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BR 515 .L6 1836
Paley, William,

Paley's Natural

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1743-1805

theology

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PALEY'S

NATURAL THEOLOGY,

WITH

ILLUSTRATIVE NOTES,

BY

HENRY LORD BROUGHAM, F.R.S.

AND MEMBER OF THE NATIONAL INSTITUTE OF FRANCE,

AND

SIR CHARLES BELL, K.G.H., F.R.S., L. & E.

PROFESSOR OF SURGERY IN THK UNIVERSITY OF EDINBURGH, FOR-
MERLY OF THE COUNCIL, AND PROF. ANAT. ROY. COLL.
SURG. LONDON, ETC.

TO WHICH ARE ADDED

SUPPLEMENTARY DISSERTATIONS,

By sir CHARLES BELL.
WITH NUMEROUS WOOD-CUTS.

TWO VOLS. VOL. L

LONDON:

CHARLES KNIGHT.

NEW-YORK: WILLIAM JACKSON.

MDCCCXXXVI.

G. F. HOPKINS Jc SON, Printers.

ADVERTISEMENT.

It is apparent that considerable difficulty must
attend the task of illustrating the justly cele-
brated work of Dr. Paley. According to his
design, no one subject could be fully and finally
treated : the eye, the ear, the teeth, and many
other organs, are of necessity touched upon oc-
casionally and repeatedly in different chapters,
at one time to prove prospective contrivances,
at another to show compensation, or relation.
This is undoubtedly a plan suited to the object
of the author ; and time and the opinion of the
public pronounced on the work have amply con-
firmed his judgement in adopting it. Fearful of
introducing too many additional subjects in the
notes to the text, and thus overloading the ar-
gument, we have thrown the Dissertations, in
illustration of the various matters, into an Ap-
pendix : thus leaving the reader more at liberty
to select the subjects on which he desires further
information.

IV ADVERTISEMENT.

Mr. Paxton, of Oxford, several years ago, pub-
lished a valuable work illustrating the " Natural
Theology,^' to which the reader is referred for fur-
ther illustration on some of the subjects, particu-
larly those connected with anatomy.

The authors of the present work have been in-
debted to Professor Lindley, of the London Uni-
versity, for the botanical notes to the twentieth
chapter ; and to Mr. Waterhouse, Curator of the
Zoological Museum of London, for the entomolo-
gical notes to the nineteenth chapter ; those which
were kindly communicated by Bishop Brinkley
are specified in chapters twenty-two and twenty-
five.

The Dissertations connected with the last ten
chapters will form a fourth volume, which will
complete this work.

The whole of the Notes, and nearly the whole
of the Dissertation, now published, to the first
seventeen chapters, were prepared for the press
several months ago, and the greater part of them
printed last summer. But the expediency of
making some additions to the Dissertations has
occasioned the publicatian to be delayed.

CONTENTS OF VOL. I.

CHAPTER I.

STATE OF THE ARGUMENT.

Watch, page 2 ; eight cases, 4-8.

yote 1, Referring to the Appendix for a description of the me-
chanism of the watch, page 1 ; 2, on *' how the stone came
to be there," ib. ; 3, on the turning of oval frames, 4 ; 4, on
"laws" of nature, &c., 8.

CHAPTER II.

STATE OF THE ARGUMENT CONTINUED.

J^ote 5, on the management and tendency of the argument in
Chapter II., 17.

CHAPTER III.

APPLICATION OF THE ARGUMENT.

Eye and telescope, 19 ; light — distance, 26; eyes of birds, 31 ;
eyes of fish, 32 ; minuteness of picture, 35 ; socket — eye-
brow — eye-lid — tears, 36 ; nictitating membrane — mus-
cle, 38 ; expedients, 41 ; why means used, ib. ; ear, 44.

J^ote 6, referring to Appendix, 18 ; 7, referring to Appendix, and
on the adaptation of the eyes offish to the medium in which
they live, 20 ; 8, referring to Appendix, and on refraction,
23 ; 9, on the adjustment of the eye to different distances,

VI CONTENTS.

29; 10, on the pressure of the sea at great depths, and on
the structure of the eyes of fishes in order to resist that
pressure, 33 ; 11, referring to the Appendix for observations
on the structure of the eyes of fishes, 37 j 12, on the mem -
branaiiictitans, 40 ; 13, referring to Appendix for observa-
tions on the limits which the Deity seems to have prescrib-
ed to his own power, 42 ; 14, referring to the Appendix,
and on the structure of the ear, 44; 15, on the chain of
bones in the ear, 49.

CHAPTER IV.

OF THE SUCCESSION OF PLANTS AND ANIMALS.

No account hereby of contrivance, 54 ; plants, 55 ; oviparous
animals, ib. ; viviparous — rational animals, 57; instance
from Gardener, ib.

J^Tote 16, on the limits of the term of existence, and on repro-
duction, 59.

CHAPTER V.

APPLICATION OF THE ARGUMENT CONTINUED.

Repetition from Chapter I., 61; imperfection, ib.; superfluous
parts, 63 ; atheistic argument, 65 ; remains of possible forms,
69 ; use arising out of the parts, 73 ; a principle of order,
76 ; of our ignorance, 78.

JN'ote 17, on the suspension of respiration, 63; 18, on parts of
animals said to be superfluous, 65 ; 19, on results supposed
to arise from chance, 68 ; 20, on the supposition of animals
having been produced by chance, 71 ; 21, on the dexterity
which man acquires by practice as distinguishing him from
other animals, 82.

CHAPTER VI.

THE ARGUMENT CUMULATIVE.

CONTENTS. VU

CHAPTER VII.

THE MECHANICAL AND IMMECHANICAL PARTS AND FUNCTIONS OF
ANIMALS AND VEGETABLES.

Imperfection of knowledge no proof of want of contrivance, 84 ;

on chemistry, 89; secretion, 91.
J^ole 22, on the perfection of the immechanical parts of animals,
84 ; 23, on the gastric juice as not acting upon the stomach
of the hving animal, 91.

CHAPTER VIIL

MECHANICAL ARRANGEMEMT IN THE HUMAN FRAME.

Of bones, 99; neck, ib. ; fore-arm, 102; spine, 104; chest, 114;
knee-pan, 115 ; shoulder-blade, 116 ; joints, 118 ; ball and
socket, 119; gynglymus, 121; knee, ib.; ankle, 122;
shoulder, 123; passage of blood-vessels, 124; gristle, 125;
moveable cartilages, 127; synovia, 128; how well the
joints wear, 129; immoveable joints, 130.

J^oie 24, on the meaning of the terms tenon and mortice, 100;
26, on variations of structure to suit the peculiar condition
or necessities of different animals, 112; 27, referring to
Appendix for further proofs of adaptation of structure to
habits and condition of animals, 115; 28, on the shoulder-
blade and collar-bone, 117; 29, on the absence, in the ouran-
outang, of the ligament in the head of the thigh-bone ; 121 ;
30, on the ankle-joint, 122 ; 31, on the cartilage which
covers the ends of the bones, 126 ; 32, on the manner in
which the thigh-bone rests upon the shin-bone, and the use
of the cartilage between them, 128 ; 33, on absorption, in
a case of inflammation of a joint, 130.

CHAPTER IX.

OF THE MUSCLES.

Suitableness to the joints, 132; antagonist muscles, 134; not ol>-
structing one another, 136 ; action wanted where their

VUl CONTENTS.

situation would be inconvenient, 137 ; variety of figure, 138 ;
how many things must be right for health, 140 ; variety,
quickness, and precision of muscular motion, 141 ; tongue,
ib.; mouth, 143 ; nose, 145 ; music — writing, 146; sploinc-
ters, 147; combination of muscles, 148; delicacy of small
muscles, 149; mechanical disadvantages, i6. ; single mus-
cles, 151; lower jaw, i6. ; slit tendons, 152 ; bandage at
the ankles, 153 ; hypothesis from appetency repelled, 154 ;
Keill's enumeration of muscles, ib. ; why mechanism is not
more striking, 155; description inferior to inspection, i6.;
quotation from Steno, 156.

J^ote 34, on the balance of action between the antagonist muscles,
134; 35, on the sacrifice of power in certain muscles, in
order to require velocity, 139 ; 36, on the complexity of
structure in the tongue, 146.

CHAPTER X.

OF THE VESSELS OF ANIMAL BODIES.

i. The circulation of the blood, 158; disposition of the blood-
vessels, 159 ; arteries and veins, 160 ; ii. hearl, as receiving
and returning the blood, 162 ; heart, as referable to the
lungs, 164; valves of the heart, 170 ; vital motions involun-
tary, 175 ; pericardium, 176; iii. alimentary system, 177 ;
passage of the food through the stomach to the intestines,
178; passage of the chyle through the lacteals and tho-
racic duct to the blood, 179; length of intestines, 180;
peristaltic motion, ih. ; tenutity of the lacteals, 181 ; valves
of the thoracic duct, ih.; entrance at the neck, 182; diges-
tion, ib. ; iv. gall-bladder, 185; oblique insertion of the
bihary duct into the intestines, 187 ; v. parotid gland, ib.;
vi. larynx, J88; trachea — gullet— epiglottis, 189, 190;
rings of the trachea, 191 sensibihty, ib. ; musical instru-
ment, 192; lifting the hand to the head, 195.

JsToU 37, referring the Appendix for a dissertation on the circu-

CONTENTS. IX

lation of the blood and its uses, 159 ; 38, on the composition
of the atmosphere, 164; 39, on the necessity of exposing
the venious blood to the air, 165; 40, on the valves of the
veins and arteries, 173 ; 41, on the germination of seeds
which have passed unbroken through the stomachs of ani-
mals, 184 , 42, referring to Appendix on the stomach of the
horse, 186 ; 43, on the necessity of certain sensibilities in
the body, 191 ; 44, referring to Appendix for observations
on the lungs, 193.

CHAPTER XL

OF THE ANIMAL STRUCTURE REeARDED AS A MASS.

i. Correspondence of sides, 196 ; not belonging to the separate
limbs, 198; nor to the internal contents, 199 ; nor to the
feeding vessels, ib. ; ii. package, 200; heart, 201 ; lungs,
202 ; liver, 203 ; bladder, ib. ; kidneys, ib. ; pancreas, ib ;
spleen, 204 ; omentum, ib. ; septa of the brain, ib. ; guts,
205 ; iii. beauty, 207 ; in animals, 208 ; in flowers, ib. ;
whether any natural sense of beauty, 209 ; iv. conceal-
ment, 211 ; V. standing, 212; vi. interrupted analogies,
216 ; periosteum at the teeth, ib. ; early skin at the nails,
217; soft integuments at the skull, 218;

JVote 45, on the spleen, 204; 46, on the sensibility by which we

are enabled to balance the body, 214 ; 47, referring to the

Appendix for a dissertation on the teeth, 217 ; 48, on the

use of the nails of the fingers, 218; 49, referring to the

-Appendix for a note on the form of the skull, ib.

CHAPTER XII.

COMPARATIVE ANATOMY.

i. Covering of animals, 222; of man, ib ; of birds, 223; struc-
ture of feathers, ib. ; black down, 228 ; ii. mouths of
animals, 229; bills of birds, 231; serrated bills, 233;
affinity of mouths,. 236; iii. gullets of animals, ib; iv.

X CONTENTS.

intestines of animals, 237 ; valves or plates, ib. -, lengtli,
238 ; V. bones of animals, 239 ; bones of birds, ib. ; vi,
lungs of animals, 240 ; lungs of birds, ib.] vii. birds ovipa-
rous, ib.] viii. instruments of motion, 241 ; wings of birds,
ib. ] fins of fish, 243 ; web-feet of water-fowl, 247 } ix.
senses of animals, 248.

J^Tote 50, on the coverings of birds and other animals with refer-
ence to warmth, 228 5 51, on the adaptation of the bills of
birds to the habits of each kind, 232; 52, on the connexion
of the fifth nerve of the brain with the organ of touch, 235 ;
53, referring to the Appendix for observations on the rela-
tion of the bodies of birds to the atmosphere, 240 ; 54, on
the necessity of birds being oviparous in order to retain the
power of flying, 241 ; 55, on the similarity of the system of
bones in all vertebrated animals, 243 ; 56, on the uses and
muscular power of the fins of fishes, 246.

CHAPTER XIII.

PECULIAR ORGANIZATIONS.

Pax- wax of quadrupeds, 252 ; oil of birds, 254; air-bladder of
fish, z6. ; fang of viper, 257 ; bag of opossum, 258; claw
of heron, 259; stomach of camel, 260; tongue of wood-
pecker, 261 J babyroussa, 265.

JVote 57, on the ligaments of the neck, 253 ; 58, on the air-bladder
of fishes, 256 ; 59, on the habits and tongue of the wood-
pecker, 262 ; 60, on the erroneous notion of the babyroussa
sleeping standing, 266.

CHAPTER XIV.

PROSPECTIVE CONTRIVANCES.

Teeth, 267; milk, 270; eye of the foetus, 272; lungs of the
foetus — foramen ovale, &c., 275.

CONTENTS. XI

Note 61, referring to Appendix for note upon the teeth, 261; 62,
on the means by which the second set of teeth are made to
succeed the first, 269 ; 63, on the provision for the first
nourishment of plants and animals, 271 ; 63, on the gra-
dual developenient of animal bodies, 275.

CHAPTER XV.

RELATIONS.

Alimentary system, 276; kidneys, ureters, and bladder, 281 ;
eyes, hands, feet, 282 ; sexes, ib. ; teats and mouths, 283 ;
particular relations, %b. ; swan, 284 ; mole, 286.

CHAPTER XVI.

COMPENSATION.

Elephant's proboscis, 268 ; hook in the bat's wing, 290 ; crane's
neck, 291 ; parrot's bill, ih', spider's web, 292; multiplying-
eyes of insects, 294 ; eyelid of the chameleon, 295 ; intes-
tines of the alopecias, 296 ; snail — muscle — cockle — lob-
ster, 297; sloth — sheep, 299; more general compensa-
tions, 300 ;. want of fore-teeth — rumination, ib. ; in birds,
want of teeth and gizzard, 302: reptiles, 304.

J^ote 64, on tlie unreasonableness of the notion of a change in the
original structure of animal organs, 289 ; 65, interesting
particulars concerning the powers and habits of the spiders,
292; 66-67, referring to Appendix, 298, 300; 68, on the
' digestive organs, with reference to the different kinds of
food, 301 ; 69, on the relation between the mouths and
stomachs of animals, 303; 70, on the variety of the instru-
ments of motion of different animals, 305.

CHAPTER XVII.

THE RELATION OP ANIMATED BODIES TO INANIMATE NATURE.

Wings of birds — fins offish — air and water, 307 ; ear to the air,

XU CONTENTS.

ib. ; organs of speech — voice and respiration to air, 308 ;
eye to light, ib. ; size of animals to external things, 309 ; of
the inhabitants of the earth and sea to their elements, 310 ;
sleep to night, 312.

JVote 71, referring to the Appendix for observations on the bones
of large animals, 309 ; 72, on the succession of day and
night and on the changes of the seasons, with reference to
the happiness of animals, 313.

CHAPTER XVIII.

INSTINCTS.

Incubation of eggs, 316 ; deposition of eggs of insects, 322 ; solu-
tion from sensations considered, 327.

J^Tote 73, on the unchangeableness of animal instincts, 317; 74,
on the instincts of the chicken in breaking the shell of its
egg, 319; 75, on the natural and instinctive feeUngs of
man, 327 ; 76, on the arguments of skeptics, and on com-
pensations in animal organs and powers, 331.

CHAPTER XIX.

OF INSECTS.

Elytra of the scarabseus, 337 ; borer of flies, 339 ; sting, 341 ;
proboscis, 343 ; metamorphosis of insects, 346 ; care of
eggs, 349 ; observations limited to particular species, 350 ;
thread of silk-worm and spider, ib. -, wax and honey of bee,
352 ; sting of bee, 355 ; forceps of the panorpa tribe, ib. ;
brushes of flies, ib.; glow-worm, 356 ; motion of the larva
of the dragon-fly, 357 ; gossamer spider, 358; shell animals,
359; snail shells, 360; univalve shell-fish, 361; bivalve,
363 ; lobster shell, ib. ; variety of insects, 364.

J^ote 77, on the antennae of insects, 336 ; 78, on the word
coleoptera, 338 ; 79, on the wing-cases of brachelytra, ib. ;
80, on the wing-cases of the genera molorchus, ib.; 81, on

CONTENTS. Xlll

tlie genus Hisler, 339 ; 82, on parasitical insects, 340 ; 83,
on the ovipositors of insects, ib.; 84, whimble of insects an
ovipositor, 341 ; 85, stings of insects used as ovipositors, ib.;

86, anatomical description of the proboscis of the bee, 343;

87, on the indentation in the head to receive the proboscis,
344; 88, on the parts of the mouths of insects, ib.; 89,
referring to note ib.; 90, on the habits of bees in collecting
food, &.C., 345 ; 91, description of the parts of the mouth of
the common flea, 346 ; 92, on the structure of the mouths
of caterpillars, ib.; 93, on the difference between the larva
and the perfect insect, 348 ; 94, on bees' wax, 353 ; 95, on
the construction of the cells of bees, 354; 96, on the ^enus
Trichins, 355 ; 97, on the mode in which the stag-beetle
cleans its antennas, ib.; 98, on the glow-worm, 356 ; 99, on
the glow-worm's Ught, 357; 100, on the manner in which
the spider attaches its thread to different bodies, 359 ; 101,
on the number of the species of insects, 364 ; 102, number of
the species of butterfly in this country, 365 ; 103, on insects
subsisting on carrion, 367; 104, on the similarity between
the improvements in paper-making and the construction of
ivasp-paper ; and on the migration of birds, ib.

CHAPTER XX.

OF PLANTS.

Preservation, perfecting, and dispersing of seed, 369; germina-
tion, 378; tendrils, 381; particular species, 384; vaUis-
neria, t6.; Cuscuta Europaea, 385; misseltoe, 386; colchi-
cum autumnalc, 387; dionsea muscipula, 389.

J^Tote 105, on the structure of birds, 372 ; 106, correction of the
text, 383; 107, on the Cuscuta Europcea, 385 ; 108, on para-
sitical plants, 387 ; 109, no attracting syrup on the leaves
of the dionaea, 390; 1 10 description of the pitcher-plant, ih.

ILLUSTRATIVE WOOD-CUTS. — VOL I.

1. The form of the eye, 19.

2. Section of the anterior part of the human eye, to show the

manner in which the images of objects are impressed upon
the retina, 25.

3. The iris separated from the eye, and laid out flat, 26.

4. Head of the eel, showing the form of the eye, 33.

5. Plan of the h-aman ear, 45.

6. Bones of the ear, 47.

7. Bones of the ear separated, 47.

8. Drum of the ear, 50.

9. The eye^ showing the transmission of the images of objects ,

81.
10. A muscle, 85.
11 The lower surface, or base, of the skull, 98.

12. Uppermost vertebra, or atlas, 100.

13. Articulation of the first and second vertebras of the neck, 101.

14. Section of the three lower vertebrae, 103.

15. Three views of the knee-joints, 105.

16. Muscle with tendons on different sides, 116.

17. Figure showing how velocity is acquired by pulling obliquely,

139.

18. Figure of the arm, showing the action of the biceps muscle,

149.

19. The heart and great blood-vessels, 157.

20. The two sides of the heart separated. 167.

21. Section of the ventricle and the artery, 169,

22. Valve of the great artery, 174.

23. Bones of the human foot, 214.

24. Heads of birds, showing the form of the bills, 230.

25. Head and neck of the heron, 232.

ILLUSTRATIVE WOOD-CUTS. XV

26. Head of the spoon-bill, 233.

27. Feet of birds, with and without web, 248.

28. Heads of the wolf and hare, showing the different manner in

which the ears are turned, 249.

29. Iris of the lion's eye, 250.

30. Dissected head of the woodpecker, 264.

31. Skull of the babyroussa, 265.

32. Spider suspended from a twig, 293.

33. Ovipositors of insects, 339.

34. Proboscis of the bee dissected, 343.

35. Mouths of beetle and bees dissected, 347.

36. Silkworm, 351.

37. Garden snail, 359.

38. Prickly oyster, 361.

39. Cock's-comb oyster, 362.

40. Venus' heart cockle, ib.

41. Poppy, 371.

42. Cuscuta Europsea, 385.

43. Autumnal crocus, 387.

44. Pitcher-plant, 390.

i. TESOLOGI

NATURAL TllfilO:l;iOv^|S^

CHAPTER I.

STATE OF THE ARGUMENT.*

I\ crossing a heath, suppose I pitched my foot
against a stone, and were asked how the stone came
to be there, I might possibly answer, that, for any-
thing I knew to the contrary, it had lain there for
ever; nor would it, perhaps, be very easy to show
the absurdity of this answer.f But suppose I had

* The last note of the Appendix describes the mechaniem of a
watch, and iUustrates the elementary principles of mechanics.
Contrasted with the mere mechanism, there is another essay on
the mechanism of the animal body. These may be perused either
before or after reading the present chapter.

t The argument is here put very naturally. But a considerable
change has taken place of late years in the knowledge attained
even by common readers, and there are few who would be with-
out reflection " how the stone came to be there." The changes
which the earth's surface has undergone, and the preparation for
its present condition, have become a subject of high interest; and
there is hardly any one who now would, for an instant, believe
that the stone was formed where it lay. On lifting it, he would
find it rounded like gravel in a river : he would see that its aspe-
rities had been worn off, by being rolled from a distance in water :
he would perhaps break it, look to its fracture, and survey the

1

Z NATURAL THEOLOGY,

found a watch upon the ground, and it should he
inquired how the watch happened to be in that
place, I should hardly think of the answer which
I had before given — that, for anything I knew,
the watch might have always been there. Yet
why should not this answer serve for the watch as
well as for the stone ? why is it not as admissible
in the second case as in the first? For this reason,
and for no other, viz., that, when we come to inspect
the watch, we perceive (what we could not discover
in the stone) that its several parts are framed and
put together for a purpose, e. g. that they are so
formed and adju&ted as to produce motion, and
that motion so regulated as to point out the hour
of the day; that, if the different parts had been

surrciinding height?, to discover v.lience it had been broken ofT^
or trom what remote region it had been swept hither : he would
consider the place Avhere he stood, in reference to the level of the
sea or the waters ; and, revolving all these things in his mind, he
would be impressed with the conviction, that the surface of the
earth had undergone some vast revolution.

Such natural reflections lead an intelligent person to seek for
infonnation in the many beautiful and interesting works on geol-
ogy that have been published in our country of late years. And
by these he will be led to infer, that the fair scene before him, so
happily adapted for the abode of man, was a condition of the earth
resulting from many successive revolutions taking place at periods
incalculably remote ; and that the variety of mountain and valley,
forest and fertile plain, promontory and shalloAv estuary, formed a
world suited to his capacities and'enterprise.

So true is the observation of Sir J. Herschcl, " that the situation
of a pebble may afford him evidence of the state of the globe he
inhabits myriads of ages ago, before his species became its deni-
zens."

NATURAL THEOLOGY. *S

^differently shaped from what they are, of a differ-
ent size from what they are, or placed after any
other manner, or in any other order than that in
which they are placed., either no motion at all
would have been carried on in the machine, or
none which would have answered the use that is
now served by it. To reckon up a few of the plain-
est of these parts, and of their offices, all tending
to one result: — We see a cylindrical box contain-
ing a coiled elastic spring, which, by its endeavour
to relax itself, turns round the box. We next ob-
serve a flexible chain (artificially wrought for the
sake of flexure) communicating the action of the
spring from the box to the fusee. We then find
a series of wheels, the teeth of which catch in, and
apply to, each other, conducting the motion from
the fusee to the balance, and from the balance to
the pointer, and, at the same time, by the size and
shape of those wheels, so regulating that motion
as to terminate in causing an index, by an equable
and measured progression, to pass over a given
space in a given time. We take notice that the
wheels are made of brass, in order to keep them
from rust ; the springs of steel, no other metal being
so elastic ; that over the face of the w^atch there
is placed a glass, a material employed in no other
part of the work, but in the room of which, if there
had been any other than a transparent substance,
the hour could not be seen without opening the
case. This mechanism being observed, (it requires
indeed an examination of the instrument, and per-

4 NATURAL THEOLOGY.

haps some previous knowledge of the subject, to
perceive and understand it ; but being once, as we
have said, observed and understood,) the inference,
we think, is inevitable, that the watch must have
had a maker: that there must have existed, at some
time, and at some place or other, an artificer or
artificers who formed it for the purpose which w^e
find it actually to answer ; who comprehended its
construction, and desis^ned its use.

I. Nor would it, I apprehend, weaken the con-
clusion, that we had never seen a watch made ;
that w^e had never known an artist capable of
making one ; that we were altogether incapable of
executing such a piece of w^orkmanship ourselves,
or of understanding in what manner it was per-
formed ; all this being no more than what is true
of some exquisite remains of ancient art, of some
lost arts, and, to the generality of mankind, of the
more curious productions of modern manufacture.
Does one man in a million know how oval frames
are turned?* Ignorance of this kind exalts our

+ It is certainly a thing not easily expressed in words. The
nave of a circular wheel moves on a single pivot ; but there are
here two pivots, and grooves in the wheel to correspond with
them. These two grooves cross each other, and play upon the
pivots in such a manner that the centre of motion varies, and the
rim of the wheel moves in an ellipsis. It is exactly on the same
principle that we draw an oval figure, by driving two nails into a
board, and throwing a band round them, and then running the
pencil round within the band. These two nails are in the points
called by mathematicians the foci of the oval or ellipse ; and ac-
cordingly, a fundamental property of the curve is, that the sum of

NATURAL THEOLOGY.

opinion of the unseen and unknown artist's skill,
if he be unseen and unknown, but raises no doubt
in our minds of the existence and agency of such
an artist, at some former time, and in some place
or other. Nor can I perceive that it varies at all
the inference, whether the question arise concern-
ing a human agent, or concerning an agent of a
different species, or an agent possessing, in some
respect, a different nature.

II. Neither, secondly, would it invalidate our
conclusion, that the watch sometimes went wrong,
or that it seldom went exactly right. The pur-
pose of the machinery, the design, and the de-
signer, might be evident, and, in the case sup-
posed, would be evident, in whatever way we ac-
counted for the irregularity of the movement, or
whether we could account for it or not. It is^not
necessary that a machine be perfect, in order to
show with what design it was made : still less ne-
cessary, where the only question is, whether it
were made with any design at all.

III. Nor, thirdly, would it bring any uncertainty
into the argument, if there were a few parts of the
watch, concerning which we could not discover, or
had not yet discovered, in what manner they con-
duced to the general effect ; or even some parts,

any two lines whatever, drawn from the two foci to any point in
the curve, is always the same. These points are called /od,^re5,
because lio;ht reflected from the surface of an oval mirror is con-
cfentrated there and produces heat.

1*

b NATURAL THEOLOGY.

concerning which we could not ascertain w hether
they conduced to that effect in any manner what-
ever. For, as to the first branch of the case, if by
the loss, or disorder, or decay of the parts in ques-
tion, the movement of the watch were found in fact
to be stopped, or disturbed, or retarded, no doubt
would remain in our minds as to the utility or in-
tention of these parts, although we should be un-
able to investiorate the manner accordinsr to which,
or the connexion by which, the ultimate eftect de-
pended upon their action or assistance; and the
more complex is the machine, the more hkely is
this obscurity to arise. Then, as to the second
thing supposed, namely, that there were parts which
might be spared without prejudice to the move-
ment of the watch, and that he had proved this by
experiment, these superfluous parts, even if we
were completely assured that they were such,
w^ould not vacate the reasoning which we had in-
stituted concerning other parts. The indication
of contrivance rem.ained, with respect to them,
nearly as it was before.

IV. Nor, fourthly, would any man in his senses
think the existence of the watch, with its various
machinery, accounted for, by being told that it was
one out of possible combinations of material forms :
that whatever he had found in the place where he
found the watch, must have contained some in-
ternal configuration or other ; and that this con-
figuration might be the structure now exhibited.

NATURAL THEOLOGY. 7

viz., of the works of a watch, as well as a differ-
ent structure.

V. Nor, fifthly, would it yield his inquiry more
satisfaction, to be answered, that there existed in
things a principle of order, which had disposed the
parts of the watch into their present form and sit-
uation. He never knew a watch made by the prin-
ciple of order ; nor can he even form to himself
an idea of what is meant by a principle of order,
distinct from the intelligence of the watchmaker.

VI. Sixthly, he would be surprised to hear that
the mechanism of the watch was no proof of con-
trivance, only a motive to induce the mind to think
so :

VII. And not less surprised to be informed, that
the watch in his hand was nothing more than the
result of the laws of metallic nature. It is a per-
version of language to assign any law as the effi-
cient, operative cause of anything. A law presup-
poses an agent ; for it is only the mode according
to which an agent proceeds : it implies a power ;
for it is the order according to which that power
acts. Without this agent, without this power,
which are both distinct from itself, the law does
nothing, is nothing. The expression, " the law of
metallic nature," may sound strange and harsh to
a philosophic ear ; but it seems quite as justifiable
as some others which are more familiar to him,
such as " the law of vegetable nature," " the law
of animal nature," or, indeed, as " the law of nature"
in general, when assigned as the cause of phenome-

8 NATURAL THEOLOGY.

na, in exclusion of agency and power, or when it
is substituted into the place of these.*

VIII. Neither, lastly, would our observer be
driven out of his conclusion, or from his confidence
in its truth, by being told that he knew nothing at
all about the matter. He knows enough for his ar-
gument : he knows the utility of the end : he knows
the subserviency and adaptation of the means to
the end. These points being known, his ignorance
of other points, his doubts concerning other points,
affect not the certainty of his reasoning. The con-
sciousness of knowing little need not beget a dis-
trust of that which he does know.

* When phftosophers and naturalists obsen^e a certain succes-
sion in the phenomena of the universe, they consider the uniformity
to exist through a laio of nalure. If they discover the order of
events, or phenomena, they say they have discovered the law : for
example, the law of affinities, of gravitation, &c. It is a loose ex-
pression ; for to obey a law supposes an understanding and a will
to comply. The phrase also implies that we know the nature of
the governing power which is in operation, and in the present case
both conditions are wanting.

The " law " is the mode in which the poM^er acts, and the term
should infer, not only an acquiescence in the existence of the power,
but of Him who has bestowed the power and enforced the law.

The term "force" is generally used instead of power, when the
intensities are measurable in their mechanical results.

NATURAL THEOLOGY.

CHAPTER II.

STATE OF THE ARGUMENT CONTINUED.

Suppose, in the next place, that the person who
found the watch should, after some time, discover
that, in addition to all the properties which he had
hitherto observed in it, it possessed the unexpected
property of producing, in the course of its move-
ment, another watch like itself (the thing is con-
ceivable) ; that it contained within it a mechanism,
a system of parts, a mould, for instance, or a com-
plex adjustment of lathes, files, and other tools,
evidently and separately calculated for this pur-
pose ; let us inquire what effect ought such a dis-
covery to have upon his former conclusion.

I. The first effect would be to increase his ad-
miration of the contrivance, and his conviction of
the consummate skill of the contriver. Whether he
regarded the object of the contrivance, the distinct
apparatus, the intricate, yet in many parts intelli-
gible mechanism by which it was carried on, he
would perceive, in this new observation, nothing
but an additional reason for doing what he had al-
ready done — for referring the construction of the
watch to design, and to supreme art. If that con-

10 NATURAL THEOLOGY.

struction imthout this property, or which is the same
thing, before this property had been noticed, prov-
ed intention and art to have been employed about
it, still more strong would the proof appear, when
he came to the knowledge of this further property,
the crown and perfection of all the rest.

II. He would reflect, that though the watch be-
fore him were, m soinc sense,i\\Q maker of the watch
which was fabricated in the course of its move-
ments, yet it was in a very different sense from
that in which a carpenter, for instance, is the maker
of a chair — the author of its contrivance, the cause
of the relation of its parts to their use. With re-
spect to these, the first watch was no cause at all
to the second ; in no such sense as this was it the
author of the constitution and order, either of the
parts which the new watch contained, or of the
parts by the aid and instrumentality of which it
was produced. We might possibly say, but with
great latitude of expression, that a stream of water
ground corn ; but no latitude of expression would
allow us to say, no stretch of conjecture could lead
us to think, that the stream of water built the mill,
though it were too ancient for us to know who the
builder was. What the stream of water does in
the affair is neither more nor less than this ; by the
application of an unintelligent impulse to a mechan-
ism previously arranged, arranged independently
of it, and arranged by intelligence, an effect is pro-
duced, viz., the corn is ground. But the effect re-
sults from the arrangement. The force of the

NATURAL THEOLOGY. 11

Stream cannot be said to be the cause or the author
of the effect, still less of the arrangement. Under-
standing and plan in the formation of the mill were
not the less necessary for any share which the water
has in grinding the corn ; yet is this share the same
as that which the watch would have contributed
to the production of the new watch, upon the sup-
position assumed in the last section. Therefore,
III. Though it be now no longer probable that
the individual watch which our observer had found
was made immediately by the hand of an artificer,
yet doth not this alteration in anywise affect the
inference, tliat an artificer had been originally em-
ployed and concerned in the production. The ar-
gument from design remains as it v/as. Marks of
design and contrivance are no more accounted for
now than they were before. In the same thing,
we may ask for the cause of difterent properties.
We may ask for the cause of the colour of a body,
of its hardness, of its heat ; and these causes may
be all different. We are now asking for the cause
of that subserviency to a use, that relation to an
end, which we have remarked in the watch before
us. No answer is given to this question, by telling
us that a preceding watch produced it. There
cannot be design without a designer ; contrivance,
without a contriver; order, without choice; ar-
rangement, without anything capable of arrang-
ing ; subserviency and relation to a purpose, with-
out that which could intend a purpose ; means suit-
able to an end. and executing their office in ac-

12 NATURAL THEOLOGY.

complishing that end, without the end ever having
been contemplated, or the means accommodated
to it. Arrangement, disposition of parts, subser-
viency of means to an end, relation of instruments
to a use, imply the presence of intelligence and
mind. No one, therefore, can rationally believe,
that the insensible, inanimate watch, from which
the watch before us issued, was the proper cause
of the mechanism we so much admire in it ; —
could be truly said to have constructed the instru-
ment, disposed its parts, assigned their office, de-
termined their order, action, and mutual depen-
dency, combined their several motions into one re-
sult, and that also a result connected with the utili-
ties of other beings. All these properties, there-
fore, are as much unaccounted for as they were
before.

IV. Nor is anything gained by running the dif-
ficulty farther back, i. e., by supposing the watch
before us to have been produced from another
w^atch, that from a former, and so on indefinitely.
Our o'oino- back ever so far, brin^rs us no nearer to
the least degree of satisfaction upon the subject.
Contrivance is still unaccounted for. We still
want a contriver. A designing mind is neither
supplied by this supposition, nor dispensed with.
If the difficulty were diminished the farther we
went back, by going back indefinitely we might
exhaust it. And this is the only case to which
this sort of reasoning applies. Where there is a
tendency, or, as we increase the number of terms,

NATURAL THEOLOGV. 13

a continual approach towai'ds a limit, there, by
supposing the number of terms to be what is called
infinite, we may conceive the limit to be attained ;
but where there is no such tendency or approach,
nothing is effected by lengthening the series.
There is no difference as to the point in question,
(whatever there may be as to many points,) be-
tween one series and another ; between a series
which is finite, and a series which is infinite. A
chain, composed of an infinite number of links, can
no more support itself than a chain composed of a
finite number of links. And of this we are assur-
ed; (though we never can have tried the experi-
ment,) because, by increasing the number of links,
from ten for instance to a hundred, from a hundred
to a thousand, &:c., we make not the smallest ap-
proach, we observe not the smallest tendency to-
wards self-support. There is no difference in this
respect (yet there may be a great difference in
several respects,) between a chain of a greater or
less length, between one chain and another, be-
tween one that is finite and one that is infinite.
This very much resembles the case before us.
The machine which we are inspecting demon-
strates, by its construction, contrivance and design.
Contrivance must have had a contriver; design, a
designer; whether the machine immediately pro-
ceeded from another machine or not. That cir-
cumstance alters not the case. That other ma-
chine may, in like manner, have proceeded from
a former machine : nor does that alter the case ;

8

14 NATURAL THEOLOGY.

the contrivance must have had a contriver. That
former one from one preceding it : no alteration
still ; a contriver is still necessary. No tendency
is perceived, no approach towards a diminution of
this necessity. It is the same with any and every
succession of these machines; a succession often,
of a hundred, of a thousand ; with one series, as
with another ; a series which is finite, as with a
series which is infinite. In whatever other re-
spects they may differ, in this they do not. In
all, equally, contrivance and design are unaccount-
ed for.

The question is not simply. How came the first
watch into existence ? which question, it may be
pretended, is done away by supposing the series
of watches thus produced from one another to
have been infinite, and consequently to have had
no suchj^?^^^, for which it was necessary to provide
a cause. This, perhaps, would have been nearly
the state of the question, if nothing had been be-
fore us but an unorganized, unmechanized sub-
stance, without mark or indication of contrivance.
It might be difficult to show that such substance
could not have existed from eternity, either in
succession (if it were possible, which I think it is
not, for unorganized bodies to spring from one an-
other,) or by individual perpetuity. But that is
not the question now. To suppose it to be so, is
to suppose that it made no diflference whether he
had found a watch or a stone. As it is, the meta-
physics of that question have no place : for, in the

NATURAL THEOLOGY. 15

watch which we are examining, are seen contri-
vance, design ; an end, a purpose ; means for the
end, adaptation to the purpose. And the question
which irresistibly presses upon our thoughts, is,
Whence this contrivance and design ? The thing
required is the intending mind, the adapted hand,
the intelhgence by which that hand was directed^
This question, this demand, is not shaken off, by
increasing a number or succession of substances
destitute of these properties; nor the more, by in-
creasing that number to infinity. If it be said
that, upon the supposition of one watch being pro-
duced from another in the course of that other's
movements, and by means of the mechanism
within it, we have a cause for the watch in my
hand, viz., the watch from which it proceeded, —
I deny, that for the design, the contrivance, the
suitableness of means to an end, the adaptation of
instruments to a use, (all of which we discover in
the watch,) we have any cause whatever. It is
in vain, therefore, to assign a series of such causes,
or to allege that a series may be carried back to
infinity; for I do not admit that we have yet any
cause at all for the phenomena, still less any series
of causes either finite or infinite. Here is contri-
vance, but no contriver; proofs of design, but no
designer.

V. Our observer would further also reflect, that
the maker of the watch before him was, in truth
and reality, the maker of every watch produced
from it : there being no difference (except that the

IC* NATURAL THEOLOGY.

latter manifests a more exquisite skill,) between the
making of another watch with his own hands, by
the mediation of tiles, lathes, chisels, &c., and the
disposing, fixing, and inserting of these instru-
ments, or of others equivalent to them, in the body
of the watch already made in such a manner, as
to form a new watch in the course of the move-
ments which he had given to the old one. It is
only working by one set of tools instead of an-
other.

The conclusion which the first examination of
the watch, of its w^orks, construction, and move-
ment, suggested, was, that it must have had, for
cause and author of that construction, an artificer
who understood its mechanism, and designed its
use. This conclusion is invincible. A second ex-
amination presents us with a new discovery. The
watch is found, in the course of its movement, to
produce another watch, similar to itself; and not
only so, but we perceive in it a system, or organi-
zation, separately calculated for that purpose.
What effect would this discovery have, or ought
it to have, upon our former inference? What, as
hath already been said, but to increase, beyond
measure, our admiration of the skill which had
been employed in the formation of such a ma-
chine ? Or shall it, instead of this, all at once
turn us round to an opposite conclusion, viz., that
no art or skill whatever has been concerned in the
business, although all other evidences of art and
skill remain as they were, and this last and su>

NATURAL THEOLOGY. 17

prenie piece of art he now added to the rest?
Can this be maintained without absurdity? Yet
this is atheism.*

* We must leave this logical and satisfactory argument un-
touched. In this chapter our author is laying the foundation for
a course of reasoning on the mechanism displayed in the animal
body. The argument in favour of a creating and presiding In-
telhgence may be drawn from the study of the laws of physical
agency: — such as the properties of heat, light, and sound; of
gravitation, and chemical combination; the structure of the globe,
the divisions of land and sea, the distribution of temperature ; nay,
the mind may rise to the contemplation of the sun and planets,
their mutual dependence, and their revolutions ; but, as affording
proofs obvious not only to cultivated reason but to plain sense,
almost to ignorance, there is nothing to be compared with that for
which our author is preparing the reader in this chapter, the me-
chanism of the animal body, and the adaptations which affect the
well-being of living creatures.

2*

18 NATURAL THEOLOGY.

CHAPTER III.

APPLICATION OF THE ARGUMENT.*

This is atheism: for every indication of contriv-
ance, eveiy manifestation of design, which existed
in the watch, exists in the works of nature ; with
the difference, on the side of nature, of being
greater and more, and that in a degree which ex-
ceeds all computation. I mean that the contriv-
ances of nature surpass the contrivances of art, in
the complexity, subtilty, and curiosity of the me-
chanism ; and still more, if possible, do they go
beyond them in number and variety ; yet in a
multitude of cases, are not less evidently mecha-
nical, not less evidently contrivances, not less evi-
dentlv accommodated to their end, or suited to
their office, than are the most perfect productions
of human ingenuity.

* The arguments adduced in this chapter being drawn from the
laws according to which light is refracted by the humours of
the eye, the reader may be inchned to peruse the few observations
on the elements of this part of physics in the Appendix, No. 16.

NATURAL THEOLOGY.

19

I know no better method of introducing so large
a subject, than that of comparing a single thing
with a single thing: an eye, for example, with a
telescope. As far as the examination of the instru-
ment goes, there is precisely the same proof that
the eye was made for vision, as there is that the
telescope was made for assisting it. They are
made upon the same principles ; both being ad-
justed to the laws by which the transmission and
refraction of rays of light are regulated. I speak
not of the origin of the laws themselves ; but such
laws being fixed, the construction in both cases is
adapted to them. For instance ; these laws re-
quire, in order to produce the same effect, that the
rays of light, in passing from water into the eye,
should be refracted by a more convex surface
than when it passes out of air into the eye. Ac-
cordingly we find that the eye of a fish, in that
part of it called the crystalline lens, is much rounder
than the eye of terrestrial animals. What plainer
manifestation of design can there be in this differ-
ence? What could a mathematical instrument
maker have done more to show his knowledge of
his principle, his application of that knowledge,

20 NATURAL THEOLOGY.

his suiting of his means to his end ; I will not say
to display the compass or excellence of his skill
and art, for in these all comparison is indecorous,
but to testify council, choice, consideration, pur-
pose ? *

To some it may appear a difference sufficient
to destroy all similitude between the eye and the

* The reader will find a comparison, more in detail, between
the eye and optical instruments, in the Appendix, No. 17.

In illustration of the instance adduced here, of the adaptation of
the fish's eye to tlie medium in which it lives, we may observe
that the powers in the human eye, for example, of drawing
the pencil of rays to a focus, and producing an accurate
image upon the expanded optic nerve (called the retina, from its
net- work structure,) in the bottom of the eye, depends principally
upon two circumstances, — the form of the cornea and the con-
vexity of the lens. That the cornea may produce this effect, it is
not only necessary that it should be convex, (as in the left-hand
figure on page 19,) but that the rays should enter it from a rarer
medium. As this cannot be effected in the water, the lens or crys-
talline humour, which is much denser than water, is brought into
operation. In the eye of an animal living in the atmosphere, the
lens is removed backwards, and resembles the optician's double
convex lens ; but in the fish it is a sphere, and brought in contact
with the transparent cornea, it not only has the power to concen-
trate the rays of light coming through the water, but by its altered
position it increases greatly the sphere of vision. (See the right-
hand figure, page 19.) To be critically correct, we may add that
it is not exactly the cornea which is deficient in the fish, but the
aqueous humour behind it. An aqueous fluid being thus both
behind and before the cornea, and that membrane being in a very
alight degree thicker in the centre than in the margin, this part of
the organ wliich is so efficient in the atmosphere is rendered use-
less in water. A man diving, for example, sees imperfectly, being
in something worse than the condition of an old man who re-
quires spectacles.

NATURAL THEOLOGY* 21

telescope, that the one is a perceiving organ, the
other an unperceiving instrument. The fact is
that they are both instruments. And as to the me-
chanism, at least as to mechanism being employed,
and even as to the kind of it, this circumstance
varies not the analogy at all. For observe what
the constitution of the eye is. It is necessary, in
order to produce distinct vision, that an image or
picture of the object be formed at the bottom of
the eye. Whence this necessity arises, or how
the picture is connected with the sensation, or con-
tributes to it, it may be difficult, nay, we will con-
fess, if 3 ou please, impossible for us to search out.
But the present question is not concerned in the
inquiry. It may be true, that, in this, and in other
instances, we trace mechanical contrivance a cer-
tain way ; and that then we come to something
which is not mechanical, or which is inscrutable.
But this affects not the certainty of our investiga-
tion, as far as we have gone. The difference be-
tween an animal and an automatic statue consists
in this, — that, in the animal, we trace the mecha-
nism to a certain point, and then we are stopped ;
either the mechanism being too subtile for our
discernment, or something else beside the known
laws of mechanism taking place ; w hereas, in the
automaton, for the comparitively few motions of
which it is capable, we trace the mechanism
throughout. But, up to the limit, the reasoning is
as clear and certain in the one case as in the
other. In the example before us, it is a matter of

22 NATURAL THEOLOGY.

certainty, because it is a matter which experience
and observation demonstrate, that the formation
of an image at the bottom of the eye is necessary
to perfect vision. The image itself can be shown.
Whatever aflects the distinctness of the image, af-
fects the distinctness of the vision. The formation
then of such an image being necessary (no matter
how,) to the sense of sight, and to the exercise of
that sense, the aparatus by which it is formed is
constructed and put together, not only with infi-
nitely more art, but upon the self-same principles
of art, as in the telescope or the camera-obscura.
The perception arising from the image may be
laid out of the question ; for the production of the
image, these are instruments of the same kind.
The end is the same ; the means are the same.
The purpose in both is alike ; the contrivance for
accomplishing that purpose is in both alike. The
lenses of the telescopes, and the humours of the
eye, bear a complete resemblance to one another,
in their figure, their position, and in their power
over the rays of light, viz. in bringing each pencil
to a point at the right distance from the lens ;
namely, in the eye, at the exact place where the
membrane is spread to receive it. How is it pos-
sible, under circumstances of such close affinity,
and under the operation of equal evidence, to ex-
clude contrivance from the one ; yet to acknow-
ledge the proof of contrivance having been em-
ployed, as the plainest and clearest of all propo*
sitions, in the other ?

NATURAL THEOLOGY. 23

The resemblance between the two cases is still
more accurate, and obtains in more points than
we have yet represented, or than we are, on the
first view of the subject, aware of. In dioptric te-
lescopes there is an imperfection of this nature.
Pencils of light, in passing through glass lenses,
are separated into ditferent colours, tlTereby ting-
ing the object, especially the edges of it, as if it
were viewed through a prism. To correct this in-
convenience had been long a desideratum in the art.
At last it came into the mind of a sagacious opti-
cian, to inquire how this matter was managed in
the eye : in which there was exactly the same dif-
ficulty to contend with as in the telescope. His
observation taught him, that, in the eye, the evil
was cured by combining lenses composed of dif-
ferent substances, i. e. of substances which pos-
sessed different refracting powers. Our artist
borrowed thence his hint ; and produced a correc-
tion of the defect by imitating, in glasses made
from different materials, the effects of the different
humours through wiiich the rays of light pass be-
fore they reach the bottom of the eye. Could this
be in the eye without purpose, which suggested
to the optician the only effectual means of attain-
ing that purpose ?*

* This is an interesting part of the inquir)', which will be found
more fully explained in the Appendix.

It is not, accurately speaking, " glasses of different refracting
powers" which are required. Refraction is the new direction
which the ray takes in passing from one transparent body into

24 NATURAL THEOLOGY.

But further; there are other points, not so much
perhaps of strict resemblance between the two,
as of superiority of the eye over the telescope ;
yet of a superiority which, being founded in the
laws that regulate both, may furnish topics of fair
and just comparison. Two things were wanted
to the eye, which were not wanted (at least in the
same degree) to the telescope; and these were
the adaptation of the organ, first, to different de-
grees of light ; and secondly, to the vast diversity
of distance at which objects are viewed by the
naked eye, viz. from a few inches to as many
miles. These difficulties present not themselves
to the maker of the telescope. He wants all the
light he can get; and he never directs his instru-
ment to objects near at hand. In the eye, both
these cases were to be provided for; and for the
purpose of providing for them, a subtile and ap-
propriate mechanism is introduced.

[The next figure represents a section of the anterior part of the
human eye : — A, A, the iris ; B, the object, from which the rays
strike ofFin all directions : a pencil of these enters at the pupil ; a
portion is intercepted by the iris A, A. The pencil which enters.
the eye, passing through the lens, converges to form the image.
But the spaces C, C, are deprived of rays by the intervention of
the iris A, A. Yet this in no measure affects the size of the image
but only diminishes the intensity of its illumination. By the con-

another of different density. Dispersion is the separation of the
beam of light into differently coloured rays. A piece of glass may
differ from another in its power of refracting, and also in its pro-
perty of dispersing. It is by duly arranging these different proper-
ties that the achromatic telescope is formed.

NATURAL THEOLOGY. 25

traction of the iris, and consequent enlargement of the pupil, a
larger pencil of rays is admitted. It is remarkable that the image
formed on the retina must always be inverted, and yet such is the
power of habit and experience, derived from touching objects,
that we see things as they are in reality, and not as they are paint-
ed in our eyes — experience thus correcting the errors of sense. It
is in the same way that we see single, though we have an image
made in each eye. But if we change the ordinary position of our
eye, the habit is broken, and we see double.]

I. In order to exclude excess of light, when it
is excessive, and to render objects visible under
obscurer degrees of it, when no more can be had,
the hole or aperture in the eye, through which the
light enters, is so formed as to contract or dilate
itself for the purpose of admitting a greater or less
number of rays at the same time. The chamber
of the eye is a camera-obscura, which, when the
light is too small, can enlarge its opening ; when
too strong, can again contract it ; and that without
any other assistance than that of its own exquisite
machinery. It is farther also, in the human sub-
ject, to be observed, that this hole in the eye,
which w^e call the pupil, under all its different di-
mensions, retains its exact circular shape. This
is a structure extremely artificial. Let an artist

3

26 NATURAL THEOLOGY.

only try to execute the same; he will find that his
threads and strings must be disposed with great
consideration and contrivance, to make a circle
which shall continually change its diameter yet
preserve its form. This is done in the eye by
an apphcation of fibres, i. e. of strings similar, in
their position and action, to what an artist would
and must employ, if he had the same piece of
workmanship to perform.

[This figure represents the iris separated from the eye and laid
out flat. We perceive the straight fibres passing towards the
inner margin, and the circular fibres running round the margin.]

II. The second difficulty which has been stated
was the suiting of the same organ to the percep-
tion of objects that lie near at hand, w^ithin a few
inches, we will suppose, of the eye, and of objects
which are placed at a considerable distance from
it, that, for example, of as many furlongs, (I speak
in both cases of the distance at which distinct
vision can be exercised.) Now this, according to
the principles of optics, that is, according to the
laws by which the transmission of light is regula-

NATURAL THEOLOGY. 27

ted (and these laws are fixed,) could not be done
without the organ itself undergoing an alteration,
and receiving an adjustment, that might correspond
with the exigency of the case, that is to say, with
the different inclination to one another under
which the rays of light reached it. Rays issuing
from points placed at a small distance from tlie
eye, and which consequently must enter the eye
in a spreading or diverging order, cannot, by the
same optical instrument in the same state, be
brought to a point, i. e. be made to form an image,
in the same place with rays proceeding from ob-
jects situated at a much greater distance, and
which rays arrive at the eye in directions nearly
(and physically speaking,) parallel. It requires a
rounder Jens to do it. The point of concourse be-
hind the lens must fall critically upon the retina,
or the vision is confused ; yet, other things re-
maining the same, this point, by the immutable
properties of light, is carried further back when
the rays proceed from a near object than when
they are sent from one that is remote. A person
who was using an optical instrument would man-
age this matter by changing, as the occasion re-
quired, his lens or his telescope, or by adjusting
the distance of his glasses with his hand or his
screw : but how is this to be managed in the eye ?
What the alteration w^as, or in what part of the
eye it took place, or by what means it w as effect-
ed, (for if the known laws which govern the re-
fraction of light be maintained, some alteration in

28 NATURAL THEOLOGY.

the state of the organ there must be,) had long
formed a subject of inquiry and conjecture. The
change, though sufficient for the purpose, is so
minute as to elude ordinary observation. Some
very late discoveries, deduced from a laborious
and most accurate inspection of the structure and
operation of the organ, seem at length to have
ascertained the mechanical alteration which the
parts of the eye undergo. It is found, that by the
action of certain muscles, called the straight mus-
cles, and which action is the most advantageous
that could be imagined for the purpose, it is found
I say, that whenever the eye is directed to a near
object, three changes are produced in it at the
same time, all severally contributing to the adjust-
ment required. The cornea, or outermost coat of
the eye, is rendered more round and prominent ;
the crystalline lens underneath is pushed forward i
and the axis of vision, as the depth of the eye is
called, is elongated. These changes in the eye
vary its power over the rays of light in such a
manner and degree as to produce exactly the ef-
fect which is wanted, viz. the formation of an im-
age tipoiL the j^etina, whether the rays come to the
eye in a state of divergency, which is the case
when the object is near to the eye, or come paral-
lel to one another, which is the case when the ob-
ject is placed at a distance. Can anything be
more decisive of contrivance than this is ? The
most secret laws of optics must have been known
to the author of a structure endowed with such a

NATURAL THEOLOGY.

29

capac'ty of change. It is as though an optician,
when he had a nearer object to view, should rec-
tify his instrument by putting in another glass, at
the same time drawing out also his tube to a differ-
ent length.^

Observe a new-born child first lifting up its eye-
lids. What does the opening of the curtain dis-
cover ? The anterior part of two pellucid globes,
which, when they come to be examined, are found
to be constructed upon strict optical principles;
the self-same principles upon which we ourselves

9 This is a subject over M^hich there is still great obscurity, and
on which adverse experiments and opinions are recorded. How-
ever difficult it may be to account for the mode of adjustment, yet
the property is not denied, and therefore the argument in the text
remains. That there is something in the sensibility of the nerve,
and in the power of attention, there seems no doubt. Birds of
prey, it has been noticed, possess a power of vision of which we
can hardly form a conception. Where it is the object to snare the
falcon, a pigeon is tied, in an exposed situation, with a cord so at-
tached that a person concealed can flutter the bird, or make it ex-
tend its wings ; and although no bird of prey be visible in the
whole sky, presently the hawk will be seen descending to pounce
upon the pigeon. The endowment of the bird's eye must be dif-
ferent from ours, else the bird of prey could not see the most mi-
nute object when hovering at a great height; nor, in sweeping
down upon his quarry, could he strike it with precision. Nothing
of the nature of mere mechanical provision can account for the
possession of this superior power. One instance of the power of
adjustment which the eye has under the influence of the will,
seems to be this. Let a person who cannot read distinctly, or at
all, without spectacles, at a given distance, look at a word through
a very small aperture, and he will see what he before could not
without spectacles. This can hardly be explained by the removal
of the lateral Ught, or by inflexion.

3*

30 jVatural theology.

construct optical instruments. We find them per-
fect for the purpose of forming an image by re-
fraction : composed of parts executing ditTerent
offices: one part having fulfilled its office upon the
pencil of light, delivering it over to the action of
another part : that to a third, and so onward : the
progressive action depending for its success upon
the nicest and minutest adjustment of the parts
concerned : yet these parts so in fact adjusted as
to produce, not by a simple action or eftect, but by
a combination of actions and effects, the result
which is uhimately wanted. And forasmuch as
this organ w'ould have to operate under different
circumstances, with strong degrees of light and
with weak degrees, upon near objects and upon
remote ones, and these differences demanded, ac-
cording to the laws by which the transmission of
light is regulated, a corresponding diversity of
structure, — that the aperture, for example, through
which the light passes should be larger or less —
the lenses rounder or flatter — or that their dis-
tance from the tablet upon w^hich the picture is
delineated should be shortened or lengthened, —
this, I say, being the case, and the difficulty to which
the eye w^as to be adapted, we find its several
parts, capable of being occasionally changed, and
a most artificial apparatus provided to produce
that change. This is far beyond the common
regulator of a watch, which requires the touch of
a foreign hand to set it ; but it is not altogether
unlike Harrison's contrivance for making a watch

NATURAL THEOLOGY. 31

regulate itself, by inserting within it a machinery
which, by the artful use of the different expansion
of metals, preserves the equability of the motion
under all the various temperatures of heat and
cold in which the instrument may happen to be
placed. The ingenuity of this last contrivance
has been justly praised. Shall, therefore, a struc-
ture which difters from it chiefly by surpassing it,
be accounted no contrivance at all? or, if it be a
contrivance, that it is without a contriver ?

But this, though much, is not the whole : by dif-
ferent species of animals the faculty we are de-
scribing is possessed in degrees suited to the dif-
ferent range of vision which their mode of life and
of procuring their food requires. Birds, for in-
stance, in general, procure their food by means of
their beak ; and, the distance between the eye and
the point of the beak being small, it becomes ne-
cessary that they should have the power of seeing
very near objects distinctly. On the other hand,
from being often elevated much above the ground,
living in the air, and moving through it with great
velocity, they require for their safety, as well as
for assisting them in descrying their prey, a power
of seeing at a great distance; a power of which,
in birds of rapine, surprising examples are given.
The fact accordingly is, that two peculiarities are
found in the eyes of birds, both tending to facili-
tate the change upon which the adjustment of the
eye to different distances depends. The one is a
bony, yet, in most species, aHexible rim or hoop.

32 NATURAL THEOLOGY.

surrounding the broadest part of the eye, which
confining the action of the muscles to that part, in-
creases the eftect of their lateral pressure upon the
orb, by which pressure its axis is elongated for the
purpose of looking at very near objects. The other
is an additional muscle, called the marsupium, to
draw, on occasion, the crystalline lens hack, and to
fit the same eye for the viewing of very distant ob-
jects. By these means, the eyes of birds can pass
from one extreme to another of their scale of ad-
justment, with more ease and readiness than the
eyes of other animals.

The eyes o^ fishes also, compared with those of
terrestrial animals, exhibit certain distinctions of
structure, adapted to their state and element. We
have already observed upon the figure of the crys-
talline compensating by its roundness the density
of the medium through which their light passes.
To which we have to add, that the eyes of fish, in
their natural and indolent state, appear to be ad-
justed to near objects, in this respect diflfering from
the human eye, as well as those of quadrupeds and
birds. The ordinar}^ shape of the fish's eye being
in a much higher degree convex than that of land
animals, a corresponding difference attends its mus-
cular conformation, viz., that it is throughout cal-
culated ^oY flattening the eye.

The iris also in the eyes of fish does not admit
of contraction. This is a great dift'erence, of which
the probable reason is, that the diminished light in
water is never too strong for the retina.

NATURAL THEOLOGY.

33

In the eel, which has to work its head through
sand and gravel, the roughest and harshest sub-
stances, there is placed before the eye, and at some
distance from it, a transparent, horny, convex case
or covering, which, without obstructing the sight,
defends the organ. To such an animal could any-
thinor be more wanted or more useful ?

Thus, in comparing the eyes of different kinds
of animals, we see in their resemblances and dis-
tinctions one general plan laid down, and that plan
varied with the varying exigencies to which it^is to
be applied."'

1"^ In viewing the structure of the eye as adjusted to the condition
of fishes, we may remark the pecuhar thickness of the sclerotic
coat in the whale. Although he breathes the atmosphere, and lies
out on the surface of the water ; to escape his enemies he will
plunge some hundred fathoms deep. The pressure therefore must
be very great upon his surface, and on the surface of the eye. If
a cork be knocked into the mouth of a bottle, so that it resists all
further pressure that we can make upon it, and if this bottle be
carried, by being attached to the sounding-lead, to a great depth in
the sea, the pressure of the water will force in the cork, and fill the
bottle ; for the cork is pressed with a force equal to the weight of
the column of water above it, of which it is the base. It is pressed
in all directions equally, so that a common-sized cork is reduced to
the size of that of a phial bottle.

"A creature hving at the depth of 100 feet would sustain a pres-

34 NATURAL THEOLOGY.

There is one property, however, common, I be-
lieve, to all eyes, at least to all w^hich have been
examined,* namely, that the optic nerve enters the

sure, including that of the atmosphere, of about 60 pounds on the
square incli ; while one at 4000 feet, a depth by no means consid-
erable, would be exposed to a piessure of about 1830 pounds upon
the square inch." — De La Beche, Tlieor. Geol. p. 243.

We can therefore comprehend how it shall happen, that on the
foundering of a ship at sea, though its timbers part, not a spar floats
to the surface ; everything is swallowed up ; for, if the hull has sunk
to a great depth, all that is porous is penetrated with water, or com-
pressed, and consequently remains where it sunk. So it happened,
and the fact goes directly to our purpose, that when, by the en-
tangling of the line of the harpoon, the boat was carried down with
tlie whale, and, being recovered, it required two boats to keep it at
the surface. — Scoresby.

We may easily conceive, therefore, the pressure which the eye
of the whale sustains when it dives, and why it is formed ■with the
provisions wliich we are about to descrilie. When we make a
eection of the whole eye, cutting through the cornea, the sclerotic
coat, which is dense as tanned leather, increases in thickness to-
wards the back part, and is full five times the tliickness behind,
that it is at the anterior part. The anterior part of the eye sustains
the pressure from without, and requires no additional support ; but
were the back part to yield, the globe would be then distended in
tliat direction, and the whole interior of the eye consequently suffer
derangement. We perceive, therefore, the necessity of the coats
being thus so remarkably strengthened behind. The natural ene-
mies of the whale are the sword-fish and the ^hark ; and it is stat-
ed with some show of reason, that tiiis huge creature, being with-
out means of defence of any kind, carries his enemies that have
fixed upon him to a depth of water, and consequently to a pressure,
which subdues them, as their bodies are not constituted for such
depths. It is under this instinct, that when the whale receives the
hajpoon, he dives to the bottom.

♦ The eye of the seal or sea-calf, I understand, is an exception.
Mem. A^ad, Paris, 1710, p. 123. — Paley.

NATURAL THEOLOGY. 35

bottom of the eye, not in the centre or middle, but
a little on one side : not in the point where the axis
of the eye meets the retina, but between that point
and the nose. The difference which this makes is,
that no part of an object is unperceived by both
eyes at the same time.

