THE MAMMALIA— MAN AND BEASTS. 
3a 
Mammalia, and tliesc are lean and meagre. Tiie Rodentia generally possess the 
largest proportional Brain, and the Pachydermata the smallest. It is very difficult, 
if not impossible, to arrive at these results with any great degree of accuracy, because 
the weight of the brain generally remains the same, while that of the body will vary 
considerably according as an animal is lean or fat. 
The proportion which the Cerebrum bears to the Cerebellum is, in 
The Squirrel Monkey (CaZhW'ri* sciarcMs), . . as 
Man, ............. 
The Ox (Ros iaurus), ......... 
Dog familiaris), . . . 
Wild Boar (Sas scroyjAa), ........ 
Horse (Eqnvs cahallus), . , . . . ... 
Cat (Fulii calus), ......... 
Haro (^Lepm timidus), . . . ■ . . . ... 
Sheep ( Oris aries), . . . . . 
Mouse (d/us nmsculus)^ . . . . . ... 
14 to 1 
9 ... 1 
9 ... 1 
8 ... 1 
7 ... 1 
7 ... 1 
6 ... 1 
G ... 1 
5 ... 1 
2 ... 1 
“ It is a common opinion,” observes Dr Herbert Mayo, “ that the fi ont of the 
brain is the seat of the inlellectual faculties; yet in Monkeys and in Man the back 
part of the brain is that which has the largest relative size. The sheep, on the other 
hand, has an ample front to its brain, a large intellectu.al region, according to the 
phrenological theory, while its instinct of .attachment to its young has a poor locality 
in its moderate posterior cerebral lobe. Has nothing then been discovered to mark 
an essential superiority in the brain of Man? The question must, I believe, be 
answered in the negative. Ko physical condition, distinguishing the hum.an brain 
from that of animals, and therefore fitting it to co-operate with a rational soul, has as 
yet been ascertained, or even plausibly conjectured to exist.” 
Physiologists have been led, in all ages, by that in.trkcd superiority of mental power 
which Man possesses above the other animals, to seek in the structure of their brains 
for some corresponding difference. It was long supposed that Man has the largest 
brain in comparison to liis body ; but the above Tables show that ho is surpassed by 
several Quadrumana, and by the Mouse. 
There is another point of comparison which seems to approach nearer to their actual 
comparative intelligence, which was first proposed by Siimmering. By comparing the 
quantity of the brain with that of the nerves arising from it, we ascertain more 
aceurately the degree in which its purer intelligence excels its more animal nature. 
“ Let us divide the brain into two parts; that which is immediately connected with 
the sensorial extremities of the nerves, which receives the impres.sions, and is there- 
fore devoted to tlic purposes of animal existence. The second division will include 
tlie rest of the brain, which may be considered as connecting the functions of the 
nerves with the faculties of the mind. In jiroportion, then, as any animal possesses a 
larger share of the latter and more noble part— that is, in proportion as the organ of 
reflexion exceeds that of the external senses— may we expect to find the powers of the 
mind more vigorous and more clearly developed. In this point of view Man is 
decidedly pre-eminent; hero he excels all other animals which have hitherto been 
investigated." Sommering found that the brain of Man never weighed less than 2 lb. 
^ or., while that of the Horse never ex<'oeded 1 lb. 4 oz. in weight. But the nerves 
arising from the brain of the Horse wore at least ten times larger than those in 
Man. 
However ingenious this theory may bo, it is not found to hold good in every 
instance ; and even if proved, it would still leave the nature of the union between 
Mind and Matter as mysterious and as incomprehensible as ever. 
The nerves of the Mammalia bear a striking resemblance in their disposition to 
those of Man, with the exception of the olfactory nerves, width are large .and hollow 
processes of the anterior lobes of the .-erebrum, the cavities of which communicate 
with the lateral v»;nlrjcles of the brniu. 
Their eyes, invarinbly placed in their orbits, and pre-served by two eye- 
lids and the vestige of a tliird, liavc their crystalline humour preserved 
l)y the ciliary process, and sclerotic coat, composed of simple cellular 
substance. 
