ii. 6. 33 



and ripens into maturity, the marrow changes its colour, just 

 as do the external parts and the viscera.^ For the viscera also 

 in very young animals have each and all a blood-like look, 

 owing to the large amount of this fluid which they contain. 



The consistency of the marrow agrees with that of the fat. For 

 when the fat consists of lard, then the marrow also is oily and 

 lard-like ; but when the concocted blood is converted into suet, 

 and does not assume the form of lard, then the marrow also 

 has a suety character. In those animals, therefore, that have 

 horns and are without upper front teeth, the marrow has the 

 character of suet ; while it takes the form of lard in those that 

 have front teeth in both jaws, and that also have the foot divided 

 into toes. What has been said hardly applies to the spinal 

 marrow. For it is necessary that this shall be continuous and 

 extend without break through the whole back-bone, inasmuch 

 as this bone consists of separate vertebrae. But were the spinal 

 marrow either of soft fat or of suet, it could not hold together 

 in such a continuous mass as it does, but would either be too 

 fluid or too frangible.* • 



There are some animals that can hardly be said to have 

 any marrow. These are those whose bones are strong and 

 solid, as is the case with the lion. For in this animal the 

 marrow is so utterly insignificant, that the bones look as though 

 they had none at all.^ However, as it is necessary that animals 

 shall have bones or something analogous to them, such as the 

 fish-spines of water-animals,^ it is also a matter of necessity that 

 some of these bones shall contain marrow ; for the substance 

 contained within the bones is the nutriment out of which 

 these are formed. Now the universal nutriment, as already 

 stated, is blood ; and the blood within the bone, owing to the 

 heat which is developed in it from its being thus surrounded, 

 undergoes concoction, and self-concocted ''' blood is suet or lard ; 

 so that it is perfectly intelligible how the marrow within the 

 bone comes to have the character of these substances. So also 

 it is easy to understand, why, in those animals that have strong 

 and solid bones, some of these should be entirely void of marrow, 

 while the rest contain but little of it ; for here the nutriment is 

 all spent in forming the bones. 



Those animals that have fish-spines in place of bones have 

 no other marrow than that of the chine.^ For in the first place 

 652 a, 3 