In considering vision as achieved by the means
of an image formed at the bottom of the eye, we
can never reflect without wonder upon the small-
ness yet correctness of the picture, the subtility of
the touch, the fineness of the lines. A landscape
of five or six square leagues is brought into a space
of half an inch diameter ; yet the multitude of ob-
jects which it contains are all preserved, are all dis-
criminated in their magnitudes, positions, figures,
colours. The prospect from Hampstead-hill is com-
pressed into the compass of a sixpence, yet circum-
stantially represented. A stage-coach, travelling
at an ordinary speed for half an hour, passes, in
the eye, only over one-twelfth of an inch, yet is this
change of place in the image distinctly perceived
throughout its whole progress ; for it is only by
means of that perception that the motion of the
coach itself is made sensible to the eye. If any-
thing can abate our admiration of the smallness of
the visual tablet compared with the extent of vis-
ion, it is a reflection w^hich the view of nature leads
up every hour to make, viz., that, in the hands of
the Creator, great and little are nothing.

Sturmius held, that the examination of the eye
was a cure for atheism. Besides that conformity

36 NATURAL THEOLOGY.

to Optical principles which its internal constitution
displays, and which alone amounts to a manifesta-
tion of intelligence having been exerted in the struc-
ture ; besides this, which forms, no doubt, the lead-
ing character of the organ, there is to be seen, in
everything belonging to it and about it, an extra-
ordinary degree of care, an anxiety for its preser-
vation, due, if we may so speak, to its value and
its tenderness. It is lodged in a strong, deep, bony
socket, composed by the junction of seven different
bones,* hollowed out at their edges. In some few
species, as that of the coatimondi,-|- the orbit is not
bony throughout ; but whenever this is the case, the
upper, which is the deficient part, is supplied by a
cartilaginous ligament ; a substitution which shows
the same care. Within this socket it is embedded
in fat, of all animal substances the best adapted
both to its repose and motion. It is sheltered by
the eyebrows — an arch of hair, which, like a thatch-
ed penthouse, prevents the sweat and moisture of
the forehead from running down into it.

But it is still better protected by its lid. Of the
superficial parts of the animal frame, I know none
which, in its office and structure, is more deserving
of attention than the eyelid. It defends the eye ;
it wipes it ; it closes it in sleep. Are there, in any
work of art w^hatever, purposes more evident than
those which this organ fulfils ? or an apparatus for
executing those purposes more intelligible, more

* Heister, sect. 89. f Mem. R. Ac. Paris, p. \\1. — Foley.

NATURAL THEOLOGY. 37

appropriate, or more mechanical ? If it be over-
looked by the observer of nature, it can only be
because it is obvious and familiar. This is a ten-
dency to be guarded against. We pass by the plain-
est instances, whilst we are exploring those which
are rare and curious ; by w4iich conduct of the
understanding, w^e sometimes neglect the strong-
est observations, being taken up w4th others w^hich,
though more recondite and scientific, are, as solid
arguments, entitled to much less consideration.

In order to keep the eye moist and clean (which
qualities are necessary to its brightness and its use,)
a wash is constantly supplied by a secretion for the
purpose ; and the superfluous brine is conveyed to
the nose through a perforation in the bone as
large as a goose-quill. When once the fluid has
entered the nose, it spreads itself upon the inside
of the nostril, and is evaporated by the current of
warm air which, in the course of respiration, is con-
tinually passing over it. Can any pipe or outlet,
for carrying off the waste liquor from a dye-house
or a distillery, be more mechanical than this is ? It
is easily perceived that the eye must want moisture :
but could the w^ant of the eye generate the gland
which produces the tear, or bore the hole by which
it is discharged — a hole through a bone ?

It is observable that this provision is not found
in fish — the element in which they live supplying
a constant lotion to the eye.'^

" We have entered into a much fuller explanation of the appa-

4

38 NATURAL THEOLOGY.

It were, however, injustice to dismiss the eye
as a piece of mechanism, witliout noticing that
most exquisite of all contrivances, the nictitating
memhrane^ which is found in the eyes of birds,
and of many quadrupeds. Its use is to sweep the
eye, which it does in an instant ; to spread over it
the lacrymal humour ; to defend it also from sud-
den injuries ; yet not totally, when drawn upon the
pupil, to shut out the light. The commodiousness
with which it lies folded up in the upper corner
of the e3'e, ready for use and action, and the
quickness with which it executes its purpose, are
properties known and obvious to every observer ;
but vv^hat is equally admirable, though not quite so
obvious, is the combination of two kinds of substance,
muscular and elastic, and of two different kinds of
action, by which the motion of this membrane is
performed. It is not, as in ordinary cases, by the
action of two antagonist muscles, the one pulling
forward, and the other backward, that a recipro-
cal change is effected ; but it is thus : the mem-
brane itself is an elastic substance, capable of
being drav;n out by force like a piece of elastic
gum, and by its own elasticity returning, when
the force is removed, to its former position. Such

ratus for the presen-ation of the eye, in the Appendix, there being
a crrcat deal that is curious in it hitherto unnoticed. It will be there
found that, ahhough the eye of the fish has no eyelid, yet it has the
rapid motion of the eye-ball, which, under water, must serve to free
it from any impurity. Some curious instances are, at the same
time, aiforded, of a still more artificial mode, in the lobster and
crab, of removing whatever obstructs the sight.

NATURAL THEOLOGY. 39

being its nature, in order to fit it up for its office, it is
connected by a tendon or thread, with a muscle
in the back part of the eye : this tendon or thread,
though strong, is so fine as not to obstruct the sight,
even when it passes across it ; and the muscle itself,
being placed in the hack part of the eye, derives
from its situation the advantage, not only of being
secure, but of being out of the way ; which it would
hardly have been in any position that could be as-
signed to it in the anterior part of the orb, where
its function lies. When the muscle behind the
eye contracts, the membrane, by means of the
communicating thread, is instantly drawn over the
fore-part of it. When the muscular contraction
(which is a positive and most probably a volun-
tary effort,) ceases to be exerted, the elasticity
alone of the membrane brings it back again to its
position.* Does not this, if anything can do it, be-
speak an artist, master of his work, acquainted with
his materials ? " Of a thousand other things," say
the French Academicians, "we perceive not the
contrivance, because we understand them only by
their effects, of which we know not the causes :
but we here treat of a m.achine, all the parts
whereof are visible, and which need only be looked
upon to discover the reasons of its motion and
action, f *'

* Phil. Trans. 1796.

t Memoirs for a Natural History of Animals, by the Royai
Academy of Sciences at Paris, done into English by order of the
E,ojal Society, 1701, p. 249. — Foley .

40 KATURAL THEOLOGY.

In the. configuration of the muscle which, though
placed behind the eye, draws the nictitating mem-
brane over the eye, there is, what the authors just
now quoted deservedly call a marvellous mecha-
nism. I suppose this structure to be found in other
animals ; but, in the memoirs from which this ac-
count is taken, it is anatomically demonstrated
only in the cassowary. The muscle is passed
through a loop formed by another rauscle ; and is
there inflected as if it were round a pully. This
is a peculiarity, and observe the advantage of it.
A single muscle \\'ith a straight tendon, which is
the common muscular form, would have been suf-
ficient, if it had had power to draw far enough. But
the contraction necessary to draw the membrane
over the wiiole eye, required a longer muscle than
could lie straight at the bottom of the eye. There-
fore, in order to have a greater length in a less
compass, the chord of the main muscle makes an
angle. This so fai' answers the end; but still fur-
ther, it makes an angle, not round a fixed pivot,
but round a loop formed by another muscle, w hich
second muscle, whenever it contracts, of course
twitches the first muscle at the point of inflection,
and thereby assists the action designed by both.'^

^^There is one effect, however, of this apparatus, which our author
has omitted to notice — that is, the rapidity of motion in tlie mein-
brana nictitans, produced by the obhque direction and junction of
the tendons of these muscles, this will be illustrated hereafter.

The mtmhrana nictitans is peculiar to birds : the term is not ap-
plicable to the corresponding structure in quadrupeds, the object

NATURAL THEOLOGY. 41

One question may possibly have dwelt in the
reader's mind during the perusal of these observa-
tions, namely, why should not the Deity have given
to the animal the faculty of vision at once ? Why
this circuitous perception ; the ministry of so many
means ; an element provided for the purpose ; re-
fleeted from opaque substances, refracted through
transparent ones ; and both according to precise
laws ; then, a complex organ, an intricate and
artificial apparatus, in order, by the operation of
this element, and in conformity with the restric-
tions of these laws, to produce an image upon a
membrane communicating with the brain? Where-
fore all this ? Why make the difficulty in order
to surmount it ? If to perceive objects by some
other mode than that of touch, or objects which
lay out of the reach of that sense, were the thing
proposed, could not a simple volition of the Cre-
ator have communicated the capacity? Why
resort to contrivance, where power is omnipotent ?
Contrivance, by its very definition and nature, is
the refuge of imperfection. To have recourse to

being there obtained by a very different mechanism. The haio is
a thin cartilage, which, lying between the eye-ball and the inner
part of the orbit, flies rapidly out, and sweeps the surface of the
eye in a manner much more perfect than can be performed by the
outer eyelids. Every one who has ridden a horse in a dusty road,
must have been struck with the superior provision in the horse's
eye : he never suffers from the dust, because, this cartilage, being
bedewed by the secretion of a peculiar gland, not tears, but a mat-
ter more glutinous, sweeps across the eye, and collects and re-
moves every particle of dust,

4*

42 NATURAL THEOLOGY.

expedients implies difficulty, impediment, restraint,
defect of power. This question belongs to the
other senses, as well as to sight ; to the general
functions of animal life, as nutrition, secretion, res-
piration ; to the economy of vegetables ; and in-
deed to almost all the operations of nature. The
question, therefore, is of very wide extent ; and
amongst other answers vdiich may be given to it,
besides reasons of which probably we are igno-
rant, one answer is this : It is only by the display
of contrivance that the existence, the agency, the
wisdom of the Deity, could be testified to his ra-
tional creatures. This is the scale by which we
ascend to all the knowledge of our Creator which
we possess, so far as it depends upon the pheno-
mena, or the works of nature. Take away this,
and you take away from us every subject of ob-
servation, and ground of reasoning ; I mean, as
our rational faculties are formed at present. What-
ever is done, God could have done Vv^ithout the in-
tervention of instruments or means ; but it is in
the construction of instruments, in the choice and
adaptation of means, that a creative intelligence is
seen. It is this which constitutes the order and
beauty of the universe. God, therefore, has been
pleased to prescribe limits to his own power, and
to work his ends within those limits.^^ The general
laws of matter have perhaps prescribed the nature

15 This subject is touched upon in the introductory observations
to the Appendix.

NATURAL THEOLOGY. 43

of these limits ; its inertia ; its reaction ; the laws
which govern the communication of motion, the
refraction and reflection of light, and the constitu-
tion of fluids non-elastic and elastic, the transmis-
sion of sound through the latter ,• the laws of mag-
netism, of electricity ; and probably others yet un-
discovered. These are general laws ; and when
a particular purpose is to be effected, it is not by
making a new law, nor by the suspension of the old
ones, nor by making them wind, and bend, and
yield to the occasion (for nature with great steadi-
ness adheres to and supports them) ; but it is, ag
we have seen in the eye, by the interposition of an
apparatus, corresponding with these laws, and
suited to the exigency which results from them,
that the purpose is at length attained. As we have
said, therefore, God prescribes hmits to his powder,
that he may let in the exercise and thereby exhi-
bit demonstrations of his wisdom. For then, ?. e.,
such laws and limitations being laid down, it is as
though one Being should have fixed certain rules,
and, if we may so speak, provided certain materi-
als, and afterwards have committed to another
Being, out of these materials, and in subordination
to these rules, the task of drawing forth a creation :
a supposition which evidently leaves room, and in-
duces indeed a necessity for contrivance. Nav,
there may be many such agents, and many ranks of
these. We do not advance this as a doctrine either
of philosophy or of religion ; but we say that the
subject may safely be represented under this view ;

44 NATURAL THEOLOGY.

because the Deity, acting himself by general laws,
will have the same consequences upon our rea-
soning, as if he had presbribed these laws to an-
other. It has been said, that the problem of cre-
ation was, " attraction and matter being given, to
make a world out of them f and, as above ex-
plained, this statement perhaps does not convey a
false idea.

We have made choice of the eye as an instance
upon which to rest the argument of this chapter.
Some single example was to be proposed ; and
the eye offered itself under the advantage of ad-
mitting of a strict comparison with optical instru-
ments. The ear, it is probable, is no less artifi-
cially and mechanically adapted to its office than
the eye. But we know less about it : we do not
so well understand the action, the use, or the mu-
tual dependency of its internal parts.'^ Its general
form, however, both external and internal, is suf-
ficient to show that it is an instrument adapted to
the reception oi sound; that is to say, already know-
ing that sound consists in pulses of the air, we per-
ceive, in the structure of the ear, a suitableness to
receive impressions from this species of action, and
to propagate these impressions to the brain. For
of what does this structure consist? An external

" The reader will find a dissertation on the ear in the Appen-
tlix. Other authors, as well as Dr. Paley, have said that we do
not understand the uses or mutual dependency of the internal parts
of the ear: an observation either not very intelligible, or which
shows them to have studied it superficially.

NATURAL THEOLOGY.

45

ear (the concha) calculated, like an ear trumpet,
to catch and collect the pulses of which we have

Explanation of the Plan of the Ear. — A, the tube of the ear, hav-
ing Httle glands to secrete the wax, and hairs standing across it
to exclude insects, without impeding the vibrations of the atmos-
phere ; B, the membrane of the tympanum drawn into the form of
a funnel by the attachment of the malleus; C, the chain of four
bones lying in the irregular cavity of the tympanum^ and commu-
nicating the vibrations of the membrane B to the fluid in the laby-
rinth ; D, Etistachian tube, which forms a communication between
the throat and the tympanum, so as to preserve an equilibrium of
the air in the cavity of the tympanum and the atmosphere ; E, F,
the labyrinth, consisting of a central cavity, the vestibule ; the
three semicircular canals, E, and the cochlea, F.

Beginning from the left hand we have the malleus, or hammer,
the first of the chain of bones ; we see the long handle or process
which is attached to the membrane of the tympanum, and which
moves with the vibrations of that membrane; the other end is en-
larged, and has a groove upon it which is articulated with the next

46 NATURAL THEOLOGY.

Spoken ; in large quadrupeds, turning to the sound,
and possessing a configuration, as v.ell as motion,
evidently fitted for the office : of a tube which leads
into the head, lying at the root of this outward ear,
the folds and sinuses thereof tending and conduct-
ing the air tow^ards it: of a thin membrane, like the
pelt of a drum, stretched across this passage upon
a bony rim : of a chain of movable and infinitely
curious bones, forming a communication, and the
only communication that can be observed, between
the membrane last mentioned and the interior chan-
nels and recesses of the skull : of cavities, similar
in shape and form to wind instruments of music,
being spiral or portions of circles : of the eusta-
chian tube, like the hole in a drum, to let the air
pass freely into and out of the barrel of the ear,
as the covering membrane vibrates, or as the tem-
perature may be altered : the whole labyrinth hewn
out of a rock ; that is, wrought into the substance
of the hardest bone of the body. This assemblage

bone. The second bone is the incus, or anvil, to the grooved sur-
face of which the malleus is attached. A long process extends
from this bone, which has upon it the os orhiculare; and to this
third bone there is attached a fourth, the stapes, which is in shape
like a stirrup iron. The base of this bone is of an oval shape, and
rests upon a membrane which closes the hole leading into the
labj-rinth. This hole is called foramen ovale. The plan of the
cochlea shows that one of its spiral passages, beginning in the ves-
tibule, winds rotmd the pillar till it meets in a point with another
tube. If the eye follow this second spiral tube, it will be found to
lead, not into the vestibule, but into the irregular cavity of the
tympanum.

NATURAL THEOLOGY.

47

of connected parts constitutes together an appara-
tus plainly enough relative to the trasmission of
sound, or of the impulses received from sound, and
only to be lamented in not being better under-
stood.

The communication within, formed by the small
bones of the ear, is, to look upon, more like what
we are accustomed to call machinery, than any
thing I am acquainted with in animal bodies. It
seems evidently designed to continue towards the
sensorium the tremulous motions which are ex-
cited in the membrane of the tympanum, or what
is better known by the name of the " drum of the
ear." The compages of bones consists of four,

[This figure represents the bones which form
the chain.]

which are so disposed, and so hinge upon one an-
other, as that if the membrane, the drum of the
ear, vibrate, all the four are put in motion toge-

48 NATURAL THEOLOGY.

ther ; and, by the result of their action, work the
base of that which is the last in the series, upon
an aperture which it closes, and upon which it
plays, and which aperture opens into the tortuous
canals that lead to the brain. This last bone of
the four is called the staj^es. The office of the
drum of the ear is to spread out an extended sur-
face, capable of receiving the impressions of sound,
and of being put by them into a state of vibration.
The office of the stapes is to repeat these vibra-
tions. It is a repeating frigate, stationed more
within the line. From which account of its action
may be understood how the sensation of sound
will be excited by any thing which communicates
a vibratory motion to the stapes, though not, as in
all ordinary cases, through the intervention of the
membrana tympani. This is done by solid bodies
applied to the bones of the skull, as by a mental
bar h olden at one end between the teeth, and
touching at the other end a tremulous body. It
likewise appears to be done, in a considerable de-
gree, by the air itself, even when this membrane,
the drum of the ear, is greatly damaged. Either
in the natural or preternatural state of the organ,
the use of the chain of bones is to propagate the
impulse in a direction towards the brain, and to
propagate it with the advantage of a lever ; which
advantage consists in increasing the force and
strength of the vibration, and at the same time
diminishing the space through which it oscillates ;

NATURAL THEOLOGY. 49

both of which changes may augment or facilitate
the still deeper action of the auditory nerves,'^

The benefit of the eustachian tube to the organ
may be made out upon pneumatic principles. Be-
hind the drum of the ear is a second cavity, or
barrel, called the tympanum. The eustachian
tube is a slender pipe, but sufficient for the pas-
sage of air, leading from this cavity into the back
part of the mouth. Now, it would not have done
to have had a vacuum in this cavity; for, in that
case, the pressure of the atmosphere from without
would have burst the membrane which covered it.
Nor would it have done to have filled the cavity
with lymph, or any other secretion ; which would
necessarily have obstructed, both the vibration of
the membrane and the play of the small bones.
Nor, lastly, would it have done to have occupied
the space with confined air, because the expansion
of that air by heat, or its contraction by cold, would
have distended or relaxed the covering membrane,
in a degree inconsistent with the purpose which it
was assigned to execute. The only remaining ex-
pedient, and that for which the eustachian tube
serves, is to open to this cavity a communication

^^ It will be shown in the Appendix, that the fine apparatus con-
sisting of these bones, with their four minute muscles attached to
them, is not necessary to the sensation coming through the bones
of the head, as here described by our author: it is provided for the
more delicate vibrations of the erastic atmosphere, and is not foimd
except in animals that breathe the air. It will be also found, that
whilst these bones move with the slightest impulse of sound, they
regulate the impression, and protect the nerve.

5

50 NATURAL THEOLOGY.

with the external air. In one word, it exactly
answers the purpose of the hole in a drum.

The membrana tympani itself, likewise, deserves
all the examination which can be made of it. It
is not found in the ears of fish ; which furnishes
an additional proof of what indeed is indicated by
every thing about it, that it is appropriated to the
action of air, or of an elastic medium. It bears an
obvious resemblance to the pelt or head of a drum.

[This figure represents the membrane of the tj-mpanum of a
larger size than natural. It is represented as tucked in by the
handle of the malleus. The description of Sir Everard Home, re-
ferred to in the text, is altogether fanciful. There is no proof that
these fibres are muscular : they are drawn tight by the small mus-
cle attached to the matteus called tensor tympani; and it would ap-
pear that these cords are necessary to produce that variety of mo-
tion in the membrane suited to all the variety of sounds which are
conveyed through it to the seat of the sense. Sir Everard played
to the elephant on the piano-forte. That the animal took some
notice of the extraordinary sound cannot surprise us; but the in-
ferences drawn by Sir Everard were equally ingenious and ground-
less. He supposed that the musical ear was owing to the mem-
brane of the tympanum.]

NATURAL THEOLOGY. 51

from which it takes its name. It resembles also
a drum-head in this principal property, that its
use depends upon its tension. Tension is the state
essential to it. Now we know that, in a drum,
the pelt is carried over a hoop, and braced as oc-
casion requires, by the means of strings attached
to its circumference. In the membrane of the ear,
the same purpose is provided for, more simply, but
not less mechanically nor less successfully, by a
different expedient, viz. by the end of a bone (the
handle of the malleus) pressing upon its centre.
It is only in very large animals that the texture of
this membrane can be discerned. In the Philoso-
phical Transactions for the year 1800 (vol. i.) Mr.
Everard Home has given some curious observa-
tions upon the ear, and the drum of the ear of an
elephant. He discovered in it what he calls a ra-
diated mxuscle — that is, straight muscular fibres
passing along the membrane from the circum-
ference to the centre — from the bony rim which
surrounds it towards the handle of the malleus, to
which the central part is attached. This muscle
he supposes to be designed to bring the membrane
into unison with different sounds ; but then he also
discovered, that this muscle itself cannot act, un-
less the membrane be drawn to a stretch, and kept
in a due state of tightness, by what may be called
a foreign force — viz. the action of the muscles of
the malleus. Supposing his explanation of the use
of the parts to be just, our author is well founded
in the reflection which he makes upon it — " that

52 NATURAL THEOLOGY,

this mode of adapting the ear to different sounds,
is one of the most beautiful applications of muscles
in the body ; the mechanism is so simple, and the
variety of effects so great, "

In another volume of the Transactions above re-
ferred to, and of the same year, tw^o most curious
cases are related, of persons who retained the
sense of hearing, not in a perfect but in a very
considerable degree, notwitstanding the almost
total loss of the membrane we have been de-
scribing. In one of these cases, the use here as-
signed to that membrane, of modifying the impres-
sions of sound by change of tension, was attempted
to be supplied by straining the muscles of the out-
ward ear. " The external ear, " we are told, " had
acquired a distinct motion upward and backward,
which w^as observable whenever the patient lis-
tened to any thing which he did not distinctly
hear ; when he was addressed in a whisper, the
ear was seen immediately to move ; when the tone
of voice was louder, it then remained altogether
motionless. "

It appears probable, from both these cases, that
a collateral if not principal use of the membrane
is to cover and protect the barrel of the ear which
lies behind it. Both the patients suffered from
cold : one, " a great increase of deafness from catch-
ing cold ; " the other, " very considerable pain from
exposure to a stream of cold air. " Bad effects
therefore followed from this cavity being left open
to the external air; yet, had the Author of Nature

NATURAL THEOLOGY. 53

shut it up by any other cover than what was ca-
pable, by its texture, of receiving vibrations from
sound, and, by its connexion with the interior
parts, of transmitting those vibrations to the brain,
the use of the organ, so far as we can judge, must
have been entirely obstructed.

5*

54 NATURAL THEOLOGY,

CHAPTER IV.

ON THE SUCCESSION OF PLANTS AND ANIMALS.

The generation of the animal no more accounts
for the contrivance of the eye or ear, than, upon
Che supposition stated in the preceding chapter, the
production of a watch by the motion and mecha-
nism of a former watch, would account for the
skill and attention evidenced in the watch so pro-
duced — than it would account for the disposition
of the wheels, the catching of their teeth, the re-
lation of the several parts of the works to one
another, and to their common end ; for the suitable-
ness of their forms and places to their offices, for
their connexion, their operation, and the useful
result of that operation. I do insist most strenu-
ously upon the correctness of this comparison ;
that it holds as to every mode of specific propa-
gation ; and that whatever was true of the watch,
under the hypothesis above mentioned, is true of
plants and animals.

I. To begin with the fructification of plants.
Can it be doubted but that the seed contains a
particular organization ? Whether a latent plan-
tule with the means of temporary nutrition, or
whatever else it be, it encloses an organization

NATURAL THEOLOGY. 55

suited to the germination of a new plant. Has
the plant which produced the seed any thing more
to do with that organization, than the watch would
have had to do with the structure of the watch
which w as produced in the course of its mechani-
cal movement ? I mean — Has it any thing at
all to do with the contrivance ? The maker and
contriver of one watch, when he inserted within
it a mechanism suited to the production of another
w^atch, was, in truth, the maker and contriver of
that other watch. All the properties of the new
watch were to be referred to his agency : the de-
sign manifested in it, to his intention : the art, to
him as the artist ; the collocation of each part, to
his placing : the action, effect, and use, to his coun-
sel, intelligence, and workmanship. In producing
it by the intervention of a former watch, he was
only working by one set of tools instead of another.
So it is with the plant, and the seed produced by
it. Can any distinction be assigned between the
two cases ; between the producing watch, and the
producing plant ; both passive unconscious substan-
ces ; both, by the organization which was given
to them, producing their like, without understand-
ing or design ; both, that is, instruments ?

n. From plants we may proceed to oviparous
animals : from seeds to eggs. Now I say, that
the bird has the same concern in the formation of
the egg which she lays, as the plant has in that of
the seed which it drops; and no other nor greater.
The internal constitution of the egg is as much a

56 NATURAL THEOLOGY.

secret to the hen as if the hen were inanimate.
Her will cannot alter it, or change a single feather
of the chick. She can neither foresee nor deter-
mine of which sex her brood shall be, or how
many of either ; yet the thing produced shall be,
from the first, very different in its make according
to the sex which it bears. So far, therefore, from
adapting the means, she is not beforehand apprized
of the effect. If there be concealed within that
smooth shell a provision and a preparation for the
production and nourishment of a new animal, they
are not of her providing or preparing ; if there be
contrivance, it is none of hers. Although, there-
fore, there be the difference of life and perceptivity
between the animal and plant, it is a difference
which enters not into the account ; — it is a foreign
circumstance ; it is a difference of properties not
employed. The animal function and the vegetable
function are alike destitute of any design which
can operate upon the form of the thing produced.
The plant has no design in producing the seed —
no comprehension of the nature or use of what it
produces : the bird, with respect to its egg, is not
above the plant with respect to its seed. Neither
the one nor the other bears that sort of relation
to what proceeds from them which a joiner does
to the chair which he makes. Now a cause which
bears this relation to the effect, is what we want,
in order to account for the suitableness of means
to an end — the fitness and fitting of one thing to

NATURAL THEOLOGY. 57

another ; and this cause the parent plant or animal
does not supply.

It is further observable concerning the propa-
gation of plants and animals, that the apparatus
employed exhibits no resemblance to the thing
produced ; in this respect, holding an analogy with
instruments and tools of art. The filaments, an-
therae, and stigmata of flowers, bear no more re-
semblance to the young plant, or even to the seed
which is formed by their intervention, than a
chisel or a plane does to a table or chair. What
then are the filaments, antheroe, and stigmata of
plants but instruments, strictly so called ?

III. We may advance from animals which bring
forth eggs to animals which bring forth their
young alive ; and of this latter class, from the
lowest to the highest ; from irrational to rational
life, from brutes to the human species ; without
perceiving, as we proceed, any alteration what-
ever in the terms of the comparison. The rational
animal does not produce its offspring with more
certainty or success than the irrational animal : a
man than a quadruped, a quadruped than a bird ;
nor (for we may follow the gradation through its
whole scale) a bird than a plant ; nor a plant than a
watch, a piece of dead mechanism, would do,
upon the supposition which has already so often
been repeated. Rationality, therefore, has nothing
to do in the business. If an account must be given
of the contrivance which we observe ; if it be de-
manded, whence arose either the contrivance by

58 NATURAL THEOLOGY.

which the young animal is produced, or the con-
trivance manifested in the young animal itself, it
is not from the reason of the parent that any such
account can be drawn. He is the cause of his
offspring, in the same sense as that in which a gar-
dener is the cause of the tulip which grows upon
his parterre, and in no other. We admire the
flower ; we examine the plant ; we perceive the
conduciveness of many of its parts to their end
and office : we observe a provision for its nourish-
ment, growth, protection, and fecundity ; but we
never think of the gardener in all this. We attri-
bute nothing of this to his agency ; yet it may still
be true, that without the gardener we should not
have had the tulip. Just so it is with the succes-
sion of animals, even of the highest order. For
the contrivance discovered in the structure of the
thing produced, we want a contriver. The parent
is not that contriver : his consciousness decides
that question. He is in total ignorance why that
which is produced took its present form rather
than any other. It is for him only to be astonished
by the effect. We can no more look therefore to
the mtelligence of the parent animal for what we
are in search of — a cause of relation, and of sub-
serviency of parts to their use, which relation and
subserviency we see in the procreated body —
than we can refer the internal conformation of an
acorn to the intelligence of the oak from which it
dropped, or the structure of the watch to the in-
telligence of the watch which produced it : there

NATURAL THEOLOGY. 59

being no difference, as far as argument is concern-
ed, between an intelligence which is not exerted,
and an intelligence which does not exist.'*^

1^ When we have, in some measure, comprehended the system
of an animal body, how the different organs are related to each
other, and how the whole exists through a mutual influence of its
parts, the wonder is renewed how another creature should grow
out of that, wluch, as far as we have seen, has no tendency to
multiply itself. Authors who treat of reproduction, even to the
ver}' last, affirm, that with the germ of life in all organized struc-
tures are conjoined the seeds of decay and of death : they tell us
that the powers of life are finite, and that the time must come
when they shall be expended. Now there are no seeds of decay ;
and altlaough, according to the law of animal existence, the indi-
vidual perishes, it is incorrect to say that it is the result of the
exhaustion of the powers of vitality, or the deterioration of the
material which enters into its composition. We gain nothing by
adapting the language of one science to explain another : it is of
no advantage, in treating of life and death, to adopt a chemical
nomenclature. The term of life in every creature, from the ele-
phant to the ephemeral fly, has its limit ; but it is wrong to say
that it is by the defect of the material, or of the energy of life ; it
is a better philosophy to admit that it is in accordance with the
system which the Deity has ordained.

Life, in the sense in which it is used here, is continued in the
germ that rises from the parent ; since out of the old body, that is
described as a deteriorated and useless material, a new creation is
produced, it suffices to show that there is no necessary decay from
the material itself A leaf or twig of an old tree will strike root
into the ground, and vegetate and exhibit youthful vigour. So will
the fresh water polypus furnish a portion which, being cut off,
will grow with a perfect resemblance to the original stock. In
the reproduction of the higher and the more complex organized
bodies there is much that is obscure ; but in the simpler, and, as
it is termed, the lower examples — vegetables, zoophytes, and in-
fusory animals — we have abundant proofs that the result does

60 NATURAL THEOLOGY.

not proceed from the exhausted or deteriorated nature of the
material.

Amongst the infusoria, the animals called Monads, of Avhich
there is a great variety, exhibit very curious phenomena. They
are of a globular form, and this globe is seen first to contract and
then divide, each becoming a distinct animal. And something
like this may be done artificially by the division of the fresh- water
polypus, or hydra ; and what is deficient in the divided portion is
supplied by a new growth, be it head or tail. The thing, however,
is not so remarkable, if we consider that those lower animals have
abundant resemblance to vegetables ; and that in cutting off por-
tions the experimenter is cutting off buds. These buds or tuber-
cles, if left to undergo their natural changes, acquire independent
motion, produce tcntacula, or feelers, to procure food, and, thus
prepared to be independent, fall off from the parent stock.

The microscope exhibits another instance in the Volvox. It is
a transparent globule, within which smaller globules may be seen ;
and when matured the parent bursts, discloses the offspring, and
dies.

In all these examples, we see that there is no reason to speak
of exhausted or deteriorated matter, or debility in the powers of
life.

So in the higher and the more complex animals we find one set
of organs decaying and another rising into existence. Contem-
plating the one, we would say that the powers were decaying ;
contemplating the other, that they were fresh and vigorous. We
must come to the conclusion, then, that the growth of parts, or
the period of their developement, the decay of the animal, or of
the parts of the animal is by an ordinance which is very inaccu-
rately expressed by the terms exhaustion of life, or imperfection
of the material. Imperfection, in truth, is a relative term, and
means failure or insufficiency towards the accomplishment of
certain purposes. If the object in view were the duration of ani-
mal bodies for a great length of time, we might be justified in say-
in'' that the materials they are made of are imperfect ; but this is
clearly not the design with which they are formed.

NATURAL THEOLOGY.

61

CHAPTER V.

APPLICATION OP THE ARGUMENT CONTINUED.

Every observation which was made in our first
chapter concerning the watch, may be repeated
with strict propriety concerning the eye ; concern-
ing animals ; concerning plants ; concerning, in-
deed, all the organized parts of the works of na-
ture. As,

I. When we are inquiring simply after the ex-
istence of an intelligent Creator, imperfection, in-
accuracy, liability to disorder, occasional irregu-
larities, may subsist in a considerable degree
without inducing any doubt into the question: just
as a watch may frequently go wrong, seldom per-
haps exactly right, may be faulty in some parts,
defective in some, without the smallest ground of
suspicion from thence arising that it was not a
watch, not made, or not made for the purpose as-
cribed to it. When faults are pointed out, and
when a question is started concerning the skill of
the artist, or dexterity with which the work is
executed, then, indeed, in order to defend these
qualities from accusation, we must be able, either
to expose some intractableness and imperfection
in the materials, or point out some invincible diffi-

6

62 NATURAL THEOLOGY,

culty in the execution, into which imperfection
and difficulty the matter of complaint may be re-
solved ; or, if we cannot do this, we must adduce
such specimens of consummate art and contrivance
proceeding from the same hand as may convince
the inquirer of the existence, in the case before
him, of impediments like those which we have
mentioned, although, what from the nature of
the case is very hkely to happen, they be unknown
and unperceived by him. This we must do in
order to vindicate the artist's skill, or at least the
perfection of it ; as w^e must also judge of his in-
tention, and of the provisions employed in fulfilling
that intention, not from an instance in which they
fail, but from the great plurality of instances in
which they succeed. But, after all, tliese are dif-
ferent questions from the question of the artist's
existence ; or, which is the same, whether the
thing before us be a work of art or not ; and the
questions ought always to be kept separate in the
mind. So likewise it is in the works of nature.
Irregularities and imperfections are of little or no
weight in the consideration, when that considera-
tion relates simply to the existence of a Creator,
When the argument respects his attributes, they
are of weight ; but are then to be taken in con-
junction (the attention is not to rest upon them,
but they are to be taken in conjunction) with the
unexceptionable evidences which we possess of
skill, power, and benevolence, displayed in other
instances ; which evidences may, in strength, num-

NATURAL THEOLOGY. 63

ber, and variety, be such, and may so overpower
apparent blemishes, as to induce us, upon the most
reasonable ground, to believe that these last ought
to be referred to some cause, though we be ignorant
of it, other than defect of knowledge or of benev-
olence in the author.

II. There may be also parts of plants and ani-
mals, as there were supposed to be of the watch, of
which, in some instances the operation, in others
the use, is unknown. These form different cases:
for the operation may be unknown, yet the use be
certain. Thus it is with the lungs of animals. It
does not, I think, appear, that we are acquainted
with the action of the air upon the blood, or in
what manner that action is conmiunicated by the
lungs ; yet we find that a very short suspension of
their office destroys the life of the animal.*"^ In
this case, therefore, we may be said to know the
use, nay, we experience the necessity, of the organ,
though we be ignorant of its operation. Nearly
the same thing may be observed of what is called
the lymphatic system. We suffer grievous incon-
veniences from its disorder, without being inform-
ed of the office which it sustains in the economy

^'' Undoubtedly the exposure of the blood to the atmosphere, in
the circulation through the lungs, and the throwing off of carbon,
are essential to life. But the pain and alarm excited when there
is danger of suffocation are not so much a direct consequence of
the interruption of the function, as an instance of the manner in
which the sensibility is bestowed to guard the important actions
of life.

64 NATURAL THEOLOGY.

of our bodies. There may possibly also be some
few examples of the second class, in which not
only the operation is unknown, but in which ex-
periments may seem to prove that the part is not
necessary ; or may leave a doubt how far it is
even useful to the plant or animal in which it is
found. This is said to be the case with the spleen,
which has been extracted from dogs without any
sensible injury to their vital functions. Instances
of the former kind, namely, in which we cannot
explain the operation, may be numerous ; for they
will be so in proportion to our ignorance. They
will be more or fewer to different persons, and in
different stages of science. Every improvement
of knowledge diminishes their number. There is
hardly, perhaps, a year passes that does not, in the
works of nature, bring some operation, or some
mode of operation, to light, which was before un-
discovered,— probably unsuspected. Instances
of the second kind, namely, where the part ap-
pears to be totally useless, I believe to be ex-
tremely rare ; compared with the number of those
of which the use is evident, they are beneath any
assignable proportion, and perhaps have been
never submitted to a trial and examination suffi-
ciently accurate, long enough continued, or often
enough repeated. No accounts which I have seen
are satisfactory. The mutilated animal may live
and grow fat (as was the case of the dog deprived
of its spleen,) yet may be defective in some other
of its functions, which, whether they can all, or in

NATURAL THEOLOGY. 65

what degree of vigour and perfection, be perform-
ed, or how long preserved without the extirpated
organ, does not seem to be ascertained by experi-
ment. But to this case, even were it fully made
out, may be applied the consideration which we
suggested concerning the watch, viz., that these
superfluous parts do not negative the reasoning
which we instituted concerning those parts which
are useful, and of which we know the use; the
indication of contrivance, with respect to them,
remains as it was before/^

III. One atheistic way of replying to our obser-
vations upon the works of nature, and to the proofs
of a Deity which we think that we perceive in them,
is to lell us, that all which we see must necessarily
have had some form, and that it might as well be

'3 In the liigher animals there is a great complication of organs^
Yet, in the lower animals, the functions of digestion, respiration,
assimilation, secretion, and growth proceed by means of an ap-
paratus comparatively simple. We must not be surprised, then,
that certain parts may be removed from the higher animals with-
out destroying life. But this does not imply that those parts are
useless, since they are structures superadded for the finer adjust-
ment of the different functions one to the other, belonging to a
higher condition of the economy.

With regard to parts which are thus called useless, we must
remember that the varieties of created animals belong to one
type. As we have just said, the essential functions are the same
in all ; and there is much of the structure common to all : when
an animal of a particular class has its organization adjusted to a
certain condition of existence, we may see the rudiments of parts
which, not being in action, are imperfect, and we must look to the
individuals of another species or variety to discover them in their
full developement.

6*

66 NATURAL THEOLOGY.

its present form as any other. Let us now apply
this answer to the eye, as we did before to the
watch. Something or other must have occupied
that place in the animal's head ; must have filled
up, we will say, that socket : we will say, also,
that it must have been of that sort of substance
which we call animal substance, as flesh, bone,
membrane, or cartilage, &:c. But that it should
have been an eye, knowing as we do what an eye
comprehends, — viz. that it should have consisted,
first, of a series of transparent lenses (very differ-
ent, by-the-by, even in their substance, from the
opaque materials of which the rest of the body is,
in general at least, composed ; and with which the
whole of its surface, this single portion of it ex-
cepted, is covered :) secondly, of a black cloth or
canvass (the only membrane of the body which is
black,) spread out behind these lenses, so as to re-
ceive the image formed by pencils of light trans-
mitted through them ; and placed at the precise
geometrical distance, at which, and at which alone,
a distinct image could be formed, namely, at the
concourse of the refracted rays: thirdly, of a large
nerve communicating between this membrane and
the brain ; without which, the action of light upon
the membrane, however modified by the organ,
would be lost to the purposes of sensation : — that
this fortunate conformation of parts should have
been the lot, not of one individual out of many
thousand individuals, like the great prize in a lot-
tery, or like some singularity in nature, but the

NATURAL THEOLOGY. C7

liappy chance of a whole species : nor of one spe-
cies out of many thousand species, with which we
are acquainted, but of by far the greatest number
of all that exist ; and that under varieties, not ca-
sual or capricious, but bearing marks of being
suited to their respective exigencies : — that all
this should have taken place, merely because some-
thing must have occupied these points on every
animal's forehead ; — or, that all this should be
thought to be accounted for by the short answer,
" that whatever was there must have had some
form or other, " is too absurd to be made more so
by any augmentation. We are not contented with
this answer ; we find no satisfaction in it, by way
of accounting for appearances of organization far
short of those of the eye, such as we observe in
fossil shells, petrified bones, or other substances
which bear the vestiges of animal or vegetable
recrements, but which, either in respect to utility,
or of the situation in which they are discovered^
may seem accidental enough. It is no way of
accounting even for these things, to say, that the
stone, for instance, which is shown to us (suppos-
ing the question to be concerning a petrification,)
must have contained some internal conformation
or other. Nor does it mend the answer to add,
with respect to the singularity of the conforma-
tion, that after the event, it is no longer to be com-
puted what the chances were against it. This is
always to be computed when the question is, whe-
ther a useful or imitative conformation be the pro-

68 NATURAL THEOLOGY.

duce of chance or not : I desire no greater cer-
tainty in reasoning than that by which chance is
excluded from the present disposition of the natu-
ral world. Universal experience is against it.
What does chance ever do for us ? In the human
body, for instance, chance, i. e. the operation of
causes without design, may produce a wen, a wart,
a mole, a pimple, but never an eye. Amongst in-
animate substances, a clod, a pebble, a liquid drop
might be ; but never was a watch, a telescope, an
organized body of any kind, answering a valuable
purpose by a complicated mechanism, the effect
of chance.^^ In no assignable instance hath such
a thing existed without intention somewhere.

19 There is great inaccuracy, and indeed a very unpliilosophical
and superficial view of the subject in these observations upon
" chancey Chance is merely an abridged fonn of expressing our
ignorance of the cause or preceding event to which any given
event may be traced ; and nothing can be more inaccurate, or in-
deed more productive of serious errors in this very branch of
science, than to speak of chance as a substantive thing or power.
To take the most obvious instance : we say, in common parlance,
that the dice being shaken together, it is a matter of chance what
faces they will turn up ; but, if we could accurately observe their
position in the box before the shaking, the direction of the force
applied, its quantity, the number of turns of the box, and the curve
in wliich the motion was made, the manner of stopping the motion
and the line in which the dice were thrown out, the faces turned
up would be a matter of certain prediction, after a sufficient num-
ber of experiments had been made to correct the theory. It is only
because we take no heed of all these things that we are ignorant
what will be the event ; and the darkness in which we are respect-
ing the circumstances which regulate it, is called by the name of
chance. Nor is it correct to say, that this or anything else is done

NATURAL THEOLOGY. 69

IV. There is another answer which has the
same eflect as the resolving of things into chance ;
which answer would persuade us to believe, that
the eye, the animal to which it belongs, every other
animal, every plant, indeed every organized body
which we see, are only so many out of the possi-
ble varieties and combinations of being which the
lapse of infinite ages has brought into existence ;
that the present world is the relic of that variety ;
millions of other bodily forms and other species
having perished, being, by the defect of their con-
stitution, incapable of preservation, or of continu-
ance by generation. Now there is no foundation
whatever for this conjecture in any thing which
we obsen-e in the works of nature ; no such expe-

without design. All we can mean by the expression is, that our
design stops short at a certain point, and leaves the laws of nature
to guide the rest of the operation. But such a position is mani-
festly quite inapplicable to the operations of nature.

Equally inaccurate is it, if not more so, to speak of a wen or a
pimple, &c., as the result of any cause in the least degree different
from that which produced the eye. These are possibly always,
certainly sometimes, diseases ; but they are the result of contri-
vance as clearly as the eye itself. The functions of the animal
system, though acting in an unusual manner, yet acting according
to rule, produce these phenomena. Indeed one of them, a pimple,
is, in part at least, the result of the provision made for restoring
the interrupted continuity of the skin, by a slight suppm-ation from
which the granulation, or production of new animal fibre, takes
place. The like remark applies to the cases of a clod, pebble, or
liquid drop, also put in this passage. We have already adverted
to the two first in a former note ; the formation of a drop is in
truth one of the phenomena of gravitation, and a very remarkable
one.

70 NATURAL THEOLOGY.

riments are going on at present ; no such energy
operates as that which is here supposed, and which
should be constantly pushing into existence new
varieties of beings. Nor are there any appearances
to support an opinion, that every possible combi-
nation of vegetable or animal structure has for-
merly been tried. Multitudes of conformations,
both of vegetables and animals, may be conceived
capable of existence and succession, which yet do
not exist. Perhaps almost as many forms of plants
might have been found in the fields as figures of
plants can be delineated upon paper. A countless
variety of animals might have existed which do
not exist. Upon the supposition here stated, we
should see unicorns and mermaids, sylphs and cen-
taurs, the fancies of painters, and the fables of
poets, realized by examples. Or, if it be alleged
that these may transgress the bounds of possible
life and propagation, we might at least have na-
tions of human beings without nails upon their
fingers, with more or fewer fingers and toes than
ten, some with one eye, others with one ear, with
one nostril, or without the sense of smelling at all.
All these, and a thousand other imaginable varie-
ties, might live and propagate. We may modify
any one species many different ways, all consistent
with life, and with the actions necessary to pre-
servation, although affording different degrees of
convenicncy and enjoyment to the animal. And
if we carry these modifications through the differ-
ent species which are known to subsist, their num-

NATURAL THEOLOGY. 71

ber would be incalculable. No reason can be
given why, if these deperdits ever existed, they
have now disappeared. Yet, if all possible exist-
ences have been tried, they must have formed part
of the catalogue.^"

But moreover, the division of organized sub-
stances into animals and vegetables, and the distri-
bution and sub-distribution of each into genera and
species, which distribution is not an arbitrary act
of the mind, but founded in the order which pre-
vails in external nature, appear to me to contradict
the supposition of the present world being the re-
mains of an indefinite variety of existences ; of a

20 No doubt men in different ages have asserted the possibihty
of all we see being made by chance ; but we are not uncharitable
when we say that no man ever believed it. It is easily shown,
that, of all the varieties of fabulous animals which have been bred
in the fertile imagination of the poet, not one could have lived.
They want that relation and balance of the different organs, that
provision running through the whole texture of the frame of the
animal, which we see in the natural productions. The sphinx has
wings, but no constitution of body to give these strength. The
griffin, with its hooked bill, has no feathers to prin, and no substi-
tute for teeth. The centaur has the body of the horse, but no
mouth to gather appropriate food.

We may conclude, then, that these products of the imagination
are altogether abortive, and only tend to prove how exact the rela-.
tion must be of all the parts, and especially of the vital organs of
an animal, in order that it may live.

As to the second position, that the animals which exist are the
happy results of chance when thousands have perished by imper-
fection, the supposition is contradicted by the perfect and harmo-
nious chain of beings forming the animal kingdom, in which there
is no link interrupted, no interval implying the loss of any species.

72 NATURAL THEOLOGY.

variety wliich rejects all plan. The hypothesis
teaches, that every possible variety of being hath,
at one time or other, found its way into existence
(by what cause or in what manner is not said,) and
that those which were badly formed perished ; but
how or why those which survived should be cast,
as we see that plants and animals are cast, into regu-
lar classes, the hypothesis does not explain; or rather
the hypothesis is inconsistent with this phenomenon.
The hypothesis, indeed, is hardly deserving of
the consideration which we have given to it. What
should we think of a man who, because we had
never ourselves seen watches, telescopes, stocking-
mills, steam-engines, &c.,made, knew not how they
were made, nor could prove by testimony when
they were made, or by whom, would have us be-
lieve that these machines, instead of deriving their
curious structures from the thought and design of
their inventors and contrivers, in truth derive them
from no other origin than this : viz., that a mass of
metals and other materials having run, when melt-
ed, into all possible figures, and combined them-
selves in all possible forms, and shapes, and pro-
portions, these things which we see are what were
left from the accident, as best worth preserving,
and, as such, are become the remaining stock of a
magazine, which, at one time or other, has by this
means contained everv' mechanism, useful and use-
less, convenient and inconvenient, into which such
like materials could be thrown ? I cannot distin-
guish the h}7)othesis, as applied to the works of

NATURAL THEOLOGY. 73

nature, from this solution, which no one would ac-
cept as applied to a collection of machines.

V. To the marks of contrivance discoverable in
animal bodies, and to the argument deduced from
them in proof of design and of a designing Creator,
this turn is sometimes attempted to be given, name-
ly, that the parts were not intended for the use, but
that the use arose out of the parts. This distinc-
tion is intelligible. A cabinet-maker rubs his ma-
hogony with fish-skin ; yet it would be too much to
assert that the skin of the dog-fish was made rough
and granulated on purpose for the polishing of wood,
and the use of cabinet-makers. Therefore the dis-
tinction is intelligible. But I think that there is
very little place for it in the works of nature. When
roundly and generally affirmed of them, as it hath
sometimes been, it amounts to such another stretch
of assertion as it would be to say, that all the im-
plements of the cabinet-maker's workshop, as well
as his fish-skin, were substances accidentally con-
figurated, which he had picked up and converted
to his use ; that his adzes, saws, planes, and gimlets,
were not made, as we suppose, to hew, cut, smooth,
shape out, or bore wood with ; but that, these things
being made, no matter with what design, or whether
with any, the cabinet-maker perceived that they
were applicable to his purpose, and turned them
to account.

But, again. So far as this solution is attempted
to be applied to those parts of animals the action
of which does not depend upon the will of the ani-

7

74 NATURAL THEOLOGY.

mal, it is fraught with still more evident absurdity.
Is it possible to believe that the eye was formed
without any regard to vision ; that it was the ani-
mal itself which found out that, though formed with
no such intention, it would serve to see with ; and
that the use of the eye as an organ of sight resulted
from this discovery, and the animal's application of
it ? The same question may be asked of the ear ;
the same of all the senses. None of the senses fun-
damentally depend upon the election of the ani-
mal ; consequently neither upon his sagacity nor
his experience. It is the impression which objects
make upon them that constitutes their use. Under
that impression he is passive. He may bring ob-
jects to the sense, or within its reach ; he may se-
lect these objects ; but over the impression itself
he has no power, or very little ; and that properly
is the sense.

Secondly; there are many parts* of animal bodies
which seem to depend upon the will of the animal
in a greater degree than the senses do, and yet w4th
respect to which this solution is equally unsatisfac-
tory. If we apply the solution to the human body,
for instance, it forms itself into questions upon
which no reasonable mind can doubt ; such as,
whether the teeth w^ere made expressly for the
mastication of food, the feet for walking, the hands
for holding ? or whether, these things being as they
are, being in fact in the animal's possession, his own
ingenuity taught him that they were convertible to

NATURAL THEOLOGY. 75

these purposes, though no such purposes were con-
templated in their formation?

All that there is of the appearance of reason in
this way of considering the subject is, that, in some
cases, the organization seems to determine the
habits of the animal, and its choice to a particular
mode of hfe ; which, in a certain sense, may be
called " the use arising out of the part."^^ Now, to
all the instances in which there is any place for
this suggestion, it may be replied, that the organi-
zation determines the animal to habits beneficial
and salutary to itself; and that this effect would
not be seen so regularly to follow, if the several
organizations did not bear a concerted and con-
trived relation to the substance by which the ani-
mal was surrounded. They would, otherwise, be

^^ We deceive ourselves in this matter : the dexterity which use
gives, makes us apt to beUeve that the faculty is gained through
the accidental possession of the instrument. But the difficulty is
removed, if we make due comparison between man and other ani-
mals. In the former, it is intended that the faculty should be
gradually developed ; and the slowness with which perfection is
attained leaves us in some doubt of the relation between the effort
and the instrument used. But in the latter, all obscurity is removed :
their propensities and instincts, and the use of their instruments
are so perfect from the beginning, as to admit of no improvement.
The fly-catcher requires no experience to adjust his eye, no second
effort of his bill to correct the first. Whether it be the horn, or the
tooth, or the sting, the disposition is given with it, and the mode
of its action is prescribed. The spider weaves his web without
improvement, or room for improvement. This subject is treated
at some length in the " Bridgewater Treatise on the Hand," where
the question is discussed, whether or not the possession of the hand
is the source of man's superiority.

76 NATURAL THEOLOGY.

capacities without objects ; powers without em-
ployment. The web-foot determines, you say, the
duck to swim ; but what would that avail if there
were no water to swim in. The strong hooked
bill and sharp talons of one species of bird deter-
mine it to prey upon animals ; the soft straight bill
and weak claws of another species determine it to
pick up seeds: but neither determination could take
effect in providing for the sustenance of the birds,
if animal bodies and vegetable seeds did not lie
within their reach. The peculiar conformation of
the bill and tongue and claws of the woodpecker
determines that bird to search for his food amongst
the insects lodged behind the bark or in the wood
of decayed trees; but what would this profit him
if there were no trees, no decayed trees, no in-
sects lodged under their bark, or in their trunk ?
The proboscis with which the bee is furnished de-
termines him to seek for honey : but what would
that signify if flowers supplied none ? Faculties
thrown down upon animals at random, and with-
out reference to the objects amidst which they are
placed, would not produce to them the services and
benefits which we see : and if there be that refer-
ence, then there is intention.

Lastly ; the solution fails entirely when applied
to plants. The parts of plants answer their uses
\vithout any concurrence from the will or choice of
the plant.

VI. Others have chosen to refer everything to
a i^rinciple of order in nature. A principle of

NATURAL THEOLOGY. 77

order is the word ; but what is meant by a princi-
ple of order as different from an intelligent Creator,
has not been explained either by definition or exam-
ple ; and, without such explanation, it should seem
to be a mere substitution of words for reasons,
names for causes. Order itself is only the adap-
tation of means to an end : a principle of order,
therefore, can only signify the mind and intention
which so adapts them. Or, were it capable of
being explained in any other sense, is there any
experince, any analogy, to sustain it ? Was a watch
ever produced by a principle of order? and why
might not a watch be so produced as well as an
eye?

Furthermore, a principle of order, acting blind-
ly and without choice, is negatived by the obser-
vation that order is not universal ; which it would
be if it issued from a constant and necessary prin-
ciple : nor indiscriminate, which it would be if it
issued from an unintelligent principle. Where
order is wanted, there we find it : where order is
not wanted, i. e, where, if it prevailed, it would be
useless, there we do not find it. In the structure
of the eye (for we adhere to our example,) in the
figure and position of its several parts, the most
exact order is maintained. In the forms of rocks
and mountains, in the lines which bound the coasts
of continents and islands, in the shape of bays and
promontories, no order whatever is perceived, be-
cause it would have been superfluous. No useful

purpose would have arisen from moulding rocks

7*

78 NATURAL THEOLOGY.

and mountains into regular solids, bounding the
channel of the ocean by geometrical curves ; or
from the map of the world resembling a table
of diagrams in Euclid's Elements or Simpson's
Conic Sections.

VII. Lastly ; the confidence which we place in
our observations upon the works of nature, in the
marks which we discover of contrivance, choice,
and design, and in our reasoning upon the proofs
afforded us, ought not to be shaken, p.s it is some-
times attempted to be done, by bringing forward
to our view our own ignorance, or rather the ge-
neral imperfection of our knowledge of nature.
Nor, in many cases, ought this consideration to af-
fect us, even when it respects some parts of the
subject immediately under our notice. True for-
titude of understanding consists in not suffering
what we know to be disturbed by what we do
not know. If we perceive a useful end, and means
adapted to that end, we perceive enough for our
conclusion. If these things be clear, no matter
what is obscure. The argument is finished. For
instance : if the utility of vision to the animal which
enjoys it, and the adaptation of the eye to this of-
fice, be evident and certain (and I can mention
nothing which is more so,) ought it to prejudice
the inference which we draw from these premises,
that we cannot explain the use of the spleen?
Nay, more : if there be parts of the eye, viz. the
cornea, the crystalline, the retina, in their sub-
stance, figure, and position, manifestly suited to the

Natural theology. 79

formation of an image by the refraction of rays of
light, at least as manifestly as the glasses and tubes
of a dioptric telescope are suited to that purpose,
it concerns not the proof which these afford of de-
sign, and of a designer, that there may perhaps
be other parts, certain muscles, for instance, or
nerves in the same eye, of the agency or effect of
which we can give no account, any more than we
should be inclined to doubt, or ought to doubt, about
the construction of a telescope, viz. for what purpose
it was constructed, or whether it were constructed
at all, because there belonged to it certain screws
and pins, the use or action of which we did not
comprehend. I take it to be a general way of in-
fusing doubts and scruples into the mind, to recur
to its own ignorance, its own imbecility : to tell us
that upon these subjects we know little ; that little
imperfectly ; or rather, that we know nothing pro-
perly about the matter. These suggestions so fall
in with our consciousness as sometimes to pro-
duce a general distrust of our faculties and our con-
clusions. But this is an unfounded jealousy. The un-
certainty of one thing does not necessarily affect
the certainty of another thing. Our ignorance of
many points need not suspend our assurance of a few.
Before we yield, in any particular instance, to the
skepticism which this sort of insinuation would in-
duce, we ought accurately to ascertain whether our
ignorance or doubt concern those precise points
upon which our conclusion rests. Other points are
nothing. Our ignorance of other points may be of

80 NATURAL THEOLOGY.

no consequence to these, though they be points, in
various respects, of great importance. A just rea-
soner removes from his consideration, not only what
he knows, but what he does not know, touching
matters not strictly connected with his argument,
i. e. not forming the very steps of his deduction :
beyond these, his knowledge and his ignorance are
alike relative.

NATURAL THEOLOGY.

81

CHAPTER VI.

THE ARGUMENT CUMULATIVE.

Were there no example in the world of con-
trivance except that of the eye, it would be alone
sufficient to support the conclusion which we draw
from it, as to the necessity of an intelligent Cre-
ator. It could never be got rid of; because it
could not be accounted for by any other supposi-
tion, which did not contradict all the principles
we possess of knowledge ; the principles accord-
ing to which things do, as often as they can be
brought to the test of experience, turn out to be
true or false. Its coats and humours, constructed

[The figure is introduced to remind the reader of the fine adjust-
ment of the eye; a subject explained in the Appendix: — A, B,
is the object, and the hues represent the hght reflected from it into
the eye. On the surface of the cornea, which is the transparent
part of the eye, the rays are in a certain degree refracted. Passing
through the coat called cornea, they enter the aqueous humour.
In their transmission through it, they pass into the pupil. They
enter the lens or crystalline humour, and by the greater power of
refraction in this humour, the rays are drawn to a point and im-

82 NATURAL THEOLOGY.

pinge on the bottom of the eye at A, B. It will be further seen
that the rays coming from B are refracted to a, those from A to b,
and that the image is therefore represented inverted.]

as the lenses of a telescope are constructed, for
the refraction of rays of light to a point, which
forms the proper action of the organ ; the provi-
sion in its muscular tendons for turning its pupil to
the object, similar to that which is given to the te-
lescope by screws, and upon which power of
direction in the eye the exercise of its office as an
optical instrument depends ; the further provision
for its defence, for its constant lubricity and moist-
ure, which we see in its socket and its lids, in its
glands for the secretion of the matter of tears, its
outlet or communication with the nose for carry-
ing off the liquid after the eye is washed with it ;
these provisions compose altogether an apparatus,
a system of parts, a preparation of means, so ma-
nifest in their design, so exquisite in their contriv-
ance, so successful in their issue, so precious, and
so infinitely beneficial in their use, as, in my opi-
nion, to bear down all doubt that can be raised
upon the subject.^' And what I wish, under the
title of the present chapter, to observe, is, that if
other parts of nature were inaccessible to our in-
quiries, or even if other parts of nature presented
nothing to our examination but disorder and con-

21 Again we have reference to the structure of the eye; which
shows the necessity of throwing our observations on tliis organ
mto the Appendix.

NATURAL THEOLOGY. 83

fusion, the validity of this example would remain
the same. If there were but one watch in the
world, it would not be less certain that it had
a maker. If we had never in our lives seen any
but one single kind of hydraulic machine, yet, if of
that one kind we understood the mechanism and
use, we should be as perfectly assured that it pro-
ceeded from the hand and thought and skill of a
workman, as if we visited a museum of the arts,
and saw collected there twenty different kinds of
machines for drawing water, or a thousand differ-
ent kinds for other purposes. Of this point each
machine is a proof independently of all the rest. So
it is with the evidences of a Divine agency. The
proof is not a conclusion which lies at the end of
a chain of reasoning, of which chain each instance
of contrivance is only a link, and of which, if one
link fail, the whole falls ; but it is an argument se-
parately supplied by every separate example. An
error in stating an example affects only that ex-
ample. The argument is cumulative, in the ful-
lest sense of that term. The eye proves it without
the ear ; the ear without the eye. The proof in
each example is complete ; for when the design of
the part, and the conduciveness of its structure to
that design is shown, the mind may set itself at
rest; no future consideration can detract any
thing from the force of the example.

84 NATURAL THEOLOGY.

CHAPTER VII.

OF THE MECHANICAL AND IMMECHANICAL PARTS AND
FUNCTIONS OF ANIMALS AND VEGETABLES.

It is not that every part of an animal or vege-
table has not proceeded from a contriving mind ;
or that every part is not constructed with a view
to its proper end and purpose, accordmg to the
laws belonging to, and governing the substance or
the action made use of in that part ; or that each
part is not so constructed as to effectuate its pur-
pose whilst it operates according to these laws;
but it is because these laws themselves are not in
all cases equally understood — or, what amounts
to nearly the same thing, are not equally exempli-
fied in more simple processes, and more simple
machines, that we lay down the distinction, here
proposed, between the mechanical parts of ani-
mals and vegetables.^

^2 The observation here is most sensible. When we speak of
an organ as peculiarly suited to exhibit design, we mean merely
that we comprehend something of the object of the particular
structure. But there is no part of an animal, if we fully compre-
hended what was necessary to the performance of its functions,
that would not raise our admiration. Were we to take a portion
of the skin, and contemplate its exquisite sensibility, so finely ap-
propriated — could we penetrate, as it were, into the pores, and

NATURAL THEOLOGY. 85

[The reader will not be easily convinced that the mass of flesh,
with which he is familiar, is easily and almost spontaneously di-
vided into distinct muscles. This figure represents a muscle. C
is tlie belly of the muscle; A and B the tendons: A being the
tendinous origin, as it is termed, attached to a fixed point of bone;
B the tendinous insertion, being attached to a part movable by
the contraction of the muscle. The belly, C, consists of fibres,
which are possessed of the power of contraction or irritability, and
through the operation of which the various motions of the body
are performed. We shall prescHtly have to remark on the direo
tion of these fibres.]

For instance: the principle of muscular motion,
viz., upon what cause the swelling of the belly of
the muscle, and consequent contraction of its ten-
dons, either by an act of the will, or by involun-
tary irritation, depends, is wholly unknown to us.
The substance employed, whether it be fluid,
gaseous, elastic, electrical, or none of these, or
nothing resembling these, is also unknown to us :

duly estimate the power which regulates the secretions and ab-
sorption— could we fully understand the relations of this organ,
either with the economy of the body within, or the constitution of
the atmosphere without — we should have no occasion to draw
our argument, for the twentieth time, from the structure of the eye
or the ear. Were we to take one cell of the millions of that sub.
stance which, intervening between the more solid textures of the
frame, gives elasticity to the whole, and permits circulation and
muscular action, and all the various movements of the body, we
should have in that one cell as much reason for wonder at the per-
fection of the contrivance, as in any joint of the limb.

