34 ii- 6— ii. 7. 



they have naturally but a small amount of blood ; and secondly 

 the only hollow fish-spine is that of the chine. In this then 

 marrow is formed ; this being the only spine in which there is 

 space for it, and moreover being the only one which owing to 

 its division into parts requires a connecting bond. This too is 

 the reason why the marrow of the chine, as already mentioned, 

 is somewhat different from that of other bones. For, having to 

 act the part of a clasp, it must be of glue-like tenacity, and at 

 the same time sinewy^ so as to admit of stretching. 



Such then are the reasons for the existence of marrow, in those 

 animals that have any, and such its nature. It is the surplus 

 of the sanguineous nutriment apportioned to the bones and fish- 

 spines, which has undergone concoction owing to its being enclosed 

 within them. 



(Ch. y.) From the marrow we pass on in natural sequence to 

 the brain. For there are some^ who think that the brain itself 

 consists of marrow, and that it forms the commencement of that 

 substance, because they see that the spinal marrow is continuous 

 with it. In reality the two may be said to be utterly opposite 

 to each other in character. For of all the parts of the body there 

 is none so cold as the brain ; whereas the marrow is of a hot 

 nature, as is plainly shown by its sheeny appearance,^ and by 

 its fatness. Indeed this is the very reason why the brain and 

 spinal marrow are continuous with each other. For, wherever 

 the action of any part is in excess, nature so contrives as to 

 set by it another part with an excess of contrary action, so that 

 the excesses of the two may counterbalance each other. Now 

 that the marrow is hot is clearly shown by many indications. 

 The coldness of the brain is also manifest enough. For in the 

 first place it is cold even to the touch ; and, secondly, of all the 

 fluids of the body it is the one that has the least blood ; for 

 in fact it has no blood at all in its proper substance.^ This 

 makes it the most consistent of all the fluids.^ This brain is 

 not an excretion, nor yet is it one of the parts which are 

 anatomically continuous with each other ; but it has a character 

 peculiar to itself, as might indeed be expected. That it has no 

 continuity with the organs of sense is plain from simple inspection, 

 and is still more clearly shown by. the fact, that, when it is touched, 

 no sensation is produced;'^ in which respect it resembles the 

 blood of animals and their excrement.^ The purpose of its 

 652 b. 



