OF ANIMALS. 



165 



a long and bifid chord or spinal marrow descending from it, of a smaller dia- 

 meter than the gland itself; and, secondly, both are severally enclosed in a 

 bony case or covering. 



In man, as we have already observed, this gland, or ganglion, is (with a 

 few exceptions) larger than in any other animal, in proportion to the size of 

 the body ; without any exception whatever in proportion to the size of the 

 chord or spinal marrow that issues from it. 



In other animals, even of the vertebral classes, or those immediately before 

 us, we meet with every variety of proportion ; from the ape, which, in this 

 respect approaches nearest to that of man, to tortoises and fishes, in which 

 the brain or ganglion does not much exceed the diameter of the spinal mar- 

 row itself. 



It is not therefore to be wondered at that animals of a still lower descrip- 

 tion should exhibit proofs of a nervous chord or spinal marrow, without a 

 superior gland or brain of any kind ; and that this chord should even be des- 

 titute of its common bony defence. And such is actually the conformation 

 of the nervous system in insects, and, for the most part, in worms ; neither 

 of which are possessed of a cranium or spine, and in none of which we are 

 able to trace more than a slight enlargement of the superior part of the 

 nervous chord, or spinal marrow, as it is called in other animals — a part situ- 

 ated near the mouth, and apparently intended to correspond with the organ 

 of a brain. The nervous chord, however, in these animals, is, for the most 

 part, proportionally larger than in those of a superior rank ; and at various 

 distances is possessed of little knots or ganglions, from which fresh ramifica- 

 tions of nerves shoot forth, like branches from the trunk of a tree, and which 

 may perhaps be regarded as so many distinct cerebels or little brains. 



In zoophytic worms we can scarcely trace any distinction of structure, 

 and are totally unable to recognise a nervous system of any kind. The com- 

 mon and almost transparent hydra or polype, which is often to be found in 

 the stagnant waters of our own country, with a body about an inch long, and 

 arms or tentacles in proportion, appears to consist, when examined by the 

 best glasses, of nothing but a granular structure, something like boiled sago, 

 connected by a gelatinous substance into a definite form.* Hydatids and 

 infusory animals exhibit a similarity of make. The common formative prin- 

 ciple of all these may be reasonably conjectured to consist in the living 

 power of the blood alone, or rather of the fluid which answers the purpose of 

 blood ; and their principles of action to be little more than instinctive. 



Can we, then, conceive that all these different kinds, and orders, and 

 classes of animals, thus differently organized and differently endowed with 

 intelligence, are possessed of an equality of corporeal feeling? or, to adopt 

 the language of the poet, that — 



the poor worm thou tread'st on, 

 In corporal suffering, feels a pang as great 

 As when a giant dies ? 



This is an interesting question, and deserves to be examined at some 

 length. It may, perhaps, save the heart of genuine sensibility from a few of 

 those pangs which, even under the happiest circumstances of life, will be 

 still called forth too frequently ; and if there be a human being so hardened 

 and barbarized as to take advantage of the conclusion to which the inquiry 

 may lead us, he will furnish an additional proof of its correctness in his own 

 person, and show himself utterly unqualified for the discussion. 



Life and sensation, then, are by no means necessarily connected: the 

 blood is alive, but we all know it has no sensation ; and vegetables are alive, 

 but we have no reason to suppose they possess any. Sensation, so far as we 

 are able to trace it, is the sole result of a nervous structure. Yet, though 

 thus limited, it has already appeared that it does not exist equally in every 

 kind of the same structure, nor in every part of the same kind. The skin is 



* Blumenbach, Anat. Comp. $ 203. 



