PARTS OF ANIMALS, II. vi.-vii. 



and so it is sticky ; and it is sinewy too so that it 

 can stretch. 



We have now explained why marrow is present in 

 certain animals. We have also made clear what 

 marrow is. The surplus of the blood-like nourishment 

 which is distributed to the bones and spine gets 

 enclosed within them, and after it has undergone 

 concoction then it is marrow. 



yil. The brain is the next subject on our list. It Brain, 

 comes appropriately after the marrow, as many think 

 that the brain is really marrow " and is the source of 

 the marrow, because, as observation shows, the spinal 

 marrow is continuous with the brain. As a matter 

 of fact, however, the two are quite opposite in nature. 

 The brain is the coldest of all the parts in the body, 

 whereas the marrow is hot, as is shown by the fact 

 that it is greasy and fat. And that is the real reason 

 why the spinal marrow is continuous with the brain. 

 Nature is always contriving to set next to anything 

 that is excessive a reinforcement of the opposite sub- 

 stance, so that the one may level out the excess of 

 the other. Now there are many indications that the 

 marrow is hot ; and the coldness of the brain is 

 shown not only by its being cold to the touch, but 

 also by its being the driest of all the fluid parts of the 

 body and the one that has the least blood in it — in 

 fact, it has none at all. It is, however, not a residue, 

 nor is it to be classed among the parts that are con- 

 tinuous. It is peculiar in its nature, and this after all 

 is but reasonable. Inspection shows that the brain 

 has no continuity with the sensory parts, but this is 

 shown still more unmistakably by the fact that like 

 the blood and the residue of animals it produces no 

 sensation when it is touched. 



« Cf. Plato, Timaeus 75 c, d. 



149 



