GENERATION OF ANIMALS, V. vii. 



\^-ill travel quickly. So then, the movement which a 

 strong agent produces is sometimes slow (i.e., when, 

 in virtue of its strength, it is mo\'ing alarge amount), 

 and sometimes fast {i.e., when the agent has the 

 upper hand). In accordance with the same line of 

 argument, in some cases the movement which a weak 

 agent produces is slow (i.e., when the agent is setting 

 in movement an amount which is too large for its 

 strength), in other cases the movement is fast (i.e., 

 when o\^ing to the agent's weakness the amount 

 which it sets mo\-ing is small). 



Such, then, are the causes to which these con- 

 trarieties are due. We have shown (a) why neither 

 voung, nor old, nor male nor female animals all have 

 high-pitched voices or all have deep voices ; (h) why 

 sick and healthy alike speak in a high-pitched voice ; 

 and (c) why, as men reach old age, the pitch of "their 

 voice rises, although old age is the opposite of youth. 



On account of their debilit}-, most animals when 

 young, and most females, set but a small amount of 

 air in movement and therefore have high-pitched 

 voices, because a small amount is propelled at a fast 

 speed, and where the voice is concerned fast means 

 high. In calves, however, owing to their age, and in 

 cows, owing to the nature of femininity, the part by 

 means of which they set (the air) in movement is not 

 strong, and as they set a large amount of it in move- 

 ment, they have deep voices, for a large amount of 

 air travels slowly, and anything that travels slowly is 

 heavy (deep).* A large amount (of air) is set in 

 movement by these animals, but only a small amount 

 by the others, the reason being that in the former 

 the vessel through which their breath first travels has 

 a large opening and is therefore forced to set a large 



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