The eye-hall of Man is nearly globular, and about one inch in di.ameter. It is 
defended externally by a white ojiaquc membrane, having the density of tanned leather, 
called the Sclerotica, which surrounds every part, excepting the small circular por- 
tion in front called the Cornea, and a small perforation behind to .admit the optic 
nerve into the brain. The Cornea is perlectly transparent and po.ssesses great sensi- 
“dity ; yet at the same time it is so tough, as to ofler a powerful resistance to external 
tujury. Within the Cornea, and immediately in cojitact with it, is placed a small 
quantity of pellucid fluid called the Jqueous humour, whi.d. occupies the external 
viiuble portion of the Eye. Tim /m is situate behind the Cornea and the Aqueous 
bumour. It consists of a circular membrane, perforated by a small hole in tl.c centre 
ualled the Fnpil. The colour of 11, e Eye rc.,ides iu this membrane, ana both its 
Mructure and functions are very remarkable. It is formed of two layevs of fibres ; in 
'he one, they are arranged like rays from the inner to the outer margin; and in the 
U'hcr, they form concentric circles. By the action of the radiated fibres, tl.e pupil is 
wntracted ; but it is dilated by the action uf the circular fibres. Those delicate motions 
e executed in a manner which hum.an ingenuity in vain attempts to equal. The 
pupil instantly contracts when exposed to a strong light; but when the light is dcli- 
^uut. It dilates readily, in order to admit as groat a number of rays as possible, 
ehind the pupil, a fluid in tlio shape of a double convex lens is jilaced, called the 
r’Jstalline humour, formed of denser materiajs than any other liquid in the human 
ye. The remaining itortion is filled up with the Vitreous humour, which is the most 
Plentiful of all its fluids. Tho inside of the Sclerotica being lined wiili a coloured 
of*th uuhed riQmentum uiijruin, or black Pigment, and tiin inner surface 
wia * brown pigment, any scattered rays of liglit w-hich would other- 
•ame vision obscure are intercepted. Those pigments are therefore of the 
e utility with tho black paint which linos the interior of telescopes and other 
optical instruments. The Retina, or expanded extremity of the optic nerve, is the 
immediate seat of sensation. Upon this delicate membrane, an inverted picture of 
the external scene is exactly delineated; and though scarcely half an inch in diameter, 
it contains the forms, positions, and colours of the most distant objects, without confu- 
sion or irregularity. 
The black pigment of the Eye is wanting in that variety of tho Human race 
called Albinos, and this deficiency is connected with the want of colouring principle 
in the hair. The Rabbit, Mouse, and Horse, are sometimes found to possess this 
peculiarity when they are said to be glass-eyed. They are capable of transmitting 
it to their posterity, and thus forming a breed of white animals. The Ferret’s eye 
b naturally destitute of the black pigment. 
The immediate object of vision is colour, and to this alone its function was origin- 
ally confined. By habit and by comparison with tho other senses, but especially 
with that of touch, it acquires new powers; and the coloured canvas of original per- 
ctqition is embodied into a real scene, in which the distance, magnitude, and figures 
of objects may be, in general, iustaulaneously discovered. This reraai'kable fact was 
fully established by Mr Clicselden, who couched tho eyes of a young gentleman born 
blind, and ascertained tho effects produced on the mind by the first exercise of the 
power of vision. ' 
By certain exquisite contrivances, the Eye is so constructed as to correct the de- 
fects which Opticians experience in their own artificial instruments. But the consi- 
deration of the Spherical, Paralactic, and Chromatic Aberrations of light, belongs 
more properly to the science of Optics. 