8

86 NATURAL THEOLOGY.

of course, the laws belonging to that substance,
and which regulate its action, are unknown to us.
We see nothing similar to this contraction in any
machine which we can make, or any process
which we can execute. So far (it is confessed)
we are in ignorance, but no farther. This power
and principle, from whatever cause it proceeds,
being assumed, the collocation of the fibres to re-
ceive the principle, the disposition of the muscles
for the use and application of the power, is me-
chanical ; and is as intelligible as the adjustment
of the wires and strings by which a puppet is
moved. We see, therefore, as far as respects the
subject before us, what is not mechanical in the
animal frame, and what is. The nervous influence,
(for we are often obliged to give names to things
which we know little about.) — I say the nervous
influence, by which the belly or middle of the
muscle is swelled, is not mechanical. The utility
of the eflfect we perceive — the means, or the pre-
paration of means, by which it is produced, we
do not. But obscurity as to the origin of muscu-
lar motion brings no doubtfulness into our obser-
vations, upon the sequel of the process : which
observations relate — 1st, to the constitution of
the muscle, in consequence of which constitution,
the swelling of the belly or middle part is neces-
sarily and mechanically followed by a contraction
of the tendons; 2dly, to the number and variety
of the muscles, and the corresponding number and
variety of useful powers which they supply to the

NATURAL THEOLOGY. 87

animal, which is astonishingly great ; 3dly, to the
judicious (if we may be permitted to use that
term in speaking of the Author, or of the works, of
Nature,) to the wise and well-contrived disposi-
tion of each muscle for its specific purpose ; for
moving the joint this way, and that way, and the
other way ; for puUing and drawing the part to
which it is attached in a determinate and particu-
lar direction : which is a mechanical operation
exemplified in a multitude of instances. To men-
tion only one : The tendon of the trochlear muscle
of the eye, to the end that it may draw in the line
required, is passed through a cartilaginous ring, at
w^hich it is reverted, exactly in the same manner
as a rope in a ship is carried over a block, or
round a stay, in order to make it pull in the direc-
tion which is wanted. All this, as we have said,
is mechanical, and is as accessible to inspection,
as capable of being ascertained, as the mechanism
of the automaton in the Strand. Supposing the
automaton to be put in motion by a magnet
(w^hich is probable,) it will supply us with a com-
parison very apt for our present purpose. Of the
magnetic effluvium we know perhaps as little as
we do of the nervous fluid. But, magnetic at-
traction being assumed, (it signifies nothing from
what cause it proceeds,) we can trace, or there
can be pointed out to us, with perfect clearness
and certainty, the mechanism, viz., the steel bars,
the wheels, the joints, the wires, by which the
motion so much admired is communicated to the

88 NATURAL THEOLOGY.

fingers of the image ; and to make any obscurity,
or difficulty, or controversy in the doctrine of
magnetism, an objection to our knowledge or our
certainty, concerning the contrivance, or the marks
of contrivance, displayed in the automaton, would
be exactly the same thing as it is to make our ig-
norance (w^hich we acknowledge,) of the cause of
nervous agency, or even of the substance and
structure of the nerves themselves, a ground of
question or suspicion as to the reasoning which
"we institute concerning the mechanical part of
our frame. That an animal is a machine is a
proposition neither correctly true nor wholly false.
The distinction w^hich we have been discussing
will serve to show how far the comparison, which
this expression implies, holds ; and wherein it
fails. And w^hether the distinction be thought of
importance or not, it is certainly of importance to
remember, that there is neither truth nor justice
in endeavouring to bring a cloud over our under-
standings, or a distrust into our reasonings upon
this subject, by suggesting that we know nothing
of voluntary motion, of irritability, of the princi-
ple of life, of sensation, of animal heat, upon all
which the animal functions depend ; for, our ig-
norance of these parts of the animal frame con-
cerns not at all our knowledge of the mechanical
parts of the same frame. I contend, therefore,
that there is mechanism in animals ; that this me-
chanism is as properly such, as it is in machines
made by art ; that this mechanism is intelligible

NATURAL THEOLOGY. 89

and certain ; that it is not the less so, because it
often begins or terminates with something which
is not mechanical ; that whenever it is intelhgible
and certain it demonstrates intention and contri-
vance, as well in the works of nature, as in those
of art ; and that it is the best demonstration which
either can afford.

But whilst I contend for these propositions, I
do not exclude myself from asserting, that there
may be, and that there are, other cases in which,
although we cannot exhibit mechanism, or prove
indeed that mechanism is employed, we want not
sufficient evidence to conduct us to the same con-
clusion.

There is what may be called the chemical part
of our frame ; of which, by reason of the imper-
fection of our chemistry, we can attain to no dis-
tinct knowledge ; I mean, not to a knowledge,
either in degree or kind, similar to that which we
possess of the mechanical part of our frame. It
does not, therefore, afford the same species of ar-
gument as that which mechanism affords ; and yet
it may afford an argument in a Iiigh degree satis-
factory. The gastric juice, or the liquor which
digests the food in the stomachs of animals, is of
this class. Of all the menstrua it is the most active,
the most universal. In the human stomach, for in-
stance, consider what a variety of strange sub-
stances, and how widely different from one another,
it in a few hours reduces to a uniform pulp, milk,
or mucilage. It seizes upon every thing ; it dis-

8*

90 NATURAL THEOLOGY.

solves the texture of almost every thing that
comes in its way. The flesh of perhaps all ani-
mals ; the seeds and fruits of the greatest number
of plants ; the roots and stalks, and leaves of
many, hard and tough as they are, yield to its
powerful pervasion. The change wrought by it
is different from any chemical solution which we
can produce, or with which we are acquainted,
in this respect as well as many others, that, in our
chemistry, particular menstrua act only upon par-
ticular substances. Consider, moreover, that this
fluid, stronger in its operation than a caustic alkali,
or miineral acid, than red precipitate or aqua-fortis
itself, is nevertheless as mild, and bland, and in-
oflfensive to the touch or taste as saliva or gum-
water, wdiich it much resembles. Consider, I say,
these several properties of the digestive organ,
and of the juice w^ith w hich it is supplied, or rather
w^ith which it is made to supply itself, and you
will confess it to be entitled to a name which it
has sometimes received, that of " the chemical
wonder of animal nature."

Still w^e are ignorant of the composition of this
fluid, and of the mode of its action ; by which is
meant, that we are not capable, as we are in the
mechanical part of our frame, of collating it with
the operations of art. And this I call the imper-
fection of our chemistry ; for, should the time ever
arrive, which is not, perhaps, to be despaired of,
when w^e can compound ingredients so as to form
a solvent which will act in the manner in which

NATURAL THEOLOGY. 91

the gastric juice acts, we may be able to ascertain
the chemical principles upon which its efficacy
depends, as well as from what part, and by what
concoction, in the human body these principles
are generated and derived.

In the mean time, ought that, which is in truth
the defect of our chemistry, to hinder us from ac-
quiescing in the inference which a production of
nature, by its place, its properties, its action, its
surprising efficacy, its invaluable use, authorizes
us to draw in respect of a creative design P^

Another most subtle and curious function of
animal bodies is secretion. This function is semi-
chemical and semi-mechanical ; exceedingly im-
portant and diversified in its effects, but obscure
in its process and in its apparatus. The import-
ance of the secretory organs is but too well attest-
ed by the diseases which an excessive, a deficient,
or a vitiated secretion is almost sure of producing.

23 After this enumeration of the things dissolved by the gastric
juice, the most extraordinary fact remains to be stated, that the
dehcate surface of the stomach itself, softer and finer than the
surface of the eye, remains untouched by this humour, which our
autlior, somewhat quaintly, describes as more powerful to dissolve
than aqua-fortis. John Hunter showed us that it was the property
of life that protected the coats of the stomach. This fact is a most
singular proof of the power bestowed through life on the mem-
branes and vessels ; and it is as important as it is curious : for as
the stomach in the dead body no longer resists this menstrum, it
may become dissolved, if the person has died with the fluid
already secreted into the stomach. And so it has happened that
persons have been supposed to be poisoned, and relations have
been falsely accused, from the stomach being found eroded as if
some acrid poison had been taken before death.

92 NATURAL THEOLOGY.

A single secretion being wrong is enough to make
life miserable, or sometimes to destroy it. Nor is
the variety less than the importance. From one
and the same blood, (I speak of the human body,)
about twenty different fluids are separated ; in
their sensible properties, in taste, smell, colour,
and consistency, the most unlike one another that
is possible ; thick, thin, salt, bitter, sweet : and if
from our own we pass to other species of animals,
we find amongst their secretions not only the most
various but the most opposite properties ; the most
nutritious aliment, the deadliest poison ; the sw^eet-
est perfumes, the most foetid odours. Of these
the greater part, as the gastric juice, the saliva,
the bile, the slippery mucilage which lubricates
the joints, the tears which moisten the eye, the
wax which defends the ear, are, after they are
secreted, made use of in the animal economy, are
evidently subservient, and are actually contribut-
ing to the utilities of the animal itself. Other
fluids seem to be separated only to be rejected.
That this also is necessary (though why it w^as
originally necessary we cannot tell,) is shown by
the consequence of the separation being long sus-
pended, which consequence is disease and death.
Akin to secretion, if not the same thing, is assimi-
lation, by which one and the same blood is con-
verted into bone, muscular flesh, nerves, mem-
branes, tendons ; things as difterent as the wood
and iron, canvass and cordage, of which a ship
with its furniture is composed. We have no ope-

NATURAL THEOLOGY. 93

ration of art wherewith exactly to compare all
this, for no other reason, perhaps, than that all
operations of art are exceeded by it. No chemi-
cal election, no chemical analysis or resolution of
a substance into its constituent parts, no mechani-
cal sifting or division that we are acquainted with,
in perfection or variety come up to animal secre-
tion. Nevertheless, the apparatus and process are
obscure, not to say absolutely concealed from our
inquiries. In a few and only a few instances, we
can discern a little of the constitution of a gland.
In the kidneys of large animals, we can trace the
emulgent artery dividing itself into an infinite
number of branches ; their extremities every
where communicating with little round bodies, in
the substance of which bodies the secret of the
machinery seems to reside; for there the change
is made. We can discern pipes laid from these
round bodies towards the pelvis, which is a basin
within the solid of the kidney. We can discern
these pipes joining and collecting together into
larger pipes ; and, when so collected, ending in
innumerable papillee, through which the secreted
fluid is continually oozing into its receptacle. This
is all we know of the mechanism of a gland, even
in the case in which it seems most capable of
being investigated. Yet to pronounce that we
know nothing of animal secretion, or nothing sa-
tisfactorily, and with that concise remark to dismiss
ihe article from our argument, would be to dis-
pose of the subject very hastily and very irration-

94 NATURAL THEOLOGY.

ally. For the purpose which we want, that of
evincing intention, we know a great deal. And
what we know is this. We see the blood carried
by a pipe, conduit, or duct, to the gland. We see
an organized apparatus, be its construction or
action what it will, which we call that gland.
We see the blood, or part of the blood, after it
has passed through and undergone the action of
the gland, coming from it by an emulgent vein or
artery, i, e., by another pipe or conduit. And we
see also at the same time a new and specific fluid
issuing from the same gland by its excretory duct,
i. e., by a third pipe or conduit ; which new fluid
is in some cases discharged out of the body, in
more cases retained within it, and there executing
some important and intelligent office. Now sup-
posing, or admitting, that we know nothing of the
proper internal constitution of a gland, or of the
mode of its acting upon the blood, then our situa-
tion is precisely like that of an unmechanical
looker on, who stands by a stocking-loom, a corn-
mill, a carding-machine, or a thrashing-machine,
at work, the fabric and mechanism of which, as
well as all that passes within, is hidden from his
sight by the outside case ; or, if seen, would be
too complicated for his uninformed, uninstructed
understanding to comprehend. And what is that
situation ? This spectator, ignorant as he is, sees
at one end a material enter the machine, as un-
ground grain the mill, raw cotton the carding-
machine, sheaves of unthrashed corn the thrashing-

NATURAL THEOLOGY. 95

machine ; and, when he casts his eye to the other
end of the apparatus, he sees the material issuing
from it in a new state ; and, what is more, in a
state manifestly adapted to future uses ; the grain
in meal fit for the making of bread, the wool in
rovings ready for spinning into threads, the sheaf
in corn dressed for the mill. Is it necessary that
this man, in order to be convinced that design,
that intention, that contrivance has been employed
about the machine, should be allowed to pull it
to pieces ; should be enabled to examine the parts
separately ; explore their action upon one another,
or their operation, whether simultaneous or suc-
cessive, upon the material which is presented to
them ? He may long to do this to gratify his
curiosity ; he may desire to do it to improve his
theoretic knowledge ; or he may have a more
substantial reason for requesting it, if he happen,
instead of a common visiter, to be a millwright
by profession, or a person sometimes called in to
repair such-like machines when out of order ; but
for the purpose of ascertaining the existence of
counsel and design in the formation of the ma-
chine, he wants no such intromission or privity.
What he sees is sufficient. The effect upon the
material, the change produced in it, the utility of
that change for future applications, abundantly
testify, be the concealed part of the machine or
of its construction what it will, the hand and
agency of a contriver.

If any conformation were wanting to the evi-

96 NATURAL THEOLOGY.

dence which the animal secretions afford of de-
sign, it may be derived, as has been ah-eady hint-
ed, from their variety, and from their appropria-
tion to their place and use. They all come from
the same blood; they are all drawn off by glands:
yet the produce is very different, and the differ-
ence exactly adapted to the work w hich is to be
done, or the end to be answered. No account can
be given of this, without resorting to appointment.
Why, for instance, is the saliva, which is diffused
over the seat of taste, insipid, w^hilst so many
others of the secretions, the urine, the tears, and
the sweat, are salt? Why does the gland within
the ear separate a viscid substance, which defends
that passage ; the gland in the upper angle of the
eye a thin brine, which washes the ball ? Why is
the synovia of the joints mucilaginous; the bile
bitter, stimulating, and soapy? Why does the
juice which flows into the stomach contain powers
which make that bowel the great laboratory, as it
is by its situation the recipient, of the materials of
future nutrition? These are all fair questions ;
and no answer can be given to them but what
calls in intelligence and intention.

My object in the present chapter has been to
teach three things ; first, that it is a mistake to
suppose that, in reasoning from the appearances
of nature, the imperfection of our knowledge pro-
portionably affects the certainty of our conclusion;
for in many cases it does not affect it at all : se-
condly, that the different parts of the animal frame

NATURAL THEOLOGY. 97

may be classed and distributed according to the
degree of exactness with which we compare them
with works of art; thirdly, that the 7nechanical
parts of our frame, or those in which this compa-
rison is most complete, although constituting, pro-
bably, the coarsest portions of nature's workman-
ship, are the most proper to be alleged as proofs
and specimens of design.

^

9

06

NATURAL THEOLOGY.

CHAPTER VIII.

OF MECHANICAL ARRANGEMENT IN THE HUMAN
FRAME.

[This figure fepresents the lower surface or base of the skull.
The hole is the foramen magnum through which the spinal marrow
descends into the spine ; and on each side of the hole are the arti-
culating processes, called the condyles.]

We proceed, therefore, to propose certain ex-
amples taken out of this class ; making choice of
such as, amongst those which have come to our
knowledge, appear to be the most striking and

NATURAL THEOLOGY. 99

the best understood; but obliged, perhaps, to post-
pone both these recommendations to a third: that
of the example being capable of explanation with-
out plates, or figures, or technical language.

OP THE BONES.

I. — I challenge any man to produce in the joints
and pivots of the most complicated or the most
flexible machine that was ever contrived, a con-
struction more artificial, or more evidently artifi-
cial, than that which is seen in the vertebrae of the
human neck, Hwo things were to be done: the
head was to have the power of bending forward
and backward, as in the act of nodding, stooping,
looking upward or downward; and, at the same
time, of turning itself round upon the body to a
certain extent — the quadrant, we w^ill say, or
rather, perhaps, a hundred and twenty degrees of
a circle. For these two purposes, two distinct
contrivances are employed : first, the head rests
immediately upon the uppermost part of the ver-
tebrae, and is united to it by a hinge-]om\. ; upon
w^hich joint the head plays freely forward and
backward, as far either way as is necessary, or as
the ligaments allow ; which was the first thing
required. But then the rotatory motion is unpro-
vided for : therefore, secondly, to make the head
capable of this, a further mechanism is introduced :

100 NATURAL THEOLOGY.

[Tliis figure represents the uppermost vertebra, or atlas ; and
the condyles, mentioned in the former figure, sink into the articu-
lating surfaces of this vertebra, permitting the nodding motions.
a and b are the articulating surfaces ; c is a surface which receives
the tooth of the vertebra below; d the circle through which the
spinal marrow passes.]

not between the head and the uppermost bone of
the neck, where the hinge is but between that
bone and the bone next underneath it. It is a
mechanism resembhng a tenon and jnortise. This
second, or uppermost bone but one, has what ana-
tomists call a process, viz., a projection, somewhat
similar, in size and shape, to a tooth; which tooth
entering a corresponding hole or socket in the
bone above it, forms a pivot or axle, upon
which that upper bone, together with the head
which it supports, turns freely in a circle ; and as
far in the circle as the attached muscles permit
the head to turn. Thus are both motions perfect
without interfering with each other. When we
nod the head, we use the hinge-joint, which lies
between the head and the neck. When we
turn the head round, we use the tenon and mor-
tise, which runs between the first bone of the neck
and the second. ^^

** The meaning of our author is obvious here ; but the tenon

NATURAL THEOLOGY. 101

[Here the tooth-like process of the second vertebra, which is
called dentata, is passed through the ring of the first, and is held
there by a transverse ligament, like a spindle in the bush. No
doubt the object of this complexity is to permit the free motion of
the head, without too great a laxity at any one joining, and there-
by to protect the most vital organ of the body, the medulla oblonga~
ta, or spinal marrow, which passes from the head into the tube of
the spine.]

We see the same contrivance and the same
principle employed in the frame or mounting of
a telescope. It is occasionally requisite that the
object-end of the instrument be moved up and
dovsrn, as well as horizontally, or equatorially. For
the vertical motion, there is a hinge, upon which
the telescope plays ; for the horizontal or equato*
rial motion, an axis upon which the telescope and
the hinge turn round together. And this is exact-
ly the mechanism which is applied to the motion
of the head ; nor will any one here doubt of the

and mortise are terms used for the tirm joining of beams, as in the
carpentry of a roof; not for rotatory motion.

9*

102 NATURAL THEOLOGY.

existence of counsel and design, except it be by
that debility of mind, which can trust to its own
reasonings in nothing.

We may add, that it was, on another account,
also expedient that the motion of the head back-
ward and forward should be performed upon the
upper surface of the first vertebra ; for, if the first
vertebra itself had bent forward, it would have
brought the spinal marrov/, at the very beginning
of its course, upon the point of the tooth.

II. Another mechanical contrivance, not unlike
the last in its object, but difterent and original in its
means, is seen in what anatomists call the frre-arm —
that is, in the arm between the elbow and the wrist.
Here, for the perfect use of the limb, two motions
are w^anted : a motion at the elbow, backward and
forward, which is called a reciprocal motion ; and
a rotatory motion, by w^hich the palm of the hand,
as occasion requires, may be turned upward.
How is this managed ? The fore-arm, it is well
known, consists of two bones, lying alongside each
other, but touching only towards the ends. One,
and only one, of these bones is joined to the cubit,
or upper part of the arm, at the elbow ; the other
alone to the hand at the wrist. The first, by
means, at the elbow, of a hinge-joint (which allows
only of motion in the same plane,) swings back-
ward and forward, carrying along with it the other
bone, and the whole fore-arm. In the meantime,
as often as there is occasion to turn the palm up-
ward, that other bone to which the hand is at-

NATURAL THEOLOGY.

103

[Since it has been our author's pleasure
to take this instance, the figure will illus-
trate his description. A is the lower part of
the arm-bone, or humerus; B is the ulna
and C the radius, the two bones of the fore-
arm. It will be understood how these bones,
being tied together by ligaments, hinge and
move upon the humerus A ; c being the pro-
cess of the ulna, on wliich we rest when
leaning on the elbow. By applying our
hand to the arm, we at once feci the freedom
with which the bone moves in bending and
extending the arm. — When we turn the
key in a lock, or make the guards in fencing
by the motion of the wrist, the ulna B is
stationary, and the radius C turns round
upon the head of the bone at d and e, carry-
ing the hand with it. The rest is abundantly
well explained in the text.]

<

»«>,

H

s

&"

t ached rolls upon the first, by the help of a groove
or hollow near each end of one bone, to which is
fitted a corresponding prominence in the other. If
both bones had been joined to the cubit, or upper
arm, at the elbow, or both to the hand at the wrist,
the thing could not have been done. The first

104 NATURAL THEOLOGY.

was to be at liberty at one end, and the second at
the other; by which means the two actions may
be performed together. The great bone which
carries the fore-arm may be swinging upon its
hinge at the elbow, at the ver}'- time that the les-
ser bone, which carries the hand, may be turning
round it in the grooves. The management, also,
of these grooves, or rather of the tubercles and
grooves, is very observable. The two bones are
called the radius and the ulna. Above, i. e.,
towards the elbow, a tubercle of the radius plays
into a socket of the ulna; whilst below, i. e.,
towards the wrist, the radius finds the socket, and
the ulna the tubercle. A single bone in the fore-
arm, with a ball and socket-joint at the elbow,
which admits of motion in all directions, might, in
some degree, have answered the purpose of both
moving the arm and turning the hand. But how
much better it is accomplished by the present me-
chanism any person may convince himself who
puts the ease and quickness with which he can
shake his hand at the wrist circularly, (moving
likewise, if he pleases, his arm at the elbow at the
same time,) in competition with the comparatively
slow and laborious motion with which his arm can
be made to turn round at the shoulder by the aid
of a ball and socket-joint.

III. The spitie, or back-bone, is a chain of joints
of very wonderful construction. A^arious, difficult,
and almost inconsistent offices were to be exe-
cuted by the same instrument. It was to be firm,

NATURAL THEOLOGY.

105

yet flexible; (now, I know no chain made by art
which is both these ; for by firmness I mean, not
only strength but stability ;) firm, to support the
erect position of the body ; flexible, to allow of the
bending of the trunk in all degrees of curvature.
It was further also (which is another and quite a
distinct purpose from the rest,) to become a pipe
or conduit for the safe conveyance from the brain
of the most important fluid of the animal frame,
that, namely, upon which all voluntary motion
depends, the spinal marrow; a substance not only
of the first necessity to action, if not to life, but of
a nature so delicate and tender, so susceptible and
so impatient of injury, as that any unusual pressure
upon it, or any considerable obstruction of its
course, is followed by paralysis or death.

[This represents a section of three of the lower vertelii ae. Tlic
subject being by no means exhausted in the text, the reader will
find it taken up in the Appendix.]

106 NATURAL THEOLOGY

Now the spine was not only to furnish the main
trunk for the passage of the medullary substance
from the brain, but to give out, in the course of
its progress, small pipes therefrom, which, being
afterwards indefinitely subdivided, might, under
the name of nerves, distribute this exquisite supply
to every part of the body. The same spine was
also to serve another use not less wanted than the
preceding, viz., to aftbrd a fulcrum, stay, or basis
(or, more properly speaking, a series of these,) for
the insertion of the muscles which are spread over
the trunk of the body ; in which trunk there are
not, as in the limbs, cylindrical bones to which
they can be fastened : and likewise, which is a
similar use to furnish a support for the ends of
the ribs to rest upon.

Bespeak of a workman a piece of mechanism
which shall comprise all these purposes, and let
him set about to contrive it ; let him try his skill
upon it ; let him feel the difficulty of accomplish-
ing the task, before he be told how the same thing
is effected in the animal frame. Nothing will en-
able him to judge so well of the wisdom which
has been employed ; nothing will dispose him to
think of it so truly. First, for the firmness, yet
flexibility, of the spine ; it is composed of a great
number of bones (in the human subject, of twenty-
four.) joined to one another, and compacted by
broad bases. The breadth of the bases upon
which the parts severally rest, and the closeness
of the junction, give to the chain its firmness and

NATURAL THEOLOGY. 107

Stability ; the number of parts, and consequent
frequency of joints, its flexibility. Which flexi-
bility, we may also observe, varies in difterent parts
of the chain ; is least in the back, where strength
more than flexure is wanted ; greater in the loins,
which it was necessary should be more supple
than the back ; and greatest of all in the neck, for
the free motion of the head. Then, secondly, in
order to aflbrd a passage for the descent of the
medullary substance, each of these bones is bored
through in the middle, in such a manner as that,
when put together, the hole in one bone falls into
a line and corresponds with the holes in the two
bones contiguous to it. By which means the per-
forated pieces, when joined, form an entire, close,
uninterrupted channel, at least whilst the spine is
upright and at rest. But as a settled posture is
inconsistent with its use, a great difficulty still re-
mained, which was to prevent the vertebrae shift-
ing upon one another, so as to break the line of
the canal as often as the body moves or twists,
or the joints gaping externally whenever the body
is bent forward and the spine thereupon made to
take the form of a bow. These dangers, which
are mechanical, are mechanicallyprovided against.
The vertebra3, by means of their processes and
projections, and of the articulations which some
of these form with one another at their extremi-
ties, are so locked in and confined as to maintain,
in what are called the bodies or broad surfaces of
the bones, the relative position nearly unaltered,

108 NATURAL THEOLOGY.

and to throw the change and the pressure pro-
duced by flexion almost entirely upon the inter--
vening cartilages, the springiness and yielding
nature of whose substance admits of all the mo-
tion which is necessary to be performed upon
them, without any chasm being produced by a
separation of the parts. I say, of all the motion
which is necessary ; for although we bend our
backs to every degree almost of inclination, the
motion of each vertebrae is very small : such is
the advantage we receive from the chain being
composed of so many links, the spine of so many
bones. Had it consisted of three or four bones
only, in bending the body the spinal marrow must
have been bruised at every angle. The reader
need not be told that these intervening cartilages
are gristles, and he may see them in perfection in
a loin of veal. Their form also favours the same
intention. They are thicker before than behind ;
so that, when we stoop forward, the compressible
substance of the cartilage, yielding in its thicker
and anterior part to the force which squeezes it,
brings the surface of the adjoining vertebrae nearer
to the being parallel with one another than they
were before, instead of increasing the inclination
of their planes, which must have occasioned a
fissure or opening between them. Thirdly, for
the medullary canal giving out in its course, and
in a convenient order, a supply of nerves to dif-
ferent parts of the body, notches are made in the
upper and lower edge of every vertebrae, two on

NATURAL THEOLOGY. 109

each edge, equidistant on each side from the mid-
dle hne of the back. When the vertebrae are put
together, these notches, exactly fitting, form small
holes, through which the nerves at each articula-
tion issue out in pairs, in order to send their bran-
ches to every part of the body, and with an equal
bounty to both sides of the body. The fourth
purpose assigned to the same instrument is the
insertion of the bases of the muscles, and the sup-
port of the ends of the ribs ; and for this fourth
purpose, especially the former part of it, a figure
specifically suited to the design, and unnecessary
for the other purposes, is given to the constituent
bones. Whilst they are plain, and round, and
smooth towards the front, where any roughness or
projection might have wounded the adjacent vis-
cera, they run out behind, and on each side, into
long processes, to which processes the muscles
necessary to the motions of the trunk are fixed,
and fixed with such art, that, whilst the vertebra
supply a basis for the muscles, the muscles help
to keep these bones in their position, or by their
tendons to tie them together. That most impor-
tant, however, and general property, viz., the
strength of the compages, and the security against
luxation, was to be still more specially consulted ;
for, where so many joints were concerned, and
where, in every one, derangement would have
been fatal, it became a subject of studious precau-
tion. For this purpose the vertebras are articulat-
ed, ihat is, the movable joints between them are

10

iiO NATURAL THEOLOGY.

formed by means of those projections of their
substance which we have mentioned under the
name of processes, and these so lock in with and
overwrap one another as to secure the body of
the vertebra not only from accidentally slipping,
but even from being pushed out of its place by any
violence short of that which would break the bone.
I have often remarked and admired this structure
in the chine of a hare. In this, as in many in-
stances, a plain observer of the animal economy
may spare himself the disgust of being present at
human dissections, and yet learn enough for his in-
formation and satisfaction, by even examining the
bones of the animals which come upon his table.
Let him take, for example, into his hands a piece
of the clean-picked bone of a hare's back, consist-
ing, wx will suppose, of three vertebrae. He will
find the middle bone of the three so implicated,
by means of its projections or processes, with the
bone on each side of it, that no pressure which
he can use will force it out of its place between
them. It will give way neither forward nor back-
ward, nor on either side. In whichever direc-
tion he pushes, he perceives, in the form, or junc-
tion, or overlapping of the bones, an impediment
opposed to his attempt, a check and guard against
dislocation. In one part of the spine he will find
a still further fortifying expedient, in the mode
according to which the vertebrse are annexed to
the spine. Each rib rests upon two vertebrae.

NATURAL THEOLOGY. Ill

That is the thing to be remarked, and any one
may remark it in carving a neck of mutton. Tiie
manner of it is this: the end of the rib is divided
by a middle ridge into two surfaces, which sur-
faces are joined to the bodies of two contiguous
vertebra}, the ridge applying itself to the inter-
vening cartilage. Now this is the very contri-
vance which is employed in the famous iron
bridge at my door at Bishop-Wearmouth, and
for the same purpose of stability, viz., the cheeks
of the bars which pass between the arches
ride across the joints by which the pieces com-
posing each arch are united. Each cross-bar
rests upon two of these pieces at their place of
junction, and by that position resists, at least in
one direction, any tendency in either piece to slip
out of its place. Thus perfectly, by one means
or the other, is the danger of slipping laterally, or
of being drawn aside out of the line of the back,
provided against; and, to withstand the bones
being pulled asunder longitudinally, or in the di-
rection of that line, a strong membrane runs from
one end of the chain to the other, sufficient to re-
sist any force which is ever likely to act in the
direction of the back or parallel to it, and conse-
quently to secure the whole combination in their
places. The general result is, that not only the
motions of the human body necessary for the or-
dinary offices of life are performed with safety,
but that it is an accident hardly ever heard of that

112 NATURAL THEOLOGY.

even the gesticulations of a harlequin distort his
spine.

Upon the whole, and as a guide to those who
may be inclined to carry the consideration of this
subject further, there are three views under which
the spine ought to be regarded, and in all which
it cannot fail to excite our admiration. These
views relate to its articulations, its ligaments, and
its perforation ; and to the corresponding advan-
tages which the body derives from it, for action,
for strength, and for that which is essential to
every part, a secure communication with the brain.

The structure of the spine is not in general dif-
fei'ent in different animals."^ In the serpent tribe,

'^ There is a notion entertained by the ingenious and somewhat
fanciful physiologists of France, that the extremities of the body,
the parts furthest removed from the centre, are most subject to
change in their conformation, •whilst the central parts of the sys-
tem are the most unvarying. Entertaining such a view, Me lose
much of the interest that is attached to the subject ; and the in-
ference which it is important to draw is forgotten, the accommo-
dation not of parts only, but of the whole framework of the animal
body, to the peculiar condition or necessities of the creature. The
teeth vary because the food is different ; the feet vary, because
the mode of progression is different ; the claws vary in connexion
with the teeth, and the mode of procuring food, by digging, or
scraping, or by holding and tearing. So does the eye, and so
does the ear. But with these adaptations of parts, we must not
jose sight of the fact which is the most important to our conclu-
sions— that the whole is accommodated, as well as the individual
organs.

The spine in all vcrtebrated animals holds its office in perpetu-
ity ; it contains and protects the spinal marrow ; and so far as its
office is permanent, there will be an uniformity in its appearance
in all creatures. But even in man it varies in its structure, in the

NATURAL THEOLOGY. 113

nowever, it is considerably varied; but with a
strict reference to the conveniency of the animal.
For, whereas in quadrupeds the number of verte-
brae is from thirty to forty, in the serpent it is
nearly one hundred and fifty: whereas in men
and quadrupeds the surfaces of the bones are flat,
and these flat surfaces laid one against the other,
and bound tight by sinews ; in the serpent, the
bones play one within another, like a ball and
socket,* so that they have a free motion upon one
another in every direction : that is to say, in men
and quadrupeds, firmness is more consulted ; in
serpents, pliancy. Yet even pliancy is not ob-
tained at the expense of safety. The back-bone
of a serpent, for coherence and flexibility, is one
of the most curious pieces of animal mechanism
with which we are acquainted. The chain of a
watch (I mean the chain which passes between
the spring-barrel and the fusee,) which aims at the

different portions or divisions of it, as these portions are required
to admit of more or less freedom of motion. In the hare, as men-
tioned in the text, the spine is beautifully accommodated to the
motion in running. In the cat-kind, as the leopard or tiger, it has
a lateral mobility, quite different from its stnicture in the horse oi
the stag. In the boar, the vertebrae are unusually firm, and the
processes enormously extended, to give strength to the union with
the head, and to direct the action of the muscles upon the head, so
that he may tear up strong roots and possess his defence in his
powerful tusks. In short, as far as the spine is required to ac-
commodate itself to the motions of the trunk, it is varied with as
fine an adjustment as the furthest bone of the toe or finger.

* Der. Phys. Theol. p. 396.
10*

114 NATURAL THEOLOGY.

same properties, is but a bungling piece of work-
manship in comparison witli that of which we
speak.

lY. The reciprocal enlargement and contrac-
tion of the chest to allow for the play of the lungs,
depends upon a simple yet beautiful mechanical
contrivance, referable to the structure of the bones
which enclose it. The ribs are articulated to the
back-bone, or rather to its side projections, oh-
liquely : that is, in their natural position they
bend or slope from the place of articulation down-
wards. But the basis upon which they rest at
this end being fixed, the consequence of the obli-
quity, or the inclination downwards, is, that when
they come to move, whatever pulls the ribs up-
wards, necessarily, at the same time, draws them
out; and that, whilst the ribs are brought to a
right angle with the spine behind, the sternum, or
part of the chest to which they are attached in
front, is thrust forward. The simple action, there-
fore, of the elevating muscles does the business;
whereas, if the ribs had been articulated with the
bodies of the vertebrae at right angles, the cavity
of the thorax could never have been further en-
larged by a change of their position. If each rib
had been a rigid bone, articulated at both ends to
fixed bases, the whole chest had been immov-
able. Keill has observed that the breast-bone, in
an easy inspiration, is thrust out one-tenth of an
inch; and he calculates that this, added to what
is gained to the space within the chest by the flat-

NATURAL THEOLOGY. 115

tening or descent of the diaphragm, leaves room
for forty-two cubic inches of air to enter at every
drawing-in of the breath. When there is a neces-
sity for a deeper and more laborious inspiration,
the enlargement of the capacity of the chest may
be so increased by efibrt, as that the lungs may
be distended with seventy or a hundred such
cubic inches.* The thorax, says Schelhammer,
forms a kind of bellows, such as never have been,
nor probably will be, made by any artificer.^

V. The patella, or knee-pan, is a curious little
bone : in its form and office unlike any other bone
in the body. It is circular; the size of a crown-
piece ; pretty thick ; a little convex on both sides,
and covered with a smooth cartilage. It lies
upon the front of the knee: and the powerful
tendons, by which the leg is brought forward,
pass through it (or rather it makes a part of their
continuation,) from their origin in the thigh to
their insertion in the tibia. It protects both the
tendon and the joint from any injury which either
might suffer, by the rubbing of one against the
other, or by the pressure of unequal surfaces. It
also gives to the tendons a very considerable me-
chanical advantage, by altering the line of their

2' In the dissertation in the Appendix on the Thorax, it will be
observed that we have additional proofs of the accommodation of
the bones of the trunk, as well as of the bones of the extremities,
to the varying habits and condition of the animal.

* Anat. p. 229.

116

NATURAL THEOLOGY.

ftnm^^^

[Three views of the knee-joints.]

direction, and by advancing it further out from
the centre of motion ; and this upon the principles
of the resohition of force, upon which principles
all machinery is founded. These are its uses.
But what is most observable in it is, that it ap-
pears to be supplemental, as it were, to the frame :
added, as it should almost seem, afterward ; not
quite necessary, but very convenient. It is se-
parate from the other bones : that is, it is not con-
nected with any other bones by the common
mode of union. It is soft, or hardly formed, in
infancy; and produced by an ossification, of the
inception, or progress of which no account can be
given from the structure or exercise of the part.

VI. The shoulder-blade is, in some material re-
spects, a very singular bone : appearing to be made
so expressly for its own purpose, and so indepen-
dently of every other reason. In such quadrupeds
as have no collar-bones, which are by far the greater
number, the shoulder-blade has no bony commu-

NATURAL THEOLOGY. 117

nication with the trunk, either by a joint, or pro-
cess, or in any other way. It does not grow to,
or out of, any other bone of the trunk. It does not
apply to any other bone of the trunk — (I know
not whether this be true of any second bone in the
body, except perhaps the os hyoides:) in strictness,
it forms no part of the skeleton. It is bedded in
the flesh, attached only to the muscles. It is no
other than a foundation bone for the arm, laid in,
separate as it were, and distinct, from the general
ossification. The lower limbs connect themselves
at the hip with bones which form part of the skele-
ton ; but this connexion, in the upper limbs, being
wanting, a basis, whereupon the arm might be ar-
ticulated, was to be supplied by a detached ossifi-
cation for the purpose.^'

^^ The shoulder-blade undergoes many changes, as we view it in
comparative anatomy. That bone which we feel running across
the upper part of the chest and lower part of the neck, the collar-
bone, is properly a process of the shoulder-blade. (See the figure
in the Appendix, No. 7, c. c. ) Its purpose is to hold the shoulders
apart, and to give strength to the arms, by throwing upon the arm
the action of the muscles of the chest. Accordingly, we find it in
climbing animals, in those which require to swing themselves by
the upper extremities, as the monkeys ; but in animals that have a
solid hoof, which implies that the anterior extremity is for the par-
ticular purpose of running or bounding upon the ground, not only
is there no occasion for that variety in the motions of the extremi's
ty, which is produced by the introduction of tliis bone into the skele»
ton of the arm, but it would be injurious — it would deprive the
animal of that elasticity with which it alights upon the ground.
Where there is no clavicle — in the horse and deer, for example,
the shoulder-blade, or scapula, is attached to the trunk by muscles
alone. Hence when the animal makes a leap, it comes down upon

118 NATURAL THEOLOGY.

OF THE JOINTS.

I. The above are a few examples of bones made
remarkable by their configuration ; but to almost
all the bones heloBg joints ; and in these, still more
clearly than in the form or shape of the bones them-
selves, are seen both contrivance and contriving
wisdom. Every joint is a curiosity, and is also
strictly mechanical. There is the hinge-joint and
the mortice and tenon-joint ; each as manifestly
such, and as accurately defined, as any which can
be produced out of a cabinet-maker's shop ; and
one or the other prevails, as either is adapted to the
motion which is wanted — e.g., a mortice and ten-
on, or ball and socket-joint, is not required at the
knee, the leg standing in need only of a motion
backward and forward in the same plane, for which
a binge-joint is sufficient ; a mortice and tenon, or
ball and socket-joint, is wanted at the hip, that not
only the progressive step may be provided for, but
the interval between the limbs may be enlarged
or contracted at pleasure. Now observe what
would have been the inconveniency — i. e., both
the superliuity and the defect of articulation, if the
case had been inverted : if the ball and socket-joint
had been at the knee, and the hinge-joint at the

the fore-less with an clastic rebound, the trunk hanging upon the
muscles, the muscles supponted by the scapula, and the scapula
sustained upon the bones of the extremity. There is no solid sub-
stance to receive the shock. Were the collar-bone introduced here,
it would be snapped across by the percussion, as happens to a man
ivhere he is thrown upon his shoulder.

NATURAL THEOLOGY. 119

hip. The thighs must have been kept constantly
together, and the legs had been loose and strad-
dling. There would have been no use, that we
know of, in being able to turn the calves of the legs
before ; and there would have been great confine-
ment by restraining the motion of the thighs to one
plane. The disadvantage would not have been less,
if the joints at the hip and the knee had been both
of the same sort ; both balls and sockets, or both
hinges : yet why, independently of utility, and of a
Creator who consulted that utility, should the same
bone (the thigh-bone.) be rounded at one end, and
channelled at the other ?

The hinge-joint is not formed by a bolt passing
through the two parts of the hinge, and thus keep-
ing them in their places, but by a ditfe rent expedient.
A strong, tough, parchment-like membrane, rising
from the receiving bones, and inserted all round the
received bones a little below their heads, encloses
the joint on every side. This membrane ties, con-
fines, and holds the ends of the bones together,keep
ing the corresponding parts of the joints — {. e., the
relative convexities and concavities — in close ap-
plication to each other.

For the ball and soclict-joint, beside the mem-
brane already described, there is in some important
joints, as an additional security, a short, strong, yet
flexible ligament, inserted by one end into the head
of the ball, by the other into the bottom of the cup,
which ligament keeps the two parts of the joint so
fii'mlv in their nlace. that none of the motions which

120 NATURAL THEOLOGY.

the limb naturally performs, none of the jerks and
twists to which it is ordinarily liable, nothing less
indeed than the utmost and the most unnatural vio-
lence, can pull them assunder. It is hardly ima-
ginable, how great a force is necessary, even to
stretch, still more to break, this ligament : yet so
flexible is it, as to oppose no impediment to the sup-
pleness of the joint. By its situation also it is in-
accessible to injury from sharp edges. As it can-
not be ruptured (such is its strength,) so it cannot
be cut, except by an accident which would sever
the hmb. If I had been permitted to frame a proof
of contrivance, such as might satisfy the most dis-
trustful inquirer, I know not w^hether I could have
chosen an example of mechanism more unequivo-
cal, or more free from objection, than this ligament.
Nothing can be more mechanical ; nothing, however
subservient to the safety, less capable of being gen-
erated by the action of the joint. I would particu-
larly solicit the reader's attention to this provision,
as it is found in the head of the thigh-hone : to its
strength, its structure and its use. It is an instance
upon which I lay my hand. One single fact, ^veigh-
ed by a mind in earnest, leaves oftentimes the deep-
est impression. For the purpose of addressing dif-
ferent understandings and different apprehensions
— for the purpose of sentiment — for the purpose
of exciting admiration of the Creators works, we
diversify our views, we multiply our examples : but
for the purpose of strict argument, one clear in-
stance is sufficient ; and not only sufficient, but ca-

NATURAL THEOLOGY. 121

pable perhaps of generating a firmer assurance
than what can arise from a divided attention.^

The ginglymus, or hinge-joint, does not it is
manifest, admit of a Hgament of the same kind
with that of the ball and socket-joint ; but it is
always fortified by the species of ligament of
which it does admit. The strong, firm, investing
membrane, above described, accompanies it in
every part ; and in particular joints, this mem-
brane, which is properly a ligament, is considera-
bly stronger on the sides than either before or
behind, in order that the convexities may play
true in their concavities, and not be subject to
slip sideways, which is the chief danger; for the
muscular tendons generally restrain the parts from
going further than they ought to go in the plane
of their motion. In the knee^ which is a joint of
this form, and of great importance, there are su-
peradded to the common provisions for the sta-
bility of the joint, two strong ligaments, which
cross each other — and cross each other in such a
manner, as to secure the joint from being dis-
placed in any assignable direction. "I think,"
says Cheselden, "that the knee cannot be com-
pletely dislocated without breaking the cross liga-

^ This ligament is absent in the orang-outang ; and in the lower
extremity of this animal, there are other points of resemblance to
the structure of the arm ; and certainly the use of the hinder ex-
tremity corresponds with this structure, since he grasps and swings
equally well with either extremity.

n

122 NATURAL THEOLOGY*

ments."* We can hardly help comparing this
with the binding up of a fracture, where the fillet
is almost wholly strapped across, for the sake of
giving firmness and strength to the bandage.

Another no less important joint, and that also
of the ginglymus sort, is the ankle ; yet though
important, (in order, perhaps, to preserve the sym-
metry and lightness of the limb,) small, and, on
that account, more liable to injury. Now this
joint is strengthened — i. e., is defended fix)m dis-
location, by two remarkable processes or prolon-
gations of the bones of the leg, which processes
form the protuberances that we call the inner and
outer ankle. It is part of each bone going down
lower than the other part, and thereby overlap-
ping the joint : so that if the joint be in danger of
slipping outward, it is curbed by the inner pro-
jection— i. e., that of the tibia ; if inward, by the
outer projection — i. e., that of the fibula. Be-
tween both, it is locked in its position. I know
no account that can be given of this structure, ex-
cept its utility.^" Why should the tibia terminate,

30 It is surprising, that among so many instances our author
should omit to notice the perfection in the anlde-joint. When we
stand resting upon the foot, the joint is firm, and yields neither to
the inside nor the outside ; but when we move the foot forward
and point the toe in making the step, such is the happy form of
the bones that the foot is in this position thrown quite loose. The
object here certainly is, that in walking on the irregular ground,
we may have a freedom in directing the foot so as to plant it

+ Ches. Anat. cd. 7th, p. 45.

NATURAL THEOLOGY. 123

at its lower extremity, with a double end, and the
fibula the same — but to barricade the joint on
both sides by a continuation of part of the thickest
of the bone over it ? The joint at the shoulder,
compared with the joint at the lii^j, though both
ball and socket-joints, discovers a difference in
their form and proportions, well suited to the dif-
ferent offices which the limbs have to execute.
The cup or socket at the shoulder is much shal-
lower and flatter than it is at the hip, and is also
in part formed of cartilage set round the rim of
the cup. The socket, into which the head of the
thigh-bone is inserted, is deeper, and made of
more solid materials. This agrees with the duties
assigned to each part. The arm is an instrument
of motion, principally, if not solely. Accordingly,
the shallowness of the socket at the shoulder, and
the yieldingness of the cartilaginous substance
with which its edge is set round, and which in
fact composes a considerable part of its concavity,
are excellently adapted for the allowance of a
free motion and a wide range, both which the
arm wants. Whereas, the lower limb, forming a
part of the column of the body, — having to sup-
port the body, as well as to be the means of its

securely. But before the weight of the body is brought perpendicu-
larly over the foot, there is no danger to the joint, because there is
no strain upon it. Just in proportion as the advancing body be-
gins to bear upon it do the bones take that position, in which
they are as firm as in the knee-joint itself, admitting only the mo-
tion of a hinge.

124 NATURAL THEOLOGY.

locomotion, — firmness was to be consulted as well
as action. With a capacity for motion, in all di-
rections indeed, as at the shoulder, but not in any
direction to the same extent as in the arm, was
to be united stability, or resistance to dislocation.
Hence the deeper excavation of the socket, and
the presence of a less proportion of cartilage upon
the edge.

The suppleness and pliability of the joints we
every moment experience ; and the firmness of
animal articulation, the property we have hitherto
been considering, may be judged of from this
single observation, that, at any given moment of
time, there are millions of animal joints in com-
plete repair and use, for one that is dislocated;
and this, notwithstanding the contortions and
wrenches to which the limbs of animals are con-
tinually subject.

II. The joints, or rather the ends of the bones
which form them, display also, in their configura-
tion, another use. The nerves, blood-vessels, and
tendons, which are necessary to the life, or for
the motion, of the limbs, must, it is evident, in
their way from the trunk of the body to the place
of their destination, travel over the movable
joints; and it is no less evident that, in this part
of their course, they will have, from sudden mo-
tions, and from abrupt changes of curvature, to
encounter the danger of compression, attrition, or
laceration. To guard fibres so tender against
consequences so injurious, their path is in those

T^ATURAL THEOLOGY. 125

parts protected with peculiar care ; and that by a
provision in the figure of the bones themselves.
The nerves which supply the fore-arm, especially
the inferior cubital nerves, are at the elbow con-
ducted, by a kind of covered way, between the
condyls, or rather under the inner extuberances
of the bone which composes the upper part of the
arm.* At the knee, the extremity of the thigh-
bone is divided by a sinus, or cliff, into two heads
or protuberances; and these heads on the back-
part stand out beyond the cylinder of the bone.
Through the hollow which lies between the hind-
parts of these two heads — that is to say, under
the ham, between the ham-strings, and within the
concave recess of the bone formed by the extu-
berances on each side — in a word, along a de-
file, between rocks, pass the great vessels and
nerves which go to the leg.f Who led these ves-
sels by a road so defended and secured? In the
joint at the shoulder, in the edge of the cup which
receives the head of the bone, is a notch, which is
joined or covered at the top with a ligament.
Through this hole, thus guarded, the blood-vessels
steal to their destination in the arm, instead of
mounting over the edge of the concavity.J

III. In all joints, the end of the bones, which
work against each other, are tipped with gristle.
In the ball and socket-joint, the cup is lined and

* Ches. Anat. p. 255, ed. 7.
t Ibid. p. 35. I Ibid, p. 30.

11*

126

NATURAL THEOLOGY.

the ball capped with it. The smooth surface, the
elastic and uiifriable nature of cartilage, render it
of all substances the most proper for the place and
purpose. I should, therefore, have pointed this
out amongst the foremost of the provisions which
have been made in the joints for the facilitating
of their action, had it not been alleged, that car-
tilage in truth is only nascent or imperfect bone;
and that the bone in these places is kept soft and
imperfect, in consequence of a more complete
and rigid ossification being prevented from taking
place by the continual motion and rubbing of the
surfaces: which being so, what we represent as a
designed advantage is an unavoidable effect. I
am far from being convinced that this is a true
account of the fact ; or that, if it were so, it an-
swers the argument."' To me the surmounting of
the bones with gristle looks more like a plating
with a different metal, than like the same metal

^^ As the Archdeacon had been a pupil of Dr. WilUam Hun-
ter's, which we gather from the tenor of many of liis observations,
it is surprising that he has not spoken v.ith more decision upon
this point. The cartilage, which is the substitute for the bone in
infancy, is very different from that which tips the ends of the ar-
ticulating extrerrxities of the bones. In a valuable paper of Dr.
Hunter's, it is shown that tliis articulating cartilage consists of
fibres, placed together like the hairs of a brush, but more com-
pactly, and perpendicularly to the ends of the bones ; and that on
liiis arrangement chiefly depends the elasticity of the material.
Its use is best proved by what takes place when it is deficient :
for then the articulation creaks like an old hinge, and the patient
suffers aches.

NATURAL THEOLOGY, 137

kept in a different state by the action to which it
is exposed. At all events, we have a great par-
ticular benefit, though arising from a general con-
stitution; but this last, not being quite what my
argument requires, lest I should seem by applying
the instance to overrate its value, I have thought
it fair to state the question which attends it.

IV, In some joints, very particularly in the knees,
there are loose cartilages or gristles between the
bones, and within the joint, so that the ends of the
bones, instead of working upon one another, w ork
upon the intermediate cartilages. Cheselden has
observed,* that the contrivance of a loose ring is
practised by mechanics where the friction of the
joints of any of their machines is great, as between
the parts of crook-hinges of large gates, or under
the head of the male screw of large vices. The
cartilages of which we speak have very much of
the form of these rings. The comparison, more-
over, shows the reason why we find them in the
knees rather than in other joints. It is an expe-
dient, w^e have seen, w^hich a mechanic resorts to
only wiien some strong and heavy work is to be
done. So here the thigh-bone has to achieve its
motion at the knee, with the whole weight of the
body pressing upon it, and often, as in rising from
our seat, with the whole weight of the body to lift.
It should seem also, from Cheselden's account, that

* Ches. Anat. p. 13, ed. 7,

128 NATURAL THEOLOGY.

the slipping and sliding of the loose cartilages,
though it be probably a small and obscure change,
humoured the motion at the end of the thigh-bone,
under the particular configuration which was neces-
sary to be given to it for the commodious action of
the tendons (and which configuration requires w^hat
he calls a variable socket, that is, a concavity, the
lines of which assume a different curvature in dif-
ferent inclinations of the bones.)^"

V. We have now done with the configuration :
but there is also in the joints, and that common to
them all, another exquisite provision manifestly
adapted to their use, and concerning which there
can, I think, be no dispute, namely, the regular sup-
ply of a mucilage, more emollient and slippery than
oil itself, which is constantly softening and lubricat-
ing the parts that rub upon each other, and thereby

^2 This is not explained with our author's usual clearness. The
lower head of the thigh-bone, which rests upon the shin-bone or
tibia, is not the segment of a regular circle. When we stand with
the knees straight, the thigh-bone rests with a broad surface, and
the convexity is principally on the back part. Such an irregularity
would make a very imperfect and jarring hinge-joint on any con-
figuration that could be given to the corresponding surface of the
tibia. Therefore these cartilages intervene ; and, being possessed
of considerable elasticity, and so connected with the bone as to
shift their place a little, they accommodate themselves, whether the
flatter end or the more convex part of the articulating surface of
the bone be presented to them ; and there is this advantage, that,
in standing, when the Aveight on the joint is greatest, the thigh-
bone has a more extensive, and consequently a more secure basis,
at the same time that the motion of the joint as a hinge is perfect,

NATURAL THEOLOGY. 129

diminishing the effect of attrition in the highest pos^
sible degree. For the continual secretion of this
important liniment, and for the feeding of the cavi-
ties of the joint with it, glands are fixed near each
joint, the excretory ducts of which glands, dripping
with their balsamic contents, hang loose like fringes
within the cavity of the joints. A late improve-
ment in what are called friction wiieels, which con-
sist of a mechanism so ordered as to be regularly
dropping oil into a box which encloses the axis, the
nave, and certain balls upon which the nave re-
volves, may be said, in some sort, to represent the
contrivance in the animal joint, with this superior-
ity, however, on the part of the joint, viz., that here
the oil is not only dropped, but made.

In considering the joints, there is nothing, per-
haps, which ought to move our gratitude more than
the reflection, how well they wear. A limb shall
swing upon its hinge, or play in its socket, many
hundred times in an hour, for sixty years together,
without diminution of its agility, which is a long
time for anything to last — for anything so much
worked and exercised as the joints are. This dura-
bility I should attribute in part to the provision which
is made for the preventing of wear and tear, first by
the polish of the cartilaginous surfaces ; secondly,
by the healing lubrication of the mucilage, and, in
part, to that astonishing property of animal consti-
tutions, assimilation, by which, in every portion of

130 NATURAL THEOLOGY.

the body, let it consist of what it will, substance s
restored, and waste repaired.^

Movable joints, I think, compose the curiosity
of bones ; but their union, even where no motion
is intended or wanted, carries marks of mechanism
and of mechanical wisdom. The teeth, especially
the front teeth, are one bone fixed in another, like
a peg driven into a board. The sutures of the skull
are like the edges of two saws clapped together in
such a manner as that the teeth of one enter the
intervals of the other. We have sometimes one
bone lapping over another, and planed dow^n at the

^ This subject is touched upon in the Appendix, in treating of
the spine. We may here take a practical illustration. We have
said that exercise is necessary to the perfection of a joint. Sup-
pose the knee-joint to be inflamed : it is of course kept in perfect
rest, because motion produces pain. This absolute rest, joined
with inflammation, alters all the textures ; the bone becomes light
and spongy ; the cartilage is absorbed ; the ligaments which ought
to hold the bones together become loose and relaxed ; and what
the surgeon calls consecutive dislocation may take place — that is,
the bones will actually shift their place, from the defect of those
attachments which ought to keep them together. JNow, let us sup-
pose the inflammation to have subsided : by due attention all may
be restored ; and by no other mode than moving the joint — the
only precaution necessary being, that it shall be moved with a care
and gentleness corresponding to its weakened condition. By this
simple means the ligaments will acquire firmness, the cartilages
smoothness, and the synovia, or lubricating mucilage, will be again
poured out : from all which we see, that in the living animal tex-
tures, wear and tear do not take place upon continued motion ; but,
on the contrary, that exercise is made the stimulus to improvement.
All other proofs of design, as adjustment, relation, compensation,
prospective contrivance, are weak in comparison with this.

NATURAL THEOLOGY. 131

edges ; sometimes also the thin lamella of one bone
received into a narrow furrow of another. In all
which varieties we seem to discover the same de-
sign, viz., firmness of juncture without clumsiness
in the seam.

132 NATURAL THEOLOGY.

CHAPTER IX.

OF THE MUSCLES.

Muscles, with their tendons, are the instru-
ments by which animal motion is performed. It
will be our business to point out instances in which
and properties with respect to which, the disposi-
tion of these muscles is as strictly mechanical as
that of the wires and strings of a puppet.

I. We may observe, what I believe is universal,
an exact relation between the joint and the muscles
which move it. Whatever motion the joint, by its
mechanical construction, is capable of performing,
that motion the annexed muscles, by their position,
are capable of producing. For example, if there
be, as at the knee and elbow, a hinge-joint, capa-
ble of motion only in the same plane, the leaders,
as they are called, {, e., the muscular tendons, are
placed in directions parallel to the bone, so as, by
thecontractionor relaxation of the muscles to which
they belong, to produce that motion and no other.
If these joints were capable of a freer motion, there
are n^ muscles to produce it. Whereas, at the
shouldi^r and the hip, where the ball and socket-
joint allows by its construction of a rotatory or
sweeping motion, tendons are placed in such a posi-

NATURAL THEOLOGY. 133

tion, and pull in such a direction, as to produce the
motion of which the joint admits. For instance,
the sartoriusor tailor's muscle, rising from the spine,
running diagonally across the thigh, and taking hold
of the inside of the main bone of the leg a little
below the knee, enables us, by its contraction, to
throw one leg and thigh over the other, giving ef-
fect, at the same time, to the ball and socket-joint
at the hip, and the hinge-joint at the knee. There
is, as we have seen, a specific mechanism in the
bones for the rotatory motions of the head and hands :
there is, also, in the oblique direction of the muscles
belonging to them, a specific provision for the put-
ting of this mechanism of the bones into action.
And mark the consent of uses : the oblique muscles
would have been inefficient without that particular
articulation ; that particular articulation would have
been lost without the oblique muscles. It may be
proper, however, to observe, with respect to the
head, although I think it does not vary the case,
that its oblique motions and inclinations are often
motions in a diagonal produced by the joint action
of muscles lying in straight directions. But whether
the pull be single or combined, the articulation is
always such as to be capable of obeying the action
of the muscles. The oblique muscles attached to
the head are likewise so disposed as to be capable
of steadying the globe as w^ell as of moving it. The
head of a new-born infant is often obliged to be
filleted up. After death the head drops and rolls
in every direction. So that it is by the equilibre

12

134 NATURAL THEOLOGY.

of the muscles, by the aid of a considerable and
equipolent muscular force in constant exertion, that
the head maintains its erect posture. The muscles
here supply what would otherwise be a great de-
fect in the articulation ; for the joint in the neck,
although admirably adapted to the motion of the
head, is insufficient for its support. It is not only
by the means of a most curious structure of the
bones that a man turns his head, but by virtue of
an adjusted muscular power that he even holds
it up.

As another example of what we are illustrating,
viz., conformity of use between the bones and the
muscles, it has been observed of the diiferent ver-
tebra?, that their processes are exactly proportioned
to the quantity of motion which the other bones al-
low of, and which the respective muscles are capa-
ble of producing.

II. A muscle acts only by contraction. Its force
is exerted in no other way. When the -exertion
ceases, it relaxes itself; that is, it returns by relaxa-
tion to its former state, but without energy.^* This

3* Excellently well as this is put, there is something more admi-
rable still in the condition of the muscular system. With respect
to the S'lpport of the head, as mentioned in the preceding page, and
the instance embraces, of course, the erect position of the body as
well as the equable poising of the head, the most extraordinary part
of the plienomenon is this, that we are sensible of the slightest in-
clination of the body or of any member, although it would be diffi-
cult to say to what order of acknowledged sensations this belongs.
Not onlv do we feel every degree of inclination from the perpen-
dicular in the poising of the body, but we act upon it with the most

NATURAL THEOLOGY. 135

is the nature of the muscular fibre ; and being so,
it is evident that the reciprocal energetic motion
of the limbs, by which we mean motion with force
in opposite directions, can only be produced by the
instrumentality of opposite or antagonist muscles —
of flexors and extensors answering to each other.
For instance, the biceps and brachialis internus
muscles placed in the front part of the upper arm,
by their contraction, bend the elbow, and with such
degree of force as the case requires or the strength
admits of. The relaxation of these muscles after
the eftbrt would merely let the forearm drop down.
For the hack stroke, therefore, and that the arm
may not only bend at the elbow, but also extend
and straighten itself with force, other muscles, the
longus and brevis brachialis externus, and the an-
conseus, placed on the hinder part of the arms, by
their contractile twitch, fetch back the forearm
into a straight line with the cubit, with no less force
than that with w^hich it was bent out of it. The
same thing obtains in all the limbs, and in every

minute correspondence of the muscles. The muscles are antago-
nists certainly, but there is a fine combination and adjustment in
tlieir action, which is not illustrated by the two saM'yers dividing a
log of wood. The muscle having finished what we call its action
or contraction, is not in the condition of a loose rope, but on the
contrary tliere is always a perfe.ct balance of action preserved be-
tween the extent of relaxation of the one class of muscles, and the
contraction of the other; and there is a tone in both by which the
limb may be sustained in any posture that is willed. Tliis subject
is treated in the Philosophical Transactions, and also in the Trea-
tise on the Hand, under the head of the " Muscular Sense."

136 NATURAL THEOLOGY.

movable part of the body. A finger is not bent
and straightened without the contraction of two
muscles taking place. It is evident, therefore, that
the animal functions require that particular dispo-
sition of the muscles which we describe by the
name of antagonist muscles. And they are accor-
dingly so disposed. Every muscle is provided with
an adversary. They act like two sa^v} ers in a pit^
by an opposite pull ; and nothing, surely, can more
strongly indicate design and attention to an end
than their being thus stationed, than this colloca-
tion. The nature of the muscular fibre being what
it is, the purposes of the animal could be answered
by no other. And not only the capacity for mo-
tion, but the aspect and symmetry of the body is
preserved by the muscles being marshalled accor-
ding to this order — e. g., the mouth is holden in
the middle of the face, and its angles kept in a state
of exact correspondency, by two muscles drawing
against and balancing each other. In a hemiple-
gia, when the muscle on one side is weakened, the
muscle on the other side draws the mouth awry.
III. Another property of the muscles, which
could only be the result of care, is, their being al-
most universally so disposed as not to obstruct or
interfere with one another's action. I know but
one instance in which this impediment is perceived.
We cannot easily swallow whilst we gape. This^
I understand, is owing to the muscles employed in
the act of deglutition being so implicated with the
muscles of the lower jaw, that whilst these last are

NATURAL THEOLOGY. 137

contracted, the former cannot act with freedom.
The obstruction is, in this instance, attended with
little inconvenience ; but it shows what the effect
is where it does exist; and what loss of faculty-
there would be if it were more frequent. Now,
when we reflect upon the number of muscles, not
fewer than four hundred and forty-six, in the human
body, known and named,* how contiguous they lie
to each other, in layers, as it were, over one an-
other, crossing one another, sometimes embedded
in one another, sometimes perforating one an-
other — an arrangement which leaves to each its
liberty, and its full play, must necessarily require
meditation and counsel.

IV. The following is oftentimes the case with
the muscles. Their action is wanted where their
situation would be inconvenient. In which case
the body of the muscle is placed in some commo-
dious position at a distance, and made to commu-
nicate with the point of action by slender strings
or wires. If the muscles which move the fingers
had been placed in the palm or back of the hand,
they would have swelled that part to an awkward
and clumsy thickness. The beauty, the propor-
tions of the part, would have been destroyed. They
are therefore disposed in the arm, and even up to
the elbow, and act by long tendons strapped down
at the wrist, and passing under the ligaments to the
fingers, and to the joints of the fingers which they

*Keill's Anatomy, p. 295, ed. 3.
12*

138 NATURAL THEOLOGY,

are severally to move. In like manner, the mus-
cles which move the toes and many of the joints
of the foot, how gracefully are they disposed in the
calf of the leg, instead of forming an unwieldy
tumefaction in the foot itself! The obsei-vation
may be repeated of the muscle w^hich draws the
nictitating membrane over the eye. Its office is in
the front of the eye ; but its body is lodged in the
back part of the globe, wiiere it lies safe, and where
it encumbers nothing.

