis, pudibuodum, feaeftratum.

Of the skeleton. 157

niche is made, which is comprehended in the great
foramen of a Ikeleton, but is formed into a hole by a
fubtended ligament in the recent fubjeft, for the paf-
fage of the pofterior crural', nerve, an artery, and a
vein. — The internal end of the os pubis is rough and.
unequal, for the firmer adhefion of the thick liga-
mentous cartilage that conne&s it to its fellow of the
other fide : — The procefs which goes down from that
to the os ifchium is broad and rough before, where
the gracilis and upper heads of the triceps , or rather
quadriceps addudlor jtmoris have their origin.

The fubflance of the os pubis is the fame as of o-
ther broad bones.

Only a part of the large end of this bone is ofii-
fied, and the whole leg is cartilaginous, in a child
born at the full time.

Betwixt the os ifchium and pubis , a very large irre-
gular hole is lefr, which, from its refemblance to a
door or fhield, has been called th'yroides. This hole
is all, except the niche for the poltevior crural nerve,
filled up in a recent lubjett with a firong ligament-
ous membrane, that adheres very firmly to its cir-
cumference. From this membrane chiefly the two
obturator mufcles, external and internal, fake their
rife — The great defign of this hole, befides render-
ing the bone lighter, is to allow a firong enough o-
rigin to the obturator mufcles, and fufficient fpace for
lodging their bellies, that there may be no danger of
difiurbing the fun£tions of the contained vifeera of
the pelvis by the a£lions of the internal, nor of the
external being bruifed by the thigh-bone, efpecially
by its leffer trochanter , in the motions of the thigh
inwards : Both which inconveniencies muft have hap-
pened, had the ojfa ihnotninala been complete here,
and of fufficient thicknefs and ftrength to ferve as the
fixed point of thefe mufcles; — The bowels fometimes
make their way through the niche for the v.efiels, at
the upper part of this thyroid hole, and this caufes a
hernia in this place (c).

O

(0 Menioircs dc l’acad, de chirurgic, tom, I, p. 709, ire.

In

158 Of the SKELETON.

In the external furface of the ojfa inneminata , near
the outfide of the great hole, a large deep cavity is
formed by all the three bones conjun&ly : For the os
pubis confiitutes about one fifth ; the os ilium makes
fomething lefs than two-fifths, and the os ifchium as
much more than two-fifths. The brims of this ca-
vity are very high, and are (till much more enlarged
by the ligamentous cartilage, with which they are
tipped in a recent fubje£t. From this form of the
cavity it has been called acetabulum ; and for a diflin-
gui fifing character, the name of the bone that con-
llitutcs the largefi: fhare of it is added; therefore ace-
tabulum ojfis ifchii ( d ) is the name this cavity com-
monly bears. Round the bafe of th c jupercilia the

bone is rough and unequal, where the capfular liga-
ment of the articulation is fixed. — The brims at the
upper ami back-part of the acetabulum are much lar-
ger and higher than any where elfe ; which is very ne-
ceflary to prevent the head of the femur from flipping
out of its cavity at this place, where the whole
weight of the body bears upon it, and confequetitly
would otherwife be conftantly in danger of thrufiing
it out. — As thefe brims are extended downwards and
forwards, they become lefs ; and at their internal
lower part a breach is made in them ; from the one
fide of which to the other, a ligament is placed in
the recent fubject ; under which a latge hole is left,
which contains a fatty cellular fubftancc and veffels.
The reafon of which appearance has afforded matter
of debate. To me it feems evidently contrived for
allowing a larger motion to the thigh inwards : For
if the bony brims had been here continued, the neck
of the thigh-bone mull have (truck upon them when
the thighs were brought acrofs each other; which, in
a large ftrong motion this way, would have endan-
gered the neck of the one bone, or brim of the other.
Then the veflels which are diftributed to the joint
may fafely enter at the finuofity in the bottom of the
breach ; which being however larger than is necef-

fary

(d) Qqxx, coxendicb.

*59

Of THE?:'S K E L E T O N.

fary for that purpofe, allows the large mucilaginous
gland of the joint to efcape below the ligament, when
the head of the thigh-bone is in hazard of prefling
too much upon it in the motions of the thigh out-
wards (e). Befides this difference in the height of

the brims, the acetabulum is otherwife unequal : For
the lower internal part of it is deprefled below the
cartilaginous furface of the upper part, and is not
covered with cartilage ; into the upper part of this
particular depreflion, where it is tleepeit, and of a
femilunar form, the ligament of the thigh-bone,
commonly, though improperly, called the round one*
is inferted; while, in its more fupeilicial lower parr,
the large mucilaginous gland of this joint is lodged.
The largeft fliare of this feparate depreflion is formed
in the os ifchium.

From what has been faid of the condition of the
three bones compofing this acetabulum in new-born
children, it muit be evident, that a confiderable part
of this cavity is cartilaginous in them.

The ojfa innominata are joined at their back-part to
each fide of the os facrum by a fort of future, with a
very thin intervening cartilage, which ferves as fo
much glue to cement thefe bones together ; and
ftrong ligaments go from the circumference of this
unequal furface, to conneft them more fiimly. The
ojfa innominata are connected together at their fore-
part by the ligamentous cartilage interpofed between
the two ojfa pubis — Thefe bones can therefore have
no motion in a natural (late, except what is common
to the trunk of the body, or to the os facrum. But
it has been difputed, whether or not they loofen fo
much from each other, and from the os facrum , in
child-birth, by the flow of mucus to the pelvis, and
by the throws of the labour, as that the ojfa pubis re-
cede from each other, and thereby allow the paffag«
between the bones to be enlarged. — Several oblerva-
tions (/ ) (hew that this relaxation fometimes happens :

O 2 But;

( e ) Petit. Mcniolres Je 1’acad. ties tcienccs* 1722.

(!) Baiilun. Theat. anat. lib. 1. cap. 49. — Spigel. Aoat. liu.
cap. 24. — Riolan. Anthropcgr, lib. 6. cap. 12, — Dicmeibrock A rat.
lib. 9. cap. i6<

t6o

Of the SKELETON.

But thofe who had frequently opportunities of direc-
ting the bodies of women who died immediately af-
ter being delivered of children, teach us to beware of
regarding this as the common effedt of child-birth
for they found fuch a relaxation in very few of the
bodies which they examined (b).

Confidering what great weight is fupported in our
cre£f poffure, by the articulation of the ojfa innomi -
nata with the os facrtlm , there is great reafon to think
that if the congluti'nated furfaces of thefe bones were
once feparated, (without which, the ojfa pubis cannot
fhnfile on each other), the ligaments would be vio-
lently flretched, if not torn from whence many dif-
orders would arife (r).

Each os innaminntum affords a focket (the acetabu-
lum) for the thigh-bones to move in, and the trunk
of the body rolls here fo much on the heads of the
thigh-bones, as to allow the moft confpicuous motions
of the trunk, which are commonly thought to be per-
formed by the bones of the fpine. — This articulation
is to be more fully deferibed after the ojfa femoris are
examined.

The pelvis then has a large open above where it is
continued with the abdomen , is ffrongly fenced by
bones on the Tides, back, and fore-part, and appears
with a wide opening below, in the fkeleton ; bur, in
ihc recent lubje£t, a confiderable part of the opening
is filled by the facro-f iatic ligaments, pyriform, inter-
nal obturator, levator cs aniy gemini , and coccygai rauf-
cles, which fupport and proteft the contained parts
better than bones could have done ; fo that fpace is
only left at the lowed part of it, for the large excre-
tories, the vefica urinaria , intejlinum re Plum, and in
females, the uterus, to difeharge themfelves.

The THORAX (d), or chejl, which is the only
part of the trunk of the body which we have not yet

deferibed,

(b) Hildan. Epift. cent. obf. 46.— Dionis Sixieme demon ft. des
OS. — Morgugn. Advert". 3. animad. 15.

(c) L.udov. in Ephcra. German, dec. I. ann. 3. obf. 2JJ.

• O) Ecdtus, cafluin.

Of the SKELETON. i6i

defcribed, reaches from below the neck to the. belly;
and, by means of the bones that guard.it, is formed
int© a large cavity: The figure of which is fomewhat
conoidal ; but its upper fmaller end is not finidied,
being left open for the pafiage of-the wind-pipe, gul-
let, and large blood- veflels ; and its lower part, or
bale, has no bones, and is fhorter before than behind ;
fo that, to carry on our comparifon, it appears like an
oblique fedtion of the conoid. Bcfides which we
ought alfo to remark, that the lower part of this ca-
vity is narrower than fome way above ( e ) ; and that
the middle of its back-part is confiderably diminifhed
bv the bones (landing forwards into it.

The bones which form the thorax, are, the twelve
dorfal vertebra behind, the ribs on the fides, and the
Jlernum before.

The vertebra have already been defcribed as part of
the fpine ; and therefore are now to be palled.

The RIBS, or cojla ( f), (as if they were cvf.odes ,
or guards, to thefe principal organs of the animal
machine, the heart and lungs), are the long
crooked bones placed at the fide of the cheft, in
an oblique diredlion downwards in refpedl of the
back-bone. — Their number is generally twelve on
each fide ; though frequently eleven or thirteen have
been found (g). — Sometimes the ribs are found pre-
ternaturally conjoined or divided (Z>).

The ribs are all concave internally ; where they
are alfo made frnooth by the adlion of the contained
parts, which, on this account, are in no danger of
being hurt by them ; and they are convex externally,
that they might refill that part of the prelfure of the
atmofphere, which is not balanced by the air within
the lungs, during infpirdtion. — The ends of the ribs
next the vertebrae are rounder than they are after thefe
bones have advanced forwards, when they become

O 3 . flatter

(f) Albin. de olfib. feft. 169^

(fj Tlrtupai, ripirrcpva, <rva8at.

(i) Riolan. Comment, de oflrbns, cap. 19. — Marchetti, cap. 9*

Cowper Explicat. tab. 93. and 94, — Morgagu. Advert, an at.

(h) Sue Trad, d’oftsolog. p. 141,

162

Of the SKELETON.

flatter and broader, and have an upper and lower
edge, each of which is made rough by the action of
the intercojial mufcles, inferted into them. Thefe
mufcles, being all of nearly equal force, and equally
flretched in the interftices of the ribs, prevent the
broken ends of thefe bones in a frafture from being
removed far out of their natural place, to interrupt
the motion of the vital organs. — The upper edge of
the ribs is more obtufe and rounder than the lower,
which is depreffed on its internal fide by a long fojfa,
for lodging the intercoftal vefl'els and nerves ; on each
fide of which there is a ridge, to which the intercoft-
al mulcfes are fixed. The fojfa is not obfervable
however at either end of the ribs ; for at the pofte-
rior or root, the vefTels have not yet reached the ribs ;
and, at the fore-end, they are fplit away into branches,
to ferve the parts between the ribs : Which plainly
teaches furgtons one reafon of the greater fafety of
performing the operation of the tmpyema towards the
iides of the thorax, than cither near the back or the
bread:.

At rhe poflerior end (r) of each rib, a little head
3s formed, which is divided by a middle ridge into
two plain or hollow furfaces ; the lowed of which is
the broadeft and deepeft in moft of them. The two
planes are joined to the bodies of tvro different verte-
brae, and the ridge forces itfelf into the intervening
cartilage. — A little way from this head, we find, on
the external furface, a fmall cavity, where mucilagi-
nous glands are lodged ; and round the head, the bone
appears fpongy, where the capfular ligament of the
articulation is fixed. — Immediately beyond this a flat-
ted tubercle rifes, with a fmall cavity at, and rough-
nefs about its root, for the articulation of the rib
with the tranfverfe procefs of the lowed of the two
vertebrae, with the bodies of which the head of the
rib is joined. — Advancing farther on this external
furface, we obferve in moft of the ribs another fmal-
ler tubercle, into which ligaments which conne£l the

(0 Kw.nov, rcantlus.

Op the SKELETON. i 6%

ribs to each other, and to the tranfverfe procefles of
the vertebrae and portions of the hngiffimus dotfty are
inferted. — Beyond this the ribs are made flat by the
facro-lumbalis mufcle, which is inferted into the part
of this flat furface fartheft from the fpine, where each
rib makes a confiderable curve, called by fome its
angle. — Then the rib begins to turn broad, and conti-
nues fo to its anterior end, (k), which is hollow and
fpongy, for the reception of, and firm coalition with
the cartilage that runs thence to be inferted into the
Jlertmtn, or to be joined with fome other cartilage. —
in adults, generally the cavity at this end of the ribs
is fmooth and polilhed on its furface ; by which the
articulation of the cartilage with it has the appearance
of being defigned for motion : hut it has none.

The fubftance of the ribs is fpongy, cellular, and
only covered with a very thin external lamellated
furface, which increafes in thicknefs and flrength ns
it approaches the vertebra.

To the fore-end of each rib, a long broad and
flrong cartilage is fixed, and reaches thence to the
Jlermtm , or is joined to the cartilage of the next rib.
This courfe, however, is not in a ftraight line with
the rib \ for, generally, the cartilages make a confi-
derable curve, the concave part of which is upwards;
therefore, at their infertion into the Jberttum , they
make an obtufe angle above, and an acute one be-
low.— Thefe cartilages are of fuch a length as never
to allow the ribs to come to a right angle with the
fpine ; but they keep them fituated fo obliquely, as
to make an angle very confiderably obtufe above, till
a force exceeding the elafticity of the cartilages is
applied — Thefe cartilages, as all others, are firmer
and harder internally, than they are on their external
furface ; and fometimes in old people, all their mid-
dle fubftance becomes bony, while a thin cartilagi-
nous lamella appears externally (a). The oflification,
however, begins frequently at the external furface. —

The

(fc) nxarn, palmula.

(a) Vcfal. lib. a. cap. 19.

1 64 Of the SKELETON.

The greateft alternate motions of the cartilages be-
ing made at their great curvature, that part remains
frequently cartilaginous, after all the reft is olfi-
lied (b).

The ribs then are articulated at each end, of
which the one behind is doubly joined to the verte-
bra ; for the head is received into the cavities of two
bodies of the vertebra , and the larger tubercle is re-
ceived into the depreflion in the tranfverfe procefs of
the lower vertebra. — When one examines the double
articulation, he mult immediately fee, that no other
motion can here be allowed than upwards and down-
wards ; fince the tranfverfe procefs hinders the rib
to be thruft back ; the refiftance on the other fide of
the Jlernum prevents the rib’s coming forward ; and
each of the two joints, with the othet parts attach-
ed, oppofe its turning round. But then it is like-
wife as evident, that even the motion upwards and
downwards can be but fmall in any one rib at the
articulation itfelf. But as the ribs advance forwards,
the diftance from their centre of motion increafing,
the motion mull be larger •, and it would be very
confpicuous at their anterior ends, were not they re-
filled there by the cartilages, which yield fo little,
that the principal motion is performed by the middle
part of the ribs, which turns outwards and upwards,
and occafions the twill remarkable in the long ribs
at the place near their fore-end where they are molt
refilled (r).

Hitherto I have laid down the ltru£ture and con-
nection which moll of the ribs enjoy, as belonging to
all of them ; but mull now confider the fpecialities
wherein any of them differ from the general defcrip-
tion given, or from each other.

In viewing the ribs from above downwards, their
figure is Hill ftraighter ; the uppermoft being the
ntoft crooked of any. — Their obliquity, in refpe£l of
the fpine, increafes as they defcend ■, fo that though

their

( i ) Havers Ofteolog. nov. dife. 5. p. 289.

(c) Winflow Memoircs de l’acad. des fdcnces, 1720..

Of the SKELETON. 165

their diftances from each other is very little different
at their back-part, yet at their fore-ends the diftances
between the lower ones muft increafe.- — In confe-
quence, too, of this increafed obliquity of the lower
ribs, each of their cartilages makes a greater curve in
its progrefs from the rib towards the Jiernum and
the tubercles, that are articulated to the tranfverfe
procefles of the vertebra , have their fmooth furfaces
gradually facing more upwards — The ribs becoming
thus more oblique, while the Jiernum advances for-
wards in its defcent, makes the diftance between the
Jiernum and the anterior end of the lower ribs greater
than between the Jiernum and the ribs above ; con-
fequently the cartilages of thofe ribs that are joined
to the breaft-bone, are longer in the lower than in
the higher ones. — Thefe cartilages are placed nearer
to each other as the ribs defcend, which occafions the
curvature of the cartilages to be greater.

The length of the ribs increases from the firft and
uppermoft rib, as far down as the feventh ; and
from that to the twelfth, as gradually diminifties. —
The fuperior of the two plain, or rather hollow fur-
faces, by which the ribs are articulated to the bodies
of the vertebra, gradually increafes from the firft to
the fourth rib, and is diminiflred after that in each
lower rib. — The diftance of their angles from the
heads always increafes as they defcend to the ninth,
becaufe of the greater breadth of the facro-lumbalis
rnufcle (d).

The ribs are commonly divided into true and falfe.

The true ( e ) cojlae are the feven upper ones of each
fide, whole cartilages are all gradually longer as the
ribs defcend, and are joined to the breaft-bone •, fo
that being preffed conftantly between two bones,
they are flatted at both ends, and are thicker, harder,
and more liable to offify, than the other cartilages,
that are not fubjcft to fo much preffure. Thefe ribs

include

(d) Window F xpofition atratomique des os fees,, § 64^,
(r) r ir.trcu, Gcrmanae, legitims.

1 66 Of the SKELETON.

include the heart and lungs ; and therefore are the
proper or true cujlodes of life.

- The five inferior ribs of each fide are the falje or
BASTARD ( f)y whofe cartilages do not reach to
the Jlernum ; and therefore, wanting the refiftance at
their fore-part, they are there pointed ; and, on this
account, having lefs preffurc, their fubltance is foft-
er. — The cartilages of thefe falje ribs are fhorter as
the ribs defcend. — To all thefe five ribs the circular
edge of the diaphragm is connected ; and its fibres,
inftead of being flretched immediately tranfverfely,
and fo running perpendicular to the ribs, are prefied
fo as to be often, efpecially in exfpiration, parallel to
the plane in which the ribs lie : Nay, one may judge
by the attachments which thefe fibres have fo fre-
quently to the fides of the thorax . a confulerable way
above where their extremities are inferred into the
ribs, and by the fituation of the vijcera , always to be
obferved in a dead fubject laid fupine, that there is
conftantly a large concavity formed on each fide by
the diaphragm within thefe baftard ribs, in which the
ftomach, liver, fplecn, fcsV. are contained ; which,
being only reckoned among the vifcera naturalia , have
©ccafioned the name of bajlard cujlodes to thefe bones.

Hence, in fimple fra&ures of the falfe ribs, with-
out fever, the ftomach ought to be kept moderately
filled with food, left the pendulous ribs falling in-
wards, fhould thereby increafe the pain, cough,
& c . (g). — Hence likewife we may learn how to judge
better of the feat of fevcral difeafes, and to do the
operation of the empyema , and fome others, with
more fafety than we can do, if we follow the com-
mon di regions.

The eight upper ribs were formerly (h) claffed in-
to pairs, with particular names to each two, to wit,

the

(/) MxxSaxa;, ^ovipoiti f, *x«v6«i, xhnc, poou, adulterine, fpuria:,
Jllcgitim*.

(g) Hippocrat. de articulo, § JI. — Pare, lib. 15. cap. II.

(h) Laurent. Hid- an at. lib. a. cap. *9.— Paaw de oflibus, par. 3.
cap. a.

Of the- SKELETON". i6y

the crocked, the /olid, the pcBoral , the twijled : But
thefe names are of fo little ufe, that they are now
generally negle&ed.

The firjl rib of each fide is fo fituated, that the
flat fides are above and below, while one edge is
placed inwards, and the other outwards, or nearly fo ;
therefore, fufficient fpace is left above it for the fub-
clavian veflels and mufcle ; and the broad concave
furface is oppofed to the lungs : But then, in confe-
quence of this fituation, the channel for the inter-
coflal veflels is not to be found, and the edges. are
differently formed from all the other, except the fe-
cond ; the lower one being rounded, and the other
fharp. — The head of this rib is not divided into two
plain furfaces by a middle ridge, becaufe it is only
•articulated with the fiill vertebra of the thorax. — Its
cartilage is oflified in adults, and is united to the
Jlernum at right angles. — Frequently this firft rib has
a ridge riling near the middle of its pofterior edge,
where one of the heads of the fcalentts mufcle rifes. —
Farther forward it is flatted, or fometimes deprefl'ed
by the clavicle.

The fifth, fixth, and feventh, or rather the fixth,
feventh, eighth, and fometimes the fifth, fixth, fe-
venth, eighth, ninth ribs, have their cartilages at leaft
contiguous 5 and frequently they are joined to each
other by crofs cartilages ; and moll commonly the
cartilages of the eighth, ninth, tenth, are connect-
ed to the former and to each other. by firm liga-
ments.

The eleventh, and fometimes the tenth rib, has no
tubercle for its articulation with the tranfverfe pro-
cefs of the vertebra, to which it is only loofely fixed
by ligaments. — f he fojfa in its lower edge is not fo
deep as in the upper ribs, becaufe the veflels run
more towards the interface between the ribs. — Its
foie-end is fmaller than its body, and its fbort fmall
cartilage is but loofely connected to the cartilage of
the xib above.

The

Of the SKELETON.

i 68

The twelfth rib is the fliortefl: and ftraighteft. — Its
head is only articulated with the laft vertebra of the
thorax ; therefore is not divided into two furfaces. —
This rib is not joined to the tranfverfe procefs of the
vertebra , and therefore has no tubercle, being often
pulled neceflarily inwards by the diaphragm, which
an articulation with the tranfverfe procefs would not
have allowed. — The fojfa is not found at its under-
edge, becaufe the vefiels run below it. — The fore-
part of this rib is fmaller than its middle, and has
only a very fmall pointed cartilage fixed to it. — To
its whole internal fide the diaphragm is connected.

The motions and ufes of the ribs fhall be more
particularly treated of, after the defcription of the
jjermim.

The. heads and tubercles of the ribs of a new-
born child have cartilages on them ; part of which
becomes afterwards thin epiphytes. — The bodies of
the libs encroach gradually after birth upon the car-
tilages ; fo that the latter are proportionally fhorter,
when compared to the ribs, in adults, than in chil-
dren.

Here I cannot help remarking the wife providence
of our Creator, in preferving us from perifhing as
foon as we come into the world. The end of the
bones of the limbs remain in a cartilaginous Hate
after birth, and are many years before they are en-
tirely united to the main body of their feveral bones ;
whereas, the condyles of the occipital bone, and of
the lower jaw, are true original procefies, and ofiified
before birth, and the heads and tubercles of the ribs
are nearly in the fame condition *, and therefore, the
weight of the large head is firmly fupported \ the
actions of lucking, fwallowing, refpiration, dsV.
which are indifpenfably necefiary for us as foon as
we come into the wrorld, are performed without
danger of feparating the parts of the bones that are
moll prefled on in thefe motions : Whereas, had
thefe procefies of the head, jaw, and ribs, been
epiphytes at birth, children mult have been expofed

to

Of the SKELETON. 169

to danger of dying by fuch a reparation ; the imme-
diate confequences of which would be, the comprefi-
fion of the beginning of the fpinal marrow, or want
of food, or a flop put to refpiration.

The STERNUM (i), or breajl-bone , is the broad
flat bone, or pile of bones, at the fore-part of the
thorax. — The number of bones which this fhould be
divided into, has occafioned debates among anato-
mifts, who have confidered it in fubjecfts of different
ages. — In adults of a middle age, it is compofed of
three bones, which eafily feparate after the cartilages
connecting them are deftroyed. Frequently the two
lower bones are found intimately united ; and very
often in old people, the Jiernum is a continued bony
fubftance from one end to the other; though we'ftill
obferve two, fometimes three tranl'verfe lines on its
furface ; which are marks of the former divifions.

When we conffder the Jiernum as one bone, we
find it broadeft and thickeft above, and becoming
finaller as it defeends. The internal furface of this
bone is fomewhat hollowed for enlarging the thorax ;
but the convexity on the external furface is not fo
confpicuous, becaufe the fides are prefled outwards
by the true ribs ; the round heads of whole carti-
lages are received into feven fmooth pits, formed in
each fide of the Jiernum , and are kept firm there by
flrong ligaments, which on the external furface have
a particular radiated texture (£). — Frequently the
cartilaginous fibres thruft themfelves into the bony
fubftance of the Jiernum, and are joined by a fort of
future. — The pits at the upper part of the Jiernum
are at the greateft diftance one from another, and, as
they defeend, are nearer ; fo that the two loweft are
contiguous.

The fubftance of the breaft-bone is cellular, with
a very thin external plate, efpecially on its internal
furface, where we may frequently obferve a cartilagi-

P nous

(i) 2r»8oc, os peftoris, enfiforme, feutum cordis,
(i) Ruyich. Catalog, rar. fig. 9.

170 Of the SKELETON.

nous cruft fpread over it (/). On both furfaces, how-
ever, a ftrong ligamentous membrane is clofely bra-
ced ; and the cells of this bone are fo fmall, that a
confulerable quantity of ofteous fibres muft be em-
ployed in the compofition of it : Whence, with the
defence which the mufcles give it, and the moveable
fupport it has from the cartilages, it is fuificiently fe-
cured from being broken ; for it is ftrong by its
quantity of bone •, its parts are kept together by li-
gaments ; and it yields enough to dude confiderably *
the violence offered ( m ).

So far may be faid of this bone in general ; but
the three bones, of which, according to the common
account, it is compofed in adults, are each to be exa-
mined. '

The firjl, all agree, is fomewhat of the figure of a
heart, as it is commonly painted ; only it does not
terminate in a (harp point. — This is the uppermoft
thickeft part of th ejlernum.

The upper middle part of this firft bone, where it
is thickeft, is hollowed, to make place for the trachea
arteria ; though this cavity («) is principally formed
by the bone being raifed on each fide of it, partly by
the clavicles thrufting it inwards, and partly by the
jlerno-majicidei mufcles pulling it upwards. — On the
outlide of each tubercle, there is an oblong cavity,
that, in viewing it tranfvcrfely from before back-
wards, appears a little convex : Into thefe glen*, the
ends of the clavicles are received. — Immediately be-
low thefe, the Tides of this bone begin to turn thin-
ner *, and in each a fuperficial cavity or a rough fur-
face is to be feen, where the firft ribs are received or
joined to the Jlernum . — In the fide of the under end
of this firft bone, the half of the pit for the fecoml
rib on each fide is formed. — The upper part of the
/'urface behind is covered with a ftrong ligament,

which

(/) Jac. Sylv. in Galen dc offibus, cap. 12.

(ni) Secac. in Memoires de l’acad. des fciences, 17*4'
(«) Jpayi i, jugulum, furcula fuperior.

1

Of the SKELETON. 171

which fecures the clavicles ; and is afterwards to be
more particularly taken notice of.

The fecond or middle divifion of this bone, is
much longer, narrower, and thinner, than the firfl ;
but, excepting that it is a little narrower above than
below, it is nearly equal all over in its dimenfions of
breadth or thicknefs. — In the fides of it are complete
pits for the third, fourth, fifth, and fixth ribs, and
an half of the pits for the fecond and feventh. ’1 he
lines, which are marks of the former divifion of this
bone, being extended from the middle of the pits of
one fide to the middle of the correfponding pits of
the other fide. — Near its middle an unoflified part of
the bone is fometimes found, which, freed of the liga-
mentous membrane or cartilage that fills it, is de-
fcribed as a hole ; and in this place, for the molt
part, we may obferve a tranfverl'e line, which has
made authors divide this bone into two. — When
the oartilage between this and the firfl: bone is not
oflified, a manifefl motion of this upon the firfl may
be obferved in refpiration, or in railing the fternumy
by pulling the ribs upwards, or diflending the lungs
with air in a recent fubjedl.

The third bone is much lei's than the other two,
and has only one half of the joit for the feventh rib
formed in it ; wherefore it might be reckoned only
an appendix of the Jiernum. — In young fubjecls it is
always cartilaginous, and is better known by the
name of cartilago xiphoides or erfiformis ( 0 ), than any
other; though the ancients often called the whole
Jiernum , enjforme , comparing the two firfl bones to
the handle, and this appendix to the blade of a fword. —
This third bone is leldom of the fame figure, magni-
tude, or fituation in any two fubjedls ; for fometimes
it is a plain triangular bone, with one of the angles
below, and perpendicular to the middle of the up-
per fide, by which it is connedlcd to the fecond bone. — -

Pa In

(0) Clypcalis, glailialis, mr.cronata, malum granatum, feutum fto-
macl.i, epigloctalis, cultralis, medium furculas iniudotis, foiafuwnii,
enficuiau.

0

172

Gf the SKELETON.

In other people, the point is turned to one fide, or
obliquely forwards or backwards. — Frequently it is
all nearly of an equal breadth, and in feveral fub-
je£ts it is bifurcated; whence fome writers give it
the name of furcella or furcula inferior ; or elfe it is
unoffified, in the middle. — In the greateft number of
adults it is offified, and tipped with a cartilage ; in
fome, one half of it is cartilaginous, and in others,
it is all in a cartilaginous ftate. — Generally, feveral
oblique ligaments fixed at one end to the cartilages
of the ribs, and by the other to the outer furface of
the xiphoid bone, connect it firmly to thofe carti-
lages (/>).

So many different ways this ftnall bone may be
formed, without any inconvenience : But then fome
of thefe pofitions may be fo directed, as to bring on
a great train of ill confequences ; particularly, when
the lower end is olfified, and is too much turned out-
wards or inwards (y), or when the conjunction of
this appendix with the fecond bone is too weak (r).

The Jlernum is joined by cartilages to the feven
upper ribs, unlcfs when the firit coalefces with it in
an intimate union of fubftance : And its unequal
cavity on each fide of its upper end is fitted for the
ends of the clavicles.

The Jlernum molt frequently has four round fmall
hones, furrounded with cartilage, in children born
at the full time ; the uppermost of thefe, which is
the fi rft bone, being the largeft. — Two or three other
very fmall bony points are likewife to be feen in fe-
veral children. — The number of bones increafes for
fome years, and then diminiihes, but uncertainly, till
they are at laft united into thofe above deferibed of an
adult.

The

(j>) Weitbrecht, Syndefmolog. p. 121.

(?) Rolfinc. DLflcrt. anat. lib. 2. cap. 41 —Pa™ de offib. par.
r. cap. 3. & par. 3. cap. 3. — Codronchi de prolaplii cartilagin.
mucronat.

(r) Paaw, ibid.— Borrich. aft. Hafn. vol. 3. «b. 79.— Bonet. Sc-
pulchret. anat. 10m. 2. lib. 3‘ § i* Append, ad obf. 8. ct. ibid. § 7*
obf. 19.

173

Of the SKELETON.

The ufes of this bone are, to afford origin and in-
sertion to feveral mufcles *, to fuftain the tnediafinum ,
to defend the vital organs, the heart and lungs, at
the fore-part ; and, laftly, by ferving as a moveable
fulcrum of the ribs, to affift confiderably in refpiration :
Which action, fo far as it depends on the motion of
the bones, we are now at liberty to explain.

When the ribs that are connected by their cartilages
to the Jlernum , or to the cartilages of the true ribs,
are a£ted upon by the intercoftal mufcles, they muft
all be pulled from the oblique pofition which their
cartilages kept them in, nearer to right angles wirh-
the vertebrae and Jlernum , becaufe the firft or upper-
moft rib is by much the moft fixed of any ; and the.
cartilages making a great refiftance to raifing the an-
terior ends of the ribs, their large arched middle
parts turn outwards as well as upwards. — The Jler -
tiutn , preffed ftrongly on both fides by the cartilages
of the ribs, is puflied forwards, and that at its feveral
parts, in proportion to the length and motion of its-
fupporters, the ribs; that is, moft at its lower end. —
The fernum and the cartilages, thus raifed forwards,,
muft draw the diaphragm connected to them ; con-
sequently fo far ftretch it, and bring it nearer to a
plane. — The power that raifes this bone and the car-
tilages, fixes them fufficiently to make them refill the
a£lion of the diaphragm , whofe fibres contradl at the.
fame time, and thruft the vtfeera of the abdomen
downwards. — The arched part of the ribs being thus-
moved outwards, their anterior ends and the Jlernum
being advanced forwards, and the diaphragm being
brought nearer to a plain furface, inftead of being
greatly convex on each fide within each cavity of the
thorax, it is evident how confiderably the cavity, of
which the nine or ten upper ribs are the fides, muffc
be widened, and made deeper and longer. — While:
this is doing in the upper ribs, the lower ones, whofe
cartilages are not joined to the fernum or to other
cartilages, move very differently, though they con-
fute to the fame intention, the enlargement of the;

T 3, thar-ax z

*74 Of the SKELETON

thorax : For having no fixed point to which their an-
terior ends are fattened, and the diaphragm being in-
ferted into them at the place where it runs pretty
ftraight upwards from its origin at the vertcbrr,
thefe ribs are drawn downwards by this ftrong muf-
ele, and by the mufcles of the abdomen , which, at
this time, are refilling the ftretching force of the
bowels ; while the intercollal mufcles are pulling them
in the contrary direction, to wit, upwards : The ef-
fect therefore of either of thefe powers, which are
nntagonitts to each other, is very little, as to mov-
ing the ribs either up or down ; but the mufcles of
the abdomen , pufhed at this time outwards by the vif-
cera , carry thefe ribs along with them. — Thus the
thorax is not only not allowed to be fhortened, but is
really widened at its lower part, to alfifl in making
fufficient fpace for the due diftesnfion of the lungs.

As foon as theaclion of thefe feveral mufcles ceafes,
the elattic cartilages, extending themfelves to their
natural fituation, deprefs the upper ribs, and th ejier-
nmn fubfides; — the diaphragm is thruft up by the vif-
cera abdominalia, and the oblique and tranfverfe muf-
cles of the belly ferve to draw the inferior ribs in-
wards at the fame time. — By thefe caufes, thextavity
of the bread is diminifhed in all its dimenfions.

Though the motions above defciibed of the ribs
and Jlemum , efpecially of the latter bone, are fo
fmall in the mild refpiration of a healthy perfon, that
we can fcarce obferve them *, yet they are manifeft
whenever we defignedly increafe our refpiration, or
are obliged to do it after exercife, and in feveral
difeafes.

Of the SUPERIOR EXTREMITIES.

AUthors are much divided in their opinions about
the number of bones which e zch fuperior extre-
mity {a) fhould be faid to confift of, fomc deferibing

the

(a) Ku>xa, yupi) ixfva tc(j Enata, adnata, explantata membra,
atus.

Of the SKELETON.

*75

the clavicle anti fcapula as part of it, others clafling
thefe two bones with thofe of the thorax : But fmce
mod quadrupeds have no clavicles , and the human
thorax can perform its funftions right when the fcapula
is taken away (£), whereas it is impoflible for us to
have the right ufe of our arms without thefe bones ;
I mud think that they belong to the fuperior extremi-
ties ; and therefore fhall divide each of them into the
Jhaulder , arm , fore-arm , and hand.

The SHOULDER confids of the clavicle and fca-
puln.

CLAVICULA , or collar-bone (r), is the long crook-
ed bone, in figure like an Italic f placed almod hori-
zontally between the upper lateral part of the Jlermrm%
and what is commonly called thfe top of the fhoulder,
which, as a clavis or beam, it beais off from the trunk
of the body.

The clavicle , as well as other long round bones, is
larger at its two ends, than in the middle. The end
next to the flemum (d) is triangular: The angle be-
hind is considerably produced, to form a fharp ridge,
to which the tranfverle ligament, extended from one
clavicle to the other, is fixed ( e ). — The fide oppofite
to this is fomewhat rounded. — The middle of this
protuberant end is as irregularly hollowed, as the cti-
vity in the Jlernum for receiving it is raifed^ but in
a recent fubjeft, the irregular concavities of both are
fupplied by a moveable cartilage, which is not only
much more clofely connected every where by liga-
ments to the circumference of the articulation, than
thofe of the lower jaw are; but it grows to the two
bones at both its internal and external end ; its
fubflance at the internal end being foft, but very ftrong,
and refembling the intervertebral cartilages (f).

From

(i) Philofoph. tranfaft. numb. 449. § 5.

(c) Os jugularc, jugulum, furcula, ligula, clavis, humerus qui-
bui'datn.

( d ) riapao-payif.

(0 Riolan. Encheirid. anat. lib. 6. cap. 13. — Winflpw, cxpof.
anat. des os irais, § 248. — Weitbrecht, Aft. Pctropolit. tom. 4. p,
255. et Syndcfmolog. feft. 2. I. § 3.

(f) Weitbrecht, Syadcfmolog. left, ». I. feft 6,

17 6 Of the SKELETON.

From this internal end, the clavicle, for about two
fifths of its length, is bended obliquely forwards and
downwards. On the upper and fore-part of this cur-
vature a fmall ridge is feen, with a plain rough fur-
face before it ; whence the mufculus Jlerno-hyoideus and
Jlerno-maJloideus have in part their origin. — Near the
lower angle a fmall plain furface is often to be remark-
ed, where the firft rib and this bone are contiguous
(g), and are connected by a firm ligament ( h ). — From
this a rough plain furface is extended outwards, where
the pectoral mufcle has part of its oiigin. — Behind,
the bone is made flat and rough by the infertion of
the larger (hare of the fubclavian mufcle. — After the
clavicle begins to be bended backwards, it is round,
but fdbn after becomes broad and thin ; which fhape
it retains to its external end. — Along the external
concavity, a rough finuofity runs, from which fome
part of the deltoid mufcle takes its rife: — Oppofite
to this, on the convex edge, a fcabrous ridge gives
infertion to a (hare of the cucullaris mufcle. The up-
per furface of the clavicle here is flat ; but the lower
is hollow, for lodging the beginning of the mufculus
fubclavius and towards its back-part a tubercle rifes,,
to which, and a roughn'efs near it, the ftrong Ihort
thick ligament connecting this bone to tire coracoid
procefs of the fcapula is fixed.

The external end (*) of this bone is horizontally,
oblong, fmooth, doping at the pofterior fide, and
tipped in a recent fubject with a cartilage, for its ar-
ticulation with the acromion fcapula. — Round this the
bone is fpongy, for the firmer connection of the liga-
ments.

The medullary arteries, having their direction
obliquely outwards, enter the clavicles by one or
more fmall paflages in the middle of their back-part.

The fubftance of this bone is the fame as of the
other round long bones.

The-

(g) Dionis, Sixieme demonft. dfs os.

( b ) Weitbrecht, Syadctmolog. feft. 2. I. § 7,
(j) Etw^/£,

r'/7

Of the SKELETON.

The triangular unequal interior end of each clavicle. ,
has the cartilage above defcribecl interpofed betwixt
it and the irregular cavity of the Jlermtm. — The liga-
ments, which furround this articulation to fecure it,
are fo fhort and ftrong, that little motion can be al-
lowed any way ; and the ftrong ligament that is
ftretched acrofs the upper furcula of the Jiernum , from
the pofterior prominent angle of the one clavicle, to
the fame place of the other clavicle, ferves to keep
each of thefe bones more firmly in their place. — By
the afliftance, however, of the moveable intervening
cartilage, the clavicle can, at this joint, be raifed or
deprefled, and moved backwards and forwards fo
much, as that the external end, which is at a great
diftance from that axis, enjoys very confpicuous mo-
tions.— The articulation of the exterior end of the
clavicle fliall be confidered after the defcription of
the fcapula.

The clavicles of infants are not deficient in any of
their parts ; nor have they any epiphyfes at their ex-
tremities joined afterwards to their bodies, as moft
other fuch long bones have, which preferves them
from being bended too much, and from the danger
of any unoflified parts being feparated by the force
which pulls the arms forwards.

The ufes of the clavicles are, to keep the fcapulaey
and confequently all the fuperior extremities , from
falling in and forward upon the thorax ; by which,
as in moft quadrupeds, the motions of the arms would
be much confined, and the breaft made too narrow.
— The clavicles likewife afford origin to feveral muf-
cles, and a defence to large veflels.

From the fituation, figure, and ufe of the clavicles,
it is evident, that they are much expofed to fra&ures j
that their broken parts muft generally go by each o-
ther; and that they are difficultly kept in their
place afterwards.

SCAPULA^ or Jhoulder- blade (b)y is the triangular

bone

(b) n,u.t>r\aT>>f, ixivktiov, latitudo humeri, fccptulum vel fcutu-,
lum opcitum, ljwtula, ala,, humerus, clypcus, feutum thoracis..

178 Of the SKELETON.

bone fituated on the outfide of the ribs, with its
longed fide called its bafe , towards the fpinal procef-
fes of the vertebrae , and with the angle .at the upper
part of this fide about three inches, and the lower
angle at a greater didance from thefe procefles. — The
back-part of the fcapula has nothing but the thin ends
ol the ferratus anticus major and fubfcapuluris mufcles
between it and the ribs : But as this bone advances

forwards, its didance from the ribs iucreafes -The

upper or fhorted fide, called the fuperior cojla of the
fcapula is nearly horizontal, and parallel with the fe-
cond rib. — The lower fide, which is named the infe-
rior cojla , is extended obliquely from the third to the
eighth rib. — The fituation of this bone here defcribcd,
is when people are fitting or danding in a date of in-
adfivity, and allowing the members to remain in the
mod natural eafy podure. — The inferior angle of the
fcapula is very acute ; the upper one is near to a right
angle $ and what is called the anterior, does not de-
ferve the name, for the two fides do not meet to form
an angle. — The body of this bone is concave towards
the ribs, and convex behind, where it has the name
of dorfum (r). — Three procefles are generally reckon-
ed to proceed from the fcapula. — The fird is the large
fpine that riles from its convex furfacc behind, and
divides it unequally. — The fecond procefs dands out
(rom the fore-part of the upper fide; and, from its
imaginary refemblance to a crow’s beak, is named
coracoides (d). — The third procefs is the whole thick
bulbous fore-part of the bone.

After thus naming the fevtral condituent parts of
the fcapula, the particular defeription will be more
eafily underdood.

The bafe, which is tipped with cartilage in a young
fubjedl, is not all draight: For above the fpine, it
runs obliquely forwards to the fuperior angle ; that
here it might not be too protuberant backwards, and
(o bruife the mufcles and teguments : Into the ob-
lique

(r) XtXinov.

\d) Anchoroidcs, tigmoides, digitalis, anciftroidcs.

Or tjhe SKELETON". 179

lique fpace the mufculus patientice is inferted. At the
root of the fpine, on the back-part of the bafe, a tri-
angular plain furface is formed, by the preflfure
of the lower fibres of the trapezius. — Below this the
■edge of the fcapttla is fcabrous and rough-, for the in-
fertion of the ferratus major anticus and rhomboid
mufcles.

The back-part of the inferior angle is madefmooth
by the latiffimus dorfi palling over it. This mufcle
alfo alters the dire&ion of the inferior cojia fome way
forwards from this angle : and fo far it is flatted be-
hind by the origin of the teres major. — As the inferior
cojia advances forward, it is of confiderable thickrrefs,
is llightly hollowed and made lmooth behind by the
teres minor, while it has a J'oJfa formed into it below
by part of the fubfcapularis ; and between the two a
ridge with a fmall depreflion appears, where the lon-
gue extenfor cubiti has its origin.

The ftperior cojia is very thin ; and near its fore-
part there is a femilunar niche, from one end of which
to the other a ligament is ftretched ; and fometimes
the bone is continued, to form one, or fometimes two
holes for the pafiage of the fcapular blood-veflels and
nerves. — Immediately behind this femilunar cavity the
coraco-hyoid mufcle has its rife. — From the niche to the
termination of the fojfa for the teres minor , the fcapula
is narrower than any where elfe, and fupports the
third procefs. This part has the name of cervix.

The whole dorfum of the fcapula is always faid to
be convex ; but, by reafon of the raifed edges that
furround it, it is divided into two cavities by the
fpine, which is ftretched from behind forwards, much
nearer to the fuperior than to the inferior cojia. — The
cavity above the fpine is really concave where the fu-
pra-fpinatus mufcle is lodged ; while the furface of
this bone below the fpine, on which the infra-fpina -
tus mufcle is placed, is convex, except a fojfa that
runs at the fide of the inferior cojia.

rI he internal or anterior furface of this bone is hol-
low, except in the part above the fpine, which is

convex.—

z8o Of the SKELETON.

convex. — The fubfcapularis mufcle is extended over
this furface, where it forms feveral ridges and inter-
mediate deprefltons, commonly miftaken for prints
of the ribs ; they point out the interfaces of the bun-
dles of fibres of which the fubjcapulciris mufcle is com-
pofed (e).

The fpine (f) rifes fmall at the bafe of the fcapula,
and becomes higher and broader as it advances for-
wards.— On the fides it is unequally hollowed and
crooked, by the a£lions of the adjacent mufcles. — Its
ridge ( g ) is divided into two rough flat furfaces : In-
to the upper one, the trapezius mufcle is inferted ;
and the lower one has part of the deltoid fixed to it. —
The end of the fpine, called acromion (h), or top of
the fhoulder, is broad and flat, and is fometimes on-
ly joined to the fpine by a cartilage (/'). — The anterior
edge %of the acromion is flat, finooth, and covered
with a cartilage, for its articulation with the external
end of the clavicle ; and it is hollowed below, to allow
a pafl'age to the infra and fupra Jpinafi mufcles, and
free motion to the os humeri.

The coracoid (i) procefs is crooked, with its point
inclining forwards j fo that a hollow is left at the
lower fide of its root, for the pafl'age of the infra-fca-
pularis mufcle. — The end of this procefs is marked with
three plain futfaces. Into the internal, th c ferratus
minor anticus is inferted : From the external, one head
of the biceps flexor cubiti rifes ; and from the lower
one, the coraco-brachialis has its origin. — At the up-
per part of the root of this procefs, immediately be-
fore the femilunar cavity, a fmooth tubercle appears,
where a ligament from the clavicle is fixed, from
all the external fide of this coracoid apoph\fey a broad
ligament goes out, which becomes narrower where

it

(f) Window, in Memoires de l’acad. des feienees, 1722.

(f) vxifox1 ’oporKaTov, eminentia fcapnlarum.

( g ) Pterigium, crilla.

E 7fu/jU( ayx.upo(i£*f 1 xopuxotiSufj xuT&Y.Kttfj ACromii OSj film*

mus armus, rolhum porcinum, proceflus digitalis.

(i) SucTrad. d’Olleol. p. 160 4

(i) 'AyxvfotiJni, viyp-idlrS) roftriionnis.

1 8 r

Of the S K E L E T O N.

it is fixed to the acromion. — Ihe fharp pain, vio-
lent inflammation, and tedious cure of contufions in
this part, are probably owing to thefe tendons and
ligaments being hurt.

From the cervix fcapul# the third procefs is produ-
ced. The foie-part of this is formed into a glenoid ca-
vity (/), which is of the fhape of the longitudinal flec-
tion of an egg, being broad below, and narrow a-
bove. — Between the brims of this hollow and the
fore-part of the root of the fpine, a large finuofity is
left for the tranflmiffion of the fupra and infra -/pi anti
muffles ; and on the upper-part of thefe brims we
may remark a fmooth furface, where the fecond head
of the biceps fexor cubiti has its origin. — The root of
the fupercilia is rough all round, for the firmer adhe-
fion of the capfular ligament of the articulation, and
of the cartilage which is placed on thefe biims, where
it is thick, but becomes very thin as it is continued
towards the middle of the cavity, which it lines all
over.

The medullary veflels enter the fcapula near the
bafe of the fpine.

The fubftance of the fcapula , as in all other broad
flat bones, is cellular, but ot an unequal thicknefs ;
for the neck and third procefs are thick and llrong.
The inferior cojla , fpine, and coracoid procefs, arc
of a middle thicknefs ; and the body is fo prefixed by
the mufcles, as to become thin and diaphanous.

The fcapula and clavicle are joined by plain fur-
faces, tipped with cartilage (»j) : by which neither
bone is allowed any confiderable motion, being tight-
ly tied down by the common capfular ligament, and
by a very rtrong one which proceeds from the cora-
coid procefs ; but divides into two before it is fixed
into the clavicle , with fuch a direction, as either can
allow this bone to have a fmall rotation, in which its
pofterior edge turns more backwards, while the an-
terior one rifes farther forwards •, or it can yield to

the

(/) CI/J.OXOTV Xlf.

{m) Acromion, xeiTtcxto if, claulurat,

1 8 z Of thf SKELETON.

the fore-part of the fcapula moving downwards, while
the back-part of it is drawn upwards ; in both which
cafes, the oblong fmooth articulated furfaccs of the
clavicle and fcapula are not in the fame plane, but
Hand a little tranfverfely, or acrofs each other, and
thereby prefer ve this joint from luxations, to which it
would be fubjeft, if either of the bones was to move
on the other perpendicularly up and down, without

any rotation. Sometimes a moveable ligamentous

cartilage is found in this joint; otherwhilcs, fuch a
cartilage is only interpofed at the anterior half of it;
and in fome old fubjetls I have found a fefamoid
bone here (//). — The fcapula is connected to the head,
cs hyoides , vertebra , ribs, and arm-bone, by mufcles,
that have one end fattened to thefe bones, and the o-
ther to the fcapula, which can move it upwards, down-
wards, backwards, or forwards ; by the quick fuc-
ceflion of thefe motions, its whole body is carried in
a circle. But being alfo often moved as upon an axis
perpendicular to its plane, its circumference turns in
a circle whofe centre this axis is ( o ). Whichever of
thefe motions it performs, it always carries the outer
end of the clavicle and the arm along with it. — The
glenoid cavity of this bone receives the os humeri ,
which plays in it as a ball in a focket, as will be ex-
plained more hereafter.

The ufe of the fcapula is, to ferve as a fulcrum to
ihe arm ; and, by altering its pofition on different
occafions, to allow always the head of the os humeri
a right fituated focket to move in ; and thereby to a f-
fift and to enlarge greatly the motions of th t fuperior
extremity , and to afford the mufcles which rife from
it more advantageous adtions, by altering their direc-
tions to the bone which they are to move.- This

bone alfo ferves to defend the back-part of the tho-
rax, and is often employed to fuftain weights, or to
refill forces, too great for the arm to bear.

The

(«) Jac. Sylv. Ilagog. anat. lib. I. cap. 2.

(#) See Winflow Mcmoires dc l’acad. des fciences, 1726.

Of the SKELETON. 183

The bafe, acromion , coracoid procefs, and head of
the fcapu/a, are all in a cartilaginous (late at birth ;
and the three firfi are joined as epiphyfes ; while the
head, with the glenoid cavity, is not formed into a
diltinft feparate bone, but is gradually produced by
the olTification of the body of this bone being conti-
nued forwards.

The ARM has only one bone, bell known by the
Latin name of os humeri {p) ; which is long, round,
and nearly flraight.

The upper end of this bone ( q ) is formed into a
large round fmooth head, whofe middle point is not
in a flraight line with the axis of the bone, but Hands

obliquely backwards from it. The extent of the

head is difiinguifhed by a circular foffa furrounding
its bafe, where the head is united to the bone, and

the capfular ligament of the joint is fixed. Below

the fore-part of its bafe two tubercles Hand out : The
fmallelt one, which is fituated molt to the kilide, haa
the tendon of the fubfcapularis mufcle inferted into it*
—The larger more external protuberance is divided,
at its upper part, into three fmooth plain l'urfaces ;
into the anterior of which the mufculus fupra-fpinatus :
into the middle or largefl, the infra-fpinatus ; inta
the one behind, the teres minor is inferted. — Between
thefe two tubercles, exndlly in the fore-part of the
bone, a deep long fojfti is formed, for lodging the
tendinous head ol the biceps Jlexor cubiti ; which, af-
ter palling, in a manner peculiar to itlfclf, through
the cavity of the articulation, is tied down by a ten-
dinous fiieath extended acrofs the fojja ; in which, and
in the neighbouring tubercles, are feveral remarkable
holes, which are penetrated by the tendinous and li-
gamentous fibres, and by veliels. — On each fide of
this fo/fr, as it defeends in the os humeri , a rough
ridge, gently flatted in the middle, runs from the
roots of the tubercles. — The tendon of the peEloral

0^2 mufcle

( p ) AxptMti, axtvit, os brachii, artr.i, adjutcrium, parrum bracL;.;-c,
eanna brachii.