In the Mammalia, the eye is composed of the same coats and humours as in Man, 
being only slightly modified and adajitod to surrounding circumstances. The eyes of 
the Cetaceous tribes more nearly resemble those of Fishes, as they are flattened on the 
anterior side, and adapted to the dense medium in which they reside. By the exqui- 
site arrangement of the sclerotic coat and cornea in the Seal tribe, these animals are 
able to adapt their vision to the two different media of air anil water; and they are 
enabled to shorten or elongate the axis of the eye according to circumstances. The 
eye of the Mus typhlus, or Blind Rat, is not larger than a poppy seed, and is alto- 
gether covered with hair, so that the animal can scarcely pen- live tho difference 
between light and dai-kness. The eyes of the Slole are so minute that most persons 
imagine them to be entirely absent. Tlie pigment at the hr ik t " the eye receives the 
name of the Fapetum lucldum; it is of different colours in different animals. 
In the Monkey it is dark-coloured. 
Dx, , groeu. 
pale yellow'. 
Rabbit, Hare, and Ilog, .... browii. 
Lion, Bear, Cat, and Dolphin, . . pale golden yellow. 
Dog, Wolf, and Badger, .... pare white, fringed with blue. 
Horse, Goat, Stag, and Buffalo, . . silvery blue, oliaiiging to violet. 
It has been supposed that the Tapetum enables these animals to see more distinctly 
in the dark. 
In the Ear a cavity is always found called the Tympanum or Ear-drum, 
which communicates with the hinder part of the mouth by a canal called 
the Eustachian tube. Tliis cavity is closed exteraal'y by a membrane, 
termed the membrana tympani, and contains within it a chain of four hones, 
called the Malleus, or Hammer Bone ; the Incus, or Anvil ; the Os Orhi- 
culare, or Lenticular Bone; and the Stapes, or Stirrup. The Stapes 
rests upon a vcstihulum or central porch, which leads on the one side to 
three semi-circular canals, and on the other to a Cochlea, or spiral canal, 
which conimunicates by one extremity with the vcstihulum, and by the 
otlier with tlie Tympanum. 
Tlie Vestibule, Coehloa, and semi-circular canals, collectively form tho Labyrinth. 
This is the essential part of the organ; and no obstruction or removal of the external 
parU can altogetber destroy the sense of heaving as long as the Labyrinth remains 
uuiiijured. Tlie precise uses of lliese sevnal parts are not yet fully understood. 
I he Mammalia do not appear to be capable of distinguishing musical sounds with 
that nicety, or of deriving that extent of enjoyment which has been bestowed on Man. 
Tlie Dog may be trained to distinguish one particular tunc from another ; but the 
extent of his pleasure or acqnireiiients see.m3 greatly limited. But JIan, besides being 
able to perceive diffcreiiecs between acute, and grave tones, is capable of distinguisliing 
four or five hmidred varieties in tlieir quality and intensify. A flute, hautboy, and 
violiiieollo may all sound the same note, and yet the peculiar quality of each may be 
reaihlyr -recivcd. An atteiiiivo ear will observe some differences althougli twenty 
Immaii voices sound the same note, and with equal strength; nay. even the same voice 
m-ay bo varied in niiuiy ways, by sickness or healtli, youtli or age, leanness or fatness, 
good or bad humour; and the same words spoken by foreigners and natives, or even 
by the inhabitants of different provinc.s i.i the same nation, will be readily distin- 
guished. 
lo ascertain the effect of tho high and low notes of the piano-forte upon tlie Ele- 
phant and Lion, Sir Everard Home procured one of Broadwood’s piano-fortes to 
make tlio experiment at tho Munagerie iu Exeter Cl.angc, Loudon. Tho Elephant 
was first tried. His attention was scarcely attracted bj' tho high notes; but when 
the low ones wore played, he brought Ids broad cai-s foiward, remained evidently lis- 
tening, and made use of sounds rather expressive of satisfaction than otlierwisc. The 
full sound of the French horn produced the sumo effect. But the Lion was much 
more forcibly affected. Wlien the high notes were played he remained silent and 
motionless, but listening with deep attention. No sooner, how'cver, were the low 
notes sounded than he sprang up, endeavoured to break loose, lashed his tail, and ap- 
peared to be enraged and furious, so much so, as to alarm the female spectators. Tbi« 
was accomjianied with the deepest yells, which ceased with the music. 
The Cranium, or .skul! of the ]\lanimalia, may be subdivided into 