V. The great mechanical variety in the figure
of the muscles may be thus stated. It appears to
be a fixed law that the contraction of a muscle
shall be towards its centre. Therefore the sub-
ject for mechanism on each occasion is, so to
modify the figure and adjust the position of the
muscle as to produce the motion required agree-
ably with this law. This can only be done by
giving to different muscles a diversity of configu-
ration suited to their several offices, and to their
situation with respect to the work which they
have to perform. On which account we find them
under a multiplicity of forms and attitudes ; some-
times with double, sometimes with treble tendons,
sometimes with none: sometimes one tendon to
several muscles, at other times one muscle to
several tendons. The shape of the organ is sus-
ceptible of an incalculable variety, whilst the ori-
ginal property of the muscle, the law and line of
its contraction, remains the same, and is simple.
Herein the muscular system may be said to bear

NATURAL THEOLOGY.

139

a perfect resemblance to our works of art. An
artist does not alter the native quality of his
materials, or their laws of action. He takes these
as he finds them. His skill and ingenuity are em-
ployed in turning them, such as they are, to his
account, by giving to the parts of his machine a
form and relation in which these unalterable pro-
perties may operate to the production of the
effects intended.^^

^ In the figure of a muscle, given in page 85, it may be observ-
ed that the tendons are on different sides of the muscle.
A

If we were to plan their arrangement it would be thus : A is the
tendinous origin, and B the tendinous insertion ; and the muscu-
lar fibres run obliquely between them. Tliis obliquity of the

140 NATURAL THEOLOGY.

VI. The ejaculations can never too often be
repeated — How many things must go right for us
to be an hour at ease ! how many more for us to
be vigorous and active ! Yet vigour and activity
are, in a vast phu'ahty of instances, preserved in
human bodies, notwithstanding that they depend
upon so great a number of instruments of motion,
and notwithstandinsj that the defect or disorder
sometimes of a very small instrument, of a single
pair, for instance, out of the four hundred and

fibres is almost universal in the muscles of the limb, and the
effect is very important. It needs no reference to mechanics to
understand, that if we pull obliquely upon a weight we sacrifice
a great deal of power. For what advantage, then, is power re-
signed in the muscle ? " If 3'ou wish to draw a thing towards
any place with the least force, you must pull directly in the line
between the thing and the place ; but if you wish to draw it as
quickly as possible, and do not regard the loss of force, you must
pull it obliquely, by drawing it in two directions at once. Tie a
string to a stone A, and draw it straight towards you at C with
one hand ; then make a loop on another string, and running the
first through it, draw one string in each hand at B B, not towards
you, in the line A C, but sideways, till both strings are stretched
in a straight line : you will see how much swifter the stone moves
than it did before when pulled straightforward. Now this is
proved by mathematical reasoning to be the necessary con-
sequence of forces apphed obliquely ; there is a loss of power, but
a great increase of velocity. The velocity is the tiring required
to be gained."*

By the liberal employment of muscular power, quickness and
variety of motion are obtained, and with the advantages which
are so well described in the succeeding part of this chapter.

* Preliminary treatise on the objects, advantages, and pleasures
of science. (Library of Useful Knowledge.)

NATURAL THEOLOGY. 141

forty-six muscles which are employed, may be
attended with grievous inconvenicncy. There is
piety and good sense in the following observation
taken out of the "Religious Philosopher :" " With
much compassion," says this writer, " as well as
astonishment at the goodness of our loving Crea-
tor, have I considered the sad state of a certain
gentleman, who, as to the rest, was in pretty good
health, but only wanted the use of these two little
muscles that serve to lift up the eyelids, and so
had almost lost the use of his sight, being forced,
as long as this defect lasted, to shove up his eye-
lids every moment with his own hands !" In
general we may remark in how small a degree
those who enjoy the perfect use of their organs
know the comprehensiveness of the blessing, the
variety of their obligation. They perceive a result,
but they think little of the multitude of concur-
rences and rectitudes which go to form it.

Besides these observations, which belong to the
muscular organ as such, we may notice some ad-
vantages of structure which are more conspicuous
in muscles of a certain class or description than in
others. Thus :

I. The variety, quickness, and precision of
which muscular motion is capable are seen, I
think, in no part so remarkably as in the tongue.
It is worth any man's while to watch the agility
of his tongue, the wonderful promptitude with
which it executes changes of position, and the

142 NATURAL THEOLOGY.

perfect exactness. Each syllable of articulated
sound requires for its utterance a specific action
of the tongue, and of the parts adjacent to it.
The disposition and configuration of the mouth
appertaining to every letter and word, is not only
pecuhar, but, if nicely and accurately attended to,
perceptible to the sight; insomuch, that curious
persons have availed themselves of this circum-
stance to teach the deaf to speak, and to under-
stand what is said by others. In the same per-
son, and after his habit of speaking is formed, one,
and only one, position of the parts w^ill produce a
given articulate sound correctly. How instanta-
neously are these positions assumed and dismissed !
how numerous are the permutations, how various,
yet how infallible ! Arbitrary and antic variety
is not the thing we admire; but variety obeying
a rule, conducing to an effect, and commensurate
with exigencies infinitely diversified. I believe
also that the anatomy of the tongue corresponds
with these observations upon its activity. The
muscles of the tongue are so numerous, and so
impHcated with one another, that they cannot
be traced by the nicest dissection; nevertheless
(which is a great perfection of the organ,) neither
the number, nor the complexity, nor what might
seem to be the entanglement of its fibres, in any-
wise impede its motion, or render the determina-
tion or success of its efforts uncertain.

NATURAL THEOLOGY. 143

I here entreat the reader's permission to step a
little out of my way, to consider the parts of the
mouth in some of their other properties. It has
been said, and that by an eminent physiologist,
that, whenever nature attempts to work two or
more purposes by one instrument, she does both
or all imperfectly. Is this true of the tongue re-
garded as an instrument of speech and of taste,
or regarded as an instrument of speech, of taste,
and of deglutition ? So much otherwise, that
many persons, that is to say nine hundred and
ninety-nine persons out of a thousand, by the in-
strumentality of this one organ, talk, and taste,
and sw^ allow very well. In fact, the constant
warmth and moisture of the tongue, the thinness
of the skin, the papillae upon its surface, qualify
this organ for its office of tasting, as much as its
inextricable multiplicity of fibres do for the rapid
movements which are necessary to speech. Ani-
mals which feed upon grass have their tongues
covered with a perforated skin, so as to admit the
dissolved food to the papillse underneath, which,
in the meantime, remain defended from the rough
action of the unbruised spiculae.

There are brought together within the cavity of
the mouth more distinct uses, and parts executing
more distinct offices, than I think can be found
lying so near to one another, or within the same
compass, in any other portion of the body: viz.,
teeth of diffi?rent shape, first for cutting, secondly
for grinding; muscles, most artificially disposed

144 NATURAL THEOLOGY.

for carr^^ing on the compound motion of the lower
jaw, half lateral and half vertical, by which the
mill is worked : fountains of saliva, springing up in
different parts of the cavity for the moistening of
the food, while the mastication is going on :
glands, to feed the fountains; a muscular constric-
tion of a very peculiar kind in the back part of
the cavity, for the guiding of the prepared aliment
into its passage towards the stomach, and in many
cases for carrying it along that passage ; for, al-
though we may imagine this to be done simply
by the w^eight of the food itself, it in truth is not
so, even in the upright posture of the human
neck ; and most evidently is not the case with
quadrupeds — with a horse, for instance, in which,
when pasturing, the food is thrust upward by mus-
cular strength instead of descending of its own
accord.

In the mean time, and within the same cavity,
is going on another business, altogether different
from what is here described — tliat of respiration
and speech. In addition, therefore, to all that
has been mentioned, we have a passage opened
from this cavity to the lungs, for the admission of
air exclusively of every other substance : we have
muscles, some in the larynx, and without number
in the tongue, for the purpose of modulating that
air in its passage, with a variety, a compass, and
precision, of which no other musical instrument
is capable. And lastly, which, in my opinion,
crowns the whole as a piece of machinery, we

NATURAL THEOLOGY. 145

have a specific contrivance for dividing the pneu-
matic part from the mechanical, and for prevent-
ing one set of actions interfering with the other.
Where various functions are united, the difficulty
is to guard against the inconveniences of a too
great complexity. In no apparatus put together
by art and for the purposes of art, do I know such
multifarious uses so aptly combined, as in the
natural organization of the human mouth; or
where the structure, compared with the uses, is so
simple. The mouth, with all these intentions to
serve, is a single cavity ; is one machine ; with
Its parts neither crowded nor confused, and each
unembarrassed by the rest : each at least at liber-
ty in a degree sufficient for the end to be attained.
If we cannot eat and sing at the same moment,
we can eat one moment and sing the next : the
respiration proceeding freely all the wiiile.

There is one case, however, of this double of-
fice, and that of the earliest necessity, which the
mouth alone could not perform; and that is, car-
rying on together the two actions of sucking and
breathing. Another route therefore is opened for
the air — namely, through the nose — which lets
the breath pass backward and forward, whilst the
lips, in the act of sucking, are necessarily shut
close upon the body from which the nutriment is
drawn. This is a circumstance which always ap-
peared to me worthy of notice. The nose would
have been necessary, although it had not been
the organ of smelling. The making it the seat of

13

146 NATURAL THEOLOGY.

a sense was superadding a new use to a part
already wanted ; was taking a wise advantage of
an antecedent and a constitutional necessity."''

But to return to that which is the proper sub-
ject of the present section — the celerity and pre-
cision of muscular motion. These qualities may
be particularly observed in the execution of many
species of instrumental music, in w^hich the changes

3<5Whcn our author describes the variety of functions performed
by the mouth and toncfue, he is in admiration at the simpHcity of
the instrument. But this is only an apparent simpUcity : the com-
plexity of structure is concealed. Indeed, it has been this very
consideration which led to the new investigations into the nervous
system. Without entering far into this subject, we take the
tongue in illustration. It is a fine organ of touch : it is the seat of
the sense of taste: it is necessary to deglutition : its modulations
are infinite in speech ; but the reason of a body so simple in its
outward form being capable of performing offices apparently so
discordant, is visible onh' to the anatomist, who traces the nerves
into this organ. Then he discovers, besides the nerve proceeding
from the papillae of the tongue to the sensorium, that there are
nerves of volition governing the muscles of the tongue. In addi-
tion to these, there is a nerve which regulates the action of swal-
lowing, and which combines the motions of the gullet with those
of the tongue; and in the same manner another nerve, tending to
the organ of voice in the larynx, branches oft' to the tongue, and
associates it with the organ of the voice, so as to produce articulate
language : these nervous cords are the true organization by which
one member, simple in its exteiior form, has a complexity in its
internal relations. And thus it is, that in many instances organs
which are apparently simple, and through which we perform many
offices so easily that we think not at all of what is necessary to
their execution, have yet internally, and to the eye of the anato-
mist, a thousand minute circumstances or relations on which the
perfection of their action depends.

NATURAL THECLOGY. 147

produced by the hand of the musician are exceed-
ingly rapid; are exactly measured, even when
most minute; and display, on the part of the mus-
cles, an obedience of action alike wonderful for
its quickness and its correctness.

Or let a person only observe his own hand
whilst he is writing; the number of muscles w^hich
are brought to bear upon the pen; how the joint
and adjusted operation of several tendons is con-
cerned in every stroke, yet that five hundred such
strokes are drawn in a minute. Not a letter can
be turned without more than one, or two, or three
tendinous contractions, definite, both as to the
choice of the tendon, and as to the space through
w^hich the contraction moves; yet how currently
does the work proceed ! and when we look at it,
how faithful have the muscles been to their duty
— how true to the order which endeavour or habit
hath inculcated ! For let it be remembered, that,
whilst a man's hand-writing is the same, an exacti-
tude of order is preserved, whether he write well
or ill. These two instances of music and writing
show not only the quickness and precision of mus-
cular action, but the docility.

II. Regarding the particular configuration of
muscles, sphincter or circular muscles appear to be
admirable pieces of mechanism. It is the muscu-
lar power most happily applied; the same quality
of the muscular substance, but under a new modi-
fication. The circular disposition of the fibres is
strictly mechanical : but, though the most mecha-

148 NATURAL THEOLOGY.

nical, IS not the only thing in sphincters which
deserves our notice. The regulated degree of
contractile force with which they are endowed,
sufficient for retention, yet vincible w^hen requisite,
together with their ordinary state of actual con-
traction, by means of which their dependence
upon the will is not constant but occasional, gives
to them a constitution of which the conveniency
is inestimable. This their semi-voluntary charac-
ter is exactly such as suits with the wants and
functions of the animal.

III. We may also, upon the subject of muscles,
observe, that many of our most important actions
are achieved by the combined help of different
muscles. Frequently, a diagonal motion is pro-
duced by the contraction of tendons pulling in the
direction of the sides of the parallelogram. This
is the case, as hath been already notice'd, with
some of the oblique nutations of the head. Some-
times the number of co-operating muscles is very
great. Dr. Nieuentyt, in the Leipsic Transactions,
reckons up a hundred muscles that are employed
every time we breathe ; yet we take in, or let out,
our breath, without reflecting w^hat a work is
thereby performed ; what an apparatus is laid in
of instruments for the service, and how many such
contribute their assistance to the effect. Breath-
ins with ease is a blessinor of every moment ; vet
of all others it is that which we possess with
the least consciousness. A man in an asthma is
the only man who knows how to estimate it.

XATURAL THEOLOGY.

149

IV. Mr. Home has observed,* that the most im-
portant and the most delicate actions are per-
formed in the body by the smallest muscles; and
he mentions, as his examples, the muscles which
have been discovered in the iris of the eye, and
the drum of the ear. The tenuity of these mus-
cles is astonishing: they are microscopic hairs;
must be magnified to be visible ; yet are they rea
effective muscles : and not only such, but the
grandest and most precious of our faculties, sight
and hearing, depend upon their health and action.

[The figure here represents the action of the biceps muscle
which Hes on the arm, and is inserted upon the radius of the fore-
arm in sustaining a weight in the hand.]

V. The muscles act in the limbs with what is
called a mechanical disadvantage. The muscle
at the shoulder, by which the arm is raised, is fixed
nearly in the same manner as the load is fixed
upon a steelyard, within a few decimals, we will
say, of an inch from the centre upon which the
steelyard turnsr In this situation, we find that a

* Phil. Trans, part i. 1800, p. 8.
13*

150 NATURAL THEOLOGY.

very heavy draught is no more than sufficient to
countervail the force ot^ a small lead plummet,
placed upon the long arm of the steelyard, at the
distance of perhaps fifteen or twenty inches from the
centre and on the other side of it. And this is the
disadvantage which is meant ; and an absolute dis-
advantage, no doubt, it would be, if the object
w^ere to spare the force of muscular contraction.
But observe how conducive is this constitution to
animal conveniency. jMechanism has always in
view one or other of these two purposes — either
to move a great weight slowly, and through a
small space, or to move a light weight rapidly,
through a considerable sweep. For the former of
these purposes, a different species of lever, and a
different collocation of the muscles, might be bet-
ter than the present ; but for the second, the pre-
sent structure is the true one. Now so it happens,
that the second, and not the first, is that which
the occasions of animal life principally call for.
In what concerns the human body, it is of much
more consequence to any man to be able to carry
his hand to his head with due expedition, than it
would be to have the power of raising from the
ground a heavier load (of two or three more hun-
dred weight, we^wijl suppose,) than he can lift at
present.

This last is a faculty, which, on some extraordi-
nary occasions, he may desire to possess; but the
other is what he wants and uses every hour or
minute. In like manner, a husbandman or a gar-

NATURAL THEOLOGY. 151

dener will do more execution, by being able to carry
his scithe, his rake, or his flail, with a sufficient des-
patch through a sufficient space, than if, with
greater strength, his motions were proportionably
more confined and slow. It is the same with a
mechanic in the use of his tools. It is the same
also with other animals in the use of their limbs.
In general, the vivacity of their motions would be
ill exchanged for greater force under a clumsier
structure.

We have offered our observations upon the
structure of muscles in general; w^e have also no-
ticed certain species of muscles; but there are
also single muscles which bear marks of mecha-
nical contrivance appropriate as well as particular.
Out of many instances of this kind we select the
following : —

I. Of muscular actions, even of those which are
well understood, some of the most curious are in-
capable of popular explanation ; at least without
the aid of plates and figures. This is in a great
measure the case with a very familiar, but, at the
same time, a very complicated motion, that of the
lower jaw ; and with the muscular structure by
which it is produced. One of the muscles con-
cerned may, however, be described in such a
manner as to be, I think, sufficiently comprehend-
ed for our present purpose. The problem is to
pull the low^er jaw down. The obvious method
should seem to be, to place a straight muscle —
viz., to fix a string from the chin to the breast, the

152 NATURAL THEOLOGY.

contraction of which would open the mouth, and
produce the motion required at once. But it is
evident that the form and hberty of the neck for-
bid a muscle being laid in such a position ; and
that, consistently with the preservation of this
form, the motion which we want must be effectu-
ated by some muscular mechanism disposed fur-
ther back in the jaw. The mechanism adopted is
as follows: — A certain muscle, called the digas-
tric, rises on the side of the face, considerably
above the insertion of the lower jaw, and comes
down, being converted in its progress into a round
tendon. Now it is manifest that the tendon, whilst
it pursues a direction descending towards the jaw,
must, by its contraction, pull the jaw up instead of
down. "What then was to be done ? This, we
find, is done : The descending tendon, when it is
got low enough, is passed through a loop, or ring,
or pully, in the os hyoides, and then made to as-
cend ; and having thus changed its line of direc-
tion, is inserted into the inner part of the chin :
by which device, viz., the turn at the loop, the
action of the muscle (which in all muscles is con-
traction,) that before would have pulled the jaw
up, now as necessarily draws it down. '* The
mouth," says Heister, "is opened by means of this
trochlea in a most wonderful and elegant manner."
II. What contrivance can be more mechanical
than the following, viz., a slit in one tendon to let
another tendon pass through it? This structure
is found in the tendons which move the toes and

NATURAL THEOLOGY. 153

fingers. The long tendon, as it is called, in tlie
foot, which bends the first joint of the toe, passes
through the short tendon which bends the second
joint, which course allows to the sinew more li-
berty, and a more commodious action than it
w^ould otherwise have been capable of exerting.*
There is nothing, I believe, in a silk or cotton
mill, in the belts, or straps, or ropes, by which
motion is communicated from one part of the ma-
chine to another, that is more artificial, or more
evidently so, than this perforation.

III. The next circumstance w'hich I shall men-
tion under this head of muscular arrangement is
so decisive a mark of intention, that it always ap-
peared to me to supersede, in some measure, the
necessity of seeking for any other observation
upon the subject ; and that circumstance is, the
tendons wdiich pass from the leg to the foot, being
bound down by a ligament to the ankle. The
foot is placed at a considerable angle with the leg.
It is manifest, therefore, that flexible strings, pass-
ing along the interior of the angle, if left to them-
selves, would, when stretched, start from it. The
obvious preventive is to tie them down. And this
is done in fact. Across the instep, or rather just
above it, the anatomist finds a strong ligament,
under which the tendons pass to the foot. The
effect of the ligament as a bandage can be made
evident to the senses : for if it be cut, the tendons

*Ches. Anat. p. 119.

154 NATURAL THEOLOGY.

stai't up. The simplicity, yet the clearness of this
contrivance, its exact resemblance to established
resources of art, place it amongst the most indu-
bitable manifestations of design with which we
are acquainted.

There is also a further use to be made of the
present example, and that is, as it precisely con-
tradicts the opinion that the parts of animals may
have been all formed by what is called appetency,
i. e., endeavour perpetuated and imperceptibly
workino^ its effect through an incalculable series
of generations. We have here no endeavour, but
the reverse of it — a constant renitency and re-
luctance. The endeavour is all the other way.
The pressure of the ligament constrains the ten-
dons ; the tendons re-act upon the pressure of the
ligament. It is impossible that the ligament
should ever have been generated by the exercise
of the tendon, or in the course of that exercise,
forasmuch as the force of the tendon perpendicu-
larly resists the fibre which confines it, and is con-
stantly endeavouring, not to form, but to rupture
and displace, the threads of which the ligament is
composed.

Keill has reckoned up in the human body four
hundred and forty-six muscles, dissectible and
describable; and hath assigned a use to every

NATURAL THEOLOGY, 155

one of the number. This cannot be all imagina-
tion.

Bishop Wilkins hath observed from Galen, that
there are at least ten several qualifications to be
attended to in each particular muscle — viz., its
proper figure; its just magnitude; its fulcrum;
its point of action, supposing the figure to be fixed ;
its collocation with respect to its two ends, the
upper and the lower ; the place ; the position of
the whole muscle; the introduction into it of
nerves, arteries, veins. How are things including
so many adjustments to be made? or, w^hen made,
how are they to be put together, w^ithout intelli-
gence ?

I have sometimes wondered why we are not
stinick with mechanism in animal bodies as readi-
ly and as strongly as we are struck with it, at first
sio^ht, in a w^atch or a mill. One reason of the
difference may be, that animal bodies are, in a
great measure, made up of soft flabby substances,
such as muscles and membranes ; whereas we
have been accustomed to trace mechanism m
sharp lines, in the configuration of hard materials,
in the moulding, chiseling, and filing into shapes
of such articles as metals or wood. There is
something therefore of habit in the case ; but it is
sufficiently evident that there can be no proper
reason for any distinction of the sort. Mechanism
may be displayed in die one kind of substance as
well as in the other.

Although the few instances we have selected,

156 NATURAL THEOLOGY.

even as they stand in our description, are nothing
short, perhaps, of logical proofs of design, yet it
must not be forgotten, that, in every part of ana-
tomy, description is a poor substitute for inspec-
tion. It is well said by an able anatomist,"^ and
said in reference to the very part of the subject
which w^e have been treating of: — "Imper-
fecta haec musculorum descriptio non minus ari-
da est legentibus quam inspectantibus fuerit ju-
cunda eorundem pra^paratio. Elegantissima enim
mechanices artificia, creber rime in illis obvia,
verbis nonnisi obscure exprimuntur : carnium
autem ductu, tendinum, colore, insertionum pro-
portione, et trochlearium, distributione, oculis ex-
posita, omnem superant admirationem."

* Steno, in Bias. Anat. Animal, p. 2. c. 4.

NATURAL THEOLOGY.

157

CHAPTER X.

OP THE VESSELS OF ANIMAL BODIES.

[The figure represents the heart and great blood-vessels, and
may convey some idea of the circulation of the blood. We under-
stand A to be the great vein returning the blood from the body ; B
the right sinus or auricle. From this cavity of the heart, the blood

14

15S XATUKAL THEOLOGY.

is carried into C, the ventricle ; and from this ventricle the pulmo-
nary artery goes off. This great artery of the lungs is for the
conveyance of the blood which is returned from the body into the
lungs. Now the great vein A, the auricle B, the ventricle C, and
the pulmonary artery D D, belong to the right side of the heart ;
or, to take a more important distinction, they convey dark-colour-
ed blood, which is unfit for the uses of the system. But when
this blood reaches the lungs, and is exposed to the atmosphere
we breathe, it throws off the carbon, becomes bright in colour,
and is called arterial blood. It returns to the heart, not to the
cavities which we have enumerated, but by the veins of the lungs
to the other side of the heart, the left — that is, to another auricle
and another ventricle. From this left ventricle there ascends the
aorta, the great artery of the body, E E. This great vessel con-
veys the blood to every part that has life. From all the parts of
the body the blood is gathered again by the extremities of the
veins, and so returns to the point of the auricle from which we
began to trace it. This short preface may make the observations
of the author easily intelligible.]

The circulation of the blood through the bodies
of men and quadrupeds, and the apparatus by
wliich it is carried on, compose a system, and tes-
tify a contrivance, perhaps the best understood of
any part of the animal frame. The lymphatic
system, or the nervous system, may be more sub-
tle and intricate — nay, it is possible that in their
structure they may be even more artificial than
the sanguiferous — but we do not know so much
about them.

The utility of the circulation of the blood I as-
sume as an acknowledged point. One grand pur-
pose is plainly answered by it — the distributing to
every part, every extremity, every nook and corner
of the body, the nourishment which is received into

NATURAL THEOLOGY. 159

it by one aperture. What enters at the mouth finds
its way to the fingers' ends. A more difficult me-
chanical problem could hardly, I think, be propos-
ed, than to discover a method of constantly repair-
ing the waste, and of supplying an accession of
substance to every part of a complicated machine
at the same time.''^

This system presents itself under two views :
first, the disposition of the blood-vessels, i, e., the
laying of the pipes ; and, secondly, the construc-
tion of the engine at the centre, viz., the heart, fur
di-iving the blood through them.

I. The disposition of the blood-vessels, as far as
regards the supply of the body, is like that of the
water-pipes in a city, viz., large and main trunks
branching off by smaller pipes (and these again by
still narrower tubes) in every direction, and tov»^ards
every part in which the fluid which they convey
can be wanted. So far the water-pipes which
serve a town may represent the vessels which carry
the blood from the heart. But there is another
thins necessary to the blood, which is not wanted

CD v' '

for the water ; and that is, the carrying of it back
again to its source. For this office, a reversed sys-
tem of vessels is prepared, which, uniting at their
extremities with the extremities of the first system,
collects the divided and subdivided streamlets,
by first, capillary ramifications into larger branches,

3'' We must refer our reader to the Dissertation in the Appendix
On the Circulation of the Blood and its Uses.

160 NATURAL THEOLOGY.

secondly, by these branches into trunks ; and thus
returns the blood (almost exactly inverting the
order in which it went out) to the fountain whence
its motion proceeded. All which is evident me-
chanism.

The body, therefore, contains two systems of
blood-vessels, arteries and veins. Between the con-
stitution of the systems there are also two differ-
ences, suited to the functions which the systems
have to execute. The blood, in going out, passing
always from wider into naiTOwer tubes; and, in
coming back, from narrower into wider, it is evident
that the impulse and pressure upon the sides of the
blood-vessel will be much greater in one case than
the other. Accordingly, the arteries which carry
out the blood are formed of much tougher and
stronger coats than the veins which bring it back.
That is one difference : the other is still more arti-
ficial, or, if I may so speak, indicates still more
clearly the care and anxiety of the artificer. For-
asmuch as, in the arteries, by reason of the greater
force with which the blood is urged along them, a
wound or rupture would be more dangerous than
in the veins, these vessels are defended from injury,
not only by their texture, but by their situation, and
by every advantage of situation which can be given
to them. They are buried sinuses, or they creep
along grooves made for them in the bones ; for in-
stance, the under edge of the ribs is sloped and fur-
rowed solely for the passage of these vessels. Some-
times they proceed in channels, protected by stout

NATURAL THEOLOGY. 161

parapets on each side, which last description is re-
markable in the bones of the fingers, these being
hollowed out, on the under side, like a scoop, and
with such a concavity, that the finger may be cut
across to the bone, without hurting the artery which
runs along it. At other times, the arteries pass in
canals wrought in the substance, and in the very
middle of the substance, of the bone. This takes
place in the lower jaw ; and is found w^here there
would, otherwise, be danger of compression by
sudden curvature. All this care is wonderful, yet
not more than what the importance of the case re-
quired. To those who venture their lives in a ship,
it has been often said, that there is only an inch-
board between them and death ; but in the body
itself, especially in the arterial system, there is, in
many parts, only a membrane, a skin, a thread.
For which reason, this system lies deep under the
integuments ; wiiereas the veins, in which the mis-
chief that ensues from injuring the coats is much
less, lie in general above the arteries ; come nearer
to the surface ; are more exposed.

It may be further observed concerning the two
systems taken together, that though the arterial,
with its trunk and branches and small twigs, may
be imagined to issue or proceed — in other words,
to grow, from the heart, like a plant from its root,
or the fibres of a leaf from its foot-stalk (which
however, were it so, would be only to resolve one
mechanism into another,) yet the venal, the re-
turning system, can never be formed in this man-

14*

162 NATURAL THEOLOGY.

ner. The arteries might go on shooting out from
their extremities — ?.e.,lengtliening and subdividing
indefinitely; but an inverted system, continually
uniting its streams, instead of dividing, and thus
carrying back what the other system carried out,
could not be referred to the same process.

II. The next thing to be considered is the engine
which works this machinery — viz., the heart. For
our purpose it is unnecessary to ascertain the prin-
ciple upon which the heart acts. Whether it be
irritation excited by the contact of the blood, by the
influx of the nervous fluid, or whatever else be the
cause of its motion, it is something which is capa-
ble of producing, in a living muscular fibre, recip-
rocal contraction and relaxation. This is the power
w^e have to work w^ith ; and the inquiry is, how this
power is applied in the instance before us. There
is provided, in the central part of the body, a hollow
muscle, invested with spiral fibres, running in both
directions, the layers intersecting one another ; in
gome animals, however, appearing to be semicir-
cular rather than spiral. By the contraction of
these fibres, the sides of the muscular cavities are
necessarily squeezed together, so as to force out
from them any fluid which they may at that time
contain : by the relaxation of the same fibres, the
cavities are in their turn dilated, and, of course,
prepared to admit every fluid which may be poured
into them. Into these cavities arc inserted the
great trunks, both of the arteries w^hich carry out
the blood, and of the veins wliich bring it back.

NATURAL THEOLOGY. 1G3

This is a general account of the apparatus ; and
the simplest idea of its action is, that by each con-
traction a portion of blood is forced by a syringe
into the arteries ; and, at each dilatation, an equal
portion is received from the veins. This produces,
at each pulse, a motion, and change in the mass
of blood, to the amount of what the cavity contains,
which in a full-grown human heart I understand
is about an ounce, or two table-spoons full. How
quickly these changes succeed one another, and by
this succession how sufficient they are to support
a stream or circulation throughout the system, may
be understood by the following computation, abridg-
ed from Keill's Anatomy, p. 117, ed. 3: "Each
ventricle will at least contain one ounce of blood.
The heart contracts four thousand times in one
hour: from which it follows, that there pass through
the heart, every hour, four thousand ounces, or three
hundred and fifty pounds of blood. Now the whole
mass of blood is said to be about twenty-five pounds:
so that a quantity of blood, equal to the whole mass
of blood, passes through the heart fourteen times
in one hour, which is about once in every four
minutes."

Consider what an affair this is, when we come
to very large animals. The aorta of a whale is
larger in the bore than the main pipe of the water-
works at London Bridge ; and the water roaring
in its passage through that pipe is inferior, in im-
petus and velocity, to the blood gushing from the
whale's heart. Hear Dr. Hunter's account of the

164 NATURAL THEOLOGY.

dissection of a whale : " The aorta measured a
foot diameter. Ten or fifteen gallons of blood are
thrown out of the heart at a stroke with an im-
mense velocity, through a tube of a foot diameter.
The whole idea fills the mind with wonder."*

The account which we have here stated of the
injection of blood into the arteries by the contrac-
tion, and of the corresponding reception of it
from the veins by the dilatation, of the cavities of
the heart, and of the circulation being thereby
maintained through the blood-vessels of the body,
is true, but imperfect. The heart performs this
office, but it is in conjunction with another of
equal curiosity and importance. It was necessary
that the blood should be successively brought
into contact, or contiguity, or proximity with the
air. I do not know that the chemical reason
upon which this necessity is founded, has been
yet sufficiently explored. It seems to be made
appear, that the atmosphere which we breathe is
a mixture of two kinds of air : one pure and vital,
the other, for the purposes of life, effete, foul, and
noxious f that when we have drawn in our breath
the blood in the lungs imbibes from the air thus
brought into contiguity with it a portion of its

^ The atmosphere contains, in every 100 parts, of oxygen 21
parts ; nitrogen or azote, 79 parts ; carbonic acid gas, a fractional
part.

♦ Dr. Hunter's Account of the Dissection of a whale— (Phil.
Trans.)

NATURAL THEOLOGY. 1G5

pure ingredient, and at the same time gives out
the effete or corrupt air which it contained, and
which is carried away, along with the halitus,
every time we expire. At least, by comparing
the air which is breathed from the lungs with the
air which enters the lungs, it is found to have lost
some of its pure part, and to have brought away
with it an addition of its impure part. Whether
these experiments satisfy the question as to the
need which the blood stands in of being visited
by continual accesses of air, is not for us to in-
quii-e into, nor material to our argument : it is
sufficient to know, that, in the constitution of
most animals, such a necessity exists, and that
the air, by some means or other, must be intro-
duced into a near communication with the blood.^
The lungs of animals are constructed for this

*The most simple view, and the best supported, is this — thnt
the dark venous blood which is returning from the circulation
through the body is loaded with carbon. When it is carried to
the right side of the heart, and from that into the lungs, the
branches of the pulmonary artery are distributed in great minute-
ness on cells infinite in number. These cells communicate with
the extreme branches of the windpipe ; and as the atmosphere is
received into these cells, the circulating blood comes to be ex-
posed to its influence ; for neither the coats of the minute ves-
sels which contain the blood, nor the fine membrane of the cells
which contain the air, prevents the influence of the atmosphere
upon the blood. The carbon of the blood meeting the oxygen in
•the atmosphere, forms carbonic acid gas ; and the air expelled in
expiration, thus loaded, carries away, of course, a portion of mois-
ture by exhalation. (See the Dissertation entitled — On the Cir-
culation. Appendix.)

166 NATURAL THEOLOGY.

purpose. They consist of blood-vessels and air-
vessels, lying close to each other ; and whenever
there is a branch of the trachea or windpipe,
there is a branch accompanying it of the vein and
artery, and the air-vessel is always in the middle
between the blood-vessels.* The internal sur-
face of these vessels, upon which the application
of the air to the blood depends, would, if collect-
ed and expanded, be, in a man, equal to a super-
ficies of fifteen feet square. Now, in order to
give the blood in its course the benefit of this or-
ganization, (and this is the part of the subject
with which we are chiefly concerned,) the follow-
ing operation takes place. As soon as the blood
is received by the heart from the veins of the
body, and before that is sent out again into its
arteries, it is carried, by the force of the contrac-
tion of the heart, and by means of a separate and
supplementary artery, to the lungs, and made to
enter the vessels of the lungs ; from which, after
it has undergone the action, whatever it be, of
that viscus, it is brought back by a large vein
once more to the heart, in order, when thus con-
cocted and prepared, to be thence distributed
anew into the system. This assigns to the heart
a double office. The pulmonary circulation is a
system within a system ; and one action of the
heart is the origin of both.

For this complicated function four cavities
become necessary, and four are accordingly pro-

* Kcill's Anatomy, p. 121.

NATURAL THEOLOGY.

167

[The figure represents the two sides of the heart separated :
that to the left of the figure, but on the right side of the body, con-
taining the venous blood which must pass through the lungs to
serve the purposes of the economy ; and that on the left side, con-
taining arterial blood, which is sent out into the body. Man, and
all animals of warm blood, have the whole mass of blood passin-;;
through the lungs, and a double heart, as here represented, each
consisting of a vein, an auricle, a ventricle, and an artery. Tho
arrows point out the course of the circulation.]

168 NATURAL THEOLOGY.

vided ; two called ventricles : which send out the
blood, viz., one into the lungs, in the first instance ;
the other into the mass, after it has returned from
the lungs ; two others also, called auricles, which
receive the blood from the veins, viz., one, as it
comes immediately from the body ; the other, as
the same blood comes a second time after its cir-
culation through the lungs. So that there are two
receiving cavities, and two forcing cavities. The
structure of the heart has reference to the lungs ;
for without the lungs, one of each would have
been sufficient. The translation of the blood in
the heart itself is after this manner. The receiv-
ing cavities respectively communicate with the
forcing cavities, and, by their contraction, unload
the received blood into them. The forcing cavi-
ties, when it is their turn to contract, compel the
same blood into the mouths of the arteries.

The account here given will not convey to a
reader ignorant of anatomy any thing like an ac-
curate notion of the form, action, or use of the
parts, (nor can any short and popular account do
this,) but it is abundantly sufficient to testify
contrivance ; and although imperfect, being true
as far as it goes, may be relied upon for the only
purpose for which we offer it — the purpose of
this conclusion.

" The wisdom of the Creator,'' saith Ham-
burgher, " is in nothing seen more gloriously than
in the heart." And how well doth it execute its
office ! An anatomist, who understood the struc-

NATURAL THEOLOGY.

1G9

ture of the heart, might say beforehand that it
would play: but he would expect, I think, from
the complexity of its mechanism, and the delicacy
of many of its parts, that it should always be
liable to derangement, or that it would soon work
itself out. Yet shall this wonderful machine go,
night and day, for eighty years together, at the
rate of a hundred thousand strokes every twenty
four hours, having, at every stroke, a great resist-
ance to overcome ; and shall continue this action
for this length of time, without disorder and with-
out weariness !

[This figure will assist the explanation of the following pages.
It presents a section of the ventricle and the artery. Suppose that
the blood enters in the direction of the arrow, it passes between
two valves of very particular construction. They are of a trian-
gular shape, and held out by little cords, which are called the
cord<B ttndinea. These cords are attached to muscles, which,
from their appearance, are called columnar carnece; and these

15

170 NATURAL THEOLOGY

fibres are continuous with the fibrous substance of the heart itself.
Now when the ventricle is distended with blood, the valves are
drawn by their tendons in such a manner as almost to close the
orifice; and certainly so to dispose them, that the instant the
blood takes a direction backward into the vein by the contraction
of the ventricle, they fall together, and like a flood-gate stop the
current in that direction. Were there no cor dm tendinece, or coluntr
nee, carnece, these valves' would be floated back into the auricle, and
lose their office. But the most adinirable part of the contrivance
is, that the columncR carnece receiving the same impulse to contract
as the walls of the heart itself, act at the same instant with it; and
by contracting in proportion as the walls approach each other,
they hold the margins of the valves like the leeches of a sail when
bagged by the wind. The blood being prevented passing back-
ward is urged into the great artery still in the direction of the ar-
row. And now it will be observed that the artery must be dilated
when the heart contracts. And the artery itself being both elastic
and muscular, reacting upon this impulse, it will contract while
the ventricle is dilating. The blood would fall back from the
great artery into the ventricle, were it not again prevented by the
mechanical intervention of valves, a represents the semilunar
valve of the aOrta at the root of that great artery ; and it is a sur-
prising thing to see how offices so nearly alike are performed by a
mechanism entirely diflTerent. This valve consists of three little
bags, which are driven up by the force of the blood in the natural
course of the circulation ; but when, by the action of the aOrta,
the blood makes a motion backwards, it fills these three little
bags, and they fall together, and prevent the blood flowing back
into the heart.]

But further : from the account which has been
given of the mechanism of the heart, it is evident
that it must require the interposition of valves;
that the success indeed of its action must depend
upon these ; for when any one of its cavities con-
tracts, the necessary tendency of the force will
be to drive the enclosed blood, not only into the

NATURAL THEOLOGY. 171

mouth of the artery where it ought to go, but also
back again into the mouth of the vein from which
it flowed. In like manner, when by the relaxa-
tion of the fibres the same cavity is dilated, the
blood would not only run into it from the vein,
which was the course intended, but back from the
artery, through which it ought to be moving for-
ward. The way of preventing a reflux of the
fluid, in both these cases, is to fix valves, which,
like flood-gates, may open a way to the stream in
one direction, and shut up the passage against it
in another. The heart, constituted as it is, can no
more work without valves than a pump can.
When the piston descends in a pump, if it were
not for the stoppage by the valve beneath, the
motion would only thrust down the water which
it had before drawn up. A similar consequence
would frustrate the action of the heart. Valves,
therefore, properly disposed, i, e., properly with
respect to the course of the blood which it is ne-
cessary to promote, are essential to the contri*
vance. And valves so disposed are accordingly
provided. A valve is placed in the communica-
tion between each auricle and its ventricle, lest,
when the ventricle contracts, part of the blood
should get back again into the auricle, instead of
the whole entering, as it ought to do,- the mouth
of the artery- A valve is also fixed at the mouth
of each of the great arteries which take the blood
from the heart ; leaving the passage free, so long
as the blood holds its proper course forward;

172 NATURAL THEOLOGY.

closing it, whenever the blood, in consequence of
the relaxation of the ventricle, would attempt to
flow back. There is some variety in the con-
struction of these valves, though all the valves of
the body act nearly upon the same principle, and
are destined to the same use. In general they
consist of a thin membrane, lying close to the side
of the vessel, and consequently allowing an open
passage while the stream runs one way, but thrust
out from the side by the fluid getting behind it,
and opposing the passage of the blood, when it
w^ould flow the other way. Where more than one
membrane is employed, the difterent membranes
only compose one valve. Their joint action fulfils
the office of a valve : for instance ; over the en-
trance of the right auricle of the heart into the
right ventricle, three of these skins or membranes
are fixed, of a triangular figure, the bases of the
triangles fastened to the flesh ; the sides and
summits loose ; but, though loose, connected by
threads of a determinate length, with certain
small fleshy prominences adjoining. The effect
of this construction is, that, when the ventricle
contracts, the blood endeavouring to escape in all
dii'ections, and amongst other directions pressing
upwards, gets between these membranes and the
sides of the passage ; and thereby forces them up
into such a position, as that together they consti-
tute, when raised, a hollow cone, (the strings be-
fore spoken of hindering them from proceeding
or separating further ;) which cone, entirely occu-

NATURAL THEOLOGY. 173

pying the passage, prevents the return of the blood
into the auricle. A shorter account of the matter
may be this : so long as the blood proceeds in its
proper course, the membranes which compose
the valve are pressed close to the side of the ves-
sel, and occasion no impediment to the circula-
tion: when the blood would regurgitate, they are
raised from the side of the vessel, and, meeting in
the middle of its cavity, shut up the channel.
Can any one doubt of contrivance here; or is it
possible to shut our eyes against the proof of it V

NO

■*" We cannot resist following up these observations with some
minute notices of the appropriate structure. A sail distended
with the wind would be torn up, were not the margins secured :
accordingly, the canvass is folded over a strong cord, which is
called the bolt-rope. So the margins of these semi-lunar valves
are as finely finished as any sheet from the dock-yard. There is
a ligament which runs along the margin, and strengthens it to
sustain the impulse of the back-stroke of the artery. And were
those cordoi tendinece, which we have described as like the leeches
of a sail, attached to the corner of the mitral valve without further
security, they would be torn off on the first pulsation. But as the
leeches are secured to the bolt-ropes of the sail, so are the corda
tendmece continued into firm ligamentous cords which strengthen
the valves. J

Our author says well, that the valve is thrown down on the side
of the artery when the blood is in its course. But were this really
the case, the refluent blood would not easily catch the edge of the
valve to throw it up. Now this difficulty is met very curiously,
and in two different modes. The cordae tendin(B prevent the
margins of the mitral valve within the ventricle from flapping close
against the side of the cavity; and as to the semi-lunar valves, at
the root of the great artery, they are prevented falling against the
walls in another mode : the section of the artery at its root is not
a regular circle ; but it is formed into three little bags or sinusee,

15*

174 NATURAL THEOLOGY.

This valve, also, is not more curious in its struc-
ture, than it is important in its office. Upon the
play of the valve, even upon the proportional
length of the strings or fibres which check the
ascent of the membranes, depends, as it should
seem, nothing less than the life itself of the ani-

and as each of the three valves has a httle sinus behind it, its mar-
gin never reaches the wall of the artery. The consequence of
which is, that in the instant that the column of blood takes a re-
trograde direction, the margins of the valve are caught, and they
are thrown up to close the passage. Nothing can be more admi-
rably mechanical.

Since our author has so properly insisted upon the mechanism
of the heart as the very strength of his argument, we shall men-
tion one circumstance more as showing what may be called the
perfection of the workmanship. It has been explained that the
valves of the great artery consist oftliree semicircular membranes.
Now if we consider the effect of these three semicircles meeting,
there must be a triangular space in their centre, an imperfection in
the point of their union as it were. To remedy this defect, on the
centre of the margin of each valve, there is a little body like a
small excrescence or tongue : and when these three bodies meet,
they exactly fill up the triangular space which is left in the centre
of the three semicircles. It is as if an ingenious workman had
contrived a thing the most apposite to remedy a defect.

NATURAL THEOLOGY. 175

mal. We may here likewise repeat, what we
before observed concerning some of the ligaments
of the body, that they could not be formed by any
action of the parts themselves. There are cases
in which, although good uses appear to arise from
the shape or configuration of a part, yet that shape
or configuration itself may seem to be produced
by the action of the part, or by the action or pres-
sure of adjoining parts. Thus the bend and the
internal smooth concavity of the ribs may be at-
tributed to the equal pressure of the soft bowels ;
the particular shape of some bones and joints, to
the traction of the annexed muscles, or to the po-
sition of contiguous muscles. But valves could
not be so formed. Action and pressure are all
against them. The blood, in its proper course,
has no tendency to produce such things ; and in
its improper or reflected current has a tendency
to prevent their production. Whilst we see,
therefore, the use and necessity of this machinery,
we can look to no other account of its origin or
formation than the intending mind of a Creator.
Nor can we without admiration reflect, that such
thin membranes, such weak and tender instru-
ments, as these valves are, should be able to hold
out for seventy or eighty years.

Here also we cannot consider but with grati-
tude, how happy it is that our vital motions are
involuntary. We should have enough to do, if
we had to keep our hearts beating and our
stomachs at work. Did these things depend, we

176 NATURAL THEOLOGY.

will not say upon our effort, but upon our bidding,
our care, or our attention, they would leave us
leisure for nothing else. We must have been
continually upon the watch, and continually in
fear ; nor would this constitution have allowed of
sleep.

It might perhaps be expected, that an organ
so precious, of such central and primary import-
ance as the heart is, should be defended by a
case. The fact is, that a membranous purse or
bag, made of strong, tough materials, is provided
for it : holding the heart within its cavity : sitting
loosely and easily about it; guarding its sub-
stance, without confining its motion ; and contain-
ing likewise a spoonful or two of water, just
sufficient to keep the surface of the heart in a
state of suppleness and moisture. How should
such a loose covering be generated by the action
of the heart ? Does not the enclosing of it in a
sack, answering no other purpose but that enclo-
sure, show the care that has been taken of its pre-
servation ?

One use of the circulation of the blood probably
(amongst other uses) is, to distribute nourishment
to the different parts of the body. How minute
and multiplied the ramifications of the blood-ves-
sels for that purpose are ; and how thickly spread
over at least the superficies of the body, is proved
by the single observation, that we cannot prick
the point of a pin into the flesh without drawing
blood, i. e. without finding a blood-vessel. Nor

NATURAL THEOLOGY. 177

internally is their diffusion less universal. Blood-
vessels run along the surface of membranes, per-
vade the substance of muscles, penetrate the
bones. Even into every tooth we trace, through
a small hole in the root, an artery to feed the
bone, as well as a vein to bring back the spare
blood from it ; both which, with the addition of
an accompanying nerve, form a thread only a
little thicker than a horse-hair.

Wherefore, when the nourishment taken in at
the mouth has once reached and mixed itself with
the blood, every part of the body is in the way of
being supplied with it. And this introduces an-
other grand topic, namely, the manner in which
the aliment gets into the hlood ; which is a sub-
ject distinct from the preceding, and brings us to
the consideration of another entire system of
vessels.

III. For this necessary part of the animal econ-
omy an apparatus is provided in a great measure
capable of being what anatomists call demonstra-
ted, that is, shown in the dead body ; and a line
or course of conveyance, which we can pursue
by our examinations.

First, the food descends by a wide passage into
the intestines, undergoing two great preparations
on its way : one in the mouth by mastication and
moisture — (can it be doubted with what design
the teeth were placed in the road to the stomach,
or that there was choice in fixing them in this sit-
uation?)— the other by digestion in the stomach

178 NATURAL THEOLOGY.

itself. Of this last surprising dissolution I say
nothing; because it is chemistry, and I am en-
deavouring to display mechanism. The figure and
position of the stomach (I speak all along with a
reference to the human organ,) are calculated
for detaining the food long enough for the action
of its digestive juice. It has the shape of the
pouch of a bagpipe ; lies across the body ; and the
pylorus, or passage by which the food leaves it, is
somewhat higher in the body than the cardia or
orifice by which it enters ; so that it is by the con-
traction of the muscular coat of the stomach that
the contents, after having undergone the applica-
tion of the gastric menstruum, are gradually
pressed out. In dogs and cats, this action of the
coats of the stomach has been displayed to the
eye. It is a slow and gentle undulation, propaga-
ted from one orifice of the stomach to the other.
For the same reason that I omitted, for the pre-
sent, offering any observation upon the digestive
fluid, I shall say nothing concerning the bile or
the pancreatic juice, further than to observe upon
the mechanism, viz., that from the glands in which
these secretions are elaborated pipes are laid into
the first of the intestines, through which pipes the
product of each gland flows into that bowel, and
is there mixed with the aliment as soon almost as
it passes the stomach ; adding also as a remark,
how grievously this same bile offends the stomach
itself, yet cherishes the vessel that hes next to it.
Secondly. We have now the aliment in the in-

NATURAL THEOLOGY. 179

testines converted into pulp; and though lately
consisting of ten different viands, reduced to near-
ly a uniform substance, and to a state fitted for
yielding its essence, which is called chyle, but
which is milk, or more nearly resembling milk
than any other liquor with which it can be com-
pared. For the straining off this fluid from the
digested aliment in the course of its long progress
through the body, myriads of capillary tubes, i. c,
pipes as small as hairs, open their orifices into the
cavity of every part of the intestines. These
tubes, which are so fine and slender as not to be
visible unless when distended with chyle, soon
unite into larger branches. The pipes formed by
this union terminate in glands, from which other
pipes, of a still larger diameter, arising, carry the
chyle from all parts into a common reservoir or
receptacle. This receptacle is a bag of size
enough to hold about two table-spoons full ; and
from this vessel a duct or main pipe proceeds,
climbing up the back part of the chest, and after-
wards creeping along the gullet till it reach the
neck. Here it meets the river ; here it discharges
itself into a large vein, which soon conveys the
chyle, now flowing along with the old blood, to
the heart. This whole route can be exhibited to
the eye; nothing is left to be supplied by imagi-
nation or conjecture. Now, besides the subser-
viency of this structure, collectively considered,
to a manifest and necessary purpose, we may re-
mark two or three separate particulars in it, which

180 NATURAL THEOLOGY,

show, not only the contrivance, but the perfection
of it. We may remark, first, the length of the in-
testines, which, in the human subject, is six times
that of the body. Simply for a passage, these vo-
luminous bowels, this prolixity of gut, seems in
nowise necessary; but in order to allow time and
space for the successive extraction of the chyle
from the digestive aliment, namely, that the chyle
which escapes the lacteals of one part of the guts
may be taken up by those of some other part, the
length of the canal is of evident use and condu-
civeness. Secondly, we must also remark their
peristaltic motion, which is made up of contrac-
tions following one another like waves upon the
surface of a fluid, and not unlike what we observe
in the body of an earthworm crawling along the
ground, and which is effected by the joint action
of longitudinal and of spiral, or rather perhaps of
a great number of separate semicirculg.r fibres.
This curious action pushes forward the grosser
part of the aliment, at the same time that the
more subtile parts, which we call chyle, are, by a
series of gentle compressions, squeezed into the
narrow orifices of the lacteal veins. Thirdly, it
was necessary that these tubes, which we denomi»
nate lacteals, or their mouths at least, should be
made as narrow as possible, in order to deny ad-
mission into the blood to any particle which is of
size enough to make a lodgement afterwards in the
small arteries, and thereby to obstruct the circu-
lation ; and it was also necessary that this ex-

NATURAL THEOLOGY. 181

treme tenuity should be compensated by multi-
tude ; for a large quantity of chyle (in ordinary
constitutions not less, it has been computed, than
two or three quarts in a day) is, by some means
or other, to be passed through them. According-
ly, we find the number of the lacteals exceeding
all powers of computation, and their pipes so fine
and slender as not to be visible, unless filled, to
the naked eye, and their orifices, which open into
the intestines, so small as not to be discernible
even by the best microscope. Fourthly, the main
pipe, which carries the chyle from the reservoir
to the blood, viz., the thoracic duct, being fixed in
an almost upright position, and wanting that ad-
vantage of propulsion which the arteries possess,
is furnished with a succession of valves to check
the ascending fluid, when once it has passed them,
from falling back. These valves look upwards,
so as to leave the ascent free, but to prevent the
return of the chyle, if, for want of sufficient force
to push it on, its weight should at any time cause
it to descend. Fifthly, the chyle enters the blood
in an odd place, but perhaps the most commo-
dious place possible, viz., at a large vein in the
neck, so situated with respect to the circulation as
speedily to bring the mixture to the heart. And
this seems to be a circumstance of great moment;
for had the chyle entered the blood at an artery
or at a distant vein, the fluid composed of the old
and the new materials must have performed a
considerable part of the circulation before it re-

16

182 NATURAL THEOLOGY.

ceived that churning in the lungs which is proba-
bly necessary for the intimate and perfect union
of the old blood with the recent chyle. Who
could have dreamt of a communication between
the cavity of the intestines and the left great vein
of the neck ? Who could have suspected that this
communication should be the medium through
which all nourishment is derived to the body, or
this the place where, by a side inlet, the impor-
tant junction is formed between the blood and the
material which feeds it ?

We postponed the consideration of digestion,
lest it should interrupt us in tracing the course of
the food to the blood ; but in treating of the ali-
mentary system, so principal a part of the process
cannot be omitted.

Of the gastric juice, the immediate agent by
which that change which food undergoes in our
stomachs is effected, we shall take our account
from the numerous, careful, and varied experi-
ments of the Abbe Spallanzani.

1. It is not a simple diluent, but a real solvent.
A quarter of an ounce of beef had scarcely touch-
ed the stomach of a crow, when the solution
began.

2. It has not the nature of saliva; it has not the
nature of bile ; but is distinct from both. By ex-
periments out of the body, it appears that neither
of these secretions acts upon alimentary substan-
ces in the same manner as the gastric juice acts.

3. Digestion is not putrefaction ; for the digest-

NATURAL THEOLOGY. 183

ing fluid resists putrefaction most pertinaciously ;
nay, not only checks its further progress, but re-
stores putrid substances.

4. It is not ?i fermentative process ; for the solu-
tion begins at the surface, and proceeds towards
the centre, contrary to the order in which fermen-
tation acts and spreads.

5. It is not the digestion of heat ; for the cold
maw of a cod or sturgeon will dissolve the shells
of crabs or lobsters, harder than the sides of the
stomach which contains them.

In a word, animal digestion carries about it the
marks of being a power and a process completely
sui generis, distinct from every other, at least from
every chemical process with which we are ac-
quainted. And the most wonderful thing about it
is its appropriation — its subserviency to the par-
ticular economy of each animal. The gastric juice
of an owl, falcon, or kite will not touch grain ; no,
not even to finish the macerated and half-digested
pulse which is left in the crops of the sparrows
that the bird devours. In poultry, the trituration of
the gizzard, and the gastric juice, conspire in the
work of digestion. The gastric juice will not dis-
solve the grain whilst it is whole. Entire grains
of barley, enclosed in tubes or spherules, are not
affected by it. But if the same grain be by any
means broken or ground, the gastric juice imme-
diately lays hold of it. Here then is wanted, and
here we find, a combination of mechanism and

184 NATURAL THEOLOGY,

chemistiy.^^ For the preparatory grinding the giz-
zard lends its mill ; and as all mill-work should be
strong, its structure is so beyond that of any other
muscle belonging to the animal. The internal coat
also, or lining of the gizzard, is, fo?^the same pur-
pose, hard and cartilaginous. But, forasmuch as
this is not the sort of animal substance suited for
the reception of glands, or for secretion, the gastric
juice, in this family, is not supplied, as in membran-
ous stomachs, by the stomach itself, but by the gul-
let, in which the feeding -glands are placed, and
from which it trickles down into the stomach.

In sheep, the gastric fluid has no effect in digest-
ing plants, unless theij have been previously masti-
cated. It only produces a slight maceration, nearly
such as common water would produce, in a degree
of heat somewhat exceeding the medium tempera-
ture of the atmosphere. But, provided that the
plant has been reduced to pieces by chewing, the
gastric juice then proceeds with it, first, by soften-
ing its substance ; next, by destroying its natural
consistency ; and, lastly, by dissolving it so com-
pletely as not even to spare the toughest and most
stringy parts, such as the nerves of the leaves.

So far our accurate and indefatigable Abbe. Dr.
Stevens, of Edinburgh, in L777, found, by experi-
ments tried with perforated balls, that the gastric

** One of the many modes by which seeds are carried to a dis-
tance, and Sir Joseph Banks gave us reason to bcheve that it serv-
ed as a preparation for sowing, as seeds so carried germinated
ooner.

NATURAL THEOLOGY. 185

juice of the sheep and the ox speedily dissolved
vegetables, but made no impression upon beef,
mutton, and other animal bodies. Mr. Hunter dis-
covered a property of this fluid, of a most curious
kind — viz., that in the stomachs of animals which
feed upon flesh, irresistibly as this fluid acts upon
animal substances, it is only upon the ^Zea^Z substance
that it operates at all. The living fibre suffers no
injury from lying in contact with it. Worms and
insects are found alive in the stomachs of such ani-
mals. The coats of the human stomach, in a healthy
state, are insensible to its presence ; yet in cases of
sudden death, (wherein the gastric juice, not hav-
ing been weakened by disease, retains its activity,)
it has been known to eat a hole through the bowel
which contains it.* How nice is this discrimina-
tion of action, yet how necessary!

But to return to our hydraulics.

IV. The gall-bladder is a very remarkable con-
trivance. It is the reservoir of a canal. It does
not form the channel itself — i, c, the direct com-
munication between the liver atid the intestine,
which is by another passage — viz., the ductus he-
paticus, continued under the name of the ductus
communis ; but it lies adjacent to this channel, join-
ing it by a duct of its own, the ductus cysticus :
by which structure it is enabled, as occasion may
require, to add its contents to and increase the flow
of bile into the the duodenum. And the position

* Phil. Trans, vol. Ixii. p. 447.
*16

186 NATURAL THEOLOGY.

of the gall-bladder is such as to apply this struc-
ture to the best advantage. In its natural situation,
it touches the exterior surface of the stomach, and
consequently is compressed by the distention of
that vessel : the effect of which compression is to
force out from the bag, and send into the duodenum,
an extraordinary quantity of bile, to meet the ex-
traordinary demand which the repletion of the
stomach by food is about to occasion.* Cheselden
describesf the gall-bladder as seated against the
duodenum, and thereby liable to have its fluid press-
ed out by the passage of the aliment through that
cavity, which likewise will have the effect of caus-
ing it to be received into the intestine at a right
time and in a due proportion.

There may be other purposes answered by this
contrivance, and it is probable that there are. The
contents of the gall-bladder are not exactly of the
same kind as what passes from the liver through
the direct passage. J It is possible that the gall
may be changed, and for some purposes meliorat-
ed, by keeping.''^

The entrance of the gall-duct into the duodenum
furnishes another observation. Whenever either

■'^ On this passage some remaiks on the absence of the gall-blad-
der ill certain animals might be required ; but the reader may turn
to the note in the Appendix on the stomach of the horse.

* Keill's Anat. p. 64. f Anat. p. 164.

I Keill, (from Malpighius,) p. 63.

NATURAL THEOLOGY. 187

smaller lubes are inserted into larger tubes, or tubes
into vessels and cavities, such receiving tubes, ves-
sels, or cavities, being subject to muscular con-
striction, we always find a contrivance to prevent
resuro-itation. In some cases valves are used ; in
other cases, amongst which is that now before us,;
a different expedient is resorted to, which may be
thus described : the gall-duct enters the duodenum
obliquely ; after it has pierced the first coat, it runs
near two fingers' breadth between the coats before
it opens into the cavity of the intestine.* The same
contrivance is used in another part, where there is
exactly the same occasion for it, viz., in the inser-
tion of the ureters in the bladder. These enter
the bladder near its neck, running obliquely for the
space of an inch between its coats. f It is, in both
cases, suflficiently evident that this structure has a
necessary mechanical tendency to resist regurgita-
tion ; for whatever force acts in such a direction
as to urge the fluid back into the orifices of the
tubes, must, at the same time, stretch the coats of
the vessels, and thereby compress that part of the
tube wdiich is included between them.

V. Amongst the vessels of the human body, the
pipe which conveys the saliva from the place where
it is made to the place where it is wanted deserves
to be reckoned amongst the most intelligible pieces
of mechanism with which we are acquainted. The
saliva, we all know, is used in the mouth ; but much

* Keill's Anat. p. 62. f Ches. Anat. p. 260.

188 NATURAL THEOLOGY.

of it is produced on the outside of the cheek by the
parotid gland, which hes between the ear and the
angle of the lower jaw. In order to carry the
secreted juice to its destination, there is laid from
the gland on the outside a pipe about the thickness
of a wheat straw, and about three fingers' breadth
in length, which, after riding over the masseter mus-
cle, bores for itself a hole through the very middle
of the cheek, enters by that hole, w^hich is a com-
plete perforation of the buccinator muscle, in to the
mouth, and there discharges its fluid very copiously.
VI. Another exquisite structure, differing, in-
deed, from the four preceding instances in that it
does not relate to the conveyance of fluids, but
still belonging, like these, to the class of pipes or
conduits of the body, is seen in the larynx. We
all know that there go down the throat two pipes,
one leading to the stomach, the other to the lungs
— the one being the passage for the food, the
other for the breath and voice : we know also,
that both these passages open into the bottom of
the mouth — the gullet, necessarily, for the con-
veyance of food, and the windpipe, for speech and
the modulation of sound, not much less so : there-
fore the difficulty was, the passages being so con-
tiguous, to prevent the food, especially the liquids,
which we swallow into the stomach from entering
the windpipe, i. e., the road to the lungs — the
consequence of which error, when it does happen,
is perceived by the convulsive throes that are in-
stantly produced. This business, which is very

NATURAL THEOLOGY. 189

nice, is managed in this manner. The gullet (the
passage for food) opens into the mouth like the
cone or upper part of a funnel, the capacity of
which forms indeed the bottom of the mouth.
Into the side of this funnel, at the part which lies
the lowest, enters the windpipe by a chink or
slit, with a lid or flap, hke a little tongue, accu-
rately fitted to the orifice. The solids or liquids
which we swallow pass over this lid or flap as they
descend by the funnel into the gullet. Both the
weight of the food and the action of the muscles
concerned in swallowing contribute to keep the
lid close down upon the aperture whilst any thing
is passing ; whereas, by means of its natural car-
tilaginous spring, it raises itself a little as soon as
the food is passed, thereby allowing a free inlet
and outlet for the respiration of air by the lungs.
Such is its structure ; and we may here remark
the almost complete success of the expedient, viz.,
how seldom it fails of its purpose compared with
the number of instances in which it fulfils it. Re-
flect hovr frequently we swallow, how constantly.
we breathe. In a city feast, for example, what
deglutition, what anhelation ! yet does this httle
cartilage, the epiglottis, so effectually interpose
its office, so securely guard the entrance of the
windpipe, that whilst morsel after morsel, draught
after draught, are coursing one another over it^
an accident of a crumb or a drop slipping into
this passage, (which, nevertheless, must be opened
for the breath every second of time,) excites in the

190 NATURAL THEOLOGY.

whole company, not only alarm by its danger, but
surprise by its novelty. Not two guests are
clioked in a century.

