40 1!. 9- 



derived from this centre that hinders the blood from coagulating ; ^ 

 indeed the blood, when withdrawn from its influence, actually 

 becomes putrid. Now the centre or origin of the blood-vessels 

 is the heart, and the centre or origin of the bones, in all animals 

 that have bones, is what is called the chine. With this all the 

 other bones of the body are in continuity ; for it is the chine 

 that keeps the body extended and straight But since it is 

 absolutely necessary that the body of an animal shall bend 

 during locomotion, this chine, while it is one in virtue of the 

 continuity of its parts, yet by its division into vertebrae is 

 made to consist of many segments. It is from this chine that the 

 bones of the limbs proceed, and with it they are continuous, in 

 •those animals that have limbs ; and these bones form joints at 

 the place where the limbs admit of flexure ; being fastened 

 together by sinews, and having their extremities adapted to each 

 other, either by the one being hollowed and the other rounded,^ 

 or by both being hollowed and including between them a huckle- 

 bone, as a connecting bolt, so as to allow of flexure and extension. 

 For without some such arrangement these movements would be 

 utterly impossible, or at any rate would be performed with great 

 difficulty. There are some joints, again, in which the lower end 

 of the one bone and the upper end of the other are alike in 

 shape. In these cases the bones are bound together by sinews, 

 and cartilaginous pieces are interposed in the joint, to serve as 

 a kind of padding, and to prevent the two extremities from 

 grating against each other. 



Round about the bones, and attached to them by thin fibrous 

 bands, grow the fleshy parts, for the sake of which the bones 

 themselves exist. For just as an artist, when he is moulding an 

 animal out of clay or other soft substance, takes first some solid 

 body as a basis, and round this moulds the clay ; so also has 

 nature acted in fashioning the animal body out of flesh. Thus we 

 find all the fleshy parts, with one exception, supported by bones, 

 which serve, when the parts are organs of motion, to facilitate 

 flexure, and, when the parts are motionless, act as a protection. 

 The ribs, for example, which enclose the chest are intended to 

 ensure the safety of the heart and neighbouring viscera. The 

 exception of which mention was made is the belly. The walls of 

 this are in all animals devoid of bones ; in order that there may 

 be no hindrance to the expansion which necessarily occurs in this 

 655 a. 



