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