There is no room for pretending that the action
of the parts may have gradually formed the epi-
glottis : I do not mean in the same individual,
but in a succession of generations. Not only the
action of the parts has no such tendency, but the
animal could not live, nor consequently the parts
act, either without it or with it in a half-formed
state. The species was not to wait for the gra-
dual formation or expansion of a part which was
from the first necessary to the life of the indi-
vidual.

Not only is the larynx curious, but the whole
windpipe possesses a structure adapted to its
peculiar office. It is made up (as any one may
perceive by putting his fingers to his throat) of
stout cartilaginous ringlets, placed at small and
equal distances from one another. Now this is
not the case with any other of the numerous con-
duits of the body. The use of these cartilages is
to keep the passage for the air constantly open,
which they do mechanically. A pipe with soft
membranous coats, liable to collapse and close
when empty, would not have answered here ;
although this be the general vascular structure,
and a structure which serves very well for those
tubes which are kept in a state of perpetual dis
tention by the fluid they enclose, or which afford
a passage to solid and proti'uding substances.

NATURAL THEOLOGY. 191

Nevertheless, (which is another particularity-
well worthy of notice,) these rings are not com-
plete— that is, are not cartilaginous and stiff all
round ; but their hinder part, which is contiguous
to the gullet, is membranous and soft, easily
yielding to the distentions of that organ occasion-
ed by the descent of solid food. The same rings
are also bevelled off at the upper and lower edges,
the better to close upon one another when the
trachea is compressed or shortened.

The constitution of the trachea may suggest
likewise another reflection. The membrane which
lines its inside is perhaps the most sensible, irri-
table membrane of the body. It rejects the touch
of a crumb of bread, or a drop of water, with a
spasm which convulses the whole frame ; yet, left
to itself and its proper office, the intromission of
air alone, nothing can be so quiet. It does not
even make itself felt ; a man does not know that
he has a trachea. This capacity of perceiving with
such acuteness, this impatience of offence, yet per-
fect rest and ease when let alone, are properties,
one would have thought, not likely to reside in
the same subject. It is to the junction, however,
of these almost inconsistent qualities, in this, as
well as in some other delicate parts of the body,
that we owe our safety and our comfort — our
safety to their sensibility, our comfort to their re-
pose^^

^ Our author touches here upon the sensibilities which govern
the motions of the chest — a subject which might be enlarged

192 NATURAL THEOLOGY.

The larynx, or rather the whole windpipe taken
together, (for the larynx is only the upper part of
the windpipe,) besides its other uses, is also a
musical instrument — that is to say, it '\^ mechanism
expressly adapted to the modulation of sound ;
for it has been found upon trial, that, by relaxing
or tightening the tendinous bands at the extre-
mity of the wind-pipe, and blowing in at the other
end, all the cries and notes might be produced of
which the living animal was capable. It can be
sounded just as a pipe or flute is sounded.

upon to fill a volume. But considering the object of this work,
we ought not to omit the occasion of observing the union of a
property of life with the most complex mechanical structure im-
aginable. We have seen, in former notes, that for the grand and
vital purpose of decarbonizing the blood, the atmospheric air must
be drawn deep into the lungs ; and the problem is, to permit the
vital air to pass, and yet prevent foreign matter from finding ac-
cess. On this subject there is a note in the Appendix. But the
more remarkable circumstance in connexion with the statement
in the text is, that the whole of this apparatus for respiration is
taken from the governance of the will, and placed under a power
more constantly vigilant and more absolutely peremptory. The
sensibility about the glottis holds in control a hundred muscles ;
and while it excites the action, directs the force of the stream of
expired air with extraordinary exactness to the very point where
the irritating matter lodges, be it in the passages of the throat, oi*
in the cavities of the nose. There are many instances of the
same kind in the economy of the frame, where actions are ex-
cited by sensibilities seated in certain spots, some of them attend-
ed with suffering, by which our voluntary efforts are brought in
aid, and others where there is neither sensation nor volition, and
yet the muscles are controlled and regulated, and the offices per-
formed, witli undeviating precision.

NATURAL THEOLOGY. 193

Birds, says Bonnet, have, at the lower end of
the windpipe, a conformation like the reed of a
hautboy, for the modulation of their notes. A
tuneful bird is a ventriloquist. The seat of the
song is in the breast.

The use of the lungs in the system has been
said to be obscure ; one use, however, is plain,
though, in some sense, external to the system,
and that is, the formation, in conjunction with
the larynx, of voice and speech. They are, to
animal utterance, what the bellows are to the
organ." ^^

For the sake of method, we have considered
animal bodies under three divisions ; their bones,
their muscles, and their vessels ; and we have
stated our observations upon these parts sepa-
rately. But this is to diminish the strength of
the argument. The wisdom of the Creator is
seen, not in their separate but their collective
action ; in their mutual subserviency and depen-
dence : in their contributing together to one effect
and one use. It has been said, that a man can-
not lift his hand to his head without finding
enough to convince him of the existence of a God.
And it is well said ; for he has only to reflect,

^ The subject admits of a much more extensive application of
physical science ; and one division of it will be found treated in
{he Appendix.

17

194 NATURAL THEOLOGY.

familiar as this action is, and simple as it seems
to be, how many things are requisite for the per-
forming of it ; how many things which we under-
stand, to say nothing of many more, probably,
which we do not : viz., first, a long, hard, strong
cylinder, in order to give to the arm its firmness
and tension ; but which, being rigid, and, in its
substance, inflexible, can only turn upon joints ;
secondly, therefore, joints for this purpose ; one
at the shoulder to raise the arm, another at the
elbow to bend it ; these joints continually fed
with a soft mucilage to make the parts slip easily
upon one another, and holden together by strong
braces, to keep them in their position : then,
thirdly, strings and wires — i. e., muscles and ten-
dons — artificially inserted, for the purpose of
drawing the bones in the directions in which the
joints allow them to move. Hitherto we seem to
understand the mechanism pretty well ; and, un-
derstanding this, we possess enough for our con-
clusion : Nevertheless, we have hitherto only a
machine standing still — a dead organization — an
apparatus. To put the system in a state of ac-
tivity, to set it at work, a further provision is
necessary — viz., a communication with the brain
by means of nerves. We know the existence of
this communication, because we can see the com-
municating threads, and can trace them to the
brain : its necessity we also know, because if the
thread be cut, if the communication be intercept-
ed, the muscle becomes paralj^ic ; but beyond

NATURAL THEOLOGY. 195

this we know little, the organization being too
minute and subtile for our inspection.

To what has been enumerated, as officiating in
the single act of a man's raising his hand to his
head, must be added likewise all that is necessary
and all that contributes to the growth, nourish-
ment, and sustentation of the limb, the repair of
its waste, the preservation of its health : such as
the circulation of the blood through every part of
its lymphatics, exhalents, absorbents ; its excre-
tions and integuments. Ail these share in the
result — join in the effect; and how all these, or any
of them, come together without a designing, dis-
posing intelligence, it is impossible to conceive.

196 NATURAL THEOLOGY.

CHAPTER XI.

OF THE ANIMAL STRUCTURE REGARDED AS A MASS.

CoNTE3iPLATiNG an animal body in its collective
capacity, we cannot forget to notice what a num-
ber of instruments are brought together, and
often within how small a compass. It is a cluster
of contrivances. In a canary-bird, for instance,
and in the single ounce of matter which composes
his body, (but which seems to be all employed,)
we have instruments for eating, for digesting, for
nourishment, for breathing, for generation, for
running, for flying, for seeing, for hearing, for
smelling : each appropriate — each entirely differ-
ent from all the rest.

The human or indeed the animal frame, con-
sidered as a mass or assemblage, exhibits in its
composition three properties, which have long
struck my mind as indubitable evidences not only
of design, but of a great deal of attention and
accuracy in prosecuting the design.

I. The first is, the exact correspondency of the
two sides of the same animal : the right hand
answering to the left, leg to leg, eye to eye, one
side of the countenance to the other ; and with a
precision, to imitate which in any tolerable de-

NATURAL THEOLOGY. 197

gree forms one of the difficulties of statuaiy, and
requires, on the part of the artist, a constant at-
tention to this property of his work, distinct from
every other.

It is the most difficult thing that can be to get
a wig made even ; yet how seldom is the face
awiy ! And what care is taken that it should not
be so, the anatomy of its bones demonstrates. The
upper part of the face is composed of thirteen
bones, six on each side, answering each to each,
and the thirteenth, without a fellow, in the middle.
The lower part of the face is in like manner com-
posed of six bones, three on each side, respective-
ly corresponding, and the lower jaw in the centre.
In building an arch, could more be done in order
to make the curve true — i. e., the parts equidis-
tant from the middle, alike in figure and position ?

The exact resemblance of the eyes, considering
how compounded this organ is in its structure,
how various and how delicate are the shades of
colour with which its iris is tinged ; how different-
ly, as to effect upon appearance, the eye may be
mounted in its socket, and how differently in dif-
ferent heads eyes actually are set — is a property
of animal bodies much to be admired. Of ten
thousand eyes, I do not know that it would be pos-
sible to match one, except with its own fellow ; or
to distribute them into suitable pairs by any other
selection than that which obtains.

This regularity of the animal structure is ren-

17^

198 NATURAL TIIEOLOGV.

dered more remarkable by the three following
considerations : —

1. The limbs, seiiarately taken, have not this cor-
relation of parts, but the contrary of it. A knife
drawn down the chine cuts the human body into
two parts, externally equal and alike ; you cannot
draw a straight line which will divide a hand, a
foot, the leg, the thigh, the cheek, the eye, the ear,
into two parts equal and alike. Those parts
which are placed upon the middle or partition line
of the body, or which traverse that line — as the
nose, the tongue, and the lips — may be so
divided, or, more properly speaking, are double
organs ; but other parts cannot. This shows that
the correspondency which we have been describ-
ing does not arise by any necessity in the nature
of the subject ; for, if necessary, it would be uni-
versal ; whereas it is observed only in the system
or assemblage. It is not true of the separate parts :
that is to say, it is not found where it conduces to
beauty or utility ; it is found where it would
subsist at the expense of both. The two wings of
a bird always correspond : the two sides of a fea-
ther frequently do not. In centipedes, millepedes,
and the whole tribe of insects, no two legs on the
same side are alike ; yet there is the most exact
parity between the legs opposite to one another.

2. The next circumstance to be remarked is,
that, whilst the cavities of the body are so confi-
gurated, as externally to exhibit the most exact
correspondency of the opposite sides, the contents

NATURAL THEOLOGY. 199

of these cavities have no such correspondency. A
line drawn down the middle of the breast divides
the thorax into two sides exactly similar; yet these
two sides enclose very different contents. The
heart lies on the left side ; a lobe of the lungs on the
right; balancing each other neither in size nor shape.
The same thing holds of the abdomen. The liver
lies on the right side, without any similar viscus
opposed to it on the left. The spleen indeed is
situated over against the liver: but agreeing with
the liver neither in bulk nor form. There is no
equipollency between these. The stomach is a
vessel, both irregular in its shape, and oblique in
its position. The foldings and doublings of the
intestines do not present a parity of sides. Yet
that symmetry which depends upon the correla-
tion of the sides is externally preserved through-
out the whole trunk ; and is the more remarkable
in the lower parts of it, as the integuments are
soft ; and the shape, consequently, is not, as the
thorax is by its ribs, reduced by natural stays. It
is evident, therefore, that the external proportion
does not arise from any equality in the shape or
pressure of the internal contents. What is it,
indeed, but a correction of inequalities ? — an ad-
justment, by mutual compensation, of anomalous
forms into a regular congeries? — the effect, in a
word, of artful, and if we might be permitted to
speak, of studied collocation ?

3. Similar also to this is the third observation :
that an internal inequality in the feeding vessels is

200 NATURAL THEOLOGY.

SO managed as to produce no inequality of parts
which were intended to correspond. The right
arm answers accurately to the left, both in size
and shape ; but the arterial branches which sup-
ply the two arms do not go off from their trunk,
in a pair, in the same manner, at the same place,
or at the same angle. Under which want of
similitude, it is very difficult to conceive how the
same quantity of blood should be pushed through
each artery ; yet the result is right ; the two limbs
which are nourished by them perceive no dif-
ference of supply — no effects of excess or defi-
ciency.

Concerning the difference of manner in which
the subclavian and carotid arteries, upon the dif-
ferent sides of the body, separate themselves from
the aorta, Cheselden seems to have thought, that
the advantage which the left gain by going ofl' at
an angle much more acute than the right, is made
up to the right by their going off together in one
branch.* It is very possible that this may be the
compensating contrivance ; and if it be so, how
curious — how hydrostatical !

II. Another perfection of the animal mass is the
package. I know nothing which is so surprising.
Examine the contents of the trunk of any large
animal. Take notice how soft, how tender, how
intricate they are ; how constantly in action, how
necessary to life ! Reflect upon the danger of any
injury to their substance, any derangement to their
position, any obstruction to their office. Observe

* Ches. Anat. p. 184, ed. p. 7

NATURAL THEOLOGY. 201

the heart pumping at the centre, at the rate of
eighty strokes in a minute; one set of pipes carry-
ing the stream away from it, another set bringing,
in its course, the fluid back to it again ; the lungs
performing their elaborate office, viz., distending
and contracting their many thousand vesicles by a
reciprocation which cannot cease for a minute ;
the stomach exercising its powerful chemistry ;
the bowels silently propelling the changed aliment;
collecting from it, as it proceeds, and transmitting
to the blood an incessant supply of prepared
and assimilated nourishment ; that blood pursuing
its course ; the liver, the kidneys, the pancreas, the
parotid, with many other known and distinguish-
able glands, drawing off from it, all the while,
their proper secretions. These several operations,
together with others more subtile but less capable
of being investigated, are going on within us at
one and the same time. Think of this ; and then
observe how the body itself, the case which holds
this machinery, is rolled, and jolted, and tossed
about, the mechanism remaining unhurt, and with
very little molestation even of its nicest motions.
Observe a rope-dancer, a tumbler, or a monkey ;
the sudden inversions and contortions which the in-
ternal parts sustain by the postures into which their
bodies are thrown; or rather observe the shocks
which these parts, even in ordinary subjects, some-
times receive from falls and bruises, or by abrupt
jerks and twists, without sensible or with soon-
recovered damage. Observe this, and then reflect

202 NATURAL THEOLOGY.

how firmly every part must be secured, how care-
fully surrounded, how well tied down and packed
together.

This property of animal bodies has never, I
think, been considered under a distinct head, or so
fully as it deserves. I may be allowed therefore,
in order to verify my observation concerning it, to
set forth a short anatomical detail, though it oblige
me to use more technical language than I should'
wish to introduce into a work of this kind.

1 . The heart (such care is taken of the centre
of life) is placed between two soft lobes of the
lungs ; is tied to the mediastinum and to the peri-
cardium ; which pericardium is not only itself an
exceedingly strong membrane, but adheres firmly
to the duplicature of the mediastinum, and, by its
point, to the middle tendon of the diaphragm.
The heart is also sustained in its place by the
great blood-vessels which issue from it.*

2. The lungs are tied to the sternum by the
mediastinum before; to the vertebrae by the pleu-
ra behind. It seems indeed to be the very use of
the mediastinum (which is a membrane that goes
straight through the middle of the thorax, from
the breast to the back) to keep the contents of
the thorax in their places ; in particular to hinder
one lobe of the lungs from incommoding another,
or the parts of the lungs from pressing upon each
other when we lie on one side.f

*Keill's Anat. p. 107, ed. 3. f lb. p. 119, ed. 3.

NATURAL THEOLOGY. 203

3. The liver is fastened in the body by two
ligaments: the first, which is large and strong,
comes from the covering of the diaphragm, and
penetrates the substance of the hver; the second
is the umbilical vein, which, after birth, degene-
rates into a ligament. The first, which is the prin-
cipal, fixes the liver in its situation whilst the
body holds an erect posture ; the second prevents
it from pressing upon the diaphragm w^hen we lie
down ; and both together sling or suspend the
liver when we lie upon our backs, so that it may
not compress or obstruct the ascending vena
cava,* to which belongs the important oflice of
returning the blood from the body to the heart.

4. The bladder is tied to the navel by the ura-
chus, transformed into a ligament: thus, what was
a passage for urine to the foetus, becomes, after
birth, a support or stay to the bladder. The pe-
ritonaeum also keeps the viscera from confound-
ing themselves with, or pressing irregularly upon,
the bladder ; for the kidneys and bladder are con-
tained in a distinct duplicalure of that membrane,
being thereby partitioned off from the other con-
tents of the abdomen.

5. The kidneys are lodged in a bed of fat.

6. The pancreas, or sweetbread, is strongly
tied to the peritonaeum, which is the great wrap-
ping sheet, that encloses all the bowels contained
in the lower belly.f

* Ches. Anat. p. 162. f Keill's Anat. p. 57.

204 NATURAL THEOLOGY.

7. The spleen also is confined to its place by
an adhesion to the peritonaeum and diaphragm,
and by a connexion with the omentum.* It is
possible, in my opinion, that the spleen may be
merely a stuffing, a soft cushion to fill up a vacan-
cy or hollow, which, unless occupied, would leave
the package loose and unsteady : for, supposing
that it answers no other purpose than this, it must
be vascular, and admit of a circulation through it,
in order to be kept alive, or be a part of a living
body.^^

8. The omentum, epiploon, or cawl, is an apron
tucked up, or doubling upon itself, at its lowest
part. The upper edge is tied to the bottom of
the stomach, to the spleen, as hath already been
observ ed, and to part of the duodenum. The re-
flected edge also, after forming the doubling,
comes up behind the front flap, and is tied to the
colon and adjoining viscera.f

9. The septa of the brain probably prevent one
part of the organ from pressing with too great a
weight upon another part. The processes of the
dura mater divide the cavity of the skull, like so

''^Our author has not failed to fall into the snare which lies in
the path of the adventurous theorist. We have here a new theory
of Ihe spleen. The spleen in truth has a double office : it is ever
found attached to the digesting part of the intestinal canal ; and is
reasonably considered to afford occasional increase of circulation
to the stomach, and to supply blood to the liver of that quahty
which appears necessary to a copious secretion of bile.

* Ches. Anat p. 167. flbid.

NATURAL THEOLOGY. 205

many inner partition walls, and thereby confine
each hemisphere and lobe of the brain to the
chamber which is assigned to it, without its being
liable to rest upon or intermix with the neighbour-
ing parts. The great art and caution of packing
is to prevent one thing hurting another. This, in
the head, the chest, and the abdomen, of an ani-
mal body, is, amongst other methods, provided for
by membranous partitions and wrappings, which
keep the parts separate.

The above may serve as a short account of the
manner in which the principal viscera are sus-
tained in their places. But of the provisions for
this purpose, by far, in my opinion, the most
curious, and where also such a provision was most
wanted, is in the guts. It is pretty evident, that
a long narrow tube (in man, about five times the
length of the body,) laid from side to side in folds
upon one another, winding in oblique and circuit-
ous directions, composed also of a soft and yield-
ing substance, must, without some extraordinary
precaution for its safety, be continually displaced
by the various, sudden, and abrupt motions of the
body which contains it. I should expect that, if
not bruised or wounded by every fall, or leap, or
twist, it would be entangled, or be involved with
itself; or, at the least, slipped and shaken out of
the order in which it is disposed, and which order
is necessary to be preserved for the carrying on
of the important functions which it has to execute
in the animal economy. Let us see, therefore,

18

206 NATURAL THEOLOGY.

how a danger so serious, and yet so natural to the
length, narrowness, and tubular form of the part,
is provided against. The expedient is admirable,
and it is this. The intestinal canal, throughout its
whole process, is knit to the edge of a broad fat
membrane called the mesentery. It forms the
margin of this mesentery, being stitched and fas-
tened to it like the edging of a ruffle ; being four
times as long as the mesentery itself, it is what a
seamstress would call " puckered or gathered on "
to it. This is the nature of the connexion of the
gut with the mesentery; and being thus joined to,
or rather made a part of, the mesentery, it is
folded and wrapped up together with it. Now
the mesentery, having a considerable dimension in
breadth, being in its substance withal both thick
and suety, is capable of a close and safe folding, in
comparison of what the intestinal tube would ad-
mit of, if it had remained loose. The mesentery
likewise not only keeps the intestinal canal in its
proper place and position under all the turns and
windings of its course, but sustains the number-
less small vessels, the arteries, the veins, the lym-
pheducts, and, above all, the lacteals, which lead
from or to almost every point of its coats and
cavity. This membrane, which appears to be
the great support and security of the alimentary
r.pparatus, is itself strongly tied to the first three
\ v:rtebra3 of the loins.*

* Keill's Anat. p. 45.

NATURAL THEOLOGY. 207

III. A third general property of animal forms
is beauty. I do not mean relative beauty, or that
of one individual above another of the same spe-
cies; but I mean, generally, the provision which
is made in the body of almost every animal to
adapt its appearance to the perception of the ani-
mals with which it converses. In our own spe-
cies, for example, only consider what the parts
and materials are of which the fairest body is
composed ; and no further observation will be ne-
cessary to show how well these things are wrap-
ped up, so as to form a mass which shall be capa-
ble of symmetry in its proportion, and of beauty
in its aspect ; how the bones are covered, the
bowels concealed, the roughnesses of the muscle
smoothed and softened ; and how over the whole
is drawn an integument, which converts the dis-
gusting materials of a dissecting-room into an
object of attraction to the sight, or one upon
which it rests at least with ease and satisfaction-
Much of this effect is to be attributed to the inter-
vention of the cellular or adipose membrane,
which lies immediately under the skin ; is a kind
of lining to it ; is moist, soft, slippery, and com-
pressible ; everywhere filling up the insterstices of
the muscles, and forming thereby their roundness
and flowing line, as well as the evenness and
pohsh of the whole surface.

All which seems to be a strong indication of de-
sign, and of a design studiously directed to this pur-
pose. And it being once allowed that such a pur-

208 NATURAL THEOLOGY.

pose existed with respect to any of the productions
of nature, we may refer, with a considerable de-
gree of probability, other particulars to the same
intention ; such as the tints of flowers, the plumage
of birds, the furs of beasts, the bright scales of
fishes, the painted wings of butterflies and beetles,
the rich colours and spotted lustre of many tribes
of insects.

There are parts also of animals ornamental, and
the properties by which they are so not subser-
vient, that we know of, to any other purpose. The
irides of most animals are very beautiful, without
conducing at all, by their beauty, to the perfection
of vision ; and nature could in no part have em-
ployed her pencil to so much advantage, because
no part presents itself so conspicuously to the ob-
server, or communicates so great an effect to the
whole aspect.

In plants, especially in the flowers of plants, the
principle of beauty holds a still more considerable
place in their composition ; is still more confessed
than in animals. Why, for one instance out of a
thousand, does the corolla of the tulip, when ad-
vanced to its size and maturity, change its colour?
The purposes, so far as we can see, of vegetable
nutrition might have been carried on as well by its
continuing green. Or, if this could not be, consist-
ently with the progress of vegetable life, why break
into such a variety of colours ? This is no proper
effect of age, or of declension in the ascent of the
sap ; for that, like the autumnal tints, would have

NAT AURAL THEOLOGY. 209

produced one colour on one leaf, with marks of
fading and withering. It seems a lame account to
call it, as it has been called, a disease of the plant.
Is it not more probable that this property, which
is independent, as it should seem, of the wants and
utilities of the plant, was calculated for beauty, in-
tended for display ?

A ground, I know, of objection has been taken
against the whole topic of argument, namely, that
there is no such thing as beauty at all ; in other
words, that whatever is useful and familiar comes
of course to be thought beautiful ; and that things
appear to be so, only by their alliance with these
quahties. Our idea of beauty is capable of being
in so great a degree modified by habit, by fashion,
by the experience of advantage or pleasure, and
by associations arising out of that experience, that
a question has been made, whether it be not alto-
gether generated by these causes, or would have
any proper existence without them. It seems, how-
ever, a carrying of the conclusion too far, to deny
the existence of the principle, viz., a native capacity
of perceiving beauty, on account of an influence,
or of varieties proceeding from that influence, to
which it is subject, seeing that principles the most
acknowledged are liable to be affected in the same
manner. I should rather argue thus : — The ques-
tion respects objects of sight. Now every other
sense hath its distinction of agreeable and disagree-
able. Some tastes offend the palate, others gratify
it. In brutes and insects, this distinction is stronger

18*

210 NATURAL THEOLOGY.

and more regular than in man. Every horse, ox,
sheep, swine, when at Hberty to choose, and when
in a natural state, that is, when not vitiated by
habits forced upon it, eats and rejects the same
plants. Many insects which feed upon particular
plants, will rather die than change their appropri-
ate leaf. All this looks like a determination in the
sense itself to particular tastes. In like manner,
smells affect the nose with sensations pleasurable
or disgusting. Some sounds, or compositions of
sound, delight the ear: others torture it. Habit
can do much in all these cases, (and it is well for
us that it can ; for it is this power which recon-
ciles us to many necessities :) but has the distinc-
tion, in the mean time, of agreeable and disagree-
able, no foundation in the sense itself? What is
true of the other senses is most probably true of
the eye, (the analogy is irresistible,) viz., that there
belongs to it an original constitution, fitted to re-
ceive pleasure from some impressions, and pain from
others.

I do not however know, that the argument which
alleges beauty as a final cause rests upon this con-
cession. We possess a sense of beauty, however
we come by it. It in fact exists. Things are not
indifterent to this sense ; all objects do not suit it ;
many, which we see, are agreeable to it : many
others disagreeable. It is certainly not the effect
of habit upon the particular object, because the
most agreeable objects are often the most rare ;
many which are very common, continue to be offen-

NATURAL THEOLOGY. 211

sive. If they be made supportable by habit, it is
all which habit can do ; they never become agree-
ble. If this sense, therefore, be acquired, it is a
result ; the produce of numerous and complicated
actions of external objects upon the senses, and of
the mind upon its sensations. With this result,
there must be a certain congruity to enable any
particular object to please ; and that congruity, we
contend, is consulted in the aspect which is given
to animal and vegetable bodies.

IV. The skin and covering of animals is that
upon which their appearance chiefly depends ; and
it is that part which, perhaps, in all animals, is most
decorated, and most free from impurities. But
were beauty, or agreeableness of aspect, entirely
out of the question, there is another purpose an-
swered by this integument, and by the collocation
of the parts of the body beneath it, which is of still
greater importance ; and that purpose is conceal-
ment. Were it possible to view through the skin
the mechanism of our bodies, the sight would fright-
en us out of our v/its. " Durst we make a single
movement," asks a lively French writer, " or stir a
step from the place we were in, if we saw our blood
circulating, the tendons pulling, the lungs blowing,
the humours filtrating, and all the incomprehensi-
ble assemblage of fibres, tubes, pumps, valves, cur-
rents, pivots, which sustain an existence at once so
frail and so presumptuous ?"

V. Of animal bodies, considered as masses, there
is another property, more curious than it is gene-

212 NATURAL THEOLOGY.

rally thought to be ; which is the faculty of stand-
ing : and it is more remarkable in two-legged ani-
mals than in quadrupeds, and, most of all, as being
the tallest, and resting upon the smallest base, in
man. There is more, I think, in the matter than
we are aware of. The statue of a man, placed
loosely upon a pedestal, would not be secure of
standing half an hour. You are obliged to fix its
feet to the block by bolts and solder ; or the first
shake, the first gust of wind, is sure to throw it
down. Yet this statue shall express all the me-
chanical proportions of a living model. It is not
therefore the mere figure, or merely placing the
centre of gravity within the base, that is sufficient.
Either the law of gravitation is suspended in favour
of living substances, or something more is done for
them, in order to enable them to uphold their pos-
ture. There is no reason whatever to doubt, but
that their parts descend by gravitation in the
same manner as those of dead matter. The gift
therefore appears to me to consist in a faculty of
perpetually shifting the centre of gravity, by a set
of obscure, indeed, but of quick-balancing actions,
so as to keep the line of direction, which is a line
drawn from that centre to the ground, within its
prescribed limits.

Of these actions it may be observed, first, that
they in part constitute what we call strength.
The dead body drops down. The mere adjust-
ment therefore of weight and pressure, which may
be the same the moment after death as the mo-

NATURAL THEOLOGY. 213

ment before, does not support the column. In
cases also of extreme weakness, the patient cannot
stand upright. Secondly, that these actions are
only in a small degree voluntary. A man is sel-
dom conscious of his voluntary powers in keeping
himself upon his legs. A child learning to walk
is the greatest posture-master in the world : but
art, if it may be so called, sinks into habit ; and
he is soon able to poise himself in a great variety
of attitudes, without being sensible either of cau-
tion or effort. But still there must be an aptitude
of parts, upon which habit can thus attach ; a pre-
vious capacity of motions which the animal is thus
taught to exercise : and the facility with which
this exercise is acquired forms one object of our
admiration. What parts are principally employed,
or in what manner each contibutes to its office,
is, as hath already been confessed, difficult to ex-
plain. Perhaps the obscure motion of the bones
of the feet may have their share in this effect.
They are put in action by every slip or vacillation
of the body, and seem to assist in restoring its
balance. Certain it is, that this circumstance in
the structure of the foot, viz., its being composed
of many small bones, applied to and articulating
with one another by diversely shaped surfaces,
instead of being made of one piece, like the last
of a shoe, is very remarkable.

214 NATURAL THEOLOGY.

I suppose also that it would be difficult to stand
firmly upon stilts or wooden legs, though their
base exactly imitated the figure and dimensions
of the sole of the foot. The alternation of the
joints, the knee-joint bending backward, the hip-
joint forward ; the flexibihty, in every direction,
of the spine, especially in the loins and neck, ap-
pear to be of great moment in preserving the
equilibrium of the body. With respect to this
last circumstance, it is observable, that the ver-
tebrae are so confined by ligaments as to allow no
more slipping upon their bases, than what is just
sufficient to break the shock which any violent
motion may occasion to the body. A certain de-
gree also of tension of the sinews appears to be
essential to an erect posture ; for it is by the loss
of this that the dead or paralytic body drops down.
The whole is a wonderful result of combined
powers, and of very complicated operations. In-
deed, that standing is not so simple a business as
we imagine it to be, is evident from the strange
gesticulations of a drunken man, who has lost the
government of the centre of gravity.^^

^ All this is admirably well put by our author. Yet when he
says '* the gift consists in the faculty of perpetually shifting the

NATURAL THEOLOGY. 215

We have said that this property is the most
worthy of observation in the human body ; but a
bird, resting upon its perch, or hopping upon a
spray, affords no mean specimen of the same fa-
culty. A chicken runs off as soon as it is hatched
from the egg ; yet a chicken, considered geome-
trically, and with relation to its centre of gravity,
its line of direction, and its equilibrium, is a very
irregular solid. Is this gift, therefore, or instruc-
tion ? May it not be said to be with great atten-
tion that nature hath balanced the body upon its
pivots ?

I observe also in the same bird a piece of use-
ful mechanism of this kind. In the trussing of a
fowl, upon bending the legs and thighs up towards
the body, the cook finds that the claws close of

centre of gravity, by a set of obscure, indeed, but of quick balanc-
ing actions," he states a fact, but omits the most surprising cir-
cumstance of all. No doubt such efforts are made ; but what
directs them ? If a man should balance a staff, resting it on the
point of the finger, he shifts the finger continually, in doing which
he is directed by the eye — he sees the staff inclining. How does
a man judge of the inclination of his body in the very first degree
of deviation from the perpendicular ? He does not see himself,
nor is he directed by the objects around him, since a blind man
will stand as securely as one who sees. The fact is, that he has
a knowledge of muscular action — a sensibility to the finest ad-
justment of the muscles, by which he directs their efforts. This
sense is of all the most marvellous : a sensibility to an internal
motion, more minute and curious than are the sensibilities to ex-
ternal impression ; and which, as may be easily proved, ministers
to a variety of proparties in the living body, and especially to the
organs of sense themselves.

216 NATURAL THEOLOGY.

their own accord. Now let it be remembered,
that this is the position of the limbs in which the
bird rests upon its perch. And in this position it
sleeps in safety ; for the claws do their office in
keeping hold of the support — not by any exertion
of voluntary power, which sleep might suspend,
but by the traction of the tendons in consequence
of the attitude which the legs and thighs take by
the bird sitting down, and to which the mere
weight of the body gives the force that is neces-
sary.

VI. Regarding the human body as a mass ; re-
garding the general conformations which obtain
in it ; regarding also particular parts in respect to
those conformations ; we shall be led to observe
what I call " interrupted analogies." The follow-
ing are examples of what 1 mean by these terms ;
and I do not know how such critical deviations
can, by any possible hypothesis, be accounted for
without design: —

I. All the bones of the body are covered with a
periostium, except the teeth, where it ceases; and
an enamel of ivory, which saws and files will
hardly touch, comes into its place. No one can
doubt of the use and propriety of this difference ;
of the " analogy " being thus "interrupted ;" of the
rule, which belongs to the confirmation of the
bones stopping where it does stop ; for, had so ex-
quisitely sensible a membrane as the periostium
invested the teeth, as it invests every other bone

NATURAL THEOLOGY. 217

of the body, their action, necessary exposure, and
irritation, would have subjected the animal to con-
tinual pain. General as it is, it was not the sort
of integument which suited the teeth ; what they
stood in need of was a strong, hard, insensible,
defensive coat ; and exactly such a covering is
given to them, in the ivory enamel which adheres
to their surface."''

2. The scarf-skin, which clothes all the rest of
the body, gives way, at the extremities of the toes
and fingers, to nails. A man has only to look at
his hand, to observe with what nicety and pre-
cision that covering, which extends over every
other part, is here superseded by a different sub-
stance and a different texture. Now, if either
the rule had been necessary, or the deviation from
it accidental, this eflect would not be seen. When
I speak of the rule being necessary, I mean the
formation of the skin upon the surface being pro-
duced by a set of causes constituted without de-
sign, and acting, as all ignorant causes must act,
by a general operation. Were this the case, no
account could be given of the operation being
suspended at the fingers' ends, or on the back
part of the fingers, and not on the fore part. On
the other hand : if the deviation were accidental,
an error, an anomalism — were it any thing else
than settled by intention — we should meet with
nails upon other parts of the body : they would

*'' See the dissertation on teeth, in the Appendix.
19

218 NATURAL THEOLOGY,

be scattered over the surface, like warts or pim-
ples.«

3. All the great cavities of the body are en-
closed by membranes, except the skull. Why
should not the brain be content with the same
covering as that which serves for the other prin-
cipal organs of the body ? The heart, the lungs,
the liver, the stomach, the bowels, have all soft
integuments, and nothing else. The muscular coats
are all soft and membranous. I can see a reason
for this distinction in the final cause, but in no
other. The importance of the brain to life, (which
experience proves to be immediate.) and the ex-
treme tenderness of its substance, make a solid
case more necessary for it, than for any other
part; and such a case the hardness of the skull
supplies.^ AVhen the smallest portion of this

^^ The human nail is calculated to support the cushion of the
extremity of the finger, and is important to us in grasping or hold-
ing any thing; but more so still in sustaining that cushion as the
chief organ of touch. There are other parts of the body which
have exquisite sensibility, yet they are not provided so as to give
us that information of the condition of matter which we have
through the finger, and in a lesser degree through the whole in-
ner surface of the hand. We easily feel, for example, the pulsa-
tion of the artery at the wrist, through the combination of the
sensibihty of the nerve of touch with the elastic cushion of the
finger. The best proof of the use of the elastic cushion is this :
Although the tip of the tongue feels so exquisitely that the pre-
sence of a hair of wool troubles us, yet if we apply it to the pulse
we shall not be sensible of the beat.

^ There is a note upon the form of the skull in the Appendix,
which may interest the reader.

NATURAL THEOLOGY. 219

natural casket is lost, how carefully, yet how im-
perfectly, is it replaced by a plate of metal ! If
an anatomist should say, that this bony protection
is not confined to the brain, but is extended along
the course of the spine, I answer, that he adds
strength to the argument. If he remark, that the
chest also is fortified by bones, I reply, that I should
have alleged this instance myself, if the ribs had
not appeared subservient to the purpose of motion
as well as of defence. What distinguishes the
skull from every other cavity is, that the bony
covering completely surrounds its contents, and is
calculated, not for motion, but solely for defence.
Those hollows, likewise, and inequalities which
we observe in the inside of the skull, and which
exactly fit the folds of the brain, answer the im-
portant design of keeping the substance of the
brain steady, and of guarding it against concus-
sions.

220 NATURAL THEOLOGY.

CHAPTER XII.

COMPARATIVE ANATOMY.

Whenever we find a general plan pursued, yet
with such variations in it as are, in each case,
required by the particular exigency of the subject
to which it is applied, we possess, in such a plan
and such adaptation, the strongest evidence that
can be afforded of intelligence and design : an evi-
dence which the most completely excludes every
other hypothesis. If the general plan proceeded
from any fixed necessity in the nature of things,
how could it accommodate itself to the various
wants and uses which it had to serve under differ-
ent circumstances, and on different occasions ?
ArkwrighVs mill was invented for the spinning of
cotton. We see it employed for the spinning of
wool, flax, and hemp, with such modifications of
the original principle, such variety in the same
plan, as the texture of those different materials
rendered necessary. Of the machine's being put
together with design, if it were possible to doubt
whilst we saw it only under one mode, and in one
form ; when we came to observe it in its different
applications, with such changes of structure, such
additions and supplements, as the special and par-
ticular use in each case demanded, we could not

NATURAL THEOLOGY. 221

refuse any longer our assent to the proposition —
"that intelligence, properly and strictly so called,
(including, under that name, foresight, considera-
tion, reference to utility,) had been employed, as
well in the primitive plan, as in the several changes
and accommodations which it is made to un-
dergo."

Very much of this reasoning is applicable to
what has been called Comparative Anatomy. In
their general economy, in the outlines of the plan,
in the construction as well as offices of their prin-
cipal parts, there exists between all large terres-
trial animals a close resemblance. In all, life is
sustained, and the body nourished, by nearly the
same apparatus. The heart, the lungs, the stomach,
the liver, the kidneys, are much alike in all. The
same fluid (for no distinction of blood has been
observed,) circulates through their vessels, and
nearly in the same order. The same cause, there-
fore, whatever that cause was, has been concern-
ed in the origin, has governed the production, of
these different animal forms.

When we pass on to smaller animals, or to the
inhabitants of a different element, the resemblance
becomes more distant and more obscure ; but still
the plan accompanies us.

And, what we can never enough commend, and
which it is our business at present to exemplify,
the plan is attended, through all its varieties and
deflections, by subserviences to special occasions
and utilities.

19*

222 NATURAL THEOLOGY.

1. The covering of different animals, (though
whether I am correct in classing this under their
anatomy, I do not know,) is the first thing which
presents itself to our observation ; and is, in truth,
both for its variety and its suitableness to their
several natures, as much to be admired as any
part of their structure. We have bristles, hair,
wool, furs, feathers, quills, prickles, scales ; yet
in this diversity both of material and form, we
eannot change one animal's coat for another,
without evidently changing it for the worse ; —
taking care, however, to remark, that these cover-
ings are, in many cases, armour as well as cloth-
ing ; intended for protection as well as warmth.

The human animal is the only one which is
naked, and the only one which can clothe itself.
This is one of the properties which renders him
an animal of all climates, and of all seasons. He
can adapt the warmth or lightness of his covering
to the temperature of his habitation. Had he
been born with a fleece upon his back, although
he might have been comforted by its warmth in
high latitudes, it would have oppressed him by its
weight and heat, as the species spread towards
the equator.

What art, however, does for men, nature has,
in many instances, done for those animals which
are incapable of art. Their clothing, of its own
accord, changes with their necessities. This is
particularly the case with that large tribe of quad-
rupeds which are covered with furs. Every

NATURAL THEOLOGY. 223

dealer in hare-skins and rabbit-skins knows how
much the fur is thickened by the approach of
winter. It seems to be a part of the same con-
stitution and the same design, that wool, in hot
countries, degenerates, as it is called, but in truth
(most happily for the animal's ease) passes into
hair : whilst, on the contrary, that hair, in the
dogs of the polar regions, is turned into wool, or
something very like it. To which may be re-
ferred, what naturalists have remarked, that bears,
wolves, foxes, hares, which do not take the water,
have the fur much thicker on the back than the
belly ; whereas in the beaver it is the thickest
upon the belly ; as are the feathers in water-fowl.
We know the final cause of all this, and we know
no other.

The covering of birds cannot escape the most
vulgar observation : its lightness, its smoothness,
its warmth — the disposition of the feathers all
inclined backward, the down about their stem, the
overlapping of their tips, their different configura-
tion in different parts, not to mention the variety
of their colours, constitute a vestment for the
body, so beautiful, and so appropriate to the life
which the animal is to lead, as that, I think, we
should have had no conception of any thing
equally perfect, if we had never seen it, or can
now imagine any thing more so. Let us sup-
pose (what is possible only in supposition,) a per-
son who had never seen a bird to be presented
with a plucked pheasant, and bid to set his wits

224 NATURAL THEOLOGY.

to work how to contrive for it a covering which
shall unite the qualities of warmth, levity, and
least resistance to the air, and the highest degree
of each ; giving it also as much of beauty and
ornament as he could afford. He is the person
to behold the work of the Deity, in this part of
his creation, with the sentiments which are due to
it.

The commendation which the general aspect
of the feathered world seldom fails of exciting
will be increased by further examination. It is
one of those cases in which the philosopher has
more to admire than the common observer.
Every feather is a mechanical wonder. If we look
at the quill, we find properties not easily brought
together — strength and lightness. I know few
things more remarkable than the strength and
lightness of the very pen with which I am writing.
If we cast our eye to the upper part of the stem,
we see a material, made for the purpose, used in
no other class of animals, and in no other part of
birds, tough, light, pliant, elastic. The pith also
which feeds the feathers is, amongst animal sub-
stances, sui generis — neither bone, flesh, mem-
brane, nor tendon.*

But the artificial part of a feather is the heard,
or, as it is sometimes, I believe, called the vane.

* The quill part of a feather is composed of circular and longi-
tudinal fibres. In making a pen, you must scrape off the coat of
circular fibres, or the quill will split in a ragged, jagged manner,
making what boys call caVs teeth.

NATURAL THEOLOGY. 225

By the beards are meant what are fastened on
each side of the stem, and what constitute the
breadth of the feather, what we usually strip off
from one side or both when we make a pen. The
separate pieces, or laminae, of which the beard is
composed, are called threads, sometimes filaments
or rays. Now, the first thing which an attentive
observer will remark is, how much stronger the
beard of the feather shows itself to be when
pressed in a direction perpendicular to its plane,
that when rubbed, either up or down, in the line
of the stem ; and he will soon discover the struc-
ture which occasions this difference, viz., that the
laminae whereof these beards are composed are
flat, and placed with their flat sides towards each
other, by which means, whilst they easily bend
for the approaching of each other, as any one
may perceive by drawing his finger ever so lightly
upwards, they are much harder to bend out of
their plane, which is the direction in which they
have to encounter the impulse and pressure of the
air, and in which their strength is wanted and
put to the trial.

This is one particularity in the structure of a
feather: a second is still more extraordinary.
Whoever examines a feather cannot help taking
notice, that the threads or laminae of which we
have been speaking, in their natural state, unite —
that their union is something more than the mere
apposition of loose surfaces — that they are not
parted asunder without some degree of force —

226 NATURAL THEOLOGY.

that, nevertheless, there is no glutinous cohesion
between them — that, therefore, by some mechan-
ical means or other, they catch or clasp among
themselves, thereby giving to the beard or vane
its closeness and compactness of texture. Nor is
this all ; when two laminae which have been sepa-
rated bv accident or force are brouojht together
again, they immediately reclasp ; the connexion,
whatever it was, is perfectly recovered, and the
beard of the feather becomes as smooth and firm
as if nothing had happened to it. Draw your
finoer down the fealher, which is against the grain,
and you break, probably, the junction of some of
the contiguous threads ; draw your finger up the
feather, and you restore all things to their former
state. This is no common contrivance : and now
for the mechanism by which it is effected. The
threads or laminae above mentioned are interlaced
w^ith one another ; and the interlacing is perform-
ed by means of a vast number of fibres or teeth,
which the laminae shoot forth on each side, and
which hook and grapple together. A friend of
mine counted fifty of these fibres in one twentieth
of an inch. These fibres are crooked, but curved
after a different manner ; for those which proceed
from the thread on the side towards the extremity
of the feather are longer, more flexible, and bent
downward ; whereas those which proceed from
the side towards the beginning or quill end of the
feather are shorter, firmer, and turn upwards.
The process, then, which takes place is as follows :

NATURAL THEOLOGY. 227

when two laminae are pressed together, so that
these long fibres are forced far enough over the
short ones, their crooked parts fall into the cavity
made by the crooked parts of the others, just as
the latch that is fastened to a door enters into the
cavity of the catch fixed to the door-post, and
there hooking itself, fastens the door; for it is pro-
perly in this manner that one thread of a feather
is fastened to the other.

This admirable structure of the feather, which
it is easy to see with the microscope, succeeds
perfectly for the use to which nature has designed
it, which use was, not only that the laminae might
be united, but that, when one thread or lamina
has been separated from another by some exter-
nal violence, it might be reclasped with sufficient
facility and expedition.*

In the ostrich, this apparatus of crotchets and
fibres, of hooks and teeth, is wanting ; and we see
the consequence of the want. The filaments hang
loose and separate from one another, forming only
a kind of down, which constitution of the feathers,
however it may fit them for the flowing honours
of a lady's head-dress, may be reckoned an im-
perfection in the bird, inasmuch as wings composed
of these feathers, although they may greatly assist
it in running, do not serve for flight.

* The above account is taken from Memoirs for a Natural His-
tory of Animals, by the Royal Academy of Paris, published in
1701, p. 219.

228 NATURAL THEOLOGY.

But, under the present division of our subject,
our business with feathers is as they are the cover-
ing of the bird. And herein a singular circum-
stance occurs. In the small order of birds which
winter with us, from a snipe downwards, let the
external colour of the feathers be what it will,
their Creator has universally given them a bed of
black down next their bodies. Black, we know,
is the warmest colour ; and the purpose here is,
to keep in the heat arising from the heart and cir-
culation of the blood.^" It is further likewise re-
markable, that this is not found in larger birds ;
for which there is also a reason. Small birds are

^ When we attempt to apply the Hghts of experimental philo-
sophy to this subject, the inquiiy is not a little embarrassing. A
loose woolly texture, or down, as it implies the presence of air in
its interstices, air being a bad conductor of heat, is therefore a
warm covering ; it prevents the expenditure of animal heat.
When we consider the colour of the coverings of birds, we must
take new elements into our process of reasoning — we must re-
flect on the effects of the conduction and radiation of heat. The
conduction is the conveyance of heat ; and the radiation is the
parting with it into the atmosphere or into space. We have
already explained why the interior covering of the arctic bird
should be loose ; as to the colour, its effect must result from radia-
tion. It appears (to use the vulgar language) that the influence
of cold both on quadrupeds and birds is to increase their woolly
or downy covering, and, in many instances, to change the exterior
colour to white ; in other and more correct words, a provision is
made for changing their clothing so as to suit their altered cir-
cumstances. This change of colour corresponds with philoso-
phical experiments — a white surface absorbing the least, and
radiating the least, it should therefore tend to confine the vital
heat within the animal, and carry it off slowly to the atmosphere.

NATURAL THEOLOGY. 229

much more exposed to the cold than large ones,
forasmuch as they present, in proportion to their
bulk, a much larger surface to the air. If a tur-
key were divided into a number of wrens, (sup-
posing the shape of the turkey and the wren to
be similar,) the surface of all the wrens would
exceed the surface of the turkey in the proportion
of the length, breadth, (or of any homologous line)
of a turkey to that of a wren, which would be,
perhaps, a proportion of ten to one. It was ne-
cessary, therefore, that small birds should be more
warmly clad than large ones ; and this seems to
be the expedient by which that exigency is pro-
vided for.

II. In comparing different animals, I know no
part of their structure which exhibits greater va-
riety, or, in that variety, a nicer accommodation
to their respective conveniency than that which
is seen in the different formations of their mouths^
Whether the purpose be the reception of aliment
merely, or the catching of prey, the picking up of
seeds, the cropping of herbage, the extraction of
juices, the suction of liquids, the breaking and
grinding of food, the taste of that food, together
with the respiration of air, and, in conjunction
with it, the utterance of sound ; these various
offices are assigned to this one part, and, in dif-
ferent species, provided for as they are wanted by
its different constitution. In the human species,
forasmuch as there are hands to convey the food
to the mouth, the mouth is flat, and by reason of

20

230 NATURAL THEOLOGY.

its flatness, fitted only for reception ; whereas the
projecting jaws, the wide rictus, the pointed teeth,
of the dog and his affinities, enable them to apply
their mouths to snatch and seize the objects of
their pursuit. The full lips, the rough tongue,
the corrugated cartilaginous palate, the broad
cutting teeth of the ox, the deer, the horse, and
the sheep, qualify this tribe for browsing upon
their pasture ; either gathering large mouthfuls at
once, where the grass is long, which is the case
with the ox in particular, or biting close where it
is short, which the horse and the sheep are able
to do in a degree that one could hardly expect.
The retired under jaw of a swine works in the
ground, after the protruding snout, like a prong or
plough-share, has made its way to the roots upon
which it feeds. A conformation so happy was not
the gift of chance.

NATURAL THEOLOGY. 231

In birds, this organ assumes a new character ;
new both in substance and in form, but in both
wonderfully adapted to the wants and uses of a
distinct mode of existence. We have no longer
the fleshy lips, the teeth of enamelled bone ; but
we have, in the place of these two parts, and to
perform the office of both, a hard substance, (of
the same nature with that which composes the
nails, claws, and hoofs of quadrupeds,) cut out
into proper shapes, and mechanically suited to
the actions which are wanted. The sharp edge
and tempered point of the sparrow^s bill picks
almost every kind of seed from its concealment
in the plant, and not only so, but hulls the grain,
breaks and shatters the coats of the seed, in order
to get at the kernel. The hooked beak of the
hawk tribe separates the flesh from the bones of
the animals which it feeds upon, almost with the
cleanness and precision of a dissector's knife.
The butcher-bird transfixes its prey upon the
spike of a thorn whilst it picks its bones. In
some birds of this class we have the cross bill, {. e.,
both the upper and lower bill hooked, and their
tips crossing. The spoo?i bill enables the goose
to graze, to collect its food from the bottom of
pools, or to seek it amidst the soft or liquid sub-
stances with which it is mixed. The long tapering
bill of the snipe and woodcock penetrate still
deeper into moist earth, which is the bed in which
the food of that species is lodged. This is exactly
the instrument which the animal wanted. It did

232 NATURAL THEOLOGY.

not want strength in its bill, which was inconsist-
ent with the slender form of the animal's neck,
as well as unnecessary for the kind of aliment
upon which it subsists ; but it wanted length to
reach its object.*^

*' Witli the instrument, as we have before hinted, we should
expect a particular instinctive action, and a corresponding mus-
cular power. As an animal with horns has a powerful neck, so
has the neck of the heron, which is introduced here, an extraordi-
nary muscular power, without which, indeed, the long and sharp
bill would be of little use. When the dog approaches the wound-
ed heron, the bird throws itself upon its back, and, retracting its
long neck, suddenly darts it out with a force which strikes the bill
deep into the dog. If you hold your hat towards the bird, the bill

will be struck quite through it. In contending with the hawk^
when the latter is spitted, it is not by the rapid descent of the
hawk, but by the force with which the heron drives its bill.

The strenoth of the bill of the parrot, and that of all birds which
break the stones of fruit, or nuts, or hard seeds, is in another di-
rection : the bill is hooked, yet is diflercntly formed from that of
the carnivorous bird. The intention is, in the first place, that
the point shall play vertically, which, with the strengthening of
successive layers near the point, enables it to break hard mate-
rials ; and secondly, that by this form the nut or seed may be
brought nearer the joining or articulation of the jaw, which gives

NATURAL TllEOLOGV. 233

But tlie species of bii). which belongs to the
birds that live by suction deserves to be described
in its relation to that office. They are what na-
turalists call serrated or deiitated bills ; the inside
of them, towards the edge, behig thickly set with
parallel or concentric rows of short, strong, sharp-

the same advantage that we have when we put a nut nearer the
joint of the nut-cracker, that is, nearer the fulcrum.

One disadvantage of this form and shortness of the bill would
be, that the mandibles could not open wide enough to take in a
large seed ; but it is provided that the upper mandible shall move
upon the skull as well as the lower one, a subject which has not
escaped our author's attention.

The form of the bill of the cross-biil, which he mentions, looks
like an imperfection, but is attended with real advantages. It is
not for crushing, but rather for splitting up a seed into halves and
tearing tlie cones of the fir-tree.

One of the most curious provisions is in the bill of the sea-crow.
The mandibles are compressed into the form of simple laminae,
and the lower mandible projects beyond the upper one ; so that,
as he skims along the water, he dips his bill and lifts his food by
the most appropriate instrument

20*

234 NATURAL THEOLOGY.

pointed prickles. These, though they should be
called teeth, are not for the purpose of mastica-
tion, like the teeth of quadrupeds ; nor yet, as in
fish, for the seizing and retaining of their prey ;
but for a quite different use. They form a filter.
The duck by means of them discusses the mud ;
examining with great accuracy the puddle, the
brake, every mixture which is likely to contain
her food. The operation is thus carried on : —
The liquid or semi-liquid substances in which the
animal has plunged her bill, she draws, by the
action of her lungs, through the narrow interstices
which lie between these teeth, catching, as the
stream passes across her beak, whatever it may
happen to bring along with it that proves agree-
able to her choice, and easily dismissing all the
rest. Now, suppose the purpose to have been,
out of a mass of confused and heterogeneous sub-
stances, to separate for the use of the animal, or
rather to enable the animal to separate for its own,
those few particles which suited its taste and di-
gestion, what more artificial or more commodious
instrument of selection could have been given to
it than this natural filter ? It has been observed
also, (what must enable the bird to choose and
distinguish with greater acuteness, as well, proba-
bly, as what greatly increases its luxury,) that the
bills of this species are furnished with large nerves,
that they are covered with a skin, and that the
nerves run down to the very extremity. In the
curlew, woodcock, and snipe, there are three pairs

Statural theology. 235

of nerves, equal almost to the optic nerve in thick-
ness, which pass first along the roof of the mouth,
and then along the upper chap dow^n to the point
of the bill, long as the bill is."-

But to return to the train of our observations.
The similitude between the bills of birds and the
mouths of quadrupeds is exactly such as, for the
sake of the argument, might be wished for. It is
near enough to show the continuation of the same
plan : it is remote enough to exclude the supposi-
tion of the difference being produced by action or
use. A more prominent contour, or a wider gap,
mio^ht be resolved into the effect of continued
efforts, on the part of the species, to thrust out the
mouth or open it to the stretch. But by what
course of action, or exercise, or endeavour, shall
we get rid of the lips, the gums, the teeth, and
acquire in the place of them pincers of horn ? By
what habit shall we so completely change, not
only the shape of the part, but the substance of
which it is composed? The truth is, if we had
seen no other than the mouths of quadrupeds, we
should have thought no other could have been
formed : little could we have supposed that all the
purposes of a mouth furnished with lips and armed
with teeth could be answered by an instrument
which had none of these — could be suppHed, and
that with many additional advantages, by the hard-

■''^ These are branches of the fifth nerve of the head, which
alone, of all the nine nerves of the brain, bestows sensibility on
the organ of touch.

236 NATURAL THEOLOGY.

ness, and sharpness, and figure of the bills of birds.
Every thing about the animal mouth is mechanical.
The teeth of fish have their points turned back-
ward, like the teeth of a wool or cotton card.
The teeth of lobsters w^ork one against another,
like the sides of a pair of shears. In many insects,
the mouth is converted into a pump or sucker,
fitted at the end sometimes with a wimble, some-
times with a forceps ; by which double provision,
viz., of the tube and the penetrating form of the
point, the insect first bores through the integu-
ments of its prey, and then extracts the juices.
And what is most extraordinary of all, one sort of
mouth, as the occasion requires, shall be changed
into another sort. The caterpillar could not live
without teeth ; in several species the butterfly form-
ed from it could not use them. The old teeth, there-
fore, are cast off with the exuviae of the grub ; a
nev/ and totally different apparatus assumes their
place in the fly. Amid these novelties of form, we
sometimes forget that it is all the while the ani-
mal's mouth ; that, whether it be lips, or teeth, or
bill, or beak, or shears, or pump, it is the same
part diversified ; and it is also remarkable, that,
under all the varieties of configuration with which
we are acquainted, and which are very great, the
organs of taste and smelling are situated near each
other.

III. To the mouth adjoins the gullet : in this
part also, comparative anatomy discovers a differ-
ence of structure adapted to the different necessi-

NATURAL THEOLOGY. 237

ties of the animal. In brutes, because the posture
of their neck conduces httle to the passage of the
aliment, the fibres of the gullet which act in this
business run in two close spiral lines, crossing
each other: in men these fibres run only a little
obliquely from the upper end of the oesophagus to
the stomach, into which, by a gentle contraction,
they easily transmit the descending morsels — that
is to say, for the more laborious deglutition of
animals which thrust their food up instead of
down, and also through a longer passage, a pro-
portionably more powerful apparatus of muscles
is provided — more powerful, not merely by the
strength of the fibres, which might be attributed
to the greater exercise of their force, but in their
collocation, which is a determinate circumstance,
and must have been original.

IV. The gullet leads to the intestines : here, like-
wise, as before, comparing quadrupeds with man,
under a general similitude we meet v/itli appro-
priate differences. The valvulce conniventes, or,
as they are by some called, the semi-lunar valves,
found in the human intestine, are wanting in that
of brutes. These are wrinkles or plates of the
innermost coat of the guts, the effect of which is
to retard the progress of the food through the ali-
mentary canal. It is easy to understand how
much more necessary such a provision may be to
the body of an animal of an erect posture, and in
which, consequently, the weight of the food is
added to the action of the intestine, than in that

238 NATURAL THEOLOGY.

of a quadruped, in which the course of the food,
from its entrance to its exit, is nearly horizontal ;
but it is impossible to assign any cause, except
the final cause, for this distinction actually taking
place. So far as depends upon the action of the
part, this structure was more to be expected in a
quadruped than in a man. In truth, it must in
both have been formed, not by action, but in di-
rect opposition to action and to pressure ; but the
opposition which would arise from pressure is
greater in the upright trunk than in any other.
That theory, therefore, is pointedly contradicted
by the example before us. The structure is found
where its generation, according to the method by
which the theorist would have it generated, is the
most difficult; but, observe, it is found where its
effect is most useful.

The different length of the intestines in carni-
vorous and herbivorous animals has been noticed
on a former occasion. The shortest, I beheve, is
that of some birds of prey, in which the intestiuai
canal is little more than a straight passage from
the mouth to the vent. The longest is in the deer-
kind. The intestines of a Canadian stag, four feet
high, measured ninety-six feet.* The intestine of
a sheep, unravelled, measured ihiriy times the
length of the body. The intestine of a wild cat
is only three times the length of the body. Uni-
versally, where the substance upon which the

♦ Mem. Acad. Paris, 1701, p. 170,

NATURAL THEOLOGY. 239

animal feeds is of slow concoction, or yields its
chyle with more difficulty, there the passage is
circuitous and dilatory, that time and space may
be allowed for the change and the absorption
which are necessary. Where the food is soon
dissolved, or already half assimilated, an unneces-
sary or perhaps hurtful detention is avoided, by
giving to it a shorter and a readier route.

V, In comparing the hones of different animals,
we are struck, in the bones of birds, with a pro-
priety which could only proceed from the wisdom
of an intelligent and designing Creator. In the
bones of an animal which is to fly, the two quali-
ties required are strength and lightness. Where-
in, therefore, do the bones of birds (I speak of the
cylindrical bones) differ in these respects from the
bones of quadrupeds? In three properties: first,
their cavities are much larger in proportion to the
weight of the bone than in those of quadrupeds ;
secondly, these cavities are empty ; thirdly, the
shell is of a firmer texture than is the substance
of other bones. It is easy to observe these par-
ticulars even in picking the wing or leg of a
chicken. Now the weight being the same, the
diameter, it is evident, will be greater in a hollow
bone than in a solid one, and with the diameter,
as every mathematician can prove, is increased,
c<Bteris paribus, the strength of the cylinder or its
resistance to breaking. In a word, a bone of the
same weight would not have been so strong in any

S40 NATURAL THEOLOGY.

Other form ; and to have made it heavier would
have incommoded the animal's flight. Yet this
form could not be acquired by use, or the bone
become hollow^ or tubular by exercise. What ap-
petency could excavate a bone ?

VI. The lungs also of birds, as compared with
the lungs of quadrupeds, contain in them a provi-
sion distinguishingly calculated for this same pur-
pose of levitation, namely, a communication (not
found in other kinds "of animals,) between the air-
vessels of the lungs and the cavities of the body ;
so that, by the intromission of air from one to the^
other, (at the will, as it should seem, of the animal,)
its body can be occasionally puffed out, and its
tendency to descend in the air, or its specific gra-
vity, made less. The bodies of birds are blown
up from their lungs, (which no other animal bodies
are,) and thus rendered buoyant.^^

VII. All birds are oviparous. This likewise
carries on the work of gestation with as little in-
crease as possible of the weight of the body. A
gravid uterus would have been a troublesome bur-
den to a bird in its flight. The advantage in this
respect of an oviparous procreation is, that whilst
the whole brood are hatched together, the eggs
are excluded singly, and at considerable intervals.
Ten, fifteen, or twenty young birds may be pro-

** We have thrown some observations upon this subject into
the Appendix, under the title of " The Relation of the Bodies of
Birds to the Atmosphere."

NATURAL THEOLOGY. 241

duced in one cletch or covey, yet the parent bird
have never been encumbered by the load of more
than one full-grown egg at one time.^^

VIII. A principal topic of comparison between
animals is in their instruments of motion. These
come before us under three divisions — feet, wings,
and fins. I desire any man to say which of the three
is best fitted for its use ; or whether the same con-
summate art be not conspicuous in them all. The
constitution of the elements in which the motion
is to be performed is very different. The animal
action must necessarily follow that constitution.
The Creator, therefore, if w^e might so speak, had
to prepare for different situations, for different
difficulties; yet the purpose is accomplished not
less successfully in one case than in the other.
And as between wings and the corresponding
limbs of quadrupeds, it is accomplished without
deserting the general idea. The idea is modified,
not deserted. Strip a wing of its feathers, and it
bears no obscure resemblance to the fore-leg of a
quadruped. The articulations at the shoulder and
the cubitus are much alike ; and, what is a closer
circumstance, in both cases the upper part of the
limb consists of a single bone, the lower part of
two.

