132 



M A M M A L I A. 



active, and, as we say, intelligent the animal is, 

 the more completely are the parts of its system deve- 

 loped ; and this holds in the case of the human body 

 as well as in the bodies of all animals. It would there- 

 fore be inconsistent alike with general reasoning and 

 with the facts, to suppose that there is any difference 

 in kind between the nervous system of man, and that 

 of the other mammalia ; though as the senses, taking 

 them altogether, are more uniformly strong and more 

 constant in their exercise in man than in the others, 

 lor this reason, and apparently for this reason 

 alone, the brain in man is much more developed ; and 

 in proportion as we find the senses more feeble in 

 some of their number, and more partial in their general 

 exercise, we find the brain smaller. But when we 

 attempt to make the brain the means of explaining 

 any of the phenomena of mind we are still more in 

 the dark, than when we endeavour to make it the 

 means of explaining the phenomena of sensation and 

 action in animals. In every case where the impression 

 in sensation or the exertion in action is sufficiently 

 strong, we find that it extends to the whole body of 

 the animal, and that the agitation of the parts most 

 remote from those which are immediately affected in 

 sensation or exerted in action, is in some cases as 

 great as that of those parts themselves. 



The only rational conclusion to which we can come 

 in animal physiology, notwithstanding the countless 

 hypotheses which have been broached upon the sub- 

 ject, is that we can have no abstract notion of animal 

 life, and therefore no means of actually separating it 

 into distinct functions, the influence of one of which 

 upon another can be at all understood. This term 

 " animal life," is merely a name, by means of which 

 we generalise all the phenomena of animals, just as 

 " matter" is merely a name, by which we generalise 

 all substantive existences which are in any way pal- 

 pable to our senses. In both cases, the phenomena 

 alone constitute the knowledge, and our general 

 names are merely short modes of expression, answer- 

 ing to which there are no real existences. In the 

 animal, however, we can carry our observation of 

 phenomena much farther, and more in a train of 

 succession, than we can do in the case of inanimate 

 matter ; and therefore the animal is by far the more 

 instructive study of the two. It is more sensitive to 

 external stimuli, arising from difference of situation, 

 difference of season, difference of weather, and every 

 thinff else of general nature which can have difference 

 at different times or in different places ; and besides 

 those obediences to external stimuli, there are internal 

 stimuli in an animal, arising from those necessities 

 which are inseparable from a material organisation, 

 in continual action in some of its parts, and therefore 

 requiring continual repair, the means of which are 

 contained in itself, though the materials are derived 

 from without, and taken in quantity proportionate 

 to the waste of the animal, and the fitness of the 

 alimentary substances for being applied to the pur- 

 poses of growth or of repair. 



There are many minor points in the physiology of 

 the mammalia as the highest or most typical class in 

 the animal kingdom ; but as there are, generally 

 speaking, adaptations to the situation and circum- 

 stances in which the animals are placed, they belong 

 to the details of the several orders and minor divisions 

 of the mammalia, rather than to the general functions 

 of the class. We shall therefore proceed to the next 

 branch of our general sketch of the order, namely, 



the modifications of their external action, and the 

 organs employed in that action, so as to suit them to 

 the places and the purposes for which they are ap- 

 pointed on the earth. Feeding is the grand stimulus 

 to action, at least to general action, during the whole 

 of every season of activity in all the mammalia ; and 

 as the food consists of a vast number of substances : 

 of plants, from the lichen which feeds the rein deer in 

 the polar latitudes, to the leaves and twigs of the most 

 lofty trees in tropical countries, and of the flesh of 

 every animal, from the small insect which is picked 

 up by the viscid matter on the projectile tongue of an 

 insectivorous animal of the humblest class, to that of 

 the elephant itself a knowledge of the food of the 

 mammalia requires at least a general knowledge of 

 the vegetable and animal productions of all parts of 

 the world ; and also of the situations in which they 

 are to be found, and the most ready means of getting 

 at them ; and thus the study of the mammalia, wheii 

 pursued in the proper manner, is a strong incitement, 

 and very soon becomes a clear and readily consulted 

 index, to natural history generally. 



The feeding of animals, from the arousing of the 

 animal by hunger, and its quitting the place of its 

 repose to go in quest of its food, till the food is 

 taken, prepared for the process of digestion by the 

 mouth, and the animal again relapses into a state of 

 repose, until fresh hunger shall excite it to a new 

 exertion, is conveniently divided into three successive 

 parts. Locomotion, or the conveying of the animal to 

 the place where the food is to be found ; prcheruion 

 or the taking of the food, whether vegetable or ani- 

 mal, wholly within the power of the animal ; and 

 mastication, or the action of the mouth in preparing 

 the food for the stomach. Our business in a general 

 sketch is to notice the leading diversities of the 

 organs by which these operations are performed, and 

 the adaptation thence traceable both to the place of 

 the animal in nature, and to its general structure. 

 We shall very briefly glance at each of these in a 

 separate section. 



III. ORGANS OF LOCOMOTION. The several kinds 

 of locomotion exercised by the mammalia, though 

 very many in their minor shades of distinction, may 

 be reduced to the general heads of climbing, flying, 

 running, leaping, and swimming ; and as these are 

 performed by means of the feet, there will of course 

 be the same distribution of the feet into general 

 heads ; only, as each operation indicated by the 

 general name is performed in various ways by dif- 

 ferent animals ; and as, in addition to this, the feet, 

 more especially the fore feet, have often other func- 

 tions to perform ; this circumstance will increase the 

 number of modifications. Among these, the organ of 

 flying is the one which performs its operation the 

 worst; because the general structure of the body, and 

 especially the articulation of the spine, the form of 

 the sternum, and the absence of coracoid bones under 

 the flying extremity, how much soever it may be 

 developed, render it a very ungainly organ of flight 

 as compared with the wing of a bird. 



The organs of flight, and also those organs which 

 are adapted for swimming and not for walking or 

 any motion upon the land, are so anomalous to what 

 may be considered as the true typical form of the 

 mammalia, that they are worthy of a separate notice ; 

 though in their physiology they are as decidedly 

 mammalia as any of the rest, and though in respect 

 of their feeding they ought to come under different 



