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lusca forming a connecting link between them; and when we consider, to say nothing of their vital functions, that the actions of reptiles and fishes are for the most part sensualand instinctive, we shall expect a meaner development of brain than in animals of higher rank. Accordingly in fishes this organ is almost Auid, and does not fill the cranium. The cerebrum consists of two hemispheres, which are without convolutions, and are actually less than the origins of the olfactory nerves. The thalami and striated bodies, the cerebral ganglia of Spurzheim, are as large as the hemispheres ; and the cerebellum is larger than the entire brain. Under the hemispheres are two or more tubercles, analogous probably to the corpora quadrigemina of mammiferous animals, which, as in them, are the true optic ganglions. The magnitude of the olfactory tubercles, of which there are two pairs in the perch and salmon, accounts for the remarkable sense of smell in fishes, of which superiority naturalists have left on record many curious examples.* “ These animals," says M. Serres, “ have the largest quadrigeminal tubercles, " and the most remarkable eyes and optic nerves.”
6 The “ eye of a codfish," says Dr Fleming, “is equal in size to “ that of an ox;" and their reproductive powers, which bear a proportion to the size of their cerebellum, may be estimated by the profusion of their spawn. In reptiles, except the serpent,
“ which is more subtle than the other beasts of the “ field,” the anterior third of each hemisphere appears to be a bulb or root for the olfactory nerves. In all other respects there is a general resemblance between the encephala of these animals. It is worthy of remark, that some indivi. duals of these orders, which, according to the tables of Cuvier, are pre-eminent for the relative size of their brains, have some degree of intellect. Trout become very docile, and old carp are said to be wary and cunning. A variety of tricks are taught to the cobra de capello, boa, and other serpents. Toads, and even crocodiles, have become tame, and learned to know their benefactors.
* Monro's Comp. Anat. p. 127.
It has been doubted by some naturalists whether fishes and reptiles have taste and hearing; but that the nerves of these senses is feebly developed is certain. In fishes the auditory nerves arise so near to the origin of the fifth pair, that they have been considered as the same; and the nerves which supply the tongue are branches of those which proceed to the gills. A similar analogy runs throughout the remainder of their nervous systems. Like the nerves, both cerebral and spinal, the spinal chord is in proportion to the bulk of the body, and not to the brain with which it is connected; as in insects and zoophytes, it is this circumstance which accounts for the tenacity of life and powers
of restora tion of many reptiles. Tortoises will live for months after the removal of their brain, and the head and eyes of the decollated newt are regenerated. In serpents, which have no arms, there are no brachial nerves; and their size in fishes is proportional to the comparative smallness of those rudi. ments of arms, the fins. Again, as these latter animals respire by gills instead of lungs, the distribution of the pneumogastric nerve (par vagum) presents important deviations from its usual course in vertebral animals. Are we then to believe that the divisions of the nervous system, which appertain to the senses and voluntary powers, are adapted to the condition of the animal, and that the corresponding degradation of the cerebral portion, which belongs to the manifestations of the mental functions, is merely accidental ? Mr Charles Bell has said, “There are no accidents in nature !"
Not much higher in the scale of intelligence, for “they “ sow not, neither do they reap, nor gather into barns," birds have a brain analogous to that of reptiles and fishes. It consists of six distinct masses or tubercles; two hemis. pheres, two thalami, a cerebellum, and medulla oblongata. The hemispheres consist principally of the striated bodies ;
and the thalami, as in reptiles and fishes, are round and hollow. The cerebellum is also hollow, and, consisting of but one lobe, has no cerebellar commissure or pons, and the pyramidal and olivary bodies are hardly apparent. Their existence was denied by Cuvier and others; but until Gall and Spurzheim appeared, anatomists were not aware that these, and the restiform bodies, are the rudiments of the cerebrum and cerebellum. The surface of the brain presents no convolutions,—a most important deficiency, and a far more striking characteristic of defect than the comparison of relative size and weight; and they want the commissures called corpus callosum and fornix, and, of course, the sep
, tum lucidum and mamillary bodies. But they have, according to Dr Spurzheim, analogous organs of communication. The olfactory tubercles arise from the point of the hemispheres, of which they appear to be a mere continuation. Between the cerebral ganglia, or corpora striata, and thalami, as they are called, there are four roundish bodies, similar to those of fishes, analogous probably to the corpora quadrigemina of mammiferous animals, and, as in them, proportioned to the size of the optic nerves. Birds, like fishes, having no diaphragm, are without phrenic nerves; the nervus accessorius is wanting for a similar reason ; and, as might be expected, the facial nerve is hardly developed.
