GENERATION OF ANIMALS, V. i. 



not-being to being is effected through the inter- 

 mediate state, and sleep would appear to be by its 

 nature a state of this sort, being as it were a border- 

 land between li^^ng and not liWng : a person who is 

 asleep would appear to be neither completely non- 

 existent nor completely existent : for of course it is 

 to the waking state par excellence that life pertains, 

 and that in virtue of sensation. On the other hand, 

 assuming it is necessary that an animal should possess 

 sensation, and that it is first an animal at the moment 

 it has first acquired sensation, we ought to regard its 

 original state not as being sleep but something re- 

 sembling sleep — the sort of state that plants also are 

 in ; indeed the fact is that at this stage animals are 

 living the Ufe of a plant. Sleep, however, cannot 

 possibly pertain to plants, because there is no sleep 

 from which there is not an awaking, and there is no 

 awaking from the condition in plants which is ana- 

 logous to sleep. An}"\vay, young animals must of 

 necessity sleep for the greater part of the time be- 

 cause the burden of their groMth and the consequent 

 weight is laid upon the upper regions of the body." 

 (We have explained elsewhere * that such is the 

 cause of sleep.) All the same, animals are clearly 

 found to wake even within the uterus, as is shown 

 by dissections and by the case of the Ovipara ; after- 

 wards they immediately drop off and fall asleep 

 again. That is why after birth as well they spend 

 most of their time asleep. 



Infants do not laugh while they are awake, but 

 they both laugh and weep while they are asleep, for 

 of course sensations occur in animals during sleep as 



regions of the body becoming weighed down by various hot 

 substances which are carried up to them. 