(7) Acrocolium.

i S4

Of the SKELETON.

mufcle is fixed into the anterior of thefe ridges, and
the latijfimus dorfi , and teres majqr\ are inferted into
the inteinal one. — A little behind the lower end of
this lad, another rough ridge may be obferved, where
the coraco-brachialis is inferted. — From the back-part
of the root of the larged tubercle a ridge alfo is con-
tinued, from which the -brevis extenfor cubiti riles.—
This bone is flatted on the infide, about its middle,
by the belly of the biceps flexor cubiti. — In the middle
of this plain furface, the entry of the medullary artery
is feen flanting obliquely downwards. — At the fore-
fide of this plane the bone rifes in a fort of ridge, which
is rough, and often has a great many fmall holes in
it, where the tendon of the llrong deltoid mufcle is
inferted ; on each fide of which the bone is frnooth
and fiat, where the brachioeus interfiles rifes. The ex-
terior of thefe two flat furfaces is the larged ; behind
it a fuperficial fpiral channel, formed by the inufcular
nerve, and the veflels that accompany it, runs from
behind forwards and downwards.-— The body of the
os humeri is flatted behind by the extenfors of the
fore-arm. — Near the lower end of this bone, a large
lltarp ridge is extended on its outfide, from which
the mufculus fpinatcr radii longus, and the longed head
of the extenfor carpi radialis rife. — Oppofite to this,
there is another fmall ridge to which the aponeurotic
tendon, that gives origin to the fibres of the internal
and external brachioei mufcles is fixed ; and from a
little depredion on the fore-fide of it, the pronator
radii teres rifes.

The body of the os humeri becomes gradually
broader towards the lower end, where it has feveral
procefi'es 5 at the roots of which there is a cavity be-
fore, and another behind (r). The anterior is divid-
ed by a ridge into two; the external, which is the
lead, receives the end of the radius ; and the internal
receives the coronoid procefsot the ulna in the fledlions
of the foie-arm, while the poderior deep triangular
cavity lodges the olecranon in the extenfions of that

member.

* (r) prffiitui.

Of

the SKELETON.

member. The bone betwixt thefe two cavities is-

nrefled fo thin by the procefles of the ulna, as to ap-
pear diaphanous in Several fubjefts — 1 he Tides of tie
pofterioi cavity are ftretched out into two procefles,.
one on each fide: Thefe are called condyles ; from
each of which a ftrong ligament goes out to the
bones of the forearm.— The externa condyle, which
has an oblique diredion alfo forwards in refpeft of
the internal, when the arm is in the molt natural
pofture {s)y is equally ' broad, and has an obtufe
fmooth head rifing from it forwards — —From the
rough part of the condyle, the inferior head of the bi-
corn'is , the extenjor digitorutn communis, extcnjor carpi
ulnar is, anconeus, and feme part of th tc fupinator radtv
brevis take their rife; and on the fmooth head the
upper end of the radius plays.— Immediately on the
outfide of this, there is a finuofity made by the
fhorter head of the bicornis mufcle, upon which the

mufcular nerve is placed. The internal condyle is

more pointed and protuberant than the external, to
give origin to fome part of the flexor carpi radiahs ,
pronator radii teres, palmaris longus, flexor digitorutn
fublimis. , and flexor carpi ulnaris. Between the two
condyles, is the trochlea or pully, which con fills or
two lateral protuberances, and a middle cavity, that
are fmooth and covered with cartilage.— When the.
fore-arm is extended, the tendon of the internal bra -
ehiocus mufcle is lodged in the fore-part of the cavity
of this pully. — The external protuberance, which is
lefs than the other, has a fliarp edge behind; but
forwards, this edge is obtufe, and only lepaiated
from the little head, already deferibed, by a lmall
fo/Ta, in which the joined edges of the ulna and radius
move. — The internal protuberance of the pully is.
]ar<Teft and higheft; and therefore in the motions of
the ulna upon it, that bone would be inclined cut-
wards, was it not fupported by the radius on that,
fide —Between this internal protuberance and condyle *

Qjj a finuofity

£) winflow Mcmoires de l’acad. dcs fciences, 1711..

1 85 Of the SKELETON.

a finuofity may be remarked, where the ulnar nerve
paffes.

The fubftance and the internal flrutture of the or
humeri is the fame, and difpofed in the fame way, as
in other long bones.

The round head at the upper end of this bone is
articulated with the glenoid cavity of the fcapula\
which being fuperficial, and having long ligaments,
allows the arm a free and extenfivc motion. — Thefe
ligaments are however confiderably flrong. For, be-
fides the common capfular one, the tendons of the
mufclcs perform the office, and have been defcribed

under the name of ligaments. Then the acromion

and coracoid procefs, with the flrong broad ligaments
flretched betwixt them, fecure the articulation above,
where the greateil and moft frequent force is applied
to thrufl the head of the bone out of its place. It is
true that there is not near fo flrong a defence at the
lower part of the articulation ; but in the ordinary
nollures of the arm, that is, fo long as it is at an a-
cute angle with the trunk of the body, there cannot
be any force applied at this place to occafion a luxa-
tion, fince the joint is protected fo well above.

The motions which the arm enjoys by this articu-
lation, are to every fide ; and by the fucceffion of
thefe different motions, a circle may be defcribed. —
Befides which, the bone performs a fmall rotation
round its own axis. But though this can be per-
formed with the round head in all pofitions ; yet as
thefe vary, the effects upon the body of the bone are
very different : For, if the middle of the head is the
centre of rotation, as it is when the arm hangs down
by the fide, the body of the bone is only moved for-
wards and backwards; becaufe the axis of motion of
the head is nearly at right angles with the length of
the bone (/) ; whereas, when the arm is raifed to
right angles with the trunk of the body, the centre
of motion, and the axis of the bone, come to be in
the fame flraight line ; and therefore the body of the

os

(t) Hippocrat. dc articul § i.

Of the SKELETON. 187

os humeri performs the fame motion with its head. —
Though the motions of the arm feem to be very ex-
tenfive, yet the larger {bare of them depends on the
motion of the [cupula. — The lower end of the os hu -
inert is articulated with the bones of the fore-arm*
and carries them with it in all its motions, but ferves
as a bafe on which they perfoim the motions peculiar
to themfelves; as (hall be defcribed afterwards.

Both the ends of this bone are cartilaginous in a
new-born infant, and the large head with the two
tubercles, and the trochlea with the two condyles , be-
come epiphyfes before they are united to the body of
the bone.

The FORE- ARM (u) confifls of two long bones,
the ulna and radius ; whofe fituation, in refpe£l of
each other, is oblique in the leaf! {training or mofl
natural pofture ; that is, the ulna is not dire&ly be-
hind, nor on the outfide of the radius , but in a mid-
dle fituation between thefe two, and the radius crofles
it. — The fituation however of thefe two bones, and
of all the other bones of the fuperior extremity that are
not yet defcribed, is frequently altered ; and there-
fore, to {bun repetitions, I defire it may be now re-
marked, that, in the remaining account of the fupe-
rior extremity , I underhand by the term of poJleriort
that part which is in the fame direction with the
back of the hand ; by anterior, that anfwering to the
palm; by internal , that on the fame fide with the
thumb ; by external, the fide neareft/o the little fin-
ger ; fuppofing the hand always to be in a middle
pofition between pronation and fupi nation.

ULNA (a), fo named from its being ufed as a mea-
fure, is the longefl of the two bones of the fore-arm,
and fituated on the outfide of the radius.

At the upper end of the ulna are two procefles. — >
The polterior is the largeft, and formed like a hook,
whofe concave furface moves upon the pully of the

es

(a) Cubitus, sxun, rvym, ulna, lacertus.

W Cnbitus, m-h^uc, xporn^ay, focile majus, canna vel arundo
major, ct inferior brachii.

1 8 8

Op the SKELETON.

\

os humeri , and is called olecranon (b), or top of tha
cubit. — The convex back-part of it is rough and fca-
brous, where the long us, brevis, and brachioeus exter - .
nus, are inferted. The olecranon makes it unneceflary
that the tendons of the extenfor muCcles (hould pafs
over the end of the os humeri ; which would have
been of ill confequence in the great fle&ions of this
joint, or when any confiderable external force is
applied to this part ( c ). — The anterior procefs is not
fo large, nor does it reach fo high as the one behind ;
but is (harper at its end, and therefore is named coro -
noid. — Between thefe two procefies, a large femicircu*
lar or Jigmoid concavity is left ; the furface of which,
on each fide of a middle rifing, is flanting, and ex-
a£Uy adapted to the pully of the bone of the arm. —
Acrofs the middle of it, there is a fmall finuofity for
lodging mucilaginous glands ; where, as well as in a
fmall hollow on the internal fide of it, the cartilage
that lines the reft of its furface is wanting. — Round
the brims of this concavity the bone is rough, where
the capfular ligament of the joint is implanted. — Im-
mediately below the olecranon, on the back-part of
the ulna, a fiat triangular fpongy furface appears, on
which we commonly lean. — At the internal fide of
this, there is a larger hollow furface, where the muf-
culus anconasus is lodged ; and the ridge at the infide
of this gives rife to the mufculus fupinator radii brevis.

, Between the top of the ridge and the coronoid pro-

cefs is the femilunated fmooth cavity, lined with car-
tilage, in which, and a ligament extended from the
one to the other end of this cavity, the round head
of the radius plays. — Immediately below it a rough
hollow gives lodging to mucilaginous glands. — Below
the root of the coronoid procefs, this bone is fcabrous
and unequal, where the brachiceus interims is inferted.

On the outfide of that we obferve a fmooth conca-
vity, where the beginning of the Jlexor digitorum pro-
fundus fprouts out.

The-

(b) Ayxwv, gibber cubitus, additamcntum necatum.

(c) Window F.xpofition anatomique du corps humain, tvaitc des.
tfs fees, feft. 279/

Of the SKELETON.

i 89

The body of the ulna is triangular. — The internal
angle is very fharp where the ligament that conne&s
the two bones is fixed : — The fides, which make this
angle, are flat and rough, by the adhion and adhefion
of the many mufcles which are fituated here. — At
the diflance of one third of the length of the ulna
from the top, in its fore-part, the paflage of the me-
dullary veflcls is to he remarked flanting upwards. —
The external fide of this bone is fmooth, fomewhat
convex, and the angles at each edge of it are blunted
by the prefi'ure of the mufcles equally difpofed about
them.

As this bone defcends, it becomes gradually fmal-
ler ; fo that its lower end terminates in a little head,
ftanding on a fmall neck. — Towards the fore but outer
part of which laft, an oblique ridge runs, that gives
rife to the pronator radii quadratus. — The head is
round, fmooth, and covered with a cartilage on its
internal fide, to be received into the femilunar cavity
of the radius ; while a Jlyloid procefs (d) rifes from its
outfide, to which is fixed a ftrong ligament that is
extended to the os cuntiforme and pififorme of the wrifl.
— Between the back-part of that internal fmooth fide
and this procefs, a finuofity is left for the tendon of
the extenfor carpi ulnaris. — On the fore-part of the
root of the procefs, fuch another depreffion may be
remarked for the paflage of the ulnar artery and nerve.
-—The end of the bone is fmooth, and covered with
a cartilage. — Between it and the bones of the wrift,
a doubly concave moveable cartilage is interpofed ;
which is a continuation of the cartilage that covers
the lower end of the radius , and is connedfed loofely
to the root of the Jlyloid procefs, and to the rough
cavity there ; in which mucilaginous glands are
lodged.

The ulna is articulated above with the lower end of
the os humeri , where thefe bones have depreflions and
protuberances correfponding to each other, fo as to
allow an eafy and fecure extenfion of the fore-arm to

almolt

(<0 TpufottSn, malleolus externus.

5po Of the SKELETON.

nlmoft a ftraight line with the arm, and fle&ion to a
very acute angle ; but, by the flaming pofition of the
pully, the lower part of the fore-arm is turned out-
wards in the extenfion, and inwards in the ile&ion
(e) ; and a very fmall kind of rotation is likevvife al-
lowed in all pofitions, efpecially when the liga-
ments are mod relaxed by the fore-arm being in a
middle degree of fle£Hon. — The ulna is alfo articu-
lated with the radius and carpus , in a manner to be
related afterwards.

RADIUS (f ), fo called from its imagined refem-
blance to a fpoke of a wheel, or to a weaver’s beam,
is the bone placed at the infide of the fore-arm. Its
upper end is formed into a circular little head, which
is hollowed for an articulation with the tubercle at the
fide of the pully of the os humeri ; and the half of
the round circumference of the head next to the ul-
na is fmooth, and covered with a cartilage, in order
to be received into the femilunated cavity of that
bone. — Below the head, the radius is much fmaller j
therefore this part is named its cervix, which is made
round by the action of the fupinator radii brevis. — At
the external root of this neck, a tuberous procefs
rifes ; into the outer part of which the biceps flexor
cubit i is inferted. — From this a ridge runs downwards
and inwards, where the fupinator radii brevis is in-
ferted ; and a little below, and behind this ridge,
there is a rough fcabrous furface, where the pronator
radii teres is, fixed.

The body of the radius is not ftraight, but convex
on its internal and pofterior furfaces ; where it is alfo
made round by the equal preflure of the circumjacent
mufcles, particularly of the extenfors of the thumb ;
but the furfaces next to the ulna are flatted and rough,
for the origin of the mufcles of the hand ; and both
terminate in a common fharp fpine, to which the
ftrong ligament extended betwixt the two bones of
the fore-arm is fixed. — A little below the beginning

& .

(e) Winflow, Memoircs tie I'acad. des fciences, 1722.

(f) facile minus, can 11 a minor, amndo minor.

Of the SKELETON.

ipr

of the plain furface, on its fore-part, where the flexor
mufcle of the laft joint of the thumb takes its origin,
the palfage of the medullary ve/Tels is feen flanting
upwards. — The radius becomes broader and flatter to-
wards the lower end, efpecially on its fore-part, where
its pronator quadratic mufcle is fituated.

The lower end of the radius is larger than the fu-
perior ; though not in fuch a difproportion as the up-
per end of the ulna is larger than its lower end. — Its
back-part has a flat ftrong ridge in the middle, and
foflx on each fide. — In a fmall groove immediately on
the outfide of the ridge, the tendon of the exttnfor
tertii internodii pollicis plays. — In a large one beyond
this, the tendons of the indicator and of the common
extenfor mufclcs of the fingers pafs. — Contiguous to
the ulna , there is a fmall depreflion made by the ex-
tenfor minimi digiti — On the infide of the ridge there
is a broad depreflion, which feems again fubdivided,
where the two tendons of the bicornis , or extenfor car-
pi radialis, are lodged. — The internal fide of this end
of the radius is alio hollowed by the extenfors of the
firft and fecond joint of the thumb; immediately a-
bove which, a little rough furface fhews where the
fupinator radii longus is inferted. — The ridges at the
tides of the grooves, in which the tendons play, have
an annular ligament fixed to them, by which the fe-
veral fheaths for the tendons are formed. — The fore-
part of this end of the radius is alio deprelfed, where
the flexors of the fingers and flexor carpi radialis pafs.

I he external fide is formed into a femilunated
fmooth cavity, lined with a cartilage, for receiving
the lower end of the ulna. — The loweft part of the
radius is formed into an oblong cavity ; in the middle
of which is a fmall tranfverfe riling, gently hollowed,
for lodging mucilaginous glands; while the riling it-
felf is inlinuatcd into the conjunction of the two
bones of the wrift that are received into the cavity.

1 he internal fide of this articulation is fenced by
|a remarkable procefs (g) of the radiusi from which a

ligament

Cf) Malleolus interims, procefius ftyloides,

IQ2

Of the SKELETON.

ligament goes out to the wrift, as the Jlyloid procefs
of the ulna with its ligament guards it on the out-
fide.

The ends of both the bones of the fore-arm being
thicker than the middle, there is a confiderable dif-
tance between the bodies of thefe bones ; in the lar-
ger part of which a ftrong tendinous, but thin liga-
ment, is extended, to give a large enough furface for
the origin of the numerous fibres of the mufcles fi-
tuated here, that are fo much funk between the bones,
as to be protected from injuries, which they would
otherwife be expofed to. But this ligament is want-
ing near the upper end of the fore-arm, where the
fupinator radii brevis , and Jlexor digitorum profundus ,
are immediately connected (A).

Both ends of the bones of the fore-arm are firft
cartilages, and then cpiphyfes in children.

As the head of the radius receives the tubercle of the
os humeri , it is not only bended and extended along
with the ulniiy but may be moved round its axis in
any pofition •, and that this motion round its axis may
be fufficiently large, the ligament of the articulation
is extended farther down than ordinary on the neck
of this bone, before it is conne£ted to it ; and it is
very thin at its upper and lower part, but makes a
firm ring in the middle. — This bone is alfo joined to
the ulna by a double articulation ; for above, a tu-
bercle of the radius plays in a focket of the ulna ;
whilft below, the radius gives the focket, and the ul-
na the tubercle : But then the motion performed in
thefe two is very different ; for at the upper end,
the radius does no more than turn round its axis ;
while at the lower end, it moves in a foit of cycloid
upon the round part of the ulna ; and as the hand is
articulated and firmly connected here with the radius ,
they mult move together. — When the palm is turned
uppermolt, the radius is faid to perform the fupination ;
when the back of the hand is above, it is faid to be
prone. But then the quicknefs and large extent of

thefe

(A) Weitbrecht, Sjrndcfmolog. %. 10, 12.

Or the SKELETON.

*93

thefe two motions are affifted by the ulna, which, as
was before obferved, can move with a kind of fmall
-rotation on the doping fides of the pulley. This la-
teral motion, though very inconfiderable in the joint
itfrlf, is confpicuous at the lower end of fuch a long
bone; and the ftrong ligament connecting this lower
end to the carpus , makes the hand more readily to
obey tbefe motions.— When we defign a large circu-
lar turn of our hand, we increafe it by the rotation
of the or htmeri , and fometimes employ the fpine and
inferior extremities to make thefe morions of probation
or fupination of the hand large enough.

The HAND (i) comprehends all from the joint of
the wrift to the points of the fingers. Its back-part
is convex, for greater firmnefs and ftrength ; and it
is concave before, for containing more furely and con-
veniently fuch bodies as we take hold of.— One half
of the hand has an obfcure motion in eomparifon of
whijt the other has, and fetves as a bafe to the move-
able half; which can be extended back very little far-
ther than to a ftraight line with the fore-arm, but can
be conhderably pended forwards.

As the bones that compofe the hand are of diffe-
rent ihapes and ufes, while feveral of them that arc
contiguous agree in fome general charters; the
hand is, on this account, commonly divided into the

among "hkh “

The CORPUS (A) is compofed of eight fmall fpon-

gy bones, fituated at the upper part of the hand. I

fhall defer 1 be each of thefe bones, under a proper
name taken from their figure (/) ; becaufe the nfethod
of ranging them by numbers leaves anatomifts too
much at liberty to debate very idly, which ought to
be preferred to the firft number ; or, which is worfe
fe^ral, without explaining the order they obferve*
differently apply the fame numbers, and fo confound
«htir readere'-But ** the cteferiprion oithefc bones

(i) ’Axpo^ti f, fumma manus.

i fbThialc> Pj.™3 PaIm* par?, rafetta.
w cjicr, Cult. anat. lib. cap. 3,

i^4 Of the SKELETON.

niay be in the fame order as they are found in the ge-
nerality of anatomical books, I fhall begin with the
range of bones that are concerned in the moveable
joint of the wrift, or are conne&ed to the fore-arm,
and fhall afterwards confider the four that fupport the
thumb and offa metacarpi of the fingers.

The eight bones of the carpus are, os fcaphoides^ lu~
tiare, cuneiforme , pijtforme , trapezium , trapezoides , mag-
num, unciforme.

The fcaphoides is fituated mod internally of thofe
rhat are articulated with the fore-arm. — The lunare
is immediately on the outfide of the former. — The
cuneiforme is placed fiill more externally, but does not
reach fo high up as the other two — The pi/iforme
Hands forwards into the palm from the cuneiforme. — ■
The trapezium is the firft of the fecond row, and is
fituated betwixt the fcaphoides and firft joint of the
thumb. — The trapezoides is immediately on the out-
fide of the trapezium. — The cs magnum is ftill more
external. — The unciforme is farther to the fide of the
little finger.

Os fcaphoides (»«) is the largeft of the eight except
one. It is convex above, concave and oblong below j
from which fmall rcfemblance of a boat it has got its
name. — Its fmooth convex furface is divided by a
rough middle foffa , which runs obliquely crofs it. —
The upper largeft divifion is articulated with the ra-
dius.— Into the foffa the common ligament of the joint
of the wrift is fixed ; and the lower divifion is joined
to the trapezium and trapezoides. — The concavity re-
ceives more than an half of the round head of the
cs magnum. — The external fide of this hollow is form-
ed into a femilunar plane, to be articulated with the
following bone. — The internal, pofterior, and ante-
rior edges are rough, for fixing the ligaments that
connect it to the furrounding bones.

Os lunare («) has a fmooth convex upper furface,
by which it is articulated with the radius* — The inter-
nal

(m) K omxojiJuf, navicular*.
(«) Lunatum,

Of the SKELETON. 19$

rial fide, which gives the name to the bone, is in the
form of a crefcent, and is joine,d with the fcaphcid ; —
the lower furface is hollow, for receiving part of the
head of the os magnum. — On the outfide of this cavi-
ty is another fmooth, but narrow oblong finuofity,
for receiving the upper end of the os unciforme : —
On the outfide of which a fmall round convexity is
found, for its connection with the os cuneiforme. —
Between the great convexity above, and the firft deep
inferior cavity, there is a rough fojfla, in which the
circular ligament of the joint of the wrift is fixed.

Os cuhetforme ( p ) is broader above, and towards the
back of the hand, than it is below and forwards ;
which gives it the refemblance of a wedge. — The fu-
perior (lightly convex furface is included in the joint
of the wrift, being oppofed to the lower end of the
ulna. — Below this the cuneiform bone hae a rough
foffht wherein the ligament of the articulation of the
wrift is fixed. — On the internal fide of this bone,
where it is contiguous to the os lunare , it is fmooth and
flightly concave. — Its lower furface, where it is con-
tiguous to the os unciforme is oblong, fomewhat fpiral,
and concave. — Near the middle of its anterior furface
a circular plane appears, where the os pijforme is fuf-
tained.

Os pijforme ( q ) is ^lmoft fpherical, except one cir-
cular plane, or flightly hollow furface, which is co-
vered with cartilage for its motion on the cuneiform
bone, from which its whole rough body is prominent
forwards into the palm ; having the tendon of the
flexor carpi ulnaris , and a ligament from the flyloid
procefs of the ulna, fixed to its upper part ; the tranj~
verfe ligament of the wrift is connected to its inter-
nal fide-, ligaments extended to the unciform bone,
and to the os metacarpi of the little finger, are attach-
ed to its lower part; the abduftor minimi digiti has its
origin from its fore-part ; and, at the internal fide of

h“ 1 R 2 it,

(t>) Triquetrum.

Cartilaginoi'um, fubrotunclum, refbun.

*9 6 Of the SKELETON.

it, a Email deprcflion is formed, for the paflagc of
the ulnar nerve.

Trapezium ( r ) has four unequal fides and angles in,
its hack-part, from which it has got its name. — A-
bove, its furface is fmooth, flightly hollowed, and
felnicircular, for its conjun&ion with the os fcapkoidcs.
— Its external fide is an oblong concave fquare, for

receiving the following bone. The inferior furface

is formed into a pulley ; the two protuberant fides of
which are external and internal. Ou this pulley the
firfi: bone of the thumb is moved. — At the external
fide of the external protuberance, a fmall oblong
fmooth furface is formed by the os metacarpi indicis. — ■
The fore-part of the trapezium is prominent in the
palm, and, near to the external fide, has a finuofity
in it, where the tendon of the flexor carpi radialis is
lodged; on the ligamentous fheath of which the ten-
don of the jlexor tertii inter ned'u pollicis plays : And
Hill more externally the bone is fcabrous, where the
Iranfverfe ligament of the wrifi; is connected, the ab -
duBor and flexor primi internodii pollicis have their o-
rigin, and ligaments go out to the fuft. bone of the
thumb.

Os trapezoidcs (r), fo called from the irregular
quadrangular figure of its back-part, is the fmalleft
bone of the wrift except the piflforme. — The figure of
it is an irregular cube. — It has a fmall hollow furface
above, by which it joins the fcapboides\ a long con-
vex one internally, where it is contiguous to the tra-
pezium ; a fmall external one, for its conjun£tion with
the os magnum ; and an inferior convex furface, the
edges of which are however fo raifed before and be-
hind, that a fort of pulley is formed, where it fuftains
the os metacarpi indicis.

Os magnum (t), fo called becaufe it is the largeft
bone of the carpus , is oblong, having four quadran-
gular fides, with a round upper end, and a triangular

plain

(r) Os cubiforme, trapezoides, multangulum majus.
(j) Trapezium, mulunguiutn minus.

( t ) Maximum, capitatum.

Of the SKELETON 197

plain one below. — —The round head is divided by a
fmall rifing, oppofite to the connexion of the os
fcaphoides and lunare, which together form the cavity
for receiving it. — On the infide a fhort plain furface
joins the os magnum to the trapezoides. — -On the cut-
fide is a long narrow concave furface, where it is
contiguous to the os uncifarme. — 'The lower end, which
fuflains the metacarpal bone of the middle finger, is
triangular, flightly hollowed, and farther advanced
on the internal fide than on the external, having a
confiderable oblong depreflion made on the advanced
infide by the metacarpal bone of the fore-finger; and
generally there is a fmall mark of the os nietacarpi di~
gift annularis on its external fide.

Os unciformc '(«) has got its name from a thin broad
procefs that (lands out from it forwards into the palm,
and is hollow on its infide, for affording paflfage to
the tendons of the flexors of the fingers. To this-
procefs alfo the tranfverfe ligament is fixed, that binds
down and defends thefe tendons ; and the plexor and
abduttor mufcles of the little finger have part of their

origin from it. The tipper plain furface is fmall,.

convex, and joined with the os lunare : — The internal
fide is long, and flightly convex, adapted to the con-
tiguous os magnum : — The external furface is oblique,,
and irregularly convex, to be articulated with the cu-
neiform bone : — -The lower end is divided into two
concave furfaces ; the external is joined with the me-
tacarpal bone of the little finger, and the internal,
one is fitted to the metacarpal bone of the ring-
finger.

In the defer iption of the preceding eight bones, I
have only mentioned thofe plain furfaces covered with
cartilage, by which they are articulated to each other,,
or to fome other bones, except in fome few cafes,,
where fomething extraordinary was to be obferved
and I have defignedly omitted the other rough fur-
faces, led, by crowding too many words in the de-
feription. of fuch fmall bones, the whole fhould be
* r R 3 unintelligibly a

09 Cuneiforms.

Of the SKELETON.'

unintelligible : But thefe fcabrous parts of the bones
may eafily be underftood, after mentioning their fi-
gure, if it is obferved, that thev are generally found
only towards the back or palm of the hand ; that they
are all plain, larger behind than before ; and that they
receive the different ligaments, by which they are ei-
ther conne&ed to neighbouring bones, or to one an-
other; for thefe ligaments cover all the bones, and
are l'o accurately applied to them, that, -at firft view,
the whole carpus of a recent fubjebl appears one
fmooth bone (a.*).

As the furfaces of thefe bones are largefi: behind,
the figure o£ the whole conjoined mult be convex
there, and concave before ; which concavity is Bill
more increafed by the os piffenne. and procefs of the
cs vrteijorme, Banding forwards on one fide, as the
trapezium does on the other : And the bones are fe-
curelv kept in this form, by the broad- Itrong tranf-
verle ligament connebled to thefe parts of them that
Hand prominent into the palm of the hand. — The
convexity behind renders the whole fabric ftrong-
cr, where it is moft expofed to injuries; and the large
anterior hollow is neceffary for a fafe palfage to the
numerous velfels, nerves, and tendons of the fingers.

The fubftance of thefe bones is fpongy and cellu-
lar, but firong in refpebl of their bulk.

The three full bones of the carpus make an oblong
head, by which they are articulated with the cavity
at the lower ends of the bones of the fore-arm; fo
as to allow motion to all fides, and, by a quick fuc-
ceflion of thefe motions, they may be moved in a
circle. But as the joint is oblong, and therefore the
two dimenfions are unequal, no motion is allowed
to the carpus round its axis, except what it has in the

pronation and fupination along with the radius.

The articulation of the firit three bones of the fupe-
rior row, with the bones of the inferior, is luch as
allows of motion, efpecially backwards and forwards;

to

( x ) Galen tie ufu part. lib. 2. cap. 8. For a particular deferiptioa
of thefe ligaments, fee Wcitbrecht Syntjcfinolog. p. $ W.

s Of the S K E L E f O N.

to the fecurity and eafinefs of which the reception of
the os magnum into the cavity formed by the fcaphoides
and lunare contributes confiderably : And the greateft
number of the mufcles that ferve for the motion of
the wrift on the radius , being inferted beyond the
conjunction of the firft row of bones with the fecond,
act equally on this articulation as they do on the for-
mer; but the joint formed with the radius being the
molt eafly moved, the firft effeCt of thefe mufcles is
on it; and the fecond row of the carpus is only mov-
ed afterwards. By this means a larger motion of the
wrift is allowed, than otherwife it could have had
fafely : For, if as large motion had been given to one-
joint, the angle of fleclion would, have been very
acute, and the ligaments muft have been longer than-
was confident with the firmnefs and fecurity of the
joint. — lhe other articulations of the bones here be-
ing by nearly plain furface9, fcarce allow of any
more motion, becaufe of the ftrong connecting liga-
ments, than to yield a little, and fo elude the force
ol any external power; and to render the back of the
wrift a little more flat, or the palm more hollow, on
pfoper occafions. The articulations of the thumb
and metacarpal bones (hall be examined afterwards.

The ufes of the carpus are to ferve as a bafe to the
hand, to proteCl its tendons, and to afford it a free
large motion.

All the bones of the carpus are in a cartilaginous
ftate at the time of birth.

On account of the many tendons that pafs upon
the lower end of the fore-arm and the carpus , and
of the numerous ligaments of thefe tendons and of
the bones, which have lubricating liquors fupplied to
them, the pain of fprains here is acute, the parts
take long time to recover their tone, and their fwell-
ings are very obftinate.

METACARPUS ( x ) confifts of four bones which
luftain the fingers. — Each bone is long and round,

with

(x) Knif, rptxafrricv, srxSof, xrcrrov, poflbrachiale, pcc^

tns, f alma, pcftea,

soa

Of the SKELETON.

with its ends larger than its body. — The upper end;,
which fome call the bafe, is flat and oblong, without
any confiderable head or cavity ", but it is however
fomewhat hollowed, for the articulation with the
carpus : It is made flat and fmooth on the fides where
thefe bones are contiguous to each other Their bo-

dies are flatted on their back-part by the tendons of
the extenfors of the fingers. — The anterior furface
of thefe bodies is a little concave, efpecially in their
middle ; along which a (harp ridge (lands out, which
feparates the mufeuli interoffti placed on each fide of
thefe bones which, are there made flat and plain by
thefe mufcles.

Their lower ends are railed into large oblong
fmooth heads, whofe greatefl extent is forwards from
the axis of the bone. — At the fore-part of each fide
of the root of each of thefe heads, one or two tu-
bercles Hand out, for fixing the ligaments that go
from one metacarpal bone to another, to- preferve
them from being drawn afundcr. — Round the heads
a rough ring may be remarked, for the capfular liga-
ments of the fir ft joints of the fingers to be fixed to ;
and both fides of thefe heads are flat, by preffing on
each other.

The fubftance of the metacarpal bones is the fame
with that of all long bones.

At the time of birth, thefe bones are cartilaginous
at both ends, which afterwards become epiphyfes.

The metacarpal bones are joined above to the ojfa
carpi and to each other by nearly plain furfaces.
Thefe connexions are not fit for large motions. —
The articulation of their round heads at the lower
ends with the cavities of thefirft bones of the fingers,
is to be taken notice of hereafter.

The concavity on the fore-part of thefe metacar-
pal bones, and the placing their bafes on the arched
carpus , caufe them to form a hollow in the palm of
the hand, which is ufeful often to U9. — The fpaces*
between them lodge mufcles, and their fmall motion
makes them fit fupporters for the fingers to play on..

Though,

201

Of the SKELETON.

Though the offd metacarpi fo far agree, yet they
may be diftinguifhed from each other by the follow-
ing marks.

The os metacarpi indicts is generally the longefi:.—
Its bafe, which is articulated with the os trapezoides ,
is hollow in the middle. — The fmall ridge on the in-
ternal fide of this oblong cavity is fmaller than the
one oppofite to it, and is made flat on the fide by the
trapezium. — The exterior ridge is alfo fmooth, and
flat on its outGde, for its conjunction with the os-
magnum ; immediately below which, a femicircular
fmooth flat furface fhews the articulation of this to
the fecond metacarpal bone. — The back-part of this
bafe is flatted, where the long head of the e> denjer
carpi radial'ts is inferted ; and its fore-part is promi-
nent, where the tendon of the flexor carpi radialts is
fixed. — The external fide of the body of this bone is
more hollowed by the aftion of mufcles, than the
internal. — The tubercle at the internal Foot of its
head is larger than the external. — Its bafe is fo firm-
ly fixed to the bone it is conne&ed with, that it has
Bo motion.

Os metacarpi medii digiti is generally tbe fecond in
length ; but often it is as long as the former ; fome-
times it is longer ; and frequently it appears only to
equal the fir ft by the os magnum being farther ad-
vanced downwards than any other bone of the
wrift. — Its bafe is a broad fuperficial cavity, flanting
outwards ; the internal pofterior angle of which is
fo prominent, as to have the appearance of a pro-
cefs. — The internal fide of this bafe is made plain
in the fame way as the external fide of the former
bone, while its external fide has two hollow' circular
furfaces, for joining the third metacarpal bone; and
between thele furfaces there is a rough fifla, for the
adhefian of a ligament, and lodging mucilaginous
glands. — The fhorter head of the bkornis is inferted
into the back-part of this bafe. — The two fides of
this bone are almofl: equally flatted ; only the ridge
on the fore-part of the bodv inclines outwards. — •

The

202 Of the SKELETON.

The tubercles at the fore-part of the root of the head
are equal. — The motion of this - bone is very little'
more than the fird metacarpal one has ; and there-
fore, thefe two firmly refill bodies preffed againll
them by the thumb, or fingers, or both.

Os metacarpi digiti annularis is (horter than the fe-
coud metacarpal bone. — Its bafe is femicircular and
convex, for its conjun&ion with the os unciforme. —
On its internal fide are two fmooth covexities, and a
middle fojfa , adapted to thefccond metacarpal bone. —
The external fide has a triangular fmooth concave
furface to join it with the fourth one. — The anterior
ridge of its body is fituated more to the out than to
the infide. — The tubercles near the head are equal. —
The motion of this third metacarpal bone is greater,
than the motion of the fecond.

Os metacarpi minimi digiti is the final left and (harp-
ed.— Its bafe is irregularly convex, and rifes flanting
outwards. — Its internal fide is exa£lly adapted to the
third metacarpal bone. — The external has no fmooth
furface, becaufe it is not contiguous to any other
bone ; but it is prominent where the extcnjor carpi
vlnaris is inferted. — As this metacarpal bone is fur-
nifhed with a proper moving mufcle, has the plained:
articulation, is mod loofely conne£led and lead con-
fined, it not only enjoys a much larger motion than,
any of the red, but draws the third bone with it,
when the palm of the hand is to be made hollow by
its advancement forwards, and by the prominence
of the thumb oppofite to it.

The THUMB and four FINGERS are each com-
pofed of three long bones.

The Thumb (y) is fituated obliquely in refpeft of
the fingers, neither oppofite dire&ly to them, nor in
the fame plane with them. — All its bones are much
thicker and dronger in proportion to their length,
than the bones of the fingers are : Which was ex-
tremely neccdary, fince the thumb counteratfls all
the fingers.

The

(yj Jr*. JvJ'uAof, maenus digitus, promanu*

Of TtiE S' K E L E T O. N. 203

. The firft bone of the thumb has its bafe adapted
•to the double pulley of the trapezium : For, in view-
ing it from one fide to the other, it appears convex
in the middle ; but when confidered from behind
forwards, it is concave there. — The edge at the fore;-
part of this bafe is produced farther than any other
part ; and round the back-part of the bafe a rough fa£a
.may be feen, for the connexion of the ligaments of
this joint. — The body and head of this bone are.pf
the fame fhape as the offa metacarpi ; only that 'the
body is fhorter, and the head flatter, with the tu-
bercles at the fore-part of its root larger. , , f

The articulation of the upper end of this bone is
uncommon: For, though it has protuberances afpd
depreffions adapted to the double pulley of the tra-
pezium ; yet it enjoys a circular motion, as the joints
do where a round head of one bone plays in the or-
bicular focket of another; only it is fomewhat more
confined and lefs expeditious, but ftronger and more
fecure, than fuch joints generally are.

This bone of children is in the fame Rate with the
metacarpal bones.

The fecond bone of the thumb has a large bafe
formed into an oblong cavity, whofe greateft length
is from one fide to the other. — Round it feveral tu-
bercles may be remarked, for the infertion of liga-
ments.— Its body is convex, or a half round behind ;
but flat before, for lodging the tendon of the long
.flexor of the thumb, which is tied down by liga-
mentous fheaths that are fixed on each fide to the an-
gle at the edge of this flat furface. — The lower end
of this fecond bone has two lateral round protube-
rances, and a middle cavity, whofe greateft extent of
fmooth furface is forwards.

The articulation and motion of the upper end of
this fecond bone is as Angular as that of the former. —
For its cavity being joined to the round head of the
firft bone, it would feem at firft view' to enjoy mo-
tion in all directions ; yet, becaufe of the Itrength
of its lateral ligaments, oblong figure of the joint it-

---V Tel f.

S04

Of the SKELETON.

lielf, and mobility of the firft joint, it only allows
fje&ion and extenfion ; and thefe aregenerally much
confined.

The third bone of the thumb is the fmalleft, with
a large bafe, whofe greateft extent is from one fide
to the other. — This bafe is formed into two cavities
and a middle protuberance, to be adapted to the pnl-
&yof the former bone. — Its body is rounded be-
hind j but is flatter than in the former bone, for fu-
ilaining the nail. — It is flat and rough before, by the
dnfertion of the flexor tertii internodii. — This bone
becomes gradually fmaller, till near the lower end,
where it is a little enlarged, and has an oval fcabrous
tS&ge.

The motion of this third bone is confined to flec-
tion and cxtenfion.

The orderly difpofition of the bones of the fl tigers
into three rows, has made them generally obtain the
name of three phalanges (2). — All of them have half
round convex furfaces, covered with an aponeuroflsy
formed by the tendons of the extenfcrsy latnbricales,
and interoffeiy and placed dire£Hy backwards, for their
greater ftrength ; and their flat concave part is for-
wards, for taking hold more furely, and for lodging
the tendons of the flexor mufcles. — The ligaments
for keeping down thefe tendons are fixed to the
angles that are between the convex and concave fides.

The bones of the firft phalanx {a) of the fingers
anfwcr to the defcription of the fecond bone of the
thumb : Only that the cavity in their bafe is not fo
oblong ; nor is their motion on the metacarpal bones
fo much confined : For they cart be moved laterally
or circularly, but have no rotation, ora very fmall de-
gree of it, round their axis.

Both the ends of this firft phalanx are in a cartila-
ginous ftate at the birth ; and the upper one is after-
wards affixed in form of an epiphyfe.

The

(?) Scytalidsc, Internodia, fcadcula, ngmina, acicr, condyli articuli.

(*) UfCKoySuMi,

Of the SKELETON-.

205

The fecond bone ( b ) of the fingers has its bafe
formed into two lateral cavities, and a middle protu-
berance ; while the lower end has two lateral protu-
berances and a middle cavity; therefore, it is joined
at both ends in the fame manner, which none of the
bones of the thumb are.

This bone is in the fame condition with the former
in children.

The third bone ( c ) differs nothing from the de-
fcription of the third bone of the thumb, excepting
in the general diftinguiftiing marks ; and therefore,
the fecond and third phalanx of the fingers enjoy on-
ly fle&ion and extenfion.

The upper end of this third phalanx is a cartilage
in a ripe chiid ; and is only an epiphfie after, till the
full growth of the body.

All the difference of the phalanges of the fevcral
fingers confifls in their magnitude. — The bones of the
middle finger (a) being the longelt and largeft, — thofe
of the fore-finger ( b ) come next to that in thicknefs,
but not in length, for thofe of the ring-finger (e) are
a little longer. The little finger ( d ) has the fmalleft
bones. Which difpofition is the bell; contrivance for
holding the largeft bodies ; becaufe the longeft fingers
are applied to the middle largeft periphery of luch
fubftances as are of a fpherical figure (e).

The ules of all the parts of our fuperior extremities
are fo evident in the common actions of life, that it
is needlefs to enumerate them here ; and therefore I
ftiall proceed to the laft part of the fkeleton. Only,
left I Ihould feem to have forgot the fmall bones at
the joints of the hand, 1 defire now to refer to the
defeription of them, under the common title of fefa -

S moid

(i) K»v<fuX«i.

(c) MiraxoiiJ'vxn, pifavu^-la.

(a) Kecrarvyov, opax*iA»r, infamis, impudicus, verpus, famofus,
obfccenus.

(b) AtxTixof, indicator, Ki^avof, demonftrativus, falutaris.

(c) ‘larpixor, *afay.tiTt{, J«xTuxiuT»f, txt&eiTVf, annularis, me*
dieus, cordis digitus.

(rf) MuuvJ,, uriTur, auricularis, minimus.

(e) Galen de ufu part, lib. I. cap. 24,

206 Of the SKELETON.

tnoict bones, which I have placed after the bones of the
feet.

Of the INFERIOR EXTREMITIES.

THE INFERIOR EXTREMITIES depend
from the acctabula of the ojfa innominata ; are
commonly divided into three parts, viz. the thigh,
leg, and foot.

The THIGH (f) has only one bone ; which is the
longed of the body, and the larged and dronged of
any of the cylindrical bones. The fituation of it is
not perpendicular ; for the lower end is inclined con-
fiderably inwards ; fo that the knees are al mod con-
tiguous, while there is a confiderable didance be-
tween the thigh-bones above *, which is of good ufe
to us, fince fufficient fpace is thereby left for the ex-
ternal parts of generation, the two great cloacet of u-
rine and faces, and for the large thick mufcles that
move the thigh inwards ; and at the fame time this
fituation of the thigh-bones renders our progredion
quicker, furer, draighter, and in lefs room ; for, had
the knees been at a greater didance from each other,
we mud have been obliged to defcribe fome part of a
circle with the trunk of our body in making a long
dep, and, when one leg was railed from the ground,
our centre of gravity would have been too far from
the bafe of the other, and we diould confequently
have been in hazard of falling ; fo that our deps
would neither have been diaight nor firm ; nor would
it have been poflible to walk in a narrow path, had
our thigh-bones been otherwife placed. In confe-
quence, however, of the weight of the body bearing
fo obliquely on the joint of the knee, by this fitu-
ation of the thigh-bones, weak ricketty children be-
come in-knee’d.

The upper end of the thigh-bone is not continued
in a draight line with the body of it, but is fet off

obliquely

(/) Mi pot, femen, coxa, agis, anch* os, crus, femur.

207

Of the SKELETON.

obliquely inwards and upwards, whereby the diftance
here between thefe two bones at their upper part is
confiderably increafed. — This end is formed into a
large fmooth round head (g), which is the greater por -
tion of a fphere unequally divided. — Towards its
lower internal part a round rough fpongy pit is ob-
fervable, where the ftrong ligament, commonly, but
unjuftly, called the round one, is fixed, to be extend-
ed from thence to the lower internal part of the re-
ceiving cavity, where it is confiderably broader than
near to the head of the thigh-bone. — The l'mall part
below the head, called the cervix of the os femoris ,
has a great many large holes into which the fibres of
the ftrong ligarv nt, continued from the capiular,
enter, and are thereby furely united to it ; and round
the root of the neck, where it rifes from the bone, a
rough ridge is found, where the capfular ligament of
the articulation itfelf is connected. — Below the back-
part of this root, the large unequal protuberance call-
ed trochanter major ( h), Hands out ; the external con-
vex part of which is diftinguifhed into three different
furfaces, whereof the one on the fore-part is fcabrous
and rough, for the infertion of the glut ecus minimus ;
the fuperior one is fmooth, and has the glutxus me dins
inferted into it j and the one behind is made flat and
fmooth by the tendon of the glutetus maximus palling
over it. — The upper edge of this procefs is fharp and
pointed at its back-part, where the glutaus medius is
fixed ; but forwards it is more obtufe, and has two
fuperficial pits formed in it : Into the fuperior of
thefe, the piriformis is implanted ; and the obturator
internus and gemini are fixed into the lower one. —
From the backmoft prominent part of this great tro -
'^yiter, a rough ridge runs backwards and down-
rNvards, into which the quadratus is inferted — In tilt
deep hollow, at the internal upper fide of this ridge,
the obturator externus is implanted. — More internally*
a conoid procefs called trochanter minor (r), riles for

S 2 thii

(?) Vertebrum.

(j) t\vro(, rotator oatis, malum gtanatum tcfUcuIoruni.-

(i) Rotator minor.

Of the SKELETON.

2c8

the inlertion of the mufculus pfoas anti iliacits internets ;
and the peflineus is implanted into a rough hollow
below its internal root. — The mufcles inferted into
thefe two procefles being the principal inrtruments of
the rotatory motion of the thigh, have occafioned
the name of trochanters to the procefles. — The ten-
dons that are fixed into, or pafs over the great trochan-
ter, caufe bruifes by falls on this part to be attended
with great pain and weaknefs of the limb, which
generally remain long.

The body of the os femoris is convex on the fore-
part, and made hollow behind, by the adtion of the
mufcles that move it and the leg, and for the conve-
niency of fitting, without bearing too much on thefe
mufcles; and probably the weight of the legs de-
pending from the thighs in that pofture, contributes
to this curvature. — The fore-part of the thigh-bone
is a little Hatted above by the beginning of the crur.eus
mufcle, as it is alfo below by the fame mufcle and the
reflus. — Its external furface is likewife made flat be-
low by the vajhts ex tern us, where it is feparated from
the former by an obtufe ridge. — The vajhis interims
depretles a little the lower part of the internal furface.
— The pollerior concave furface has a ridge riling in
its middle commonly called linen afpera, into which
the triceps is inferted, and the fliort head of the biceps
Jirxor tibi.e rifes from it. — At the upper part of it the
medullary veflels enter by a fmall hole that runs ob-
liquely upwards; a little above which there is a
rough fojfn or two, where the tendon of the glut nus
mnximus is fixed. — The lower end of the linen a/pern
divides into two, which delcend towards each fide —
The two vq/ii mufcles have part of their origin from
thefe ridges; and the long tendon of the triceps,
fixed to the internal, by means of part of the fajern
aponeurotica of the thigh. — Near the beginning of the
internal ridge, there is a difeontinuation of the ridge
where the crural artery pafles through the aponeurofts.
— Between thefe two rough lines, the bone is made
flat by the large blood-vefl'els and nerves which pafs

upon

Of the SKELETON". 209

spon it ; and near the end of each of thefe ridges, a
finall fmooth protuberance may often be remarked,
where the two heads of the external gajlrocnemius
mufcle take their rife, and where felamoid bones are
fometimes found {k) ; and fcom the fore-part of the
internal tubercle, a llrong ligament is extended to the
in fide of th e tibia.

The lower end of the os femoris is larger than any
other part of it, and is formed into a great protuber-
ance on each fide, called its condyles ; between which
a confiderable cavity is found, efpecially at the back-
part, in which the crural vefl'els and nerves lie im-
merfed in fat. — The internal condyle is longer than
the external, which mull happen from the oblique
pofition of this bone, to give lefs obliquity to the
leg. — Each of thefe procefles feems to be divided in
its plain fmooth furface. The mark of divifion on
the external is a notch, and on the internal a fmall
protuberance. The fore-part of this divifion, on
which the rotnla moves, is formed like a pulley, the
external fide of which is higheft. — Behind, there
are two oblong large heads, whofe greatell extent is
backwards, for the motion of the tibia y and from
the rough cavity between them, but near to the bafe
of the internal condyle, the llrong ligament com-
monly called the crop one, has its rife ; — a little a-
bove which a rough protuberance gives infertion to
the tendon of the triceps. — The condyles, both on the
outer and inner fide of the knee, are made flat by the
mufcles palling along them. — On the back-part of the
Internal, a flight depreffion is made by the tendons
©f the gracilis and pirtorius ; and on the external fuch
another is formed by the biceps flexor cruris ; behind
which a deep fojfa is to be obferved, where the popli-
teus mufcle has its origin. — From the tubercle im-
mediately before this cavity, a Irong round ligament
goes out to the upper part of the fibula. — Round this
lower end of the thigh-bone, large holes are found*
into which the ligaments for the fecurity of the joint

S 3 ate

( k ) Vefal. lib. I. cap. a8. & JOk.

210

0? the SKELETON,

are fixed, and blood-veflels pals to the internal lub-
ftance of the bone.

All the procefles of the femur are cartilaginous in
new-born children, and afterwards become fmall a-
pophyfesy with large epiphfes.

The thigh-bone being articulated above with the
acetabulum of the ojfa innominnta% which affords its
round head a fecure and extenfive play, can be mov-
ed to every fide ; but is reftrained in its motion out-
wards, by the high brims of the cavity, and by the
round ligament ; for otherwife, the head of the bone
would have been frequently thurft out at the breach
of the brims on the infide, which allows the thigh to
move conliderably inwards. — The body of this bone
enjoys little or no rotatory motion, though the head
mod commonly moves round its own axis j becaufe
the oblique progrefs of the neck and head from the
bone is fuch, that the rotatory motion of the head
can only bring the body of the boue forwards and
backwards : Nor is this head, as in the arm, ever ca-
pable of being brought to a ftraight dire£tion with its
body -y fa far however as the head can move within
the cavity backwards and forwards, the reft of the
bone may have a partial rotation. — When the thigh-
bone refifts the actions of its mufcles more than the
trunk of the body can then do, as in Handing, thefe
mufcles have their effe£l on the trunk, caufing it to
bend forward, railing it up, inclining it to the one
or the other fid'e, twilling it obliquely, £sV. which
the rolling of the acetabula of the effa innominata on
the round heads of the thigh-bones is well fitted
for. — The os femoris is articulated below to the tibia
and rotula in the manner afterwards to be deferibed.

The ncarnefs of the fmall neck to the round head
of the thigh-bone, and its upper end being covered,
with very thick mufcles, make greater difficulty in
diitinguilhing between a luxation and fra&ure here,,
than in any other part of the body.

The LEG (b) is compofed, according to the com-
mon.

<$) crus, tibia.

211

Of the SKELETO N.

mon account, of two bones, tibia and fibula , though
it feems to have a very good title to a third, the ro-
tula ; which bears a ftrong analogy to the olecranon
of the ulna, and moves always with the other two.

TIBIA , (c), fo called from its refemblance to an
old mufical pipe or flute, is the long thick triangular
bone, fituated at the internal part of the leg, and
continued in almoft a flraight line from the thigh-
bone.

The upper end of the tibia is large, bulbous, and
fpongy, and is divided into two cavities, by a rough
irregular protuberance (d), which is hollow at its mod
prominent part, as well as before and behind. 1 he
anterior of the two ligaments that compofe the great
crofs one, is inferted into the middle cavity, and the
deprefiion behind receives the pofterior ligament. —
The two broad cavities at the fides of this protube-
rance arc not equal •, for the internal is oblong and
deep, to receive the internal con/lyle of the thigh-bone j
while the external is more fuperficial and rounder,
for the external condyle. — In each of thefe two ca-
vities of a recent fubjedd, a femilunar cartilage is pla-
cet), which is thick at its convex edge, and becomes
gradually thinner towards the concave or interior
edge. — The middle of each of thefe cartilages is broad,
and the ends of them turn narrower and thinner, as
they approach the middle protuberance of the tibia. —
The thick convex edge of each cartilage is connedded
to the capfular and other ligaments of the articula-
tion, but fo near to their rife from the tibia , that
the cartilages are not allowed to change place far j
while the narrow ends of the cartilages becoming al-
molt ligaments, are fixed at the infertion of the ftrong
crols ligament into the tibia , and feem to have their
fubftance united with it ; therefore a circular hole is
left between each cartilage and the ligament, in
which the mod prominent convex patt of each con-
dyle of the thigh-bone moves. — The circumference of

thefe

( c ) VlfOKvnfinv, ovTix.vxy.iovy focilc majus, arundo major, caona:
major, canna domeftica cruris.