But, fitted up with its furniture of feathers and

54 It has been elsewhere observed, that when predatory birds
gorge themselves, they are sometimes unable to rise on the wing
— a sufficient demonstration that the burden of an offspring would
have unsuited them for flight.

21

242 NATURAL THEOLOGY.

quills, it becomes a wonderful instrument, more
artificial than its first appearance indicates, though
that be very striking ; at least, the use which the
bird makes of its wings in flying is more compli-
cated and more curious than is generally known.
One thing is certain, that if the flapping of the
wings in flight were no more than the reciprocal
motion of the same surface in opposite directions,
either upwards and downwards, or estimated in
any oblique line, the bird would lose as much by
one motion as she gained by another. The sky-
lark could never ascend by such an action as this ;
for, though the stroke upon the air by the under-
side of her wing would carry her up, the stroke
from the upper-side, when she raised her wing
again, would bring her down. In order, there-
fore, to account for the advantage which the bird
derives from her wing, it is necessary to suppose
that the surface of the wing, measured upon the
same plane, is contracted, whilst the wing is drawn
up ; and let out to its full expansion, when it de-
scends upon the air for the purpose of moving the
body by the re-action of that element. Now, the
form and structure of the wing, its external con-
vexity, the disposition, and particularly the over-
lapping, of its larger feathers, the action of the
muscles and joints of the pinions, are all adapted
to this alternate adjustment of its shape and dimen-
sions. Such a twist, for instance, or semirotatory
motion, is given to the great feathers of the wing,
that they strike the air with their flat side, but rise

NATURAL THEOLOGY. 243

from the stroke slantwise. The turning of the
oar in rowing, whilst the rower advances his hand
for a new stroke, is a similar operation to that of
the feather, and takes its name from the resem-
blance. I believe that this faculty is not found in
the great feathers of the tail. This is the place also
for observing that the pinions are so set upon the
body as to bring down the wings not vertically,
but in a direction obliquely tending towards the
tail; — which motion, by virtue of the common
resolution of forces, does two things at the same
time — supports the body in the air, and carries it
forward. The steerage of a bird in its flight is
effected partly by the wings, but in a principal
degree by the tail. And herein we meet with a
circumstance not a little remarkable. Birds with
long legs liave short tails ; and in their flight place
their legs close to their bodies, at the same time
stretching them out backw ards, as far as they can.
In this position the legs extend beyond the rump,
and become the rudder ; supplying that steerage
which the tail could not.

From the wings of birds, the transition is easy
to the fins of fish.^^ They are both, to their re-

^ This subject is necessarily treated at length in the Bridge-
water Treatise of the Hand. We have had occasion to state, that
in the higher division of animated nature, the vertebrata, one plan or
system of bones can be traced through every variety from man to
fishes ; and this is more especially shown by the comparison of the
arm with the anterior extremity of quadrupeds and the wing of
birds, and even with the pectoral fin of the fish. The number of
the bones, and the form and the application of the muscles to them

244 NATURAL THEOLOGY.

spective tribes, the instruments of their motion;
but, in the work which they have to do, there is a
considerable difference, founded in this circum-
stance. Fish, unlike birds, have very nearly
the same specific gravity with the element in
which they move. In the case of fish, therefore,
there is little or no w'eight to bear up ; \\\mt is
w^anted, is only an impulse sufficient to carry the
body through a resisting medium, or to maintain
the posture, or to support or restore the balance
of the body, which is always the most unsteady
w^here there is no w^eight to sink it. For these
offices, the fins are as large as necessary, though
much smaller than wings, their action mechanical,
their position, and the muscles by w^hich they are
moved, in the highest degree convenient. The
following short account of some experiments upon
fish, made for the purpose of ascertaining the use
of their fins, will be the best confirmation of w^hat
we assert. In most fish, besides the great fin, the
tail, w^e find two pairs of fins upon the sides, two
single fins upon the back, and one upon the belly,
or rather between the belly and the tail. The
balancing use of these organs is proved in this
manner. Of the large-headed fish, if you cut off
the pectoral fins — /. e., the pair which lies close
behind the gills — the head falls prone to the
bottom : if the right pectoral fin only be cut off,

vary, but yet they are accommodated in a manner so perfect, that,
on examining any individual among the varieties of the species,
we should say that nothing could be better suited to its purpose.

NATURAL THEOLOGY. 245

the fish leans to that side ; if the ventral fin on
the same side be cut away, then it looses its equi-
librium entirely ; if the dorsal and ventral fins be
cut off, the fish reels to the right and left. When
the fish dies, that is, when the fins cease to play,
the belly turns upwards. The use of the same
parts for motion is seen in the following ob-
servation upon them when put in action. The
pectoral, and more particularly the ventral fins,
serve to i^aise and depress the fish ; when the fish
desires to have a retrograde motion, a stroke for-
w^ard with the pectoral fin effectually produces it ;
if the fish desire to turn either way, a single blow
with the tail the opposite way sends it round at
once ; if the tail strike both ways, the motion pro-
duced by the double lash is progressive, and en-
ables the fish to dart forward with an astonishing
velocity.* The result is, not only in some cases
the most rapid, but in all cases the most gentle,
pliant, easy, animal motion with which we are
acquainted. However, when the tail is cut off,
the fish loses all motion, and gives itself up to
where the water impels it. The rest of the fins,
therefore, so far as respects motion, seem to be
merely subsidiary to this. In their mechanical
use, the anal fin may be reckoned the keel ; the
ventral fins, out-riggers ; the pectoral muscles, the
oars , and if there be any similitude between these
parts of a boat and a fish, observe, that it is not

* Goldsmith, Hist, of An. Nat. vol. vi. p. 154,
21*

246 NATURAL THEOLOGY.

the resemblance of imitation,but the Hkeness which
arises from applying similar mechanical means to
the same purpose.

We have seen that the tail in the fish is the
great instrument of motion. Now, in cetaceous
or warm-blooded fish, which are obliged to rise
every two or three minutes to the surface to take
breath, the tail, unlike what it is in other fish, is
horizontal ; its stroke, consequently, perpendicular
to the horizon, which is the right direction for
sending the fish to the top, or carrying it down to
the bottom.^

^ The poising and motion of fishes in the water has interested
some of our greatest philosophers, as Gahleo and Borelh. It is es-
timated that fishes make their way through a medium which resists
nine hundred times more than the atmosphere. But then, as it
offers a certain resistance to their progress, it resists also the mo-
tion of their tail and fins by which they have their power of pro-
gression. The breadth of the tail of fishes, compared v.ith that of
their fins, and its muscularity and power, declare what is affirmed
to us upon authority — that the tail is the great instrument of their
progression ; and we can see that when the trout darts away, the
force of his motion lays down the fins close upon his body. But
the fins direct him, as outriggers, and the pectoral fins especially,
by raising or depressing the head, give direction to the whole body
under the force of the tail. The lateral fins, and particularly the
pectoral fins, also sustain him in the right position in the water :
without the co-operation of these with the tail, the fish would move
like a boat sculled by one oar at the stern. As the digestion of
fishes, as well as that of other animals, is attended with the extri-
cation of air, and as the intestines are below the centre, the belly
would be turned up but for the action of these lateral fins : as we
see takes place in a dead fish. The tail and fins are the instru-
ments of motion ; but the incessant action of the muscles which
move these is a just matter of admiration. If a fish move with his

NATURAL THEOLOGY. 247

Regarding animals in their instruments of
motion, we have only followed the comparison
through the first great division of animals into
beasts, birds, and fish. If it were our intention to
pursue the consideration further, I should take in
that generic distinction amongst birds, the web-foot
of water-fowl. It is an instance which may be
pointed out to a child. The utility of the web to
water-fowl, the inutility to land-fowl, are so ob-

head down the stream, he must move more rapidly than the water,
or the water gets under the operculum of the gills, and chokes him.
He lies, therefore, continually with his head to the stream. We
may see a trout h'ing for hours stationary, whilst the stream is
running past him ; and they seem to remain so for days and nights.
In salmon-fishing, the fly is played upon the broken water, in the
midst of the torrent, and there the fish shows himself rising from
a part of the river where men could not preserve their footing,
though assisted by poles, or locking their arms together. When
the salmon leaps, he makes extraordinary exertions. Just under
the cataract, and against the stream, he will rush for some yards,
and rise out of the spray six or eight feet ; and amidst the noise of
the water, they may he heard striking against the rock with a
sound like the clapping of the hands. If they find a temporary
lodgement on the shelving rock, they lie quivering and preparing
for another somerset, until they reach the top of the cataract. This
exliibits not only the power of their muscles, assisted by the elasti-
city of their bones, but the force of instinct by which they are led
to seek the shallow streams for depositing their eggs.

The porpoise will swim round and round a ship which is sailing
at fourteen miles an hour : a thing almost as surprising as the fly
circling round the horse's ears for a whole stage.

To all this may be added, that the solid which mathematicians
have discovered, by refined application of the calculus, and have
termed " the solid of least resistance," because it is the conforma-
tion, which is less than an}' other affected by the resistance of any
medium, resembles a fish in its form.

248

NATURAL THEOLOGY.

vious, that it seems impossible to notice the dif-
ference without acknowledging the design. I am
at a loss to know how those who deny the agency
of an intelligent Creator dispose of this example.

There is nothing in the action of swimming, as
carried on by a bird upon the surface of the w ater,
that should generate a membrane between the
toes. As to that membrane, it is an exercise of
constant resistance. The only supposition I can
think of is, that all birds have been originally
water-fowl, and web-footed ; that sparrows, hawks,
linnets, &c., which frequent the land, have, in
process of time, and in the course of many genera-
tions, had this part worn aw^ay by treading upon
hard ground. To such evasive assumptions must
atheism always have recourse ! And after all, it
confesses that the structure of the feet of birds, in
their original form, was critically adapted to their
original destination! The web feet of amphibious
quadrupeds, seals, otters, &:c., fell under the same
observation.

IX. The five senses are common to most large

NATURAL THEOLOGY.

249

animals ; nor have we much difference to remark
in their constitution, or much, however, which is
referable to mechanism.

The superior segacity of animals which hunt
their prey, and which, consequently, depend for
their livelihood upon their nose, is well known in
its use ; but not at all known in the organization
which produces it.

The external eai^s of beasts of prey, of lions,
tigers, wolves, have their trumpet-part, or con-
cavity, standing forward, to seize the sounds
which are before them — viz., the sounds of the
animals which they pursue or watch. The ears of
animals of flight are turned backward, to give
notice of the approach of their enemy from behind,

mi

450

NATURAL THEOLOGY.

whence he may steal upon them unseen. This is
a critical distinction, and is mechanical ; but it
may be suggested, and, I think, not without pro-
bability, that it is the effect of continual habit.

The eyes of animals which follow their prey by
night, as cats, owls, &c., possess a faculty not
given to those of other species, namely, of closing
the pupil entirely. The final cause of which
seems to be this: — It was necessary for such
animals to be able to descry objects with very
small degrees of light. This capacity depended
upon the superior sensibility of the retina ; that
is, upon its being effected by the most feeble im-
pulses. But that tenderness of structure, which
rendered the membrane thus exquisitely sensible,
rendered it also liable to be offended by the access
of stronger degrees of light. The contractile
range therefore of the pupil is increased in these
animals, so as to enable them to close the aperture
^entirely, which includes the power of diminishing

[The figure represents the iris of a Hon. B B, the straight or
converging fibres ; C, the fibres which circle the inner margin of
the iris,]

NATURAL THEOLOGY. 251

it in every degree ; whereby at all times such
portions, and only such portions of light are ad-
mitted, as may be received without injury to the

sense.

There appears to be also in the figure, and in

some properties of the pupil of the eye, an appro-
priate relation to the wants of different animals.
In horses, oxen, goats, sheep, the pupil of the eye
is elliptical; the transverse axis being horizontal;
by which structure, although the eye be placed
on the side of the head, the anterior elongation of
the pupil catches the forward rays, or those which
come from objects immediately in front of the
animal's face.

252 NATURAL THEOLOGY.

CHAPTER XIII.

PECULIAR ORGANIZATIONS.

I BELIEVE that all the instances which I shall
collect under this title might, consistently enough
with technical language, have been placed under
the head of Co?nparative Anatomy. But there
appears to me an impropriety in the use which
that term hath obtained; it being, in some sort,
absurd to call that a case of comparative anatomy,
in which there is nothing to " compare ;" in which
a conformation is found in one animal, which hath
nothing properly answering to it in another. Of
this kind are the examples which I have to pro-
pose in the present chapter ; and the reader will
see that, though some of them be the strongest,
perhaps, he will meet with under any division of
our subject, they must necessarily be of an uncon-
nected and miscellaneous nature. To dispose
them, however, into some sort of order, w^e will
notice, first, particularities of structure which be-
long to quadiupeds, birds, and fish, as such, or to
many of the kinds included in these classes of
animals ; andl hen, such particularities as are con-
fined to one or two species.

I. Along each side of the neck of large quadru-
peds runs a stiff robust cartilage, which butchers

NATURAL THEOLOGY. 253

call the pax-wax. No person can carve the upper
end of a crop of beef without driving his knife
against it. It is a tough, strong, tendinous sub-
stance, braced from the head to the middle of the
back; its office is to assist in supporting the
weight of the head. It is a mechanical provision,
of which this is the undisputed use; and it is
sufficient, and not more than sufficient for the
purpose which it has to execute. The head of an
ox or a horse is a heavy weight, acting at the end
of a long lever (consequently with a great pur-
chase,) and in a direction nearly perpendicular to
the joints of the supporting neck. From such a
force, so advantageously applied, the bones of the
neck w^ould be in constant danger of dislocation,
if they were not fortified by this strong tape. No
such organ is found in the human subject, be-
cause, from the erect position of the head (the
pressure of it acting nearly in the direction of the
spine,) the junction of the vertebrae appears to be
sufficiently secure without it. This cautionary ex-
pedient, therefore, is limited to quadrupeds ; the
care of the Creator is seen where it is wanted.^^

^^ The author is not quite correct here, inasmuch as elastic
ligaments are Uberally supplied in the human spine : a range of
peculiar ligaments, the " ligamenta subflava," run along the course
of the spine, and are highly elastic. The ligamentum nuchce is
that ligament which runs from the prominence of the spine be-
tween the shoulders to the back of the head ; and the student who
hangs his head over his book enjoys the advantage of this elastic
su pport : so that it is strictly a matter comparative ; we may trace
it with increasing strength from the ligament that sustains a man's

22

254 NATURAL THEOLOGY.

II. The oil with which birds preen their fea-
thers, and the organ which supplies it, is a specific
provision for the winged creation. On each side
of the rump of birds is observed a small nipple,
yielding upon pressure a butter-like substance,
which the bird extracts by pinching the pap with
its bill. With this oil or ointment, thus procured,
the bird dresses his coat; and repeats the action
as often as its own sensations teach it that it is in
any part wanted, or as the excretion may be suf-
ficient for the expense. The gland, the pap, the
nature and quality of the excreted substance, the
manner of obtaining it from its lodgement in the
body, the application of it when obtained, form,
collectively, an evidence of intention which it is not
easy to withstand. Nothing similar to it is found
in unfeathered animals. What blind conatus of
nature should produce it in birds ; should not pro-
duce it in beasts ?

III. The air-bladder also of a fish affords a
plain and direct instance, not only of contrivance,
but strictly of that species of contrivance which
we denominate mechanical. It is a philosophical

head, to that which, like the spring of a steelyard, weighs against
the immense head of the elephant.

These elastic ligaments vary witli the length and motion of the
neck. It would be tedious to describe their varieties in tlie camel,
cameleopard, ostrich, &c. We may be satisfied with the fact, that
the elastic hgament is a structure extensively used in the animal
textures, generally coming in aid of the muscles, or as a substi-
tute for them.

NATURAL THEOLOGY. 255

apparatus in the body of an animal. The prin-
ciple of the contrivance is clear ; the application
of the principle is also clear. The use of the
organ to sustain, and, at will, also to elevate, the
body of the fish in the water, is proved by ob-
serving, what has been tried, that, when the
bladder is burst, the fish grovels at the bottom ;
and also, that flounders, soles, skates, which are
without the air-bladder, seldom rise in the water,
and that with effort. The manner in which the
purpose is attained, and the suitableness of the
means to the end, are not difficult to be appre-
hended. The rising and sinking of a fish in
water, so far as it is independent of the stroke
of the fins and tail, can only be regulated by the
specific gravity of the body. When the bladder,
contained in the body of the fish, is contracted,
which the fish probably possesses a muscular
power of doing, the bulk of the fish is contracted
along with it ; whereby, since the absolute weight
remains the same, the specific gravity, which is
the sinking force, is increased, and the fish de-
scends: on the contrary, when, in consequence of
the relaxation of the muscles, the elasticity of the
enclosed and now compressed air restores the di-
mensions of the bladder, the tendency downwards
becomes proportionably less than it was before, or
is turned into a contrary tendency. These are
known properties of bodies immersed in a fluid.
The enamelled figures, or Httle glass bubbles, in a
jar of water, are made to rise and fall by the same

256 NATURAL THEOLOGY.

artifice. A diving-machine might be made to as*
cend and descend, upon the hke principle ; name-
ly, by introducing into the inside of it an air-vessel,
which, by its contraction, would diminish, and by
its distension enlarge, the bulk of the machine it-
self, and thus render it specifically heavier or spe-
cifically lighter than the water which surrounds it»
Suppose this to be done, and the artist to solicit a
patent for his invention : the inspectors of the mo-
del, whatever they might think of the use or value
of the contrivance, could by no possibility enter-
tain a question in their minds, whether it were a
contrivance or not. No reason has ever been as-
signed,— no reason can be assigned, why the con-
clusion is not as certain in the fish as it is in the
machine ; why the argument is not as firm in one
case as the other.

It would be very worthy of inquiry if it were
possible to discover, by what method an animal
which lives constantly in water is able to supply
a repository of air. The expedient whatever it
be, forms part, and perhaps the most curious part
of the provision. Nothing similar to the air-bladder
is found in land-animals ; and a life in the water
has no natural tendency to produce a bag of air.
Nothing can be further from an acquired organi-
zation than this is.^^

^ The aea varies in temperature and pressure at different
depths, and no doubt the texture of the fish^ and especially of its
integument must conform to this variety. The swimming-bladder
13 the means of adjustment by which the fish lives at its native

NATURAL THEOLOGY. 257

These examples mark the attention of the Crea-
tor to the three great kingdoms of his animal
creation, and to their constitution as such. The
example which stands next in point of generality,
belonging to a large tribe of animals, or rather to
various species of that tribe, is the poisonous tooth
of serpents.

I. The fang of a viper is a clear and curious
example of mechanical contrivance. It is a per-
forated tooth, loose at the root : in its quiet state,
lying down flat upon the jaw, but furnished with
a muscle, which, with a jerk, and by the pluck, as
it were, of a string, suddenly erects it. Under the
tooth, close to its root, and communicating with
the perforation, lies a small bag containing the
venom. When the fang is raised, the closing of

depths without waste of animal exertion : such is the power of ex-
pansion of the air-bladder when relieved from the pressure, that,
when a fish is brought up from the greatest depth, it inverts and
thrusts out the viscera from the mouth. We do not see, however,
that naturalists have adverted to the place of tliis swimming-blad-
der. It lies close to the spine, and appears to counterbalance, in
some measure at least, the air in the intestines by being thus
placed above them. In the cetacea, as the whale, their buoyancy
proceeds from the quantity of oil under the skin, especially of
their head, and which it has been observed is bestowed in order
to ensure their readily coming to the surface to breathe when
their natural powers are weakened. For the same reason, that
they may raise their heads to the surface, their tails are horizontal.
In the jelly-fish, those soft animals which float in sheltered estua-
ries, (the physsophora,) there is an air-vessel which they can fill
and empty, by which means they rise or sink at pleasure. Others
(the villela,) raise a sail. Some of this class propel themselves by
taking in water, and suddenly rejecting it.

22*

258 NATURAL THEOLOGY.

the jaw presses its root against the bag under-
neath ; and the force of this compression sends
out the fluid with a considerable impetus through
the tube in the middle of the tooth. What more
unequivocal or eftectual apparatus could be de-
vised for the double purpose of at once inflicting
the wound and injecting the poison ? Yet, though
lodged in the mouth, it is so constituted, as, in its
inoffensive and quiescent state, not to interfere
with the animal's ordinary office of receiving its
food. It has been observed, also, that none of
the harmless serpents, the black snake, the blind
worm, iS^:c., have these fangs, but teeth of an equfel
size ; not moveable as this is, but fixed into the
jaw.

II. In being the property of several different
species, the preceding example is resembled by
that which I shall next mention, which is the hag
of the opossum. This is a mechanical contrivance,
most properly so called. The simplicity of the
expedient renders the contrivance more obvious
than many others, and by no means less certain.
A false skin under the belly of the animal forms a
pouch, into which the young litter are received at
their birth ; where they have an easy and constant
access to the teats ; in which they are transported
by the dam from place to place ; where they are
at liberty to run in and out ; and where they find
a refuge from surprise and danger. It is their
cradle, their asylum, and the machine for their
conveyance. Can the use of this structure be

NATURAL THEOLOGY. 259

doubted of? Nor is it a mere doubling of the
skin ; but is a new organ, furnished with bones
and muscles of its own. Two bones are placed
before the os pubis, and joined to that bone as
their base. These support and give a fixture to
the muscles which serve to open the bag. To
these muscles there are antagonists, which serve
in the same manner to shut it ; and this office they
perform so exactly, that, in the living animal, the
opening can scarcely be discerned, except when
the sides are forcibly drawn asunder.* Is there
any action in this part of the animal, any process
arising from that action, by which these members
could be formed ? any account to be given of the
formation, except design ?

III. As a particularity, yet appertaining to more
species than one, and also as strictly mechanical,
we may notice a circumstance in the structure of
the claws of certain birds. The middle claw of
the heron and cormorant is toothed and notched
like a saw. These birds are great fishers, and
these notches assist them in holding their slippery
prey. The use is evident ; but the structure such,
as cannot at all be accounted for by the effort of
the animal, or the exercise of the part. Some
other fishing birds have these notches in their
hills ; and for the same purpose. The gannet, or
Soland goose, has the side of its bill irregularly
jagged, that it may hold its prey the faster. Nor

♦ Goldsmith, Nat. Hist, vol iv. p. 244.

260 NATURAL THEOLOGY.

can the structure in this, more than in the former
case, arise from the manner of employing the
part. The smooth surfaces, and soft flesh of fish,
were less hkely to notch the bills of birds, than
the hard bodies upon which many other species
feed.

We now come to particularities strictly so called,
as being limited to a single species of animal. Of
these, I shall take one from a quadruped, and one
from a bird.

I. The stomach of the camel is -well known to
retain large quantities of water, and to retain it
unchanged for a considerable length of time. This
property qualifies it for living in the desert. Let
us see, therefore, what is the internal organization,
upon which a faculty so rare and so beneficial de-
pends. A number of distinct sacs or bags (in a
dromedaiy thirty of these have been counted,) are
observed to lie between the membranes of the se-
cond stomach, and to open into the stomach near
the top by small square apertures. Through these
orifices, after the stomach is full, the annexed bags
are filled from it : and the water so deposited is,
in the first place, not liable to pass into the intes-
tines ; in the second place, is kept separate from
solid aliment ; and, in the third place, is out of the
reach of the digestive action of the stomach, or of
mixture with the gastric juice. It appears proba-
ble, or rather certain, that the animal, by the con-
formation of its muscles, possesses the power of
squeezing back this water from the adjacent bags

NATUftAL THEOLOGY. 2G1

into the stomach, whenever thirst excites it to put
this power in action.

II. The tongue of the ivoodpecker is one of those
singularities, which nature presents us with, when
a singular purpose is to be answered. It is a par-
ticular instrument for a particular use ; and what,,
except design, ever produces such? The wood-
pecker lives chiefly upon insects lodged in the
bodies of decayed or decaying trees. For the pur-
pose of boring into the wood, it is furnished with
a bill straight, hard, angular, and sharp. When.
by means of this piercer, it has reached the cells
of the insects, then comes the office of its tongue ;
which tongue is, first, of such a length that the
bird can dart it out three or four inches from the
bill, — in this respect differing greatly from every
other species of bird ; in the second place, it is
tipped with a stiff, sharp, bony thorn ; and, in the
thu'd place, (which appears to me the most re-
.markable property of all,) this tip is dentated on
both sides like the beard of an arrow or the barb
of a hook. The description of the part declares
it& uses. The bird, having exposed the retreats
of the insects by the assistance of its bill, with a
motion inconceivably quick, launches out at them
this long tongue ; transfixes them upon the barbed
needle at the end of it ; and thus draws its prey
within its mouth. If this be not mechanism, what
is ? Should it be said, that, by continual endea-
vours to shoot out the tongue to the stretch, the
woodpecker species may by degrees have length^*

262 NATURAL THEOLOGY.

ened the organ itself, beyond that of other birds,
what account can be given of its form, of its tip 1
how, in particular, did it get its barb, its denta-
tion ? These barbs, in my opinion, wherever they
occur, are decisive proofs of mechanical contri-
vance.^^

^ What could have tempted BufFon to express his pity for this
bird as abject and degraded, it is not easy to conceive : nor why
it should be described as leading an insipid hfe, because con-
tinually employed in boring and hammering the old stump of a
tree. A late naturalist describes the woodpecker as enjoying the
sweet hours of the morning, on the highest branch of the tallest
tree, fluttering and playing with his mate and companions. No
doubt his diligence, perseverance, and energy in plying his beak
is very extraordinary. But, besides the wedge-like strength of the
beak, and the power of the neck to strike with it, there is some-
thing remarkable in its sensibility. That nerve, the fifth pair, on
which we have shown that all the sensibility of the head depends,
transmits a large branch along the inside of the mandibles : and,
as this nei-ve approaches the extremity, it perforates the bone by
innumerable small canals, so as to be given to the horny covering
of the beak, which is thus possessed of a sensibility to feel in the
crevices of the wood, and under the bark ; and the woodpecker is
enabled by this means to direct the tongue, which our author cor-
rectly describes as moving with extraordinary celerity, and with a^
point like a barbed arrow.

We have represented the dissection of the head of this bird
more accurately in its anatomy than is to be found in books. We
offer it because it eslhibits a very curious piece of mechanism, ad*-
justed to the tongue, to enable the animal to thrust it out far, and
with unusual rapidity. A, is the barbed tongue ; B, two slender
elastic ligamentous cartilages, of very peculiar structure and use.
On one extremity they are attached to the bone which supports
the upper mandible ; from this we trace them over the skull down
upon the sides of the neck ; and, with a large sweep, turnins;
under the lower mandible, and so continued into the tongue, and
not terminating until they reach the horny point. C C C, a long

NATURAL THEOLOGY. 263

III. I shall add one more example, for the sake
of its novelty. It is always an agreeable discovery,

muscle which follows these ligamentous cartilages upon their
concave side, arising from the bone of the lower mandible, and so
sweeping round with the cartilages and over the skull, to have
another tixed point at the upper mandible : these protrude the
tongue. Two muscles are seen to arise from the sides of the
larjnix, which are the opponents of the last, and retract the tongue.
Leaving the other parts of the anatomy, we beg the reader's atten-
tion to the action of the muscle C C C, which presents one of
those curious instances observed in comparative anatomy, of a
mechanism adapted to a particular purpose. The tongue is not
only thrust out far by this apparatus, but is shot with great
rapidity, in correspondence with its barbed point. This effect
is produced by the two extremities of the muscle being fixed
points, and the fibres of the muscle itself running on the con-
cave side of the cartilagineous bow, so as to form a smaller circle.
We require no mathematical demonstration to prove that the
tongue must be thrust out to a greater distance than the measure
of contraction of the muscle. Let us tie the line of the fishing-
rod to its slender top, and pull upon it at the butt : the motion of
the top will be very extensive, even when only an inch of the line
is drawn through the rings. This is a pretty accurate representa-
tion of what takes place by the contraction of this protruding
muscle. We have noticed that the upper end of this arch is fixed,
the whole motion must therefore be given to the loose extremity
in the tongue ; and we cannot but observe that this peculiar arch
and muscular ring are adapted for the rapid protrusion of the
tongue ; whilst its retraction is produced by a common muscle,
that is, a muscle running in a straight course.

Another curious part of this apparatus is, that a very large
gland, Avhich pours out a glutinous matter, is embraced and com-
pressed by the action of the circular muscle. This viscid secre-
tion bedewing the tongue furnishes an additional means for the
bird to pick up insects, such as ants, without the necessity of
sticking each with its arrow. Nothing can be more mechanical, or
more happily adapted to its purpose, than the whole of this struc-
ture, and consequently nothing better suited to strengthen the

264

NATURAL THEOLOGY.

NATURAL THEOLOGY.

265

when, having remarked in an animal an extraor-
dinary structure, we come at length to find out an
unexpected use for it. The following narrative
furnishes an instance of this kind. The baby-
roussa, or Indian hog, a species of wild boar,
found in the East Indies, has two lent teeth, more
than half a yard long, growing upwards, and
(which is the singularity) from the upper jaw.
These instruments are not wanted for offence ;
that service being provided for by two tusks issu-
ing from the under jaw, and resembling those of
the common boar : nor does the animal use them
for defence. They might seem, therefore, to be
both a superfluity and an encumbrance. But ob-
serve the event : — the animal sleeps standing ;

argument in the text. Indeed, it is not inferior to the means em-
ployed for giving rapidity of motion to the membrana nictitans of
the eye of the bird.

23

266 NATURAL THEOLOGY.

and, in order to support its head, hooks its upper
tusks upon the branches of trees.^°

^ This notion of the babyroussa sleeping on its feet and hang-
ing by its teeth the while, is a mere fancy. It has arisen from
the difficulty of accounting for the teeth, which rise out from
the mouth, and turn up before the eyes. The better opinion is,
that they guard the eyes in rushing through the thick under-
wood.

NATURAL THEOLOGY. 267

CHAPTER XIV.

PROSPEETIVE CONTRIVANCES.

I CAN hardly imagine to myself a more distin-
guishing mark, and, consequently, a more certain
proof of design, than preparation, — i. e., the pro-
viding of things beforehand, which are not to be
used for a considerable time afterwards : for this
implies a contemplation of the future, which be-
longs only to intelligence.

Of these prospective contrivances, the bodies of
animals furnish various examples.

I. The human teeth afford an instance, not only
of prospective contrivance, but of the completion
of the contrivance being designedly suspended.
They are formed within the gums, and there they
stop ; the fact being, that their farther advance
to maturity would not only be useless to the new-
born animal, but extremely in its way ; as it is
evident that the act of sucking, by which it is for
some time to be nourished, will be performed with
more ease both to the nurse and to the infant,
whilst the inside of the mouth and edges of the
gums are smooth and soft, than if set with hard-
pointed bones. By the time they are wanted the
teeth are ready. They have been lodged within
the gums for some months past, but detained, as
it were, in their sockets, so long as their farther

268 NATURAL THEOLOGY.

protrusion would interfere with the office to which
the mouth is destined. Nature, namely, that in-
telligence which was employed in creation, looked
beyond the first year of the infant's life : yet,
whilst she was providing for functions which were
after that term to become necessary, was careful
not to incommode those which preceded them.
What renders it more probable that this is the ef-
fect of design, is, that the teeth are imperfect,
whilst all other parts of the mouth are perfect.
The lips are perfect, the tongue is perfect ; the
cheeks, the jaws, the palate, the pharynx, the la-
rynx, are all perfect : the teeth alone are not so.
This is the fact with respect to the human mouth :
the fact also is, that the parts above enumerated
are called into use from the beginning ; whereas
the teeth would be only so many obstacles and an-
noyances, if they were there. When a contrary
order is necessary, a contrary order prevails. In
the worm of the beetle, as hatched from the egg,
the teeth are the first things which arrive at per-
fection. The insect begins to gnaw as soon as it
escapes from the shell, though its other parts be
only gradually advancing to their maturity."

What has been observed of the teeth, is true
of the horns of animals ; and for the same reason.
The horn of a calf or a lamb does not bud, or at
least does not sprout to any considerable length,
until the animal be capable of browsing upon its

<*' See the note upon the teeth in the Appendix. The subject is
full of interest.

NATURAL THEOLOGY. 269

pasture ; because such a substance upon the fore-
head of the young animal would very much in-
commode the teat of the dam in the office of
giving suck.

But in the case of the teetJi — of the human
teeth at least, the prospective contrivance looks
still farther. A succession of crops is provided,
and provided from the beginning ; a second tier
being originally formed beneath the first, which do
not come into use till several years afterwards.
And this double or suppletory provision meets a
difficulty in the mechanism of the mouth, which
would have appeared almost insurmountable.
The expansion of the jaw (the consequence of the
proportionable growth of the animal, and of its
skull) necessarily separates the teeth of the first
set, however compactly disposed, to a distance from
one another, which would be very inconvenient.
In due time, therefore, i. e., when the jaw has at-
tained a great part of its dimensions, a new set of
teeth springs up, (loosening and pushing out the old
ones before them,) more exactly fitted to the space
w-hich they are to .occupy, and rising also in such
close ranks, as to allow for any extension of line
which the subsequent enlargement of the head
may occasion.^^

62 The second or permanent set of teeth does not push out the
deciduous or milk teeth. The process is not mechanical. Whilst
yet a tender membrane is around the second tooth, those of the
first set are suffering absorption at their fangs. Another circum-
stance, which shows the provision not to be mechanical, is the

23*

270 NATURAL THEOLOGY,

11. It is not very easy to conceive a more evi-
dently prospective contrivance than that which, in
all viviparous animals, is found in the milk of the
female parent. At the moment the young animal
enters the world there is its maintenance ready for
it. The particulars to be remarked in this econ-
omy are neither few nor slight. We have, first,
the nutritious quality of the fluid, unlike, in this
respect, every other excretion of the body : and in
which nature hitherto remains unimitated, neither
cookery nor chemistry having been able to make
milk out of grass : we have, secondly, the organ
for its reception and retention : we have, thirdly,
the excretory duct annexed to that organ : and we
have, lastly, the determination of the milk to the
breast at the particular juncture when it is about
to be wanted. We have all these properties in
the subject before us ; and they are all indications
of design. The last circumstance is the strongest
of any. If I had been to guess beforehand, I
should have conjectured, that at the time when
there was an extraordinary demand for nourish-
ment in one part of the system, there w^ould be the
least likelihood of a redundancy to supply another
part. The advanced pregnancy of the female has
no intelligible tendency to fill the breasts with
milk. The lacteal system is a constant w:onder ;

wasting of the old alveolar process, and the growth of the new ;
the new alveolar process or socket of the permanent tooth is form-
ing at the time that the portion of the jaw which held the first tooth
firm is yielding by absorption.

NATURAL THEOLOGY. 271

and it adds to other causes of our admiration, that
the number of the teats or paps in each species is
found to bear a proportion to the number of the
young. In the sow, the bitch, the rabbit, the cat,
the rat, which have numerous htters, the paps are
numerous, and are disposed along the whole length
of the belly : in the cow and mare they are few.
The most simple account of this, is to refer it to a
designing Creator."

But in the argument before us, we are entitled
to consider not only animal bodies when framed,
but the circumstance under which they are framed :
and in this view of the subject, the constitution of
many of their parts is most strictly prospective.

III. The eye is of no use, at the time when it is

^ The only parallel to this is the care with which nature secures
the nourishment of the embryon plant, or the chick in the egg.
The lobes of a bean or a pea, and of most seeds, consist of a de-
posit of nutritious matter, and when heat and moisture favour the
developement of the living property, vessels which are scattered in
these lobes or cotyledons commence absorption of the matter, and
carry it to the centre of the plant. It is remarkable that these
lobes, having thus, in the first instance, suppUed the young plant
with nutritious matter, change their office, and, rising above the
surface, become the first leaves. Thus we see how the nourish-
ment is supplied, until the radicle is pushed down into the earth,
and the leaves receive the influence of the atmosphere. So in the
chick, the white or albumen of the egg goes to its nourishment
whilst it is in the shell : but the yolk of the egg is embraced in the
body of the chick when excluded from the shell, and a duct leads
from the membrane enclosing this mass of nutriment into the first
intestine. And thus is the chick nourished, not only whilst includ-
ed in the shell, but also during its first feeble existence, a period
which corresponds with that of lactation in mammalia.

272 NATURAL THEOLOGY,

formed. It is an optical instrument made in a
dungeon ; constructed for the refraction of light to
a focus, and perfect for its purpose, before a ray
of light has had access to it ; geometrically adapt-
ed to the properties and action of an element,
with which it has no communication. It is about
indeed to enter into that communication : and this
is precisely the thing which evidences intention.
It is providing for the future in the closest sense
which can be given to these terms ; for it is pro-
viding for a future change ; not for the then sub-
sisting condition of the animal ; not for any gradual
progress or advance in that same condition ; but
for a new state, the consequence of a great and
sudden alteration, which the animal is to undergo
at its birth. Is it to be believed that the eye was
formed, or, which is the same thing, that the series
of causes was fixed by which the eye is formed,
without a view to this change ; without a prospect
of that condition, in which its fabric, of no use at
present, is about to be of the greatest ; without a
consideration of the qualities of that element, hith-
erto entirely excluded, but with which it was here-
after to hold so intimate a relation ? A young man
makes a pair of spectacles for himself against he
grows old ; for which spectacles he has no want
or use whatever at the time he makes them.
Could this be done without knowing and consider-
inff the defect of vision to which advanced aoje is
subject ? Would not the precise suitableness of
the instrument to its purpose, of the remedy to

NATURAL THEOLOGY. 273

the defect, of the convex lens to the flattened eye,
establish the certainty of the conclusion, that the
case, afterwards to arise, had been considered
beforehand, speculated upon, provided for? all
which are exclusively the acts of a reasoning
mind. The eye formed in one state, for use only
in another state, and in a difterent state, affords
a proof no less clear of destination to a future
purpose ; and a proof proportionably stronger, as
the machinery is more complicated, and the adap-
tation more exact.

IV. What has been said of the eye, holds
equally true of the lungs. Composed of air-
vessels, where there is no air ; elaborately con-
structed for the alternate admission and expulsion
of an elastic fluid, where no such fluid exists;
this great organ, with the whole apparatus be-
longing to it, lies collapsed in the foetal thorax ;
yet in order, and in readiness for action, the
first moment that the occasion requires its ser-
vice. This is having a machine locked up in store
for future use ; which incontestably proves, that
the case was expected to occur in which this use
might be experienced ; but expectation is the pro-
per act of intelligence. Considering the state in
which an animal exists before its birth, I should
look for nothing less in its body than a system of
lungs. It is like finding a pair of bellows in the
bottom of the sea ; of no sort of use in the situa-
tion in which they are found : formed for an
action which was impossible to be exerted ; hold-

274 NATURAL THEOLOGY.

ing no relation or fitness to the element which
surrounds them, but both to another element in
another place.

As part and parcel of the same plan ought to
be mentioned, in speaking of the lungs, the provi-
sionary contrivances of the foramen ovale and
ductus arteriosus. In the foetus pipes are laid for
the passage of the blood through the lungs ; but,
until the lungs be inflated by the inspiration of
air, that passage is impervious, or in a great de-
gree obstructed. What then is to be done? What
would an artist, what would a master, do upon
the occasion ? He would endeavour, most proba-
bly, to provide a temporary passage, which might
carry on the communication required, until the
other was open. Now this is the thing which is
actually done in the heart. Instead of the cir-
cuitous route through the lungs which the blood
afterwards takes before it get from one auricle of
the heart to the other, a portion of the blood
passes immediately from the right auricle to the
left, through a hole placed in the partition which
separates these cavities. This hole anatomists
call the foramen ovale. This is likewise another
cross cut, answering the same purpose, by what
is called the ductus arteriosus, lying between the
pulmonary artery and the aorta. But both expe-
dients are so strictly temporary, that after birth
the one passage is closed, and the tube which
forms the other shrivelled up into a ligament. If
this be not contrivance, what is ?

NATURAL THEOLOGY. 275

But, forasmuch as the action of the air upon
the blood in the lungs appears to be necessary to
the perfect concoction of that fluid, i. e. to the life
and health of the animal, (otherwise the shortest
route might still be the best,) how comes it to
pass that the fcetus lives, and grows, and thrives
without it ? The answer is, that the blood of the
fcetus is the mother's ; that it has undergone that
action in her habit ; that one pair of lungs serves
for both. When the animals are separated a new
necessity arises ; and to meet this necessity as soon
as it occurs an organization is prepared. It is
ready for its purpose ; it only waits for the atmo-
sphere ; it begins to play the moment the air is
admitted to it.''^

^ Does not the whole condition of the embryon go to this argu-
ment ? At first there is a mere jelly, or what appears as such ; a
little farther advanced, and there are bones, and muscles, and
nerves. But these lie quite inactive for a long term ; the nerve
excites to no action ; the muscles do not move ,• the joints are not
exercised, they are perfected slowly. The period of full develope-
ment is not arrived ; they have not yet their stimulus to activity.
The whole then is in a state of preparation. Conduit pipes with-
out their fluids, glands and ducts without their secretions, sensi-
bilities dormant, and a mechanism quite inoperative ; a whole
animal system beautifully contrived, but only in "prospective
contrivance."

276 NATURAL THEOLOGY.

CHAPTER XV.

RELATIONS.

When several different parts contribute to one
effect, or, which is the same thing, when an effect
is produced by the joint action of different instru-
ments ; the fitness of such parts or instruments
to one another for the purpose of producing, by
their united action, the effect, is what I call rela-
tion ; and wherever this is obser^^ed in the works of
nature or of man, it appears to me to carry along
with it decisive evidence of understanding, inten-
tion, art. In examining, for instance, the several
parts of a watch, the spring, the barrel, the chain,
the fusee, the balance, the wheels of various sizes,
forms, and positions, what is it which would take
an observer's attention as most plainly evincing a
construction, directed by thought, deliberation, and
contrivance ? It is the suitableness of these parts
to one another ; first, in the succession and order
in which they act ; and, secondly, with a view to
the effect finally produced. Thus, referring the
spring to the wheels, our observer sees in it that
which originates and upholds their motion ; in the
chain, that which transmits the motion to the
fusee ; in the fusee, that which communicates it
to the wheels ; in the conical figure of the fusee, if

NATURAL THEOLOGY. 277

he refer to the spring, he sees that which corrects
the inequality of its force. Referring the wheels
to one another, he notices, first, their teeth, which
would have been without use or meaning if there
had heen only one wheel, or if the wheels had
had no connexion between themselves, or common
bearing upon some joint effect ; secondly, the cor-
respondency of their position, so that the teeth of
one wheel catch into the teeth of another ; thirdly,
the proportion observed in the number of teeth in
each wheel, which determines the rate of going.
Referring the balance to the rest of the works, he
saw, when he came to understand its action, that
which rendered their motions equable. Lastly, in
looking upon the index and face of the watch, he
saw the use and conclusion of the mechanism, viz.
marking the succession of minutes and hours ; but
all depending upon the motions within, all upon
the system of intermediate actions between the
spring and the pointer. What thus struck his at-
tention in the several parts of the watch he might
probably designate by one general name of" rela-
tion ;" and observing with respect to all cases
whatever, in which the origin and formation of a
thing could be ascertained by evidence, that these
relations v/ere found m things produced by art
and design, and in no other things, he would
rightly deem of them as characteristic of such
productions. To apply the reasoning here de-
scribed to the works of nature.

24

278 NATURAL THEOLOGY.

The animal oeconomy is full, is made up, of
these relations.

I. There are, first, what in one form or other
belong to all animals, the parts and powers which
successively act upon their food. Compare this
action w^ith the process of a manufactory. In
men and quadrupeds the aliment is first broken
and bruised by mechanical instruments of masti-
cation, viz. sharp spikes or hard knobs, pressing
against or rubbing upon one another; thus ground
and comminuted it is carried by a pipe into the
stomach, where it waits to undergo a great chymi-
cal action, which we call digestion : when digested
it is delivered through an orifice, which opens and
shuts, as there is occasion, into the first intestine ;
there, after being mixed with certain proper in-
gredients, poured through a hole in the side of the
vessel, it is further dissolved : in this state the
milk, chyle, or part which is wanted, and which
is suited for animal nourishment, is strained off by
the mouths of very small tubes opening into the
cavity of the intestines ; thus freed from its grosser
parts, the percolated fluid is carried by a long,
winding, but traceable course, into the main stream
of the old circulation ; which conveys it in its pro-
gress to every part of the body. Now I say again,
compare this with the process of a manufactory,
with the making of cider, for example ; with the
bruising of the apples in tlie mill, the squeezing of
them when so bruised in the press, the fermenta-

NATURAL THEOLOGY. 279

tion ill the vat, the bestowing of the Hquor thus
fermented in the hogsheads, the drawing off into
bottles, the pouring out for use into the glass. Let
any one show me any difference between these two
cases as to the point of contrivance. That which
is at present under our consideration, the " rela-
tion " of the parts successively employed, is not
more clear in the last case than in the first. The
aptness of the jaws and teeth to prepare the food
for the St imach is, at least, as manifest as that of
the cider-mill to crush the apples for the press.
The concoction of the food in the stomach is as
necessary for its future use as the fermentation of
the stum in the vat is to the perfection of the li-
quor. The disposal of the aliment afterwards, the
action and change which it undergoes, the route
vrhich it is made to take, in order that, and until
that, it arrive at its destination, is more complex
indeed and intricate, but, in the midst of compli-
cation and intricacy, as evident and certain as is
the apparatus of cocks, pipes, tunnels, for trans-
ferrins: the cider from one vessel to another; of
barrels and bottles for preserving it till fit for use,
or of cups and glasses for bringing it when want-
ed to the lip of the consumer. The character of
the machinery is in both cases this, — that one
part answers to another part, and every part to
the final result.

This parallel between the alimentary operation
and some of the processes of art might be car-
ried further into detail. Spallanzani has remark-

280 NATURAL THEOLOGY.

ed* a circumstantial resemblance between the
stomachs of gallinaceous fowls and the structure
oi corn-mills. Whilst the two sides of the gizzard
perform the office of the mill-stones, the craw or
crop supplies the place of the liopper.

When om' fowls are abundantly supplied with
meat, they soon fill their craw ; but it does not
immediately pass thence into the gizzard ; it al-
ways enters in very small quantities, in proportion
to the progress of trituration, in like manner as,
in a mill, a receiver is fixed above the two large
stones, which serve for grinding the corn, which
receiver, although the corn be pnt into it in bush-
els, allow the grain to dribble only in small quan-
tities into the central hole in the upper mill-stone.

But we have not done with the alimentary his-
tory. There subsists a general relation between
the external organs of an animal by which it pro-
cures its food and the internal powers by wiiich
it digests it. Birds of prey, by their talons and
beaks, are qualified to seize and devour many spe-
cies both of other birds and of quadrupeds. The
constitution of the stomach agrees exactly with
the form of the members. The gastric juice of a
bird of prey, of an owl, a falcon, or a kite, acts
upon the animal fibre alone ; it will not act upon
seeds or grasses at all. On the other hand, the
conformation of the mouth of the sheep or the
ox is suited for browsing upon herbage. Nothing

+ Disc. i. sec. liv.

NATURAL THEOLOGY. 281

about these animals is fitted for the pursuit of
iiviiig prey. Accordingly it has been found by
experiments, tried not many years ago, with per-
forated balls, that the gastric juice of ruminating
animals, such as the sheep and the ox, speedily
dissolves vegetables, but makes no impression
upon animal bodies. This accordancy is still more
particular. The gastric juice, even of granivorous
birds will not act upon the grain whilst whole and
entire. In performing the experiment of digest-
ing with the gastric juice in vessels, the grain must
be crushed and bruised before it be submitted to
the menstruum, that is to say, must undergo by
art, without the body, the preparatory action which
the gizzard exerts upon it within the body, or no
digestion will take place. So strict, in this case,
is the relation between the offices assimed to the
digestive organ, between the mechanical opera-
tion and the chemical process.

II. The relation of the kidneys to the bladder,
and of the ureters to both, i. e., of the secreting
organ to the vessel receiving the secreted liquor,
ajid the pipe laid from one to the other for the
purpose of conveying it from one to the other, is
as manifest as it is amongst the different vessels
employed in a distillery, or in the communications
between them. The animal structure, in this case,
being simple, and the parts easily separated, it
forms an instance of correlation which may be
presented by dissection to every eye, or which,

24*

282 NATURAL THEOLOGY.

indeed, without dissection, is capable of being ap-
prehended by every understanding. This correla-
tion of instruments to one another fixes intention
somewhere : especially when every other solu-
tion is negatived by the conformation. If the
bladder had been merely an expansion of the
ureter, produced by retention of the fluid, there
ought to have been a bladder for each ureter.
One receptacle fed by two pipes issuing from dif-
ferent sides of the body, yet from both conveying
the same fluid, is not to be accounted for by any
such supposition as this.

III. Relation of parts to one another accom-
panics us throughout the whole animal economy.
Can any relation be more simple, yet more con-
vincing than this, that the eyes are so placed as
to look in the direction in which the legs move
and the hands work? It might have happened
very differently if it had been left to chance.
There were at least three quarters of the com-
pass out of four to have erred in. Any consider-
able alteration in the position of the eye or the
figure of the joints would have disturbed the line,
and destroyed the alliance between the sense and
the limbs.

IV. But relations, perhaps, is never so striking
as when it subsists, not between different parts of
the same thing, but between different things. The
relation between a lock and a key is more obvious
than it is between different parts of the lock. A bow

NATURAL THEOLOGY. 283

was designed for an arrow, and an arrow for a bow ;
and the design is more evident for their being
separate implements.

Nor do the works of the Deity want the clear-
est species of relation. The sexes are manifestly
made for each other. They form the grand rela-
tion of animated nature, universal, organic, me-
chanical, subsisting, hke the clearest relations of
art, in different individuals, unequivocal, inexpli-
cable without design.

So much so, that, w^ere every other proof of con-
trivance in nature dubious or obscure this alone
would be sufficient. The example is complete.
Nothing is wanting to the argument. I see no
way whatever of getting over it.

V. The teats of animals which give suck, bear
a relation to the mouth of the suckling progeny,
particularly to the lips and tongue. Here also,
as before, is a correspondency of parts, which parts
subsist in different individuals.

These are general relations, or the relations of
parts which are found either in all animals or in
large classes and descriptions of animals. Parti-
cular relations, or the relations which subsist be-
tween the particular configuration of one or more
parts of certain species of animals, and the parti-
cular configuration of one or more other parts of
the same animal (which is the sort of relation
that is, perhaps, most striking) are such as the
foiiowinsf :

884 NATURAL THEOLOGY.

I. In the swan, the web-foot, the spoon-bill, the
long neck, the thick down, the graminivorous sto-
mach, bear all a relation to one another, inasmuch
as they all concur in one design, that of supplying
the occasions of an aquatic fowl floating upon the
surface of shallow pools of water, and seeking its
food at the bottom. Begin with anyone of these
particularities of structure, and observe how the
rest follow it. The web-foot qualifies the bird
for swimming ; the spoon-bill enables it to graze.
But how is an animal floating upon the surface of
pools of water to graze at the bottom, except by
the mediation of a long neck? A long neck ac-
cordingly is given to it. Again, a warm-blooded
animal which was to pass its life upon water, re-
quired a defence against the coldness of that ele-
ment. Such a defence is furnislied to the swan in
the muft^ in which its body is wrapped. But all
this outward apparatus w^ould have been in vain,
if the intestinal system had not been suited to the
digestion of vegetable substances : I say suited to
the digestion of vegetable substances ; for it is v/eli
known that there are two intestinal systems found
in birds : one with a membranous stomach and a
gastric juice, capable of dissolving animal sub-
stances alone — the other with a crop and gizzard
calculated for the moistening, bruising, and after-
wards digesting, of vegetable aliment.

Or set oflf with any other distinctive part in the
body of the swan; for instance, with the long
neck. The long neck, without the web-foot,

NATURAL THEOLOGY. '285

would have been an encumbrance to the bird ;
yet there is no necessary connexion between a long
neck and a web-foot. In fact they do not usually
go together. How happens it, therefore, that they
meet only when a particular design demands the
aid of both ?

II. This mutual relation arising from a sub-
serviency to a common purpose, is very observable
also in the parts of a rnole. The strong short legs
of that animal, the palmated feet, armed with
sharp nails, the pig-like nose, the teeth, the velvet
coat, the small 'external ear, the sagacious smell,
the sunk protected eye, all conduce to the utilities
or to the safety of its under-ground life. It is a
special purpose, especially consulted throughout.
The form of the feet fixes the character of the
animal. They are so many shovels ; they deter-
mine its action to that of rooting in the ground ;
and everything about its body agrees with its des-
tination. The cylindrical figure of the mole, as
well as the compactness of its form, arising from
the terseness of its limbs, proportionably lessens
its labour ; because, according to its bulk, it there-
by requires the least possible quantity of earth to
be removed for its progress. It has nearly the
same structure of the face and jaws as a swine,
and the same office for them. The nose is sharp,
slender, tendinous, strong, with a pair of nerves
going down to the end of it. The plush covering
which, by the smoothness, closeness, and polish
of the short piles that compose it, rejects the ad-

286 NATURAL THEOLOGY.

hesion of almost every species of earth, defends
the animal from cold and wet, and from the im-
pediment which it would experience by the mould
sticking to its body. From soils of all kinds the
little pioneer comes forth bright and clean. In-
habiting dirt, it is of all animals the neatest.

But what I have always most admired in the
mole is its eyes. This animal occasionally visiting
the surface, and w^anting, for its safety and direc-
tion, to be informed when it does so, or when it
approaches it, a perception of light w^as necessary.
I do not know that the clearness of sight depends
at all upon the size of the organ. What is gained
by the largeness or prominence of the globe of
the eye, is width in the field of vision. Such a
capacity would be of no use to an animal which
w^as to seek its food in the dark. The mole did
not want to look about it ; nor would a large ad-
vanced eye have been easily defended from the
annoyance to which the life of the animal must
constantly expose it. How indeed was the mole,
working its w^ay under ground, to guard its eyes
at all ? In order to meet this difficulty, the eyes
are made scarcely larger than the head of a
corking-pin ; and these minute globules are sunk
so deeply in the skull, and lie so sheltered within
the velvet of its covering, as that any contraction
of wiiat may be called the eye-brows, not only
closes up the apertures which lead to the eyes, but
presents a cushion, as it were, to any sharp or pro-
truding substance which might push against them.

NATURAL THEOLOGY. 287

This aperture, even in its ordinary state is like a
pin-hole in a piece of velvet, scarcely pervious to
loose particles of earth.

Observe, then, in this structure, that which we
call relation. There is no natural connexion be-
tween a small sunk eye and a shovel palmatcd foot.
Palmated feet might have been joined with goggle
eyes ; or small eyes might have been joined with feet
of any other form. What was it therefore which
brought them together in the mole ? That which
brought together the barrel, the chain, and the
fusee in a watch — design; and design in both
cases inferred, from the relation which the parts
bear to one another in the prosecution of a com-
mon purpose. As hath already been observed,
there are different ways of stating the relation,
according as we sat out from a different part. In
the instance before us, we may either consider the
shape of the feet, as qualifying the animal for that
mode of life and inhabitation to which the structure
of the eye confines it; or we may consider the struc-
ture of the eye as the only one which would have
suited with the action to which the feet arc adapted.
The relation is manifest, whichever of the parts re-
lated we place first in the order of our consideration.
In a word, the feet of the mole are made for digging:
the neck, nose, eyes, ears, and skin, are peculiarly
adapted to an under-ground life ; and this is what
I call relation.

2S8 NATURAL THEOLOGY.

CHAPTER XVI.

COMPENSATION.

Compensation is a species of relation. It is
relation when the defects of one part, or of one
organ, are supplied by the structure of another
part, or of another organ. Thus —

I. The short unbending neck of the elephant is
compensated by the length and flexibility of his
proboscis. He could not have reached the ground
without it ; or, if it be supposed that he might have
fed upon the fruit, leaves, or branches of trees,
how was he to drink ? Should it be asked, why
is the elephant's neck so short? it may be snswer-
ed, that the weight of a head so heavy could not
have been supported at the end of a longer lever.
To a form, therefore, in some respects necessary,
but in some respects also inadequate to the occa-
sion of the animal, a supplement is added, which
exactly makes up the deficiency under which he
laboured.

If it be suggested that this proboscis may have
been produced, in a long course of generations, by
the constant endeavour of the elephant to thrust
out its nose, (which is the general hypothesis by
which it has lately been attempted to account for

NATURAL THEOLOGY. 289

the forms of animated nature,) I would ask, How
was the animal to subsist in the mean time — du-
ring the process — until this prolongation of snout
were completed ? What was to become of the
individual whilst the species was perfecting V'^
Our business at present is, simply to point out

^ AVliilst we have before us the daily proof of the capacities of
animals for domestication, in considering their structm-e and their
instincts, we must look back into that long period before man's
creation, when they had not his protection and care. A thousand
concurring testimonies prove that there were periods when the
earth's surface was more suitable for brutes than it" was for the
abode of man ; and when they were grouped together, each specie?
with its enemy, and each with a power of preseiTation, at once to
prevent too great an increase and total extermination. The young
horse, which in his paddock has neither known bad treatment nor
an enemy, will yet shiver and start away from a brindled swinCj
or any animal that is bristled or rough.

Geological researches, so happily combined with comparative
anatomy, give us no room to conjecture that there has been any-
thig like a progressive improvement in the species of animals. They
have been created with all the characters in which they are now
propagated; and had it been otherwise, the species would haA^e be-
come extinct, or they would have lost their place in that balance of
offence and defence by wliich it has pleased the Creator to provide
for their continuance.

One would imagine that an idea so wild, as that an animal
should produce the variet}^ of organs or external instruments
which we see, by an effort — an energy proceeding from itself,
could never have been maintained in an age like the present, when
it is so fully proved that there is no change upon the extremity of
an animal, no additional organ like this of the trunk of the ele-
phant, no variety in its paw or its hoof, but what is attended with
a corresponding alteration in the whole system of the creature —
of its bones, its teeth, its stomach, as well as in its appetites and
desires.

25

290 NATURAL THEOLOGY.

the relation which this organ bears to the peculiar
figure of the animal to which it belongs. And
herein all things correspond. The necessity of the
elephant's proboscis arises from the shortness of
his neck : the shortness of the neck is rendered
necessary by the weight of the head. Were we to
enter into an examination of the structure and
anatomy of the proboscis itself, we should see in
it one of the most curious of all examples of ani-
mal mechanism. The disposition of the ringlets
and fibres, for the purpose, first, of forming a long
cartilaginous pipe ; secondly, of contracting and
lengthening that pipe ; thirdly, of turning it in
every direction at the will of the animal ; with the
superadd ition at the end, of a fleshy production, of
about the length and thickness of a finger, and
performing the office of a finger, so as to pick up
a straw from the ground. These properties of the
same organ, taken together, exhibit a specimen,
not only of design, (which is attested by the ad-
vantage,) but of consummate art, and, as I may
say, of elaborate preparation, in accomplishing
that design.

II. The hook in the wing of a hat is strictly a
mechanical, and, also, a compensating contrivance.
At the angle of its wing there is a bent claw, ex-
actly in the form of a hook, by wliich the bat at-
taches itself to the sides of rocks, caves, and build-
ings, laying hold of crevices, joinings, chinks and
roughnesses. It hooks itself by this claw ; remains
suspended by this hold ; takes its flight from this

NATURAL THEOLOGY. 291

position: which operations compensate for the de-
crepitude of its legs and feet. Without her hook,
the bat would be the most helpless of all animals.
She can neither run upon her feet, nor raise her-
self from the ground. These inabilities are made
up to her by the contrivance in her wing ; and in
placing a claw on that part, the Creator has de-
viated from the analogy observed in winged
animals. A singular defect required a singular
substitute.

III. The crane kind are to live and seek their
food amongst the waters ; yet, having now^eb-foot,
are incapable of swimming. To make up for this
deficiency, they are furnished with long legs for
wading, or long bills for groping, or usually with
both. This is compensation. But I think the
true reflection upon the present instance is, how
every part of nature is tenanted by appropriate
inhabitants. Not only is the surface of deep
waters peopled by numerous tribes of birds that
swim, but marshes and shallow pools are fur-
nished with hardly less numerous tribes of birds
that wade.

IV. The common|?«rro^has, in the structure of
its beak, both an inconveniency and a competisa-
tion for it. When I speak of an inconveniency I
have a view to a dilemma which frequently occurs
in the works of nature — viz., that the peculiarity
of structure by which an organ is made to answer
one purpose necessarily unfits it for some other
purpose. This is the case before us. The upper

292 NATURAL THEOLOGY.

bill of the parrot is so much hooked, and so much
overlaps the lower, that if, as in other birds, the
lower chap alone had motion, the bird could scarce-
ly gape wide enough to receive its food : yet this
hook and overlapping of the bill could not be
spared, for it forms the very instrument by which
the bird climbs, — to say nothing of the use which
it makes of it in breakiug nuts and the hard sub-
stances upon which it feeds. How, therefore, has
nature provided for the opening of this occluded
mouth ? By making the upper chap moveable, as
well as the lower. In most birds, the upper chap
is connected, and makes but one piece, with the
skull ; but in the parrot the upper chap is joined
to the bone of the head by a strong membrane
placed on each side of it, which lifts and depresses
it at pleasure.*

V. The sjyider^s iceh is a compensating contri-
vance. The spider lives upon flies, w^ithout w ings
to pursue them, — a case, one w^ould have thought,
of great difficulty, yet provided for, and provided
for by a resource which no stratagem, no effort of
the animal, could have produced, had not both its
external and internal structure been specifically
adapted to the operation.*^^

^•^ There are few things better suited to remove the disgust into
which young people are betrayed on the view of some natural ob-
jects, than this of the spider. They will find that the most des-
pised creature may become a subject of admiration, and be select-
ed by the naturalist to exhibit the marvellous works of the crea-
tion. The terras given to these insects lead us to expect interest-

♦ Goldsmith's Nat. Hist. vol. v. p. 274.