Between the instincts of birds, which, in the gregarious and migratory species, are very remarkable, and their cerebral configurations, Messrs Gall and Spurzheim have discovered a relation. The aquatic differ in this respect from land birds; and of the passeres, the brain of the male, which sings, is different from that of the female, which cannot sing. Again, birds which build nests and provide for their young are unlike the cuckoo and ostrich, whose heads are similar, and in which these instincts are never manifested, and so on through. out the entire range of their propensities. That many birds have intellectual powers is evident from the docility of the parrot, raven, and falcon. The gull, the wild duck, and the
plover, will feign lameness, to lead intruders from their young. And the conduct of the hooded crow (corvus cornix) in obtaining food from the larger shellfish, is perfectly rational. Dr Fleming, who was an eye-witness of its proceedings, thus describes them :-“ We have seen the hooded
crow in Zetland, when feeding on the testaceous mollusca, able to “ break some of the tenderer kinds by means of its bill, aided in
some cases by beating them against a stone; but as some of the “ larger shells, such as the buckie (buccinum undatum), and the “ wilk, cannot be broken by such means, it employs another me" thod by which it accomplishes its object. Seizing the shell in its “ claws it mounts up into the air, and then loosing its hold, causes the “ shell to fall amongst stones, (in preference to the sand, the wa“ter, or the soil of the ground,) that it may be broken, and give “ easier access to the contained animal. Should the first attempt !.« fail, a second and a third are made, with this difference, that the
crow rises higher into the air, in order to increase the power of “ the fall, and more effectually remove the barrier to the contained “ morsel. On such occasions we have seen a stronger bird remain “ an apparently inattentive spectator of the process of breaking " the shell
, but coming to the spot with astonishing keenness when “ the efforts of its neighbour had been successful, in order to share “ in the spoil.'
We now come to the mammalia, between which animals and man there is the nearest resemblance in functions and cerebral development. That brutes, in addition to the senses and instincts, have knowing faculties, is on all hands admitted. “ The ox knoweth his owner, and the ass his mas“ter's crib.” Nor are they entirely destitute of sentiments, as Cuvier observes. “ The affliction many of them feel on “ the absence or loss of a companion, friend, or benefactor, “is manifested by evident signs, in the same manner as they
testify their attachment without any temporary induce“ ment.” Surpassing him in the perfection of the senses and strength of the propensities, their inferiority in intellect and sentiments to man is unquestionable ; and yet when we see how feebly these are exerted in some men, and the consequent abuse of the propensities, we may exclaim with the poet,
“ Each kindred brute may bid thee blush for shame."
• Fleming's Phil, of Zoology, vol. i. p. 231,
Corresponding differences are to be found in their respective nervous systems. The nerves of sense in man are palpably smaller ;
he has a smaller cerebellum and nervous chord ; but he surpasses all other animals in the perfection of the brain. It has, indeed, been truly said, “ that by taking away, dimi
nishing, or changing proportions, you might form from the hu“ man brain that of any other animal ; while, on the contrary, " there is none from which you could in like manner construct the 66 brain of man.'
With respect to size, man, according to Sæmmering, has, without exception, the longest brain in comparison with the nerves that issue from it. The inferiority to the smaller birds in weight, when compared with the body, is not wonderful, when their leanness and natural levity are considered. Indeed, this criterion is in every point of view objectionable ; nor is that much better which is founded on the comparison of the cerebrum with the cerebellum and medulla oblongata, these parts and the brain bearing by no means a constant proportion to each other. As to form, the cerebrum of the human subject is elevated, whereas in brutes it is without elevation. It is nearly spherical in man; but in brutes is either oblong, as in herbivorous animals, or triangular, as in the carnivora. The differences in development and structure are no less remarkable. Excepting in the quadrumana, many of whose actions are almost human, and who differ from man to a distance indeed which is immeasurable, Cuvier says, the posterior lobes are wanting, and the anterior ones are imperfect, consisting in many animals of little more than the processus mamillaris or olfactory organ. The thalami or cerebral ganglia are smaller than in man. The convolutions are fewer and shallower, the corpora quadrigemina larger, being proportioned to the superior size of the visual organs, and there is considerably less cortical than medullary matter. “ Independ
ently of weight and size, Sæmmering observed fifteen visible
• Lawrence, p. 195.