(d] bixfvtrt;, vivpo^ovxpuSrif, tuber, tubcrculuuv

2i2 Of the SKELETON.

thefe cavities is rough and unequal for the firm corn*
nedlion of the ligaments of the joint. — Immediately
below the edge at its back- part, two rough flatted
protuberances dand out : Into the internal, the ten-
don of the feniimembranofus mufcle is inferted ; and a
•part of the crofs ligament is fixed to the external. —
On the outfide of this lad tubercle, a fmooth flightly-
JiblJowed furface is formed by the adtion of the popji-
taus mufcle.

,,,iBelow the fore-part of the upper end of the tibia,
a confiderable rough protuberance ( e ) rifes, to which
the drong tendinous ligament of the rotula is fixed. —
On the internal fide of this, there is a broad fcabrous
Rightly-hollowed furface, to which the internal long
ligament of the joint, the aponeurofis of the vafius in-
ternus , and the tendons of the fcmmervofus , gracilis,.
and fartorius , are fixed. — The lowed part of this
furface is therefore the place where the tibia ought
to be fawed through in an amputation, fo as not to
have too long and troublefome a dump, and, at the
the fame time, to preferve its motions, by faving the
proper mufcles. — Below the external edge of the up-
per end of the tibia, there is a circular flat furface,
covered in a recent fubjedl with cartilage, for the ar-
ticulation of the fibula ; — between which and the an-
terior knob, there is a rough hollow from which the
tibialis anticus, and extenfor digitorum lotigus, take their
origin. — From the fmooth flat furface, a ridge runs ob-
liquely downwards and inwards, to give rife to part
of the foist us, tibialis pofiicus, and flexor digitorum lun-
gus, and infertion to the aponeurofis of the femimem-
branofus which covers the poplitieus, and to fome of
the external fibres of this lad named mufcle. — At the
infide of this ridge an oblique plain furface is left,
where the greated part of the mufculus poplitieus is in-
ferted.— The remaining body of the tibia is triangu-
lar.— The anterior angle is very fharp, and is com-
monly called the fpine or Jhin ( f )*. This ridge is not

draight

(<■) ’A*rixvi)/tiiov, anterior tuber.

(fj Axwfi*, fpina, crca, liaea prima tibiae, angulus acutus^

Of the S K E L E T O N.

213

ftraight ; but turns firft inwards, then outwards, and
laflly inwards again. — The plain internal fide is
fmooth and equal, being little fubje&ed to the ac-
tions of mufcles ; but the external fide is hollowed
above by the tibialis a/iticus , and below by the exten -
for digitorum longus and extenfor pollicis longus. — The
two angles behind thefe Tides are rounded by the ac-
tion of the mufcles ; — the pofterior fide comprehended
between them is not fo broad as thofe already men-
tioned, but is more oblique and flatted by the a&ion
of the tibialis poficits and flexor digitorum longus. — Some
way above the middle of the bone the internal angle ter-
minates, and the bone is made round by the prefiure
of the mufculus folaus. — Near to this, the paflage of the
medullary veflels is feen flanting obliquely downwards.

The lower end of the tibia is made hollow, but fo
as a fmall protuberance rifes in the middle. — The in-
ternal fide of this cavity, which is fmooth, and in
a recent fubjett is covered with cartilage, is pro-
duced into a confiderable procefs, commonly nam-
ed malleolus internus (g) ; the point of which i»
divided by a notch, and from it ligaments are fent
out to the foot. — We ought to obferve here, that this
internal malleolus is fituated more forwards than the
internal condyle of the upper end of this bone ; which
is necefiary to be remembered in reducing a fra&ure
of the leg (b). — The external fide of this end of the
tibia has a rough irregular femilunar cavity formed in
it, for receiving the lower end of the fibula — The
poflerior fide has two lateral grooves, and a fmall
middle protuberance. In the internal depreflion, the
tendons of the mufculus tibialis poflicus and jitxor digi-
torum longus are lodged; and in the external, the
tendon of the flexor longus pollicis plays. — From the
middle protuberance, ligamentous Iheaths go out,
for tying down thefe tendons.
rI he articulations and motions of the tibia fhall be

explained,

(g) 'Sfvfov, rrta-ev, talus, clavicula, clavilla interior, clavilia 1 i<v
nultica.

(A) Window, Expofition anatouiiquc des os lees, feet. 865.

214 Qf the SKELETON.

explained, after all the three bones of the leg are de-
scribed.

Both the ends of the tibia are cartilages at birth,
and become afterwards epiphyfes.

FIBULA (z) is the fmall long bone, placed on the
outfide of the leg, oppofite to the external angle of
the tibia ; the drape of it is irregularly triangular.

The head of the fibula has a Superficial circular ca-
vity formed on its infide, which, in a recent fubjedl,
is covered with a cartilage, but fo elofely connected
to the tibia by ligaments, as to allow only a fmall
motion backwards and forwards. — This head is pro-
tuberant and rough on its outfide, where a flrong
round ligament and the inufculus biceps are inferted
and below the back-part of its internal fide, a tuber-
pie may be remarked, that gives rife to the flrong
tendinous part of the foleeus mufcle.

The body of this bone is a little crooked inwards
and backwards, which figure is owing to the actions
of the mufcles ; but is ftill further inereafed by nur-
fcf, who often hold children carelcfsiy by the legs. —
The Sharped angle of the fibula is forwards, on each
fide of which the bone is confiderably, but unequally,
deprefied by the bellies of the feveral mufcles that
rife from, or act upon it ; and, in old people, thefe
mufcles make didindt finuoGties for themfelves. —
The external furface of the fibula is depreffed oblique-
ly from above downwards and backwards, by the two
perotuei. — Its internal furface is unequally divided in-
to two narrow longitudinal planes, by an oblique ridge
extended from the upper part of the anterior angle,
to join with the lower end of the internal angle.
To this ridge the ligament dretched between the two
bones of the leg is connected. — The anterior of the
tw'O planes is very narrow above, where the extenfor
longus digit or inn and extenfor longus pollicis arife from
it ; but is broader below, where it has the print of
the nonus Vefalii. — The poderior plane is broad and

hollow,

(?) Tlttpatuv/xion, perone, focile minus, arundo minor, canna mlr
nor cruris, tira, radius.

Of the SKELETON.

2 r£

hollow, giving origin to the larger (hare of the tibialis
j>ofiicus. — The internal angle of this bone has a tendi-
nous membrane fixed to it, from which fibres of the
flexor digitorum longus take their rife. — The pofterior
furface of the fibula is the plained and fmootheft, but
is made flat above by the foleeus , and is hollowed be-
low by th t flexor pollicis longus. — In the middle of this
furface the canal for the medullary veffels may be
feen flanting downwards.

I have taken particular notice of the entry and di-
rection of the medullary veffels of the large bones of
the extremities (a) ; becaufe, in feveral chirurgical
cafes, a furgeon, who is ignorant of this, may do
mifchief to his patient. Thus, for example, if thefe
veffels are opened very near to their entry into the
bone, or while they are in the oblique palfage through
it, an obdinate haemorrhagy may enfue : For the ar-
teries being connected to the bony paffage, ftvptics,
and other like corrugators, are vainly applied ; com-
prefling inflruments can do no fervice, and ligatures
cannot be employed. — There feems to be a particular
defign in the contrivance of thefe canals •, thofe in the
os humeri , tibia , and fibula , running obliquely down-
wards from their external entry ; whereas in the ra -
dius, ulna, and os femoris, they flant upwards, where-
by the arteries and nerves which are fent into thefe
three lafl bones, muff f offer a confiderable reflection
before they come at the cancelli. The reafon of this
diverfity may perhaps be, that the arteries, which are
fo fmall within the bones as to have no drong con-
tractile propelling force in their coats, and where they
are not affided by the aCtion of any moving neigh-
bouring organ, fhould have, at lead in their paffage
through the bone, a favourable defcent for their li-
quids: Which, it is evident, they have in the de-
fending oblique paffages formed for them in the firft
clafs of bones, to wit, the os humeri, tibia, and fibu-
la, which are generally depending ; and they alfo mod
frequently acquire the like advantage in ttie radius ,

ulnaf

(a) Havers, Ofteolog. nov. difc. I. p. 59,

Of the SKELETON.

* i(5

ulna, and os femoris ; hecaufe the hand, in the mod
natural podure, is higher than the elbow ; and when
we fit or lie, the lower end of the thigh bone comes
to be at lead as high raifed as the upper. In (landing
and walking, or when the arms are moved, the blood
mud indeed afeend as it pafles through the bones of
the fore-arm and thigh ; but the preflure of the muf-
cles, then in a£lion, on the veflels, before they enter
the bones, is fufficient to compenfate thedifadvantage
of their courfe. This reafoning feems to be dill en-
forced, by obferving, that this padage is always near-
er the upper than the lower ends of thefe bones.

The lower end of the fibula is extended into a
fpongy oblong head, on the infide of which is a con-
vex, irregular, and frequently a fcabrous furface, that
is received by the external hollow of the tibia , and fo
firmly joined to it by a very thin intermediate carti-
lage and drong ligaments, that it fcarce can move. —
Below this, the fibula is dretched out into a coronoid
procefs, that is fmooth, covered with cartilage on its
internal fide, and is there contiguous to the outfide
of the fird bone of the foot, the afiragalus , to fecure
the articulation. This procefs, named malleolus ex-
ternus , being fituated farther back than the internal
malleolus, and in an oblique direction, obliges us na-
turally to turn the fore-part of the foot outwards (b).
At the lower internal part of this procefs, a fpongy
cavity for mucilaginous glands may be remarked;
from its point ligaments are extended to the afiraga-
lus, os calf is, and os naviculare, bones of the foot ;
and from its infide fliort drong ones go out to the
afiragalus . On the back-part of it a finuofity is made
by the tendons of the perotuci mufcles. — When the
ligament extended over thefe tendons from the one
fide of the deprefiion to the other is broke, dretched
too much, or made weak by a fprain, the tendons
frequently dart forwards to the outfide of the fibula.

The conjunction of the upper end of the fibula
with the tibia is by plain furfaces tipped with carti-
lage

(b) Window, Mcmoircs dc 1'acad. des feientes, l]2i.

Of the SKELETON. 217

lage, and at its lower end the cartilage feems to glue
the two bones together, not, however, fo firmly in
young people, but that the motion at the other end
of fuch a long radius is very obferveable. — In old fub-
jects I often fee the two bones of the leg grown to-
gether at their lower ends.

The principal ufe of this bone is to afford origin
and infertion to mufcles; the diredfion of which may
be a little altered on proper occafions, by its upper
part fhuffling backwards and forwards. — It like wife
helps to make the articulation of the foot more fecure
and firm. — The ends of the tibia and fibula being
larger than their middle, a ipace is here left, which
is filled up with fuch another ligament as I deferibed
extended between the bones of the fore-arm ; and
which is alfo difeontinued at 'its upper part, where
the tibialis anticus immediately adheres to the folaus
and tibialis pof icus ; but every where elfe it gives ori-
gin to mufcular fibres (a).

lloth the ends of this bone are cartilaginous in a
ripe child, and affume the form of appendices before
• they are united to its body.

ROTULA ( b ) is the fmall fiat bone fituated at the
fore-part of the joint of the knee. — Its fhape refem-
bles the common figure of the heart with its point
downwards. — The anterior convex furface of the ro~
tula is pierced by a great number of holes, into which
fibres of the ftrong ligament that is fpread over it,
enter. — Behind, its furface is fmooth, covered
with cartilage, and divided by a middle convex ridge
into two cavities, of which the external is largeft ;
and both are exactly adapted to the pulley of the os
fetnoris , on which they are placed in the molt ordina-
ry unftraining poftures of the leg; but when the leg
is much bended, the rotula defeends far down on the
condyles ; and when the leg is fully extended, the
rotula rifes higher, in its upper part, than the pullev

T . of

(a) Weitbrecht, Syndefmolog. p. 156.

(i) ’Exi/xvKii, fj.ia.av. pif, ir/yavcmf, pa-

tella, mola, genu, feutiforme os, cartilaginofuni, difekornse, oculus
genu.

2 1 8 Of the SKELETON.

of the thigh-bone. — The plain fmooth furface is fur-
rounded by a rough prominent edge, to which the
capfular ligament adheres : — Below, the point of the
bone is fcabrous, where the ftrong tendinous ligament
from the tubercle of the tibia is fixed. — The upper hori-
zontal part of this bone is flatted and unequal, where
the tendons of the extenfors of the leg are inferted.

The fubftance of the rotula is cellular, with very
thin external firm plates : But then thefe cells are fo
fmall, and fuch a quantity of bone is employed in
their formation, that fcarce any bone of its bulk is
fo ftrong. Befides, it is covered all over with a thick
ligament, (as it was oblerved, that this fort of bones
generally is), to conne£t its fubftance, and is moveable
to one fide or other ; therefore is fufficiently ftrong to
refill the ordinary atflions of the large mufcles that
are inferted into it, or any common external force
applied to it ; while a fixed procefs, fuch as the ole-
cranon, would not have been fufficient to bear the
whole weight of our bodies, which frequently falls
on it, and would have hindered the rotatory motion
of the leg. Notwithftanding thefe precautions to
preferve this bone from fuch injuries, yet I have feen
a tranfverfe fracture in it, when, by the report of the
patient, and of the people about him, and by the
want of fwelling, difcolouring, or other mark of
bruife or contufion, it was plain the bone was broken
by the violent Braining effort of the mufcles (c).
Though my patient recovered the ufe of the joint of
the knee, yet I think it reafonable to believe, that this
fort of fra£lure is commonly attended with difficulty
of motion, after the broken parts of the rotula are
reunited ; becaufe the callous matter probably extends
itfelf into the cavity of the joint, where it either
grows to fome of the parts, or makes fuch an inequa-
lity on the furface of this bone, as does not allow it
to perform the neceffary motions on the condyles of
the femur ( d ).

At

(<r) See Ruyfch. Obferv, anat. chirurg. obf. $•

\d) Pare, liv. IJ. cap. a*.

Of the SKELETON.

219

At the ordinary time of birth, the rotula is entire-
ly cartilaginous, and fcarcely aflumes a bony nature
fo foon as mod epiphyfes do-

The parts which conftitute the joint of the knee
being now defcribed, let us examine what are its
motions, and how performed. — The two principal
motions are fle£Hon and extenfion. — In the former of
thefe, the leg may be brought to a very acute angle
with the thigh, by the condyles of the thigh-bones
being round and made fmoorh far backwards. In
performing this the rotula is pulled down by the tibia .
— When the leg is to be extended, the rotula is drawn
upwards, confequently the tibia forwards by the ex-
tenfor mufcles ; which, by means of the protuberant
joint, and of this thick bone with its ligament, have
in effect the chord, with which they atl, fixed to the
tibia at a confiderable angle, therefore act with ad-
vantage ; but are reflrained from pulling the leg far-
ther than to ]a ftraight line with the thigh, by the
pofterior part of the crofs ligament, that the bod/
might be fupported by a firm perpendicular column :
For at this time the thigh and leg are as little move-
able in a rotatory way, or to either fide, as if they
were one continued bone. — But when the joint is a lit-
tle bended, the rotula is not tightly braced, and the
pofterior ligament is relaxed *, therefore this bone may
be moved a little to either fide, or with a fmall rota-
tion in the fuperficial cavities of the tibia \ which is
done by the motion of the external cavity backwards
and forwards, the internal ferving as a fort of axi3
(a). Seeing then one part of the crofs ligament is
fituated perpendicularly, and the pofterior part is
ftretched obliquely from the internal condyle of the
thigh outwards, that pofterior part of the crofs liga-
ment prevents the leg’s being turned at all inwards.*
but it could not hinder it from turning outwards al-
moft round, was not that motion confined by the la-
teral ligaments of this joint, which can yield little.

T 2 This

(a) Window, Expo fit ion anatomique du corps humain, traitc ds
os fees, § 97 6.

9

2 20

Of the SKELETON.

This rotation of the leg outwards is of good advan-
tage to us in crofling our legs, and turning out feet
outwards, on feveral necefiary occalions ; though it
is altogether fit this motion fhould not be very large,
to prevent frequent luxations here. While all thefe
motions are performing, the part of the tibia that
moves immediately on the condyles is only fo much
as is within the cartilaginous rings, which, by the
rhicknefs on their outfides, make the cavities of the
tibia more horizontal, by raifing their external fide
where the furface of the tibia Hants downwards. By
this means the motions of this joint are more equal
and fieady than otherwife they would have been.
The cartilages being capable of changing a little their
lituation, are fit for doing this good office in the dif-
ferent motions and poll ures of the member, and like-
wife contribute.to make the motions larger and quicker.

On account of the very large furface of the bones
forming the joint of the knee, and the many flrong
ligaments connecting them, luxations feldom happen
here. But thefe very ligaments, the aponeurfis paf-
ling over this joint, the quantity of fat and mucila-
ginous glands necefiary for lubricating it, make it
more fubject to •white-fivellings, dropfies, and fuch
other diforderSj than any other joint of the body.

The FOOT is divided, as well as the hand, into
three parts, viz. tarfus , metatarfus , and toes : , I n the
dclcription of which, the feveral furfaces fhall be
named, according to their natural fituation, viz. the
broad of the foot, fhall be called fuperior ; the foie ,
inferior ; the fide on which the great toe is, internal ;
that where the little toe is, external. >

'J'h a tarfus (• a ) confifisof feven fpongy bones; to wit,
the afragalus, os calcis, naviculare , cuboides , cuneiformc
externum , cuneiforme medium , and cuneiforme internum .

The ajlragalus is the uppermoft of thefe bones. —
The os calcis is below the ajlragalus, and is confider-
•ably prominent backwards beyond the other bones, to
form the heel. — The os naviculare is in the middle of

the

(a) Rafictta.

221

Of the SKELETON.

the internal fide of the tarfus. — The os cuboides is the
moll external of the row of four bones at its fore-part.
— The os ctmefoftne externum is placed at the in fide
of the cuboid. — The cuticifonne medium is between the
external and internal cuneiform bones, and the internal
cuneiform is put at the internal fide of the foot.

That the defcription of thefe bones may not be
immoderately fwelled with repetition, I defire, once
for all, to obferve, That wherever a ridge is men
rioned, without a particular ufe affigned, a ligament
is underftood to be fixed to it *, or where a fpongv
rough cavity, depreffion, or fojfa is remarked, without
naming its ufe, a ligament is inferted, and mucilagi
nous glands ate lodged : For fuch will occur in the de '
tail of each of thefe bones.

The upper part of the ajlragalus (b) is formed into
a large fmooth head (c), which is flightly hollowed
in the middle ; and therefore refembles a fuperficial
pulley, by which it is fitted to the lower end of the
tibia. — The internal fide of this head is flat and fmooth,
to play on the internal malleolus. — The external fide
has alfo fuch a furface, but larger, for its articulation
with the external malleolus. — Round the bafe of this
head there is a. rough fojfa ; and, immediately before
the head, as alfo below its internal fmooth furface,
we find a confiderable rough cavity.

The lower furface of the ajlragalus is divided by
an irregular deep rough fojfa which at its internal
end is narrow, but gradually widens, as it ftretches
obliquely outwards and forwards. — The fmooth fur-
face, covered with cartilage, behind this fojfa, is large,
oblong, extended in the fame oblique fituation with
the fojfa, and concave, for its conjunction with the
os calcis. — The back-part of the edge of this cavity is
produced into two tharp-pointed rough procefles, be-
tween which is a depreffion made by the tendon of
the fiexor pollicis longus. — The lower furface before

T 3 the

(£) Arpitt, talus, balifti os, malleolus, chaib, quatrio, os tefli-
rae, clavicular, unciforme.

(0 TtT/Mi :po(.

222

Of the SKELETON.

the fojfa is convex, and compofed of three diftin£fc
fmooth planes. The long one behind, and the exterior
or fliorteft., are articulated with the heel-bone •, while
the internal, which is the mod convex of the three,
refls and moves upon a cartilaginous ligament, that
is continued from the calcaneum to the os fcaphoides.
Without which ligament, the ajlragalus could not be
fultained, but would be prefled out of its place by
the great weight it fupports, and the other bones of
the tarfus would be feparated. Nor would a bone be
fit here, becaufe it mud have been thicker than could
conveniently be allowed ; otheiwife it would break,
and would not prove fuch an eafy bending bafe, to
Jeflen the '{hock which is given to the body in leaping,
running, 5*rV.

The lore-part of this bone is formed into a convex
oblong frnooth head, called by fome its procefs, which
is received by the os naviculare. Round the root of
this head, efpecially on the upper furface, a rough
fojfa may be remarked.

The ajlragalus is articulated above to the tibia and
fibula, which together form one cavity. Though, in
this articulation, the bones have prominencies and ca-.
vities Co fmall, as might allow motions in all direc-
tions ; yet the flc£lion and extenfion are the mod
confiderable, the other motions being confined by the
malleoli , and by the flrong ligaments which go out
from the points of thefe proccfles to the ajlragalus and
or calcis. — When ;Jbe foot is bended, fo far as it is
commonly when we Hand, no lateral or rotatory mo-
tion is allowed in this joint ; for then the head of the
ajlragalus is funk deep between the malleoli , and the
ligaments arc tenfe ; but vvhen the foot is extended,
the ajlragalus can move a little to either fide, and
with a fmall rotation. By this contrivance the foot
is firm, when the weight of the body is to be fupport-
ed on it; and when a foot is raifed, we are at liber-
ty to direct it more exadtly to the place we intend
next to ftep upon. — The ajlragalus is joined below,
to the os colds ; and before, to the os navicular e, in

Of the SKELETON. 22*

the manner to be explained, when thefe bones are
deicribed.

A confiderable (hare of this bone is oflified in a
new-born infant.

Calcaneutn (d) is the largeft bone of the feven. —
Behind, it is formed into a large knob, commonly
Called the heel : The furface of which is rough be-
hind, where the tendo Achtllis is inferted into it; and
above it, it is hollow and fpongy. Farther forwards,
on the upper furface of the calcaneum , there is an ir-
regular oblong fmooth convexity, adapted to the con-
cavity at the back-part of the ajlragalus : And be-
yond this a narrow fcjfa is feen, which divides it from
two fmail concave fmooth furfaces, that are joined to
the fore-part of the ajlragalus . — Behind the pofterior
of thefe fmooth furfaces, which is the largeft, a fmail
finuofity is made by the tendon of the Jlexor digitorum
longus ; at the fore-part of which a fmail rough pro-
tuberance appears, that gives rife to the mufculus ex •
tetflor digitorum brevis.

The external fide of this bone is flat, with a fuper-
f\c\a\ fojfa running horizontally, in which the tendon
of the mufculus peronaus longus is lodged. — The inter-
nal fide of the heel-bone is hollowed, for lodging the
origin of the majfa cornea Jac. Sylvit, and for the
fafe paflage of tendons, nerves, and arteries. — Under
the fide of the internal fmooth concavity, a particular
groove is made by the tendon of the jlexor polluis lon-
gus ; and from the thin protuberance on this internal
fide, the cartilaginous ligament that fupports the a-
Jlragalusy goes out to the os naviculare ; on which li-
gament, and on the edge of this bone to which it is
fixed, the groove is formed for the tendon of the
jlexor digitorum profundus.

The lower furface of this bone is prefled flat at the
back-part, by the weight of our bodies ; and imme-
diately before this plane, there are two tubercles,
from the internal of which the mufculus abductor polli-
cis ;> flexor digitorum fublimis , as alfo part of the apo-

nturafs

(<0 Os calcis, jrnpv*j calcar pedis.

224

Of the SKELETON.

twn-cjis plantaris, and of the abduElor minimi digit}
haVe their origin ; and the other part of the abduHor
tmtwm digiti and apQncurof,s plantaris rifes from the
external. Before thefe protuberances this bone is
concave, for lodging the flexor mufcles ; and at its
fore-part we may obfervc a rough depreflion, from
which, and a tubercle behind it, the ligament goes
out that prevents this bone to be feparated from the
os cuboides.

The fore-part of the os calcis is formed into an ob-
long pulley-like fmooth furface, which is circular at
its upper external end, but is pointed below. This
fmooth furface is fitted to the os cuboides.

Though the furfaces by which the ajlragalus and ox
colas ztt articulated, feem fit enough for motion ;
yet the very ftrong ligaments by which thefe bones
are connected, prevent it, and render this principal
part of our bafe, which refts on the ground, to ZiU
the os calcu , firm. *

A large fhare of the heel-bone is offified at the or-
dinary time of birth, and the large knob appears af-
terwards in form of an epiphy/'e.

Os naviculare (x), is fomewhat circular.— It is form-
ed into an oblong concavity behind for receiving the
anterior head of the ajlragalus — On the upper fur-
face there is a rough /^.-Below, the or naviculare
is very unequal and rough ; but hollow for the fafe-
ty of the mufcles— On its infide a large knob rifes
out, from which the abduElor pollicis takes in part its
origin, the tendon of the tibialis pojlicus isinferted in-
to 1c £n-d Jt _two rernarkable ligaments are fixed;

the firlt is the ftrong one, formerly mentioned, which
fupports the ajlragalus ; the fecond is ftretched from
this bone obliquely crofs the foot, to the metatarfal
bones of the middle toe, and of the toe next to the
little one.- On the outfide of the os naviculare there
is a femicircular fmooth furface, where it is joined
to the os cuboides — The fore-part of this bone is all

covered

(f) ’Sf.xftutnc, os cymbs,

Of the SKELETON. 225

covered with cartilage, and is divided into three
fmooth planes, fitted to the three ojfa cuneiformia.

The os naviculare and ajtragalus are joined as a ball
and focket, and the naviculare moves in all directions
in turning the toes inwards, or in railing or depref-
ling either fide of the foot, though the motions are
greatly reftrained by the ligaments which conneCb
this to the other bones of the tarfus. — A weaknefs of
thefe ligaments caufes fometimes an unnatural turn of
the fore-part of the foot inwards.

The os naviculare is wholly cartilaginous in a new-
born infant.

OS CUBOIDES (a) is a very irregular cube.—
Behind, it is formed into an oblong unequal conca-
vity, adapted to the fore-part of the os calcis. — On
its internal fide, there is a fmall femicircular fmooth
cavity, to join the os naviculare. — Immediately be-
fore which, an oblong fmooth plane is made by the
cs cuheiforme externum. — Below this, the bone is hol-
low and rough. — On the internal fide of the lower
furface, a round protuberance and foJTa are found,
where the mufculus abductor pollicis has its origin.
On the external fide of this fame furface, there is a
round knob, covered with cartilage ; immediately
before which, a fmooth fojfa may be obferved, in
which the tendon of the peromtus primus runs ob-
liquely crofs the foot ; and on the knob, the thin flat
cartilage proper to this mufcle plays ; in place of
which, fometimes a bone is found : More externally
than the knob, a rough hollow is made, for the
ftrong ligaments ftretched betwixt this bone and the
es calcis. — Before, the furface of the os cuboides is flat,
fmooth, and (lightly divided into two planes, for fu-
ftaiuing the os metatarfi of the little toe, and of the
toe next to it.

The form of the back-part of the os cuboides , and
the ligaments connefting the joint there with the os

calcis t

rn) Tloxu tup?™, cubiformc, quadratum, grandinofum, variura»
Teflene, nrnltitorme.

226 Of the SKELETON.

calcis, both concur in allowing little motion in this
part.

The oflification-of this bone isfcarcely begun at the
birth. >

Os cuneiforme externum (b), if we regard its fixa-
tion or medium by its bulk, is much of the fhape of
a wedge, being broad and Hat above, with long fides
running obliquely downwards, and terminating in a
fliarp edge. — The upper furface of this bone is an
oblong fquare. — The one behind is nearly a triangle,
but not complete at the inferior angle, and is joined
to the os naviculare. — The external fide is an oblong
fquare, divided as it were by a diagonal ; the upper
half of it is finooth, for its conjunction with the os
cuboides : The other is a fcabrous hollow, and in its
fuperior anterior angle a fmall fmooth impreflion is
made by the os metatarfi of the toe next to the little
one. — The internal fide of this bone is alfo quadran-
gular, with the fore-part of its edge made flat and
fmooth by the os metatarfi of the toe next to the great
one, and the back-part is alfo Hat and finooth where
the os cuneiforme medium is contiguous to it. — The
fore-part of this bone is an oblong triangle, for fu-
ftaining the os metatarfi of the middle toe.

Os cuneiforme medium, or minimum, is ftill more
exaCtly the fhape of a wedge than the former. — It3
upper part is fquare ; — its internal fide has a flat
fmooth furface above and behind, for its conjunction
with the following bone ; with a fmall rough fojfa
below ; and a confiderable fharc of it is rough and
hollow. — The external fide is finooth and a little
hollowed, where it is contiguous to the laft deferibed
bone. — Behind, this bone is triangular, where it is
articulated with the os naviculare; and it is alfo
triangular at its fore-part, where it is contiguous to
the os metatarfi of the toe next to the great one.

Os cuneiforme maximum, or internum , differs from
the two former in its fixation, which is more ob-
lique than theirs. — Befides, its broad thick part is

placed

(b) ChalcoiJcum ei.tcraum.

Of the SKELETON.

227

placed below, and the fmall thin point is above and
outwards ; while its under broad furface is concave,
for allowing a fafe paflage to the flexors of the great
toe. — The furface of this os cuneiforme behind, where
it is joined to the os navicularey is hollow, fmooth,
and of a circular figure below, but pointed above. —
The external fide confifts of two fmooth and flat
furfaces, -whofe direction is nearly at right angles
with each other. With the pofterior, that runs ob-
liquely from below forwards and upwards, the os
cuneiforme minimum is joined ; and with the anterior,
whofe direction is longitudinal, the os metatarfi of the
toe next to the great one is connected. — The fore-
part of this bone is femilunar, but flat and fmooth,
for fuftaining the os metatarfi of the great toe. — The
internal fide is fcabrous, with two remarkable tu-
bercles below, from which the mufculus abductor pdii -
cis rifes, and the tibialis anticus is inferted into it6 up-
per part.

The three cuneiform bones are all fo fecured by li-
gaments, that very little motion is allowed in any of
them ; and they are cartilaginous in a foetus of nine
months.

Thefe feven bones of the tarfus , when joined, are
convex above, and leave a concavity below, for lodg-
ing fafely the feveral mufcles, tendons, veflels, and
nerves, that ly in the foie of the foot. — In the recent
fubjeft, their upper and lower furfaces are covered
with ftrong ligaments which adhere firmly to them ;

I and all the bones are fo tightly connected by thefe
and the other ligaments, which are fixed to the
rough ridges and foflle mentioned in the preceding de-
scription of the particular bones, that, notwithftand-
ing the many furfaces covered with cartilage, fome
of which are of the form of the very moveable ar-
ticulations, no more motion is here allowed, than
only to prevent too great a (bock of the fabric of the
body in walking, leaping, bfc. by falling on too folid
a bafe *, which, if it was one continued bone, would
jikewife be much more liable to be broken ; and in

order

228

Of the SKELETON.

order to make our foot accommodate itfelf to the fur-
faces we tread on, by becoming more or lefs hollow,
or by raifing or deprefling either fide of it, as might
be judged by what was faid of the particular bones.

Sprains here occafion, as in the wrift, great pain
and obllinate tumours, which too often caufe carious
bones.

METATARSUS ( c ) is compofed of five bones,
which, in their general chara£ters, agree with the
metacarpal bones ; but may be diftinguifhed from
them by the following marks : x. They are longer,

thicker, and ftronger. 2. Their anterior round ends
are not fo broad, and are lefs in proportion to their
bafes. 3. Their bodies are {harper above and flat-
ter on their fides, with their inferior ridge inclined
more to the outfide. 4. The tubercles at the lower
parts of the round head are larger.

The full or internal metatarfal bone is eafily di-
ftinguifhed from the reft by its thicknefs. — The one
next to it is the longeft, and with its (harp edge al-
moft perpendicular. — The others are (horter and
more oblique, as their fituation is more external.
Which general remarks, with the defcription I am
now to give of each, may teach us to diftinguifti them
from each other.

Oj- metatarfi pollicis is bv far the thickeft and
ftrongeft, as having much the greateft weight to fu-
ftain. Its bafe is oblong, irregularly concave, and of
a femilunar figure, to be adapted to the os cuneiforms
maximum. — The inferior edge of this bafe is a little
prominent and rough, where the tendon of the pero -
naus primus mufcle is inferted. — On its outfide an
oblique circular depreftion is made by the fecond
metatarfal bone. — Its round head has generally on its
fore-part a middle ridge, and two oblong cavities,
for the o]fa fefamoidea ; and on the external fide a de-
preffion is made by the following bone.

Os

( c ) 'S.rxioc, rihtn, planta, planum, vjftignim, folium, peftus, prat*
Cordium, pcfhifculum.

229

Of the SKELETON.

0/ metatarfi of the fecond toe, is the longed of
the five, with a triangular bafe fupported by the os
cuneiforme medium and the external fide produced into
a procefs; the end of which is an oblique fmooth

plane, joined to the os cuneiforme externum . Near

the internal edge of the bafe, this bone has two fmall
depreflions, made by the os cuneiforme maximum, be-
tween which is a rough cavity. — Farther forwards we
may obferve a fmooth protuberance, which is joined
to the foregoing bone. — On the outfide of the bafe
are too oblong fmooth furfaces, for its articulation
•with the following bone ; the fuperior fmooth furface
being extended longitudinally, and the inferior per-
pendicularly; between which there is a rough foffa.

Os metatarfi of the middle toe, is the fecond in
length. — Its bafe, fupported by the os cuneiforme ex-
ternum, is triangular, but flanting outwards, where
it ends in a fharp-pointed little procefs ; and the angle
below is not completed.

The internal fide of this bafe is adapted to the
preceding bone ; and the external fide has alfo two
fmooth furfaces covered with cartilage, but of a dif-
ferent figure ; for the upper one is concave, and, be-
ing round behind, turns fmaller as if advances for-
wards; and the lower furface is little, fmooth, con-
vex, and very near the edge of the bafe.

Os metatarfi of the fourth toe, is near as long as
the former, with a triangular flanting bafe joined to
the os cuboides , and made round at its external angle,
having one hollow fmooth furface on the outfide,
where it is prefled upon by the following bone, and
two on the internal fide, correfponding to the for-
mer bone; behind which is a long narrow furface
imprefled by the os cuneiforme externum.

Os metatarfi of the little toe, is the fliorteft, fituat-
ed with its two flat fides above and below, and with
the ridges laterally. — The bafe of it, part of which
refts on the os cuboides , is very large, tuberous, and
produced into a long-pointed procefs externally, where-

U part

.230 Of the SKELETON.

part of the abduElor minimi digiti is fixed ; and into
its upper part the peronaus Jccutidus is inferted. — Its
infide has a fiat conoidal furface, where it is conti-
guous to the preceding bone.

When we (land, the fore-ends of thefe metatarfal
bones, and the os calcisy are our only fupporters ; and
therefore it is neceflary they fliould be llrong, and
fhould have a confined motion.

The bones of the TOES are much a-kin to thofe
of the thumb and fingers; particularly the two of the
great toe are precifely formed as the two laft of the
thumb; only their pofition, in refpeff of the other
toes, is not oblique ; and they are proportionally
much flronger, becaufe they are fubje&ed to a greater-
force ; for they fuftain the force with which our
bodies are puflied forwards by the foot behind at
every ftep we make; and on them principally the
weight of the body is fupported, when we are raifed
on our tiptoes.

The three bones in each of the other four toes,,
compared to thofe of the fingers, differ from them ip
thefe particulars. — They are lefs, and fmaller in pro-
portion to their lengths: Their bafes are much

larger than their anterior ends : Their bodies are more

narrow above and below, and flatter on the Tides

The firff; phalanx is proportionally much longer than
the bones of the fecond and third, which are very
ftiort.

Of the four, the toe next to the great one, has the
largeft bones in all dimenfions, and more externally
the toes are lefs. — The little toe, and frequently that
next to it, have the fecond and third bones intimate-
ly united into one ; which may be owing to their
little motion, and the great preflure they are fubjedl-
ed to.

The toes are of good ufe to us in walking : for,
when the foie is raifed, they bring our body, with its
centre of gravity, perpendicular to the adyanded
foot.

\3

The

Of the SKELETON.

2'3 1

The bones of the metatarfus and toes, are in the
fame condition in children as thofe of the metacarpus
and fingers.

The only bones now remaining to complete the
defcription of the (keleton, are the fmall ones, which
are found at the joints of the fingers and toes, and in
fome other parts, called

OSSA SESAMOIDEA , which are of very diffe-
rent figures and fizes, though they are generally faid
to refemble the feed of th o. fefamum. — They fecm to
me nothing elfe than the ligaments of the articula-
tions, or the firm tendons of ftrong mufcles, or both,
become bony, by the comprefiion which they fuffer.
Thus the fefamo'id bones at the beginning of the gafi-
rocnemii mufcles, are evidently compofed of the ten-
dinous fibres only. — Thefe, at the firll joint of the
great toe, are as plainly the fame continued fubffance
with the ligaments and the tendons of the adductor y
flexor, brevis, and abductor. — That which is fometimes
'double at the fecond joint of that toe, is part of the
capfular ligament ; and if we enumerate the otruit
fefamoid bones that are at any time found, we may
obferve all of them formed in this manner. — Their
number, figure, fituation, and magnitude, are fo un-
certain, that it were in vain to infift on the differ-
ences of each ; and therefore I (hall only in general
remark,

1. That where-ever the tendons and ligaments are
firmeft, the actions of the mufcles ftrongeft, and the
compreffion greateit, there fuch bones are molt com-
monly found.

2. That, c/eteris paribus , the older the fubjedl is in
which they are fought, their number is greater, and
their fize is larger.

3. The more labour any perfon is inured to, he
has, azteris paribus , the molt numerous and largeft'
ojfa fejamoidea.

However, as the two at the firft joint of the great
toe are much larger than any other, are early form-
ed, and are feldom wanting in an adult, tve may

U 2 judge,

2^2

Of the SKELETON.

judge, that befides the more forcible caufe of their
formation, there fhould alfo be fome particular ad-
vantage necefl'ary at this place, rather than elfewhere,
which may poflibly be, to allow the Jlexor mufcles to
fend their tendons along this joint, fecure from com-
preffion in the hollow between the two oblong fefa-
moid bones ; while, by removing thefe tendons from
the centre of motion, and giving them the advantage
of an angle at their infertion, the force of the mufcles
is increafed, and therefore the great fuperincumbent
weight of our body in progreffion is more eafily
raifed.

A P P E N-

APPENDIX.

Of the Marks of a Jemale Skeleton’,

TO finifh the defcription of the bones, is gene-
rally to conclude the ojleology; but that no part
of the fubje£l may be left untouched, I think it ne-
ceflary to fubjoin the diftinguifhing marks of the
male and female flceletons ; and have chofcn to il-
luftrate them principally in the latter; bee aufe wo-
men having a more delicate conflitution, and afford-
ing lodging and nourifhment to their tender foctufe j,
tilf they have fuflicient ftrength and firmnefs to bear
the injuries of the atmofphere, and conta£l of other
more folid fubftances, their bones are frequently in-
complete, and always of a make in fome parts of the
body different from thofe of the robuft male ; which
agree to the defcription already given, unlefs where
the proper fpecialities of the female were particularly
remarked ; which could not be done in all places
where they occur, without perplexing the order of
this treatil'e : Therefore I chofe rather to fum them
up here by way of Appendix.

The caufes of the following fpecialities of the fe-
male bones may be reduced to thefe three : i. A weak
lax conflitution. 2. A fedentary ina&ive life, in-
creafing that conflitution. 3. A proper frame for
being mothers.

The bones of women are fmaller in proportion to
their length than thofe of men ; becaufe the force of
their mufcles is not fo great, nor is fuch flrong ex-
ternal force applied to them to prevent their ftretch-
ing out in length.

The deprefbons, ridges, fcabrous furfaces, and o-
ther inequalities made by the mufcles, are not fo

U 3 confpicuous

234

APPENDIX.

confpicuous in them ; becaufe their mufcles are nei-
ther fo thick nor ftrong, nor fo much employed, to
make fo ftrong prints on their bones.

Their os frontis is more frequently divided by a
continuation of the fagittal future, which depends
on the firft and fecond general caufes aftigned above,
for the fpecialities in their bones; as will appear af-
ter reflecting on the account given formerly of the
middle internal fpine of this bone.

Their clavicles are lefs crooked ; becaufe their arms
have been lefs forcibly pulled forwards, which in our
European women, efpecially thofe of diftinClion, is
more hindered by their garb.

Their Jternum is more raifed by long cartilages be-
low, that the thorax might be there widened in fome
proportion to what it is fhortened by the preflure up-
on the diaphragm , when they are with child.

The defeCt of bone, or the hole in the middle of
■the fternum , is ofteneft found in them, to allow the
paffage of the mammary veffels, fay fome ; but, in
my opinion, this is owing to a lax conftitution, by
which the offification is not fo foon completed as in
men, where the aCtion of the folids is vigorous, and
the circulation of the fluids is brifk ; for a much
l'maller hole might have ferved this purpofe; and the
branches of the internal mammary veffels which are
fent to the external parts of the thorax , do not pafs
here, hut between the cartilages of the ribs, before
thefe are joined to the Jlernurn.

The cartilago xiphoides , is oftener bifurcated in
women than men, for the reafon afligned in the pre-
ceding paragraph, viz. a lefs forcible power of offifi-
cation.

The fuperior cartilages of the ribs fooner oflify, to
fupport the weight of the mamnue.

The middle cartilages are more flat and broad by
the weight of the breads.

The inferior cartilages arc longer, for enlarging
the cheft.

Weak

APPENDIX.

235

Weak women, who have born many children when
young, often have the vertebra of their back bended
forwards, and their Jlernum deprefled, or become
round-fhouldered and flat-breafted (a), by the pref-
fure and weight of the impregnared uterus , and by
the ftrong a&ion of the abdominal mufcles.

The os facrum is broader, and turned much more
backwards, for enlarging the pelvis.

The os coccygis is more moveable, and much lefs
bended forwards, to facilitate the birth.

The ojfa ilium are more hollow, and more reflect-
ed outwards, and confequently further removed from
each other, in order to widen the lower part of their
abdomen , and for the better fupport of the impreg-
nated uterus.

The ridge on the upper part of the os pubis , is
larger in fuch women as have born children, being
extended by the ftrong a£lion of the mufculi reEli ab-
dominis.

The cartilage between the two ojfa pubis , efpecially
in women who have born children, is thicker than
in men, by which the pelvis is more capacious in fe-
males.

The conjoined furfaces of the ojfa pubis , and of the
ojfa innominata and facrum are lefs, the angle under
the J'ymphyfts of the ojfa pubis, is much larger, and the
arches formed below and behind by the ojfa ilium and
ijchiutn are wider, which, with the ftraighter os Jacrumt
and more diftant tubera ifchii , leave a larger paflage
for the exclufion of the child in birth.

The great tuberofity of the ojfa ijchium , is flatter
in women than in men, becaul'e it is more prefied
upon in the fedentary life which females enjoy.

In confequence of the pelvis of women being wid-
er, the articulations of their thigh-bones muft be
farther removed from each other : and therefore a
larger fpace is left for the procreation and birth of
children (b) •, which diftance of the thighs, may be

one

(a) Chefclden’s Anatomy, book I, chap. 3.

(l>) Albin, dc <jlEb. § 339.

one reafon why women in running generally fhufHe
more from one fide to the other than men, to preferve
the centre of gravity of their bodies from falling too
far to a fide of the joint of the thigh that fuppotts
them when the other is raifed, which would en-
danger their tumbling to the ground.

t 237 3

INDEX.

A.

ACetabulum of ofla innominata, Ij8.

Analyfis, chemical, of bones, II. Phenomenon from it, 12.
Apophyfes, their different forts, ufes, 18, 19. Many fb named are
epiphyfes, 19.

Appendices, vid. Epiphyfes.

Arm-bone, vid. Humeri os.

Arthrodia, 31, ;3-

Articulations, 29. Symphylis, ibid. Synarthrofis, 30. Diartftffl^
fis, 30, 32. Difpute concerning them, 31.

Aftragalus, 221. Its articulation, 222. Of children, 228.

Atlas, or the firft vertebra of the neck, 133. Of infants, 134.

Axis, or third vertebra colli, 138.

B.

BOnes, what, 4. Their plates, ibid. Fibres, daviculi, 5. Can,-
celli, 6. Arteries, 7. Veins, 8. Nerves, ibid. Circulation
of their liquors, nourishment, increafe, decreafe, 9. Phenomena
and difeafes, 9, 10, 16, 26. Tranfverfe canals, 7, 10. Longitu-
dinal ones, 10. Analyfis, II. Phenomenon, ufes, 12. Perio-
fttum internum and marrow, ibid. Diftinguifhcd into broad and
round, 16. Strength increafed by being hollow, 17. Procefies,
18. Cavities, 19. Epiphyfes, 20. Oflification, 22. Phenome-
na, 26. Articulations, 29.

Breaft-bonc, vid. Sternum.

Bregma, 67.

Broad bones, their ftrufture, 16.

C.

CAlcis os, 223. Of children, 224.

Cancelli of bones, 6. Corrugati, cribriform es, reticulares,
ufes, ibid.

I Canini dentes, Il8.

I Carpus confifts of eight bones, 193. Its figure, fubrtance, articula-
tion, motions, 198. Ufes ; of infants, 199.

| Cartilages, what; their plates, fibres, 37. Vcffels, nerves, 37,38.
Olfification, how prevented, 38. Their ufes, difeafes, 39, 40.
Cavities of bones, their different kinds, 19. Uies, 20.

: Cervical vertebra:, their diftinguilhing marks, 131. Atlas, ibid.
Dentata, 134. Axis, 138. Seventh, ibid.

•beek-boncs, vid. Malarum olfc.

Clavicle"?*

238 INDEX.

Clavicles, 175. Internal end, ibid. Body, 176. External end,
medullary veflels, fubftance, articulation, ibid. Of children:
ufes, 177.

Claviculi of bones, perpendicular, oblique, headed, crooked, 5.
Coccygis os, 148. Its firft bone, ibid. Its 2d, 3d, 4th bones, 149,
150. Subfiance, motion, difeafes, ufes, 150, 151.

Collar-bone, vid. Clavicle.

Coronal future, 50.

Coflae, vid. Ribs.

Cranium, its figure, 47. Surfaces, 48. Tables, diploe, 49. Con-
fiftsof fix proper, 50. and two common bones, 79. Its futures, 50.
Cubitus, vid. Fore-arm.

Cuboides os, 225. At the birth, 226.

Cuneiforme os, of the wrift, 195.

Cuneiformia offa, of the foot, externum, 226. Medium internum,
ibid. At the birth, 227.

D.

DEntata, or ad vertebra of the neck, 134. Its diflinguilhing
marks, 13J. ; of infants, 136.

Dentes, vid. Teeth.

Diarthrofis, 30, 32. Its three fpecics, Enarthrofis, Arthrodia, Gin-
glimus, 31, 33.

Digit!, vid. Fingers and Toes.

Diploe of the Ikull, 49.

Dorfal vertebra, their diflinguilhing flrufture, I39. Wherein they
differ from each other, 140.

E.

ENarthrofis, 31, 33.

Epiphyfes, 19, 20. Several hare apophyfes, 20. Their ufes,
20, 21.

Ethmoidal future, 54.

Ethmoides os, its cribriform plate, 80. Nafal plate, ibid. Cellu-
le, ofla fpongiofa, 81. Connexion, ufes, 82. Morbid pheno-
mena ; of a child, 83.

Extremities inferior, confift, each, of thigh, 206. leg, 210. foot, 220.

fuperior, 174. confift, each, of fhoulder, 175. arm, 183.

fore-arm, 187. hand, 193. Ufes, 205.

F.

FAce, 90. Compofcd of upper jaw, ibid. Lower jaw, 108.

Female Ikeleton, diftinguifhing marks of it, 233.

Femoris os, 206. Its upper end, ibid. Body, 208. Lower end,
209. Of infants, its articulation and motions, 210.

Fibula, its upper end, 214. Body, ibid. Inferior end, 216. Its
articulation, ufes, 217. ; of infants, ibid.

Fingers, their bones, phalanges, 204. ill, ibid. 2d, 3d, 205. In»
dicis, of middle, annular, little finger, ibid.

Fontanelle,

INDEX.

23*

Fontanelle, 67.

Foot, com pofcd of tarfus, 220. -Metatarfus, 228. Toes, 230.. Its
motion, 222.

Fore-arm, 187. Confifts of ulna, ibid. Radios, TQO.

Frontal-bone, 57. Its external furface, procefies, cavities, ibid. Fo-
ramina, 58. Internal furface, 59. Foramen, 60. Subftance,
finufes, 6l. Connexion, 63. Ufes ; of children, 64.

G.

GInglimus, its fpecies, 3T, 33.

Gomphofis, 30.

H.

HAnd, 193. Confifts of carpus, ibid. Metacarpus, 199. Fingers,
202.

Harmonia, 30.

Haunch-bones, vid. Ilium ofla.

Head, confifts of cranium, 47. Face, 90. Its motion, 136.
Heel-bone, vid. Calcis os.

Hip-bone, vid. Os Ifehium.

Humeri os, 183. Its upper end, ibid. Body, 184. Lower end,
ibid. Subftance, articulation, 186. Motion, ibid. Of children,
187.

Hyoidesos, 122. Its body, ibid. Cornua, 123. Appendices, ibid.
Ligaments, fubftance, connection, ufes; of children, 124.

I.

JAw, lower, vid. Maxilla inferior.

upper, vid. Maxilla fuperior.

Ilium ofta, 131. Spine, dorfum, ibid. External furface, 15a. In-
terior furface, 153. Medullary veflels, fubftance; of a child, 134.
Inciiores dentes, 117.

Innominata ofla, 131. Coinpofcd of os ilium, ibid. Ifehium, 134*
Pubis, 154. Their great foramen, 157. Acetabulum, 158. In
infants, 131, 159. Connection, ibid. Phenomena, ibid. Uics,
160.

Ifehium os, 154. Procefs, depreflions, tuber, 133. Subftance, 136.
Of infants, ibid.

L.

IAmbdoid future, 30. Its additamenta, ibid.

Lattice-work of bones, vid. Cancelli.

Leg, compofed of tibia, 210. Fibula, 214. Rotula, 217. Its arti-
culation and motions, 2x8.

Ligaments, 33. Their fibres, veflels, nerves, difeafes, 3 3, 36. Ufes,
phenomena, 36.

Lumbar vertebra;, their particular ftruCture, 14a. Differences, 143.
Lunareos, 194.

Magnum

240

INDEX.

' • ^ M.

> ^Agmim os, of the wrift, 196.

JY1 Mala rum ofla, their procefles, 95. Holes, fubftance, connec-
tion, 96. Of infants, ibid.

Marrow, what, 13. Its chemical analyfis, its arteries, veins, nerves,
ibid. Difeafes., 14. Tranfverfe and longitudinal canals for con-
veying it, 10, Ij. Ufes, ij. Phasnomena and difeafes, 14, 16.

Maxilla inferior, 108. The chin, fidcs, bafe, 109. Phenomena,
angles, procefles, no. Foramina, fubftance, no, III. Articu-
lation, III. Motions, III. Of infants, ufes, 113.

. fuperior, confifts of 13 bones, 91. Their connexion, ibid.

Maxillaria ofla, their procefles, 97. Cavities, 98. Foramina, 99.
Sinufes, 100. Morbid phenomena, ibid. Subfiance, connexion,
101. Ufes; of children, IOI.

Metacarpus, compofed of four bones, 199. Subftance, at the birth,
articulation, 200. Figure, ufes, digiti indicis, aoi. Medii, ibid.
Annularis, minimi, 202.

Metatarfus, compofed of five bones, ll8. l’ollicis, I ft, ibid, id, 3d,
4th, 129. Digiti, 230.

Molares dentes, 117, 118.