NATURA.L THEOLOGY. 293

VI. In many species of insects the eye is fixed,
and consequently without the power of turning

ing particulars concerning them, since they have been divided into
vagrants, hunters, swimmers, and water-spiders, sedentary, and
mason-spiders ; thus evincing a variety in their condition, activity,
and mode of hfe ; and we cannot be surprised to find them varying
intlie performance of their vital functions (as, for example, in their
mode of breathing,) as well as in their extremities and instruments.
Of these instruments the most striking is the apparatus for spinning
and weaving, by which they not only fabricate webs to entangle
theh' prey, but form cells for thefr residence and concealment ;
sometimes living in the ground, sometimes under water, yet breath-
ing the atmosphere. Corresponding with their very singular or-
ganization are their instincts. We are familiar wnth the watch-
fulness and voracity of some spiders, when their prey is indicated
by the vibration of the cords of their net-work. Others have the
eye and disposition of the lynx or tiger, and after crouching in con-
cealment, leap upon their victims. Some conceal themselves

25*

294 NATURAL THEOLOGY.

the pupil to the object. This great defect is, how-
ever, perfectly cojiij^ensated, and by a mechanism
which we should not suspect. The eye is a mul-
tiplying-glass with a lens looking in every direc-

under a silken hood or tube, six eyes only projecting. Some bore
a hole in the earth, and line it as finely as if it were done with the
trowel and mortar, and then hang it with delicate curtains. A very
extraordinary degree of contrivance is exhibited in the trap-door
spider. This door, from which it derives its name, has a frame
and hinge on the mouth of the cell, and is so provided that the
claw of the spider can lay hold of it, and whether she enters or
goes out, says Mr. Kerby, the door shuts of itself. But the water
spider has a domicil more curious still : it is under water,
with an opening at the lower part for her exit and entrance ; and
although this cell be under water, it contains air like a diving-bell,
so that the spider breathes the atmosphere. The air is renewed
in the cell in a manner not easily explained. The spider comes
to the surface ; a bubble of air is attracted to its body ; with this
air she descends, and gets under her cell, w^here the air is disenga-
ged and rises into the cell ; and thus, though under water, she lives
in the air. There must be some peculiar property of the surface
of this creature by which she can move in the water surrounded
^^ ith an atmosphere, and live under the water breatliing the air.

The chief instrument by which the spider performs these won-
ders is the spinning apparatus. The matter from which the threads
are spun is a liquid contained in cells ; the ducts from these cells
open upon little projecting teats, and the atmosphere has so imme-
diate an effect upon this liquid, that upon exposure to it, the secre-
tion becomes a tough and strong thread. Twenty four of these
fine strands form together a thread of the tliickness of that of the
silk-worm. We are assured that there are three different sorts of
material thus produced, which are indeed required for the various
purposes to which they are applied — as, for example, to mix up
the earth to form the cells, — to line these cells as with fine cotton,
— to make light and floating threads by which they may be con-
veyed through the air, as well as those meshes which are so geo-
metrically and correctly formed to entrap their prey.

NATURAL THEOLOGY. 295

tion and catching every object. By which means,
ahhough the orb of the eye be stationary, the field
of vision is as ample as that of other animals, and
is commanded on every side. When this lattice-
work was first observed, the multiplicity and mi-
nuteness of the surfaces must have added to the
surprise of the discovery. Adams tells us that
fourteen hundred of these reticulations have been
counted in the two eyes of a drone-bee.

In other cases the compensation is effected by
the number and position of the eyes themselves.
The spider has eight eyes, mounted upon different
parts of the head ; two in front, two in the top of
the head, two on each side. These eyes are with-
out motion, but, by their situation, suited to com-
prehend every view which the wants or safety of
the animal rendered it necessary for it to take.

VII. The Memoirs for the Natural History of
Animals, published by the French Academy, a. d.
1687, furnish us with some curious particulars in
the eye of a cameleon. Instead of two eyelids, it
is covered by an eyelid with a hole in it. This
singular structure appears to be compensatory, and
to answer to some other singularities in the shape
of the animal. The neck of the cameleon is in-
flexible. To make up for this, the eye is so pro-
minent as that more than half of the ball stands
out of the head, by means of which extraordinary
projection the pupil of the eye can be carried by
the muscles in every direction, and is capable of
being pointed towards every object. But then, so

296 NATURAL THEOLOGY.

unusual an exposure of the globe of the eye re-
quires for its lubricity and defence a more than
ordinary protection of eyelid, as well as a more
than ordinary supply of moisture ; yet the motion
of an eyelid, formed according to the common
construction, would be impeded, as it should seem,
by the convexity of the organ. The aperture in
the lid meets this difficulty. It enables the animal
to keep the principal part of the surface of the
eye under cover, and to preserve it in a due state
of humidity without shutting out the light, or with-
out performing every moment a nictitation which
it is probable would be more laborious to this ani-
mal than to others.

VIII. In another animal, and in another part of
the animul economy, the same Memoirs describe
a most remarkable substitution. The reader will
remember what we have already observed con-
cerning the intestinal canal — that its length, so
many times exceeding that of the body, promotes
the extraction of the chyle from the aliment by
giving room for the lacteal vessels to act upon it
through a greater space. This long intestine^
wherever it occurs, is in other animals disposed in
the abdomen from side to side in returning folds.
But in the animal now under our notice the mat-
ter is managed otherwise. The same intention is
mechanically effectuated, but by a mechanism of
a different kind. The animal of which I speak is
an amphibious quadruped, which our authors call
the alopecias or sea-fox. The intestine is straight

NATURAL THEOLOGY. 297

from one end to the other ; but in this straight
and consequently short intestine is a winding,
corkscrew, spiral passage, through which the food,
not without several circumvolutions, and in fact
by a long route, is conducted to its exit. Here
the shortness of the gut is campensated hy the ob-
liquity of the perforation.

IX. But the works of the Deity are known by
expedients. Where we should look for absolute
destitution — where w^e can reckon up nothing but
wants — some contrivance always comes into sup-
ply the privation. A sjiail, without wings, feet, or
thread, climbs up the stalks of plants by the sole
aid of a viscid humour discharged from her skin.
She adheres to the stems, leaves, and fruits of
plants by means of a sticking-plaster. A mussel,
which might seem by its helplessness to lie at the
mercy of every wave that went over it, has the
singular power of spinning strong tendinous threads
by which she moors her shell to rocks and timbers.
A cockle, on the contrary, by means of its stiff
tongue, works for itself a shelter in the sand. The
provisions of nature extend to cases the most des-
perate. A lohstei" has in its constitution a difficulty
so great that one could hardly conjecture before-
hand how nature would dispose of it. In most
animals the skin grows with their growth. If, in-
stead of a soft skin, there be a shell, still it admits
of a gradual enlargement. If the shell, as in the
tortoise, consist of several pieces, the accession of
substance is made at the sutures. Bivalve shells

298 NATURAL THEOLOGY.

grow bigger by receiving an accretion at their
edge ; it is the same with spiral shells at their
mouth. The simplicity of their form admits of
this. But the lobster's shell being applied to the
limbs of the body, as well as to the body itself,
allows not of either of the modes of growth which
are observed to take place in other shells. Its
hardness resists expansion ; and its complexity
renders it incapable of increasing its size by addi-
tion of substance to its edge. How then was the
growth of the lobster to be provided for? Was
room to be made for it in the old shell, or was it
to be successively fitted with new ones? If a
change of shell became necessary, how was the
lobster to extricate himself from his present con-
finement ? how was he to uncase his buckler, or
draw his legs out of his boots ? The process which
fisher men have observed to take place is as fol-
lows : At certain seasons the shell of the lobster
grows soft ; the animal swells its body ; the seams
open, and the claws burst at the joints. When
the shell has thus become loose upon the body, the
animal makes a second effort, and by a tremulous
spasmodic motion casts it off. • In this state the
liberated but defenceless fish retires into holes in
the rock. The released body now suddenly pushes
its growth. In about eight-and-forty hours a fresh
concretion of humour upon the surface, i. e., a new
shell, is formed, adapted in every part to the in-
creased dimensions of the animal. This wonder-
ful mutation is repeated every year.'^*^
^See Appendix.

NATURAL THEOLOGY. 299

If there be imputed defects without compensa-
tion, I should suspect that they were defects only
in appearance. Thus, the body of the sloth has
often been reproached for the slowness of its mo-
tions, which has been attributed to an imperfec-
tion in the formation of its limbs. But it ought
to be observed that it is this slowness which alone
suspends the voracity of the animal. He fasts
durins his migration from one tree to another : and
this fast maybe necessary for the relief of his over-
charged vessels, as well as to allow time for the
concoction of the mass of coarse and hard food
which he has taken into his stomach. The tardi-
ness of his pace seems to have reference to the
capacity of his organs, and to his propensities with
respect to food — i. e., is calculated to counteract
the effects of repletion.

Or there may be cases in which a defect is ar-
tificial, and compensated by the very cause which
produces it. Thus the sheej), in the domesticated
state in which we see it, is destitute of the ordi-
nary means of defence or escape — is incapable
either of resistance or flight. But this is not so
with the wild animal. The natural sheep is swift
and active ; and, if it lose these qualities when it
comes under the subjection of man, the loss is
compensated by his protection. Perhaps there is
no species of quadruped whatever which suffers so
little as this does from the depredation of animals
of prey.

For the sake of making our meaning better un-

300 NATURAL THEOLOGY.

derstood, we have considered this business of com-
pensation under ceriSim jmi^ticulaj'ities of constitu-
tution in which it appears to be most conspicuous.
This view of the subject necessarily limits the in-
stances to single species of animals. But there
ai'e compensations, perhaps not less certain, wiiich
extend over large classes and to large portions of
livinsf nature.

I. In quadrupeds, the deficiency of teeth is usu-
ally compensated by the faculty of rumination. The
sheep, deer, and ox tribe are w^ithout fore-teeth in
the upper jaw.""^ These ruminate. The horse
and ass are furnished with teeth in the upper jaw,
and do not ruminate. In the former class, the
grass and hay descend into the stomach nearly in
the state in which they are cropped from the pas-
ture or gathered from the bundle. In the stomach
they are softened by the gastric juice, which in
these animals is unusually copious : thus softened
and rendered tender, they are returned a second
time to the action of the mouth, where the grind-
ing teeth complete at their leisure the trituration
which is necessary, but which was before left im-
perfect : I say the trituration which is necessary ;
for it appears from experiments that the gastric
fluid of sheep, for example, has no effect in digest-
ing plants unless they have been previously masti-
cated ; that it only produces a slight maceration,
nearly as common water v/ould do in a like de-

^7 See the account of the teeth, in the Appendix.

NATURAL THEOLOGY. 301

gree of heat ; but that when once vegetables are
reduced to pieces by mastication, the fluid then
exerts upon them its specific operation. Its first
effect is to soften them, and to destroy their nat-
ural consistency : it then goes on to dissolve them,
not sparing even the toughest parts, such as the
nerves of the leaves.*

I think it very probable that the gratification
also of the animal is renewed and prolonged by
this faculty. Sheep, deer, and oxen appear to be
in a state of enjoyment whilst they are chewing
the cud : it is then, perhaps, that they best relish
their food.^^

^* Wherever a seed can lodge we find vegetables growing ; and
Vi^herever we find digestible matter there are animals to live upon
it ; and the kind of food determines the organization of the crea-
ture, not resulting from it, but provided for it. The class of rumi-
nants feed on the coarser herbage where the vegetable is in abund-
ance, but the actual nutritious matter is small in quantity compared
with the mass. There is therefore an obvious necessity for a more
complex apparatus to extract the smaller proportion of matter ca-
pable of being animalized : hence the maceration in the first sto-
mach, hence the regurgitation and rumination, nnd the reception
into the second and third stomach, in preparation for the proper
digestion in the last. When the mass is digested, the nutritious
part is still small in proportion to the whole ; and to permit that
smaller portion of aliment to be absorbed and carried into the sys-
tem, the intestinal canal must be long and complex, offering re-
sistance to the rapid descent of the food, and giving it lodgement :
and thus there is always a correspondence between the complica-
tion of the stomach and the length of the intestines, and between
both and the nature of the food. It is further very remarkable, that
when animals of the same species live in different climates, where
there is more or less abundance of vegetable food, there is an adap-
tation of their digestive organs.

♦ Spall. Dis. iii. sect. cxl.

26

302 NATURAL THEOLOGY.

II. In birds, the compensation is still more
striking. They have no teeth at all. What have
they then to make up for this severe want ? I
speak of granivorous and herbivorous birds : such
as common fowls, turkeys, ducks, geese, pigeons,
«fcc. ; for it is concerning these alone that the
question need be asked. All these are furnished
with a peculiar and most powerful muscle, called
\\ie gizzard ; the inner coat of which is fitted up
wath rough plaits, which, by a strong friction
against one another, break and grind the hard ali-
ment as effectually, and by the same mechanical
action, as a coffee-mill would do. It has been
proved by the most correct experiments that the
gastric juice of these birds will not operate upon
the entire grain : not even when softened by water
or macerated in the crop. Therefore, without a
grinding machine within its body, without the tri-
turation of the gizzard, a chicken would have starv-
ed upon a heap of corn. Yet, why should a bill
and a gizzard go together? why should a gizzard
never b^ found where there are teeth ?

Nor does the gizzard belong to birds as such.

Where it is abundant, the configuration of the intestines which is
intended to delay its descent is less complex. Where the food is
more scarce, the intestine is longer, and the valvular obstruction
greater. This has been observed by Sir E, Home, in comparing
the cassowary of Java with the cassowary of New South Wales,
and the American ostrich wilh the same bird inhabiting the deserts
of Africa. The same comparison has been made between the
Leicestershire sheep and the mountain sheep of Scotland.

NATURAL THEOLOGY. 303

A gizzard is not found in birds of prey : their food
requires not to be ground down in a mill. The
compensatory contrivance goes no further than the
necessity. In both classes of birds, however, the
digestive organ within the body bears a strict and
mechanical relation to the external instruments for
procuring food. The soft membranous stomach
accompanies a hooked, notched beak ; short mus-
cular legs ; strong, sharp, crooked talons ; — the car-
tilaginous stomach attends that conformation of bill
and toes w hich restrains the bird to the picking of
seeds or the cropping of plants.oo

^ We have said that it is the object to support animal hfe, and
to give the enjoyment of existence ; and that wherever the means
are afforded of converting a material under the processes of diges-
tion and assimilation, there animals will be found with an appa-
ratus of digestion adapted to the food. Nothing certainly can be
more curious than the vicarious action of the stomach and mouth.
We see, for example, that where the bill precludes mastication in
the mouth, it is performed in the stomach ; and then muscles are
found in the stomach as powerful as those of the jaws and teeth ;
and as to the teeth, or what is equivalent to them, Ave may say
that they are continually renewed. In fact, no mechanical struc-
ture of jaws and teeth could answer the purposes of nature here:
no union of bone and enamel in the tooth could have withstood
the attrition of the gizzard ; and one of the most beautiful and
interesting appliances of nature is the substitution, through the
instinct of the animal, of small stones of hard texture, generally
consisting of silex, introduced within the grasp and action of this
organ. It is a further proof that the mastication, if we may use
the term, is more perfect in the gizzard than where there is the
most complex structure of teeth, and therefore that is the means
of extracting the greater quantity of nutritious matter. Accord-
ingly, there are gizzards in most classes of animals. They are
not only found in birds, but in reptiles. The sea-turtle has what

304 NATURAL THEOLOGY.

III. But to proceed with our compensations. A
very numerous and comprehensive tribe of terres-
trial animals are entirely without feet — yet loco-
motive, and in a very considerable degree swift in
their motion. How is the icant of feet compen-
sated ? It is done by the disposition of the mus-
cles and fibres of the tiunk. In consequence of
the just collocation and by means of the joint ac-
tion of longitudinal and annular fibres — that is to
say, of strings and rings — the body and train of
reptiles are capable of being reciprocally shorten-
ed and lengthened, drawn up and stretched out.
The result of this action is a progressive and in
some cases a rapid movement of the whole body,
in any direction to which the will of the animal
determines it. The meanest creature is a collec-
tion of wonders. The play of the rings in an earth-
worm, as it crawls, the undulatory motion propa-
gated along the body, the beards or prickles with
wiiich the annuli are armed, and which the ani-
mal can either shut up close to its body, or let out
to lay hold of the roughness of the surface upon
which it creeps, and the power arising from all
these of changing its place and position, aff'ord,
when compared with the provisions for motion in

is termed a muscular stomach. Among fishes, the mullet and the
gillaroo trout have muscular stomachs. The cuttle-fish, the nau-
tilus, and even the earth-worm, have a crop and gizzard ; and in-
sects, according as they live on a leaf or suck the blood, have the
same difference in the internal arrangement of the structure for
assimilation as that which distinguishes the ox from the lion.

NATURAL THEOLOGY. 305

Other animals, proofs of new and appropriate me-
chanism. Suppose that we had never seen an ani-
mal move upon the ground without feet, and that
the problem was: Muscular action, i. e., reciprocal
contraction and relaxation being given, to describe
how such an animal might be constructed capable
of voluntarily changing place. Something, per-
haps, like the organization of reptiles might have
been hit upon by the ingenuity of an artist ; or
might have been exhibited in an automaton, by
the combination of springs, spiral wires, and ring-
lets : but to the solution of the problem would not
be denied, surely, the praise of invention and of
successful thought : least of all could it ever be
questioned whether intelligence had been employ-
ed about it or not.'*^

''0 Not unconnected with the subject of the last note is the pro-
gression of animals : and we have none better suited for the ob-
ject of this volume than the consideration of the infinite variety of
the instruments of motion, from the blubber that floats like froth
upon the water, to the eagle or the antelope. The genus medusa of
Linnaeus embraces those animals like jelly which float in the sea.
Some of these, when taken out of the water, will weigh fifty ounces,
and, on being dried, not more than five or six grains. From this it
would appear that they must be of the specific gravity of water,
and hence their peculiar organization and mode of existence;
especially it accounts for their mode of progression, if it can be
called so : since they are in a great measure passive, and float
and are carried by the wind. For this purpose there is a vesicle
or bladder filled with air, which in some rises above the water,
and the animal is dragged as we might imagine a balloon would
be after lighting on the water. The walls of this sac are muscu-
lar, and the animal, by retaining or forcing out the air, can either
take advantage of the wind, and is sometimes moved with great

26*

30G NATURAL THEOLOGY.

velocity, or sink under the surface, and move only with the cur-
rent. There is every reason to believe that the air, which is the
principal means of change of place, is secreted by the animal.

From some of these animals tentacula hang down into the wa-
ter for seizing their food, and perhaps for directing their progress.
They have a power of distending them, or erecting them by
orcing water into their texture, by the contraction of vesicles near
their base. Varieties of these animals hoist a plate or crest out
of the water, which has a still greater resemblance to a sail.

We have alread}'^ noticed the fins of fishes, the wing of the
bird, and the web-foot of the duck. " The meanest creature is,
indeed, a collection of wonders." In the earth-worm or the cater-
pillar, the head, or the anterior part of the body, is projected (and
it is a dfficult problem to produce extension by contraction) till it
touches the ground, and slightly adheres to it, when the posterior
part of the body is drawn forwards. In many wonus or cater-
pillars there are holders discoverable upon minute inspection, and
their anatomy exhibits a perfect set of muscles attached to those
exterior rough points, — by which it is made evident that each of
them is a foot. But nothing is more interesting than to see the
change of the larva to the winged insect, where these muscles
and their appropriate nerves disappear : and new muscles, and
new nerves, and new energies direct the creature that crept an
inch in an hour to outstrip, as we have said, the fleetest horse or
to rise upon the wind ; for those who travel by the new rail-roads
obser\'e bees lo fly round them, and therefore to move above sixty
miles an hour. The contrasts are the most curious between the
flight of the bat and the motion of the mole ; the same organiza-
tion being calculated, with slight adaptation, for the atmosphere,
and for moving under the earth. We might almost give the in-
stance of the perforation of solid calcareous rock by the boring
mollusca, which, by late observations, seems to be accomplished
by means of the foot.

NATURAL THEOLOGY. 307

CHAPTER XVII.

THE RELATION OF ANIMATED BODIES TO INANIMATE

NATURE.

We have already considered relation, and under
different views ; but it was the relation of parts
to parts, of the parts of an animal to other parts of
the same animal, or of another individual of the
same species.

But the bodies of animals hold, in their consti-
tution and properties, a close and important rela-
tion to natures altogether external to their own:
to inanimate substances, and to the specific quali-
ties of these ; e. g., they hold a strict relation to the
ELEMENTS hy wMch they are surrounded.

I. Can it be doubted, whether the ivings of birds
bear a relation to air, and ihe fins of fish to water ?
They are instruments of motion severally suited
to the properties of the medium in which the mo-
tion is to be performed ; which properties are dif-
ferent. Was not this difference contemplated
when the instruments were differently constituted?

II. The structure of the animal ear depends for
its use not simply upon being surrounded by a fluid,
but upon the specific nature of that fluid. Every
fluid would not serve: its particles must repel one
another ; it must form an elastic medium : for it is
by the successive pulses of such a medium that the

308 NATURAL THEOLOGY.

undulations excited by the surrounding body are
carried to the organ ; that a communication is
formed between the object and the sense ; which
must be done, before the internal machinery of the
ear, subtile as it is, can act at all.

III. The organs of voice and respiration are,
no less than the ear, indebted, for the success of
their operation, to the peculiar qualities of the
fluid in w^iich the animal is immersed. They,
therefore, as w^ell as the ear, are constituted upon
the supposition of such a fluid, i. e., of a fluid w ith
such particular properties, being always present.
Change the properties of the fluid, and the organ
cannot act ; change the organ, and the properties
of the fluid would be lost. The structure, there-
fore, of our organs, and the properties of our at-
mosphere, are made for one another. Nor does it
alter the relation, whether you allege the organ to be
made, for the element (which seems the most natu-
ral way of considering it,) or the elements as pre-
pared for the organ.

IV. But there is another fluid with which w'e
have to do; with properties of its own ; wdth laws
of acting, and of being acted upon, totally diflerent
from those of air and water: and that is light.
To this new, this singular element — to qualities
perfectly peculiar, perfectly distinct and remote
from the qualities of any other substance with
which we are acquainted — an organ is adapted,
an instrument is correctly adjusted, not less pecu-
liar amongst the parts of the body, not less singu-

NATURAL THEOLOGY. 309

lar in its form and in the substance of which it is
composed, not less remote from the materials, the
model, and the analogy of any part of the animal
frame, than the element to which it relates is spe-
cific amidst the substances w^ith which we con-
verse. If this does not prove appropriation, I de-
sire to know what would prove it.

Yet the element of light and the organ of vision,
however related in their office and use, have no
connexion whatever in their original. The action
of rays of light upon the surfaces of animals has
no tendency to breed eyes in their heads. The
sun might shine for ever upon living bodies, w^ith-
out the smallest approach towards producing the
sense of sight. On the other hand also, the ani-
mal eye does not generate or emit light.

V. Throughout the universe there is a wonder-
ful proportioning of one thing to another. The
size of animals, the human animal especially, w^hen
considered with respect to other animals, or to the
plants which grow around him, is such as a regard
to his conveniency would have pointed out. A
giant or a pigmy could not have milked goats, reap-
ed corn, or mowed grass; we may add, could not
have rode a horse, trained a vine, shorn a sheep,
with the same bodily ease as we do, if at all. A
pigmy would have been lost amongst rushes, or
carried off by birds of prey.71

It may be mentioned, likewise, that the model

*' See the Appendix, on the bones of huge animals^

310 NATURAL THEOLOGY.

and the materials of the human body being what
they are, a much greater bulk would have broken
down by its own weight. The persons of men
who much exceed the ordinary stature betray this
tendency.

VI. Again, (and which includes a vast variety
of particulars, and those of the greatest impor-
tance,) how close is the suitableness of the earth
and sea to their several inhabitants ; and of these
inhabitants to the places of their appointed resi-
dence !

Take the earth as it is ; and consider the cor-
respondency of the powers of its inhabitants with
the properties and condition of the soil which they
tread. Take the inhabitants as they are ; and con-
sider the substances which the earth yields for
their use. They can scratch its surface, and its
surface supplies all which they want. This is the
length of their faculties : and such is the constitu-
tion of the globe, and their own, that this is suffi-
cient for all their occasions.

When we pass from the earth to the sea, from
land to water, we pass through a great change :
but an adequate change accompanies us of ani-
mal forms and functions, of animal capacities and
wants ; so that correspondency remains. The earth
in its nature is very different from the sea, and
the sea from the earth, but one accords with its
inhabitants as exactly as the other.

YII. The last relation of this kind which I shall
mention is that of sleep to night; and it appears

NATURAL THEOLOGY. 311

to me to be a relation which was expressly in-
tended. Two points are manifest ; first, that the
animal frame requires sleep ; secondly, that night
brings with it a silence and a cessation of activity
which allows of sleep being taken without inter-
ruption and without loss. Animal existence is
made up of action and slumber ; nature has pro-
vided a season for each. An animal which stood
not in need of rest would always live in daylight.
An animal which, though made for action, and
delighting in action, must have its strength re-
paired by sleep, meets, by its constitution, the re-
turns of day and night. In the human species,
for instance, were the bustle, the labour, the mo-
tion of life upheld by the constant presence of
light, sleep could not be enjoyed without being
disturbed by noise, and without expense of that
time which the eagerness of private interest would
not contentedly resign. It is happy, therefore, for
this part of the creation, I mean that it is con-
formable to the frame and wants of their consti-
tution, that nature, by the very disposition of her
elements, has commanded, as it were, and im-
posed upon them, at moderate intervals, a general
intermission of their toils, their occupations, and
pursuits.

But it is not for man, either solely or princi-
pally, that night is made. Inferior but less per-
verted natures taste its solace, and expect its re-
turn with greater exactness and advantage than
he does. I have often observed, and never ob-

312 NATURAL THEOLOGY.

served but to admire, the satisfaction, no less than
the regularity, with which the greatest part of the
irrational world yield to this soft necessity, this
grateful vicissitude ; how comfortably the birds of
the air, for example, address themselves to the
repose of the evening, with what alertness they
resume the activity of the day.

Kor does it disturb our argument to confess
that certain species of animals are in motion dur-
ing the night, and at rest in the day. With res-
pect even to them, it is still true that there is a
change of condition in the animal, and an external
change corresponding with it. There is still the
relation, though inverted. The fact is, that the
repose of other animals sets these at liberty, and
invites them to their food or their sport.

If the relation of sleep to nighty and, in some
instances, its converse, be real, we cannot reflect
without amazement upon the extent to which it
carries us. Day and night are things close to us ;
the change applies immediately to our sensations;
of all the phenomena of nature, it is the most ob-
vious and the most familiar to our experience ;
but, in its cause, it belongs to the great motions
wiiich are passing in the heavens. Whilst the
earth glides round her axle, she ministers to the
alternate necessities of the animals dwelling upon
her surface, at the same time that she obeys the
influence of those attractions which regulate the
order of many thousand w^orlds. The relation,
therefore, of sleep to night is the relation of the

NATURAL THEOLOGY. 313

inhabitants of the earth to the rotation of their
globe ; probably it is more, it is a relation to the
system of which that globe is a part ; and, still
further, to the congregation of systems of which
theirs is only one. If this account be true, it con-
nects the meanest individual with the universe it-
self, — a chicken roosting upon its perch with the
spheres revolving in the firmament."^^

''^ Nothing is more true than that the strength of the bones and
the power of the muscles stand in intimate relation with the
weight of the body, that is, also, in relation with the attraction of
the globe itself. It is no less certain that many of the living pro-
perties of animals, the condition of the nei-vous system, and the
alternation of exertion and repose in the muscular system, are re-
lated to the change of day and night, or to the revolving of our
planet upon its axis. In man we may see a slight deviation in
his habits and occupations from this correspondence with the suc-
cession of light and darkness ; yet he enjoys a return of energy
and elasticity of spirits, which is followed by weariness and ex-
haustion ; and health will not long continue without yielding to
the alternate condition of activity and repose. In nothing do we
see the benevolence of the Creator more than in the continued
gratification consequent on this arrangement alone, and more es-
pecially in the brutes. It is not a mere effect of hght and the
freshness of the morning which produces the almost universal
animation and activity of that time of day ; for to many animals
the light of day is the signal to seek repose ; and that it is not the
mere necessity which brings animals abroad at night, in order to
feed secluded, or escape their enemies, we know from this, that
their organs are adapted to the obscurer light, and not their organs
only, but their propensities ; for they are as full of activity and en-
joyment as the things of day. The history of pulmonary and
other complaints indicates a curious connexion between the func-
tions of the body and the revolution of time or alternations of day
and night.

27

314 NATURAL THEOLOGY.

VIII. But if any one object to our representa-
tion, that the succession of day and night, or the
rotation of the earth upon which it depends, is
not resolvable into central attraction, we will refer

But the most remarkable accommodation of the economy of
animals, and of the property of life itself in them, regards the
changes of the year rather than the diurnal change. How
much this prevails in the vegetable world, we have only to look
around us fully to comprehend. With the diminution of heat ve-
getation is nipped, the ova of insects locked up, and the food of
many animals withdrawn. Some animals could not be protected
by an instinct of migration, being without the means of passage :
the bat could not fly away with the swallow, nor the hedgehog
and dormouse travel with the deer. To sustain the animal heat
against the low temperature of the surrounding atmosphere, re-
quires a vigorous circulation of the blood, and a plentiful and un-
interrupted supply of food. Many animals must, therefore, have
died during the winter, had not nature supplied a means of their
continuance in life beyond the ingenuity of man to conceive. The
warmth of their clothing, and the instincts to build themselves a
warm habitation, which we should almost say were the exercise
of ingenuity, are insufficient. To sustain life they must hold it
by a new tenure. Accordingly the necessity for food is removed ;
the activity of the circulation is diminished remarkably ; a torpor
seizes upon every living faculty, and they fall into what seems a
long sleep. Yet it is not sleep, but a new condition of existence,
in which life is preserved without the necessity for food, and when
all the functions of the system are let down to a lower state of ac-
tivity. And justly, therefore, it has been said that in these tilings
we trace the benevolence of the Creator, "who did not cast his
living creatures into the world to prosper or perish as they might
find it suited to them or not, but fitted together with the nicest
skill the M'orld and the constitution which he gave to its inhabi-
tants ; so fashioning it, that light and darkness, sun and air, moist
and dry, should become their ministers and benefactors, the un-
wearied and unfailing causes of their well-being." — WhcweWs
Brids;eivater Treatise.

NATURAL THEOLOGY. 315

him to that which certainly is, — to the change of
the seasons. Now the constitution of animals sus-
ceptible of torpor bears a relation to winter simi-
lar to that which sleep bears to night. Against
not only the cold, but the want of food, which the
approach of winter induces, the Preserver of the
world has provided in many animals by migration,
in many others by torpor. As one example out
of a thousand, the bat, if it did not sleep through
the winter, must have starved ; as the moths and
flying insects upon which it feeds disappear. But
the transition from summer to winter carries us
into the very midst of physical astronomy, that is
to say, into the midst of those laws which govern
the solar system at least, and probably all the
heavenly bodies.

316 NATURAL THEOLOGY.

CHAPTER XVIII.

INSTINCTS.

The order may not be very obvious by which I
place instincts next to relations. But I consider
them as a species of relation. They contribute,
along with the animal organization, to a joint ef-
fect, in which view they are related to that orga-
nization. In many cases they refer from one ani-
mal to another animal; and, when this is the case,
become strictly relations in a second point of view.

An INSTINCT is a propensity prior to experience
and independent of instruction. We contend that
it is by instinct that the sexes of animals seek
each other ; that animals cherish their offspring ;
that the young quadruped is directed to the teat
of its dam ; that birds build their nests and brood
with so much patience upon their eggs ; that in-
sects which do not sit upon their eggs deposit
them in those particular situations in which the
young when hatched find their appropriate food :
that it is instinct which carries the salmon, and
some other fish, out of the sea into rivers, for the
purpose of shedding their spawn in fresh water.

We may select out of this catalogue the incu-
bation of eggs. I entertain no doubt but that a

NATURAL THEOLOGY. 317

couple of sparrows hatched in an oven, and kept
separate from the rest of their species, would pro-
ceed as other sparrows do in every office which
related to the production and preservation of their
brood. Assuming this fact,'" the thing is inexpli-
cable upon any other hypothesis than that of an
instinct impressed upon the constitution of the
animal. For, first, what should induce the female
bird to prepare a nest before she lays her eggs ?
It is in vain to suppose her to be possessed of the
faculty of reasoning ; for no reasoning will reach

"3 There can be very little doubt of this assumption being ac-
cording to the fact. Nevertheless, as the experiment has proba-
bly not been actually made, there is no harm in mentioning one
or two examples of the same import, and which are ascertained
by repeated observation. When caterpillars bred upon a tree are
shaken off and fall for the first time upon the ground, they imme-
diately regain the tree by crawling up as quick as they can.
Again — it is a very general law of insects, that the grub feeds
upon a food which the parent does not eat, and yet the latter
makes provision for the grub. Thus the solitary wasp deposits
its eggs, each in a hole, and then collects a certain number of
green worms, which she rolls up and deposits in the same hole,
over the egg. When the grub is hatched, it feeds upon these
worms until transformed into a young wasp. And here two
things are remarkable : first, the wasp itself never feeds upon the
worm, or indeed on any animal food ; and next, M. Reaumur
found that she provides just enough of the worms to sustain the
grub till it becomes a fly, and changes its food. Our author
dwells afterwards upon the application to the argument of the fact
that the parent insect never sees its young. The arcliitecture of
bees affords perhaps the most striking illustration ; for those which
have been taken without ever having any communication with the
former race, build precisely in the accustomed manner. See the
next note.

27*

318 NATURAL THEOLOGY.

the case. The fullness or distension which she
might feel in a particular part of the body, from
the growth and solidity of the egg within her,
could not possibly inform her that she w^as about
to produce something which, when produced, was
to be preserved and taken care of. Prior to ex-
perience there was nothing to lead to this infer-
ence, or to this suspicion. The analogy was all
against it ; for, in every other instance, what is-
sued from the body w^as cast out and rejected.

But, secondly, let us suppose the egg to be pro-
duced into day ; how should birds know that their
eggs contain their young ? There is nothing
either in the aspect or in the internal composition
of an egg wiiich could lead even the most daring
imagination to conjecture that it was hereafter to
turn out from under its shell a living perfect bird.
The form of the egg bears not the rudiments of a
resemblance to that of the bird. Inspecting its
contents, we find still less reason, if possible, to
look for the result which actually takes place. If
we should go so far as, from the appearance of
order and distinction in the disposition of the li-
quid substances which we noticed in the eggj to
guess that it might be designed for the abode and
nutriment of an animal, (which would be a very
bold hypothesis,) we should expect a tadpole dab-
bling in the slime, much more than a dry, winged,
feathered creature, a compound of parts and pro-
perties impossible to be used in a state of confine-
ment in the egg, and bearing no conceivable rela-

NATURAL THEOLOGY. 319

tion, either in quality or material, to any thing ob-
served in it. From the white of an egg, would
any one look for the feather of a goldfinch ? or ex-
pect from a simple uniform mucilage the most
complicated of all machines, the most diversified
of all collections of substances ? Nor would the
process of incubation, for some time at least, lead
us to suspect the event. Who that saw red
streaks shooting in the fine membrane which di-
vides the white from the yolk, would suppose that
these w^ere about to become bones and limbs ?
Who that espied two discoloured points first mak-
ing their appearance in the cicatrix, would have
had the courage to predict that these points were
to grow into the heart and head of a bird? It is
diflicult to strip the mind of its experience. It is
difficult to resuscitate surprise when familiarity
has once laid the sentiment asleep. But could we
forget all that we know, and which our sparrows
never knew, about oviparous generation — could
we divest ourselves of every information but what
we derived from reasoning upon the appearances
or quality discovered in the objects presented to
us — I am convinced that Harlequin coming out
of an egg upon the stage is not more astonishing
to a child than the hatching of a chicken both
would be, and ought to be, to a philosopher."'*

'''* The manner in which the chicken breaks the egg is one of
the most wonderful operations of instinct, and is a process marked
by the uniformity of instincts. For as all bees build alike with
respect to the size of the cell and the angles at which its planes

320 NATURAL THEOLOGY.

But admit the sparrow by some means to know
that within that egg was concealed the principle
of a fliture bird : from what chemist was she to
learn that warmth was necessary to bring it to
maturity, or that the degree of warmth imparted
by the temperature of her own body was the de-
gree required ?

To suppose, therefore, that the female bird acts
in this process from a sagacity and reason of her
own, is to suppose her to arrive at conclusions
which there are no premises to justify. If our
sparrow, sitting upon her eggs, expect young spar-
rows to come out of them, she forms, I will ven-
ture to say, a wild and extravagant expectation,
in opposition to present appearances and to pro-
bability. She must have penetrated into the order
of nature further than any faculties of ours will
carry us ; and it hath been well observed, that this
deep sagacity, if it be sagacity, subsists in conjunc-
tion wath great stupidity, even in relation to the
same subject. " A chemical operation," says Ad-

are inclined, so M. Reaumur found that all chickens chip the
shell in the same direction, from left to right ; and that the circle
in which they chip, invariably cuts the egg at right angles to its
transverse axis, and not obliquely. The instrument wliich the
chicken employs is a small protuberance on its upper mandible,
called the bill-scale, which has no other use,. and accordingly drops
off soon after the bird is hatched. If any one should consider this
as a different operation in kind from those usually ascribed to in-
stinct in animals that are formed, a little reflection will probably
show him the impossibility of drawing any such line of distinction.
See the Dissertation on Instinct, Appendix.

NATURAL THEOLOGY. 321

dison, " could not be followed with greater art or
diligence than is seen in hatching a chicken ; yet
is the process carried on without the least glim-
mering of thought or common sense. The hen
will mistake a piece of chalk for an egg — is in-
sensible of the increase or diminution of their num-
ber — does not distinguish between her own and
those of another species — is frightened ^vhen her
supposititious breed of ducklings take the water."
But it will be said, that what reason could not
do for the bird, observation, or instruction, or tra-
dition might. Now if it be true t hat a couple of
sparrows, brought up from the first in a state of
separation from all other birds, would build their
nest, and brood upon their eggs, then there is an
end of this solution. What can be the traditionary
knowledge of a chicken hatched in an oven ?

Of young birds taken in their nests, a few spe-
cies breed when kept in cages ; and they which
do so build their nests nearly in the same manner
as in the wild state, and sit upon their eggs. This
is sufficient to prove an instinct without having
recourse to experiments upon birds hatched by
artificial heat, and deprived from their birth of all
communication with their species ; for we can
hardly bring ourselves to believe that the parent
bird informed her unfledged pupil of the history
of her gestation, her timely preparation of a nest,
her exclusion of the eggs, her long incubation, and
of the joyful eruption at last of her expected off-
spring : all which the bird in the cage must have

322 NATURAL THEOLOGY.

learnt in her infancy if we resolve her conduct in-
to institution.

Unless we will rather suppose that she remem-
bers her own escape from the egg — had atten-
tively observed the conformation of the nest in
which she was nurtured — and had treasured up
her remarks for future imitation; which is not only
extremely improbable (for who that sees a brood
of callow birds in their nest can believe that they
are taking a plan of their habitation ?) but leaves
unaccounted for one principal part of the difficulty,
" the preparation of the nest before the laying of
the egg." This she could not gain from observa-
tion in her infancy.

It is remarkable also, that the hen sits upon
eggs which she has laid without any communica-
tion with the male, and which are therefore ne-
cessarily unfruitful. That secret she is not let into.
Yet if incubation had been a subject of instruction
or of tradition, it should seem that this distinction
would have formed part of the lesson ; whereas
the instinct of nature is calculated for a state of
nature — the exception here alluded to taking place
chiefly, if not solely, amongst domesticated fowls,
in which nature is forced out of her course.

There is another case of oviparous economy,
which is still less likely to be the eftect of educa-
tion than it is even in birds, namely, that of moths
and butterflies, which deposit their eggs in the pre-
cise substance — that of a cabbage, for example
— from which, not the butterfly herself, but the

NATURAL THEOLOGY. 323

caterpillar which is to issue from her egg, draws
its appropriate food. The butterfly cannot taste
the cabbage : cabbage is no food for her ; yet in
the cabbage, not by chance, but studiously and
electively, she lays her eggs. There are, amongst
many other kinds, the willow-caterpillar and the
cabbage-caterpillar ; but we never find upon a wil-
low the caterpillar which eats the cabbage, nor the
converse. This choice, as appears to me, cannot
in the butterfly proceed from instruction. She
had no teacher in her caterpillar state. She never
knew her parent. I do not see, therefore, how
knowledge acquired by experience, if it ever were
such, could be transmitted from one generation to
another. There is no opportunity either for in-
struction or imitation. The parent race is gon*-
before the new brood is hatched. And if it be
original reasoning in the butterfly, it is profound
reasoning indeed. She must remember her cater-
pillar state, its tastes and habits, of which memory
she shows no signs whatever. She must conclude
from analogy, (for here her recollection cannot
serve her,) that the little round body which drops
from her abdomen will at a future period produce
, a living creature, not like herself, but like the cater-
pillar which she remembers herself once to have
been. Under the influence of these reflections,
she goes about to make provision for an order of
things which she concludes will some time or
other take place. And it is to bie observed, that
not a few out of many, but that all butterflies

324 NATURAL THEOLOGY.

argue thus ; all draw this conclusion ; all act upon
it.

But suppose the address, and the selection, and
the plan, which we perceive in the preparations
which many irrational animals make for their
young, to be traced to some probable origin, still
there is left to be accounted for that which is the
source and foundation of these phenomena, that
which sets the whole at work, the (fropy/], the pa-
rental affection, which I contend to be inexplicable
upon any other hypothesis than that of instinct.

For we shall hardly, I imagine, in brutes, refer
their conduct towards their offspring to a sense of
duty or of decency, a care of reputation, a com-
pliance with public manners, with public laws, or
wdth rules of life built upon a long experience of
their utility. And all attempts to account for the
parental affection from association, I think, fail.
With what is it associated ? Most immediately
with the throes of parturition, that is, with pain,
and terror, and disease. The more remote, but
not less strong association, that w^hich depends
upon analogy, is all against it. Every thing else
which proceeds from the body is cast away and
rejected. In birds is it the egg which the hen
loves ? or is it the expectation which she cherishes
of a future progeny that keeps her upon her nest?
What cause has she to expect delight from her
progeny ? Can any rational answer be given to
the question, why, prior to experience, the brood.

NATURAL THEOLOGY. 325

ing hen should look for pleasure from her chickens?
It does not, I think, appear that the cuckoo ever
knows her young ; yet, in her way, she is as care-
ful in making provision for them as any other bird.
She does not leave her egg in every hole.

The salmon suffers no surmountable obstacle to
oppose her progress up the stream of fresh rivers.
And what does she do there ? She sheds a spawn,
which she immediately quits in order to return to
the sea ; and this issue of her body she never af-
terwards recognises in any shape whatever. Where
shall we find a motive for her efforts and her per-
severance ? Shall we seek it in argumentation
or in instinct ? The violet crab of Jamaica per-
forms a fatiguinj; march of some months' con-
tinuance from the mountains to the sea-side. When
she reaches the coast, she casts her spawn into
the open sea, and sets out upon her return
home.

Moths and butterflies, as hath already been ob-
served, seek out for their eggs those precise situa-
tions and substances in which the offspring cater-
pillar will find its appropriate food. That dear
caterpillar the parent butterfly must never see.
There are no experiments to prove that she would
retain any knowledge of it if she did. How shall
we account for her conduct ? I do not mean for
her art and judgement in selecting and securing a
maintenance for her young, but for the impulse
upon which she acts. What should induce her to

28

326 NATURAL THEOLOGY.

exert any art, or judgement, or choice, about the
matter? The undisclosed grub, the animal which
she is destined not to know, can hardly be the ob-
ject of a particular affection, if we deny the in-
fluence of instinct. There is nothing therefore
left to her, but that of which her jjature seems in-
capable, an abstract anxiety for the general pre-
servation of the species — a kind of patriotism —
a solicitude lest the butterfly race should cease
from the creation.

Lastly, the principle of association will not ex-
plain the discontinuance of the affectipn when the
young animal is grown up. Association operating
in its usual way w^ould rather produce a contrary
eflfect. The object would become more necessary
by habits of society ; whereas birds and beasts,
after a certain time, banish their offspring, disown
their acquaintance, seem to have even no know-
ledge of the objects which so lately engrossed the
attention of their minds and occupied the industry
and labour of their bodies. This change, in dif-
ferent animals, takes place at different distances
of time from the birth ; but the time alw ays cor-
responds with the ability of the young animal to
maintain itself, never anticipates it. In the spar-
row tribe, w hen it is perceived that the young brood
can fly and shift for themselves, then the parents
forsake them for ever ; and, though they continue
to live together, pay them no more attention than
they do to other birds in the same flock.* I be-

♦ Goldsmith's Natural History, vol. iv. p. 244.

NATURAL THEOLOGY. 327

lieve the same thing is true of all gregarious quad-
rupeds."^

In this part of the case the variety of resources,
expedients, and materials which animals of the
same species are said to have recourse to under
ditferent circumstances, and when differently sup-
plied, makes nothing against the doctrine of in-
stincts. The thing which we want to account for
is the propensity. The propensity being there, it
is probable enough that it may put the animal
upon different actions according to different exi-
gencies. And this adaptation of resources may
look like the effect of art and consideration rather
than of instinct ; but still the propenshy is instinc-
tive. For instance, suppose what is related of the
woodpecker to be true, that in Europe she de-
posits her eggs in cavities which she scoops out
in the trunks of soft or decayed trees, and in
which cavities the eggs lie concealed from the eye,
and in some sort safe from the hand of man, but
that, in the forests of Guinea and the Brazils,
which man seldom frequents, the same bird hangs

" In the natural and instinctive feelings of man, as contradis-
tinguished from those which have been modified by reason, some-
thing of the same kind may be observed. The mutual relation of
protection and dependence, produced by power and weakness, is
of this description. A helpless infant excites much stronger sym-
pathy in the mother than the child that can shift for itself; and
hence the partiality, accompanied by blindness to defects, vv^hich
most parents entertain towards children whose natural deficiency,
whether bodily or mental, throws tliem on their care long after the
season of infancy.

328 NATURAL THEOLOGY.

her nest on the twigs of tall trees, thereby placing
them out of the reach of monhcys and snahes —
i. e., that in each situation she prepares against the
danger which she has most occasion to apprehend.
Suppose, I say, this to be true, and to be alleged,
on the part of the bird that builds these nests, as
evidence of a reasoning and distinguishing pre-
caution : still the question returns, whence the
propensity to build at all?

Nor does parental affection accompany genera-
tion by any universal law of animal organization,
if such a thing were intelligible. Some animals
cherish their progeny with the most ardent fond-
ness, and the most assiduous attention ; others
entirely neglect them; and this distinction always
meets the constitution of the young animal with
respect to its w^ants and capacities. In many, the
parental care extends to the young animal ; in
others, as in all oviparous fish, it is confined to
the egg, and even as to that, to the disposal of it
in its proper element. Also, as there is genera-
tion without parental affection, so is there parental
instinct, or what exactly resembles it, without
generation. In the bee tribe, the grub is nurtured
neither by the father nor the mother, but by the
neutral bee. Probably the case is the same with
ants.

I am not ignorant of the theory which resolves
instinct into sensation, which asserts that what
appears to have a view and relation to the future,
is the result only of the present disposition of the

NATURAL THEOLOGY. 329

anirnal's body, and of pleasure or pain experienced
at the time. Thus the incubation of eggs is ac-
counted for by the pleasure which the bird is sup-
posed to receive from the pressure of the smooth
convex surface of the shells against the abdomen,
or by the relief which the mild temperature of the
egg may afford to the heat of the lower part
of the body, w hich is observed at this time to be
increased beyond its usual state. This present
gratification is the only motive with the hen for
sitting upon her nest; the hatching of the chickens
is, with respect to her, an accidental consequence.
The affection of viviparous animals for their young
is in like manner solved by the relief, and perhaps
the pleasure, which they perceive from giving
suck. The young animal's seeking, in so many
instances, the teat of its dam, is explained from
its sense of smell, which is attracted by the odour
of milk. The salmon's urging its way up the
stream of fresh-water rivers is attributed to some
gratification or refreshment which, in this particu-
lar state of the fish's body, she receives from the
change of element. Now of this theory it may
be said, —

First, that of the cases which require solution,
there are few to which it can be applied with
tolerable probability; that there are none to which
it can be applied without strong objections, fur-
nished by the circumstances of the case. The
attention of the cow to its calf, and of the ewe to
its lamb, appear to be prior to their sucking. The

28*

330 NATURAL THEOLOGY.

attraction of the calf or lamb to the teat of the
dam, is not explained by simply referring it to the
sense of smell. What made the scent of milk so
agreeable to the lamb that it should follow it up
with its nose, or seek with its mouth the place
from which it proceeded ? No observation, no
experience, no argument could teach the new-
dropped animal that the substance from w^iich
the scent issued was the material of its food. It
had never tasted milk before its birth. None
of the animals which are not designed for that
nourishment ever offer to suck, or to seek out any
such food. What is the conclusion, but that the
sugescent parts of animals are fitted for their use,
and the knowledge of that use put into them?

We assert, secondly, that, even as to the cases
in which the hypothesis has the fairest claim to
consideration, it does not at all lessen the force
of the argument for intention and design. The
doctrine of instinct is that of appetencies, super-
added to the constitution of an animal, for the
effectuating of a purpose beneficial to the species.
The above-stated solution would derive these ap-
petencies from organization; but then this organi-
zation is not less specifically, not less precisely,
and, therefore, not less evidently adapted to the
same ends, than the appetencies themselves would
be upon the old hypothesis. In this way of con-
sidering the subject, sensation supplies the place
of foresight : but this is the effect of contrivance
on the part of the Creator. Let it be allowed,

NATURAL THEOLOGY. 331

for example, that the hen is induced to brood upon
her eggs by the enjoyment or rehef which, in the
heated state of her abdomen, she experiences from
the pressure of round smooth surfaces, or from
the apphcation of a temperate warmth. How
comes this extraordinary heat or itching, or call it
what you will, which you suppose to be the cause
of the bird's inclination, to be felt just at the time
when the inclination itself is wanted : when it
tallies so exactly with the internal constitution
of the egg, and with the help which that constitu-
tion requires in order to bring it to maturity ? In
my opinion, this solution, if it be accepted as to
the fact, ought to increase, rather than otherwise,
our admiration of the contrivance,'^ A gardener

'■^ Whether we regard the argument of existence, or of attri-
butes, the truth here glanced at is of extreme importance, and it
pervades the whole of Natural Theology, It will be more fully
illustrated in the Appendix, and in the notes to the subsequent
chapters. When skeptics think they have destroyed one reason
for believing in the skill or in the goodness of the Deity, by an
explanation of the means used for producing some given effect,
they only remove our admiration and our gratitude from one point
to another, and often augment both the one and the other. Sup-
pose it were discovered, contrary to all probability, that the bee
makes the angles of 109° 28' and 70*^ 32' by means of some bodily
conformation which secures this result, — some form of its own
parts answering to those angles, if such a thing can be conceived ;
the wonder is only removed from the working of the insect without
a tool to its using a tool provided for it by the intelligence which
had solved the problem of maxima and minima, whence this con-
formation is a corollary. Again, — the loss of one sense, as the
sisht, quickens our perceptions through the organs of those senses
which remain, — as touch and hearing. It is most probable that

832 NATURAL THEOLOGY.

lighting up his stoves, just when he wants to force
his fruit, and when his trees require the heat, gives
not a more certain evidence of design. So again;
when a male and female sparrow come together,
they do not meet to confer upon the expediency
of perpetuating their species. As an abstract
proposition, they care not the value of a barley-
corn whether the species be perpetuated, or not :
they follow their sensations, and all those conse-
quences ensue, which the wisest counsels could
have dictated, which the most solicito s care of fu-
turity, which the most anxious concern for the
sparrow-world, could have produced. But how
do these consequences ensue ? The sensations,

this effect is produced by the influence of habit, and has no direct
connexion with the loss sustained. But habit might have had no
such effect, and it might have blunted instead of sharpening ; its
effect tends to lessen the evil of the loss sustained , and it produces
this advantage just as much as if the compensation had been the
direct and immediate consequence of that loss. We are not here
arguing the question of evil : that will be treated of hereafter, and
it is common to both suppositions; both to the case of immediate
and of mediate compensation. Again, — suppose, in generaliz-
ing, we could resolve all intellectual phenomena into some one
principle, as association, — all moral into some other, as habit, —
all physical into some third, as gravitation; — iny, suppose the
doctrines of some materialists to prevail, and that all mental and
all physical phenomena were resolvable into the operations of some
subtile fluid, — this would surely not weaken the arguments for
the unity of the Deity, if indeed it did not rather strengthen them;
it would in no degree detract from our conviction of his skill, nor
even of the variety of its operations ; and it would leave the argu-
ment as to goodness exactly where it stood before. — See Appen-
dix, Dissertation upon Evil.

NATURAL THEOLOGY. 333

and the constitution upon which they depend, are
as manifestly directed to the purpose which we
see fulfilled by them ; and the train of intermediate
effects as manifestly laid and planned with a view
to that purpose: that is to say, design is as com-
pletely evinced by the phenomena, as it would be,
even if w^e suppose the operations to begin or to
be carried on, from what some will allow to be
alone properly called instincts, that is, from desires
directed to a future end, and having no accom-
phshment or gratification distmct from the attain-
ment of that end.

In a word : I should say to the patrons of this
opinion. Be it so ; be it that those actions of ani-
mals which w^e refer to instinct are not gone about
with any view to their consequences, but that
they are attended in the animal with a present
gratification, and are pursued for the sake of that
gratification alone ; what does all this prove, but
that the prospection, w4iich must be somewhere, is
not in the animal, but in the Creator '?

In treating of the parental aflfection in brutes,
our business lies rather with the origin of the prinr
ciple, than with the effects and expressions of it.
Writers recount these with pleasure and admira-
tion. The conduct of many kinds of animals
towards their young has escaped no observer, no
historian of nature. " How will they caress them,"
savs Derham, " with their affectionate notes ; lull
and quiet them with their tender parental voice ;
put food into their mouths; cherish and keep them

334 NATURAL THEOLOGY.

warm ; teach them to pick, and eat, and gather
food for themselves ; and, in a word, perform the
pai't of so many nurses, deputed by the Sovereign
Lord and Preserver of the world to help such
young and shiftless creatures !" Neither ought it,
under this head, to be forgotten, how much the
instinct costs the animal which feels it; how much
a bird, for example, gives up by sitting upon her
nest ; how repugnant it is to her organization, her
habits and her pleasures. An animal, formed for
liberty, submits to confinement, in the very season
when every thing invites her abroad : what is
more, an animal delighting in motion, made for
motion, all whose motions are so easy, and so free,
hardly a moment, at other times, at rest, is, for
many hours of many days together, fixed to her
nest, as close as if her limbs were tied down by
pins and wires. For my part, I never see a bird
in that situation but I recognise an invisible hand,
detaining the contented prisoner from her fields
and groves, for the purpose, as the event proves,
the most worthy of the sacrifice, the most impor-
tant, the most beneficial.

But the loss of hberty is not the whole of what
the procreant bird suflfers. Harvey tells us that
he has often found the female wasted to skin and
bone by sitting upon her eggs.

One observation more, and I will dismiss the
subject. The pcm-ing of birds, and the non-jKiir-
ing of beasts, forms a distinction between the two
classes, which shows that the conjugal instinct is

NATURAL THEOLOGY. 335

modified with a reference to utility founded on
the condition of the offspring. In quadrupeds,
the young animal draws its nutriment from the
body of the dam. The male parent neither does,
nor can contribute any part to its sustentation.
In the winged race, the young bird is supplied by
an importation of food, to procure and bring home
which, in a sufficient quantity for the demand of a
numerous brood, requires the industry of both pa-
rents. In this difference, we see a reason for the
vagrant instinct of the quadruped, and for the
faithful love of the feathered mate.

336 NATURAL THEOLOGY.

CHAPTER XIX.

OF INSECTS.

We are not writing a system of natural histo-
ry ; therefore we have not attended to the classes
into which the subjects of that science are distribu-
ted. What we had to observe concerning differ-
ent species of animals, fell easily, for the most part,
within the divisions which the course of our argu-
ment led us to adopt. There remain, however,
some remarks upon the insect tribe, which could
not properly be introduced under any other of
these heads ; and which therefore we have col-
lected into a-chapter by themselves.

The structure, and the use of the parts, of
insects, are less understood than that of quadru-
peds and birds, not only by reason of their mi-
nuteness, or the minuteness of their parts, (for that
minuteness we can, in some measure, follow w^ith
glasses,) but also by reason of the remoteness of
their manners and modes of life from those of
larger animals. For instance : Insects, under all
their varieties of form, are endowed with anten-
ncB,''^ which is the name given to those long

'''' The most scientific entomologists consider the antennae of
insects to be organs of hearing ; this is the opinion of those who
have minutely examined their structure j whereas very many en-

NATURAL THEOLOGY. 337

feelers that rise from each side of the head : but
to what common use or want of the insect kind a
provision so universal is subservient has not yet
been ascertained ; and it has not been ascer-
tained, because it admits not of a clear, or very
probable, comparison, with any organs which we
possess ourselves, or with the organs of animals
which resemble ourselves in their functions and
faculties, or with which we are better acquainted
than we are with insects. We want a ground of
analogy. This difficulty stands in our way as to
some particulars in the insect constitution, which
we might wish to be acquainted with. Neverthe-
less, there are many contrivances in the bodies of
insects, neither dubious in their use, nor obscure in
their structure, and most properly mechanical.
These form parts of our argument.

I. The elytra, or scaly wings of the genus of
scarabseus or beetle, furnish an example of this
kind. The true wing of the animal is a light,

tomologists contend that the antennae are organs of feeUng, obser-
ving that many insects are constantly touching surrounding ob-
jects with them, such as the bee tribe, ichneumonidae, &c. The
argument used against the latter opinion is, that although many
insects do undoubtedly touch surrounding objects with their an-
tennae, yet many scrupulously avoid so doing, such as the butter-
fly and moth tribe, the Lamellicorn beetles, &c. When, however,
we are asked the question, what is hearing as distinguished from
feeUng, we find it difficult to draw any line. Are they not mere
modifications of the same thing? and as the antennae of insects
are so exceedingly variable in form, may they not be used as or-
gans of touch in some, and of hearing in others ?

29

338 NATURAL THEOLOGY.

transparent membrane, finer than the finest gauze,
and not unhke it. It is also, when expanded, in
proportion to the size of the animal, very large.
In order to protect this delicate structure, and,
perhaps, also to preserve it in a due state of supple-
ness and humidity, a strong, hard case is given to
it in the shape of the horny wing which we call the
elytron. When the animal is at rest, the gauze
wings lie folded up under this impenetrable shield.
When the beetle prepares for flying, he raises the
integument, and spreads out his thin membrane to
the air. And it cannot be oJ?served without ad-
miration, what a tissue of cordage, i. e, of muscu-
lar tendons, must run in various and complicated,
but determinate directions, along this fine surlace,
in order to enable the animal, eiiher to gather it
up into a certain precise form, whenever it desires
to place its wings under the shelter which nature
hath given to them ; or to expand again their folds
when wanted for action.

In some insects the elytra cover the whole
body •,''^ in others, half; in others only a s ..all part
of it -^^ but in all,'" they completely hide and cover
the true wings. Also,

''^ From this circumstance beetles (tlie tribe of insects to which
the above description applies) have received the name of Coleop^
tera, from two Greek words si^^nifying sheath and loing.

^^ A tribe of insects called the Brachelytra (or SiOphylinus o(
Linnaeus) possess wing cases of this description.

80 These are exceptions. In the genera Motcrchvs, Silaris, (and
others might be enumerated among the beetle tribe,) the wing
uases are small and narrow, and leave the wings exposed. The

NATURAL THEOLOGY.

330

Many or most of the beetle species lodge in
holes in the earth, environed by hard, rough sub-
stances, and have frequently to squeeze their way
through narrow passages; in which situation,
wings so tender, and so large, could scarcely have
escaped injury, without both a firm covering to de-
fend them, and the capacity of collecting them-
selves up under its protection."'

II. Another contrivance, equally mechanical,
and equally clear, is the awly or borer, fixed at the

«S^sss^^sS*se*ai*ss*!«^»>

specie? of the genus Molorchus, however, do not require such pro-
tection for their wings, since they Ifj^ in flowers. The habits of
the Sitaris are not so well known; they are said to hve in the
nests of certain species of bees.

In the earwig the elytra do not entirely cover the wings ; but
the portion of the wing exposed is of horn-like substance, like th«
elytra, whilst the remaining part of the wing is extremely delicate.

8* A tribe of beetles, coming under the generic name of Hister,
forms a good illustration of this mode of existence : in these in-
sects the elytra are remarkably hard.

The species of the genus Hister possess remarkable analogical
resemblances to tortoises, which have somewhat similar habits :
like them, they are exceedingly hard, of an oval shape, and have
the power of retracting the head beneath a horny covering ; they

340 NATURAL THEOLOGY.

tails of various species of flies ; and with which
they pierce, in some cases, plants ; in others,
wood ; in others,^^ the skin and flesh of animals ;
in others, the coat of the chrysalis of insects of a
different species from their own ; and in others,
even lime, mortar, and stone /^ I need not add,
that having pierced the substance, they deposit

are slothful, and very strong, and burrow in the grovuid by means
of their fore legs.

A great analogical resemblance al^o exists between an insect
called the mole-cricket and. the mole, their habits also being
similar.

82 Almost every caterpillar (perhaps, without exception) has its
peculiar parasites among the ichneumonidse, a difterent tribe of
insects : the same ichneumon almost invariably choosing the
same caterpillar to deposit its eggs upon or in ; and as the situa-
tions in which difterent caterpillars feed are very various, so is
the structure of their parasites. The ichneumons which infest
internal feeding caterpillars (i. c, such as feed in the trunk of a
tree, or the stein of a plant) are furnished with long ovipositors to
enable them to reach the caterpillar through some hole or chink
where they themselves cannot get.

Even the ichneumons are not free from parasites. There are
instances where four or five different parasitical insects have been
found in the same chrysalis, (as that of the Trichiosoma leucorum,
a saw-fly,) each one feeding upon the other. Thus several larvce
of an ichneumon may be found feeding upon the inside of a chry^
salis ; and when these larvte turn into pupa? or chrysalides, some
of the chalcidida?, a different tribe of flics, will feed upon them,
and even some of the last may in their turn be eaten up.

*^ There is not any accredited instance of any insects perfora-
ting so hard a substance as stone, with the * awl or borer' fixed at
the tail. This instrument, technically called ovipositor, is exces*
sively variable in its structure, being scarcely alike in any two
species : the description given will answer for that of the saw-fly,
{Ter.tredo.)

NATURAL THEOLOGY. 341

their eggs in the hole. The descriptions which
naturalists give of this organ are such as the fol-
lowing: It is a sharp-pointed instrument, which,
in its inactive state, lies concealed in the extrem-
ity of the abdomen, and which the animal draws
out at pleasure, for the purpose of making a punc-
ture in the leaves, stem, or bark, of the particular
plant, which is suited to the nourishment of its
young. In a sheath, which divides and opens
whenever the organ is used, there is inclosed a
compact solid, dentated stem, along which runs a
gutter or groove, by which groove, after the pen-
etration is effected, the egg, assisted, in some cases
by a peristaltic motion, passes to its destined lodge-
ment. In the oestrum or gstd-fly, the wimble"'
draws out hke the pieces of a spy-glass : the last
piece is armed with three hooks, and is able to
bore through the hide of an ox. Can any thing
more be necessary to display the mechanism, than
to relate the fact?

ill. The stings"^ of insects, though for a differ-
ent purpose, are, in their structure, not unlike the
piercer. The sharpness to which the point in all
of them is wrought; the temper and firmness of
the substance of which it is composed ; the
strens^th of the muscles bv which it is darted out,
compared with the smallness and weakness of the
insect, and with the soft and friable texture of the
rest of the body, — are properties of the sting to be

** Whimble, or ovipositor.

" The stings of insects are also used as ovipositors.

