440 ON GENERATION. 



urine full of those excrements of the second digestion, wherefore 

 should we not conclude that the first digestion, or chylopoiesis, 

 has preceded? 



The embryo, therefore seeks for and sucks in nourishment 

 by the mouth ; and you will readily believe that he does so if 

 you rip him from his mother's womb and instantly put a finger 

 in his mouth; which Hippocrates thinks he would not seize 

 had he not previously sucked whilst in the womb. For we are 

 accustomed to see young infants trying various motions, making 

 experiments, as it were, approaching everything, moving their 

 limbs, attempting to walk, and uttering sounds, acts all of 

 which when taught by repeated experience, they afterwards 

 come to execute with readiness and precision. But the foetus 

 so soon as it is born, aye, before it is born, will suck ; doubt- 

 less as it had done in the uterus long before. For I have found 

 by experience that the child delayed in the birth, and before it 

 has cried or breathed, will seize and suck a finger put into its 

 mouth. A new-born infant, indeed, is more expert at sucking 

 than an adult, or than he is himself if he have but lost the 

 habit for a few days. For the infant does not suck by squeez- 

 ing the nipple with his lips as we should, and by suction in 

 the common acceptation ; he rather seems as if he would swallow 

 the nipple, drawing it wholly into his throat, and with the aid 

 of his tongue and palate, and chewing, as it were, he milks his 

 mother with more art and dexterity than an adult could prac- 

 tise. He therefore appears to have learned that by long cus- 

 tom, and before he saw the light, which we know full well he 

 unlearns by a very brief discontinuance. 



These and other observations of the same kind make it ex- 

 tremely probable that the chick in ovo is nourished in a two- 

 fold manner, namely, by the umbilical and by the mesenteric 

 veins. By the former he imbibes a nourishment that is well 

 nigh perfectly prepared, whence the first-formed parts are en- 

 gendered and augmented ; by the latter he receives chyle for 

 the structure and growth of the other remaining parts. 



But the reason is perhaps obscure why the same agent should 

 perform the work of nutrition by means of the same matter in 

 a variety of ways, since nature does nothing in vain. We shall 

 therefore endeavour to explain this. 



What is taken up by the umbilical veins is the purer and 