Mucilaginous glands, 40. Liquor fecreted by them, ibid. Their
cellular fubftance, vcflels, nerves, difeafes, 41. Ufes, 42, Pheno-
mena, ibid.

N.

NAfi ofla, their fides, 93. Connection, ufes ; of an infant, 94#
Naviculare os, of the tarfus, 224. Of children, 225.

Heck, vid. Ccrvicle vertebrae.

O.

OCcipitis os, 73. Its external furface, 74. Procefles, ibid. In-
ternal furface, 76. Holes, 77. Subftance, 78. Connexion,
ibid. Ufes, in infants, 79.

Ofli Station of bones, 22. Accounted for from particular difpofition
of veflels, and from prefliire, 23. Phenomena, 22, 26. Its hi-
ftory, 27.

Ofteogcnea, its hiftory, 27. Of what ufe, 28.

P.

PAlati os, 102. Its fquare palate-plate, ibid. Pterygoid proeefs,
natal lamella, 103. Orbitar proeefs, 104. Subftance, connec-
tion, ufes, 105. Of children ; difeafes, ibid.

Parietal bones, their external furface, 64. Internal furface, 65. k
Subftance, ibid. Connexion, ufes; of children, 66. Practical ■
obfervations concerning bregma, 67.

Patella, vid. Rotula. _

Pelvis, 151, 160. Confifts of os facrum, 144. Coccygis, 148. Ofla
inmomiaata, 151, :

PcrichondriuiUj

INDEX.

241

Perichondrium, its veflels, 37.

Periofteum externum, x. Its fibres, ibid. Arteries, veins, nerves,
a, 3. Ufcs, 3. Difeafes, 4.

internum, its ftructure, ules, 12, 13.

Phalanges of the fingers, 204.

■ toes, 230.

Pififorme os of the wrift, 195.

Plates of bones, their fibres, 4.

Pollicis manus ofla, vid. Thumb.

pedis offa, vid. Toes.

Pores tranfverfe and longitudinal of bones, 7, io. Their ufcs, Ij.
ProcefTcs of bones, vid. Apophyfes.

Pubis os, 156. Subftance; of children, 157.

R.

RAdius, its upper end, 190. Body, ibid. Lower end,. I9X. Of
children, articulation, 192.

Ribs, 161. Their middle, pofterior end, 162. Anterior end, fiib-
ftance, cartilages, 163. Articulation and motion, 164. Differ
from each other, ibid. Diftinguilhed into true and falfe, 16 r.
Diftinguilhing marks of ift, 2d, 3d, 4th, 5th, 6th, 7th, nth, 12th,
167. Of infants, 168/ Motion, 168, 1 73.

Rotula deferibed, 217. Its fubftance, 218. Articulation; of chil-
dren, ibid.

Round bones, their ftrufhire, 16. Strength how incrcafed, 17.

S.

SAcrum os, its body, 144. Procefles, oblique, tranfvcr/c, 145’.
Spinal, 146. Foramina, ibid. Subftance, articulation 147.
Ules; of children, 148.

Sagittal future, 51.

Scaphoid bone of the wrift, 194.

Scapula, 177. Its bale, inferior cofta, 178. Superior cofta, dorfum,
anterior furface, 179. Procefles, fpinc, acromion, coracoid pre^
cefs, 180. Third procefs, medullary vellcls, 181. Subftance,
articulation, ibid. Ufes; of children, 183.

Schyndelefis, 30. _

Sefamoid bones, how formed, 231. Where to be found, ibid.

} Share-bone, vid. Olla Pubis.

Shoulder, confifts of clavicle, 175. and fcapula, 177!

Shoulder-blade, vid. Scapula.

Sinus frontales, 61. Sphenoidal, 88. Maxillary, too.

Skeleton, natural, artificial, 45. Situation of the bones, 46. Divid-
ed into Head, 47. Trunk, 124. Extremities, fuperior, 174. Infe-
rior, 206.

— — - — of a female, its differences from that of the male,

Skull, vid. Cranium.

Sphenoid bone, 83. Its external lurface, procefles, ibid. Cavities
85. Internal furface, 86. Holes proper, ibid. Common, 88*
Smufes, ibid. Subftance, connexion, 89. Ules ; of children, 90*.

^ Sphenoidal

24*2

INDEX.

Sphenoidal future, 54.

Spine, its fhape, 124. Confifts of true vertebrae, 125. and falfe, 144.
Spongiofa inferiors oda, ioj. Their fubftance connexion, ufes; of
children, X06.

Squamous futures, 52. How formed, 53.

Sternum, 169. Its fubftance, ibid. Firft bone, 170. SeconcJ.bone,
171. Xiphoid cartilage, ibid. Difeafes, 172. Connexion; of
children, ibid. Ufes, motion, 173.

Suture, 30. How formed, ibid.

of the cranium, 50. Coronal, lambdoid, ibid. Sagittal,

51. Squamous, 32. Ethmoidal, fphenoidal, tranfverfe, zygoma-
tic, 54. Ufes, 55.

of the face diftinguilhed by names, 91. Ufes, 93.

Symphyfis, divided into fynchondrofis, fyneurofis, fydarcofis, 29.

Synarthrofts, divided into future, harmonia, gomphofis, fchyndclcfis.

Synchondrofis, 29.

Syneurofis, 30.

Synovia of joints, what compofed of, 41. Its ufes, difeafes, 42.
Syffarcofis, 30.

Arfus confifts of feven bones, 220. Its articulation, 222. Ufes,

ibid. 227.

Teeth, 1x3. Their bafe, roots, periofteum, fubftance, 114. Ca-
nals, 1 15. Veftels, ibid. Formation, 1 16. Shedding, ibid. Con-
nexion, ufes, 117. Diftinguilhed into incifores, ibid! Canini, mo-
lares, 1x8. Pha-nomena, 120, ire.

Temporal bones, 67. Their external furface, precedes, 68. Cavi-
ties, 69, 73. Holes, 70. Internal furlace, 71. Precedes, cavities,
holes, 72. Subftance, ibid. Connexion, 73. Ufes; of infants,
ibid.

Thigh-bone, vid. Femoris os.

Thorax, 160. Confifts of vertebrae, 139. Ribs, 161. Sternum,
169. Us motion, 173.

Thumb confifts of three bones ; the firft, its articulation, 202. At
the time of birth, 203. Second bone, its articulation, ibid. Third
bone, 204.

Tibia, its upper end, cartilages, *11. Body, 212. Lower end, 213*
Articulation ; of children, 2 1 4.

Toes, 230. differ from the fingers, ufes, ibid. Of children, 231s

Tranfverfe future, 54.

Trapezium os, 196.

Trapezoides os, ibid.

Triquetra oda, 51.

Trochoides Ginglimus, 33.

Trunk of the Ikeleton confifts of the fplne, 134. Pehris, IJI, 10O.
Thorax, ibid.

Turbinata ofla, vid. Spongiofa,

fuperiora oda, 81.

T.

Ulna,

I N- D E

X.

243

u.

ULna, its upper end, 187. Body, 189. Lower end, ibid. Ar-
ticulation, 190. Of children, 192.

Unciforme os of the wrift, 197.

Unguis ofla, their furfaces, 94. Subftance, connection, ules, 9 j.
Morbid Phamomcna ; of children, ibid.

V.

VErtebrae cervical, vid. Cervical.

— dorfal, vid. Dorfal.

— ■■ — falle, compofed of os facrum, 144. Coccygis, 148.

— lumbar, vid. Lumbar.

true, their bodies, cartilages, 125. Procefles, ligaments,

foramina, X27. Articulations, phaenomena, 128. Of
infants, 129. Difeafes, 130. Divided into cervical,
I31. dorfal, 139. lumbar, 142. Ufcs, fecurcd from
luxations, 143, 144.

Veflels of periofteum, 2. Of the bones, 7. Of the marrow, 13. Of
ligaments, 35. Cartilages, 37. Mucilaginous glands, 40.

Vomer, 106. Its figure, fituation, I07. Subflance, connexion, ufes,
108.

W.

V\70men, the differences of their bones from thole of men, J.

’ Wormiana ofla, vid. Triquetra.

Wrift, vid. Carpus.

X.

^Iphoid cartilage, 171. Its difeafes, 17*.

Z.

ZYgoma, 68.

Zygomatic future, 54.

X »

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HUMAN NERVES,

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A Description of the HUMAN
LACTEAL SAC and DUCT.

The Tenth Edition.

My Alexander Monro Senior , M. D. and P. A.

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PREFACE

To the Seventh Edition.

BEING informed that the following Effay*
have been ufeful to the ftudents in anato-
my, I have caufed them to be reprinted, with
fiuch amendments as I thought neceflary.

That offence might not be given, I have
treated all the opinions concerning the dis-
puted phyfiology of the nerves with that de-
ference which the uncertainty of the fub-
jett required ; and have not only concealed the
names of the writers whofe fentiments were
different from mine, but have Ihunned quota-
tions from thofe whom I approve, left the
knowledge of the latter fltould be a key to dis-
cover the former by.

Defcriptions of the very minute ramifications of
the nerves are obfeure to the young gentlemen
for whofe ufe I write ; and therefore I have
taken notice only of the larger branches in the
defeription of the particular nerves.

The firft occafion of my publiftiing my great
Mafter Boerhaave’s do&rinc concerning the
Syftole and Diaftole of the heart, was to pre-
vent the imputation I might have lain under of
affuming it to myfelf, when my worthy Mafter
and good friend Mr. Chefelden inferted it into
his anatomy, as communicated by me, without

mentioning

PREFACE. „

248

mentioning Boerliaave’s name. Having now
taken away all grounds of fuch imputation, and
the doCtrine, though fimple and beautiful, not
appearing fufficient to account for the pheno-
mena of the motions of the heart, I have omit-
ted it in this edition.

The defcription of the receptaculum chyli
and thoracic duCt is more accurate, than in the
common fyflems of anatomy j and on that ac-
count is here republilhed.

The corrections and additions made in this
edition of the anatomy of the bones, and of
thefe Eflays, fltow, that I pretend not to Per-
fection ; but I would however wifli, that no
more faults were imputed to me than what are
really my own.

THE

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4

THE

ANATOMY

OF THE

HUMAN NERVES.

Of the Nerves in general.

I. r Ij "1HE numerous turns which the carotid and
[i vertebral arteries make before they pafs
through the dura mater , thefe arteries hav-
ing neither fwelling mufcles nor preflure of the at-
mofphere to aflift the courfe of the blood in them
after they enter the fcitll, and their divifion into innu-
merable communicating branches in the pia mater , and
its procefl'es, fliew, that the liquors mull move more
fiowly and equally in them than in mod other parts
of the body.

2. By the afliftance of injections and microfcopes,
the very minute branches of thefe veflels (§ i.) are
difcovered to go from the pia mater into the cortex ,
cineritious, or afhy-coloured part of the cerebrumy
cerebellum , and fpinal marrow ; whereas we can only
fee longitudinal veflels, without numerous ramifica-
tions or reticular plexufes, in the white medullary
fubflance of thefe parts.

3. The continuity of the cortex with the medulla of
the encephalon and fpinal marrow is obfervable with
the naked eye, and is more diltindUy feen with the
afiiftance of a microfcope.

4. Itt

250 Of the NERVES 1N GENERAL.

4. In difle£fing the brain and cerebellum , we fee
the fmall beginnings of the medulla proceeding from
the cortex, and can trace its gradual increafe by the
addition of more fuch white fubftance coming from
the cortex.

5. Both thefe fubftances (§ 4.) are very fucculent;
for, being expofed to the air to dry, they lofe more of
their weight than mod other parts of the body do.

6. In feveral places we can obferve the medulla to
be compofed of fibres laid at each others fides.

-»■ 7. The medullary fubftance is employed in form-

ing the white fibrous cords, which have now the name
of nerves appropriated to them. Within the fcull we
fee the nerves to be the medullary fubftance continued ;
and the fpinal marrow is all employed in forming
nerves.

8. The common opinion concerning the rife of the
nerves, founded on a fuperficial infpe&ion of thofe
parts, is, that the nerves are propagated from that
fide of the encephalon , at which they go out of the
fcull. But it having been remarked, after a more
ftricl inquiry, and preparing the parts by maceration
in water, that the medullary fibres decufiate or croft
each other in fome parts of the medulla j as for ex-
ample, at the corpus annulare, and beginning of the
fpinal marrow : And practical oblervators having re-
lated feveral examples of people whofe brain was hurt
on one fide, while the morbid fymptom, palfy, ap-
peared on the other fide of the body, of which I
have feen fome inftanccs ; and experiments made on
brutes having confirmed thefe obfervations, it has been
thought, that the nerves had their rife from that fide
of the encephalon, which is oppofite to their egrefs
from the fcull. It may however ftill be faid, that
this laft opinion is not fully demonftrated, becaufe a
decuflation in fome parts is not a proof that it obtains
univerfally j and if there are examples of palfy of
the fide oppofite to where the lefion of the brain was,
there are alfo others, where the injury done to the
brain and the paify wfere both on the fame fide.

9. The

Of the NERVES in GENERAL. 251

9. The nerves are compofed of a great many
threads lying parallel to each other, or nearly fo, at
their exit from the medulla.

This fibrous texture is evident at the origin of mod
of the nerves within the fcull ; and in the cauda equi-
na of the fpinal marrow , we can divide them into
fuch fmall threads, that a very good eye can fcarce
perceive them •, but thefe threads, when looked at
with a microfcope, appear each to be compofed of a
great number of fmaller threads.

ro. How fmall one of thefe fibrils of the nerves
is, we know not; but when we confider that every,
even the moll minute part of the body is fenfible, and
that this mud depend on the nerves (which all con-
joined, would not make a cord of an inch diameter)
being divided into branches or filaments to be dif-
perfed through all thefe minute parts, we mull be
convinced that the nervous fibrils are very fmall.
From the examination of the minimum vi[ibiley it is
demonftrated, that each fibre in the retina of the eye
or expanded optic nerve, cannot exceed the fize of
the 32,400 part of a hair.

11. The medullary fubftance, of which the ner-
vous fibrils are compofed, is very tender, and would
not be able to refill: fu,ch forces as the nerves are ex-
pofed to within the bones, nor even the common
force of the circulating fluids, were not the pia mater ,
and tunica arachnoides continued upon them \ the for-
mer giving them firmnefs and ftrength, and the lat-
ter furnifliing a cellular coat to connect the threads
of the nerves, to let them lie foft and moift, and to
fupport the vefiels which go with them.

It is this cellular fubftance that is diftended when
air is forced through a blow-pipe thruft into a nerve,
and that makes a nerve appear all fpongy, after being
diftended with air till it dries ; the proper nervous
fibrils fhrivelling fo in drying, that they fcarce can
be obferved.

12. Thefe coats (§ 11.) would not make the nerves
Rrong enough to bear the ftretching and preflure they

are

Of the NERVES in GENERAL.

are expofed to in their courfe to the different parts of
the body ; and therefore, where the nerves go out at
the holes in the cranium and [pine,- the dura mater is
generally wrapt clofely round them, to collett their
difgregated fibres into tight firm cords; and, that the
tenfion which they may happen to be expofed to, may
not injure them before they have got this additional
coat, it is firmly fixed to the fides of the holes in the
bones through which they pafs.

13. The nervous cords thus compofed of nervous
fibrils, cellular coat, pia and dura mater, have fuch
numerous blood-veffels, that after their arteries only
are inje&ed, the whole cord is tinged of the colour
of the injefled liquor; and if the inje£tion is pufhed
violently, the cellular fubftance of the nerves is at
laft diftended with it.

14. A nervous cord, fuch as has been juft now de-
feribed, (§ 13.), has very little elafticity, compared
■with feveral other parts of the body. When cut out
of the body, it does not become obferveably fhorter,
while the blood-veffels contract three eighths of their
length.

15. Nerves are generally lodged in a cellular or
fatty fubftance, and have their couife in the interfti-
ces of mufclcs, and other a£tive organs, where they
are guarded from preffure ; but in feveral parts they
are fo placed, as if it was intended that they fhould
there fuffer the vibrating force of arteries, or the
preffure of the contracting fibres of mufcles.

16. The larger cords of the nerves divide into
branches as they go off to the different parts; the
branches being fmaller than the trunk from which
they come, and making generally an acute angle
■where they feparate.

1 7. In feveral places, different nerves unite into one
cord, which is commonly larger than any of the
nerves which form it.

18. Several nerves, particularly thofe which are
diftributed to the bowels, after fuch union, (§ 17.),
fuddenly form a hard knot confiderably larger than

all

2$3

Of the NER\ES in GENERAL.

"all the nerves of which it is made. Thefe knots were
called corpora olivaria , and are now generally named.
ganglions.

j ;j. The ganglions have thicker coats, more nume-
rous, and larger blood- vefltls than the nerves ; fo that
they appear more red and mufcular. On diflecling the
ganglions , fibres are feen running longitudinally in
‘theit axes, and other fibres are derived from their
tides in an oblique direction to the longitudinal ones.

20- Commonly numerous fmall nerves, which con-
jundly are not equal to the fize of the ganglion, are
lent out from it, but with a ftrudure no way dif-
ferent fiom that of other nerves.

21. The nerves fent to the organs of the fenfes,
Jofe there their firm coats, and terminate in a pulpy
fubftance. rl he optic nerves are expanded into the
foft tender webs, the retina. I he auditory nerve has
fcarce the confidence of mucus in the vejlibulum , coch-
lea, and femicircular canals of each ear. I he papilla
of the nolle, tounge, and fkin, arc very foft.

22. The nerves of mufcles can likeways be traced
till they feem to lofe their coats by becoming very
foft •, from which, and what we obferved of the fen-
iatory nerves (§ 21.), there is reafon to conclude, that
the mufcular nerves are alfo pulpy at their termina-
tions, which we cannot indeed profecute by diffedion.

23. It would feem neceflary that the extremities of
the nerves fhould continue in this foft flexible date,
(§21. 22.), in order to perform their fundions right:
Tor, in proportion as parts become rigid and firm by
age, or any other caufe, they lofe of their fenfibility,
*md the motions are more difficultly performed.

24. Though the fibres in a nervous cord are firm-
ly conneded, anti frequently different nerves join in-
to one trunk, or into the fame ganglion ; yet the fen-
fation of each part of the body is fo very diflind,
and we have fo much the power of moving the muf-
cles feparately, that, if the nerves are principal a-
gents in thefe two fundions, which 1 (hall endeavour
to prove they are, we have reafon to believe that there

254 Of the NERVES in GENERAL.

is no union, confufion, or immediate communication
of the proper nervous fibrils, but that each fibre re-
mains diftinft from its oiigin to its termination.

25. Changes produced any way upon the coats of
the nerves, cannot however mifs to'affe£l the nervous
fibrils. The cellular fubfiance may be too full of li-
quor, or may not fupply enough ; the liquor may not
be of a due confiftence, or it may be preternaturally
obftru£ted and colle£led. The pi a 01 dura mater %
may be too tenfe, or too lax ; their veflels may be ob-
ftru£ted ; their proper nerves may be violently irritat-
ed, or lofe their power of adding; and a great many
other fuch changes may happen, which will not only
occafion diforders in particular nerves, but may be a
caufe of the fympathy fo frequently obferved among
the nerves ; which is fo necefiary to be attentively re-
garded in a great many difeafes, in order to difeover
their true ftate and nature, that, without this know-
ledge, very dangerous mi (lakes in the practice of
phyfic and furgery may be committed.

26. Many experiments and obfervations concur in
proving, that when nerves are comprefled, cut, or
any other way deftroyed, the parts ferved by fuch
nerves, farther from the head or fpine than where the
injuring caufe has been applied, have their fenfations,
motions, and nourifhment weakened or loft, while no
fuch eftefts are feen in the parts nearer to the origin
of thofe nerves ; and in fuch experiments where the
caufe impeding the nerves to exert themfelves could
be removed, and the ftruddure of the nerves not in-
jured, as for example, when a ligature made upon a
nerve, and (topping its influence, has been taken away,
the motion and fenfation of the parts foon were re-
ftored. From which it would appear, that the nerves
are principal inftruments in our fenfations, motions,
and nouriftiment; and that this influence of the
nerves is not inherent in them, without the com-
munication between thefe cords and their origin is
preferved.

Of THE NERVES in GENERAL. 255

This conclufion is juft, notwithftanding that fome-
'times, upon cutting a nerve, the effedts above men-
tioned have been felt for a fhort time ; but afterwards
the perfon was fenfible of no numbnefs or immobili-
ty ; for where-ever this is faid to have happened, the
cut nerve was only one of feveral which were fent to
the member; the want of whofe influence was felt
no longer, than till the habit was acquired of per-
forming the fundlions eafily by the other nerves.

Nor is it of greater weight as an objection, that
fometimes when a ligature is drawn very hard upon
a nerve, and then is taken away, the nerve never a-
gain recovers its influence upon the parts it is diflribut-
ed to beyond the ligature, but is of as little effedt as
if it had been cut through ; which is to fay, that itsf
texture has been altered beyond recovery. The fame
thing is to be feen by tying a thread tight round a.
tender twig of any vegetable ; it decays.

27. Experiments and obfervations fhew too, that
when parts of the encephalon or fpinal marrow have
been irritated, comprcfled, or deftroyed, the parts of
the body, whofe nerves had their origin from fuch
afledted parts of the encephalon or fpinal marrow , be-
come convulfed, paralytic, infenfible, or wafted ; and
in fuch cafes where the injuring caule could be re-
moved from the origin of the nerves, the morbid
fymptoms obferved in the parts to which thefe nerves
were diftributed, went off upon the removal of that
eaufe. From which it is thought reafonable to con-
clude, that the nerves mull not only have a com-
munication with their origin, but that the influence
they have upon the parts they are diftributed to, de-
pends on the influence which they deiive from the
medulla enccphali and fpinalis.

28. 1 hough the fpinal marrow has its own veffels
and cineritious fubltance which aflifts to form its me-
dulla; yet .a very large (hare of the medullary fub-
ftance within the fpine is derived from the encephalon ,
whofe medulla oblongata defeends from the head, and
the influence of the fpinal marrow on its nerves de-

^ 2 pends

2 S6 Or THE NERVES IN GENERAL.

pends in a great meafure on this medulla oblongata of
the head. Hence an injury done to any part of the
Spinal marrow , immediately affetts all the parts whole
nerves have i heir origin below where the injuring
caufe is applied. A luxation of a vertebra in the loins
makes the lower extremities foon paralytic; a tranf-
verfe feclion of the medulla at the fir It vertebra of the
neck, foon puts an end to life.

29. If fuch caufes produce conftant'iy fuch effects
(§ 26. 27. 28 ) in us and other creatures living in
nearly the fame circumftances as we do, the conclu-
fions already made muft be good, notwithftanding
examples of children and other creatures being born
without brains or Jpinal marrow ; or notwithftanding
that the brains of adult creatures can be much chan-
ged in their texture by difeales ; and that tortoifes, and
feme other animals, continue to move a confiderable
time after their heads are cut off’. We may be igno-
rant of the particular circumftances requifite or ne-
ccffary to the being or well-being of this or that par-
ticular creature, and we may be unable to account
for a great many phenomena ; but we muft believe
our eyes in the examination of fa£ts ; and if we fee
eonftantly fuch confequences from fuch actions, we
cannot but conclude the one to be the caufe, and the
other the effect. It would be as unjuft to deny the
conclufions made in the three preceding articles, be-
caufe of the fcemingly preternatural phenomena,
mentioned at the beginning of this, as it would be
to deny the neceflity of the circulation of the blood
in us and mod quadrupeds, becaufe a frog can jump
about, or a tortoife can walk long after all the bowels
of its thorax and abdomen are taken out, or becaufe
the different parts of a worm crawl after it has been
cut into a great many pieces. It is therefore aJmoft
univerfally allowed, that the nerves are principal in-
ftruments in our fenfations, motion, and nourifh-
ment ; and that the influence which they have is com-
munic ted from their oiigin, the encephalon and me-
dulla Spinalis. Hut authors are far from agreeing a-
1 bout

Of THE NERVES in GENERAL.

/

bout the manner in which this influence is communi-
cated, or in what -way nerves aCt to produce thefe
effects.

30. Some alledge, that the nervous fibres are all fo~
lid cords acting by elafiicity or vibration ; others main-
tain, that thofe fibres are fmall pipes conveying liquors ,
by means of which their effects are produced.

3 1. The gentlemen, who think the nervous fibres
felid, raife feveral objections to the other doctrine ;
which 1 fhall confide r afterwards ; and endeavour to
to {hew the fitnefs of their own doCtrine to account
for the effects commonly obferved to be produced by
the nerves.

The objeCts of the fenfes plainly (fay they) make
impulfes on the nerves of the proper organs, which
mull {hake the nervous fibrils : and this vibration mull
be propagated along the whole cord to its other extre-
mity or origin •, as happens in other tenfe firings ;
and thefe vibrations being differently modified, ac-
cording to the difference of the objeCt, and its diffe-
rent application, produce the different ideas we have
of objects.

32. To this account of fenfation, it is ebjeCted,
ficjly 'That nerves are ur.fi t for vibrations, becaufe
their extremities, where objoCts arc applied ro them,
are quite foft and pappy (^21.), and theiefore not
fufceptible of the vibrations fuppofed ; and if there
could be any little tremor made here by the impulfe
of objeCts, it could not be continued along the ner-
vous cord, becaufe the cellular fubfiance by which
each particular fibre is connected to the neighbouring
ones (§ 11.), and the fatty fubfiance in which the
nervous cord is immerfed (§ 15-), would foon flifle
any fuch vibratory motion.

A fecond objeCtion to this doCtrine is, that fuppcf-
ing the nerves capable of vibrations by the iinprellions
of objeCts, thefe vibrations would not anfwer the de-
fign. For if what we know of other vibrating firings,
to wit, that their tone remains the fame, unlefs their
texture, length, or tenfion is altered, and that diifc-

Y 3 rent

25 3 Of THE NERVES in GENERAL.

rent fubftances finking them do no more than make
the found higher or lower ; if thefe properties are to
be applied to nerves, then it will follow, that the
fame nerve would conftantly convey the fame idea,
with no other variety than of its being weaker and
ftronger, whatever different objects were applied to
it; unlefs we fuppofed the nerve changed in its tex-
ture, length, or tenlion, each time a different object
is applied; which, it is prefumed, no body will un-
dertake to prove does happen.

Nav, 3 d/y, If ever fuch a variety of vibrations
could be made, our fenfations would notwithftanding
be confufed and indiftinCt, becaufe the tremulous
Nervous fibre being firmly connected and contiguous
to feveral other fibres of the fame cord, would necef-
farily ibake them too, by which we fhould have the
notion of the objeCt as applied at all the different
parts where the extremities of thefe fibres terminate.

33. In whatever way the favourers of the doCtrine
of folid nerves pleafe to apply the elafticity of nerves
to the contraction of mufcles, their adverfaries in-
fill that nerves are too weak to refift fuch weights as
the mufcles fuflain ; they would furely break, efpe-
cialiy as they are in a great meafure, if not wholly,
deprived of their ftrong coats before they come to
the part of the inulcle they are immediately to act
upon (§ 22.) — The nerves being found to have little
or no elafticity to fiiorten themfelves (§ 14.), fiiews
them altogether unfit for fuch an office as this of con-
tracting mufcles in the way propofed of their aCting
by elafticity ; and when a nerve is viewed with a mi-
crofcope while the mufcles it ferves are in aCtion, no
contraction or motion is obferved in it. — Nay, if they
were elaftic, they would equally exert their power of
contracting mufcles nearer to their origin as well as
farther from it, when they were put into contraction
or vibration, by irritation of any part of them. The
former however does not happen.

34. As a farther objection againft either motion
or fenfation being owing to the elafticity of the nerves,

it

Of the NERVES in GENERAL. 25^

ir is faid, that if this d'oClrine was true, the fenfa-
tions would be more acute, and the contractions of
mufcles would be greater and dronger, when the parts
become firmer and more rigid by age ; for then their
elaflicit y is increafed : Whereas, on the contrary, it
appears (§ 23.) that then the fenfations are blunted,
and mufcular contraction becomes lefs and weaker.

35. If the nerves were granted to be eladic, and
to communicate a fpringy force to all the parts they
are diltri buted to, they might appear neceflary in this
view to aflift the application of the nutritious parti-
cles of the fluids to the fides of.the veflels which thefe
particles were to repair; andfo far might well enough
account for the fhare which nerves are thought to
have in nutrition : But if we cannot make ufe of e-
ladicity in the other two functions, fenfation and mo-
tion, we mult alfo endeavour to find out fome other
wav for the nerves to aCt in nutrition; which will
be done afterwards.

36. Having thus dated the reafons for and againft
the nerves aCting as folid firings, let us likewife re-
late the arguments for nerves being pipes, and the
objeClions to this doCtrine.

A great argument of thofe who think the nerves to
be tubes conveying liquors, is the flrong analogy of the
brain and nerves to other glands of the body and their
excretoiics, where a manifed fecretion of liquor is
made in the glands, to be conveyed by the excreto-
ries to the proper places in which it ought to be de-
pofited : They think that the vafcular texture of the
cortex of the encephalon and fpinal marrow (§ 2.), the
continuation of the cortex in forming the medullary
fubflance (§ 3. 4.), the fibrous texture (§ 6.), and
fucculent date of this m Mia (§ 5.), and its being
wholly employed to form the nerves (§ 7.), where the
fibrous texture is evident (§ 9.) ; all thefe things, fay
they, confpire to (hew fuch a flrong analogy between
thefe parts and the other glands of the body, as car-
ries a conviction that there is a liquor fecreted in the

encephalon

Of the NERVES in GENERAL.

260

encephalon and fpinal marrow , to be fent out by the
nerves to the different parts of the body.

37. The following objections are railed to this ar-
gument in favour of liquor conveyed in the nerves,
from the analogy of the glands. 1 ft, Other glands,
it is faid, have their excretories collected into a few
large pipes, and not continued in fuch a great num-
ber of feparate pipes, as far as the places where the
liquors are depofited ; which laft mud be the cafe, if
the nerves are the excretories of the glandular brain.
'idly, We fee the cavities, and can examine the li-
quors in the excretories of other glands much fmallcr
than the brain ; which cannot be done in the nerves.
ydly, If the nerves were pipes, they would be lo
frnall, that the attraction of the liquors to their tides,
would prevent that celerity in the motion of the li-
quors, which is requilite to fer.fations and motions.
4 tkly, If the nerves weie pipes, they would be cylin-
drical ones, and confequently not fubjeCt to difeafes ;
or at leaf!: we could have no comprehenfion of the
difeafes in them.

38. The anfwer to the \Jl of thefe objections is,
That there are other glands where there is a ma-
nifetl fecretion, and in which the difpofition of the
excretories is in much the fame way as is in the ence-
phalon : The kidneys, for example, have a reticulated
cortex of veffels, from which the Eujlachian or Belli-
nian medulla , confiding, of longitudinal fibres and a
few blood-vefl'els in the fame direction, pioceeds \
and this medulla is collected into ten, twelve, or more
pap'illee , each of which is formed of numerous frnall
feparate pipes, which fingly difeharge the urine into
the large membranous tubes; and thefe united form
the pelvis. Upon comparing this texture of the kid-
neys with that of the encephalon (§ 2. 3. 4. 5. 6. 7. 9.)
the analogy will be found very flrong.

39. In anfwer to the id objection, in § 37. it is
granted, that microfcopes, injections, and all the o-
ther arts hitherto employed, have not fheun the ca-
vities of the nervous fibrils, or the liquors contained

in

Of the NERVES in GENERAL. 261

in them ; and from what was faid (§ 10.) of the
fmallnefs of the nervous fibrils, it is not to be expect-
ed that ever they fhould be feen. But fo long as fuch
a number of little animals can every hour be brought
to the objectors, in which they can as little demon-
ftrate the veflels or contained fluids, it will not be
allowed to be conclufive reafoning, that becaufe ocu-
lar demonfti ation cannot be given of either the tubes
or their contents, therefore they do not exift. For
if we have any notion of an animal, it is its being an
hydraulic machine, which has liquors moving in it
as long as it has life j if therefore fuch little animals
have veflels and liquors which we cannot fee, why
may not fome of the veflels and liquors of the hu-
man body be alfo invifible to us ?

To avoid this anfwer to the obje&ion, it is further
urged, That though we might not fee the nervous
tubes or the liquors they contain, as they naturally
flow ; yet if fuch liquors really exift, they ought to
difeover themfelves, either by a nerve’s fwelling when
it is firmly tied ; or that, however fubtile their fluids
are, they might be colledted in fome drops, at leaft,
when the cut end of a nerve of a living animal is
kept lome time in the exhaufted receiver of an air-
pump. It is affirmed, that neither did the tied nerve
l’well between the brain and ligature, nor was there
any liquor colle£led in the receiver of the air-pump ;
from which it is concluded, that there is no liquor in
the nerves.

Some, who fay they have tried thefe experiments,
affirm, that, in young animals, the nerve does fwell
above the ligature, and that a liquor does drill out

upon cutting a nerve. Whether fwelling or liquor

is feen or is not feen in thefe experiments, no con-
clufion for or againft a nervous fluid can be made
Item them ; for the fwelling of the nerve after it is
tied, or the tfl’ux of liquors from its extremity, will
never prove either to be the tfreft of the fluid, in the
proper nervou: id rile, io long as they n ight Le cc-
t'i'.hcned by the liquors in the larger veflels of the

, cellular

262 Of THE NERVES in GENERAL.

cellular fubftance of the nerves; and if thefe fame
veflels of the coats of the nerves do not difcover their
liquors by thefe experiments, it is far lefs to be ex-
pected, that the much more fubtile nerves will dif-
cover theirs.

40. The 3 d objection to the doCtrine of the brain
being a gland, and the nerves its excretories, fup-
pofes a more rapid motion neceflary in the fluid of
the nerves, than what mod of the defenders of the
nervous fluid will now allow; and is afterwards to be
confidered particularly in a more proper place.

41. The t\th objection being, That if nerves are
excretories of a gland, they muft be cylindrical pipes,
in which no obftruCtions or difeafes would happen;
but fince we daily fee difeafes in the nerves, they
muft therefore not be fuch excretories. The anfwer
is, That difeafes happen often in the excretories of
other glands, as of the liver, kidneys, £s*r. notwith-
ftanding their cylindrical form, and their much
fhorter and lefs expofed courfe. When we confider
the very tender fubftance of the brain, the vaft com-
plication of veflels there, the prodigious fmallnefs of
the pipes going out from it, the many moving pow-
ers which the nerves are to undergo the fhock of, and
the many chances which the veflels, membranes, and
cellular fubftance accompanying the nerves have of
being difordered, and then affeCting the nervous
fibrils, we have very great rcafon to be furprifed, that
thefe cylindrical pipes are not much more frequently
put out of order, by too great or too fmall a quanti-
ty of liquors; by two vifcid or too thin fluids; by
liquors confiding of too mild and fluggifli particles,
or of too acrid pungent ones; by too great or too
little motion given to the liquors; by the diameters
of the pipes being too much llraitened, or too much
enlarged ; and by a great many other varieties of cir-
cumftances which might be thought capable of di-
fturbing the fun&ions of the nerves, fuppofing them
to be cylindrical excretories of the gland, the brain.

42. Tha

Of the NERVES in GENERAL. 263

4 2. The numerous veflels of the encephalon have
brought fome of the gentlemen who afiert the nerves
to be folid, to acknowledge, that there is a liquor fe-
creted in the brain : But then they will not allow that
this liquor is fent out by the proper nervous fibrils;
but that it is ;-oured into the cellular fubftance in
which the nerves lie, to keep them moifl: and fupple,
and therefore fit for exerting their elafticity, vibration,
£sV. by which, in their opinion, the effects common-
ly afcribed to nerves are produced.

43. Befides the objections already mentioned (§ 32.
33.) againfl the nerves aCting as elaftic firings, this
opinion has fome other difficulties which may be ob-
jected to it : For inftance, there is not one analogous
example in the whole body of liquors fecreted in a
large gland, to be poured into a cellular fubftance,
as is here fuppofed ; the liquors in the cells of the
tela cellularis of other parts are feparated from the
little aiteries which are diflributed to thefe cells.

Further, it cannot be imagined, how a liquor fe-
creted in the cortex of the brain fhould make its way
through the medulla , to come out into the cellular
membranes on the furface of that medulla.

Lajlly , A very fimple experiment, of injecting wa-
ter by the artery of any member, and thereby filling
the cellular fubftance of the nerves of that member,
lhews evidently, that the liquor of the cellular fub-
flance of the nerves has the fame fountain as the li-
quor has in the tela cellularis any where elfe, that is,
from the little arteries dilperfed upon it.

44. The doCtrine of a fluid in the nerves, is not
only thus fupported by the analogy of the brain and
nerves to the other glands and their excretories, but
thole who maintain this doCtrine mention an experi-
ment which they think direCUy proves a fluid in the
nerves. It is this: After opening the thorax of a
living dog, catch hold of and prefs one or both the
phrenic nerves with the fingers, the diaphragm imme-
diately ceafes to contraCl ; ceafe to comprefs the
nerves, and the mufcle aCts again ; A fecond time.

2o4 Of the NERVES in GENERAL.

lay hold of the nerve or nerves fome way above the
diaphragm, its motion flops. Keep firm the hold of
the nerve, and, with the fingers of the other hand,
flrip it down from the fingers which make the com-
preffion towards the diaphragm, and it again con-
tracts : A repetition of this part of the experiment
three or four times, is always attended with the fame
effe£ts ; but it then contrails no more, flrip as you
will, unlefs you remove the prefiure, to take hold of
the nerves above the place fir fl pinched * when the
mufcle may again be made to contract, by dripping
the nerve down towards it. This experiment I have
done with the fuccefs here mentioned. Let any one
try if he can imagine any other reafonable account
of thefe appearances, than that the prefiure by the
fingers dopped the courfe of a fluid in the nerve;
that fo much of this fluid as remained in the nerve,
betwixt the fingers and diaphragm was forced into
that mufcle by dripping, and when it was all prefled
away, the fingers above preventing a fupply, the
ntufclc con trailed no more till the fingers were re-
moved, and a frefli flow by that means was received
from the fpinal marrow, or from that part of the
nerve which had yet not been fo dripped.

It has been objected to the conclulions from this
experiment, i. That the diaphragm is fet in motion
by dripping the nerve from, as well as towards this
mufcle; and this may be well expected; for a liquor
in fuch fmall pipes hindered to flow backwards by li-
gature, pinching fingers, or even the flow of their
liquors from the fountain, will regurgitate forwards
with velocity, when prefled backwards. We fee it
happen in the dalks of tender fucculent plants.

2. It is faid, that mufcles ceafe to a£t when their
veins are tied, as well as when their arteries or nerves
are tied or cut, but that mufcles continue to a£l when
their veins are cut ; by which it would appear, that
the overloading of the veflels is an impediment to the
action of mufcles, and therefore the ceafing of their

action.

Of THE NERVES in GENERAL. 265

aCtion, when their arteries or nerves are tied or cut,
may alfo be owing to the liquor in the branches of
thcfe pipes of mufcles flagnating when it is not pro-
pelled by the flow of more liquor from their trunks,
and not to any influence or moving power, which now
ceafes to be conveyed to them.

It is to be obferved in making tne experiments jufl
now mentioned, that the contraction of the mufcles
ceafes fooneft when the nerves, and lateft when the

veins are tied. That when veins are tied, not only

are the veflels overloaded, but all the cellular fub-
ftance of the mufcles is filled wTith coagulated blood;
whereas when the arteries and nerves are tied, the
reverfe is feen, the mufcles are lax and of lefs btdk.
So that in thefe cafes, the ceafing of the contraction
of the mufcles feems to depend on very different
caufes, to wit, a deprivation of neceflary liquors in
the one, and a redundancy of fuperfiuous blood in
the other. An elaftic flick may be deprived of its e-
lafticity by being made either too dry or too wet.

45. Some gentlemen, convinced of the reafonabie-
nels of the fecretion of a liquor in the brain to be
fent out by the nerves, but not comprehending how
a fluid could have fuch a rapid retrograde motion as
they imagined was neceflary for conveying the im-
preflions of objeCts made on the extremities of nerves
to the fetiforiam, fuppofed two forts of nerves; one
that conveyed a liquor for mu'cular motion and nu-
trition ; the other compofed of folid nerves, that
were to ferve for organs of the lenfcs, to convey the
vibrations communicated from objects to the J\nfo~
riutn.

46. To this opinion (§ 45.) the objections againfl
the fenfatory nerves aCting by vibration (§ 32.)^ may
be made; and there is fo little reafon to fuipect any
difference in the texture of the dilierent parts of the
brain or nerves, that, on the contrary, the ItruClure
is every where fimilar, and branches of the fame
nerve often ferve both for fenfation and motion.

Z How

266 Of the NERVES in GENERAL.

How little necefTity there is for fuppofing extreme-
ly rapid motions of the nervous fluid, is to be exa-
mined foon.

47. 'I he hypothefis of great celerity in the motion
of the fluid of the nerves being neceflary, gave alfo
life to another divifion of the nerves, into arterions
or effluent , and venous or refluent. It was faid, that
mufcular motion and nutrition depended on the arte-
rious nerves •, and that the fenfations depended on an
accelerated motion of the nervous fluid towards the
brain, by the impreflions which the obje&s of the
fenfes make upon the venous nerves. By thisfuppofi-
tion the abfurdity of rapid fluxes and refluxes in the
fame canal was prevented, and an advantage was
thought to be gained by it, of faving too great a
wade of the fluid of the nerves, which otherwife the
encephalon and fpinal marrow could not fupply in fuf-
licient quantity to anfvver all the exigencies of life.

48. To this opinion (§ 47.) it has been objected,

1/7, That there is no example in the body, of a fe-
creted liquor being returned immediately and unmix-
ed to the gland by which it was originally feparated
from the mafs of blood ; which would be the cafe,
were there venous nerves, idly, There is no occafiou
for faving the fluid of the nerves in the way propof-
ed ; the organs for fecreting that fluid being large e-
nough to fupply all that is neceflary of it in the com-
mon fundlions of life. 3 dly, If the fluid of the

nerves was to be thus kept in a perpetual circulation,
it would foon become too acrid for continuing with
fafety in fuch fenfible tender veflels as the brain and
nerves are compofed of. 4 thly, This hypothefis will
not anfwer the defign for which it was propofed :
For though the momentary application of an objett
might caufe an acceleration in the fluid of venous
nerves, yet if the obje£t was kept applied to the
nerves, it would flop their fluid, fo that it could not
go forward to the brain ; and therefore, according to
this doftrine, we fliould be fenfible of no objefts,

except

Of THE NERVES in GENERAL. 267

except thofe whofe application to the organs of the
fenfcs was momentary.

49. Let us now fuppofe it probable, that the ence-
phalon and fpinal marrow fecern a liquor from the
blood which is fent into all jthe nerves, and that by
the means of this liquor, the nerves perform the
offices commonly affigned to them it is next necef-
fary to enquire what kind of liquor this is, and how
it moves, in order to determine how well its nature
and motion are fitted for performing what is expedit-
ed'from if.

50. The liquor of the nerves has been fancied by
fome to be of a very firong acid or alcnline nature:
But fince none of our juices appear to be of ibis tort,
and fince fuch liquors irritate and defiioythe parts of
the body which they are applied to, we cannot con-
ceive how the brain can feparate, or the nerves could
bear any thing of fuch an acrid nature. This ten-
dernefs and fenfibility of thefe organs mud hinder us
abfolutely from fuppofing that the liquor of the nerves
can be acrid or pungent, or of the nature of fpirit
of wine, hartfhorn, &c.

51. Some have imagined the liquor of the nerves
to be capable of vail explofion like gun-powder, or of
violent fudden rarefaction like air, or of firong ebul-
lition like boiling water, or the mixture of acids
with alcaline liquors. But as the mafs of blood from
which this fluid is derived, is not poflefied of any
fuch properties, we cannot fuppofe the blood to fur-
nifh what it has not in itfelf. Befides, all thefe ope-
rations are too violent for the brain or nerves to bear;
and when once they are begun, they are not fo quick-
ly controlled or reftrained, as experience teaches us
the nerves can be made to ceafe from acting.

52. We are not fufficienily acquainted with the
properties of an a/her or electrical effluvia pervading
every thing, to apply them jufily in the animal oeco-
nomy ; and it is as difficult to conceive how they
fhould be retained or conducted in a long nervous
cord. Thefe are difficulties not to be furmounted.

£ 2 53. The

268 Of the NERVES in GENERAL.

53. 1 he fared way of judging what kind of liquor
this of the nerves muli be, is to examine the liquors
of Gmilar parts of the body. All tiie glands fepa-
rate liquors from the blood much thinner than the
compound mafs itfelf ; fuch is the liquor poured into
the cavity of the abdomen , thorax , ventricles of the
brain, the faliva , pancreatic juice, lymph, &c. Where-
ever theie is occafion for fecreted liquors being thick
and vifcid, in order to anfwer better the ufes they are
intended for, nature has provided iefervoirs for them
to (lagnate in, where their thinner parts may be car-
ried off by the numerous abforbent veins difperfed
on the_ (ides of thofe cavities ; or they may exhale
where they are expoled to the open air. The mucus
of the nofc becomes vifcid by flagnation ; for, when it
is immediately fecreted it is* thin and watery ; as ap-
pears from the application of fternutatoiies, tsY.
The cerumen of the ears is of a watery confidence,
when juft fqueezing out. The mucus of the alimen-
tary canal grows thick in the lacuna. The bile in the
hepatic dutt has little more confidence than lymph ;
that in the gall-bladder is vifcid and ftrong. The
urine is much more watery as it flows from the kid-
neys, than when it is excreted from the bladder.
'I lie feed is thin as it comes from the tcfticles, and is
con coded in the vefculee feminales, c5V.

^4. Hence (§ 53.) we may fafely conclude, that a
thin liquor is fecreted in the cortex encephali and fpinal
marrow; and feeing the thinnefs of fecreted liquors
is generally, as the divifions of the veffels, into (mail
iubtile branches, and that the ramifications within
the feu 11 are almoft infinitely fubtile, the liquor fe-
creted in the encephalon may be determined to be a-
inong the fined, or thinned fluids.

55". Seeing alfo that we can obferve no large refer-
red, where the liquor fecern d in the cortical fubjlance
is depofited, to have its finer parts taken off, we have
reafon to think, that it goes forward into the nerves
in the tame condition in which it is fecerned.

56. By

Of THE NERVES in GENERAL. 269

56. By fine or fubtile animal liquors, is meant no
more than thofc which are very fluid, and which
feem to confift of a large proportion of watery par-
ticles, and a lefler one of the oily, faline, and ter-
reftrious particles. Some of the liquors which we
can have in fufficient quantity to make experiments
•with, are fo fluid, and have fo little vifcidity or co-
hefion of parts, that when laid upon a piece of dean
mirror, they evaporate without leaving a Itain ; l'ucli
is the liquor oozing out from the furface of the pleura,
the lymph, and feveral others.

If then thefe liquors; which are fubied: to cur ex-
amination, the fecerning vefl'els of which are fo large
that we can fee them, have fuch a fmall cohefion of
parts, it might not be unreafonable to fay, that the
liquor of the nerves is as much more fine and fluid
than lymph, as the vefl'els feparating it are fmaller ;
and therefore that the fluid of the nerves is a defe-
cated water, with a very fmall proportion of the other
principles extremely fubtilized.

57. Two experiments are faid to contradict this
opinion, of the liquor of the nerves being fo fluid and
fubtile. One is, that upon cutting the cauda equina
of a living animal, a liquor as vifeid as the white of
an egg drops out : The other is, that a wounded nerve
yields a glairy fames. But thefe do not appear to be
the proper fluid of the nerves; fince it is evident,
that what is difeharged in both thefe cafes, comes
out of the cellular fubftance involving the nervous
fibrils.

58. Confidering how many experiments make it
evident, that there is a conltant uninterrupted ftream
of liquors flowing through all the canals of animals,
which convey liquors compofed of particles fmalier
than the diameter of their canal, which is alwr.vs
the cafe of the nerves in a natural ftate ; it is lop rifl-
ing how it ever could be thought that the liquid of
the nerves (hould be obliged to flow from the brain
to each mufcle the moment we will; or that this li-
quor ihould flow back with the like fwiftnefs from

Z 3 the

*7® Of the NERVES in GENERAL.

<Le extremity of each nerve, to which an bbjeft of
fenfarion is applied. The nerves, as well as the o-
ther excretories of the glands, always are full of li-
quor; the degree of diftenflon of the canals not be-
ing at all times alike even in a found ftate. But this
happens without inconvenience, as the Tides of the
canals have a power to accommodate themfelves to
the p refen t quantity, unlefs it is very much above or
below the natural flandard; in both which cafes dif-
eafes enfue.

59. The motion of the fluid in the nerves is there-
fore not only conflant, but it is alfo equal, or nearly
fo : For, though the blood in the larger arteries is
moved unequally, by the unequal forces, the contra£lion
of the ventricle of the heart, and the weaker power,
the fy/lcle of the arteries ; yet the difference between
thefc two moving powers comes to be lefs and lefs
perceptible, as the arteries divide into fmaller branches;
becaufe of the numerous refiflances which the liquors
meet with, and becaufe the canals they move in be-
come larger, till in the very fmall arterious branches,
there i« no fenfible difference in the velocity of the
liquors from the effect of the heart or arteries. The
motion of the fluids muff ffill be more equal in the
cxcretories of glands, and particularly in thofe where
the veffels have divided into very minute branches,
and the liquors have no other propelling force but the
heart and arteries, (fee § 1); therefore the nervous
fluid moves eonftantly, equally, and flowly, unlefs
when its courfe is altered by the influence of the
mind, or by the preffure of fome neighbouring attive
organ.

60. As there is neither proof nor probability of the
vahes fuppofed by fame in nerves, we are not to af-
fume them in accounting for any phenomena.

6 1. We have not, and perhaps cannot have any
idea of the manner in which mind and body a£k up-
on each other; but if wc allow that the one is af-
fetted by the other, which none deny, and that the
fluid of tfce nerves (whatever name people pleafe to,

give

Of the NERVES in GENERAL. 271

give it) is a principal inftrument which the mind
makes ufe of to influence the a£tions of the body, or
to inform itfelf of the impreflions made on the body,
we mufl allow that the mind can dire£t this inftru-
ment differently, particularly as to quantity and ce-
lerity, though we muft remain ignorant of the man-
ner how many phenomena depending on this connec-
tion of mind and body are produced. thus we
would in vain attempt to account for animals conti-
nuing, after their heads were (truck off, or their hearts
were cut out, to perform actions begun before they
fuffered any injury.

62. Let us now fuppofe the nervous fluid fuch as
has been argued for, to wit, a very fluid faponaceous
water, moving in a conftant, equal, flow ftream, from
the encephalon and fpinal marrow, in each of the pro-
per nervous fibres, except when the motion is chan-
ged by fome acceffory caule, fuch as the mind, pref-
fure of other parts, &c. •, and let us examine how
well fuch a fuppofition will agree with the phenomena
of the three great functions, nutrition, fenfation, and
mufcular motion, which the nerves are principal in-
ftruments of.

63. In general, we may fay, that nerves can carry
fluids to the mod minute part of the body, to fupply
what is wafted in any of the folids •, that the impref-
fion made by the objects of the fenfes on the very
foft pulpy extremities of the nerves of the organs of
the fenfes, mult make fuch a flop in the equal-flowing
nervous fluid, as muft inftantaneoufly be perceptible
at the fountain head from which the pipes affected
arife ; that the conftant flow of the liquor of the
nerves into the cavities of the mufcular jibr tile, occa-
fions the natural contra£tion of the mu(cles, by the
as conftant nifus it makes to incieafe the tranfverfe,
and to fhorten the longitudinal diameter of each fibre ;
and that it is only to allow the mind a power of de-
termining a greater quantity of this fame fluid with a
greater velocity into what mulcular fibres it pleafes,

to

212 Of the NERVES in GENERAL.

to account for the voluntary ftrong aCtion of the
mufcles.

64. But fince fuch a fuperficial account would not
be fatisfaCtory, it will be expected, that the princi-
pal phenomena of thefe three functions fhould be ex-
plained by the means of fuch a fluid as has been fup-
pofed ; and that the feveral objections againlt this
doctrine fiiould be anfwered : Let us attempt this;
and where we cannot extricate ourfelves from diffi-
culties which may be thrown in, let us honeftly ac-
knowledge ignorance.