29*

342 NATURAL THEOLOGY,

noticed, and not a little to be admired. The sting
of a hee will pierce through a goat-skin glove. It
penetrates the human flesh more readily than the
finest point of a needle. The action of the sting
aftbrds an example of the union of chemistiy and
mechanism, such as, if it be not a proof of contri-
vance, nothing is. First, as to the chemistry :
how highly concentrated must be the venom,
which, in so small a quantity, can produce such
powerful effects ! And in the bee we may observe
that this venom is made from honey, the only food
of the insect, but the last material from which I
should have expected that an exalted poison could,
by any process or digestion wiiatsoever, have been
prepared. In the next place, with respect to the
mechanism, the sting is not a simple but a com-
pound instrument. The visible sting, though
•drawn to a point exquisitely sharp, is in strictness
only a sheath, for, near to the extremity, may be
perceived by the microscope two minute orifices,
from which orifices, in the act of stinging, and, as
it should seem, after the point of the main sting
has buried itself in the flesh, are launched out two
subtile rays, which may be called the true or proper
stings, as being those through which the poison is
infused into the puncture already made by the
•exterior sting. I have said that chemistry and
mechanism are here united: by which observation
I meant, that all this machinery would have been
^iseless, telum imbelle, if a supply of poison, in-
tense in quality, in proportion to the smallness of

NATURAL THEOLOGY.

343

the drop, had not been furnished to it by the
chemical elaboration which was carried on in the
insect's body ; and that, on the other hand, the
poison, the result of this process, could not have
attained its eftect, or reached its enemy, if, when
it was collected at the extremity of the abdomen,
it had not found there a machinery fitted to con-
duct it to the external situations in which it was
to operate, viz. an awl to bore a hole, and a syr-
inge to inject the fluid. Yet these attributes,
though combined in their action, are independent
in their origin. The venom does not breed the
sting ; nor does the sting concoct the venom.

lY. The proboscis,"^ with which many insects
are endowed, comes next in order to be consider-

Fig. 1. - Fig. 2.

€d. It is a tube attached to the head of the ani-
mal ; in the bee, it is composed of two pieces, con-

^ The part called proboscis in the bee consists of a central
stalk, or tongue, a, (Fig. 1,) and four lateral pieces, or jaws, two
4)f which spring from the base, and two have their origin near the

344 NATURAL THEOLOGY.

nected by a joint : for, if it were constantly ex-
tended, it would be too much exposed to acciden-
tal injuries ; therefore, in its indolent state, it is
doubled up by means of the joint, and in that posi-
tion lies secure under a scaly penthouse.''^ In many
species of the butterfly, the proboscis, when not
in use, is coiled up like a watch-spring. In the
same bee, the proboscis serves the office of the
mouth, the insect having no other ;^^ and how much
better adapted it is, than a mouth would be, for
the collecting of the proper nourishment of the ani-
mal, is sufficiently evident. The food of the bee
is the nectar of flowers ; a drop of syrup, lodged
deep in the bottom of the corollge, in the recesses
of the petals, or down the neck of a monopetalous
glove. Into these cells the bee thrusts its long nar-
row pump, through the cavity of which it sucks"^

middle. The apical half of the stalk is soft and flexible, rather
flat, and covered with minute hairs : it is chiefly this part of the
proboscis which is used in collecting honey. Honey is not sucked
up as is generally supposed, but licked up, and then conveyed to
the oesophagus. The four lateral pieces when closed form a
sheath to protect the tongue, and other parts of the central stalk.
Fig. 2 represents the profile of a butterfly's head ; a is the com-
pound eye, and b the proboscis partiaHy unfolded ; c and d show
portions o ' the tubes forming the proboscis highly magnified.

^'' There is an indentation in the under side of the head to re-
ceive the proboscis when folded up.

** A bee has the same number of parts to its mouth as any other
insect ; the only difference between that of a bee and a beetle is,
that some of the parts are more developed in the former ; viz., th«
labium, tongue, and maxillie.

^ See Note 86. It might be more correct to say lick up, for
there is no tube.

NATURAL THEOLOGY. 345

up this precious fluid, inaccessible to every other
approach. It is observable also, that the plant is not
the worse'" for what the bee does to it. The harm-
less plunderer rifles the sweets, but leaves the
flower uninjured. The ringlets of which the pro-
boscis of the bee is composed, the muscles by which
it is extended and contracted, form so many mi-
croscopical wonders. The agility also with which
it is moved can hardly fail to excite admiration.
But it is enough for our purpose to observe, in
general, the suitableness of the structure to the
use of the means to the end, and especially the
wisdom by which nature has departed from its
most general analogy, (for animals being fur-

^ Bees are essential to the fructification of many sorts of plants,
for it is by them that the farina is carried from the male to the fe-
male flowers ; and as some flowers yield a much greater quantity
of honey than others, it might perhaps be imagined that those
yielding little, and yet depending upon the bees for their fructifi-
cation, might often be barren. No such defects, however, are to be
found : the structure of the proboscis varies considerably in diffe-
rent species of bees, so that all bees cannot collect indiscriminate-
ly from any honej'-yielding plant. One great tribe of bees (the
apidce) collect their honey for the most part from bell-shaped
flowers, such as the blind-nettle, &c. ; their long proboscis enabling
them to reach the bottom of the bells. Another tribe, having the
proboscis short, are obliged to collect from flowers of a d'.flerent
shape. There is yet another circumstance which leads the diffe-
rent sorts of bees to visit a variety of flowers : viz., that they do
not feed their larvae on the same substance. If we examine the
cells of some (the andrctiiidce,) we find that the food stored up for
the young consists of a ball of farina, which has scarcely any ad-
mixture of hone}' : these bees would naturally seek those flowers
which yield the most farina ; whereas in others (the apida) honey
with very little farina is st,ored up for the young.

346 NATURAL THEOLOGY.

nished with mouths are such,) when the purpose
could be better answered by the deviation.

In some insects the proboscis, or tongue, or
trunk, is shut up in a sharp-pointed sheath, which
sheath,^' being of a much firmer texture than the
proboscis itself, as well as sharpened at the pomt,
pierces the substance which contains the food, and
then operis within the wound, to allow the inclosed
tube, through which the juice is extracted, to per-
form its office. Can any mechanism be plainer
than this is, or surpass this ?

V. The metamorphosis of insects from grubs
into moths and flies is an astonishing process. A
hairy caterpillar is transformed into a butterfly.
Observe the change. We have four beautiful wings
where there were none before — a tubular pro-
boscis in the place of a mouth with jaws and teeth,^^

^' The mouth of the common flea {Pulex irritans) is of this na-
ture; it is (o nposed of seven pieces, a pair of mawlibles, a pair
of maxillce, two palpi or feelers, and a tongue. The uses of these
pieces appear to be as follows : — -the mandibles, which are short,
gtroncr, and sharp, are to cut through the outer skin ; the maxillce,
which are long and shaped like lancets, are to pierce still deeper
so as to cause bleeding : the tongue is then used to lick and con-
vey the blood *o the oesophagus; and the palpi are to direct these
operations, conveying information to the animal by feeling or touch.
These same seven parts (forming the mouth, and technically call-
ed trophi) are to be found in almost all insects, but constructed in
different ways to suit the various habits of the species.

"* The mouth of the cat.>rpillar, or larva state of insects, has,
in the greater portion of the species, the same number of parts a?
that of the perfect insect. In the pupa state some of th^se parts
become nearly or quite obliterated, whilst others are much more
developed to suit the habits of the animal in its next or perfect

NATURAL THEOLOGY.

347

six long legs instead of fourteen feet. In another
case we see a white, smooth, soft worm turned

state of existence ; and thus, of course, in some instances, where
there is but little difference between the habits of the larva and
those of the perfect insect, there is likewise but little difference in
the structure of the mouth, as, for instance, in locusts, grasshop-
pers, and cock.oaches.

In the butterfly tribe the maxillae or under-jaws of the caterpil-
lar become in the perfect insect elongated into two lubes (see
Cut,) which may be joined together at the pleasure of the animal,
by means of projecting ridges (furnished with a sort of hook some-
what like the laminae of feathers,) in such a way as to leave a

HUMBLE BEE.

a, a, mandibles ; c, c, maxillary palpi ;

b, b, maxillae ;

d, d, labium ;

BEE.

e, e, labial palpi;
/, tongue . g, neck,

third tube between the two. It is through the central tube that
the nectar is pumped or sucked up ; the two outer tubes Reaumur
imagines are for the reception of air ; if this be the case, it may
possibly be that air which is discharged from the central tube to
create the necessary vacuum. The mandibles, or upper jaws, and
other parts conspicuous in the caterpillar, are to be found only in
ft rudimentary state in the butterfly, — yet they do exist.

348 NATURAL THEOLOGY.

into a black, hard, crustaceous beetle with gauze
wings. These, as I said, are astonishing processes,
and must require, as it should seem, a proportiona-
bly artificial apparatus. The hypothesis which ap-
pears to me most probable is, that, in the grub,
there exist at the same time three animals, one
within another, all nourished by the same diges-
tion, and by a communicating circulation, but
in different stages of maturity.'^^ The latest dis-

^ The following observations do not exactly support the opinion
of Dr. Paley. It is more probable that the parts which are to ap-
pear in the perfect insect do not exist in the larvae, where there is
not much difference between the larva and pupa, excepting at the
time just previous to its becoming a pupa, at which time the larva
is motionless and torpid. The caterpillar of a moth, when about
to turn into a pupa, provides for the protection of the latter state,
either by surrounding itself with a web, or by some other means.
Soon after this is accomplished the caterpillar becomes motionless,
or nearly so ; it can neither eat nor crawl. At this time, and not
before, the parts of the pupa are forming within the skin of the
caterpillar, which may be easily seen by dissection. When the
difference between the larva and the perfect insect is great this is
always the case, and the pupa is passive; but when the difference
is not so considerable the case is different. The larva of a grass-
hopper scarcely differs from the perfect insect it is to become, ex-
cept in wanting wings ; the pupa differs only in having rudimen-
tary instead of perfect wings ; it casts its skin ; it is then the per-
fect insect, excepting that the wings are crippled, and these very
rapidly expand. In this latter case it is seen that there is but lit-
tle difference between the three stages, and the change from the
caterpillar to the moth is very great, and takes place only during
the torpid state of the former, which state is to allow of its taking
place, in the case of the grasshopper, where the changes are but
slio-ht, we should imagine but little of this torpidity would be re-
quired ; and such appears to be the case, for the pupae of grass-
hoppers, and allied insects, are always as active as either the larva
or perfect insect.

NATURAL THEOLOGY. 349

coveries made by naturalists seem to favour this
supposition. The insect ah-eady equipped with
wings, is descried under the membranes both of
the worm and nymph. In some species the pro-
boscis, the antennae, the limbs, and wings of the
fly have been observed to be folded up within the
body of the caterpillar, and with such nicety as to
occupy a small space only under the two first wings.
This being so, the outermost animal which, be-
sides its own proper character, serves as an in-
tegument to the other two, being the farthest ad-
vanced, dies, as w^e suppose, and drops off first.
The second, the pupa or chrysalis, then ofl?ers it-
self to observation. This also, in its turn, dies ;
its dead and brittle husk falls to pieces, and makes
way for the appearance of the fly or moth. Now
if this be the case, or indeed whatever explication
be adopted, we have a prospective contrivance of
the most curious kind; we have organizations
three deep, yet a vascular system which supplies
nutrition, growth and life to all of them together.
VI. Almost all insects are oviparous. Nature
keeps her butterflies, moths, and catterpillars lock-
ed up during the winter in their egg-state ; and
we have to admire the various devices to which, if
we may so speak, the same nature hath resorted
for the security of the egg. Many insects inclose
their eggs in a silken web; others cover them
with a coat of hair torn from their own bodies;
some glue them together; and others, like the
moth of the silk-worm, glue them to the leaves

30

350 NATURAL THEOLOGY.

upon which they are deposited, that they may not
be shaken off by the wind, or washed away by
rain. Some, again, make incisions into leaves,
and hide an egg in each incision ; whilst some
envelop their eggs with a soft substance which
forms the first aliment of the young animal ; and
some again make a hole in the earth, and, having
stored it with a quantity of proper food, deposit
their eggs in it. In all which we are to observe,
that the expedient depends not so much upon the
address of the animal, as upon the physical re-
sources of his constitution.

The art also with which the young insect is
coiled up in the egg presents, where it can be ex-
amined, a subject of great curiosity. The insect,
furnished with all the members which it ought to
have, is rolled up into a form which seems to con-
tract it into the least possible space ; by which
contraction, notw^ithstanding the smallness of the
egg, it has room enough in its apartment, and to
spare. This folding of the limbs appears to me
to indicate a special direction ; for if it were
merely the effect of compression, the collocation of
the parts would be more various than it is. In
the same species, 1 believe, it is always the same.

These observations belong to the whole insect
tribe, or to a great part of them. Other observa-
tions are limited to fewer species, but not, per-
haps, less important or satisfactory.

I. The organization in the abdomen of the silk-
worm or spider^ whereby these insects form their

NATURAL THEOLOGY. 351

thready is as incontestably mechanical as a wire-
drawer's mill. In the body of the silkworm arc

two bags, remarkable for their form, position, and
use. They wind round the intestine ; when drawn
out they are ten inches in length, though the ani-
mal itself be only two. Within these baffs is col-
lected a glue ; and, communicating with the bags,
are two paps or outlets, perforated like a grater
by a number of small holes. The glue or gum,
being passed through these minute apertures,
forms hairs of almost imperceptible fineness ; and
these hairs, when joined, compose the silk whicia
we wind oft' from the cone in which the silkworm
has wrapped itself up : in the spider, the web is
formed from this thread. In both cases, the ex*
tremity of the thread, by means of its adhesive
quality, is first attached by the animal to some
external hold ; and the end being now fastened to
a point, the insect, by turning round its body, or
by receding from that point, draws out the thread
through the holes above described, by an opera-
tion, as hath been observed, exactly similar to the
drawing of wire. The thread, like the wire, is
formed by the hole through w^hich it passes. In
one respect there is a difference. The wire is the
metal unaltered, except in figure. In the animal
process the nature of the substance is somewhat

352 NATURAL THEOLOGY.

changed as well as the form ; for, as it exists
within the insect, it is a soft, clammy gum or
glue. The thread acquires, it is probable, its
firmness and tenacity from the action of the air
upon itft surface in the moment of exposure ; and
a thread so fine is almost all surface. This pro-
perty, however, of the paste is part of the con-
trivance.
^, The mechanism itself consists of the bags or
reservoirs into which the glue is collected, and
of the external holes communicating with these
bags ; and the action of the machine is seen in the
forming of a thread, as wire is formed, by forcing
the material already prepared through holes of
proper dimensions. The secretion is an act too
subtile for our discernment, except as we perceive
it by the produce. But one thing answers to an-
other ; the secretory glands to the quality and
iconsistence required in the secreted substance ;
the bag to its reception. The outlets and orifices
are constructed not merely for relieving the re-
servoirs of their burden, but for manufacturing
the contents into a form and texture of great ex-
ternal use, or rather, indeed, of future necessity,
to the life and functions of the insect.

II. Bees, under one character or other, have
furnished every naturalist with a set of observa-
tions. I shall, in this place, confine myself to
one ; and that is the relation which obtains be-
tween the wax and the honey. No person who
has inspected a bee-hive can forbear remarking

NATURAL THEOLOGY. 353

how commodiously the honey is bestowed in the
comb, and, amongst other advantages, how effec-
tually the fermentation of the honey is prevented
by distributing it into small cells. The fact is>
that when the honey is separated from the comb,
and put into jars, it runs into fermentation with a
much less degree of heat than what takes place in
a hive. This may be reckoned a nicety ; but, in-
dependently of any nicety in the matter, I would
ask, what could the bee do with the honey if it
had not the wax ? how, at least, could it store it
up for winter? The wax, therefore, answers a
purpose with respect to the honey ; and the honey
constitutes that purpose with respect to the wax.
This is the i-elation between them. But the two
substances, though together of the greatest use,
and without each other of litt'e, come from a dif-
ferent origin. The bee finds the honey, but
makes the wax. The honey is lodged in the nec-
taria of flowers, and probably undergoes little al-
teration— is merely collected; whereas the wax
is a ductile tenacious paste, made out of a dry
powder,^* not simply by kneading it with a liquid,
but by a digestive process in the body of the bee.
What account can be rendered of facts so circum-

'^ The opinion of Huber, Hunter, and others, is, that wax is
not made out of pollen, but«f:om honey. Huber kept some bees
confined, and fed them with honey only, and wax was secreted as
usual. It is most likely that bees never cat farina, and that it is
collected from the larvae only. See article Bee, "Penny Cyclo-
paedia."

30*

554 NATURAL THEOLOGY.

Glanced, but that the animal, being intended to
feed upon honey, was, by a peculiar external con-
figuration, enabled to procure it ? That, more-
over, wanting the honey when it could not be
procured at all, it was further endued with the no
less necessary faculty of constructing repositories
for its preservation ? Which faculty, it is evident,
must depend primarily upon the capacity of pro-
viding suitable materials. Two distinct functions
go to make up the ability. First, the power in
the bee, with respect to wax, of loading the farina
of flowers upon its thighs. Microscopic observers
speak of the spoon-shaped appendages with which
the thighs of bees are beset for this very purpose;
but, inasmuch as the art and will of the bee may
be supposed to be concerned in this operation,
there is, secondly, that which doth not rest in art
or will — a digestive faculty, which converts the
loose powder into a stifle substance. This is a just
account of the honey and the honey-comb ; and
this account, through every part, carries a creative
intelligence along with it.^

9j

^'' It has often been remarked, that Dr. Paley does not either in
thia chapter, or in that on instinct, state the most remarkable of
all instincts, and of all the labours of insects, the formation -of the
cells by the bee, according to the strictest geometrical rules. The
history of this discovery made '(through Reaumur's suggestion)
by Koenig's application of the fluxional calculus, and by its result
being found to tally with Maraldi's measurement, will be given in
the Appendix. Maclaurin solved the same problem afterwards
by the help of jilaae geometry, with a truly felicitous fikill. The

NATURAL THEOLOGY. 355

The sting also of the bee has this relation to
the honey, that it is necessary for the protection
of a treasure which invites so many robbers.

III. Our business is with mechanism. In the
panorpa tribe of insects, there is a forceps in the
tail of the male insect with which he catches and
holds the female. Are a pair of pincers more me-
chanical than this provision in its structure ? or
is any structure more clear and certain in its de-
sign V^

IV. St. Pierre tells us,* that in a fly with six
feet (I do not remember that he describes the spe-
cies,) the pair next the head and the pair next the
tail have brushes at their extremities, with which
the fly dresses, as there may be occasion, the an-
terior or the posterior part of its body; but that
the middle pair have no such brushes, the situa-
tion of these legs not admitting of the brushes, if
they were there, being converted to the same use.
This is a very exact mechanical distinction.^

angles actually made differ by about two R)inutes fioiia those
given by the calculus ; but no one can doubt that subsequent dis-
covery will explain this.

^ In the genus Trichius (a tribe of beetles closely allied to the
rose beetle) the males have the tibicE of the middle pair of legs
curved for the same purpose.

^ The stag-beetle {Lucanus cervus) cleans its antennae "by
drawing them between the thigh of the fore-leg and the underside
of the thorax, in both of which parts a velvet-like patch of hair is
to be observed, which is well adapted for such purpose." See
this, and other peculiarities in the same insect, in the fest Part of
the Entomological Society's Transactions, in "The .Journal of
Proceedings," page 6.

+ Vol. i. p. 342.

356 NATURAL THEOLOGY.

V. If the reader, looking to our distributions of
science, wish to contemplate the chemistry as
well as the mechanism of nature, the insect crea-
tion will afford him an example. I refer to the
light in the tail of a glow-worm. Two points seem
to be agreed upon by naturalists concen ing it:
first, that it is phosphoric ; secondly, that its use is
to attract the male insect. The only thing to be
inquired after is the singularity, if any such there
be, in the natural history of this animal, which
should render a provision of this kind more neces-
sary for it than for other insects. That singular-
ity seems to be the difference which subsists be-
tween the male and the female, which difference
is greater than what we find in any other species
of animal whatever. The glow-worm is a female
caterpillar f the male of which is a^i/, lively, com-
paratively small, dissimilar to the female in ap-
pearance, probably also as distinguished from her
in habits, pursuits, and manners, as he is unlike in
form and external constitution. Here then is the
adversity of the case. The caterpillar cannot meet
her companion in the air. The winged rover
disdains the ground. They might never there-
fore be brought together did not this radiant
torch direct the volatile mate to his sedentary
female.^^

*« The female glow-worm undergoes the same transformations
as all other insects, and its perfect state differs considerably from
its larva or caterpillar state, though in both stages it emits the
phosphoric light. Besides the ordinary sexual distinctions, the

NATURAL THEOLOGY. 357

In this example we also see the resources of art
anticipated. One grand operation of chemistry
is the making of phosphorus ; and it was thought
an ingenious device to make phosphoric matches
supply the place of lighted tapers. Now this very
thing is done in the body of the glow-worm. The
phosphorus is not only made, but kindled, and
caused to emit a steady and genial beam, for the
purpose which is here stated, and which I believe
to be the true one.''^

VI. Nor is the last the only instance that en-
tomology affords in which our discoveries, or
rather our projects, turn out to be imitations of
nature. Some years ago, a plan was suggested
of producing propulsion by reaction in this way:
by the force of a steam-engine, a stream of water
was to be shot out of the stern of a boat, the im-
pulse of which stream upon the water in the river
was to push the boat itself forw^ard ; it is in truth

female glow-worm differs from ,the male only in being apterous ;
but apterous female insects are not unfrequent ; th.us many spe-
cies of moths have no wings. The two circumstances of the
sedentary habits of the female, and the males flying by night only,
seems to show the use of the light. See the next note.

^ There exists some controversy among naturalists as to the
use of the glow-worm's light. The doubt has been chiefly raised
by the observation that the insect is luminous, though in an im-
perfect degree, when in the state in which it cannot propa£ate, as
mentioned in the last note ; and that other insects are attracted
by light as well as the male glow-worm. The preponderance of
the argument is decidedly in favour of the supposition adopted by
our author, and which is also the commonly received opinion.
The particulars of the discussion will be given in the Appendix.

358 NATURAL THEOLOGY.

the principle by which sky-rockets ascend in the
air. Of the use or practicabihty of the plan 1 am
not speaking; nor is it my concern to praise its
ingenuity; but it is certainly a contrivance. Now,
if naturalists are to be believed, it is exactly the
device which nature has made use of for the mo-
tion of some species of aquatic insects. The larva
of the dragon-^y^ according to Adams, swims by
ejecting water from its tail — is driven forward by
the reaction of water in the pool upon the cur-
rent issuing in a direction backward from its
body.

VII. Again : Europe has lately been surprised
by the elevation of bodies in the air by means of
a balloon. The discovery consisted in finding
out a manageable substance, which was, bulk for
bulk, lighter than air ; and the application of the
discovery was to make a body composed of this
substance bear up, along with its own weight,
some heavier body which was attached to it. This
expedient, so new to us, proves to be no other
than what the Author of nature has employed in
the gossamer spider. We frequently see this spi-
der's thread floating in the air, and extended from
hedge to hedge across a road or brook of four or
five yards width. The animal which forms the
thread has no wings wherewith to fly from one
extremity to the other of this line, nor muscles to
enable it to spring or dart to so great a distance :
yet its Creator hath laid for it a path in the atmo-
sphere ; and after this manner. Though tlie ani-

NATURAL THEOLOGY.

359

mal itself be heavier than air, the thread which it
spins from its bowels is specifically lighter. This
is its balloon. The spider, left to itself, would
drop to the ground ; but being tied to its thread,
both are supported. \v . have here a very pecu-
liar provision; and to a contemplative eye it is a
gratifying spectacle to see this insect wafted on
her thread, sustained by a levity not her own, and
traversing regions which, if we examined only the
body of the animal, miglit seem to have been for-
bidden to its nature.'""

I must now crave the reader's permission to
introduce into this place, for want of a better, an
observation or two upon the tribe of animals,
whether belonging to land or water, which are
covered by shells.

/-feiix o5juersa of Mailer, — common garden snail; but the cut
represents what is called a left- handed -shell, and a rarity.

*•* It was at one time supposed that the spider could project its
iiatead through the air at will in any direction, and thus attaching

360 NATURAL THEOLOGY.

I. The shells of snails are a wonderful, a me-
chanical, and, if one might so speak concerning
the works of nature, an original contrivance.
Other animals have their proper retreats, iheir
hybernacula also, or winter-quarters, but the snail
carries these about with him. He travels with
his tent ; and this tent, though as was necessary,
both light and thin, is completely impervious
either to moisture or air. The young snail comes
out of its egg with the shell upon its back ; and
the gradual enlargement which the shell receives
is derived from the slime excreted by the animal's
skin. Now the aptness of this excretion to the
purpose, its property of hardening into a shell,
and the action, whatever it be, of the animal,
whereby it avails itself of its gift, and of the con-
stitution of its glands, (to say nothing of the work
being commenced before the animal is born,) are
things which can, with no probability, be referred
to any other cause than to express design; and
that not on the part of the animal alone, hi which
design, though it might build the house, it could
not have supplied the material. The will of the
animal could not determine the quality of the ex-
cretion. Add to which, that the shell of the

it to different bodies, move from one to the other. The observa-
tions more accurately made of late years, show that this power is
not possessed by the animal, but that it requires the aid of a cur-
rent of air to direct the thread. This correction, however, of the
former opinion, in no way weakens the force of the argument in
the text.

NATURAL THEOLOGY.

361

snail, with its pillar and convolution, is a very ar-
tificial fabric ; whilst a snail, as it should seem, is
the most numb and unprovided of all artificers.
In the midst of variety, there is likewise a regular-
ity which could hardly be expected. In the same
species of snail the number of turns is usually, if
not always, the same. The sealing up of the
mouth of the shell by the snail is also well calcu-
lated for its warmth and security ; but the cerate
is not of the same substance with the shell.

II. Much of what has been observed of snails
belongs to shell-fish and their shells, particularly
to those of the univalve kind ; with the addition

Spondylus — prickly oyster.

of two remarks — one of which is upon the great
strength and hardness of most of these shells. I
do not know whether, the weight being given, art
can produce so strong a case as are some of these
shells ; which defensive strength suits well with

31

362

NATURAL THEOLOGY.

the life of an animal that has often to sustain the
dangers of a stormy element and a rocky bottom,
as well as the attacks of voracious fish. The other
remark is upon the property, in the animal excre-

Ostrea crista galli^ of Lamarck, Mytihis crista gallioi' Linr.a'us —
the cock's-comb oyster.

tion, not only of congealing, but of congealing, or,
as a builder would call it, setting, in water, and
into a cretaceous substance, firm and hard. This
property is much more extraordinary, and, chemi-
cally speaking, more specific, than that of harden-
ing in the air, which may be reckoned a kind of
exsiccation, like the drying of clay into bricks.

Cardium cardis^a — Venus' heart cockle.

NATURAL THEOLOGY. 368

III. In the bivalve order of shell-fish, cockles,
mussels, oysters, &c., what contrivance can be so
simple or so clear as the insertion, at the back, of
a tough tendinous substance that becomes at once
the ligament which binds the two shells together,
and the hinge upon which they open and shut ?

IV. The shell of a lobster's tail, in its articula-
tions and overlappings, represents the jointed part
of a coat of mail ; or rather, which I believe to be
the truth, a coat of mail is an imitation of a lob-
ster's shell. The same end is to be answered by
both ; the same properties, therefore, are required
in both ; namely, hardness and flexibility — a co-
vering which may guard the part without ob-
structing its motion. For this double purpose the
art of man, expressly exercised upon the subject,
has not been able to devise any thing better than
what nature presents to his observation. Is not
this therefore mechanism, which the mechanic,
having a similar purpose in view, adopts ? Is the
structure of a coat of mail to be referred to art ?
Is the same structure of the lobster, conducing to
the same use, to be referred to any thing less than
art?

Some who may acknowledge the imitation, and
assent to the inference which we draw from it in
the instance before us, may be disposed, possibly,
to ask, why such imitations are not more frequent
than they are, if it be true, as we allege, that the
same principle of intelligence, design, and mecha-
nical contrivance was exerted in the formation of

364 NATURAL THEOLOGY.

natural bodies as we employ in the making of the
various instruments by which our purposes are
served ? The answers to this question are, first,
that it seldom happens that precisely the same
purpose, and no other, is pursued in any w^ork
which we compare of nature and of art ; secondly,
that it still more seldom happens that we can imi-
tate nature if we would. Our materials and our
workmanship are equally deficient. Springs and
wires, and cork and leather, produce a poor sub-
stitute for an arm or a hand. In the example
w^hich we have selected, I mean a lobster's shell
compared with a coat of mail, these difficulties
stand less in the way than in almost any other
than can be assigned ; and the consequence is, as
\\Q have seen, that art gladly borrows from nature
her contrivance, and imitates it closely.

But to return to insects. I thnik it is in this
class of animals, above all others, especially when
we take in the multitude of species which the
microscope discovers, that we are struck with
what Cicero has called "the insatiable variety of
nature." There are said to be six thousand spe-
cies of flies ; seven hundred and sixty butterflies ;
each different from all the rest (St. Pierre.)""

"^' There are collections of insects in this country which, in all
probability, contain forty thousand species. The number of spe-
cies in existence may fairly be reckoned at sixty or eighty thou-
sand. Mr. Stephens, in his catalogue of British insects, enume-

NATURAL THEOLOGY. 365

The same writer tells us, from his own observa-
tion, that thirty-seven species of winged insects,
with distinctions well expressed, visited a single
strawberry-plant in the course of three weeks.*
Ray observed, within the compass of a mile or
two of his own house, two hundred kinds of but-
terflies,'"" nocturnal and diurnal. He likewise as-
serts, but, I think, without any grounds of exact
computation, that the number of species of insects,
reckoning all sorts of them, may not be short of
ten thousand. f And in this vast variety of animal
forms, (for the observation is not confined to in-
sects, though more applicable perhaps to them
than to any other class,) we are sometimes led to
take notice of the different methods, or rather of
the studiously diversified methods, by which one
and the same purpose is attained. In the article
of breathing, for example, which was to be pro-
vided for in some way or other, besides the ordi-
nary varieties of lungs, gills, and breathing-holes,
(for insects in general respire, not by the mouth,
but through holes in the sides,) the nymphae of

rates ten thousand, since the pubheation of which, many new spe-
cies have been discovered. We are now speaking of true in-
sects,— animals having six legs, &c., — and not including crabs,
spiders, scorpions, and others, which have been classed with in-
sects.

'0* Ray must mean butterflies and moths, -rr^ we have not one
hundred species of butterflies in this country; and besides, no
butterflies are "nocturnal."

* Vol, i. p. 3. t Wisd. of God, p. 23,

31*

366 NATURAL THEOLOGY.

gnats have an apparatus to raise their hacks to the
top of the water, and so take breath. The hydro-
canthari do the hke by thrusting their tails out of
the water.* The maggot of the eruca labra has
a long tail, one part sheathed within another, (but
which it can draw out at pleasure,) wdth a starry
tuft at the end, by which tuft, when expanded
upon the surface, the insect both supports itself in
the ^vater, and draws in the air which is neces-
sary. In the article of natural clothing, we have
the skins of animals invested with scales, hair, fea-
thers, mucus, froth, or itself turned into a sliell or
crust. In the no less necessary article of offence
and defence, we have teeth, talons, beaks, horns,
stings, prickles, with (the most singular expedient
for the same purpose) the power of giving the
electric shock, and, as is credibly related of some
animals, of driving away their pursuers by an in-
tolerable foetor, or of blackening the water through
which they are pursued. The consideration of
these appearances might induce us to believe that
iia.riety itself, distinct from every other reason,
was a motive in the mind of the Creator, or with
the agents of his will.

To this great variety in organized life the Deity
has given, or perhaps there arises out of it, a cor-
responding variety of animal appetites. For the
final cause of this we have not far to seek. Did
all animals covet the same element, retreat, or

* Derham, p. 7.

NATURAL THEOLOGY. 367

food, it is evident how much fewer could be sup-
plied and accommodated than what at present
live conveniently together, and find a plentiful
subsistence. What one nature rejects, another
delights in. Food which is nauseous to one tribe
of animals becomes, by that very property which
makes it nauseous, an alluring dainty to another
tribe. Carrion is a treat to dogs, ravens, vultures,
fish.'"^ The exhalations of corrupted substances
attract flies by crowds. Maggots revel in putre-
faction.'''^

103 Very many insects subsist entirely upon carrion, both in the
larva and imago state, and in hot weather must be highly service-
able in removing such noxious substances. In this point of view
the maggots of flies are exceedingly useful; a carcass becoming
speedily threaded in every direction by them, is soon either de-
voured or wasted.

1°'* The most remarkable circumstance relative to instinct, as
well as to the habits of insects, the architecture of the bee, has
been observed upon in a former note. The manufacture of the
wasp perhaps comes next, and is to the chemistry what the for-
mer is to the mathematics of instinct. It furnishes, too, one of the
most striking instances of the discoveries of man having been an-
ticipated by the lower animals ; and is another remarkable proof
how many more might have been made by closely attending to
their habits, — perhaps a more remarkable proof than those re-
ferred to in the text of this chapter, and hinted at in chapter viii.,
"where the author is treating of the vertebrae and ribs. It is cer-
tain that some of the most material improvements in paper-making
recently introduced, as the use of other substances besides rags,
xmd the obtaining toughness by means of long fibres, had been
known to the wasp from its first creation. Its whole process in
making what is called wasp-paper is precisely that of the best pa-
per-makers. This will be illustrated in the Appendix. It is only
mentioned here as another among the striking instances of the

368 NATURAL THEOLOGY.

Divine agency through the operations of unreasoning animals —
instances which fill the contemplative mind w ith the most pro-
found and pleasing admiration, and dispose it to the enjoyment
and the duty of heartfelt devotion.

The migration of birds is another subject full of instruction re-
garding the great queslions connected with instinct, and is re-
served for the Appendix. Observation seems at variance with
the notion of the older birds teaching the yearlings ; indeed, the
two classes have been found not to travel together. But the agi-
tation universally observed in birds of passage kept in cages, at
the season of migration, proves clearly that no experience nor in-
struction will account for the change of place. See Mr. W. Her-
bert's excellent remarks on this instinct, and on the similar instincts
respecting choice of food, which makes birds bred in a cage at
once select their appointed food when shown them for the first
time. White's Selbourne, edit. 1833, p. 41, et seq. The facts
respecting carrier-pigeons and other animals finding their way-
through countries, in the knowledge of which they never could
have been trained, belong to the same class, and will be particu-
larly discussed in the Appendix — Dissertation upon Instinct.

The doctrine of conflicting instincts will be considered under
the head of conflicting contrivances in the Dissertations upon Evil,
and adverted to in the Notes on the last Chapter. Such apparent
conflicts afford no ground whatever for the skeptical argument as
to design ; and they in no way strengthen the skeptical argument
drawn, and inaccurately drawn, from other sources, respecting
benevolence.

NATURAL THEOLOGY. 309

CHAPTER XX.

OF PLANTS.

I THINK a designed and studied mechanism to be
in general more evident in animals than in plants ;
and it is unnecessary to dwell upon a weaker ar-
gument where a stronger is at hand. There are,
however, a few observations upon the vegetable
kingdom which lie so directly in our way, that it
would be improper to pass by them without notice.

The one great intention of nature in the struc-
ture of plants seems to be the perfecting of the
seed, and, what is part of the same intention, the
preserving of it until it be perfected. This inten-
tion shows itself, in the first place, by the care
which appears to be taken to protect and ripen,
by every advantage w4iich can be given to them
of situation in the plant, those parts which most
immediately contribute to fructification, viz., tlie
antherse, the stamina, and the stigmata. These
parts are usually lodged in the centre, the recesses,
or the labyrinths of the flow^er — during their ten-
der and immature state are shut up in the stalk,
or sheltered in the bud — as soon as they have ac-
quired firmness of texture sufficient to bear ex-
posure, and are ready to perform the important
office which is assigned to them, they are disclosed

370 NATURAL THEOLOGY.

to the light and air by the bursting of the stem or
the expansion of the petals; after which they have,
in many cases, by the very form of the flower du-
ring its blow, the light and warmth reflected upon
them from the concave side of the cup. What is
called also the sleep of plants is the leaves or petals
disposing themselves in such a manner as to shel-
ter the young stems, buds, or fruit. Tiiey turn up,
or they fall down, according as this purpose ren-
ders either change of position requisite. In the
growth of corn, whenever the plant begins to shoot,
the two upper leaves of the stalk join together,
embrace the ear, and protect it till the pulp has ac-
quired a certain degree of consistency. In some
water-plants the flowering and fecundation are
carried on within the stem, which afterwards
opens to let loose the impregnated seed.* The
pea, or papilionaceous tribe, inclose the parts of
fructification within a beautiful folding of the inter-
nal blossom, sometimes called, from its shape, the
boat or keel — itself also protected under a pent-
house formed by the external petals. This struc-
ture is very artificial ; and what adds to the value
of it, though it may diminish the curiosity, very
general. It has also this further advantage, (and
it is an advantage strictly mechanical,) that all the
blossoms turn their hacks to the wind whenever
the gale blows strong enough to endanger the deli-
cate parts upon which the seed depends. I have
observed this a hundred times in a field of peas in

♦Philos. Transact, part ii. 1796, p. 502.

NATURAL THEOLOGY.

371

blossom. It is an aptitude which results from the
figure of the flow er, and, as we have said, is strict-
ly mechanical, as much so as the turning of a wea-
ther-board or tin cap upon the top of a chimney. Of
the poppy, and of many similar species of flowers,
the head while it is growing hangs down, a rigid
curvature in the upper pait of the stem giving to

Papaver rhc^as — Poj'py.

it that position ; and in that position it is impene-
trable by rain or moisture. When the head has
acquired its size and is ready to open, the stalk
erects itself for the purpose, as it should seem, of
presenting the flower, and with the flower the in-
struments of fructification, to the genial influence
of the sun's rays. This always struck me as a
curious property, and specifically as well as origi-
nally provided for in the constitution of the plant;
for if the stem be only bent by the weight of the
head, how comes it to straighten itself when the
head is the heaviest ? These instances show the

872 NATURAL THEOLOGY.

attention of nature to this principal object, the
safety and maturation of the parts upon which the
seed depends.

In trees^ especially in those which are natives
of colder climates, this point is taken up earlier.
Many of these trees (observe in particular the ash
and the horse-chestnut) produce the embryos of
the leaves and flowers in one year, and bring them
to perfection the following. There is a winter
therefore to be gotten over. Now what we are
to remark is, how nature has prepared for the
trials and severities of that season. These tender
embrj'os are, in the first place, wrapped up with
a compactness which no art can imitate ; in which
state they compose what we call the bud. This
is not all. The bud itself is inclosed in scales ;
w hich scales are formed from the remains of past
leaves, and the rudiments of future ones.'°^ Neither
is this the whole. In the coldest climates, a third
preservative is added, by the bud having a coat of
gum or resin, which, being congealed, resists the

J05 1 his is not exr\ctly true. Buds are not inclosed in scales
formed from the remains of past leaves, except in a few rare in-
stances, to which it cannot be supposed that the author refers ;
neither are they protected by what can correctly be called the ru-
diments of future leaves, or are only protected in part. The ex-
tensive seales of a bud, those in which the office of protection
more especially resides, are rudimentary leaves, which are form-
ed at the end of the season, when ihe force of development in
the vet^etable system is weak and imperfect ; they do not be-
come leaves another season, but are simply thrown off by the ex-
pansion of the leaves which unfold from within them.

NATURAL THEOLOGY. 373

Strongest frosts. On the approach of \v arm wea-
ther, this gum is softened, and ceases to be a hin-
derance to the expansion of the leaves and flowers.
All this care is part of that system of provisions
which has for its object and consummation the
production and perfecting of the seeds.

The SEEDS themselves are packed up in a cap-
sule, a vessel composed of coats, which, compared
with the rest of the flower, are strong and tough.
From this vessel projects a tube, through which
tube the farina, or some subtile fecundating efflu-
vium that issues from it, is admitted to the seed.
And here also occurs a mechanical variety, ac-
commodated to the different circumstances under
which the same purpose is to be accomplished. In
flowers which are erect, the pistil is shorter than
the stamina ; and the pollen, shed from the antherae
into the cup of the flower, is caught in its descent by
the head of the pistil, called the stigma. But how
is this managed when the flowers hang down, (as
does the crown-imperial for instance,) and in
which position, the farina, in its fall, would be car-
ried from the stigma, and not towards it ? The
relative length of the parts is now inverted. The
pistil in these flowers is usually longer, instead of
shorter, than the stamina, that its protruding sum-
mit may receive the pollen as it drops to the ground.
In some cases, (as in the nigella,) where the shafts
of the pistils or stiles are disproportionably long
they bend down their extremities upon the antherae,
that the necessary approximation may be effected.

32

374 NATURAL THEOLOGY.

But (to pursue this great work in its progress)
the impregnation, to which all this machinery re-
lates, being completed, the other parts of the
flower fade and drop off*, whilst the gravid seed-
vessel, on the contrary, proceeds to increase its
bulk, always to a great, and, in some species (in the
gourd, for example, and melon,) to a surprising
comparative size ; assuming in different plants an
incalculable variety of forms, but all evidently con-
ducing to the security of the seed. By virtue of
this process, so necessary, but so diversified, we
have the seed at length, in stone-fruits and nuts,
incased in a strong shell, the shell itself inclosed
in a pulp or husk, by which the seed within is, or
hath been, fed ; or, more generally (as in grapes,
oranges, and the numerous kinds of berries)
plunged overhead in a glutinous syrup, contained
within a skin or bladder: at other times (as in ap-
ples and pears) embedded in the heart of a firm
fleshy substance ; or (as in strawberries) pricked
into the surface of a soft pulp.

These and many more varieties exist in what
we cdiW fruits.* In pulse, and grain, and grasses;

+ From the conformation of fruits alone, one might be led, even
without experience, to suppose, that part of this provision was
destined for the utihties of animals. As hmited to the plant, the
provision itself seems to go beyond its object. The flesh of an
apple, the pulp of an orange, the meat of a plum, the fatness of
the olive, appear to be more than sufficient for the nourishing of
the seed or kernel. The event shows that this redundancy, if it
be one, ministers to the support and gratification of animal na-
tures ; and when we observe a provision to be more than suffi-

\

NATURAL THEOLOGY. 375

in trees, and shrubs, and flowers; the variety of
the seed-vessels is incomputable. We have the
seeds (as in the pea tribe) regularly disposed in
parchment pods, w^hich, though soft and mem-
branous, completely exclude the wet even in the
heaviest rains ; the pod also, not seldom (as in
the bean) lined with a fine down; at other times
(as in the senna) distended like a blown bladder :
or we have the seed enveloped in wool (as in the
cotton-plant) lodged (as in pines) between the

cient for one purpose, yet wanted for another purpose, it is not
unfair to concludL^ that both purposes were contemplated together.
It favours this view of the subject to remark, that fruits are not
(which they might have been) ready aUtogether, but that they
ripen in succession throughout a great part of the year ; some in
summer; some in autumn; that some require the slow matura-
tion of the winter, and supply the spring ; also that the coldest
fruits grow in the hottest places. Cucumbers, pine-apples, melons,
are the natural produce of warm climates, and contribute greatly,
by their coolness, to the refreshment of the inhabitants of those
countries.

I will add to this note the following observation communicated
to me by INIr. Brinkley.

"The eatable part of the cherry or peach first serves the pur-
poses of perfecting the seed or kernel, by means of vessels pass-
ing through the stone, and which are very visible in a peach-
stone. After the kernel is perfected, the stone becomes hard,
and the vessels cease their functions. But the substance surround-
ing the stone is not then thrown away as useless. That which
was before only an instrument for perfecting the kernel, now re-
ceives and retains to itself the whole of the sun's influence, and
thereby becomes a grateful food to man. Also what an evident
mark of design is the stone protecting the kernel ! The inter-
vention of the stone prevents the second use from interfering with
the first. — .A/ofe of the Author.

376 NATURAL THEOLOGY.

hard and compact scales of a cone, or barricadoed
(as in the artichoke and thistle) with spikes and
prickles ; in mushrooms, placed under a pent-
house ; in ferns, within slits in the back part of
the leaf: or (which is the most general organiza-
tion of all) we find them covered by strong, close
tunicles, and attached to the stem according to an
order appropriated to each plant, as is seen in the
several kinds of grains and of grasses.

In which enumeration, what we have first to
notice is, unity of purpose under variety of expe-
dients. Nothing can be more single than the de-
sign ; more diversified than the means. Pellicles,
shells, pulps, pods, husks, skin, scales armed with
thorns, are all employed in prosecuting the same
intention. Secondly ; we may observe, that, in
all these cases, the purpose is fulfilled within a
just and limited degree. We can perceive, that
if the seeds of plants were more strongly guarded
than they are, their greater security would inter-
fere with other uses. Many species of animals
would suffer, and many perish, if they could not
obtain access to them. The plant would overrun
the soil ; or the seed be w^asted for want of room
to sow itself. It is sometimes as necessary to de-
stroy particular species of plants, as it is, at other
times, to encourage their growth. Here, as in
many cases, a balance is to be maintained between
opposite uses. The provisions for the preserva-
tion of seeds appear to be directed chiefly against
the inconstancy of the elements, or the sweeping

NATURAL THEOLOGY. 377

destruction of inclement seasons. The depreda-
tion of animals, and the injuries of accidental vio-
lence, are allowed for in the abundance of the in-
crease. The result is, that out of the many thou-
sand different plants which cover the earth, not a
single species, perhaps, has been lost since the
creation.

When nature has perfected her seeds, hei* next
care is to disperse them. The seed cannot an-
swer its purpose, while it remains confined in the
capsule. After the seeds therefore are ripened,
the pericarpium opens to let th^m out ; and the
opening is not like an accidental bursting, but,
for the most part, is according to a certain rule in
each plant. What I have always thought very
extraordinary, nuts and shells, which we can hard-
ly crack with our teeth, divide and make way for
the little tender sprout which proceeds from the
kernel. Handling the nut, I could hardly con-
ceive how the plantule was ever to get out of it.
There are cases, it is said, in which the seed-ves-
sel, by an elastic jerk, at the moment of its explo-
sion, casts the seeds to a distance. We all how
ever know, that many seeds (those of most compo-
site flowers, as of the thistle, dandelion, &c.) are
endowed with what are not improperly called
wings; that is, downy appendages, by which they
are enabled to float in the air, and are carried
oftentimes by the wind to great distances from
the plant which produces them. It is the swell-
ing also of this downy tuft within the seed-vessel

32*

378 NATURAL THEOLOGY.

that seems to overcome the resistance of its coats,
and to open a passage for the seed to escape.

But the constitution of seeds is still more admi-
rable than either their preservation or their disper-
sion. In the body of the seed of every species of
plant, or nearly of every one, provision is made
for two grand purposes : first, for the safety of the
germ ; secondly, for the temporary support of the
future plant. The sprout, as folded up in the
seed, is delicate and brittle beyond any other sub-
stance. It cannot be touched w^ithout being bro-
ken. Yet, in beans, peas, grass-seeds, grain, fruits,
it is so fenced on all sides, so shut up and protect-
ed, that, whilst the seed itself is rudely handled,
tossed into sacks, shovelled into heaps, the sacred
particle, the miniature plant, remains unhurt. It
is wonderful how long many kinds of seeds, by the
help of their integuments, and perhaps of their
oils, stand out against decay. A grain of mus-
tard-seed has been known to lie in the earth for a
hundred years; and, as soon as it has acquired a
favourable situation, to shoot as vigorously as if
just gathered from the plant. Then, as to the
second point, the temporary support of the future
plant, the matter stands thus. In grain, and pulse,
and kernels, and pippins, the germ composes a
very small part of the seed. The rest consists of
a nutritious substance, from which the sprout
draws its aliment for some considerable time after
it is put forth ; viz., until the fibres, shot out from
the other end of the seed, are able to imbibe

NATURAL THEOLOGY. 379

juices from the earth, in a sufficient quantity for its
demand. It is owing to this constitution, that we
see seeds sprout, and the sprouts make a con-
siderable progress, without any earth at all. It is
an economy, also, in which we remark a close
analogy between the seeds of plants and the eggs
of animals. The same point is provided for, in
the same manner in both. In the egg, the resi-
dence of the living principle, the cicatrix, forms a
very minute part of the contents. The white and
the white only is expended in the formation of the
chicken. The yolk, very little altered or dimin-
ished, is wrapped up in the abdomen of the young
bird, when it quits the shell ; and serves for its
nourishment, till it have learned to pick its own
food. This perfectly resembles the first nutrition
of a plant. In the plant, as well as in the animal^
the structure has every character of contrivance
belonging to it ; in both it breaks the transition
from prepared to unprepared aliment ; in both, it
is prospective and compensatory. In animals
which suck, this intermediate nourishment is sup-
plied by a different source.

In all subjects, the most common observations
are the best, when it is their truth and strength
which have made them common. There are, of
this sort, two concerning plants, which it falls
within our plan to notice. The first relates to
what has already been touched upon, their ger-
mination. When a grain of corn is cast into the

380 NATURAL THEOLOGY.

ground, this is the change which takes place.
From one end of the grain issues a green sprout ;
from the other, a number of white fibrous threads.
How can this be explained? Why not sprouts
from both ends? why not fibrous threads from
both ends ? To what is the difference to be refer-
red, but to design ; to the different uses which
the parts are therefore to serve ; uses which
discover themselves in the sequel of the process ?
The sprout, or plumule, strugges into the air ; and
becomes the plant, of which, from the first, it con-
tained the rudiments : the fibres shoot into the
earth ; and thereby both fix the plant to the
ground, and collect nourishment from the soil for
its support. Now, what is not a little remarkable,
the parts issuing from the seed take their respec-
tive directions, into whatever position the seed it-
self happens to be cast. If the seed be thrown
into the wrongest possible position ; that is, if the
ends point in the ground the reverse of what they
ought to do, every thing, nevertheless, goes on
right. The sprout, after being pushed down a
little way, makes a bend, and turns upwards ; the
fibres, on the contrary, after shooting at first up-
wards, turn down. Of this extraordinary vege-
table fact, an account has lately been attempted
to be given. "The plumule (it is said) is stimula-
ted by the air into action, and elongates itself
when it is thus most excited ; the radicle is stim-
ulated by moisture, and elongates itself when it
is thus most excited. Whence one of these grows

NATURAL THEOLOGY. 381

upward in quest of its adapted object, and the
other downward."* Were this account better
verified by experiment than it is, it only shifts the
contrivance. It does not disprove the contri-
vance ; it only removes it a little further back.
Who, to use our author's own language, ''adapted
the objects ?" Who gave such a quality to these
connate parts, as to be susceptible of different
"stimulation;" as to be "excited" each only by
its own element, and precisely by that which the
success of the vegetation requires ? I say, " which
the success of the vegetation requires ;" for the
toil of the husbandman w^ould have been in vain,
his laborious and expensive preparation of the
ground in vain; if the event must, after all, depend
upon the position in which the scattered seed was
sown. Not one seed out of a hundred would fall
in a right direction.

Our second observation is upon a general pro-
perty of climbing plants, which is strictly mecha-
nical. In these plants, from each knot or joint, or
as botanists call it, axilla, of the plant, issue, close
to each other, two shoots, one bearing the flower
and fruit, the other drawn out into a wire, a long,
tapering, spiral tendril, that twists itself round any
thing which lies within its reach. Considering
that in this class two purposes are to be provided
for, (and together) fructification and support, the
fruitage of the plant and the sustentation of the

* Darwin's Phytologia, p. 144,

382 NATURAL THEOLOGY.

stalk, what means could be used more effectual,
or, as I have said, more mechanical, than what this
structure presents to our eyes ? Why, or how,
without a view to this double purpose, do two
shoots, of such different and appropriate forms,
spring from the same joint, from contiguous points
of the same stalk ? It never happens thus in robust
plants, or in trees. "We see not," says Ray, "so
much as one tree, or shrub, or herb, that hath a
firm and strong stem, and that is able to mount up
and stand alone without assistSLVice, funiished with
these tendrils. ^^ ISIake only so simple a compa-
rison as that between a pea and a bean. Why
does the pea put forth tendrils, the bean not? but
because the stalk of the pea cannot support itself,
the stalk of the bean can. We may add also, as
a circumstance not to be overlooked, that, in the
pea tribe, these clasps do not make their appear-
ance till they are wanted — till the plant has
grown to a height to stand in need of support.

This word "support" suggests to us a reflection
upon a property of grasses, of corn, and canes.
The hollow stems of these classes of plants are set
at certain intervals with joints. These joints are
not found in the trunks of trees, or in the solid
stalks of plants. There may be other uses of these
joints ; but the fact is, and it appears to be at least
one purpose designed by them, that they corrobo-
rate the stem, which by its length and hollo wness
would otherwise be too liable to break or bend.

Grasses are Nature's care. With these she

NATURAL THJKOLOGY. 383

clothes the earth — with these she sustains its in-
habitants. Cattle feed upon their leaves — birds
upon their smaller seeds — men upon the larger;
for few readers need be told that the plants which
produce our bread-corn belong to this class. In
those tribes which are more generally considered
as grasses, their extraordinary means and powers
of preservation and increase, their hardiness, their
almost unconquerable disposition to spread, their
faculties of reviviscence, coincide with the inten-
tion of Nature concerning them. They thrive
under a treatment by which other plants are de-
stroyed. The more their leaves are consumed,
the more their roots increase. The more thev
are trampled upon, the thicker they grow. Many
of the seemingly dry and dead leaves of grasses
revive, and renew their verdure in the spring.'*^^
In lofty mountains, where the summer heats are
not sufficient to ripen the seeds, grasses abound
which are viviparous, and consequently able to
propagate themselves without seed. It is an ob-
servation likewise which has often been made,
that herbivorous animals attach themselves to the
leaves of grasses, and if at liberty in their pastures
to range and choose, leave untouched the straws
which support the flowers.*

J<^ Here, to be correct, we ahould read " Many grasses whose
leaves are so dry and withered that the plants appear dead, revive
and renew their existence in the spring by pusliino- forth new
leaves from the bosom of the former ones."

+ Withering, Bot. Arr. vol. i. p. 28, ed. 2nd.

384 NATURAL THEOLOGY.

The GENERAL properties of vegetable nature, or
properties common to large portions of that king-
dom, are almost all which the compass of our ar-
gument allows us to bring forward. It is impossi-
ble to follow plants into their several species. We
may be allowed, however, to single out three or
four of these species as worthy of a particular no-
tice, either by some singular mechanism, or by
some peculiar provision, or by both.

I. Jn Dr. Darwin's Botanic Garden, (1. 395,
note,) is the following account of the vallisneria,
as it has been observed in the river Rhone : —
" They have roots at the bottom of the Rhone.
The flowers of the female plant float on the sur-
face of the water, and are furnished with an clas-
tic spiral stoch, which extends or contracts as the
water rises or falls — this rise or fall, from the
torrents which flow into the river, often amount-
ing to many feet in a few hours. The flowers of
the male plant are produced under water ; and as
soon as the fecundating farina is mature, they se-
parate themselves from the plant, rise to the sur-
face, and are wafted by the air, or borne by the
currents, to the female flowers." Our attention
in this narrative will be directed to two particu-
lars : first, to the mechanism, the " elastic spiral
stalk," which lengthens or contracts itself accord-
ing as the water rises or falls ; secondly, to the
provision which is made for bringing the male
flower, which is produced under water, to the fe-
male flower, which floats upon the surface.

NATURAL THEOLOGY. 385

II. My second example I take from Withering's
Arrangement, vol. ii. 209, ed. 3. " The cuscuta
europcBa is a parasitical plant. The seed opens,

and puts forth a little spiral body, which does not
seek the earth to take root, but climbs in a spiral
direction, from right to left, up other plants, from
which, by means of vessels, it draws its nourish-
ment." The " little spiral body " proceeding from
the seed is to be compared with the fibres which
seeds send out in ordinary cases ; and the compa-
rison ought to regard both the form of the threads
and the direction. They are straight; this is
spiral. They shoot downwards ; this points up-
wards. In the rule and in the exception we
equally perceive design.'**'

^o' This statement is incorrect. When the seed of the cuscuta
opens, it puts forth a httle thread-shaped body, namely, a young
root, which, as in other plants, plunges into the earth, and from
t he opposite end elevates a young and slender stem. The latter

33

386 NATURAL THEOLOGY.

IIL A better known parasitical plant is the
evergreen shrub, called the misseltoe. What we
have to remark in it is a singular instance oi com-
pensation. No art hath yet made these plants
take root in the earth. Here, therefore, might
seem to be a mortal defect in their constitution.
Let us examine how this defect is made up to
them. The seeds are endued with an adhesive
quality so tenacious, that, if they be rubbed upon
the smooth bark of almost any tree, they will stick
to it. And then what follows ? Roots, 'springing
from these seeds, insinuate their fibres into the
woody substance of the tree ; and the event is,
that a misseltoe plant is produced next winter.*

after a little while, applies itself to some neighbouring plant, and
emits very short broad suckers on the side of its stem, which is
placed in contact with the other plant ; by these suckers it fastens
itself upon the new branch, round which it twines, and as soon as
it IS secure in its new station its root perishes, and it ceases to
have any communication with the earth. This property in the
cuscula seems to be given it in consequence of its root not having
the power that such parts usually possess of branching, lengthen-
ing, and attracting nutriment from the earth. If the cuscuta seed
germinates at a distance from any living branch to which it can
adhere, it elevates its stem for a short time in the air and then dies.
If it is so placed as to be able to come in contact only with dead
branches, still it dies ; and it is only when it succeeds in fixing it-
self upon a living branch that it emits its suckers and continues to
exist. Once attached to the living stem of another plant, it takes
that for its base, and turning round once or twice, then darts forth
in a straight line, touches something else which it also fixes in its
folds, and thus travels from plant to plant, sometimes covering a
Tcry considerable extent of bushes.

* Withering, Bot. Arr. vol. i. p. 203, ed. 2d.

NATURAL THEOLOGY.

387

Of no other plant do the roots refuse to shoot in
the ground ; of no other plant do the seeds pos-
sess this adhesive, generative quality, when ap-
plied to the bark of trees.'"^

IV. Another instance of the compensatory sys-
tem is in the autumnal crocus, or meadow saffron,
{colchicum autumnale.) I have pitied this poor
plant a thousand times. Its blossom rises out of
the ground in the most forlorn condition possible ;
without a sheath, a fence, a calyx, or even a leaf
to protect it : and that, not in the spring, to be
visited by summer suns, but under all the disad-
vantages of the declining year. When we come,

however, to look more closely into the struct ure
of this plant, we find that, instead of its being ne-

^°^ These statements are true, not only of the misseltoe or v is-
cum actum, but of the whole natural order Loranlhacct, with one
exception.

388 NATURAL THEOLOGY.

glected, Natui'e has gone out of her course to pro-
vide for its security, and to make up to it for all
its defects. The seed-vessel, vs^hich in other plants
is situated within the cup of the flower, or just be-
neath it, in this plant lies buried ten or twelve in-
ches under ground within the bulbous root. The
tube of the flower, which is seldom more than a
few tenths of an inch long, in this plant extends
down to the root. The styles in all cases reach
the seed-vessel ; but it is in this by an elongation
unknown to any other plant. All these singulari-
ties contribute to one end. " As this plant blos-
soms late in the year, and probably would not
have time to ripen its seeds before the access of
winter, which would destroy them, Providence
has contrived its structure such, that this import-
ant ofliice may be performed at a depth in the
earth out of reach of the usual effects of frost."*
That is to say, in the autumn nothing is done
above ground but the business of impregnation :
which is an aflfair between the antherae and the
stigmata, and is probably soon over. The matu-
ration of the impregnated seed, which in other
plants proceeds within a capsule, exposed together
with the rest of the flower to the open air, is here
carried on, and during the whole winter, within
the heart, as we may say, of the earth, that is,
"out of the reach of the usual eftects of frost."
But then a new difficulty presents itself. Seeds,
though perfected, are known not to vegetate at

* Withering, ubi supra, p. 360.

NATURAL THEOLOGY. 389

this depth in the earth. Our seeds, therefore,
though so safely lodged, would, after all, be lost
to the purpose for which all seeds are intended.
Lest this should be the case, " a second admirable
provision is made to raise them above the surface
when they are perfected, and to sow them at a
proper distance :" viz., the germ grows up in the
sj^ring, upon a fruit-stalk, accompanied w ith leaves.
The seeds now, in common with those of other
plants, have the benefit of the summer, and are
sown upon the surface. The order of vegetation
externally is this ; — the plant produces its flowers
in September ; its leaves and fruits in the spring
following.

V. I give the account of the dioncea muscipula,
an extraordinary American plant, as some late
authors have related it : but whether we be yet
enough acquainted with the plant, to bring every
part of this account to the test of repeated and
familiar observation, I am unable to say. " Its
leaves are jointed, and furnished with two rows
of strong prickles ; their surfaces covered with a
number of minute glands, which secrete a sweet
liquor that allures the approach of flies. When
these parts are touched by the legs of flies, the
two lobes of the leaf instantly spring up, the rows
of prickles lock themselves fast together, and
squeeze the unwary animal to death."* Here,
under a new model, we recognise the ancient

♦ Smellie's Phil, of Nat. Hist. vol. i. p. 5.

390

NATURAL THEOLOGY.

plan of nature, viz., the relation of parts and pro-
visions to one another, to a common office, and to
the utility of the organized body to which they
belong. The attracting syrup,'"^ the rows of strong
prickles, their position so as to interlock the joints
of the leaves ; and, what is more than the rest,
that singular irritabihty of their surfaces, by which
they close at a touch ; all bear a contributory part
in producing an effect, connected either with the
defence or with the nutrition of the plant."**

109 From this account must be omitted what is said of the syrup
that allures the approach of flies. There is no such attraction
upon the leaves of the dionoea.

''° The pitcher- plant, nepenthes distillatoria, of the East, is another

NATURAL THEOLOGY. 391

example which may be given. It grows natural pitchers or tank-
ards, holding from a pint to a quart of pure water. Even when
raised in this country under glass, they have been known to hold
half-a-pint. The plate represents these, with their lids AA, which
move on hinges, opening in moist weather, and shutting quite
close in dry to prevent evaporation. When the pitcher becomes
full, and requires additional support, the hook A behind the lid
seizes on some neighbouring tendril, and holds by it. BB are
young pitchers just unfolding. This water which supplies the
pitcher is secreted by the process of vegetation, and is perfectly
pure, though the plant grows in a muddy and unwholesome marsh.

The palo de vaca, or cow-tree of South America, yields a deli-
cious and nutritive milk on its trunk being pierced ; and it grows
in the most parched soil, and in a climate where rain is unknown
during half the year.

The supply of fine water afforded by the tillandsia, or water-
with, in Jamaica, and by the bejuco, or cissus latifolia in the East,
on cutting, is a fact of the same class. The latter plant also
twines round other trees, and affords, as it were, a reservoir for
their use.

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