188 AN ANIMAL MAY BE KNOWN FROM ONE OF ITS BONES. 



tern, of which all the different parts mutually correspond, and concur in the 

 same definitive action by a reciprocal re-action. No one part can undergo 

 a change without a corresponding change taking place in all the others ; and, 

 consequently, each part taken separately, indicates and gives the key to a 

 knowledge of all the rest. 



" Thus, it the stomach of an animal is so organized as only to digest fresh 

 animal food, its jaws must also be so contrived as to devour such prey ; its 

 claws, to seize and tear it ; its teeth, to cut and divide it ; the whole struc- 

 ture of its locomotive organs, to pursue and obtain it; its organs of sense, to 

 perceive it from afar ; and nature must have even placed in its brain the 

 necessary instinct to enable it to conceal itself, and to bring its victim within 

 its toils. Such will be the general conditions of a carni'vorous animal ; they 

 must inevitably be brought together in every species intended to be carni'- 

 vorous, for its race could not subsist without them ; but under these general 

 conditions there exist also special ones, relating to the size, the habits, and 

 the haunts of the prey, on which the animal is to exist ; and from each one 

 of these special conditions there result certain modifications, in detail, of the 

 form required by the general conditions ; so that not merely the class, but 

 the order, the genus, and even the species, will be found expressed by, and 

 deducible from, the structure of each part. 



**ln order, for example, that the jaws may be enabled to seize the prey, 

 there must be a certain shaped prominence for its articulation ; a certain 

 relation between the position of the resistance and that of the power, with 

 respect to that of the fulcrum ; a certain magnitude of the muscle that works 

 the jaw, requiring corresponding dimensions of the pit in which that muscle 

 is received, and of the convexity of the arch of bone beneath which it passes, 

 while this arch must also possess a certain amount of stiength, to enable it to 

 bear the strain of another muscle. 



"That the animal may be enabled to carry off its prey, a certain degree 

 of strength is necessary in the muscles which support the head ; whence 

 results a peculiar structure in the vertebrae to which these muscles^are at- 

 tached, and in the back of the skull where they are inserted. 



"That the teeth may be adapted to tear flesh, they must be sharp; and 

 they must be more or less so, exactly according as they are likely to have 

 more or less flesh to tear, while their bases must be strong in proportion to 

 the quantity of bone, and the magnitude of the bones they have to break. 

 Every one of these circumstances will have its effect on the development of 

 all the parts which assist in moving the jaw. 



" That the claws may be able to seize the prey, there must be a certain 

 amount of flexibility in the toes, and of strength in the nails ; and this 

 requires a peculiar form of the bones, and a corresponding distribution of the 

 muscles and tendons ; the fore-arm must possess a certain facility in turning ; 

 whence also result certain forms of the bones of which it is made up; and 

 these bones of the fore-arm, articulating to the humerus, cannot undergo 

 change without corresponding changes taking place in this latter bone. The 

 bones of the shoulder also require to have a certain degree of strength, when 

 the anterior extremities are to be used in seizing prey ; in this way again 

 other special forms become involved. The proper and free play of all these 

 parts requires certain proportions in all the muscles concerned in the mo- 

 tions of the fore-leg, and the impression of the museles so proportioned will 

 determine still more definitely the structure of the bones. 



"It is easy to perceive that similar conclusions might be drawn as to the 

 structure of the posterior extremities, which contribute to the rapidity of the 

 general movement of the body; or of the vertebra?, which influence the 

 facility or" those movements ; and also as to the structure of the bom-s of the 

 t'aee. in their relation to the degree of development of the external senses. In 