65. a. If water, with a very fmall proportion of
oils and falts from the earth, proves a fit nourifhment
for vegetables, fuch a liquor as the fluid of the nerves
has been defcribed (§ 56.) may not be unfit for re-
pairing the wafte in animals.

ft- The flow continual motion of this nervous fluid
(§ t; 8. 59 ) to the molt minute parts of the body
(§ 10.), is well enough calculated to fupply the parti-
cles that are conftantly worn off from the folids
by the circulation of the liquors and neceffary actions
of life.

y • The greater proportional fize of the encephalon
in young creatures than in adults, feems calculated
for their greater proportional growth : For the young-
er the animal is, the larger encephalon and fpeedier
growth it has.

S- A palfy and atrophy of the members generally
accompanying each other, fiiew, that nourifhment,
fenfation, and motion, depend on the fame caufe.

'• It was laid (§ 26.), that the nerves were princi-
pal inflruments in nutrition : It was not affirmed,
that they were the foie inflruments ; and therefore an
atrophy may proceed from the compreffion or other
lefion of an artery, without being an objection to
the doCtrine here laid down.

66. a. All objeCls of fenfe, when applied to their
proper organs, aCt by impulfe ; and this aCtion is ca-
pable of being increafed by increafing the impelling
force. In tangible objeCts, that is clearly evident ;

the

Of the NERVES in GENERAL. 273

the'clofer they are preffed to a certain degree, the
more diftind perception enfues. Odorous particles
need the afiiftance of air moved rapidly, to afled our
nofe: Sapid fubftances, that are force fufficient to
give us an idea of their tafte by their own weight, are
a {Tilled by the preffure of the tongue upon the palate:
The rays of light colleded drive light bodies before
them : Sound communicates a vibration to all bodies
in harmonic proportion with it.

The impulf^s made thus by any of thefe objeds on
the foft pulpy nerves (§ 21.), which are full of li-
quor, preffcs their Tides or extremities, and their li-
quor is hindered to flow fo freely as it did. The ca-
nals being all full (§ 58.) this refiftance mull inftan-
taneoufly affed the whole column of fluids in the ca-
nals that are prefled, and their origins, and have the
fame effed as if the impulfe had been made upon the
origin itielf. To illuflrate this by a grofs compari-
fon : Let any one pulh water out of a fyringe, through
a long flexible pipe fixed to the fyringe, and he is
fenfible of refiftance or a pulh backwards, the mo-
ment any one flops the orifice of the pipe, or clofes
the Tides of it with his fingers. This impulfe made
on the nerves, and thus communicated to their ori-
gin, varies according to the ftiength or weaknefs,
the quicknefs or flownefs, the continuance or fpeedy
removal, the uniformity or irregularity, the conftan-
cy or alternation, &c. with which objects are applied
to the nerves.

b. Whenever any objed is regularly applied with
due force to a nerve, rightly dilpoled to be imprefl'ed
by it, and is communicated, as juft now explained,
to the fenjorium , it gives a true and juft idea of the
objed to the mind.

c. The various kinds of impulfes which the diffe-
rent dalles of obj-.ds make, occafion in animals,
which ought to have accurate perceptions of each
ofcjcd, a neceflity of having the different organs of
the lenfes varioufly modified, fo that the feveral im-
pulfes may be regularly applied to the nerves in each

organ i

274 Of the NERVES in GENERAL.

organ; or, in other words, we muft have different
organs of the fenfes fitted to the different claffes of
objects.

d. As the objefts have one common property of
impulfe, fo all the organs have mod of the properties
of the organ of touching in common with the pnpilLe
of the fkin. In the nofe and tongue, this is evident :
In fome operations of the eyes we can alfo perceive
this ; as we may likewife do in fome cafes where mat-
ter is collected in the internal ear. •

e. Thefe properties common to the different objefts
and organs, occafion frequently uncommon effects in
the application of an objedf to an organ proper to an-
other objedt of fenfation ; for fometimes we have the
fame idea as if the objedt had been applied to its own
proper organ : At other times the objedt is as it were
changed, and we have the idea as if the organ had
had its own proper objedt applied to it. Thus, for
example, light is the proper objedt to be applied to
the eye, to give us any idea of' colours ; yet when
all light is excluded from the eyes, an idea of light
and colours may be excited in us by coughing, fneez-
ing, rubbing, or ftriking the eye-ball — A cane vi-
brating, fo as not to excite found perceptible to the
ear, applied to the teeth, raifes a ftrongidea of found ;
as a little infedt creeping in the meatus auditorius alfo
does. — The fingers applied to two rough furfaces,
rubbing on each other, are fenfible of the found they
make ; fuigeons of any pradlice in the cure of frac-
tured bones can bear witnefs to the truth of this. —
The fingers dipped in acid and feveral other acrid li-
quors, have a fenfation very like to tailing. — Smel-
ling and tailing, every body knows, are fubfervient and
afiifling to each other. From fuch examples we have
further proof of one general caufe of our fenfations,
to wit, impulfe from the objects; and of fuch a fi-
milarity andjelation in the organs as might give rea-
fon for imagining that any one of them would be ca-
pable of producing the effedt of another, if the im-
pulfes of the different objects could be regularly ap-

Of THE NERVES in GENERAL. 275

plied to each. — Hence light and found may affed in-
feds and other animals that have not eyes or ears.

f. If the impulfe of an objed is applied with due
force, but irregularly, a confufed idea of the objed
is raifed. Diftant objeds are confufed to myopes , as
very near ones are to prejbyiee.

g. If the application of the impulfe is regular, but
the force with which it is applied is too weak, our
perception of the objed is too faint. One may whif-
per fo low as not to be heard.

h. If the application of objeds is too violent, and
there is any clanger of the tender organs of our fenfes
being hurt or deftroyed, an uneafy fenfation we call
pain is raifed, whatever the organ thus injured is.
The objed of feeling affeds every organ : Thus pref-
fure, ftretching, cutting, pricking, acrid falts, pun-
gent oils, great heat, violent cold, &fc. occafion pain,
where-ever they are applied. Befides, every particu-
lar organ can be affeded with pain by the too violent
application of its own proper objed. Too much light
pains the eyes ; very loud founds (tuns the ears ; very
odorous bodies and too fapid objeds hurt the nofe
and tongue. A pretty fure proof this, that the ob-
jeds of our fenfes all ad, and chat the organs are all
impreffed, in nearly the fame way.

i. Since a middle impulfe, neither too fmall nor
too great, is neceflary for a clear perception of objeds,
we would often be in danger of not diflinguifbing
them, if we were not fubjeded to another law, to
wit, that numerous impulies made at once, or in a
quick fuccefhon to each other, increafe our percep-
tions of objeds. Thus, fuch found as would not be
heard on a mountain top, will be diftindly heard in a
wainfcotted-chamber. — We feel much more clearly a
tangible objed when our finger is drawn alongft it,
than when applied with the fame force, but by a
fingle preflure, upon it. — We make repeated applica-
tions of odorous and fapid objeds, when we wifh to
fmell or tafte accurately. — The end of a burning flick

appears

1^6 OF THE NERVES IN GENERAL.

appears much more luminous when quickly whirled
in a circle than when at red:.

k. Whenever the uneafy fenfation, pain, is railed
by the too ftrong application of objeCts, a fort of ne-
ceflity is as it were impofed upon the mind to endea-
vour to get free of the injuring caufe, by either with-
drawing the grieved part of the body from it, as one
retires his hand when his finger is pricked or burnt ;
or the injuring caufe is endeavoured to be forced from
the body, as a tenefmus excites the contraction which
pulhes acrid faeces out of the reftum. In both thefe
operations, a convulfive contraction is immediately
made in the ltfed part, or in the neighbourhood of
it; and if the irritation is very ftrong or permanent,
the greater part of the nervous fyftern becomes affec-
ted in that fpafmodic or convulfive way. — Is it this
neceffity which obliges the mind to exert herfelf in
refpiration, or in the aCtion of the heart, when the
lungs or heart are gorged with blood ? or the iris to
contraCl the pupil, when the eye is expofed to ftrong
light ? or fneezing to be performed when the nofe is
tickled ? — Will not a ftimulus of any nerve more

readily affeCt thofe with which it is any where con-
nected than the other nerves of the body ? — May not
this fympathy ferve as a monitor of the mind rather
to employ the organs fumifhed with nerves thus con-
nected, to aflift in freeing her of any uneafy fenfa-
tion, than ro make ufe of any other organs? — Will
not this in fome meafure account for many falutary
operations performed in the body, before experience
has taught us the functions of the organs performing
them ?

This nifus of the mind to free the body of what is
in danger of being hurtful, may ferve to explain the
phenomena of a great many difeafes, when we art ac-
quainted with the dillribution of the particular nerves ;
and from this we can underfband the operation of me-
dicines that llimulate ; and may learn how, by ex-
citing a (harp, but momentary pain, we may free the
body ol another pain that would be more durable ;

277

Of the NERVES in GENERAL.

and that, by having it thus in our power to determine
a flow of the liquor of the nerves to any particular
part, for the benefit of that part, or the relief of any
other difeafed part, we can do confiderable lervicc by
a right application of the proper medicines.

/. If a pain-giving caufe is very violent or long
continued, it deftroys the organs either irrecoverably,
or puts them fo much out of order that they only
gradually recover : People have been made blind or
deaf for all their lives after a violent efFeG; of light
on their eyes, or of found on their ears ; and we are
frequently expofed to as much light and found as to
make us unfit to fee or hear for a confiderable time.
I would explain this by a ligature put round the ten-
der branch of an herb. This ligature drawn to a
certain degree, may weaken the canals fo as to be un-
fit for the circulation of the juices a good while, till
they are gradually explicated and made firm by thefe
juices : A firitter ligature would diforder the .{true-
ture of the fibres fo much, that the liquors could not
recover them. The analogy is fo plain, that it needs
no commentary. — Thus, the influence of a nerve tied
with an artery in the operation of an aneurifm, may
ceafe lor fome time, but be afterwards recovered.

67. 1. In applying the fluid of the nerves to the
a£tion of mufcles, it was faid, that the natural or
involuntary contr?<Rion of mufcles was the nifus which
the nervous fluid flowing conftantly into the muicu-
lar fibres makes to diftend thefe fibrils, by enlarging
their tranfverfe diameters and fliortening their axes;
and that voluntary contraction was owing to a greater
quantity of that nervous liquor determined towards
the mufcle to be put in action, and poured with
greater momentum into the mufcular fibrils, by the
power of the mind willing to make l'uch a mufcle to
add, or obliged to do it by an irritating pain-giving
cauie (§ 66. k.\

2. Some object to this account of mufcular motion,
that if there is no outlet for the liquor fuppofed to
be poured into mufcular fibres, mufcles would always

A a be

278 Of the NERVES in GENERAL.

be in a ftate of contraction, which they are not ; and
if there is a paflage from the fibrils, the liquor would
flow out as faft as it was thrown in ; and therefore
no diftenfion of the fibres or contraction of the muf-
fles could he made.

3. In anfwer to this objection, it is obferved, that
notwithftanding the evident outlet from the arteries
into the veins, yet the arteries are diflended by the
fyjiole of the heart, or any other caufe increafing the
Momentum of the blood.

4. It has been alfo objeCted to § 1. That, if it was
true, the volume of the mufcle in contra&ion necef-
farily would be confiderably increafed by fo much li-
quor poured into its fibrils ; whereas it does not ap-
pear, by any experiment, that the volume of a muf-
cle is increafed by its being put into aCtion.

5. To this it has been anfwered, 1. That when the
axes of mufcular fibres are fhortened, and their tranf-
verfe diameters are enlarged, the capacities of their
fibres, and confequently their volume, may not be
changed, the diminution one way balancing the in-
creafe in the other. 2. That the fpaces between the
mufcular fibres are fufficient to lodge thefe fibres when
they fwell, during the contraction of a mufcle, with-
out any addition to its bulk ; and that it plainly ap-
pears that thefe fpaces between the fibrils are thus oc-
cupied, by the comprelfion which the larger veflels of
mufcles, which run in thofe fpaces, fiuffer during the
aCtion of the mufcle •, it is fo great as to drive the
blood in the veins with a remarkable accelerated ve-
locity.

6. Another objeClion to the aCtion of mufcles be-
ing owing to the influx of a fluid into their fibrils, is,
That mufcular fibres are diftrattile, or capable of be-
ing ftretched-, and therefore, when a fluid is poured
into their hollow fibrils, they would be ftretched lon-
gitudinally, as well as have their tranfverfe diameters
increafed ; that is, a mufcle would become longer,
as well as thicker, when it is put into aCtion -, where-
as

Of the NERVES in GENERAL.

279

as it is certainly known, that a mufcle is fhortened
while it aCts.

7. In anfwer to this, it has been remarked, That
though mufcular fibrils are diflraCtile, yet they will
not yield to, or be flretched by every force, however
fmall, that might be applied to them. A cord that
can be dretched in length by the weight of a pound
or two, would not yield in the lead to an ounce or
two; and it mud likewife be obferved, that gradual-
ly as any body is dretched, its refidance to the
{(retching force increafes. A rope may be dretched
to a certain length by a pound weight appended to
it, which would require two pounds to dretch it very
little further ; and therefore, the general observation
of animal fibres being diflraCtile, cannot be a rea-
sonable objection to the account of mufcular motion
above-mentioned, unlefs a proof is brought that the
force which the liquid of the nerves mud exert upon
each fibre of a mufcle, in order to make it aCt, is
capable of didracting or dretching the fibres; which
has not yet been attempted to be proved. — It would
appear, from the pain caufed by too great an effort of
mufcles, efpecially in weak people, that mufcular
fibres can bear very little diflraCtion without danger
of a Solution of continuity.

8. Mufcles ceafing to act when their arteries are
tied or cut, and being brought into motion by inject-
ing liquors into the arteries even of a dead animal,
has been mentioned as objections to the nervous in-
fluence caufing their contractions.

To the fiilt of thefe experiments it may be anfwer-
ed, That the tying or cutting of the nerves, fooner
produces the etfcCt of making the contraction ceafe,
than flopping the influx of the arterious blood does ;
and it will be univerfally allowed, that the influx of
blood into mufcles is necefi'ary for performing their
functions right.

Whoever obferves the motion which injecting wa-
ter, or any other liquor into the arteries of a dead
nimal, caufcs in its mufcles, will not compare it to

A a 2 what

2So Or THE NERVES in GENERAL.

■what contraction, whether voluntary or excited by ir-
ritation, he may fee in a living one.

9- ^ mufcular motion depends on the influx of the
nervous liquid, the inflantaneous contraction of a
mufcle, when the mind wills to make it a£t, will be
eaflly underftood from the nerves being always full of
their liquor (§ 58. 66. a.)

10. It either the nerves of any mufcle do not fur-
nifh a fufficient quantity of their liquor, or if the fi-
bres of a mufcle become too eaflly diftraCtile, fuch a
mufcle will be inactive or paralytic.

ij. If too great a quantity of the liquor of the
nerves is determined to a mufcle or mufcles, by any
caufe which the mind cannot command, fuch mufcle
or mufcles will be convulfed.

1 2. - It the motion of the liquid of the nerves is
not uniform, but by difeafe becomes irregular, an al-
ternate relaxation and contraction of mufcles may be
the conlequence. Hence trembling palfies, chorea
Salih?/ Viti , &c. Hence alfo the convulfive tremors
which animals have when they lofe much blood.

13. Though the nerves may not furnifh fo much
liquor as may be fufficient to make mufcles contrail
with ftrength enough to overcome the refitlances to
their actions, yet there may be a fufficient quantity
of liquor in the nerves to allow the imprellions of
objedts to be conveyed to the fenforium. This may
be one caufe ot a member’s being fometimes fenfible
after it cannot be moved.

14. Unlefs the liquor of the nerves acquires fome
energy in the brain, which we have no reafon to
think the circulation of the fluids in the veffels can
give it, or unlefs it has other properties than what
we can difeover in it, or unlefs there is an agent re-
gulating its momentum and courfe to different parts
which we are not confeious of ; if fome of thel'e, I
fay, do not obtain, the a£Hon of the heart continuing
of equal force to propel our liquors, notwithftanding
all the refinances that are to it, is not to be explained.

15. All

Of the NEVRES in GENERAL. 2 Sx

15. All mufcles, but efpecinlly the heart, continue
to contract in an irregular way, after they are cut a*
way from the animal to whom they belonged ;
which may be owing to the liquors continuing to
flow in the fmall veflels, and being poured irregularly
into the mufcular fibrilla.

16. It is faid that a mufcle cut out of the body
continues fome time to be capable of contradtion ;
whereas, by tying its arteries or nerves, while it is
otherwise entire in the body, it lofes its contradfing
power, which therefore does not depend on thefe or-
gans, the arteries or nerves.

The lofs of the power of adding, when the arteries
or nerves are tied while the mufcle is in the body, is
denied by fome who made the trial ; and it might
be expedfced, that the motion of a mufcle would be
more confpicuous where there is no refiftance to it,
as is the cafe when it is cut away from all the parts
it is connected with, than when its connedlion remains
with parts refilling its contradlile efforts.

17. After the heart, or any other mufcle cut away
from an animal, has ceafed to contract, its contrac-
tion may again be reftored, by breathing upon it, c r
pricking it with any fharp inffrument. That heat or
pricking fhould, by their Jlimulus (§ 66. Z\), occafion
contradlion in a living creature, may be underftood ;
but how they fliould have the fame effedt in a mufcle
feparated from an animal, I know not.

68. Some have thought the ganglions of nerves
(§ 1 8, 19, 20.) to be glandular, and to perform a fe-
cretion. — Others, from their firm texture, fuppofe
them to be mufcular, and to ferve to accelerate the
motion of the liquor in the nerves which proceed
from them ; but as no proof is offered of either of
thefe opinions, they cannot be maintained. — Others
would make them ferve, 1. To divide a fmall nerve
into many nerves, and by thefe means to increafe the
number of nervous branches. 2. To make nerves
come conveniently by different diredtions to the paits
to which they belong. 3. To reunite feveral fmall

A a 3 nervous

282 Of the PARTICULAR NERVES.

nervous fibres into one large nerve. — Since no proof
is brought that thefe three things cannot be done
without the interpofition of a ganglion , but, on the
contrary, we fee them performed where there are no
ganglions , we mull continue to acknowledge igno-
rance concerning the ufes of thefe knots, the gan-
glions.

Or the PARTICULAR NERVES.

’’T' I S generally laid, that there are forty pair of
nerves in all ; of which ten come out from the
encephalon, and the other thirty have their origin from
the fpinnl marrow.

Of the ten pair of neives which come from the en-
cephalon, the fnft is the OLFACTORY', which long
had thy name of the mammillary proceJJ'es of the
brain, becaufe in the brutes, cows and fheep, which
were mod commonly dirtc£ted by the ancients, the
anterior ventricles of the brain are extended for-
wards upon thefe nerves, and adhere fo firmly to
them, that they feem to make the upper fide of the
nerves. Each of them being large, where it begins
to be ftretched out, and gradually becoming fmaller
as it approaches the cribriform bone, was imagined
to refemble a nipple. Thofe who miftook the ven-
tricles for part of the nerves, obferving the cavity in
them full of liquor, concluded, that thefe olfactory
nerves ferved to convey the fuperfluous moffture of
the brain to the holes of the ethmoid bone through
which it parted into the nofe. But in man, the ven-
tricles cf whofe brain are not thus extended forwards,
thefe nerves are fmall, long, and without any cavity,
having their origin from the corpora Jiria/a, near the
part where the internal carotid arteries are about to
fend off their branches to the different parts of the
brain j an^ in their courfe under the anterior lobes
of the brain, which have each a deprclfion made for

lodgir

Of the PARTICULAR NERVES. 283

lodging them, the human olfaftory nerves become
larger, till they are extended to the cribriform bone ■,
where they fplit into a great number of fmall fila-
ments, to pafs through the little holes in that bone j
and, being joined by a branch of the fifth pair o_
nerves, are fpread on the membrane of the nofe.

The tender ftru&ure and fudden expanfion of thefe
nerves on fuch a large furface, render it impoflible to
trace them far ; which has made fome authors deny
them to be nerves : But when we break the circum-
ference of the cribriform lamella , and then gently
laife it, we may fee the diflribution of the nerves
fome way on the membrane of the nofe.

The contrivance of defending thefe long foft nerves
from being too much prefl'ed by the anterior lobes of
the brain under which they lie, is fingular ; becaufe
they have not only the prominent orbitar procefTes of
the frontal bone to fupport the brain on each fide,
with the veins going into the longitudinal ftnus, and
other attachments bearing it up, but there is a groove
formed in each lobe of the brain ltfelf for them to
lodge in. — Their fplitting into fo many fmall branches
before they enter the bones of the fkull, is likewife
peculiar to them ; for, generally, the nerves come
from the brain in difgregated filaments, and unite
into cords, as they are going out at rhe holes of the
bones. ’1 his contrivance is the beft for anfwering
the purpofe they are defigned for, of being the organ
of lmelling •, for, had they been expanded upon the
membrane1 of the note into a medullary web, iuch as
the optic nerve forms, it would have been too fenfi-
ble to bear the imprefhons of fuch objects as are ap-
pl-ed to the nofe ; and a diflribution in the more
common way, of a cord fending off branches, would
not have been equal enough lor luch an organ of ien-
fation.

rl he 2 d pair of nerves, the OPTIC , riling from
the thnlami nervorum cpticorum , make a large curve
outwards, and then run obliquely inwards and for-
wards, till they unite at tnc fore-part oi the fella Tur-
* cica t

284 Of THE PARTICULAR NERVES.

cica ; then foon divide, and each runs obliquely for-
wards and outwards, to go out at its proper hole in
the fphenoid bone, accompanied with the ocular ar-
tery, to be extended to the globe of the eye, within
which each is expanded into a very fine cup-like web,
that lines all the infide of the eye as far forwards as
the ciliary circle, and is univerfally known by the name
of retina.

Though the fubftance of this pair of nerves feems
to be blended at the place where they are joined ;
yet obfervations of people whofe optic nerves were*
not joined, and of others who were blind of one eye,
from a fault in the optic nerve, or in thofe who had
one of their eyes taken out, make it appear, that
there is no fuch intimate union of fubftance ; the
optic nerve of the affe&ed fide only being wafted,
while the other was large and plump. And the fame
obfervations are contradi&ory to the doChine of a
decufiation of all the nerves (§ 8.) ; for the difeafe
could be traced from the affeCted eye to the origin
of the nerve on the fame fide. In many fifties, in-
deed, the doCtrine of decufiation is favoured ; for
their optic nerves plainly crofs each other, without a-
ny union at the part where they are joined in men
and moft quadrupeds.

Thefe people whofe optic nerves were not joined,
having neither feen objc&s double, nor turned their
eyes different ways, is alfo a plain proof, that the
conjunction of the optic nerves will not ferve to ac-
count for either the uniform motions of our eyes,
or our feeing objeCts fingle with two eyes, though it
may be one caufe of the remarkable fympathy of the
one eye with the other in many difeafes.

The retina of a recent eye, without any prepara-
tion, appears a very fine web, with fome blood-
veflels coming from its centre to be diftributed on it ;
but after a good injeCtion of the arteries that run in
the fubftance of this nerve, as is common to other
nerves, it is with difficulty that we can obferve its
nervous medullary fubftance. — The fituation of thefe

vefiels

Of the PARTICULAR NERVES. 285

veflels in the central part of the optic nerve ; the
want of medullary fibres here, and the firmnefs of
this nerve before it is expanded at its entry into the
ball of the eye, may be the reafon why we do not
fee fuch bodies, or parts of bodies, whofe pi£lure falls
on this central part of the retina. An inflammation
in thofe arteries of the retina , which feveral fevers
and an ophthalmia are generally attended with, may
very well account for the tendernefs in the eyes, and
inability to bear the light, which people have in
thefe difeafes. — The over-diftenfion of thefe veflels
may likewife ferve to account for the black fpots ob-
ferved on bright coloured bodies efpecially, and for
that fmoaky fog through which all obje£ls are feen
by people in fome fevers. — If thefe veflels lofe their
tone, and remain preternaturally diftended, no ob-
jects afleft our retina , though the eye externally ap-
pears found ; or this may be one caufe of an amauro-
fs or gutta ferena. — From a partial diftenfion of thefe
veflels, or paralyfts of a part of the retina , the central
part, or the circumference, or any other part of ob-
jects, may be loft to one or both eyes.

The THIRD PAIR rife from the anterior part
of the procejjiis annularis , and, piercing the dura ma-
ter a little before, and to a fide of the ends of the
pofterior clinoid procefs of the fphenoid bone, run a-
long the receptacula , or cavernous ftnufes , at the fide of
the ephippium , to get out at the foramina lactra ; af-
ter which, each of them divides into branches, of
which one, after forming a little ganglion, is diftri-
buted to the globe of the eye; the others are fent to
the mufculus rehlus of the palpebra, and to the attol-
lens , adduBor, deprimens , and oldiquus minor mufcles
of the eye-ball. Thefe mufcles being principal in-
ftruments in the motions of the eye-lid and eye-ball,
this nerve has therefore got the name of the motor
eculi. — I have frequently obferved in convulfions the
ty e-lids widely opened, the cornea turned upward and
outwards, and the eye- balls funk in the orbit ; which
well deferibed the conjunct aftion of the mulcles

which

286 Of the PARTICULAR NERVES.

which this pair of nerves ferves — The diftenfion of
a confiderable branch of the carotid, which pafles o-
ver this nerve near its origin on each fide, may pof-
fibly be the reafon of the heavinefs in the eye-lids
and eyes, after drinking hard, or eating much.

lhe FOURTH PAIR , which are the fmallefl
nerves of any, derive their origin from the back-part
of the bafe of the tejies ; and then making a long
courfe on the fide of the annular protuberance, enter
the dura water a little farther back, apd more exter-
nally than the third part, to run alfo along the recep-
tacu/a, to pafs out at the foramina larera, and to be
entirely fpent on the mufculi trochleares , or fuperior
oblique mufcles of the eyes. Thefe mufcles being
employed in performing the rotatory motions, and
the advancement of the eye-balls forward, by which
feveral of our paflions are exprefied, the nerves that
ferve them have got the name of PATHETICI. —
Why thefe fmall nerves fhould be brought fo far to
this mufcle, when it could have been fupplied eafily
by the motor oculi , I know not.

The FIFTH PAIR are large nerves, riling from
the annular procclles where the medullary proctfles
of the cerebellum join in the formation of that tuber t
to enter the dura mater near the point of the pe-
trous procefs of the temporal bones; and then fink-
ing clofe by the receptacula at the Tides of the fella
Turcia , each becomes in appearance thicker, and goes
out of the fkull in three great branches.

'The fiill branch of the fifth is the OPHTHAL-
MIC, which runs through the foramen lacerum to the
orbit, having in its palfage thither a connection with
the fixth parr. It is afterwards diftributed to the
ball of the eye with the third, to the nofe, along
with the olfadlory, which the branch of the fifth that
pafi’es through the foramen orbitarium Internum joins^
as was already mentioned in the defeription of the
firft pair. This ophthalmic branch likewife fupplies
the parts -at the internal canthus of the orbit, the
glandula lacrymalis, fat, membranes, mufcles, and te-
guments

Of the PARTICULAR NERVES. 287

foments of the eye-lids ; its longeft fartheft extend-
ed branch palling through the foramen fuperciliare of
the os frontis , to be diftributed to the forehead.

The fmall fibres which this firft branch of the fifth
and the third pair of nerves fend to the eye-ball, be-
ing fituated on the optic nerve, and, after piercing
the fclerotic coat, running along the choroid coat on
the outfide of the retina in their courfe to the uvea
or iris, may be a caufe of the fympathy between the
optic nerve and the uvea; by which we more readily
acquire the habit of contracting the iris, and there-
by leflen the pupil, when too ftrong light is exclud-
ed ; and, on the contrary, enlarge the pupil, when
the light is too faint. — This, with the fympathy
which mull arife from fome of the nerves of the
membrane of the noftrils, being derived from this
firft branch of the fifth pair of nerves, may alfo be
the caufe, why an irritation of the return, by too
ftrong light, may produce fneezing, as if a Jiimulus
had been applied to the membrane of the nofe it-
felf ; — why prefling the internal cantkus of the or-
bit, fometimes ftops fneezing ; — why irritation of the
nofe or of the eye caufes the eye-lids to (hut con-
vulfively, and makes the tears to flow plentifully ;
and why medicines put into the nofe, do often great
fervice in difeafes of the eyes. — In the megrim, all
the branches of the nerve difcover themfelves to be
affected : For the forehead is racked with pain, the
eye-ball is pained, and feels as if it was fqueezed,
the eye-lids fhut convulfively, the tears trickle down,
and an uneafy heat is felt in the nofe. Hence we
can undcrftand where external medicines will have
the beft effe£t, when applied to remove this difeafe,
to wit, to the membrane of the nofe, and to the
forehead ; — why alternate preflure near the fuperci-
liary hole of the frontal bone, or fneezing, fome-
times gives immediate relief in the megrim; — why
the fight may be loft by an injury done to the fupra-
criitar branch ; — how it may be reftored by agitation
of that branch of this nerve.

The

288 Of the PARTICULAR NERVES.

The fecond branch of the fifth pair of nerves may
be called MAX ILL AR IS SUPERIOR, from its
ferving principally the parts of the upper jaw. It
goes out at the round hole of the fphenoid bone, and
lends immediately one branch into the channel on
the top of the antrum maxillare ; the membrane of
which and the upper teeth are fupplied by it in
its paffage. As this branch is about to go out at
the foramen orbitarium externum , it fends a nerve
through the fubftance of the os maxillare to come out
at Stead’s dudl, to be diftributed to the fore-part of
the palate ; and what remains of ?t efcaping at the
external orbitar hole, divides into a great many
branches, that fupply the cheek, upper lip, and no-
ftril. — The next considerable branch of the juperior
maxillary nerve, after giving branches which are re-
flected through the fixth hole of the fphenoid bone, to
join the intercoftal where it is palling through the
fkull with the carotid artery, and the pdrtio dura of
the feventh pair, as it pafl'es through the os pctrofum,
is lent into the nofe by the hole common to the pa-
late and fphenoidal bone ; and the remaining part of
this nerve runs in the palato-maxillaris canal, giving
off branches to the temples and pterygoid mufcles,
and comes at laft into the palate to be loft. — Hence,
the ach in the teeth of the upper jaw occafions a
gnawing pain, deep-feated in the bones of the face,
with fwelling in the eye-lids, cheek, nofe, and upper
lip •, and, on the other hand, an inflammation in thefe 1
parts, or a megrim, is often attended with {harp pain
in the teeth. — Hence, an obftrudion in the duct of
the maxiilary fin us, which obliges the liquor fecreted
there to find out a preternatural route for itfelf, may
be occafioned by the pain of the teeth. — Hence, the
upper lip often fufFers when the palate or nofe is ul-
cerated.

The third or MAXILLA RIS INFERIOR branch
of the fifth pair going out at the oval hole of the
fphenoid bone, ferves the mufcles of the lower jaw,
and the mufcles fituated between the os hyoides and

jaw : .!

Of the PARTICULAR NERVES. 2S9

jaiu : All the falivary glands, the amygda /<*, and the
external ear, have branches from it : It has a large
branch loft in the tongue, and fends another through
the canal in the fubftance of the lower jaw to fervr
all the teeth there, and to come cut at the hole in
the fore-part of the jaw, to be loft: in the chin and
under-lip. — Hence, a convulfive contraction of the
mufcles of the lower jaw, or the mouth’s being in-
voluntarily ftiut, a great flow of fpittle or falivation,
a pain in the ear, efpecially in deglutition, and a
fwelling all about the throat, are natural coniequen-
ces of a violent irritation of the nerves of the lower
teeth in the tooth-ach ; and pain in the teeth and
ear, is as natural a confequence of an angina. — Hence,
alternate preflure on the chin may fometimes relieve
the violence of a tooth-ach. — Hence, deftroying the
nerves of a tooth by actual or potential cauteries, or
pulling a carious tooth, fo often removes immediate-
ly all thefe fymotoms. — Hence, no cure is to be
found for fome ulcers in the upper or lower jaw, but
by drawing a tooth. — Hence, in cancers of the up-
per lip, the falivary glands are in danger of being af-
fected, or the difeafe may be occafioned to the lip bv
its beginning in the glands. — Perhaps the fympathy
of the organs of tailing and fuelling may, in fome
meafure, depend on their both receiving nerves from
the fifth pair.

The SIXTH PA IR , which is the fmalleft except
the fourth, fifes from the fore-part of the corpora py-
ramidalia ; and each entering the dura mater fome
way behind the pofterior clinoid procefs of the fphe-
noid bone, has a long conrfe below that membrane,
and within the receptaculum at the fide of the fella
Turcica , where it is immerfed in the blood of the ic-
ccptacle ; but for what purpofe I am ignorant. It
goes afterwards out at the foramen lacerum into the
orbit, to fevve the abduCtor mufcle of the <-ve. — ri.
defeCl in this nerve may therefore be one cauie of a
Jirabiftnus. — In the paflage of this nerv. below the
dura mater , it lies very contiguous (9 the internal ca-

R b jotid

zpo Of the PARTICULAR NERVES.

rotid artery, and to the ophthalmic branch of the fifth
pair of nerves. At the place where the fixth pair is
contiguous to the carotid, a nerve either goes from
each of them in an uncommon way, to wir, with the
angle beyond where it rifes obtufe, to defeend with
the artery, and to form the beginning of the inter-
coftal nerve, according to the common defeription ;
or, according to other authors, this nerve comes up
from the great ganglion of the intercojlnl , to be joined
to the fixth here.

The arguments for this latter opinion are, That,
according to the common doCtrine, this beginning of
the intercoftal nerve, as it is called, would rife in a
manner not fo ordinary in nerves. In the next place,
it is obferved, that the fixth pair is larger nearer to
the orbit, than it is before it comes to the place
where this nerve is faid to go off; and therefore, it
is more probable, that it receives an addition there,
lather than gives off a branch. Lnjlly , It is found,
that upon cutting the intercoftal nerves of living ani-
mals, the eyes plainly were affeCtied ; they loft their
bright water ; the gum, or gore, as we call it, was'
feparated in greater quantity; the pupil was more
contracted ; the cartilaginous membrane, at the in-
ternal cant bus, came more over the eye ; and the eye-
ball itfelf was diminifhed.

'To this it is anfwered, in defence of the more com-
mon doCtrine, i ft, That other branches of nerves
go off in a reiieCted way, as well as this does, fup-
pofing it to be the beginning of the intercoftal ; and
that the reflection would rather be greater, if it is
thought to come up from the intercoftal to the fixth.
idly, It is denied that this nerve is for ordinary thick-
er at its fore than its back part; and if it was fup-
pofed to be thickeft nearer to the orbit, the conclufion
made above could not be drawn from this appearance,
becaufe other nerves enlarge fometimes where there
is no addition made to them, as in the inflance al-
ready mentioned of the trunk of the fifth pair while
below the dura mater. 3 dly} The experiments on

living

Of the PARTICULAR NERVES. 2 91

living animals fliew indeed, that the eyes are afFcdl -
e<l, upon cutting the intercoftal nerve, but not in tne
way which might have been expected, if the b.ta-
rofial had furniihed fuch a (hare of the_ nerve that
goes to the adduBor mufcle of the eye ; for it might
have been thought, that this mufcle would have been
fo much weakened immediately upon cutting the in-
tercojlnl, that its antagonift the adduStor would have
greatly prevailed over it, and have turned the eye
ltrongly in towards the nofe 5 which is not faid to be
a confequence of this experiment. So tnat the argu-
ments are Hill equivocal ; and more obfervations and
experiments mall be made, before it can be deter-
mined with certainty, whether the fixth pair gives cr
receives a branch here. In the mean time, I (hail
continue to fpeak about the origin of the intcrcojlal
with the generality of anatomifts.

At this place where the intercoftal begins, the fifth
pair is contiguous and adherent to the (ixth ; and it
is generally faid, that the ophthalmic branch of the
fifth gives a branch or two to the beginning of the
intercoftal, or receives fuch from it. Others deny
any fuch communication between them ; and thole
who affirm the communication confels, that in lome
fubjedls they could not fee it. After examining the
nerves here in a great many fubjedls, I cannot deter-
mine whether or not there are nervous filaments
going from the one to the other. Sometimes I have
thought that 1 traced them evidently •, at other times I
obferved, that what I difle&ed for nervous filaments
was collapfed cellular fubftance *, and in all the fub-
jedh; where I had pufhed an injtdfion fuccefsfully in-
to the very fmall arteries, I could only obferve a plex-
us of vefi'els conncdting the one to the other. In am*
of thele ways, however, there is as much connection
as, we are allured fiom many experiments and ob-
fervations on other nerves, is fufficient to make a verv
great fympathy among the nerves here. Poftibly the
appearances in the eyes of dogs, whofe intercoftal
nerves were cut, might be owing to this fympathy.

B b 2 ‘ The

292 Of the PARTICULAR NERVES.

The SEVEN'! H PAIR comes out from the late-
ral part of the annular procefs, behind where the
medullary procefs of the cerebellum are joined to that
tuber ; ai'.d each being accompanied with a larger ar-
tery than mofl other nerves, enters the internal meatus
audit arms, where the two large bundles of fibres, of
which it appeared to confift within the fcull, foon
feparate from each other; one of them entering by
feveral fmall holes into the vejlib/c, cochlea, and femi-
circular canals, is ftretched on this inner camera of the
ear in a very foft pulpy fubltance ; and being never
feen in the form of a firm cord, fuch as the other
parcel of this and mod other nerves become, is called
PORTIO MOLLIS of the auditory nerve.

The other part of this feventh pair pafles through
Galen's foramen cacutn, 01 Fallopius's aquxducl, in its
crooked pnliage by the fide of the tympanum ; in
which paff.ige, a nerve fent from the lingual branch
of the inferior maxillary nerve, along the outfide of
the tuba Eujlachiana, and crofs the cavity of the
tympanum, where it has the name of chorda iympani,
is commonly laid to be joined to it. The very acute
angle which this nerve makes with the fifth, or the
hidden violent refledlion it would fuffer on the fup-
pofirion of its coming from the fifth to the feventh,
appears unufual; whereas, if we fuppofe that it comes
from the feventh to the fifth, its courfe would be
more in the ordinary way, and the chorda tympani
would be cfleemed a branch of the feventh pair going
rojoin the fifth, the fize of which is increafed by
this acquifition. This l'mnller bundle of the lcventh
gives branches to the mufcles of the malleus, and to
the. aura mater, while it pafles through the bony
crooked canal, and at lafl comes out in a firm chord
named PORTIO DURA, nt the end of this canal,
between the Jly/oid and majloid proceffes of the tem-
poral bone, giving immediately filaments to the little
oblique muicles of the head and to thole that rife
from the it y bid proccfs. It then pierces through the
parotid gland, and divides into a great many branches, ;

which I

Of the PARTICULAR NERVES.

*03

which are difperfed in the mufcles and teguments
that cover all the fide of the upper part of the neck,
the whole face and cranium , as far back as the tem-
ples, including a confiderable part of the external
ear. Its branches having thus a confiderable con-
nection with all the three branches of the fifth pair,
and with the fecond cervical, occafion a confiderable
fympathy of thefe nerves with it. — Hence in the
tooth-ach, the pain is fomelimes very little in the af-
fected tooth, compared to what it is all along the fide
of the head, and in the ear. — Hence probably the
relief of the tooth-ach from blifters applied behind oi‘
before the ear, or by a hot iron touching the ar.tiMi:.
of the ear. — By this communication or connection
pcfiibly too it is, that a vibrating firing held between
one’s teeth, gives a (Irong idea of found to the perfon
who holds it, which nobody elfe can percci’. c. —
Perhaps too the diftribution of this nerve occafions
the head to be fo quickly turned upon the imprdfion
of found on our ears.

The EIGHTH PAIR of nerves rife from the lateral
bafes of the corpora olivaria in difgregated fibres; and
as they are entering the anterior inteinal part of the
holes common to the os occipitis and temporum, each
is joined by a net ve which afeends within the dura
mater from the tenth of the head, the firfl, fecond
and inferior cervical nerves: This every body knows
has the name of the NERFUS ACCESSORIUS.
When the two get out of the fcull, the acc. Jbrius fe-
parates from the eighth, and, defeending obliquely
outwards, pafies through the Jierno - majloidrus mufcle,
to which it gives branches, and afterwards terminates
in the trapezius and rhomboid mufcles of the Jcapula.
In this courfe it is generally more or lefs joined by the
fecond cervical nerve. Why this m rve, and feveral
others which are dillributed to mufcles, arc made to
pierce through mufcles, which they might have only
palled near to,- I do not know.

The large eighth pair , foon after its exit, gives
nerves to the tongue, larynx, pharynx , and "garAion

^ b 3 of

^94 Of the PARTICULAR NERVES.

of the interccjial nerve, and being. disjoined from the
ninth and jntercoftal, to which it adheres clofely fome
wav, rims ftraight down the neck behind the inter-
nal jugular vein, and at the external fide of the caro-
tid artery. As it is about to enter the thorax, a large
nerve goes off from the eighth of each fide : This
branch of the right- fide turns round from the fore
to the back-part of the fubclavi'an artery, while the
branch of the left-fide turns round the great curve of
the aorta, and both of them mounting up again at
the fide of the aejbphagus , to which they give branches,
are loft at laft in the larynx. Tbefe are called the
RECURRENT nerves, which we are defired to fhun
in the operation of bfonrhotomy , though their deep fi-
tuaticn prote£ls them fufticiently. — The mufcles of
the larynx, being in a good meafure fupplied with
nerves fiom the reenrrems, it is to be expe&ed, that
the cutting of them will greatly weaken the voice,
though it will not be entirely loft, fo long as the fuperior
branches of the eighth pair are entire. — Why the re-
current iierves rife to low from the eighth pair to go
round a.large artery, and to have fuch a long courfe
upwards, I know not.

The eighth pair, above and at or near the place
where the recurrent nerves go off from it, or frequent-
ly the recurrents themfelvrs, fend oft fmall nerves to
the pericardium, and to join with the branches of the
intcrcoftal that are diflributcd to the heart} but their
fize and fituation are uncertain.

After thefe branches are fern off, the par vagum on
each fide defeends behind the great branch of the tra-
chea, and gives numerous filaments to the lungs, and
feme ro the hearr in going to the aefophagus. lhe
ore of tl e left fide running on the fore part of the
ipjlphagui, communicates by feveral branches with
the rignt one in its defeen' to bt diftributed to the
ftomach : : he right one gets behind the oefophagris,
where it fplits and rejoins feveral times before it
arrives at the fto-oach. to which it fends nerves } and
then being joined by one or more branches from the

Of THE PARTICULAR NERVES 295

left-trunk, they run towards the eseliac artery, there
to join into the great femilunar ganglion formed by the
two intercoftals.

From the difiribution.of this/><7>- vngum , we may
learn how tickling the fauces with a feather or any fuch
fubftance, excites a tinufea and inclination to vomit ; —
why coughing occafions vomiting, or vomiting raifes a
Cough. — Hence we fee how the nervous afihva and
the tujjis convulftva , chincough, are attended with a
ftrakening of the glottis 5 — why food difficult to digeffc
occafions the ajlhnia to weakly people , and why eme-
tics have frequently cured the njllma very lpeedily ; —
why an attempt to vomit is fometimes in danger of
fuft'ocating ajlhmatic people ; — why the fuptrior ori-
fice of the Itomach is fo fenfiblc, as to be looked on
as the feat of the foul by fonie ; — why people fubjeft
to diftenfions of the Itomach, have io often the l'tn-
fation of balls in their breads and throats ; — why the
globus hyfiericus is fo often attended with a violent
ftrangulation at the glottis.

1 he NINT H PAIR of nerves comes from the in-
ferior part of the corpora pyramideliat to go out of the
fcull at their proper holes of the occipital bone. Af-
ter their egrels they adhere for fome way firmly to
the eighth and intercoftal ; and then fending a btanch,
that in many fubje&s is joined with blanches of the
firll and iecond cervical nerves, to be diltiibuted to
the thyroid gland and mufcles on the fore-pan of the
trachea arteria, the ninth is lofl in the mufcles and
fubftance of the tongue. Some have thought this
nerve, and others have efteemed the third branch of
the fifth pair of nerves, to be the proper guftatory
nerve. I know no obfervation or experiments to
prove either opinion, or to allure us that both nerves
do not ferve tor tailing and for the motion of the
tongue.— May not the diflribution of this nerve to
the mulcles below as well as above the os hyoides ,
contribute to their adling more uniformly in dcpief-*
fing the lower jaw or head ?

The

296 Of. THE PARTICULAR NERVES.

The TENTH PAIR rifes in feparate threads from
the fules ot th e fpinal marrow , to go out between the
os occipitis and firjl vertebra of the neck. After each
of them has given banches to the great ganglion of
the intercoflal, 8th, 9th, and ift cervical nerves, it
is diflributed to the ftraight, oblique, and fome of
the extenfor mufcles of the head. Whether the name
of the tenth of the head, or of the firft vertebral,
ought to be given to this pair of nerves, is of no fuch
confcquencc as to deferve a debate, though it has
l'ome of the marks of the fpinal nerves, to wit, its
being formed of filaments proceeding from both the
fore and back part of the medulla , and a little gan-
glion being formed where thefe filaments meet.

In the defcription of the fixth pair, I followed the
ufual way of fpeaking among anatomifts, and called
that the beginning of the intercoflal nerve which
comes out of the fcull ; and therefore {hail here fob-
join a curfory defcription of this nerve, notwithfland-
ing its much larger part is compofed of nerves com-
ing out from the fpinal marrow. There is no greater
incongruity in point of method to fay, that the nerve
we are deferibing receives additions from others that
have not been deferibed, than it is to repeat in the
defcription of a great many nerves, that each of them
gives branches to form a nerve which we arc igno-
rant of ; which is all the difference between deferi-
bing the intercoflal before or after the fpinal nerves. ■

The branch reflected from the fixth pair, joined j
poffibly by fome filaments of the opththalmic branch
of the fifth, runs along with the internal carotid ar-
tery, through the crooked canal formed for it in the
temporal bone , where the little nerve is very foft and
pappy, and in feveral fubji£ls divides and unites a-
gain, and is joined by one or more branches from the
fifth, particularly of its fuperior maxillary branch
before it comes out of the fcull. May the ccmprtf-
fion of this nerve by the carotid artery when lb r< reli-
ed during th e. Jyfiole, contribute to the diajlole of the
heart ? As foon as the nerve cfcapes out cf this beny

canal,

Of the PARTICULAR NERVES. 297

canal, it is connected a little way with the eighth
and ninth ; then feparating from thefe, afteF feeming
to receive additional nerves from them, it forms a
hrge ganglion, into which branches from the tenth of
the head, and from the firft and fecond cervical en-
ter. From this ganglion the nerves come out again
fmall to run down the neck along with the carotid
artery, communicating by branches with the cervi-
cal nerves, and giving nerves to the mufcles that
bend the head and neck. As the intercoJJal is about
to enter the thorax , it forms another ganglion, from
which nerves are fent to the trachea and to the heart j
thefe dcfigned for the heart joining with the branches
of the eighth, and mod of them palling between the
two great arteries and the auricles, to the fubftance
of that mufcle. The intercoftal after this confifting
of two branches, one going behind, and the other
running over the fore-part of the fubclavian artery,
forms a new ganglion where the two branches unite
below that artery, and then defcendjng along the
fules of the vertebra of the tlxrax, receives branches
from each of the dorfal nerves ; which branches ap-
pearing to come out between the ribs, have given the
name of intercoftal to the whole nerve. Where the
addition is made to it from the fifth dorfal nerve, a,
branch goes off obliquely forwards ; which being
joined by fuch branches from the fixth, feventh,
eighth, and ninth dorfal, an anterior trunk is formed,
and paft'es between the fibres of the appendix mtefculofa,
of the diaphragm, to form, along with the other in-
tercoftal and the branches of the eighth pair, a large
femilunar ganglion, fituated between the cseliac and
fuperior mei'enteric arteries ; the roots of which are
as it were involved in a fort of nervous net-work of
this ganglion, from which a great number of very
fm?.ll nervous threads run out to be extended on the
furface of all the branches of thofe two arteries, fo a's
to be eafily feen when any of the arteries are ftietch-
ed, but not to be railed from them by difTetHon : and
thus the liver, gall- bladder, duodenum, pancreas, fpleen ,

jejunum.

298 Of the PARTICULAR. NERVES.

jejunum , ilium , and a large (hare of the xolon , have
their nerves fent from this great /»/<7r ganglion or //£>.v-
wr. May the perirtaltic motion of the inteftines de-
pend in lome meafure on the pafl'age of the intercoil d
nerves through the diaphragm ?

Several fibres of this ganglion, running down upon
the aorta , meet with other nerves fent from the pof-
terior trunk of the intercortal, which continues its
courfe along the fides of the vertebra ;*they fupply the
glandul* renales , kidneys, and tejles in men, or ovaria
in women ; and then they form a net-work upon the
inferior mefenteric artery, where the nerves of the two
fides meet, and accompany the branches of this arte-
ry to the part of the colon that lies in the left fide of
the belly, and to the reflum, as far down as to the
lower part of the pelvis.

The intercortal continuing down by the fide of the
vertebra of the loins, is joined by nerves coming from
between thefe vertebra , and fends nerves to the or-
gans of generation and others in the pelvis, being
even joined with thofe that are fent to the inferior
extremities.

I he almoft uniterfal connexion and communica-
tion which this nerve has with the other nerves of
the body, may lead us to underftand the following,
and a great many more phanomena : — Why tickling
the nofe caufes lneezing. — AVhy the too great quan-
tity of bile in the cholera occafions vomiting as well
as purging. — Why people vomit in colics, in inflam-
mations, or other irritations of the liver, or of the
dutrts going from it and the gall-bladder. — Why a
flone in the kidneys, or ureters, or any orher caufe
irritating thofe organs, fliould fo much more frequent-
ly bring on vomiting and other diforders of the fto-
mach, than the (tone, or any other- (Emulating caufe
in the bladder does. — Why vomiring is a fymptom of
danger after child birth, iithotomy, and other opera-
tions on the parts in the pelvis. — Why the obltruc-
tions of the menfes are capable of occafioning ftrangu-
lations, belching, colics, ftomach-aches, and even

convulfions

Of THE PARTICULAR NERVES. 299

convulfions in the extremities. — Why veficatories, ap-
plied from the ears to the clavicles of children labour-
ing under the tujfis convulfiva , are frequently of great
fervice. — Why worms in the ftomach or guts excite
an itching in the nofe, or grinding of the teeth. —
Why irritations in the bowels or the bel'y occafion
fometimes univerfal convuifions of the bodv.

The fpinal nerves rife genet ally by a number of
difgregated fibres from both the fore and back-part of
the medulla fpinalis, and foon after form a little knot
or ganglion, where they acquire drong coats, and
are extended into firm cords. 1 hey are didinguifhed
by numbers, according to the vertebrae from between
which they come out ; the fuperior of the two bone6
forming the hole thiough which 1 hev pafs, being the
one from which the number is applied to each nerve.
There are generally laid to be thirty pair of them ;
feven of which come out between the vertebra of the
tieck, twelve between thofe of the back, five between
thofe of the loins, and fix from the falfe vertebra.

The FIRST CERVICAL pair of nerves comes
out between the fird and fecond vertebra of the neck ;
and having given branches to join with the tenth pair
of the head, the fecond cervical and intercodal, and
to ferve the mufcles that bend the neck, it fends its
larged branches backwards to the extenfor mufcles of
the head and neck; fome of which piercing through
.thefe mufcles, run up on the ccciput to be loft in the
teguments here ; and many fibres of it advance fo
far forward as to be conne&ed with the Jibrils of the
fird branch of the fifth pair of the head, and of the
portio dura of the auditory nerve. — Hence poflibly it is
that a clavus kyjlericus changes fuddenlv fometimes
from the fore-head to a violent pain and fpafm in the
back-part of the head and n;ck.

