GENERATION OF ANIMALS, V. iii. 



brain is by its nature the coldest part of the body ; 

 thus, as we should expect, it is the first part to feel 

 the effect : anything that is weak and poorly needs 

 only a slight cause, a slight momentum, to make it 

 react. So that if you reckon up (a) that the brain 

 itself has very little heat, (h) that the skin surrounding 

 it must of necessity have even less, and (c) that the 

 hair, being the furthest off of the three, must have 

 even less still, you •will expect persons who are plenti- 

 ful in semen to go bald at about this time of life. 

 And it is owing to the same cause that it is on the 

 front part of the head only that human beings go 

 bald, and that they are the only animals which do so 

 at all ; i.e. , they go bald in front because the brain is 

 there," and they alone do so, because they have by 

 far the largest brain of all and the most fluid. Women 

 do not go bald because their nature is similar to that 

 of children : both are incapable of producing seminal 

 secretion. Eunuchs, too, do not go bald, because of 

 their transition into the female state, and the hair 

 that comes at a later stage they fail to grow at all, 

 or if they already have it, they lose it, except for the 

 pubic hair : similarly, women do not have the later 

 hair, though they do grow the pubic hair. This 

 deformity constitutes a change from the male state 

 to the female. 



The reason why the hair does not grow again in 

 cases of baldness, although hair and feathers grow 

 again on hibernating animals and leaves on deciduous 

 trees, is that in the case of the animals and trees the 

 seasons are the turning-points of their lives more 

 (than in the case of man), and so when there is a 

 change of season, then they follow suit and grow or 



» See P.A. 656 b \2. 



525 