The SECOND CERVICAL is foon joined by
fome branches to the ninth of the head and intercod-
al, and to the fird and third of the neck ; then has a
large branch that comes out at the exterioi edge of
thcjler no-majioideus mufcle, where it joins with the

accejforius

3oo Of the PARTICULAR NERVES.

a cceforius of the eighth pair ; and is afterwards dif- :
tributed to the platyfma myoides , teguments of the
fide of the neck and 'head, parotid gland, and exter-
nal ear, being connedted to the portio dura of the au-
ditory nerve, and to the firft cervical. The remain-
der of this fecond cervical is fpent on the levator fra-
pula and the extenfors of the neck and head. Gene-
rally a large branch is here fent off to join the accrf-
f.jrias of the eighth pair, near the fuperior angle of
the Jcdpula.

To the irriration of the branches of this nerve it
probably is, that, in an inflammation of the parotid
gland, the neck is pained fo far down as the clavicle,
the head is drawn towards the fhoulder of the afiedt-
ed fide, and the chin is turned to the other fide. —
In opening the external jugular vein, no operator can
promife hot to touch fome of the cutaneous branches
of this nerve with the lancet •, which occafions a lharp
pricking pain in the mean time, and a numbnefs oi
the (kin near the orifice for fome time after.

The THIRD PAIR of the neck paffes out be-
tween the third and fourth cervical vertebra •, having

immediately a communication with the fecond, and

fending down a branch, which being joined by a
branch from the fourth cervical, forms the PHkh-
NIC nerve. This defending enters the thorax be-
tween the fuhclavian vein and artery ; and then bc-
in" received into a groove formed for it in the pertcar-
diuiity it has its courfe along this capfula of the heart,
tili it is loft in the middle part of the diaphragm.
The right phrenic has a ftraight courfe ; but the left
one is obliged to make a confiderable turn outwards
to xo over the prominent part of the pericardium,
■where the point of the heart is lodged. Hence in
violent palpitations of the heart, a pungent acute
pain is felt near the left orifice of the ftomach.— I he
middle of the diaphragm icarce could have been inp-
plied by any other nerve which could have had tuch a

ftraight courle as the phrenic has. If the fubclavian
6 artery

Of the PARTICULAR NERVES- 301

artery and vein have any efTe£I upon this nerve, I do
not know it.

Tiie other branches of the third cervical nerve are
diftributed to the mufcles and teguments at the lower
part of the neck and top of the fhoulder. No won-
der then that an inflammation of the liver or lpleen,
an abfcefs in the lungs adhering to the diaphiagm, or
any other caufe capable of irritating the diaphragm,
fhould be attended with a (harp pain on the top of the
fhoulder, as well as wounds, ulcers, fcsV. of this
mufcle itfelf. — If the irrit«tion of this mufcle is very
violent, it may occafion that convulfive contraction
of the diaphragm which is called an hiccough ; and
therefore an hiccough in an inflammation of the liver
has been j u fitly declared to be an ill lymptom.

An irritation of the thoracic nerves which produces
fneezing, may fometimes free the phrenic nerves from
any fpafm they occafion ; fo that fneezing fometimes
takes away the hiccough ; and a derivation of the
fluid of the nerves any other way may do the fame
thing : Or the hiccough may alfo he fometimes cured,
by drawing up into the nofe the fmoak of burning
paper or other acrid fumes, fwallowing pungent or
aromatic medicines, and by a furprife, or any other
ilrong application of the mind in thinking, or in dif-
tinguifhing objects : Or, when all thefe have failed,
it has been put away by the briik Jlimulus of a blifter-
ing plafler applied to the back.

The FOURTH CERVICAL nerve, after fending
off that branch which joins w’ith the third to form
the phrenic, and bellowing twigs on the mufcles, and
glands of the neck, runs to the arm-pit, where it
meets with the FIFTH , SIXTH , and SEVENTH
cervicals, and FIRST DORSAL, that efcape in the
interfaces of the mufeuli fcaleni, to come at the arm-
pit, where they join, feparate, and rejoin, in away
fcarce to be rightly exprefled in words ; and after gfv_
ing fcveral confiderable nerves to the mufcles and te-
guments which cover the thorax , they divide into fe-
veral branches, to be diftributed to all the parts of

^ c the

302 Of the PARTICULAR NERVES.

the fapcrior extremity. Seven of thefe branches I
Itiau deicribe under particular names.

f. SCAPULAR IS runs ftraight to the cavitas femi-
lunata of the upper co/la of the fcapula, which is a
hole in the recent fubjeft by a ligament being extend-
ed from one angle of the bone to the other, giving-
nerves in its way to the mufcles of the fcapula. When
it has palfed this hole, it fupplies the fupra fpinatus
mufcle ; and then defcending at the anterior root of
the fpine of the fcapula, it is loft in the other mufcles
that lie on the dorfum of that bone.

2. ARTICULARIS finks downwards at the axilla ,
to get below the neck of the head of the os humeri ’
and to mount again at the back-part of it ; fo that it
aim oft furrounds the articulation, and is diftributed
to the mufcles that draw the arm back, and to thofe
that raife it up.

3. CUTANEUS runs down the fore-part of the
arm near the fkin, to which it gives off branches ;
and then divides on the infide of the fore-arm into
feveral nerves, which fupply the teguments there,
and on the palm of the hand. — In opening the bafilic
vein of the arm, at the ordinary place, the fame
fymptoms are fometimes produced as in opening the
external jugular vein, and from a like caufe, to wit,
from hurting a branch of this cutaneous nerve with
the lancet.

4. MUSCULO- CUTANEUS, or perforans Cajferi,
paffes through the coraeo-brachialis mufcle ; and after
fupplying the biceps flexor cubiti and bracb'ueus interims ,
paffes behind tbe tendon of the biceps, and over the
cephalic vein, to be bellowed on the teguments on
the outfide of the fore-arm and back of the hand. —
This nerve is fometimes hurt in opening the cephalic
vein, and caufes pain and numbnels for a fhort time.

5. MUSCULARIS has a fpiral courfe from the
axilla, under the os humeri , and backward to the ex-
ternal part of that bone, fupplying by the way the
extenfor mufcles of the fore-arm, to which it runs
between the two brachiai mufcles, and within the

fupinator

Of the PARTICULAR NERVES. 303

fupinator radii lengus. — At the upper part of the :C'rp~
arm, it fends off a branch, which accompanies the
fupinator longus till it comes near the wrift, where it
paffes obliquely over the radius , to be loft in the fcacic
of the hand and fingers. — .1 he principal part of this
nerve pierces through the fupinator radii brevis , to
ferve the mufcles that extend the hand and fingers,
whofe actions are not injured when the fupinator arfh.

6. ULNARIS is extended along the infide of the
arm, to give nerves to the mnfcles that extend the
fore-arm and to the teguments of the elbow : To-
wards the lower part of the arm, it Hants a little
backward to come at the groove behind the intern;**
condyle of the os humeri , through which it runs to
the ulna : In its courfe along this bone, it feives the
neighbouring mufclfes and teguments ; and as it comes
near the wrift, it detaches a branch obliquely over the
ulna to the back of the hand, to be loft in the convex
part of feveral fingers. Ihe larger part of the nerve
goes ftraight forward to the internal fide of the es pi-
Jiforme of the wrift ; where it fends off a branch
which finks under the large tendons in the palm, to
go crofs to the other fide of the wrift, ferving the
mufeufi lumbricales and intercjfci , and at laft terminat-
ing in the fliort mufcles of the thumb and fore-fin-
ger. What remains of the ulnar nerve, after fupply-
ing the fliort mufcles of the little finger, divides into
three branches; whereof two are extended along the
fides of the fheath of the tendons of the flexors of
the little finger, to furnifh the concave fide of that
finger; and the third branch is difpofed in the fame
way upon the fide of the ring finger next to the little
finger.

When we lean or prefs on the internal condyle of
the os humeri , the numbnefs and prickling we fre-
quently feel, point out the courfe of this nerve. I
have feen a weaknefs and atrophy in the parts which
I mentioned this nerve to be lent to, after a wound
in the internal lower part of the arm.

Cc 2

7. RA-

3°4 Or the PARTICULAR NERVES.

7. RJDIJLIS accompanies the humeral artery
to 'he bending of the elbow, ftrving the flexors of
the cuhir in its way ; then palling through the prona-
tov radii teres mufcle, it gives nerves to the mufcles
on t ne fore- part of the fore-arm, and continues its
coiiife near to the radius , befloaing branches on the
circumjacent mufcles. Near the wrift, it fomerimes
gives off a nerve which is diftiibuted to the back of
the hand, and the convex part of the thumb and fe-
veral of the fingers, inftead of the branch of the
mu feu Jar. 1 he larger part of this nerve, pafftng be-
hind the annular ligament of the wrift, gives nerves
to the fl.ort mulclcs of the thumb ; and afterwards
fends a branch along each fide of the lheath of the
tendons of the flexors of the thumb, fore-finger,
mid- finger, ami one branch to the fide of the ring-
finger, next to the middle one, to be loft on the con-
cave fide of thofe fingers.

Though the radial nerve pafles through the prona-
tcr mufcle, and the mufcular nerve feems to be ftill
more unfavourably placed within the fupinator brevis ;
vet the a£lion of thefe mufcles does not feem to have
any effect in hindering the influence of thefe nerves;
lor the fingers or hand can be bended while pronation
i = performing vigoroufly, and they can be extended
y. bile fupination is exercifed.

The manner of the going off of thefe nerves of the
fi-\g both from the ulnar and radial, is, that a
fugle branch is fent from the ttunk to the fide of the
thumb and little finger fartheft from the other
fingers;, and all the reft are fupplietl by a trunk of a
nerve, v hich fplits into two fome way before it comes
as Tar as the end of the metacarpus , to run along the
fides of different fingers that aie neareft to each'
other.

It might have been obferved, that, in deferibing the
pofterior branches of the ulnar and mufcular nerve , I
did not mention the particular fingers, to the convex
part of which they are diftributed. My reafon for
this omiftion is, the uncertainty of their diftribution;

Of the PARTICULAR NERVES. * 305

for though fometimes thefe pofterior branches go to
the fame fingers, to #the concave part of which the
anterior branches of the ulnar and radial ' are tern,
yet frequently they are diftributed otherwife.

The fituation of thefe brachial nerves in the axilla*
may let us fee, how a weaknefs and atrophy may be_
brought on the arms by long continued preffure of
crutches, or fuch other hard fubftances on this part ;
and the courfe of them, from the neck to the arm,
may teach us, how much better effects vehcatories,
or ftimulating nervous medicines, would have, when
applied to the fkin, covering the tranfverfe proceffcs
of the vertebra of the neck, or at the axilla, than
when they are put between the fhoulders, or upon
the fpinal procefles, in convulfions or palfies of the
fuperior extremities, where a Jlimulus is required.

The TWELVE DORSAL nerves of each fide,
as foon as they efcape from between the vertebra , fend
a branch forward to join the intercoftal, by which a
communication is made among them all; and they
foon likewife give branches backwards to the mufcles
that raife the trunk of ’the body, their piincipal trunk
being extended outwards to come at the furrow in
the lower edge of each rib, in which they run toward
the anterior part of the thorax , between the internal
spid external intercoftal mufcles, giving off branches-
in their courfe to the mufcles and teguments ot the
thorax.

The FIRST dorfal, as was already obferved, is
particular in this, that it contributes to form the
brachial nerves ; and that the two branches of the in-
ter coital, which come down to the thorax , form a
^pnfiderable ganglion with it.

The SIX lower dorfal nerves give branches to the
diaphragm and abdominal mufcles.

The TWELFTH joins with the fnft lumbar, and
beftows nerves on the mufculus quadratus lumborum
and iliacus interna s.

May not the communications of all thefe nerves be
one rcafon, why the parts they ferve a£t fo uniform-

C c 3 ly.

3c6 Of the PARTICULAR NERVES.

ly and coiijun&ly in refpiration, and confpire toge-
ther in the convulfive motions pf coughing, fneez-
ihg, is‘c. — ! he twitching fpafms that happen fome-
times in different parts of the mufcles of the abdo-
men, by an irritation on the branches of the lower
dorfal nerves, are in danger of occafioning a miftake
in practice, by their refemblance to the colic, neph-
ritis, Ufa. — The communications of thefe lower ones
with the intercoftals may ferve to explain the violent
effort of the abdominal mufcles in a tenefmus and in
child bearing.

As the intercoflal is larger in the thorax than any
where elfe, and feenis to diminifh gradually as it a-
fcends and defends, there is caufe to fufpe£l, that
this is the trunk from which the fuperior and inferior
pairs are fent as branches.

The FITF. LUMBAR nerves on each fide com-
municate with the intercoflal and with each other,
and give blanches backwaids to the loins.

The FIRST communicates with the lafl dorfal,
feuds branches to the abdominal mufcles, to the pfoas
and iliacus , and to the teguments and mufcles on the
fore-part of the thigh ; while its principal branch
joins with the other nerves, to form the crural nerve.

The SF.COND LUMBAR netve paffes through
th ’‘pfoas mu[A’, and is diflributed nearly in the fame
wav as the former ; as is alfo the THIRD.

Branches of the fecond, third , and fourth, make up
one trunk, which runs along the fore-part of the
pelvis; and puTmg in the notch at the fore-part of
the great hole common to the os pubis and ifehium , is
fpent bn the adduflor multles, ano on the teguments
on the in fid- of 'he thigh This nerve is called the
OBTURATOR or POSTERIOR CRURAL
NERTE. •

Ry united branches from the firfi, fecond, third , and
■four'h lumbar nerves, a nerve is formed that runs a-
lony the pfoas tnufcle, toefcapc with the external iliac
veil' i s ut of the abdomen, below the tendinous ar-
cade of the external oblique mul'cle. This neve,

which

Of THE PARTICULAR NERVES. 307

which is named the INTERIOR CRURAL, is
diffributed principally to the rnufcles and teguments
on the fore-part of the thigh. A branch, however,
of this nerve runs down the infide of the leg to the
upper part of the foot, keeping near to the vena fa-
pheena ; in opening of -which with a lancet at the
ancle, the nerve is fometimcs hurt, and occafions
fharp pain at the time of the operation, and numb-
nefs afterwards.

The remainder of the fourth lumbar and the fifth
join in compofing the largeft nerve of the body *,
which is foon to be defcribed.

Whoever attends to the courfe of thefe lumbar
nerves, and of the fpermatic veffels and nerves upon
the p/oas mufcle, with the oblique paff ge of the ure-
ter over that mufcle, will not be furpriied, that when
a flcr.e is palling in this canal, or even when it is In-
flamed, the trunk of the body cannot be raided etcdh,
without great pain ; or that the fkin of the thigh be-
comes lets fenfible, and the thigh is drawn forward,
and that the teflicle often fwells and is drawn ccn-
vulfively towards the ring of the abdominal rnufcles.

The SIXTH PAIR of the falfe VERTEBRAL
confilt each of fmall pofterior branches lent to the
Lips, and of large anterior branches.

rl he firfi, fecond, and third, after coming through
the three upper holes in the fore- part of the os J'a -
crutn , join together with the fourth and filth of the
loins, to form the largell nerve of the body, which is
well known by the name of the SCIAl IC or 1SCHI-
AT1C nerve : This, after fending large nerves to the
different parts of the pelvis, and to the external paits
of generation, and the podex, as alfo to the muf-
cles of the hips, paffes behind the great tuber of the
os ifckium , and then over the quadrigemini rnufcles, to
run down near to the bone of the thigh at its hack-
part, giving off nerves to the neighbouring rnufcles
and teguments. Some way above the ham, where it
has name of the poplitaus nerve '.t lends eff a
large branch that paffes over the fibula, and finking

in

308 Of the PARTICULAR NERVES.

in among the mufcles on the anterior external part
of the leg, runs down to the foot, to be lofl in the
upper part of the larger toes, fupplying the neigh-
bouring mufcles and teguments every where in its
pafTage. The larger branch of the fciatic, after giv-
ing branches to the mufcles and teguments about the
ham and knee, and fending a large cutaneous nerve
down the calf of the leg, to be lofl at laft on the
outfide of the foot, and upper part of the leffer toes,
finks below the gemellus mufcle, and diflributes nerves
to the mufcles on the back of the leg; among which
it continues its courfc, till, palling behind the inter-
nal malleolus , and in the internal hollow of the cs cal-
chf it divides into the two plantar nerves : The in-
ternal of which is diftributed to the toes in the fame
manner that the radial nerve of the hand ferves the
concave fide of the thumb and fingers; and the ex-
ternal plantar is divided and diftributed to the foie of
the foot and toes,, nearly as the ulnar nerve is in the
palm of the hand, and in the concave part of the
lingers.

Several branches of thefe nerves, that ferve the in-
ferior extremities , pierce through mufcles.

By applying what was faid of the nerves in gene-
ral to the particular diftribution of the nerves of the
inferior extremities , we may fee how people with frac-
tured legs, efpecially where there are fplinters, fhould
be fubjedl to convulfive ftartings of the fra£lured
member. — Why, upon tying the blood vefl'els in an
amputation of the leg, the patients fhould fometimes
complain of violent pain in their toes ; — why fuch
patients lhould alfo be troubled with ftartings ; — why,
for a confiderable time after the amputation of the
difeafed limb, when the fuppuration is well advan-
ced, they fhould complain of pain in the lore whicli
occafioned the amputation.

The FOURTH, which, with the two following,,
is much fmaller than the three fuperior, foon is loft
ia the vefca urinaria and intejlinum rectum ,

The

Of the PARTICULAR NERVES. 309

The FIFTH comes forward between the extremi-
ty of the os facrurn and coccygis , to be diftributed prin-
cipally to the levatores am.

The SIXTH , which fome think to be only a pro-
duction of the dura mater, advances forward below
the broad fhoulders of the firft bone of the os coccygis ,
and is Jolt in the fphinBer am, and teguments cover-
ing it.

The branches of the four laft cervical nerves, and
of the firft dorfal, which are beftowed on the fuperior
extremities, and the two crurals, with the fciatic,
which are diltributed to the inferior extremities, are
much larger proportionally to the parts they ferve,
than the nerves of the trunk of the body, and efpe-
cially of the vifeera, are •, and for a very good reafon,
that, in the molt common neceffary adlions of life, a
fufficicnt quantity of fluid, on which the influence
of nerves lee ms to depend, may be fupplied to the
mufcles there, which are obliged to perform more
frequent and violent contractions than any other parts
do. — The flze of the nerves of the inferior extremities
fcems larger proportionally than in the fuperior ex-
tremities \ the inferior extremities having the weight of
the whole body to fullain, and that frequently at a
great difadvantage. — What the effeCt is of the nerves
here being injured, we fee daily, when people hap-
pen, by fitting wrong, to comprefs the fciatic nerve,
they are incapable for fome time after to fuppoit
themfelves on the afl'edted extremity : And this is Hill
more remarkable in the fciatic or hip-gout , in which
the member is not only weakened, but gradually
fhrivels and wafl.es.

THE

THE

DESCRIPTION

Of the Human

LACTEAL SAC and DUCT.

The receptaculum chyli of Pecquet , or facctts lac-
teus of Van Horne , is a membranous fomewhat
pyriform bag, two-thirds of an inch long, one-third
of an inch over in its larged part when collapfed ;
fituated on the firft vertebra of the loins to the right
of the aorta , a little higher than the right emulgent
artery, behind the right inferior mufcle of the dia-
phragm : It is formed by the union of three tubes,
one from under the aorta , the fecond from the inter-
ftice of the aorta and cava, the third from under the
emulgents of the right fide. The laEtcal fac, becom-
ing gradually fmaller towards its upper part, is con-
tra&ed into a {lender membranous pipe, of about a
line diameter, which is generally named the THO-
RACIC DUCT. This pafl'es betwixt the mufcular
appendices or inferior mufcles of the diaphragm, on
the right of, and fomewhat behind the aorta ; then,
being lodged in the cellular fubftance behind the
pleura , it mounts between the aorta and the vena a-
zygos, as far as the fifth vertebra of the thorax , where
it is hid by fhe azygos , as this vein rifes forwards to
join the defeending or luperior cava1, after which the
du£t pafiTes obliquely over to the left fide behind the

Of the LACTEAL SAC and DUCT. 311

aefophagus, aorta defcendenst and the great curvature
of the aorta , until it reaches the left carotid artery ;
behind which, on the left fide of the cefophagus, it
runs to the interftice of the firft and fecond vertebra
of the thorax , where it begins to feparate from the
carotid, ftretching farther towards the left internal
jugular vein by a circular turn, whofe convex part
is uppermoft. At the top of this arch it fplits into two
for a line and an half ; the fuperior branch receiving
into it a large lymphatic vefTel from the cervical glands.
This lymphatic vefTel appears, by blowing air and
injeding liquors into it, to have few valves. When
the two branches are again united, the dud continues
its courfe towards the internal jugular vein, behind
which it defeends, and, immediately at the left fide
of the iniertion of this vein, enters the fuperior pof-
terior part of the left fubclavian vein, whole internal
membrane duplicated, forms a femilunar valve that
is convex externally, and covers two-thirds of the o-
rifice of the dud ; immediately below this orifice a
cervical vein from the mufcul't fealeni , enters the fub-
clavian.

I he coats of the fac and duB are thin tranfparent
membranes-, from the infide of which, in the dud,
fmall femilunar valves are produced, molt commonly
in pairs; which are fo fituated as to allow thepafl'age
ol liquors upwards, but oppofe their return in an op-

pofite courfe. The number of thefe is generally ten
or twelve. 1

This is the moll fimple and common courfe, fixa-
tion, and flrudure of the receptaculum chyli and tho-
racic duB ; but having had occafion to obferve a va-
riety in thefe parts, of different fubjeds, I fhall fet
down the moft remarkable of them.

The fac is lometimes fituated lower down than in
the former defeription ; is not always of the fame di-
menfions; is not compofed of the fame number of
duds ; and frequently appears to confift of feveral
fmall cells or duds, inftead of being one fimple ca-

Thc

312 Of the LACTEAL SAC and DUCT.

The diameter of the du£f is various in mofl bodies,
and is feldom uniform in the fame fubjeft; but fre-
# quently fudden enlargements or facculi of it are ob-
lervable. — The divilions which authors mention of
this duiT are very uncertain. I have feen it divided
into two, whereof one branch climbed over the fore-
part of the aorta at the eighth vertebra of the thorax,
and at the fifth flipped behind that artery, to join
the otheF branch which continued in the ordinary
courfe. — The prectfe vertebra , where it begins to turn
to the left fide, is alfo uncertain. — frequently it does
not fplit at its fuperior arch ; in which cafe a large
fac is found near its aperture into the fubclavian
vein. — Generally it has but one orifice ; though I have
. feen two in one body, and three in another.: Nay,
fometimes it divides into two, under the curvature of
the great artery; one goes to the right, another to'
the left fubclavian vein; and I have found this dudb
difoharging itfelf entirely into the right fubclavian. —
The lymphatic veflel which enters its fuperior arcii,
is often fent from the thyroid gland.

Whether is not the fituation of the rcceptaculutn
rhyli lo much nearer the mufcular appendices of the
diaphragm in men than in brutes, defigned to fup-
ply the difadvantageous courfe the chyle muff other-
wife have in our erett pofture ?

Does not the defeent of the end of the diuft to the
fubclavian vein, and the opening of the lymphatic
into the top of the arch, contribute to the ready ad-
miflion of the chyle into that vein ?

FINIS.

A N

ESSAY

O N

Comparative Anatomy.

—Vos miinmc fugit, plures efle humani corporis partes, quarum
flruftura, et officium, etfi non aliunde quam ex beftiis defuirpta
Tint, nunc tamen in fcholis accipiuntur, atque probantur.

A nt. M. Valfalva in differt. Anatom, tertia.

Incidenda autem animalia, quibus partes ills quarum aOiones qux-
rimus, eadem atque homini funt, aut certe limiles iis ; ex quibus
fine metu erroris judicare de illis hominis liceat. Quin et rcliqua,
fi modo aliquam habcant ad homincm fimilitudincm, quantula-
cunque fit, idonca funt ad aliquid fuppeditandum.

Albini Prxf. ad Harvei Exercitationem <je molti cordis.

The THIRD EDITION,

EDINBURGH: "

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TO THE

reader.

TH E following Iheets were found
among the papers of a phyfician late-
ly deceafed, and fent by a friend of his to
the bookfeller, with liberty to print them.
As the fubje<5t appeared ufeful, they were
prefented to two eminent phyhcians in
town for their approbation : One of
them was fo good as to write the follow-
ing letter, which, with difficulty we ob-
tained leave to print, as it will ferve for
a preface to the whole. From what he
there fays, in relation to the fubjecd and
treatife, we prefame the publiffiing it
mull be a fervice done the public.

A 2

A

A LETTER, 6 c. .

S 1 R,

JHAVE read over the papers on Comparative Ana*
tomy, which I now return you with thanks by
this bearer. Yop dclire my thoughts on the i'ubjed
and treatife, and indeed the pleafure 1 had in the
perufal makes your demand but juft. — What is called
Comparative Anatomy was certainly the firft branch of
the feience that was cultivated, and from it the earlieft
anatomifts formed their notion and fyftem of the hu*
man body. The natural prejudices of mankind, and
in fame fenfe common humanity, oppofcd any at-
tempts to be made in the other way. As the firft
phvficians were pbilofophers, and this part of natu-
ral knowledge more immediately related to medicine,
they particularly applied to it. Democritus, who,
according to fome, was the inafter of Hippocrates,
ipent much time in difleding brutes, and examining
their feveral parts. He applied himfelf with fuch ’
eagemef* to this ftudy, as to incur the cenfure of
madnefs. His deftgn was to examine the nature of
the biJe, and Uarn ibefeat and caufes of dfeafes. That
this foence was much improved by the times of Hip-
pocrates, is very apparent from his writings, which
are intermixed with reafonings drawn from it, and
tome parts of his phyfiology are only applicable
to brutes. Thefe paflages appear to us exceeding
obfcure, often falfe and contradictory, and have for
that r afon been rejeded by tome very great critics. —
But is not this owing to our own ignorance? We do
not well underhand the then received fyftem of ana-
tdmy, and his terms and names do not correfpand to
ours. '1 he fmall trad de V ulneribus Capitis is, I

think.

r 5 i

tHink, as great a matter-piece in its kind as the
Coac* Prxdiftiones. Yet the firft has been efteemed
by fome lame and imperfect ; and afforded cccafion
for many difputes and wranglings, and all tnis be-
caufe not underflood : Anatomitts however have done
by Hippocrates in raoft cafes as the critics with Ho-
mer, made him the matter of all human and divine
fcience. Not a new divifion of a bone, or difpute
about a procefs of articulation, but has been referred
to his judgment, and he has often been made to ex-
plain what lie never dreamed of. Galen, the father
of anatomitts, is for the fame reafon in many places
become an obfeure writer. He is accufed and de-
fended by the greatett fucceeding matters. V efalius,
the great reftorer of anatomy, will not allow accu-
racy or truth in many of his deferiptions ; they are
according to him taken from brutes, and obtruded
on the work! for human.

I he other anatomitts treat \ efalius much in the
fame manner, and with uncommon fagacity and un-
wearied application have found out variations and
lufus nature in particular parts, that they may etta-
bjjfh Galen’s delcriptions, and condemn thofe of Ve«
falius. This is particularly the cale with Luttach us
in his treatife on the kidneys, flow fhall we now
underttand Galen, and judge between thefe great
anatomids. It is Comparative Anatomy alone can ex-
tricate us from this contulion, as it will teach us, when
Galen and others deferibed and realbned fro i brutes,
and when not. We ihall then find (I believe) that
the greatett part of his delcriptions w'as taken from
brutes, which he transferred by analogy to the ha-
man body, and fo are inaccurate ; that a few were
taken from the human fubjett, and are not capable of
being otherwife applied. 1 his ttudy he himtclf re-
commends with great earntftnefs to his fcholars, and
it is obfervable that the moft eminent anatomitts hrtt
diftovered their genius, by an early attachment to

C 6 3

it. Tliis was particularly the cafe of Vefalius and
Val'al'va *.

As the firft knowledge the ancients gained in ana-
tomy was from the direction of brutes, fo they form-
ed the names and terms of art from the molt natural
appearance the part afforded, and that in different
animals. 1 hole names were applied to the corre •
fponding parts in the human hotly, and retained by
fucceeding anatomifts to avoid a multiplicity of words.
This however produ.es one bad effect, that it muft
miffead us in our conceptions, as thofe names are
often very improper epithets in the human fubjeft.
The author has elegantly remarked feveral of thefe.
The name of right and left ventricle is apt to give a
wrong i lea of the petition of the heart, and the aorta
afee miens and defcenJcns has impofed on fome of the
inafters in anatomy, who, it is plain, have taken tiieir
figures from the name. Difputes have arifen about
the appendix vermiji.rrnis, &c. which are all cleared up
when we once view the part in the animal whence
the name was taken. A fhort technical dictionary,
with an account of the fubjecls whence the names of
the feveral parts were derived would be of great ole
to itudents, and is one of the chfukruta in anatomy f.

The intention of nature in the formation of the
different parts, can no where he fo well learned as
from this fcience ; that is, if we would underhand
' phyfiology and reafou on the functions in the animal
orconomy, we muft fee how the lame end is brought
• about iu other f; ecies — We mult contemplate the
part or organ in different animals, its iliape, poll •

* Gaudcbat enim avicularum, alioruirique animalculorum diflec-
tionitus, corumque exta cuiiotius, quam pro iila aitate, rimabatur :
qu;.m ego ptsefignificationc®, non in Vcfalio tantum, fed in aliis
quoque pucris fuitTe itio, qui, cum adoltvii'.c it, analomiai penitus
le dedidcrunt. Morj.:gm Comment, de v:tu Valjalvs.

f Such a treatiu: might in a great mcjfure- be collected from
Sylvius’s works, and Fatius’iOficonomia Hippocratis.^ Camerariu*
did fuch a work under the title of Ai-eoum orouacix.r., tut it is a
ure book.

Mon*

[ 7 1

tion, connexion with the other parts, 6c. and ob-
serve what thence ariles — if we find one common ef-
fect conftantly produced, though in a very different
way, then we may fafely conclude that this is the
ufe or function of the part ; this reafoning can never
betray us, if w e are but fure of the fads. 1 he
writers in phvliology have generally taken another
rout, and one favourite thefts or other ferves to ex-
plain the whole or nioff of the fyftent. Aq innate
and concocting heat, acids, menfruums , &c. have all
had their fucceffive reigns and patrons And, in
in truth, phyficians feem not to have fuffkiently con-
fidei ed the importance cf this lludy to form a com-
plete phyfiology, which mutt ever be the great bafis of
their art. T hey have bellowed pains iu examining
the human body, differed minutely its leveral parts,
traced out (perhaps often invented) a new divifion of
a mufcle ; — but how little has pbyfjc been promoted
by all this? i he molt accurate delcription of the hu-
man ltomach, with all its veins, arteries, nerves, tdfe.
will never rightly explain digeftion. — What mutt we
then do? — examine it in the other fpecies of animals,
mark there its differeiiLes and the etfeds. compare
thefe with the human, and then lhall we in loine
rnenfure.be able to judge what are the principal in-
Uru.uents, and how they are employed iu this corn-
pound action. Any other way. of reafoning (as the
author, well ohferves), will never bring us to the fo*
lotion of a philol'ophical or medic. d problem. It muft
indeed be confefled, that this method is tedious and
flow ; many obfervauons muft firlt be made, and the
labour cf learebing and examining gone through,
before we can bat e proper materials to build on.
^ et thefe are the hard conditions on which the know-
ledge of natural caufes is to be obtained, which, as a
great genius lays, “ Tam facile foleriia. vinci pof-
“ lunt, quant folent couatibus vulgaribus didiculter
“ cedere.”

Of this kind of reafoning, we have many beautiful
inftauces tn the following papers; fucli is the account

of

C 8 J

of the pofition of the duodenum, the Riftory of the-
thymus and thyroeia gland, their ufe and mutual pro-
portion, rhe ufe of the fplten , See. 1 his laft he ex-
plains in fo Ihort and mafterly a manner, as you’ll
6nd more argument in the few lines upon it, that is
to be collected from whole treatifes on the fnbjech
But as his defign was to give a defeription of the fe«
veral fpecies, or rather their principal differences, he
chiefly confines himfelf to this : fo in the anatomy
of the dog he compares the different pofition, fh.ipe,
length, JsV. of the fcvcral parts with the correfpon-
ding parts in man, and from that one circumftance,
the difference of an erect and horizontal pofture, ex-
plains all the variations. 1 his reafoning then gives
folution to many difficulties in the human anatomy ;
why the fplten !o firmly attached ro the dhrphragm ,
why the omentum reaches only fo far, why the pos-
terior part of the bladder only covered by the peri -

tonaitm, See. 1 here have been difputes about

the fiffu re itt the human liver, and different accounts
given. Thefe all vauifh, when we confider this
t-j feus in different animals. We then find that there
are more or fewer divifions, according to the greater
or lefl'er flexility of the /pine. 1 he lame rule holds
with regard to the divifions of the lungs. This rea-
foning likewife excludes the pretended u(e of the
ligament in the human liver. And in Ihort we can
onderftand but little of our own ftrufiure, unlels we
ftudy that of other animals ; we lhall then find that
thfe feveral variations are relative and depend on the
different way of life ; that is, one hading fpeciality
draws after it a great many more, in which nature
is always an oecononnit and takes the lhortelt n ut.

The beautiful gradation of nature in the different
orders of beings, is very remarkable, and ltrikes the
mind firft, as being moft obvious ; but when we take
any one fpecies, the -cafe there is (fill the fame, and
we oblei ve as furpriling a difference. ! hus in the
animal kingdom, fome are provided with lungs, when
others are deprived of thefe breathing organs j foaie

have

[ 9 3

have a mnfcular diaphragm and ftrong abdominal muf-
c/es, others a mere membrane ; fome have lecleals, o*
tliers want them. It mult be very/entertaining to
learn how thefe differences anti deficiencies are ad-
jufted and fupplied ; his then from this fcience alone
we can underlland that ftmpliehy of nature, which is
much talked of, and hut 1st tie underlloo'd. Hence
Hkewife we muft learn what to think of animals per -
feel and imperfett.

Anatomifts have made a noife about the different
ftructures of the fame part in the human body, and
been at great pains to make collections of thofe lufus
nature as they call them ; which, becaufe they are
rare, are for that very reafon of no great eonfequence
to be known. The epithet however is extremely pro*
per ; for the mod remarkable of them are tranfitions
from the order or law of nature that obtains in one
fpecies, to that of another. Thus it has been ob-
ferved (though very rarely) that the liver was fitu-
ated in the left hypcchondrium ; but as our author
remarks, it is not peculiar to it to lye on the right-
fide in animals ; for in fowls it lies equally on both,
and in filhes moftly on the left.

It is furpriling that we have no tolerable treatife
on this fubjeCt, which is in itfelf fo entertaining and
fo conducive to promote medicine. Thofe, who
have made attempts this way, have only collected
and ranged in order fome particular fpecies, fuch as
birds or filhes. 1 hey have likewil’e with great la.
bolir given us figures and deferiptions of them, — but
al! this is little elie than mere araufement. ’Tis the
llruCture of the internal organs we leek after, and
the manner how the differenc functions of the animal
oeconomy are performed. I heir hiflories of thefe
are every way defective and erroneous. i here are
indeed noble hints to be found in the writings of
lome of our modern anatomills, particularly thofe of*
the immortal Dr Harvey, i hat great man well un-
clcritood the importance of this lcience to advance
medicine, and accordingly employed the molt of his-

time

[ 10 ]

time in diffecling animals of different tribes, and
making experiments on them : by which means he
made the greatell difcovery that ever was in the
fcience, and laid the foundation of the prefent fyflem.
He had certainly left ns other treatifes on the fubject,
had he not been interrupted by the civil wars. The
phyficians who lived then, imitating his example,
made many new experiments on the bodies of brutes,
changing their juices by transfufing of new liquors,
accurately marking the effe&s, SsV. that all this
might be transferred to the human hotly ; and indeed,
from the application of thefe reafonings, to the ob-
servations they made on morbid bodies, the fcience
feemed fall advancing to that phyfical certainty,
which can be attained from experiment and obferva-
tion. But alas ! this fpirit died with thefe great
men, and theory and calculation came in its place.
Mathematics , it was fuid, could alone bring the
fcience to certainty, and throw out conje&urc. The
quantity and velocity of the blood, the force of the
heart, diameters of the velTels, 5sjV. were fubjedted
to meafure and number, and difeafes next were to
be accounted for all in a mathematical manner.- —
This method however did not fucceed according to
wilh ; for firft thefe great geniufes difagreed widely
in their calculations, and differed from one another ;
..whence in place of certain conclufions we had only
wranglings and difputes : not to mention, that fome
of them-made fueh edimates, as mud plainly apppear
ridiculous at firli fight (#). 1 his, you’ll lay, pri vcs.

(*) The ingenious Dr Pitcairn was the chief man in t! efe parts,
who gave into this way. He fuppofes the force of mufylcs to be in
a compound ratio of their length, bieadlh and depth ; that is, as
they are honogeneoui fohds in the ratio of their weights. Whence
knowing the force ol any one mufcle, we can by the rule of pro-
portion (from their weights) determine that of another. This he
applies to the ftomach, and by the computation its mufcular force

is equal at lead to 117088 lb. weight. That mufcles are in that

proportion, is a mere hypothefit, for which the doctor docs not offer
the l'mallefl proof ; and had he afTigned five ounces ^s the weight
of the ftomach, he had been nearer the truth. This is one glaring
inflance, how much theory and whim may prevail with the great elf
of men over common Jtnjt.

nothing

[ II ]

nothing, it was the fault of the artifts, who aflumed
wrong hypothefes for their calculations, or were not
perhaps accurate in their obfervations. True, —

but whofe fault was it to adapt figure and number
to a fubjeft which refufes them, through its num-
berlefs deviations from fixed laws and condi-
tions?— Is an animate body a mere bundle of hard
conical elaftir tubes, and the heart a pump forcing
the liquors through ? Are then all the veflels exatt
cones, or have any two anatomjfs agreed in their
meafures of them ? Do they not yield every way ?
And are they not continually obftru&ed in different
places? Are they not many different attractions pre*
vailing for the feveral fecretions, and many different
forces acting on the velfels at the fame time which
can never be determined? SsV. Thefe and fuch like ccm-
fiderations will loon convince us how little the prac-
tice of medicine is to be promoted by thofe fpecula-
tions (*). If thele gentlemen meant by mathematical
reafoning phylical experiments, then no one ever
doubted of this, no more than they do of the ufe of
mathematics in natural phttofophy itfelf. l ut as
this feems not to be their fenfe of the matter, they
fhould point out a few dileafeb which this fcience has
explained, and wherein it has corrected the received
practice — But I am quite got from the fubjedl to
what is foreign. l’o return then, Comparative Ana-
tomy has hitherto been treated but by pieces. Thus
fome writing on the human eye, have examined the
eyes of other animals ; and fo with regard to the
heart, <&c. Some have given us the defcription of

(’) The authority of Hippocrates is often adduced in this argu-
ment, foi which they cite two paflages. In the one he recommends
the ftudy of ofironmy , as neceffary to a phyfician, and in the other,

that of arithmetic and geometry. The firft he did from his belief

in the iufluence of the Jiars, and the fecond from his veneration for
the Pythagoric numbers ; in the myfterics of which he founded his
theory of the crifes in acute dileafes : Both thefe conliderations then
are foreign to the purpofe, nor is there in any of his genuine
writings the fmalleft veftige of this kind of reafoning. On the con
tn^7 Gtlfus fays of him, Primus ab fiuiioja picntiac medtanam fepa-

one

£ 12 ]

One particular animal, others of another. But no
one author, as I know of, has given us a fvftem of
this fcience where we might have a fummary view
of the moft material differences in the ftrudture of
animals. There are indeed compends of this fcience
if you will, which are efteemed by many, and were
Wrote with the noble delign of illuftrating the wif-
dom and goodnefs of our maker. But thofe who
compofed them were not anatovnifts themfelves, fo
could only colled from others, which they often do
Without any judgment — for how voluminous loever
their works mav be, yet if you’il flrip them of their
repeated exclamations, citations of author^ and books,
the many ftrange and furpriling flories, all ttld
however by creditable vouchers, you’ll have little
left behind befides an indigelled chaos of hiflories
and defcriptions, fome true and many falfe. The
argument how-ever was popular, and they could not
fail of pleafmg.

The author of thefe few lheets is certainly a great
tnafter of the fubject, and has here laid down an ul'e-
ful plan, which will not be difficult for others to com-
pleat. The defcriptions, ’iis eafy to fee, are all
taken from the life, and his reafoning plain and con-
clulive. Thefe are intermixed with many practical
obfervations in medicine and furgery, which mult e-
qually inftrud and entertain the reader. — You have
now a few loole reflections on this fubjeCt, wherein I
have entirely confined rayfelf to that light, in which
ir is here treated. I fhall only remark one thing
more, that the author’s modefiy is at leafl equal to
his capacity and knowledge ; a rare quality to be met
with in an anatomifl ! Head him on the fubjcCt of
the Human Alaniois, and obferve his conclulion of
the argument You mult then fay, it had been
happy for the public, if half fo much candour and
felf diffidence had prevailed in the difputes among
the learned. The world had been more inftru&ed,
and they more juflly efteemed.

I am, Sir,

Your moft humble Servant.

A N

ESSAY

O N

Comparative Anatomy.

The INTRODUCTION.

TU^ principal advantages of Comparative Ana-
tomy are the follow ng : Firft, it furnifhes
us with a fufficient knowledge of the different
parts of animals, to prevent our being impofed upon
by fuch authors who have delineated and defcribed
leveral parts from brotes as belonging to the human
body. Secondly, It helps us to underhand feveral
pail ages in the ancient writers in medicine, who have
taken many of their defections from brutes, and
jeafoned from them; their reafonings have often

rrifaP1Plled confe,Iuent!y wrong explained)
y the moderns, through a foolilh fondnefs to fup-

poi t then own inventions, or give an air of antiquity

to a favourite hypothefis. The third and great ufe

reap from this faence is the light it cafts^n feve-

B ral

1

The INJTRObuCTION.

ral functions in the human economy, about which
there have been fo many difputes among anaromiils :
'l hefe will be in a great meafure cleared up by exhi-
biting the ftrufture of the fame parts in different ani-
mals, and comparing the ieveral organs employed in
performing the fame aftioig which in the human body
is brought about by one more complex.

In this view it is altogether needlefs to infill on
thofe parts whole ufe is eafily underftOod when once
their firufture is unravelled ; thus, for inflauce, if
Ave be acquainted ' with the aflien of the mufcles in
general, it will not be difficult to determine the ufe
of any particular mufcle, whofe origin and infertion
is kndvvn, if we at the fame time conlider the va-
rious connexions of the bones to which it is fixed,
and the different degree of mobility they have with
refpeX to each » ther : In the fame manner, if we
know the ufe of the nerves in general, we can eafily
affign the ufe of thofe nerves which are dillributed
to any particular part. 1 here is then no occafion
for a complete ojl eulogy, my: logy, Izfc. of the fevcral
animals we lliall treat of, nor need we trouble our-
felves about the ItruXure of any of the parts, unlefs
whenitferves to illuftrate fome of the fore-mentioned
purpofes.

That the firft ufe we propoftd from examining the
ftruXnre o,f the parts in brutes is real and of confe-
quence, is evident from looking into the works of
Ibine of the earUett and gre licit mailers of anatomy,
who for want ol human fuhjeXs, have often borrow-
ed their deferiptions from other animals. The great
Vefalius, although he judly reproves Galen for this
fault, is guilty of the fame himfclf, as is plain from
his delineations of the kidneys, uterus, the m nicies of
the eye, and fome other parts, isor is anticpiity
only' to be charged with this, ftnee in Willis’s Ana-
emia Cerebri (the plates of which were reviled by
that accurate anatomill t)r Lower), tncre art Icvecal
of the pictures taken from different brutes, elpecially
tile do<r, b elides thofe he owns to be Inch.

Wc

3

The INTRODUCTION.

We /hall give feveral examples of the fecond me

in the lequel of the work.

The animal kingdom, as well as the vegetao.e,
contains the mod 1'urprifing variety, and the deicenc
in each is fo gradual, that the little tranfltions and
deviations are almod imperceptible. 1 he bat and
flying fquirrel, though quadrupeds, have wings to
buoy therofelves up in the sir. tonic birds inhabit th-
waters, and there are fiihes that have wings, and are
not drar.gers to the airy iegions ; the amphibious
animals blend the terrejirial and aquatic together.

The animal and vegetable kingdoms are likewife
fo nearly connected, that if you take the highed ct
the one, and the lo.ved of the other, there will
fcarce be preferred any difference : For indance,
what difference is there betwixt an oyder, one of the
of the mod inorganifed of the animal tribe, and the
fenfitive plant, the molt exalted of the vegetable
kingdom? they both remain fixed to one ipot, where
they receive their nourifhmenr having no proper
motion of their own, fave the lhrirlking from the ap-
proach of external injuries. 1 hus we obferve a
furprifing chain in nature.

As there is then fuch a vafl variety, it is not only
needlefs but impoffible to confider all of them parti-
cularly. We 11 all take only fome of the mod re-
markable genera, and hope from what will be faid of
them any of the intermediate degrees may be under-
dood.

In treating of quadrupeds, we fhall divide them into
the carnivorous, i. e. thole that feed indifferently on
animal and vegetable fubdances, and granivcrcus ;
As an indance of thefe laft we lhall take the rumi-
nant kind. The fowls we lhall alio divide into thofe
that feed on grain and thofe that feed on fielb.
1 he didindion we lhall make in treating of hikes,
lhall be of thofe that have lungs, and thofe that
have them not. The fird indeed are with difficulty
procured, and at the fame time differ very little front
quadrupeds .

B 2

As

4

The INTRODUCTION.

As the ftnifture of infers is To Very minute, and
tends us but little alliitance for the ends rropofed
we purpofely omit them, *

3n ftiqairing into the flrutfurr of different animal*,
we ought to be prcvio ifly acquainted with the form of
their body, manner of life, kind of food ; or, in
ihort, with their natu al hiftqry, which wi 1 lead us
to account for the reafon of their difTeteut {hue-
ture, and thence explain the anions of the human

COMPARATIVE ANATOMY*

5

Of Quadrupeds in General.

ALL quadrupeds have a covering of hair, woo!,
&c. to defend them from the injuries of the
weather, which varies in thicknefs according to the
feafon of the year, and difference of the climate :
Thus in Rufba and the northern countries, the furi
are very thick and warm, while the little Spaniih
lap-dogs, and Barbary cows, have little or no hair at
all.

The cutis and cutlcula in quadrupeds are difpofed
much in the fame way as the human, only more
elaftic ; immediate ly under this there is a very thin
cutaneous mufcular fubftance called panniculus carno-
fus, which is common tq all quadrupeds, the porcine
kind excepted; this principally covers the trunk,
ferving to fhrivel the fit i n , in order to drive off infects,
their tails and heads not being fuffeient for this pur-
pole, while their extremities are employed in thtir>-
fupport and progreHion.

It has probably been from obferving fome mufcles
of the human body, litth as the platyfrna m sides, err-
mafler, and front ides, and the collapfed tunica cel -
lu'.ofa of emaciated fubjects, to refetnble this thia
mulcle, that fome of the older anatomiils reckoned fuch
a panniculus among the common teguments of the hu-
man body. I Ills Ct.rJus Stephanas has well o-'o*
ferved.

Moll part of quadrupeds want clavicles , whereby
their anterior extremities fall upon their chelt, fo as
to make their tkr,:x proportionally narrower than
the human. I his ftnall distance of their anterior ex-
tremities is very necellary ter their uniform progref-
tion : Apes indeed and fquirrels have ilavicles to al-
low them a more loll uie of their extremities in climb-

13 3 in g,

6

COMPARATIVE anatomy.

ing, but when they fit down on all- four they walk
but indifferently.

I l « Y 1 * » » ' 3 4 4 1 \ j % *

The Anatomy cf a Dog.

\~K~/ E may fir ft obferve of this animal, as indeed
V V of liioft e/uadn peds, that its legs are much
fhorter in proportion to ts trunk than in man, the
length of whole Heps depends entirely on the length
of his inferior extremities ; howev er, to balance thi?,
the trunk -of the animal is proportionably longer and
fnraller, his (pine more flexible, by which he is able
at each flep to bring bis poftcrior extremities nearer
to his anterior, his common teguments are much a-
kin to thole of other quadrupeds , only they allow
\litt!e or no patlage for fwea-t, but when lie is over-
heated, the fuprrlluoua matter finds an exit by the
falivary glands, for he lolls out his tongue and Ha-
vers plentifully.

The pyramid'd mufcles are wanting, to funpfy
which the refias is inferted flelhy into the os pulis.

The omeuiian reaches down to the os pubis, which
coufulering the poflure of the animal we will find to
be a wife provdion, fince its ule is to (eparate an
oily liquor for lubricating the guts and facilitating
their periftaltic motion; lb in our ere^ pollute the
natural gravity cf the oil will determine it downward,
but in the horizontal pefition of thefe creatures, if
alt the bit'ffincs were not covered, there would be
no favourable derivation of the fluid to the guts ly-
ing in the poiterior part of the abdomen, which is
the higheft ; and belides, had the omentum reached
much farther down in us, we had been in continual
hazard of an epipfocele, which the dog is not fubjodl
to, as his vijt era don't prefs fo much on the rings of
‘the abdominal 'mltfclesj The inferior and anterior
lamella of the omentum is fist to the fplten, jx.ndus-oi
tik; ftomach, p-hrus, liver, iffc. in the fame way as
the human, but the funerior ha' ing no colon to pafs

7

COMPARATIVE ANATOMY.

over, goes direftly to the back- bone. This ferves
to explain the formation of the imall omentum in the
human body, which is nothing but the large omentum t
having lolt its fat, palling over the Itomach and colon ,
where it realTurnes its pmguedo, fo proceeds and is
firmly attached to the liver, fpine, 6>V. i he llrias
of fat are pretry regularly dilpoled through it, ac-
companying the diltriburion or the blood-vellels
to guard them from the preflure of the fuper- incum-
bent vfeera.

This animal’s Itomach, though pretty much refem-
bling the human in its ihape, is fomewhat d fierently
fi uated. It lies more longitudinal, as indeed all the
other vifeera do, to accommodate themlelves to the
lhape of tire cavity in which they are contained, that
is, its inferior orifice is much farther down with re-
fpect to the i'uperior than the human : By this means
the grofs food has an eulier pafiage into the duode-
num. Again, the fundus of the human Itomach, w hen
diltended, Hands almolt directly forw ards, w hich is
©ccafioned by the little omentum tying it fo clofe
down to the back bone, isfe. at it’s two orifices j
bin it not being fixed in that manner in the dog, the
fundus remains always pofterior ; 1 his alio aniwers
very well the lhape of the dilferem cavities, the
cliltance betwixt the candle, and fundus bei g greater
than that betwixt the two hues. It leems to he
much larger in proportion to the bulk of the animal
than the human, that it might contain a greater
quantity of food at once, which was very necefii.ry,
lince this animal cannot at any time get its luiten-
ance as men do. 1 he turiil/hn is not fo large, nor
is there any coarction forming the antrum vtlllt/ii as in
the Itomach of man. It is confiderably thicker and
more mufcular than ours for breaking the cohelion of
their food, which they fwallovv without iurfkient
chewing. Hence it is evident the force of the
Itomach is rot fo great as lome would have it, nor
its contraction fo violent j otherwife that of dogs
would be undoubtedly wounded by the Iharp bcn.es

3

COMPARATIVE ANATOMY.

&c. they always take down ; for the contraftion here
is (till greater than in the human ftomaich, which is
much thinner. 1 he ruga of the tunica villofa are
neither lb large nor fitti itccl tranfverfefy as in the
human, hut go from one oritice to the other ; the
reafon of which difference is, perhaps, that they
might he in lets danger of being hurt by the hard
fubftances this creature frequently feeds upon,, and
for the fame reafon there is not the like coardlion at
their pybrus.

1 he intejiines of this animal are proportionally
much fhorter than ours, for the food which theft
creatures moltly life, foon diflblves and then putrifies ;
on whicit account there was no occafion for a long
tract of inte/Iines, but on the contrary that it fhould
he quickly thrown out of the body : the fame is to
be obferved of all the carnivorous animals. The
mufcular coat of the intejiines isalfo Wronger than the
human, to protrude the hard bones, left they fhould
{top fomewhere in the canal.

The valvuLt connsventes are lefs numerous, and in >
a longitudinal direction.

The duodenum differs confiderably in ils fituation
from the hnman ; for in man it firft mounts from the
pylorus upwards, backwards, and to the right fide,
then p tides down by the gall-bladder, and marching
over the right kidney and luperior part of the pfoas
mufclct, makes a curvature upwards, and pafTes over
the back bone and vena cava inferior , to the left
h'ypochondrium , where it gets through the omentum ,
mtfentery and mefsalon to commence the jejunum, being
firmly tied down nil the way, the biliary and patureatic
duffs entering at its mi ft depending part : whereas
in the dog the duodenum is fixed at the pyiorus to the
concave furface of the liver, and hangs loofe and
pendulous with tlte mefentcry backwards into the ca-
vity of the abdomen, then turning up again is fixed
to the back-lone uhere it ends in the jejunum ; the
bile and pancreatic juice are poured into it at the
moft depending part ; therefore the fame intention

teems

COMPARATIVE ANATOMY. £

Teems to have been had in view in the formation of
this part in both, viz. the giving the chyle, afcer the
liquors of the liver and pancreas are poured into ir,
a difadvantngeouscourfe, that fo it might be the more
intimately blended with the humours before its entry
into the jejunum, where the lacteals are very nume-
rous : And thus by reafon of their different pofture,
the fame defign ^'though by a very different order of
the parts) is brought about in both

The other fmall guts are much the fame
with ours, only fhorter. 1 he great guts are alfo
Ihorter and lefs capacious than in the human body ;
and we take it for a general rule, that all animals
that live on vegetable food, have not only their
fmall guts confiderably longer, but alfo their great guts
more capacious than fuch creatures as feed on other
animals. Hence man from this form of his intejlines and
that of the teeth, feems to have been originally de-
figned for feeding on vegetables, and ftill the mod
of his food and all his drink is of that clafs.

The reafon of this difference feems to be, that as
animal food is not only much more eafily reduced into
chyle, but alfo more prone to putrefaftion, too long
a remora of the juices might occafion the word con-
fcquerices. So it was neceffary that their recepta-
cles Ihould not be too capacious, but on the contra-
ry, being fhort and narrow, might conduce to the
feafonable difeharge of their contents. Whereas
vegetable food being more difficultly diffolved and
converted into an animal nature, there was a riecef-
ftty for fuch creatures as fed on it to be provided
with a long internal canal, that this food in its paf-
fage might be conliderably retarded, and have time to
change its indoles into one more agreeable to our na-
ture. Eefides which, there is another advantage
which accrues to man in particular, from having his
great guts very capacious ; for as he is a rational be.
ing, and mollly employed in the fun&ions of fecial
hie, it would have been very inconvenient as well
unbecoming for him to be loo frequently employed

ia

IO COMPARATIVE ANATOMY.

in fuch ignoble exercifes, fo that having this large
refervoir for his faces alvinx, he can retain them for
a confiderable time without any trouble.

I he appendix vermiformis juftly enough deferves
the name ot an ii.tejlinum cecum in this fubjeiff,
though in the human body it does not, and it has
probably been from the largenefs of this part in
other animals, that the oldell anatomifts came to
reckon that fmall appendkle in man as one of the
great guts : On its internal furface we obferve a
great number of mucous glands.

1 he colon has no longitudinal ligaments, and con-
sequently this gut is not purled up into different bags
or cells as the human, nor does this intejlir.e make any
circular turn round the abdomen , but paffes dire&ly
acrofs it to the top of the os facrum, where it gets
the name of redlum .

At the extremity of the mtejlinum rectum or verge
of the anus , there are found two bags or paunches,
which contain a moft abominable fetid mucus, for
which I know no life, nnlel's it ferves to lubricate
the ilrained extremity of the refium, and defend it
againft the afperity of th e-faeces, or to feparate fome
liquor that might otherwil'e prove hurtful to their
bodies. 'I here is nothing analogous to thole facs
in the human fubject, unlels we reckon the mucila-
ginous glands that are found moll frequent and large!!
about the lower part of the tedium.

The mefentcry is confiderably longer than in the
human body, for in man had the mejentery been very*
long, the guts would have fallen down on the lio-
mach, 6r. by reafon of his ereft polirion. 1 he
fat is here difpofed in the fame way, and for the
fame reafon, as in the omentum. The inte/flices betwixt
the fat are filled with a fine membrane. Jnftead
of a great number of glandules vagx to be found in
the human mefentery , there is only one large gland
to be oblerved in the middle of the mefentcry of a
dog, which from its imagined refeinblance to the
pancreas and the naaie cf its difcoverers, is called

pancreas

II

COMPARATIVE ANATOMY.

pancreas Afdlli. The reafon why this in man is as it
were fubdivided into many fmaller ones, may poflibly
be, that as the guts of a human body are propor-
tionally much longer than thole of this creature, it
would have been inconvenient to have gathered all
the laReaprhm generis into one place, whereas by
collecting a fe.w of thefe veffels into a neighbour-
ing gland, the fame effect is procured much more
eatilv.

The pancreas in man lies crofs the abdomen, tied
down by the peritoneum ; but the capacity of this
creature’s abdomen not allowing ot that fituation,
k is difpofed more longitudinally, being tied to the
duodenum which it accompanies for fome way. Its
duel enters the duodenum about half an inch below
the others.

The fpleen of this animal differs from ours very
much, both in figure and fituation. It is much
more oblong and thin, and lies more according to
the length of abdomen, like the pancreas. Though
die fpleen of this creature is not firmly tied to the
diaphragm (’which was neceffary in rur erect poflure
to hinder ij, from f tiling downwards) yet by the ani-
mal’s prone politico, its poftcrior parts being rather
•higher than the anterior, i: comes to be always con-
tiguous to this inufcle, and is as effectually fubjedted
to an alternate preflUre from its action as the human
fpleen is.

1 he human liver has no fijfm'es or divifions, un-
lefs you pleafie to reckon that linall one betwixt the
two pvbe, where the large veffels !fenter : Whereas
in a dog and all other creatures that have a^large
flexion in their (pine, as lions, leopards, cats, &C.
the liver and lungs are divided into a great many
lobds by deep fections, reaching the large blood-
vefftls, which in great motions of the back bone may
eafiiy fhuffle over one another, and fo are in much
lefs danger of being torn or bruiled, than if they
were formed of one entire piece, as we really fee it
in hurt.es, cows, and filch creatures as have , their

back-bone

ra COMPARATIVE ANATOMY.

back-bone ftiff and immoveable. There is here no
ligamentum latum conne&ing the liver to the dia-
phragm, which in ourfituation w as neceflary to keep
the vifcus in its place ; whereas in this creature it
naturally gravitates forwards, and by the horizontal
pofition of the animal is in no danger of preffing
againft the vena cava : The preventing of which is
one ufe generally afligned to this ligament in man.
Had the liver of the clog been thus connected to the
diaphragm, the refpiration mull neceffarily have fuf-
fered ; for as we ihall fee afterwards, this mufcle is
here moveable at the center, as well as at the fides:
But in man the li er is fixed to the diaphragm, mod.
ly at its tendinous part; that is, where thepericar-
dium is fixed to it on the other fide ; fo that it is in
no danger of impeding the refpiration, being fuf-
pended by the mediajlinum and bones of the thorax.
In confequence of this vifcus being divided into fo
many lobes, it follows that the hepatic duffs cannot
pofiibly join into one common trunk till they are
quite out of the fubdance of the liver.

We come next, after having examined the chylo-
poietic vifeera, to dilcourfe of thofe organs that ferve
for the fecretion and excretion of urine, and firft of
the kidneys, which in this animal are fituated much
in the fa ne way as in the human fubjeef, but have
no fat on their inferior furface, where they face the
abdomen, and are of a more globular form than the
human. The reafon of thel’e differences will eafily
appear, if you compare their fituation and pofture
in this animal with thofe of a man who w’alks eredf.
They are placed in this fubjeft in the inferior part
of the body, fo are not fubjeft to the preffure of the
vifeera, which feems to be the principal caufe of the
fatnefs of thole organs in us, and perhaps may like-
wile be the caufe of our being more fubjeft to the
done than other animals. Hence Acre is no need
of any cellular fubftarce to ward ofF this preffure
where there would necelfarily be fat collected ; but
the fuperior part of their kidneys is pretty well co-

vered

COMPARATIVE ANATOMY. 13

rered with far, left they fhould fuffer any compreffion
from the adion of the ribs and fpine.

In the internal ftrtidure there is ftill a more conli-
derable difference, for the papilla do not here fend
out fingle the feveral tubuli uriniferi , but being all
united they hang down in form of a loofe pendulous
flap in the middle of the pelvis , andjform a kind of fep -
turn medium, fo that a dog has a pelvis formed with/-
in the fubftance of the kidney. The only thing
that is properly analogous to a pelvis here, is that fac
or dilatation of the ureters formed at the union of
the duftula urihifira. The reafon of thefe particu-
larities may probably be, that' the liquors of this
animal, as of all thole of the carnivorous kind, be-
ing much more acrid than thofe that live on vegeta-
ble food, its urine muft incline much to an^alcalef-
cency, as indeed the line 11 and tafte of that liquor in
dogs, cars, leopards, Izfc. evidently fhew, being fe-
tid and pungent, and therefore not convenient to be
long retained in the body. Kor this end it was pro-
per, that the fecerning organs ihould have as little
impediment as.poffible by preffure, isfe. in the per-
forming their functions ; and for that dtlign, the
mechanifm of their kidneys feems to be excellently:
adapted : We have moil elegant pictures in Emca-
chius of the kidneys of brutes delineated, as fueh,
with a view to lhew Vefalius’s error in painting and
defcribing them for the human.

1 he glamlula or capful it atrabilari £ are thicker and
rounder than the human, for the fame real'on as the
kidneys.

1 he ureters are more mufcular than the human,
becaufe of the favourable paffage the urine has
through them ; they enter the bladder near its
fundus.

1 he bladder of urine differs confiderably from
the human, and firft in its form, which is pretty
much pyramidal or pyriform ; this lhape of the dog’s
bladder is likewife common to all quadrupeds , except
the ape and thofe of an ered polture. In men it

14 COMPARATIVE ANATOMY.

is by no means pyriform, but has a large fac at its
pofterior and' inferior part : This form depends en-
tirely on the urine gravitating in our ereft pofture
to its bottom, which it will endeavour to protrude,
but as it cannot yield before, being contiguous to the
os pulis , it will naturally ftretch out where there is
the leaft refinance, that is, at the pofterior and la-
teral parts ; and were it not for this fac, we could not
come at the bladder to extract the ftone either by the
lcfTer or lateral operation of lithotomy. Moll ana-
tomies have delineated this wrong fo much, that I
know of none who have juftly painted it. excepting
Mr Cowper in his myotomia, and Mr Rully. It has
certainly been from obferving it in brutes and young
children, that they have been led into this miflake.
The fame caufe, viz. the gravity of the urine, makes
the bladder of a different form in brutes ; in their
horizontal pofition, the cervix, from which the ure-
thra is continued, is higher than its fundus, the u-
rine mud therefore diftend and dilate the inoft de-
pending part by its weight.

As to its connexion, it is fattened to the abdomi-
nal mufcles by a procefs of the 'peritoneum, and that
membrane is extended quite over it ; whereas in us
its fuperior and pofterior parts are only covered by
it : Hence in man alone the high operation of litho -
temy can be performed without hazard of opening
the cavity of the abdomen. Had the peritoneum been
fpread over the bladJer in its whole extent, the
weight of the vifiera in our eredt pofture would have
fo bore upon it, that they would not have allowed
any confiderable quantity of urine to be collected
there ; but we muft have been obliged to difcharge
its contents too frequently to be confiftent with the
functions of a focial life. Whereas by means of the
peritoneum the urine is now collected in fufficient
quantity, the vifeera not gravitating this way.

You may take it for a general rule, that thofe
creatures that feed upon animal food have their blad-
der more mufcular and confidcrably ftronger, and

lefs

-i

COMPARATIVE ANATOMY.

i5

lefs capacious than thofe that live on vegetables, fuch
as horfes, cows, fwine, 6c. whofe bladder of urin
h perfectly membranous, and very large l his is
wifely adapted to the nature of their food for m
thefe firft, as all their juices are more acrid, lo in a
particular manner their urine becomes exalted,
which as its remora might be of very ill confequence,
mu ft neceflarily be quickly expelled. '1 his is chiefly
effected by its ftimulating this vifcus more ftrongly to
contraa, and fo difcharge its contents. 1 hat a //i-
fnulus is one of the principal caufes of the excretion
of urine, we learn from the common faline diuretic
medicines that are given, which are diftolved into
the ferum of the blood, and carried down by the
kidneys to the bladder : 1 he fame appears likewife
from the application of cantharides, or without any
of thefe, when the parts are made more fenlible, as
in an excoriation of the bladder, there is a frequent
defire to make water. Accordingly we find thefe
animals evacuate their urine much more frequently
than man, or any other creature that lives on vege-
table food. And if thefe creatures, whofe fluids
have already a tendency to putrefattion, are expoled
to heat or hunger, the liquids muft for a confidera-
ble time undergo the actions of the containing vef-
fels, and frequently perform the courfe of the cir-
culation without any new fupplies of food ; by which
the fluids becoming more and more acrid, the crea-
ture is apt to fall into feverifh and putrid difeafes ;
and in fa<ft we find that thofe caufes are fufficient
to produce that fatal and melancholy diftemper, the
rabies canina , vu 'pitta , 6c. in thefe animals ; whereas
thofe that feed on vegetable food feldom or never
contract thefe difeafes but by mfeftion.

The fpermatic velfels are much the fame way dif«
pofed as in us ; they are contained within the cavity
of the abdomen , as the guts are within the peritoneum ,
which is Ipread over them, and from which they have
a membrane like a mefentery , fo hang loofe and pen-
dulous in the abdomen .* Whereas in us they are con-

C 2 tained

ifl COMPARATIVE ANATOMY.

tamed m the cellular part of the peritoneum, which
js teule y Itrerched over them. At their pafTnoe out
of the lower belly, there appears a plain perforation
or holes, and 'from obltrving th:s in quadrupeds has
arifen the falfe notion of hernia or rupture among
authors. 1 his opening is of no difadvantage to
them, but evidently would have been to us, for
from the weight of our vifccra and our continually
gravitating upon thefe holes, we mult have perpetu-
ally la oured under entcroccles ; this they are in no
hazard of, lince in them this paflage is at the higheft
part of thetr belly, and in their horizontal poiture,
the vifeera cannot bear upon it : And to prevent
even the fmalleft hazard, there is a loofe pendu-
lous femilunar flap of fat which ferves two ufes, as
it both hinders the intt/fines from getting into the
paflage, and alio the courfe of the fluids from being
flopped in the veflels, which is fecured in us by the
cellu'ar fuhflance and tenfe peritoneum .

I he feptum medium , or conjunction of the two
tunics, is the fame as in men. 1 here is next a
paflage quite down. into the cavity, where the tejli-
cles lie. Had the fame ftruChire obtained in man,
by the cohdant drilling down of the liquor which is
fecerned for the lubricating of the guts, we lliould
always have laboured under an hydrocele; but their
pofture fecures them from any hazard of this kind ;
indeed your very fat lap-dogs, who confequently
have au overgrow a omentum , are fometimes troubled
with au epiplocele

i he ferotum is fhorter and not fo pendulous as the
human, this it has in common with all the dog kind
that want the veftcvLt feminales , who have it pretty
clofe tucked up, that the feed at each copulation
might the fooner be brought from the tejies, thus in
fume meafure fupplying the place of the veftcuU fc.
niinales; for the courfe of the feed through the vafa
deferentia is thus fhortened by placing the fecerning
veflels nearer the excretory organs. Ibis at the

fame

COMPARATIVE ANATOMY- 17

Fame time explains the reafon why this creatuie is fo
tedious in copulation.

The ftriitture of the tejlicles is much the Fame
with the human ; as are likewife the corpus pyramid
dale varicofum or pampiniforme, and the epididymis or
excretory veflel of the tejhcle ; the vaja de^erentea
enter the abdomen where the blood veflels come out,
and palling along the upper part of the bladder,
are infer ted a little below the bulbous part of the
urethra .

The praputium has two mufcles fixed to it ; one
that aril'es from the fphinhler ani, and is inferred all
along the penis, and this is called retractor prseputii ;
but the other, whole office is direftly contrary to
this, is cutaneous, and leems to take its origin from
the mufcles of the abdomen, or rather to be a pro-
duction of their tunica carnofa. 1 he corpora caver •
nofa rife much in the fame way as the human ; but
thele foon terminate, and the reft is fupplied by a
triangular bone, in the inferior part of which there
is a groove excavated for lodging the urethra . "I here
are upon the penis two protuberant bulbous flelhy
fubftances, at the back of which are two veins,
which by the e restores penis are contprelTed in the
time ef coition, and the circulation being ftopt, the
blood diltends the large cavernous bodies : After the
penis is thus fwelled, the vagina, by its contraction,
gripes it clofely, and fo the male is kept in addon
fome time contrary to his will, till time be given
for bringing a quantity of feed fufficient to impreg-
nate the female ; and chus by that orgafmus veneris
of the female organs, the want of the veficulte femi -
Males are in fome meafure lupphed. But as it would
be a very uneafy pofture for the dog to fupport him-
felf folely upon Ins hinder feet, and for the bitch to
lupport the weight of the dog for fo long a time; there*
fore as foon as the bulbous bodiesarelufficiently tilled,
he gets off and turns averfe to her; had then the penis
been pliable as in other animals, the urethra muft of
neceility have been compreffed by this twifting, and

C 3 consequently

1 8 COMPARATIVE ANATOMY.

confequently the courfe of the feed intercepted ; but
this is wifely provided againft by the urethra' s being
formed in the hollow of the bone. After the ernilt
lion of the feed, the parts turn fiaccidr the circula.
lion is reflored, and the bulbous parts can be eafily
extended.

1 he pr.Jlrata feems here divided into two, which
are proportionally larger than the human, and afford
a greater quantity of that liquid.

1 he uterus of multifarious animals is little elfe but
a continuation of their vagina , only feparated from
it by a fmall ring or value . From the uterus two
long canals mount upon the loins, in which the foetus's
are lodged ; thefe are divided inrio different [acs,
which are ftrongly eonltri&ed betwixt each foetus ,
yet thefe coarfcions give way in the time of birth.
From thefe go out the tubatfilIopiarue, fo* that the
o-uaria come to lodge pretty near the kidneys.

We ought next to examine the ftrufture of the
thorax and its contents ; but firft it may not be a-
mifs to remark of the diaphragm in its natural
fnuation, that it is in general mure lool'e and free
than the human, which is owing to its connetflbn
with the neighbouring parrs in a different manner from
ours ; the human diaplsragrn is connected to the
pericardium , which again by the intervention of the
tnediaf inum is tied to the Jlernum, Jpiae, Sec. but here
there is fome ddtance between the diaphragm and
pericardium. We obferve further that its middle
parr is much more moveable, and the tendinous parts
not fo large. And indeed it W3S neceflary their
diaphragm lhould be fomewhat loofe, they making
more ule of it in difficult refpiration than man. 1 his
we may oblerve by the ftrong heaving of the
flanks of an horfe or dog when out of breath ;
which correfponds to the riling of the ribs in us.

The difpofnion and fnuation of the mamma vary
as they bear one or more young. l hofe of the
uniparous kind have them placed between the pofte-
j-ior extremities, which in them is the hightft part of

their

COMPARATIVE ANATOMY. i-g-

t'neir bodies, whereby their young get at them with-
out the inconvenience of kneeling ; neverthelefs,
when the creatures are of no great fize, and their
bread large, as in iheep, the young ones are to take
this pollure. In multifarious animals they muff have a
great number of nipples, that their feveral young ones
may have room at the fame time, and thefe diipofed
over both thorax and abdomen ; and the creatures
generally lye down when their young are to
be fuckled, that they may give them the mod favour-
able fttuation. From th.a it does nor appear to be
from any particular fitnefs of the veffels at certain
places, for giving a proper nouriihment to the child,
that the breads are fo placed in women, as we find
them, bur really from that fmiatk>n being the moft
convenient, both for mother and infant.

I he Jlernum is very narrow, and conlids of a great
number of fmalL bones, moveable every way, which
always happens in creatures that have a great mo-
bility in their fyine. 1 he ribs are (freighter and by
no means fo convex as the human, whereby in re-
fpiration the motion forward will very little enlarge
their thirax, which is' compenfated by the greater
mobility of their diaphragm : fo our thorax is prind-
pally enlarged according to its breadth and depth,
and theirs according to its length. The want of
clavicles ,. and the confecjuen; falling in of the anterior
extremities upon the ehed, may contribute fomewhat
to the llreightnefs of the ribs.

The mediajlinum in this creature is pretty broad,
whereas the human being fo narrow has occafioned
a dilpute whether there be fuch a thing or not.
7 he pericardium is not here contiguous to the dia-
phragm, but there is an inch of diilance betwixt them,
in which place the linall lobe of the lungs lodges, and
by this means the liver, &c. of this animal, though
continually prefling upon the diaphragm, yet cannot
didurb the heart’s motion.

1 he heart is fjtuated with its point almod dirg$ly
downwards, according to the creature’s pofture, t?nd

is

Qfo

GOMPARA1 IVE ANATOMY.

is but very little inclined to the left-lide. Its poiitt
'is much lharper, and its* fit ape more corioidal than the
human. Here the names of right and left ventricles are
proper enough, though nor fo in the human, which
ought rather to be called anterior and polterior, or
fuperior and inferior. 1 he animal .has the vena cava
of a coniiderable length within the thorax, having
near the whole length of the heart to run over ere
it gets at the fmus loturrianus dexter. In men, as
foon as it pierces the diaphragm, fo foon it enters the
pericardium, which is firmly attached to it, and im-
mediately gets into the fmus lower] amt s ; which fmus
hi the human fubject, by the oblique (kuation of the
heart, is almoft contiguous to the diaphragm , and by
this we difeover that feveral authors have taken their
delineations of the human heart from brutes, which
rs eafily detected by the fhape and litnation of the
heart, and long vena cava wirhin the thorax. T his
was one of the faults of the curious wax works, that
vwere lhewn at London and Park, which was plainly
tdken from a cdw.

This fituation of the heart of the creature agrees
belt with the fbnpe of its thorax , which is lower than'
the abdomen.

The egrefs cf the large blood- veffels from the
heart is fomewhat different from the human, for here
the left fubclavian comes off firft, and then a large
trunk runs fome way upwards before it gives off the
.left carotid, and fplits into the carotid and fubclavian
of the right fide : So that neither here, properly
fpedkirig, is there an aorta afeendetts, more than in
the human, but this name has probably been impofed
upon it from obferving this in a cow, where, indeed
there is an afeending and defeending aorta.

From this fpeciality of the diftribution of the vef-
fels of the right-fide1, which happens, though not in
fo great . a degree, -in the human fubjeft, we may
perhaps in fome meafure account for the general
gnjiperftrength, readinefs or faculty of motion which
is obfervable in the right arm, I believe upon

meafuring

COMPARATIVE ANATOMY. 21

irreafuring the Tides of the veffels, the furface of the
united trunk of the right fubclavian and carotid is
refs than that of the left fubclavian and carotid , as
they are feparated ; if To, the refiftance to the blood
m nfl 'be lefs in that common trunk, than in the left
fubclavian and carotid ; but if the ret /fiance be hnaller,
the abfolute force with which the blood is fent from
the heart being equal, there mud necefTnrily be a
greater quantity of blood fent through them in a gi-
ven time. And as the ftrength of the mufcles is,
cateris paribus , as the quantity of blood fent inro
them in a given time, thofe of the right- arm
will be flronger than thofe of the left. Now chil-
dren being confcious of this fuperior ftrength, ufe the
right upon all occafions, and thus from ufe comes
that great difference which is fo obfervable. That
this is a fofficient caufe Teems evident from faff ; far
what a difference is there betwixt the right and left-
arm of one who has played much at tennis ? view
but the arms of a blackfmith, and legs of a foot-
man, and you’ll Toon be convinced of this effedf ari-
fing from ufing them. But if by any accident the right-
arm is kept from aiftion for fome time, the other
from being ufed gets the better, and thofe people are
left handed ; For it is not to be imagined that the
fmall odds in the original formation of the vefTels
fbould be fofficient to refift the effect of ufe and ha-
bit, (inftances of the contrary occur every day ;) his
enough for our prefent argument that where no
means are ufed to oppofe it, the odds are fufficient
to determine the choice in favour of the right. Now
becaufe it is natural to begin with the leg correfpon-
ding to the hand we have moft power of; this is
what gives alfo a fupcriority to the right leg.

This difference is not peculiar to man, but is ftill
more obfervable in thofe creatures, in whom the fame
mechanifm does obtain in a greater degree. Do but
obierve a dog at a trot, how he bears forwards with
his right Tide, or look at him when a-feraping up any
thing, and you will pfefently fee that he ufes his

right

I* COMPARATIVE ANATOMY.

right much oftner than he does his left-foot. Some-
thing analogous to this may be obferved in horfes.

The thymus of this creature is proportionally
much larger than ours, whereas the glandula thyroidea
is much lefs, and it is generally remarked, that thefe
two glands do thus always l'upply the place of each
other : that is, in fuch animals as have a large
thymus ; the glandula thyroidea is fmaller, and vice
verfa. Hence we are naturally led to afcribe the
fame life to both, viz. the feparation of a thin lymph
for diluting the chyle in the thoracic duff, before it
be poured into the blood ; then if we confider the
different formation of the thorax in both, we fhall
readily account for the variety in the bulk of thefe
two glands. Refpiratton being chiefly perform-
ed in man by the widening of the theft, the lungs
at every infpiration mull prefs upon the thymus f
and confequcntly dimmifh it ; but the diaphragm
yielding more in the dog’s infpiration, this gland is
not fo much prefled by the lungs, and fo will be
larger, and hence the glandula thyroidea will be
proportionably lefs : Again, from the pofture of this
creature, we fliall fee that it was much more conve-
nient for a dog to have the moll part of the diluting.
lymph fupplied by the thymus, ftnce the neck being
frequently in a delcending pofture, the lymph of the
thyroid gland would have a very difadvantageous
courfe to get to the thoracic duEl : whereas in the
human body, the thymus is really below the laEleal
canal, where it makes its curvature before it opens
into the fubclavian, and confequently there is a necef-
fityofa conlklerable fliare of the diluting liquor being
fu. nilhed by the thyroid gland, which is fituated much
higher, fo that its lymph has the advantage of a per-
pendicular defcent.

We may here obferve, that the thoracic dufl in a
dog has no curvature before it enters the fubclavian
vein. The horizontal pofition of this animal allow-
ing a favourable enough courfe to the chyle, fo as not
to need that turn to force its paflage into the blood.
The Jungs of this creature are divided into more nu-
merous

COMPARATIVE ANATOMY. 23

tnerous lobes and deeper than they are in man, for
the fame reafon as the liver 1 he left fide of the
thorax in this animal bears a greater proportion to the
right than in man, the one being nearly as three to
two, the other as four to three.

We look on it as a general rule, that all quadru »
peds, as having occafion to gather their food from
the ground, are provided with longer necks than
man ; but as a long neck not only gives the advan-
tage of too long a lever to the weight of the head,
but alfo when the animal is gathering his food, makes
the brain in danger of being opprefTed with too great
a quantity of blood, by the liquor in thefe arteries
having the advantage of a defcent, while that in the
veins mull remount a confiderable wav contrary to
its own gravity, it was therefore neceflary that a part
of the lfength of the neck fhould be fupplied by the
length of the jaws. Thus we fee horles, cows, &c.
who have no occafion for opening their mouths very
wide, yet have long jaws. Bull dogs indeed, and
fnch animals as have occafion for very ftrong jaws,
mult of necelfity have them fhort; becaufe the long-
er they are, the refinance to be overcome atts with a
longer lever. Another exception to this general rule is,
fuch animals as are furniilied with fome'thing analogous
to hands to convey their food to their mouths, as cats,
apes, i*?c. i he teeth of this creature plainly Ihew it
to be of the carnivorous kind, for there are none of
them made for grinding their food, but only for tear-
ing and dividing it. Even its pofterior teeth are not
formed with rough broad furfaces as ours are; but
are ma'de confiderably fharper, and prefs over one
another when the mouth is fhut, that fo they may
take the firmer hold of whatever comes betwixt
them.

The tongue, in confequence of the length of the
jaws, is much longer than ours ; and as this creature
feeds with his head in a depending pofture, the bolus
would always be in danger of falling out of the
mouth, were it not for feveral prominences placed

moftly

24 COMPARATIVE ANATOMY.

moftly at the root of th© tongue, and crooked back-
wards in fuch a manner, as to allow any thing to
prefs eafily down to the jaws, but to hinder its re-
turn. In fome animals who feed

thefe under hooks are (till more
feveral large fifhes, where they are almoft as farge
£S their teeth in the fore part of their mouth, and near
as firm and ftrong.

When we open the mouth, we fee the aiHygdals
very prominent in the pofterior part of it, fo that it
would appear at fir.il view, that thefe were inconve-
niently placed, as being continually expofed to inju-
ries from the hard fubitances. this creature fwallows ;
but upon, a more narrow ferutinv we find this pro-
vided for by two membranous capful a, into which the
amygdds , when prefled, can efcape and remove
themfelves from fuch injuries.

The velum pendulum palati, is in this creature con-
Gderably longer than in man, to prevent the food
from getting jnto his nol'e ; which would happen
more frequently in this animal than in man, becaufe
of its fituation while feeding.

In this fubjeeft there .s no uvula , but then the epi-
glottis, when preft down, covers the whole rirna en-
tirely, and naturally continues fo ; there is therefore
a ligament or rather mufcle that comes from the os
hyoides and root of the tongue that is infer ted into
that part of the epiglottis , where it is articulated with
the cricoid cartilage which ferves to raife it from the
rJma, though not fo flrongly but that it may with a-
finall force be clapt down again. If then in all fuch
animals as have no uvula , the epiglottis is fo ordered
as to be capable of covering the rima entirely, and
if in man the epiglottis cannot be lb preft backwards
and downwards, as to Unit up the glottis perfectly,
but leaves a fpace that can be exactly filled up by the
uvula, we may very reafonably conclude that the ufe:
of this part is to fupply this deficiency in the epi-
glottis.

on living creatures,
confpicuous, as in

In

COMPARATIVE ANATOMY. 25

In the upper part of the pharxyx, behind the cri-
coid cartilage, there is a pretty large gland to be
found, which ferves not only for the reparation of a
mutous liquor, to lubricate the bolus as it pafles this
way, but alfo fupphes the place of a valve, to hinder
the food from regurgitating into the mouth, which it
would be apt to do by realon of the defeending litu-
atiori of the creature’s head.

The ccfophagus is formed pretty much in the fame
way as the human ; authors indeed generally allege,
that quadrupeds have their gullet cotnpofed of a
double row of fpiral fibres deculling one another, but
this is proper to ruminating animals, who have occa-
sion for fuch a decollation of fibres. 1 he action of
thefe you may eafily obferve in a cow chewing her
cud.

1 he nofe is generally longer than in man, and its
external paffage much narrower. 1 he internal
ftructure is alfo better adapted for an acute Knelling,
having a larger convoluted iurface on which the
membraua fcheideriana is fpread, and this is to be ob-
ferved in molt quadrupeds , who have the ojja JpongioJk
commonly large, and thele too divided into a great
number of excelfively fine thin lamella. 1 he ele-
phant, which has a head pretty large in proportion
to its body, has the greateft part of it taken up with
the cavity of the nole and frontal finufies , which laft
extend almolt over their whole head, and leaves but a
fmall cavity for their brains. A very nice fenfe of fmel-
ling w as not fo abfolutely necefTary for man, who has
judgment and experience to diredl him in the choice
of his food ; whereas brutes, who have only their
fenfes, mull: have thele of necellity acute, fome having
one lenfe in greater perfection than others, according
to their different way of life. We not only conclude
a priori from the large expanded membrana fcheide-
riana that their lenfe of fmelling is very acute, but
w’e find it fo by cows and horfes diltinguilhing fo
readily betwixt noxious and wholefome herbs, which
they do principally by this fenfe,
h \ p Th3

26

•COMPARATIVE ANATOMY.

The external ear in different quadrupeds is diffe-
rently framed, but always calculated to the creature’s
manner of life : In fliape it commonly refembles the
oblique feffion of a cone from near the apex to the
bafts. Hares and fuch other animals as arc daily ex-
pofed to infults from beads of prey, have large ears
dire&ed backwards, their eves warning them of any
danger before ; rapacious animals, on the other
hand, have their ears placed direftly forwards, as
we fee in the lion, cat, bV. 1 he flow hounds and
other animals that are deligned to hear molt dillinctly
the founds coming from below, have their ears flang-
ing downwards. Man again, who muft equally hear
founds coining from all quarters, but efpecially fuch
as are fefit from about h'i6 own height, has his exter-
nal ear placed in a vertical manner, fomewhat turned
forward. In ihort, wherever we fee a fpeciality in
the rhake of this organ in any creature, we (hall
with very little reflection difeover this form to be
more convenient for that creature than another.
There are fome differences to be obferved in the
itructure of the internal ear in different animals ; but
we know fo very little of the ufe of the particular
parts of that organ in the human iubjecr, that it is al-
together impoflible to affign realons lor thele varia-
tions in other creatures.

All quadrupeds have at the internal canthus of the
eye, a ftrong firm membtatie with a cartilaginous edge,
which may be made to cover Come part of their eye,
and this is greater or lefs in different animals, as their
eyes are more or lefs expofed to dangers in fearching
after their food : this membrana niElitans , as it is cal-
led is not very large in this animal ; cows and horfes
have it fo large as to cover one half of the eye like a
curtain, and at the fame time is tranlparent enough
to allow abundance of the rays of light to pafs
through it : filhes have a cuticle always over their
eyes, as they are ever in danger in that inconflant
element. In this then we may alio obferve a fort of
gradation*

COMPARATIVE ANATOMY. 27

AH quadrupeds have a feventh mufcle belonging
to the eye, called fufpenforius. It furrounds almoft the
whole optic nerve, and is fixed into ihe/c/er^rcoatas the
others are; its ufe is to fultaiil the weight of the g.obele
of the eye, and prevent the optic nerve being too mucti

ftretched, without obliging the four ftraight mulcts .
to be in a continual contraction, which would be in-
convenient. At the fame time this mufcle may be
brought to a (Tift any of the o'her four, by caufrng
one particular portion of it to act at a time.

The next thing to be remarked is the figure of the
pupil, which is different in different animals, but al-
ways exactly accommodated to the creature’s way of
life. Man has it circular for obvious reafons ; an ox
has it tranfverfe, to take in a larger view of his
food ; cats again have theirs fomew'hat perpendicular,
(but can alter it pretty much) for a fimilar reafon,
and fo of the reft : the pupil of different animals
varies in widenefs, according as the internal organs
of vifion are more or lefs acute ; thus cats and owls
who feek their prey in the night, or in dark places,
(and confequently mull have their eyes fo formed as
that a few rays of light may make a lively impreffion
on the retina ), have their pupils in day time contract-
ed into a very narrow fpace, as a great number of
rays would opprefs their nice organs, while in the
night they dilate conftderably. In the fame way
when the retina is inflamed, a great number of rays
of light would occafion a painful feniation, therefore
the pupil is contracted ; on the contrary, in dying
people, or in a beginning amour efts , it is greatly di-
lated, as the eyes on fuch occations are very difficultly
afteCted, and as it were infenfihle.

The poftcrior part of the choroid coat, which is
called tapetum, is of different colours in different crea-
tures. Oxen feeding moftly on grafs have this
membrane of a green colour, that it may refleCt upon
the retina all the rays of light which come from ob-
jects of that colour, while other rays are obfeured :
thus the animal fees its food better than other objects.

D 2 Cats

2 8 COMPARATIVE A\ ATOMY.

Cats and ov Is have their tapetum of a vhitifh colour,
and for the fame reafonshave the pupil very dilatable,
and their organs of vifion acute ; and we ilial) find
that all animals fee more or lefs diltindly in the dark,
according as their tapetum approaches nearer to a
white or black colour. i hus dogs who have it of a
greyilh colour diftinguilh objects better in the night
than man, vvhofe tapetum is dark brown, and who, I
believe, f£ts wot ft in the dark of anv creature, it
being originally designed that he fhould red from all
kinds of employments in the night rime. The dif-
ference then of the colour of the tapetum, as indeed the
fabric of any other part in different creatures, always
depends on feme particular advantage accruing to
the animal ifi its peculiar manner of life from this lin-
gtflarity.

We fhall now proceed to the brain, which we re-
mark in the firft place is proportionally much fmaller
in all quadrupeds than the human. 1 he reafon of
which may be, that as thofe creatures for the moft
part feek their food with their heads in a depending
pofture, this fit nation would make ic very inconve-
nient for the brain itlelf to fend its animal fpirits (or
its influence and energy, let that be what it will)
through the nerves, lo that it was necefTary they
fliould be fuppiicd from fomewhere elfe, and confe-
quently there Was no reafon for the brain itfelf be’ng
of a great bulk. As a confirmation of this theory,
we find that the intetccjtal and eight pair of nerves,
which ferve the vital organs in the human body,
take their origin from the encephalon, which in quadra
peds cone tnollly from the theca vertebras urn. Again,
there was no fuch ocrafion for fo great a quantity
of brain's in thofe ahimals as in mail; feeing in them
all its energy is employed in their progreflion, while
iftati has great wade of fpirits in the exercif'e of his
rtafonand intellectual faculties. And betides all this,
a great bulky brain would be inconvenient to thefe
creatures, in fo far as it would add confiderably to
the weight of the head, wh'ch having the advantage

29

COMPARATIVE ANATOMY.

a lone lever to aft with, would require a much great-
er force to fupport it than now it dees; foi the heat
of the greatelt parts of quadrupeds are not near fo
heavy as they would at fight feem to be, from the
J/nus frontales being produced a great way upwards
to enlarge the organs of fmelling.

The pits in the anterior part of their ikulls are
much more ccnfpicuous than in the human cranium,
which may be occafioned by the depending pohure
of thefe creatures heads, while they gather their
food : The brain at this time gravitating much on the
bones while they are as yet fott, will gradually make
tmpreffions upon them at thefe places where it riles
into eminencies. 1 his is prevented in man moiily by
his erect polture.

'1 he falx is not near fo large in quadrupeds as
in man, as they have little occafion to be on either
fide, and the two hanifphcres of the brain are in a
great rneafure hindered from juftling again ft one an-
other in violent motions, by the brain’s infmuating

itfelf into the above-mentioned pits.

The feconcl procefs of the dura mater , or tentorium
cerebello fuperexpanfum, is confiderably thicker and
ftronger in molt quadrupeds than in man, efpecially
in fuch of them as are very fwift of foot, as hares
and rabbits, and that moft when they are old. 1 his
membrane is generally ollified, that it may the more
effectually keep off the weight of the fuperincumbent
brain from the cerebellum in their rapid motions^
which otherwife would be of bad conlequence.

The olfactory nerves are very large, and juftly de-
ferve the name of proof us manul laris. 1 hey are

hollow, and confilt of a medullary and cineritious
fubftance, and at firft fight appear to be anterior
ventricles of the brain produced ; but in man they
are fmall, and without any difcernable cavity. a he
reafon of this is pretty evident, it v. e lOiilider how
this animal’s head is (itnated ; for the l\mph co timi-
ally gravitating upon the inferior par of the ventricles
may thus elongate and prodjuce them : but from this

D 3 very

$o COMPARATIVE ANATOMY.

very inferior part the olfaElory nerves rife, and are
fent immediately through the os ethmoides into the
nofe. Hence the antients thinking they were con-
tinued hollow into the uofe, believed they were the
emut: Stories of the brain ; in the brain of iheep which
by its linn texture is the belt lubject of any for
fearching into the llfu&ure of this part, we evidently
fee, that the name of the ftgmotd cavities was very
properly applied by the antients to the lateral ven*
triclfcs of the brain, which are really of a greater
extent than they are ordinarily painted by the anato-
jnifts, reaching farther backwards and forwards again
under the fu bitan; e of the brain.

l:fie nates ana tejles deferve this name much better
here than in the hum in body with refpeft to each
other. They are here ulfo of different colours, the
n ites being of the colour of the cortical, and the tejles
of the medullary fubltancc of the brain : Whereas
m man they arc hoth of one colour The reafon of
t'.iefe differences, and others of the like nature to be
met with, 1 lliall not pretend to determine ; for we
have hitherto filch an imperfect knowledge of the
brain itfclf, that we arc entirely ignorant of the va-
rious ufes of its ‘different parts ; we ma> in general
conclude, that the varying in one animal, from what
it is in another, is fitted to the creature’s particular
way of living.

The rete mirabile gnteni, fituated on each fide of
the fella turcica , about which there has been fo much
uifpute, is more remarkable in quadrupeds than in the
human filbjefb though it is certainly to he found there
too ; notwithstanding leveral anatomills have denied
its exigence. I he ure indeed which Galen aferibes
to it is frivolous, and not well grounded ; for he will
have this plexus of the veifels ferve for checking the
iaipetuofity of the braio, but it is evident this cannot
be the ufe of it ; if indeed the whole carotid artery
had fplit into fuch final 1 vefTels as compole this net-
work, the motion of the blood would certainly have
been retarded in it j but this is not the cafe, fer it

COMPARATIVE ANATOMY*

3*

only fends off a few finall twigs to compofe the plexus
at its entry into the cranium, and the branches going
out from this fame plexus , are diitribured to the
neighbouring nerves : Among the reft it gives forne
twigs to the ophthalmic branch of the fifth pair.
It is this diftribution of tliefe arteries makes it fo
difficult to determine whether there is a communication
between the intercoflal and that nerve ; fur if- you
diffeft the parts in a recent fubjecl, you would at firft
view affirm, that there is an anajhmofis ; but when
the carotid artery is injected, and the plexus filled
with the fubtife liquor, thefe branches, which for-
merly feemed to be nerves, have now the appearance
of arteries by the veflels.of their coats being injected.
1 have been at great pains to enquire into the matter,
but could never pofitnely determine if there is fuch
an anaftomofis as is deferibed by a great many au»
thors, and fo very diftincUy delineated by Dr Lower
in Willis’s treatile of the nerves, and Mr Vieuflen,
only it Teems molt probable from the lympathy ob>
fervable between them that there is fuch an anajlo. *
tnofs.

1 he ftrufture of the brain diftering*but very little
In all quadrupeds , it will be needlefs to examine it ia
any other.

The Anatomy of a Co vs.

THE next fpecies of quadrupeds we propofed tt*
cotilider was the ruminant kind, of which we
have an example in a cow, and accordingly fhali
tak? the foetus of the animal in utero, that we may
firft remark feme things that are peculiar to it if)
that ftate, and afterwards proceed to examine its
■vifeera as a ruminant animal • firft then as a foetus ':

1 he form of a cow’s uterus differs from the human
in having two pretty large cornua. 1 his is common
to it with other brutes, for a bitch has two long
cornua uteri ; but thefe again differ (as being multi.

parous

COMPARA I'lVE ANATOMY.

J2

parous and uniparous ) in this, that in the bitch’s for-
ms* the foetus's are contained, whereas here there is
only part of the fecundities , being moltly the allantois
with the included liquor. The mufcular fibres of
the uterus are more eaiily difeovered ; its internal
furface has a great number of fpungy, oblong, pro.
tuberant, glandular bodies fixed to it by a fine mem-
brane : Thefe are compofed of feveral large vefiels
ofthe uterus terminating here. 1 hefe are very final!,
fometimes not to be obferved at all. In an impreg..
nated uterus we can eaiily prefs out of them a chylous
mucilaginous liquor ; they are competed of a great
many procefles or digituli , and deep caverns anfwer*
ing to as many procedes and caverns of the placenta..
Their refemblance has occalioned the name of
papilla to be given them, and hence it was that Hip-
pocrates was induced to believe, that the foetus fuck’d
in utero. It is not eafy to determine, whether the
uterus grows thicker or thinner in the time ofgeilation.
The membranes it is plain (by the llretching of the
parts) mud be made thinner, but then it is as evident,
that the veflels are at that time enlarged, upon which
principally the thicknefs of any part depends ; fo
there feems to be as much gained the one way, as loll
the other. The os uteri is entirely Hint up by a
glutinous mucilaginous fnbltance, that is common to
the females of all creatures when with young; by
this the external air is excluded, which would loon
make the liquors corrupt; it alfo prevents the inflam*
mation of the membranes , and the hazard of abortion.
By this means alfo the lips of the womb are kept
from growing together, which otherwife they would
certainly at this time do. There are mucous glands
placed here to fecern this gluten, which on the break-
ing of the membranes with the contained waters make
a Japo that lubricates and waihes the parts, and makes
them eafdy yield. The firlt of. the proper involucra
of the foetus is the chorion.

The chorion is a pretty ftrong firm membrane, on
whole external furface are dil'perfed a great many red

flefliy-

COMPARATIVE ANATOMY.

33:

flefby bodies of the fame number, fize and ftrutffure
with the papilla, with which they are mutually in-
dented. They have been called coty/edones fiom
kotvM cavity. This is greatly difpnted by fome as
a name very improper, but 1 think without reafon,
fiuce the furface that is connected to the papilla is
concave, though when feparated it appears rather
convex. To Ihun all dilpute, they may be called
properly enough placentula , fince they ferve the fame
ufe as the placenta in women. The reparation of
thefe from the papilla without any dilaceration feems
to prove beyond a reply, that there can be here no
ariafiomofes betwixt the vefTels ; on their coats run a
great number of vefiels that are fent to the iieveral pla*
ccntula, on the external fide next to the uterus ; where-
as in creatures that have but owe placenta, as in the
human fubjeft, cats, dogs, SsV. the adhelion is
fomewhat firmer : The placenta are likewife joined to
the papilla in the cornua uteri. We fhall next give
the hiftory of the allantois .

This is a fine tranfparenr membrane contiguous to
the former. It is not a general involucrum of the
foetus in the mother, for it covers only a fmall part
of the amnios: It is moftly lodged in the cornua ute

rt.

In mares, bitches and cats it f’Urrounds the

arnnhs , being every where interpoled betwixt it and
the chorion. In fheep and goats it is the fame as in
this animal ; and iri fwine and rabbits it covers flill
]< Is of the amnios. This fac is probably formed by
the dilatation of the urachus, which is connected at
its other end to the fundus of the bladder, through
which it receives its contents, and the membrane is
doubled at the extremity of the canal to hinder the
return of the urine back into the bladder. Its vef-
lels are excelfively fine and few, and we cannot force
an injefled liquor farther than the beginning of this
coat. 1 his membrane is lo far analogous to the
cuticula, as not to be liable to corruption, or eafily
irritated by acrid liquors. 1 he exiftence of this
metnbrane i n women has been very warmly disputed on

both

CO M PAR ATI VE A N ATOMY.

34

both fides : Thofe who are againft its exigence de-
ny they could ever find it, and allowing it were fo,
allege, that fince the urachus is impervious, as ap-
pears by our not being able to throw liquors from
the bladder into it, or vice lerfa , it cannot 1’erve the
life that is agreed by all it does ferve in beads, and
therefore in the human body there is no fuch thing :
But if we confider on the other hand, that firlt
there feetns to be the fame neceflity for fuch a refer,
voir in man as in ether animals. Secondly, that
we actually find urine contained in the bladder of
the human foetus. 1 hirdly, that urine has been e-
vacuated at the navel when the urethra was flopped,
which urine without this conduit would have fallen
into the cavity of the abdomen. Fourthly, that mid-
wives do generally remark two different forts of wa-
ters come away at the time of birth. And, laftly,
that Dr Littre and Dr Hale have given in this mem-
brane of an human fubjedl with all the other fecun«
dines enrioufly prepared, the one to the Royal Aca-
demy at Paris, the other to the Royal Society at
London, by which focieties their refpedlive accounts
are attefted, not to mention Verheyen, Heifler,
Kell, CsV. who affirm their ’having feen it, and Mr
Albinus, that famous anatomift, profefl'or at Leyden,
fhows, as I am told, to his college every year a pre-
paration of it. On all thel'e accounts I mufl own,
that it feems mod probable to me there is fuch a
membrane in the human body, although in four bo-
dies I purpofely differed, w herein 1 was affilled by

a very accurate anatorrtiil, Dr S r, 1 could

not obferve any fuch thing; however, I would ra-
ther accufe my own want of fkili, than doubt the
truth of relations fupported by fuch authentic
vouchers.

The third proper integument of the foetus is the am-
nios ; it is thinner and firmer than the chorion ; it
has numerous ramifications of the umbilical veffels
fpread upon it, the lateral branches of which fepa-
rate a liquor into its cavity. This is the proper li-
quor

COMPARATIVE ANATOMY. 35

quor of the amnios , which at firft is in a fmall quan-
tity, afterwards encreafes for fome months, then
again decreases ; and in a cow near her time the
quantity of this liquor is not above a pound. This
membrane does not enter the cornua uteri in this crea-
ture ; but for what further relates to the ftrudure
of t he inw/ucra, with the nature of the liquors con-
tained in them, 1 nuift refer to the fecond volume
of medical effays, from page 121, where you have
the fum of all we know of this matter.

There are here two vena umb'.li tales , and but one
in the human fubjecl, becaufe the extre ne branches
coming from the feveral placentuld could not unite
fo Icon as they would have done had they come all
from one cake, as in the human.

1 here is a fmall round flelhy body that fwims in
the urine of this creature, mares, c5V. called cutieu-
/a, winch is the hyponienes of the ancients. Several
idle opinions and whims have been entertained as to
its ule, but that feems to be hill unknown, or how
it is generated or nourilhed, for it has no connexion
with thei foetus or pLuentula.

Having thus confidered the feveral involucra of
tins animal in a foetus date, let 11s next obferve the
fpecialities in its internal Itruchire peculiar to a foetus .

The umbilical vein joins the vena porturum in the
capfula glijfniatta without fending off any branches
as it does in the human fu ject. I his vein foon
after birth turns to a ligament, yet there are fome
initances where it has remained pervious for feveral
years after birth, and occafioned an hemorrhage.
We may next obferve the duel called canalis venofus ,
going {freight from the capfula giifjuniana to the vena
cava ; this turns alfo afterwards to a ligament. The
umbilical arteries rife at acute angles from the imer-
nal iliacs, whatever fome may fay to the contrary :
*1 hele aifo become impervious.

i he pulmonary artery coming from the right ven-
tricle of the heart, divides into two, the fmalleft
o'.: called

36 COMPARATIVE ANATOMY.

called canalis arterhfus opens into the defcending aor-
ta « the other divides into two, to ferve the lungs
on each tide. The foramen ovale is placed in the par-
tition betwixt the right and left auricles. At the
-edge of this hole is fixed a membrane , which when
much ftretched will cover it all over, but more eafi-
-ly yields to a force that ads from the right auricle
to the left, than from the left to the right Af-
ter what has been faid we may eafily underftand
how the circulation is performed in a foetus. The
blood being brought from the placenta of the mother,
is thro vn into the capfula glijfoniana, where it is in-
timately blended with the blood in the vena porta-
rum : then part of this blood goes diredly into the
vena cava by the ductus venofus , the reft pafles
through the liver. Firft then, the whole is fent
from the vena cava into the right auricle , from whence
part of it is fent by the foramen ovale into the left
'■auricle, the reft pafles into the right ventricle, then
•into the pulmonary artery, then the greateft lhare
it receives is fent immediately into the defcending
aorta by the canalis ar ter if us, and the remainder
circulates through the lungs and is fent back by the
pulmonary veins into the left auricle , which with the
blood brought there by the foramen ovale is fent into
the left ventricle, from whence it is driven by the
aorta through the body. I he great defign of this
mechanifm is, that the whole mafs of blood might
not pal's through the collapfed lungs of the foetus,
but that part of it might pals through the foramen
ovale and canalis arterhfus without circulating at all
through the lungs.

This was the opinion that univerfally prevailed
till the end of the laft century, when it was violent-
ly oppofed by Monfieur Mery, who is very fingular
in feveral of his opinions. He will not allow that
the foramen ovale tranfmits blood from the right to
•the left auricle, but, on the contrary, from the left
to the right, and that for no other reafon hut be-
caufe he obferved the pulmonary artery in a foetus

longer

COMPARATIVE ANATOMY. 37

longer than the aorta : Mr Window endeavours to
reconcile thefe two opinions, by faying the blood
may pafs either way, and that it is here as it were
blended ; his reafon is, that on putting the heart in
water, the foramen ovale tranfmits it any way.. Mr
Rohault, profeflor of anatomy at i urin, and for-
merly one of Mery’s fcholars, ftrongly defends his
mafter and criticifes Mr Window. Whait he princi*
pally builds on is the appearance this foramen has it?
fome dried preparations: This Mr Window won’t
allow as a proof. After all I remain in the com-
mon opinion, and that for the following realons:
Eird, the pulmonary artery being larger dignifies no-
thing, fince its coats are not only thinner, and will
be more ealily didended, but alfo the reddance to
the blood in the pulmonary artery from the col*
lapfed lungs is greater than the refinance to the
blood in the aorta. Secondly, if we diould allow
any of thefe two uncommon opinions, we diould
have the right ventricle Vaftly more capacious than
the left ; for if we fnppofe the foramen ovale to be
capable of tranfmitting one half of the whole mafs
of blood in any given time, and the arteriofus as
much in the fame time, then you’ll find that, accor-
ding to Mr Mery’s opinion, the whole mafs of blood
being driven from the right ventricle into the pul-
monary artery, one third pafles by the canalu artcri -
ofus into the defcending aorta, two thirds pading
through the lungs and returning into the left auricle ,
one half of it, or one third of the whole mafs, pafles
by the foramen ovale into the right auricle, and the
other or the latl third will be feat into the left ven-
tricle, and thence expelled into the aorta , which
third, with that from the pulmonary artery by the
canalu arteriofus^ circulating through the body, are
returned unto the right auricle, where meeting with
the other third from the foramen ovale, w ith it are
lent into the right ventricle to undergo the fame
eourie. Thus the whole mals is expelled by tne
right ventricle and only one third by the left. If

E this

3« COMPARATIVE ANATOMY.

was the cafe, why is not the right ventricle three
times as large anil ftrong as the left ? Then if accor-
ding to Mr Window's fyltem the foramen ovale tranf-
mits equal quantities from both auricles , this comes
to the fame as if there were no foramen ovale at all ;
that is to fay, the whole mafs going from the 'right
auricle into the right ventricle and pulmonary artery,
one third oT the whole mafs paffes into the aorta
through the canalis arteriofus , the other two thirds
palling through the lungs return to the left ventri-
cle and auricle, to be feiit through the canalis arteri-
ofus to the right ventricle to undergo the fame fare ;
thus the right ventricle expels the w'hole mafs, the
left only one third ; but if according to the common
opinion we fuppofe the foramen ovale to convey the
blood from the right to the left auricle, then one
third palTes this way into the left ventricle, the other
two thirds are fent by the right ventricle into the
pulmonary artery, from whence one third pafles by
the canalis arteriofus into the aorta defcendens , the
other third circulates through the lungs, and is re-
turned into the left ventricle, where meeting with
that from the foramen ovale is with it expelled into
the aorta, and with the one third tranfmitted by the
canalis arteriofus returns into the auricle to run the
fame race as before. 1 hns we conclude that two
thirds are expelled by each ventricle and the whole
circulates through the body ; and hence they come
to be of pretty equal dimenllons. In all this calcu-
lation I have had no regard to the blood difcharged
from the umbilical vcjlTels ; but the greater quantity
returned by the veins, than fent out by the arteries,
ftill argues for the common opinion.

The kidneys in the foetus are compofed of diffe-
rent lobes, w-hich ferves to give us an idea of the
kidneys being a congeries of different glands ; thefe
lobes being kept contiguous by the external unm-
b'rane are prefled by the other vifcera till at length
they unite.

We

COMPARATIVE ANATOMY. 39

We come now to confider the creature as a rumi-
nant animal. There are no dentes incifores in the
upper jaw, but the gums are pretty hard, their
tongue rough, and they fupply this defeat by wrap-
~ ping their tongue round a tuft of grafs, fo prefling
it againlt the upper jaw keep it ftretched, and cut it
with the teeth of the under-jaw ; then, without
chewing, throw it down into the cefophagns , which,
in thefe creatures, conlifts of a double row of fpiral
fibres decollating one another. All animals which
ruminate muff have more ventricles than one, feme
two, fome three, our pref'ent fubjecl has no lefs
than four. The food is carried directly down into
the firft, which lies upon the left fide and is the
larged of all ; it is called ventriculus, and

xoiXtx by way of eminence. It is what is called by
the general name of paunch by the vulgar. There
are no ruga upon its internal furface ; the food, by
the force of its mufcular coat, and the liquors pour-
ed in here, is fufficiently macerated, after which ic
is forced up hence by the oefophagus into the mouth,
and there it is made very fmall by maftication ; this
is what is properly called chewing the cud or rumi-
nation ; after this it is fent down by the gullet into
the fecond, for the oefophagus opens indifferently into
both ; however the creature has a power to diredt
it into which it will. Some tell us that the drink
goes into the fecond, but that might be eafily deter-
mined by making them drink before (laughter; the
fecond Itotnach, which is the anterior and fmallett, is
called xi xgJ.pa>.o5 reticulum, the bonnet, or kiug’s-hcod.
It confilts of a great number of cells on its internal
furface of a regular pentagonal figure, like to a honey-
comb. Here the food is farther macerated, from
which it is protruded into the third, called t or
tnnafum , vulgo the »ian\p!us , becaufe the internal
furface riles up into a great many plica or folds, and
Jlratum f:iptr firatum, according to the length of this
ftomach. Some of thefe plica are further produced
into the ftomach than others, i. e. lirlt two long

E 2 ones

Ao COMPARATIVE ANATOMY.

ones on each fide, and within thefe, two fhcrter
in the middle, &t. There are feveral glands in this
ltomach which is next to the *o »,\<* in bignefs, and
from this it paffes into the fourth, whofe names are
abomnfuw, caille, or the red , which is the
name it commonly has becaufe of its colour. Cail/c
dignities curdled, and hence the French have given
that as a name to this fourth ftomach, becaufe any
milk that is taken down by young calves, from the
long remora it makes here, turns acid ; and by the
remains of the milk before taken down afliftiurr, it
is curdled. It is this fourth ftomach with the^ilk
curdled in it, that is commonly taken for earning of
milk (as they call rr), but after the bile a pancreatic
juice enter, this coagulation is not to be found which
fhews the u!e ot thcle licjuors. "1 here are other
creatures that ufe the fame food, that have not foch
a mechanifm in their digeftive organs ; horfes, afles,
tsfe. have but one ftomach where grafs’is macet ated
and a liquor for their nouriihmenc extracted, and
rhe remainder fent out by the anus very little alter,
cd. From this different ftrutfture of the ltomach in
thefe creatures, a ruminant animal will be ferved
with one third lefs food than another of equal bulk;
gra Tiers are fufficienrly acquainted with this. The
reafon is, that ruminating animals have many and
ftrong digeftive organs ; all their food is fully prepar-
ed and almoft wholly converted into chyle, but a
horfe’s ftomach is not firted for this, fo that they re-
quire a much greater quantity of food to extract
the fame nourilhment.

The guts of thefe creatures are of a confiderahLe
length in proportion to the bulk of the animal’s body,
and this confirms what we faid formerly on the-fubjeCf
of the intejlines of a dog, viz . that the length and
ca; acity of the guts were different in different ani-
mals according to the nature of their food.

The duodenum is formed here much the Time way
as in a dog, and the general intention kept in view
with regard to the mixture of the bife and -pancrea-
tic

COMPARATIVE ANATOMY. 41

tic lymph. The great gms here hardly defcrve that
name, their diameter differing very little horn mat
of the ftnall ones ; but to comperdate this,, they are
much longer proportionally than a dog’s are> hemg
convoluted in the fame way as the fmall guts are.

The cacimi is very large. . r

The fpleeti differs not much either in figure cr li-
tuation from that of a dog’s, but it is a little mere
firmly fixed to the diaphragm, there not being here
fo much danger of this vifeus' s being hurt in the

flexions of the fpine. . , .

'i he liver is not fplit into fo many lobes in this crea-
ture as either in a man or dog, which depends on
the fmall motion this creature enjoys in hi fpine,
which made luch a divifion needlefs : d his alfo con-
firms what I formerly advanced on this head.

Their veftca urinaria is of a pyramidal fhape, and
has fcarce any mufculnr fibres. It is very large and
membranaceous, for the urine of thefe creatures not
being fo acrid as that of carnivorous animals, there
was no filch occafion for expelling it lo loon.

1 his creature is provided with a loofe pendulous
ferotum, and consequently with vtficuU ftmi tides .
The female organs differ from thofe of a bitch,
moffly as to the form of the cornua uteri , which are
here converted in form of a fnail. I11 this and ail
uniparous animals they contain only part of the fe-
cundities, but in bitches and ether multiparous animals
they run (freight up in the abdomen, and contain the
foetus themfelves.

.. The fixation of the heart :s pretty much the
fame with that of a dog, only its point is rather
fharper ; in tis the heart beating continually againft
the ribs, and both ventricles going equally tar down
to the conffiiuuon of the apex it is very ubtufe, 1 ut
here the apex is made up only of the left ventricle, lio
is more acute.

The aorta in this creature is juftly divided into a-
feending and defce tiding, though this divifion is ill
founded either in a dog or man, and it has certainly

£ 3 * be«.i

42 COMPARATIVE ANATOMY".

been from this fubjett that the oMer anntomifls took
their defcriptions v. hen they made this divilion ; for
here the aorta divides into two, the alcending and
descending ; the defcending rows upwards or for-
wards, according to their pollute, for two or three
inches, before it gi es off the left / ubclav’tatt , and Hill
an inch or more before the right fubclavian comes off,
and yet Somewhat further before it divides into the
two carotids, fo that the veflels that go to the ante-
rior extremity of the right-fide, do llii! keep longer
in a common trunk with, the carotids than thofe on
the left.

Of Fowls in general.

TH E next cTafs of animals we come to confider,
are the feathered kind ; which are divided in-
to the Cranivorous and Carnivorous . But before we
go on to confider the fpecialries in the vifrera of each
kind, we muff obferve what both fpecies agree in.

Fowls have a particular covering of feathers dif-
ferent from all other creatures, but exa&ly well fuited
to their manner of life ; for it not only protects
them from the injuries of the weather, but ferves
them in their progrelhon through that thin aerial
element, they are for the mod part employed in-;
and as fome fowls live much in the water, their
feathers being continually befmeared with an oily
liquor, keeps the water from foaking into their ikins,
and fo prevents its bad effects, which it would in-
fallibly otherwife produce.

Fowls have the ftrongeft mufcles of their whole
body inferted inta their wings ; whence by the way
we may obferve that it is altogether impof-
fible for mao to buoy himfelf up into the air like birds,
even though he had propermachines in place of wings,
unlefs he were likewile provided with mufcles ftrong
enough for moving them, which he has not. In the
next jplat-C their win^s are not placed in the middle

of

COMPARATIVE ANATOMY* 43

of their bodies, but a good deal further forwards,
whence it would at firfl view appear that their heads
would be ereft, and their poilerior parts mod de-
pending, when raided in the air ; but by Aretching
out their heads, which act upon the lever of a long
neck, they alter their center of gravity pretty much,
and alfo by filling the lacs or bladders in the infiide
of their abdomen, w ith air, and expanding their tail,
they come to make the poilerior part of their bodies
confiderably higher, and thus they fly with their bo-
dies near in an horizontal lituation. Hence we find,
that if their necks are kept from being flretched out,
or if you cut away their tails, they become incapable
of flying any confiderable way. 1 lie largenels of
the wings in different fowls varies; according to the
occasions of the creature. Thus birds of prey, w'ho
mult fly a confiderably way to provide their food,
have large llrong wings; whereas domeflic birds,
who find their nourilhment almelt every where, have
very fhort and but fmall wings. The beft account
of the manner of progreflion of fowls, is given by
Alfoufus Borellus, in his treatife De Mutu Anima-
lium, and in the Religious Philofopher we have Bo-
relh’s doctrine Aripped pretty much of its mathema-
tical form. 1 lie poilerior extremities are fo fituated
as to make us at firfl think they wonid be in conti-
nual hazard of falling down forwards when they
waik, but this is prevented by their holding up their
heads and necks, and when they have occalion for
climbing up afteep place, they ftretch out their heads
and necks forwards. 1 hus we may obferve a goole en-
tering a barn door, where generally there is an a f-
cending flep, to llretcfi out its neck, which before
was railed, and incline its body forwards ; this is
laughed at by the common people, who alcribe it to
a piece of folly in the goofe, as if afraid of knocking
its head againlt the top of the door.

Carnivorous animals are provided with flrong
.crooked elaws for the catching their prey; water
fowls ule then) for lwimming, and principally for this
purpofe have a flrong firm membrane interpofed be.

t'-Vixt

44 COMPARATIVE ANATOMY.

twixt the toes. Thee- is a beautiful mechanifm to
be obferved in the toes of fowls, which is of conli-
derable life to then*; for tl>eir toes are naturally
drawn together or bended when the foot is bended ;
this perhaps proceeds from the tendons of the toes
paQTintr over in them, which is analogous tootir heels,
and when the foot is bended muft conlequently be
much ft retched ; and fince they are inferred into the
toes, mult, of necellry bend them when the foot is
bend eel, and when the foot is extended the flexors
of the roes 3re again relaxed, and they therefore ex-
panded. This is of great ufe to water fowls, for had
there been no fuels contrivance as this, they muft
have loft as much time whetv they pulled their legs
in, as they had gained by the former ftroke ; but as
the parts are now framed, whenever the cieature
draws in its foot, the toes are at the fame time bended
and contracted into lefs fpace, fo that the rdiftancc
made againft the water is not near lo great as before :
On the contrary, when they ftretch their foot, their
toes are extended, the membrane betwixt them ex-
panded, and conlequently a greater refinance made
to the water. Again, fuch fowls as live mollly m
the air, or have occasion to fuftakt tbemfelves on
branches of trees in windy weather and even in the
night time wften afleep, whi e all their mukles are
fuppofed to be in a itatc of relaxation ; fuch, 1 lay
have no more to do, but lean down the weight cf
their bodies, and their toes continue bended withotu
any ninfcleS being in aftion ; and whenever they
would ditentnngle. themfelves, they raife up he r
bodies, by which their foot, and conlequently their

toes, are extended. . , . ,

Carnivorous fow Is have their beaks long, fharp a.ul

crooked; the domeftic fowls, foch as lhc he" k’n ’
&c. have ftrong fhort beaks, commodioufly fitted o
dig up and break their food ; the water fowls apm
have long or very broad fccrop like beaks, w id
Sclent for them. 1 bejff.r*»» of fowUt.
much larger proportionally than the human, and has

COMPARATIVE ANATOMY. *5

a ridge rifing in its middle for the more commodious
origin of the mulcles that move the wings. It is
alio lefs moveable than ours, for had it been very
moveable, a -great deal of the force employed for
moving the wings Mould at every contraction of the
muffles have been loft, or elfe fome other mufcies
mult have come in piny to keep firm the Jterni/m, but
this additional weight would have been inconvenient
for their progreffton.

What other things are mod remarkable in the,
ftru&ure of the feveral vifctra , we lliail conftder ux
that common domeftic animal, the cock or hen, and
afterwards obferve the difference of their iiifccra
thylopoietica from a carnivorous fowl.

The Anatomy of a Cack.

TH E oefophagns of this creature runs down its
neck fotnewhat inclined to tht right lute and
terminates in a pretty large membranous Joe, w hich is
the ing/uvies or crop where the food is macerated and
diffolved by a liquor, feparated by the glands winch
are eaiily obferved every whereon the external ituf-
face of this, bag. 1 he effect of this inace rjat ton rna.y
be very well obferved in pigeons, who are louse tune ^
in danger of being fuffocatecl by the peale, iAc. they
feed upon, fuelling to fuch an immenie bu k in tbtir
in&luvics, that they can neither get upwards uor
downwards. If it be a favourite foul, Lt might be
preferved by opening tht foe, taking out tire peafe
and tewing up the wound.

i he food getting cut of this fee goes down by the
remaining part of the oejopbagus into the vaitticuius.
fucceniurinius or infundibulum peyeri, which is a con*
tinuation of the gullet with more numerous glands,
wh ch (eparate a liquor to dilute the food Hill more,
which at length gets into the true itomach or giz-
zard, w hich conlifts of tw o very tlrong mukles cover-
ed externally with a tendinous aponeurofist ’and lined

Oli

4 6 COMPARATIVE ANATOMY.

on the infide by a very thick firm membrane, which we
evidently difcover to be a production of the cuticula .
This might have been proved in i'ome meafure a pri-
ori, from taking notice that this membrane, which in
chicks is only a thin flight pellicle , by degrees turns
thicker and ftronger, the more attrition it luffers :
but there is no other animal fubftance, fo far as we
know, which grows more hard and thick by being
fuhjeCted to attrition, excepting the cuiicuLi. Hence
may be drawn fome kind of proof of what 1 have
fometimes affirmed concerning the tunica villofa of
the Aomach, and intejlines in the human body,
viz. that it was only a continuation of the epidermis.
Nay, all the hollow parts of the body, even arteries,
veins, &c. feein to be lined with a produftion of this
membrane or one analogous to it. 1 he uie of this in-
ternal coat of the ftomach of fowls is to defend the
more tender parts of that vifeus from the hard grains
and little flones thofe creatures take down.

I he digeflion of thele animals is performed merely
by attrition, as is evinced by many experiments. We
fee them daily take down confiderable numbers of
the molt folid rugged little flints they find, and thefe
can lerve for no other purpole than to help the tri-
turation of their aliments. After thele pebbles by
becoming Imooth are unfit for this office, they are
thrown op by the month ; hence fowls that are long
confined, though never fo well fed, turn lean for
want of thefe flones to help their digeflion; but
this was put beyond all difpute by Mr iauvry, who
gave a fpecies of metal to an oflrich, convex on one
fide, and concave on the other, but carved on both
and opening the creature’s body iome time after, it
was found that the carving on the convex fide was all
obliterated, while the engraved character remained
the fame as before on the concave fide, which was
not fubjeCted to the floinach’s preflure ; which could
not have happened had digeflion been performed by
a menjlruum , or any other way whatfoever; but may
be ealily fblved by allowing a Ample mechanical

preflure

COMPARATIVE ANATOMY. 47

preffure to take place. We are however by no
means to conclude from this, as fome have too raflily
done, that in the human body digeftion is performed
by a fimple attrition, otherwife we may with equal
ftrength of reafon, by as good arguments drawn
from what is obfervetl in fifhes, prove that the aliments
are diffolved in our ftomachs by the action of a merf
flruum : But this method of reafoning is very faulty,
nor can it ever bring us to the true folution of any
philofophica! or medical problem. It is very plain,
fince the ftrufture of the pants of the human ftomach
are fo very different from that of this creature, that
it is foolilh and unreafonable to imagine both of th r»
capable "of producing the fame effects At each end
of the ftomach there are as it were two particular
facs of a different texture from the reft of the ito-
mach, not confiding of ltrong mttfcular fibres ; they
feem to be receptacles for the ilones (efpecially at the
end which is fartheft from the orifice) while the di-
gefted aliment is protruded into the inteflines.

The duodenum begins pretty near the fame place,
at which the oesophagus enters ; yet notwithstanding
the vicinity of thefe two tubes, the aliments are in no
danger of getting out before they are pert'edly digeft^
ed, by reafon of a protuberance or feptum medium be-
twixt the orifices ; and in thofc creatures who have
iuch a firong mulcular ftomach, it is a matter of great"
indifference, whether the entry of the cefophagus or
py’crus be higheft, provi led that the entry from the
cefpha'gus does not allow the food to regurgitate, fince
the torce of the ftomach can eaiily protrude it to-
wards the duodenum . 1 his gut is moftly in the right

fide, and hangs pendulous in their abdomen , having
its two extremities fixed to the liver. The duttus
communis choledochus enters near its termination, where
it mounts up again to be fixed to the liver ; and left,
by .the contraction of the intefiines, the bile lhould
pals over without being intimately blended with
the chyle, that dut l enters downwards contrary to the
Qourle of the food, and contrary to what is obferved

COMPARATIVE ANATOMY.

48

$n aWy of the animals we have mentioned yet. But
ftill the general intention is kept in view, in allowing
thefe juices the faireft chance of being intimately
blended with the food.

The forth guts are -proportionally larger than thofe
of carnivorous -birds, for the general caufe already af-
figned. At the end of the ilium they have two
large irtteftina aeca, one on each fide, which ferve as
refervoirs to the fxces, which after fome remora there
regurgitate into what foon becomes the re Phan, which,
together with the excretories of the urine, and or-
gans of generation, empties itfelf into the common
cloaca. The fmall intefines are tonnefted by a long
loofe mefehtery, which has little or no fat accompany-
ing the blood veflels, there being no hazard of the
blood’s being (topped. There are no lafteal veflels,
glandul t vug a or pancreas ajjellii to be obferved here.
The tneferuic' wins are proportionally very large, if
you either compare them with the correfponding ar-
teries, or conlider them with refpeft to the guts
themfelves. The want of laetenls, &c. is fupplied
by thefe veins. As a proof of thefe having a com-
munication with the guts, in larger fowls the guts
can be diftended by blowing in at the meferaic vein •
and from this difference of ftrufture, the ufe of the
glandul* vag*. Sec. can eaft'y be afligned, viz. the
chyle in thele animals that have 'areals, being to be
ntfxed with the blood in a conliderable quantity at a
rime, left its particles fliould attraft one another
ftrongly, and fo hinder this mixture ; it was
therefore neceffaiy it Jhoultl he well diluted by the
humores iniquilini, which hear a very great propor-
tion to the quantity of pure chyle ; fince the lymph
from the inferior extremities abdominal vifeera , neck,
&V. are poured into it. Here there was no hazard of
any fuch iiconvenicncv by the chyle being mixed
with the blood in (mall proportion from the iin-
menfe number of the fmall extremities of the tiicferaic
veins.

The

COMPARATIVE ANATOMY. 49

The pancreas in the creature lies betwixt the two
folds of the duodenum , and fends two or three duels
into this gut pretty near the biliary.

1 he fpleen is here of a round globular figure, fi-
tuated between the liver and ftomach, and betwixt
thefe and the back bone it enjoys the fame proper-
ties as in other animals, viz. large blood veflels, &c.
All its blood is lent into the vena portarum, and has
a perpetual conquaflation. It has excretory as far as
we know. Their liver is divided into two equal lobes
by a pellucid membrane, running according to the length
of their body ; and hence we may obferve, that it is
not proper to that bowel :o lie on the right fide,
which is ft ill more confirmed by what we obferve in
fillaes, where it almolt lies in the left fide.

The fhape of their gall bladder is not much diffe-
rent from that of quadrupeds, but is thought to be
longer in proportion to the fize of the animal, and
is farther removed from the liver ; though in fifties
it is Hill further removed, not being at all contiguous;
and in them the duclus hepaticus and cxjlicus do not
unite till juft at the entry into the gut. In thefe
animals, viz. fifties, there feems to be no way of
the bile getting into the gall bladder but by regurgi-
tation.

The principal difference to be remarked in their
heart is the w'ant of the valvula tricufpides, and their
place being fupplied by one flefliy flap.

1 he lungs are not loole within the cavity of the
thorax, but fixed to the bone all the way ; neither
are they divitfled into lobes, as in thofe animals that
have a large motion in their J pine . They are two
red fpor.gy bodies covered with a membrane that is
pervious, and communicates with the large veficles
or air bags that are difperfed over their whole abdo-
men, which veficles lerve two very confiderabie ules ;
the one is to render their bodies fpecifically light,
when they have a mind to afeend and buoy them-
felves up when flying, by diftending their lungs

& with

COMPARATIVE ANATOMY.

5°

\vith air, and alfo ftraiten their trachea arteria, and
fo return the air.

Secondly, they fupply the place of a mufcular dia-
phragm and ftrong abdominal rm fries ; producing the
fame effects on the feveral contained vifcera , as thefe
mufcles would have done without the inconveniency
of their additional weight'; and conducing as much
to the exclufion of the egg and faeces.

The trachea arteria, near where it divides, is very
much contracted, and their voice is principally owing
to this coarftion. If you liften attentively to a cock
crowing, you will be fenfibk4 that the uoife does not
proceed from their throat, but deeper ; nay this very
pine, when taken out of their body and cut off a
little, after its divifion, and blown into, will make a
fqueaking noife, fomething like the voice of thefe
crearures. On each fide, a little higher than this
contraction, there is a mufcle ariling from their Jler-
vum , which dilates the trachea. 1 he cartilages , of
which the pipe is cornpofed in this animal, go quite
round it ; whereas in men and quadrupeds, they are
difeontinued for about one fourth on the back part,
and the intermediate fpace filled up by a membrane.
Neither is the trachea fo firmly attached ter their ver-
tebra as in other creatures we have examined. i his
Itrufture we fliall find of great fervice to them, if ve
confider, that had the fame ftruffure obtained in
them as in us, their breath would have been, in ha-
zard of being flopped at every flexion or twilling of
their neck, which they are frequently obliged to.
This we may be fertflble of by bending our necks
conflderably on one fide, upon which we fhall find a
great ftraitnefs and difficulty of breathing ; whereas
their trachea is better fitted for following the flexions
of the neck by its loofe connection to the vertebre:
and as from the ftrufture of the trachea it cannot
yield to every caufe diftending the afophagus as in us,
it was proper they fhould be placed at a greater
diftance from each other, which we accordingly find
they are.

In

COMPARATIVE ANATOMY. 5*

In place of a mufcular diaphragm, this creature^ has
nothing but a thin membrane connected to the pericar-
dium, which feparates the thorax and abdomen. But be-
fides this, the whole abdomen and thorax are divided
by a longitudinal membrane or mediajl inum connected,
to the lung %, pericardium, liver, ftoraach, and to the
fat lying over their (tomach and guts, which is analo-
gous to an omentum, and fupplies its place.

The kidneys lie in the hollow excavated in the fide
of the back-bone, from which there is fent out a
blueilh coloured canal, running along by the fide of
the vos deferens, and terminates directly into the
common cloaca. 1 his is the ureter , which opens by
a peculiar aperture of its own, and not at the penis .
This creature having no vefica urinaria, it was thought
by fome they never pafled any urine, but that it went
to the nourifiiment of the feathers, but this is falle ;
for that whitilh fubftance that you fee their greenilh.
faces covered with, and which turns afterwards
chalky, is their’ urine. Let us next confider the or-
gans of generation of both fexes, and firft thofe of
the male.

The tejlicles are fituated one on each fide of the
back-bone, and are proportionally very large to the
creature’s bulk. From thele run out the vafafemini •
fera, at firft (freight, but after they recede far-
ther from the body of the tefiicle, they acquire au
undulated or convoluted form, as the epididymis in
man. Thefe convolutions partly fupply the want of
veficul ee feminales, their coition being at the lame
time very lhort ; thefe terminate in the penis, of
which this creature has two, one on each tide of the
common cloaca, pointing d'reftly outwards, and are
very fmali and very lhort, hardly fo big as a millet
feed ; whence they have efcaped die notice of anato-
tniUs, who have often denied their exigence. This
is what is chiefly remarkable in the organs of the
male.

The racemus vitelLrum being analogous to the
ovaria in the human fuhjeft, are attached by a proper

F 2 membrane

52 COMPARATIVE ANATOMY.

membrane to the back -bone This is very fin? and

thin, and continued down to the uterus . Its orifice is
averfe with refpeft to the ovaria, yet notvvithftand-
ihg> by the force of the orgafmus venereus, it turns
found and grafps the vile! Ins, which in its paffage
through this duEt, called the infundibulum, receives
a thick gelatinous liquor, fecreted by certain glands.
T his, with what it receives in the uterus, compofe the
■white of the egg By this tube then it is carried
into the uterus .

J he uterus is a large bag, placed at the end of the
infundibulum, full of wrinkles on its infide ; here the
egg is completed, receiving its laft involve rum , and the
Ihell is at laft pufhed out at an opening in the fide of
the common cloaca. From the tejies in the male
being fo very large, in proportion to the body of the
creature, there mult necelTarily be a great quan-.
t'ity of femen fecerned; hence the animal is lalacious,
and becomes capable of impregnating fo many fe-
males. 1 heVant of the vefcula feminales is in fome
meafure fupplied by the convolutions of the vafa de.
ferentia , and by the fmall diftance betwixt the fecer-
niug and excretory organs. 1 he two penes contribute
alfo very much to their Ihort coition, at which time
the opening of the uterus into the cloaca is very much
dilated, that the effetft of the femen on the vitelli may
be the greater.

A hen will of herfelf indeed lay eggs, but thefe
are not impregnated, and yet appear entirely com-
plete, except that the fmall black ipor, which comes
afterwards to he the rudiments of the chick, is not
here to be ohferved/ After having obferved the
contents of th e abdomen and thorax, we next proceed
to examine the parts about the neck and head.

"1 hele creature ,as was oblerved.of fowls in general,-
have no teeth, which would have beenneedlefs, as they
Ta allow their food entire; but their tongue is made
pret-tv firm, left it Ihould be hurt by the (harp points
of the grain they feed on. It is of a triangular fi-
gure, and pointed before; and as by the depending

pollure

COMPARATIVE ANATOMY. 53
pofture their nteat it in

i K=SrJttrJW5«

nafiace to the food, but hindering its return.

P We have here no velum palatinum, uvula or ep -
,Z* and^n place of two large holes opening >mo
r rhpre is onlv a long narrow rima fupphed
^th p eny ftrong nicies, and fuch another rupees
The Place of a glottis. The creature has a power of
fl uttC both ft pleafure, and the nature of their
food feems not only to exempt them from the hazard
of its setting into the nofe or trachea, but its lharp
pointsgwouid hurt an uvula, or epiglottis, if they had
fnv Hence we fee with what difficulty they fal-
low dough or other fort of food that can be eafi.y

moulded into 3iiv ff'iio* -

J heir cranium is more cellular and cavernous ^than

ours • by this means their heads are light, yet ftrong
enough to refill external injuries ; for the enlar-
ging Hhe diameter of the bones contributes to their
Length. By this cavernous cranium the organ of
finelling is confide r ably enlarged-, and S'

ing birds, as is oblerved by Mr Ray and Mr Derham,
ha5ve this cavernous flruftnre of the brain fiill more
ebfervable ; and we are told that the cavity c*
the tympanum communicates with the cells ; but this
1 am apt to believe, fo far as I could find from dif-
feclion, is rather founded on theory than matter of
fa&. Their brain is covered with the common went*
braties, but its external furface is not formed into lo
many eyrce or convolutions, as ours, its antenot
part is quite lolid, of a cineritious colour, audio
far has a refemblarce of the corpora firtata, as to give
rife to the olfaBory nerves. The whole of it appears
to us as imperfect, and we can fcarce determine
whether there be any- thing analogous to a third or
fourth ventricle ; neither the corpus callofum, fornix,
nates, or tejtes, k c. can be obferved here; which
parts therefor^ cannot be imagined as abfolutely ne-
* F 3 cellar y/

54 COMPARATIVE ANATOMY.

ceflary for the funftions of life, fmce we find thefe
creatures perform them fuificiently well. We may
perhaps think thefe ferve a particular ufe in man, who
is a rational creature, but then quadrupeds enjoy
them in common with man. Thefe protuberances,
,T c’ rather to depend on the different difpo-

iinon of the feveral parts, being varioufly comietted
and meeting m different direttions in different places
than their being abfolutely neceffary for any partial-
and th*3 ufes that have been alhgned to clif-
ft rent parts of the brain by authors, feem to me to
have no foundation but in the author’s fancy. I
have already owned my ignorance cf the ufes of the
particular parts of the brain, fo fhall not pretend to
gne reafons for their being different in different an's
m.rls, bur all fern to agree in this, that the cerebrum
has always hollows and vacuities in it, but the cere -
helium none.

1 heir organ of fuelling is very large and well pro-
vided with nerves ; hence they have this filiation
very acute. Ravens and other birds of prey ojve a
hire proof of this by their being able to fr.d ouf their
prey though concealed from their fight, and at a ton-
liderable ddiance

'ihofe birds that grope for their food in the wa-
tors, mud, (sV. ha-e large nerves which run quite to.
the end of their hills, by which the. find out and oil-
tingui/h their food.

O i .

The anterior parr of their eyes (rnflead of having
the fclcntic coat continued, fo as to make near a
‘fphere as in us) turns all of a hidden flat ; fo that
here the frier otic makes but half a fphere ; and the
'corue. t riles up afterwards, being a portio a very
fmall and ’ditt net fphere ; fo that in th ft* creatures
there is a much greater difference be-twix the fclero-
tie and cornea than in us. Hence their eyes do not
jut out of their heads- as in man and qvadr. peds As
mod of thefe creatures are continually euq loyed in
hedges and thickets, therefore that their eyes might
be faired from thefe injuries-, as wdl as from top
much light when flying in die face of the tun, there is

a

COMPARATIVE ANATOMY- 55

a very elegant mcchanifm in their eyes, which is a
membrane riling from the internal canthus of the eye,
which at pleafure, like a curtain, can be made to co-
ver the whole eye, and this by means of a proper
mufcle that rifes from the fclerotic coat and palling
round the optic nerves runs through the mufculus oculi
attollens (by which however the optic verves are not
corn prefled) and palpebra to be inferted into the edge
of this membrane. Whenever this mufcle ceales to
aft, the membrane by its own elafticity again difcovers
the eye. 1 his covering is neither pellucid nor opaque,
both which would have been equally inconvenient,
but being fo me what tranfparent, allows as many rays
to enter as to make any objeft juft vifible, and is
fufficient to direft them in their progreflion. By
means of this membrane it is faid that the eagle is Caid
to look at the fun. Quadrupeds, as we mentioned
before, have a membrana niftitans ; but then it only
can cover that part of the eye which is never covered
by their eye lids.

Belides, all fowls have another particularity, whofe
ufe 1 think is not fo well under flood, and that is a
pretty long black triangular purfe riling from the
bottom of their eye juft at the entry of the optic
nerve, and ftretched out into their vitreous humour,
and one would imagine it gave fume threads to the
cry flal line. I his the French (who as far as 1 know,
were the firft who took notice of it in their difleftions
before the Royal Academy) give the name of bourfi
n .re to. 1 his mav pofliby ferve to lufiocate fotne of
the rays of light, that they may fee objects more dif.
tinftly without hurting their eyes. It has a connec-
tion with the vitreous, and leeins to be joined alfo to
the cry flail ine humour. If we fuppofe it to have a
power of contraftion, (which may be as well allowed
as that of the iris) it may fo alter the polluon of the
vitreous and cryflalline humours, that the rays frona
any body may not fall perpendicularly upon the crys-
talline, and this leems to be neceflary in them* fince
•they cannot change the figure of the anterior paj’t of
■iheir eye fo much as we can do j and as this animal

s 6 COMPARATIVE ANATOMY.

is expofed often to too great a number of rays of’
light, fo they having no tapcium, have the .bottom
of their eye wholly black on ii>f i\th: and in con-

fequence of this fowls fee verv ill in the dark.

They have no external ear, bur m place thereof a
tuft of very fine feathers coveriny the meatus audi-
torius, which eafily allow the rays of found to pafs
them, and likewife prevent duft. or any mfeft from
getting in. An external ear would have been incon-
venient in their palling through thickets and in fly.
ing, &c. A liquor is fepa rated in the external part
of the ear or meatus auditorius to lubricate the paf-
fage, and further prevent the entrance of any infers,
life i he mem bra na t\mpani'\b convex externally, and
no mnfcles are fixed to the bones of their ear, which
are rather of a cartilaginous confidence y any tre-
mulous motions impreffed on the air are communi-
cated in thefe creatures, merely by the fpring and e-
Falficity of thefe bones, fo probably the membrane is
not fo diftended as in the human ear, where this is
done by mulcles. The cochL a and femicircular canals
are very diltinct and eafily prepared.

The Anatomy of a carnivorous Fowl.

W'Ecome next to the birds of prey, and for an ex-
ample (hail take a flenhil. The principal dif-
ference to be ohftrved in them, is in their chylopoietie
vifeera, which may be accounted for from their dif-
ferent w'ay of life.

Immediately under their clavicles , you will obferve
the oefopkagus expanded into their inglnvtes, which
is proportionally lefs than in the granivorous kind,
fince their food does not Iweli fo much by maceration,
and for the fame reafon, there is a lefs quantity of a
rnenjlruum to be found here.

They have alio a ventriculus fucceniuriatus plenti-
fully ftored with glands, fituated immediately above
their fiomach, which we lee here is evidently mnn-

brathus)

COMPARATIVE AX ATOMY.

$ 7

branous, otherw ife rhan in the granivorous kind, and
this difference, which is almoft the only one we
/hall find betwixt the two different fpecies of fowds, is
eafily accounted for from the nature of their food,
which requires lefs attrition, hemp eafier of digeflion
than that of the other kind ; never rhetbfts it feems
requifite it fhould he lifonger than the human, to
compenfate the want of abdominal muicles, which
are here very thin.

The fame mechanifm obtains in this creature’s duo •
denum , that we have hitherto obferved. As being
a carnivorous animal its guts are proportionally fhort-’.
er than thofe of the granivorous kind, for the rea-
fon firft given, viz. its food being more liable to
corrupt, therefore not proper to be long detained
in the body, and for that reafon it has no intejlina
doeca , of which the other fpecies of fowls have a
pair. The difference in their wings, backs and
daws are obvious, and have been already in fome
meafure obferved.

There is a full defcription of the different parts
of the egg, with the changes that happen in the
time of incubation, in the fecond volume of the Ale*
dual Ejfays.

The Anatomy of Fi/bes.

AOueous animals are generally divided into fuch
as have lungs, and inch as want them. The
firft fpecies differ very inconfiderably from an ox or
any other quadruped , and are not eafily procured, fo
that all I have to fay on fillies, lhall be taken from
that lpecies, which is not provided with relpiratory
organs.

Of thefe we may firft obferve, that they have a
very ftrong thick cuticle compofed evidently of a
great number of fcales laid one on another like the
tiles of houles ; this among other arguments ferves
to prove the human epidermis to be of a lquamous

ftructure.

5$ COMPARATIVE ANATOMY.

ftrucfture. In the next place thefe creatures have
neither anterior nor pofterior extremities, as quadru-
peds and fowls : For their progrefiion is performed
in a different way from either of thefe fpecies of
animals ; for this purpofe they are provided with ma-
chines properly tonli. ting of a great number of elaftic
beams, connefted to one another by firm membranes ,
and with a tail of the fame texture ; their J pine is
very moveable towards the pofterior part, and the
ftrongeft mufiles of their bodies are inferted there.
Their tails are fo framed as to contradl to a narrow
fpace when drawn together to either fide, and to
expand again when drawn to a ftrcight line with
their bodies, fo by the afiiftance of this broad tail,
and the fins on their fides, they make their progref-
fiion much in the fame way as a boat with oars on its
Tides and rudder at its Item. 1 he perpendicular
fins fituated on the fuperior part of their body keep
them in i equilibrium , hindering the belly from turn-
ing uppermoft, vvhiih it would readily do, becaufe
of the air bag in the abdomen rendering their belly
fpecifically lighter than their back, but by the refif-
tance thefe hns meet with when inclined to either
fide, they are kept with their backs always upper-
moft. The beft account of this matter we have in
the treatife before mentioned, viz. Borelli dc Motts
Animalium , part I. chap. 23.

It may be next oblerved, that thefe creatures
have nothing that can be called a neck, feeing they
feek their food in an horiiontal way, and can move
their bodies- cither upwards or downwards as they
have occalion by the contra&ion or dilatation of
their air bag ; a long neck, as it would hinder their
progreflion, would be very diladvantageous in the
element they live in.

'The abdomen is covered on the inferior part with
a black-coloured thin membrane refembling our peri-
toneum. It is divided from the thorax by a thin mem*
brumous partition which has no mufcular appearance,.

fo

COMPARATIVE ANATOMY. ^

fo that we have now Teen two different forts of ani-
mals that have no mufcular diaphragm.

1 hefe creatures are not provided with teeth pro-
per for breaking their aliment into fmaller morfels,
as the food they ufe is generally final] filhes or other
animals that need no trituration in the mouth, but
fpontaneoufly corrupt and gradually diffolve into a
liquid chyle. Their teeth lerve to grafp their prey
and hinder the creatures they have once catched from
efcaping again For the fame purpofe the inrernal
cartilaginous bahs of the bronchi, and the two round
bodies fituated in the poflerior part of the jaws,
have a great number of tenter-hooks fixed into them
in fitch' a manner, as that any thing may eafily get
down, but is hindered to get backwards. J he wa-
ter that is neceffai ilv taken in along w ith their food in
too great quantities to be received into their jaws in
deglutition, piffes betwixt the interflices of the bron-
chi, and the flap thit covers them. 1 he compref-
lion of the water on the bronchi is of conliderable ule
to the creature, as we lhall explain by and by.

The orfphagus in thefe creatures is very Ihcrt,
and fcarceiy diltinguifhed from their llomach, feeing
their food lies almoit equally in both. i he llomach
is of an oblong figure. There are commonlv found
fmall filhes in the itomach of large ones, Hill retain-
ing their natural form, but when touched they melt
down into a jelly. From this and the great quanti-
ty of liquors poured into their ftomachs. we may con-
clude rhat digeltion is iolely brought about in them
by the diffolving power of a menjtruurn , and that
no trituration happens here

I he guts in thefe animals are very fhort, making
only three turns, the lalt of which ends in the com-
mon cloaca for the faces, urine and femen , fituated
about the middle of the inferior part of their
bodies. ' *

What I call pancreas, fome gave the name of in-
teftinula c.tca to ; it confiits of a very great number
ot fmall threads, like fo many little worms, which all

terminate

66

COMPARATIVE ANATOMY.

terminate at laff in two larger canals, that open inte
the firfl gur, and pour into it a vifcous liquor, much
about the place where the biliuryduBs enter. 1 heir
intejlines are connected to the back bone by a mem-
brane analogous to a mefentery. No la Beals have
been yet obferved, and it is probable their aliment
is taken in by the m/feraic veins.

Their liver is very large, of a whitifh colour,
and lies almofl in the left fide wholly, and contains
a great deal of fat.

The gall-bladder is fuuated a confidcrable w’ay
from the liver, and fends out a canal, the cyjlic dud
which joins with the hepatic juB jull at the entry in-
to the gut ; fome fibres are ltretched from the liver
to the gall bladder, but none that 1 know of have hi-
therto difcovered any cavity in thefe cords ; fo in
this animal it fhould feein impoflible that the bile can
be carried into the gall-bladder in the ordinary way,
and confequently mutt either be fecei ned on the fules
of that fac, or regurgitate into it from the canalis chole-
dochus.

The fpleen is placed near the back-bone, ar.d at a
place where it is fubjected to an alternate preffure
from the conftricbon and dilatation of the air-bag,
which is fuuated in the neighbourhood. Since in
all the different animals we have diflected, we find
the fpleen attached to (omewhat that may give it a
conquafTation, as in the human fnbjeft and quadru-
peds, it is contiguous to the diaphragm, in fowls it
is placed betwixt the back bone, the liver and flo-
mach, in fillies it lies on the facus arias, and fince
we find it fo well fen ed with blood -vefTels, and all
its blood returning into the liver, we mull not con-
clude the fpleen to be an inutile pondus , only to
ferve as a balance to the animal pro equilibria,
but particularly defigned for preparing the blood to

the liver. _

The only organs of generation in this animal are
two menltruous bags iituated in the abdomen uniting
near th e podex. Thefe in the male are filled with a

whitifh

COMPARATIVE ANATOMY. 61

whitifh firm fubdance called the milt , and in the fe «
male with an infinite number of little ova cludered
together, of a reddilh yellow colour called the roc.
Both thefe at fpawning time we find very much dis-
tended, whereas at another time the male organs
can (carce be didinguilbed from the female, nor is there
any proper inftrument in the male for throwing the feed
into the organs of the female as in ether creatures.

I fhali not take upon me to determine the way where-
by the female fperm is impregnated, but we find
that the fpawn of frogs confilts in the fmall fpecks
wrapt up in a whitilh glutinous liquor ; thefe fpecks
are the rudiments of the young frogs which are
nouriihed in that liquor, till they are able to go in
fearch of their food. In the fame w’ay the ova of
fiihes are thrown out and depofited in the fand, the
male being for the mod part ready to impregnate
them, and they are incubated by the heat of the
fun. It is curious enough to remark with what care
they feek for a proper place to depofite their ova,
by fwimming to the lhallow, W'here they can better
enjoy the fun’s rays, and fhun the large jaws of o-
ther fiihes. '1 he river fiihes again fpawn in fome
creek free from the hazard of the impetuous dream.
But whether this mixture be brought about in fiihes
by a Ample application of the genitals to each other,
or if both of them throw out their liquors at the
fame time in one place, and thus bring about the de-
filed mixture, is not ealy to determine ; the latter
1 think, feems mod probable. Thefe creatures are
fo fhy that we cannot poflibly get to obferve their
way of copulation, and are confequently but little ac-
quainted with their natural hidory.

After railing up the black peritoneum , there comes
in view an oblong white membranous bag, in which
there is nothing contained but air. i his is the
fwimming-bladder ; it lies clofe to the back- bone,
and has a pretty drong mulcular coat, whereby it can
contract itfelt. By contracting this bag, they can
jnake the mulcles fpecifically heavier than water,

G- and

COMPARATIVE ANATOMY.

and fo readily fall to the bottom ; whereas the mufcit -
lar fibres ceafing to aft, they become fpecifically light-
er than water, and fo fwim above According to
the different degrees of contraction and dilatation of
this bladder, they can keep higher or lower in the
water at pleafure. Hence flounders, foies, raia and
fuch other filhes as want this far, are found always
groveling at the bottom of the water : It is owing
to this that dead fillies (unlefs this membrane has been
previoufly broke) are found fwimm'ing a top, the
mufcular fibres then ceafmg to aft, and that with their
bellies uppermoft ; for the back-bone cannot yield,
and the diftended fac is protruded into the abdomen
and the back is cor.fe piently heavieft at its upper
part according to thar pollure. There is here
placed a glandular lubflance containing a good quan-
tity of red blood and all the red in their body is
contiguous to this air-bag, excepting the guts \ rom
the anterior part of the bag go out two procejfes or
appendices, which, according to the gentlemen of
the French Academy, terminate in their fauces :
but I never could find out this communication either
by tracing them, pouring in mercury or water, &A
I put, it is true, a prol e thr ugh them, but theft
with the fame ftrengtb I could have put it through
the (ides of the procefl'es , fo that I am afraid this it
gratis dictum, and that there is here as in Tome o*
ther places of the human bodv an ner injitus.

At the fuperior part of this bag there are other
red coloured bodies, of a glandular nature, which are
connefted with- the kidneys. From them the ureters
go down to their inflrtion in the vefica immune*,
which lies in the lower part- of the abdomen, and the
urethra is there produced, which, terminates in the
pedex.

Thefe lafl mentioned parrs have not hitherto been

obferved in fome fpecies of fifties, whence authors too

bailily denied them in all. Thefe creatures have a
membranous diaphragm which forms a faci hi w 1

COMPARATIVE ANATOMY. 63

the heart is contained. It is very tenfe, and almoft
perpendicular to the vertebra. ... , r

The heart is of a triangular form, with its bale
downwards, and its apex uppermoft, which fituation
it has becaufe of the branch la. It has but one

auricle and on e. ventricle , becaufe they want lungs; .
and one great artery. 1 he fize of the auricle and
ventricle are much the fame ; the artery fends out
numberlefs branches to the branchia or gills.

The branchia lie in two large flits at each Ode of
their heads, and feem to be all they have that bears
any analogy to lungs. I heir form is lemicircular ;
they have a vaft number of red fibrilla handing out oil
each fide of them, like a fringe, and very much re-
feinble the vane of a feather. Thefe branchia are
perpetually fubjeded to an alternate motion and pref-
fure from the water ; and we may here remark, that
we have not found any red blood but in places fubjected
to this alternate preflure ; this obfervation will help
us in explaining the action of the lungs upon the
blood. Over thefe gills there is a large flap, allow-
ing a communication externally, by which the water
they are obliged to take into their mouths with their
food, finds an exit without palling into their ftomach;
it is owing to thefe flaps coming fo far down that the
heart is faid commonly to be fltuated in their heads.

Their brains are formed pretty much in the fame
way as that of fowls, only we may obferve that the
pofterior lobes bear a greater proportion to the an*
terior.

Their organ of fmelling is large, and they have a
power of contracting and dilating the entry into their
nofe as they have occaflon. It feems to be mofily
by their acute fmell that they difcover their food ;
for their tongue feems not to have been defigned for
a very nice lenfation, being of a pretty firm cartila-
ginous fubftance, and common experiment evinces
that their fight is not of fo much ufe to them as their
fmell in learching for their nourilhment. If you

G 2 throw

'6* COMPARATIVE anatomy.

throw a freflj worm into the water, a fifh fhal! di-
ftinguifh it at a confiderable diftance, and that this is
not done by the eye, is plain from obferving,
that after the fame worm has been a confiderable
time in the water and loft its fmell, no fifties will
come near it ; but if you rake out the bait and make
fever a 1 little incifions into it, fo as to let ont more of
the odoriferous effluvia, it ftiall have the fame effedi
as formerly. Now it is certain, had the creatures
difcovered this bait with their eyes, they would have
come equally to it in both cafes : In confequencfe of
their fmell being the principal means they have of
difcovering their food, we may frequently obferve
their allowing themfelves to be carried down with
the dream, that they may afcend again leifurely againft
the current of the water ; thus the odorous particles
fy,'imming in that medium being applied more for-
cibly to their fmelling organs, produce a ftronger
ftnfation.

The optic nerves in thefe animals are not confound-
ed with one another in their middle progrefs be-
twixt their origin and the orbit, but the one pafies
over the other without any communication,' fo that
the nerve that comes from the left fide of the brain
goes di£tin<ftly to the right- eye.! And vice verfa.

The lens cryflallina is here a compleat fphere,
whereas in men and all other rerreftrial animals it
confifts of two portions of unequal fpheres laid on
one another ; to account for t his j it mud be confi-
dered that thefe creatures have got no aqueous hu-
mour, as the rays that come to their eyes are con-
veyed through a medium of the fame denfity with
that humour in other animals, and confequently
wonld have gone on in a {freight line, without any
refradtion till they come to the lens, although they
had been provided with an aqueous humour ; thus
then the rays impinging upon their lens have hither-
to fufFered no refraction ; that they might therefore
be fufficiently refradted and meet in a point on the
rhma3 it was neceflary the lens lhould be made more

convex

COMPARATIVE ANATOMY. 65

convex than it is in other creatures who have the
rays confiderably refraSed in their paffage from the
air through the aqueous humour. .... .

As filhes are continually expofed to injuries in the
uncertain element they live in, and as they are in per-
petual danger of becoming a prey to the larger ones,
it was neceffary their eyes fhould never be tout, and
in confequence of this they are not provided with
palpebra ; but then as in the current ltfelf the eye
mud be expofed to feveral injuries, there was a ne-
ceflity it Ihould be fufficiently defended, which in ef-
fect it is by a firm pellucid membrane that feems to be
a continuation of the cuticula , being (tretched over
here. The epidermis is very proper for this purpole,
as being infenfible and deftitute of vefTels, and
confequently not liable to obftruftions, or by that
means, of becoming opake.

Whether fifties have a fenfe of hearing or not, is
very uncertain : All that has the appearance of an
organ of hearing in thefe creatures is a bone, about
the bulk of one half of a common bean of a particu-
lar ftrufture, being very brittle and compofed of a
great many different Jegments laid at one another*
fides, and fituated in a particular form at the fide of
the brain ; is then the idea of found communicated
to them by means of this bone ? Or does their run-
ning away, at ftamping hard on the ground or cry-
ing loud, depend, upon fome other kind of fenfation?
This may poffibly be produced in them, by a tremu-
lous motion communicated to their bodies by the cir-
cumambient water, which is pur in agitation, from
the like concuflions happening in the air or neighbour-
ing ground.

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