Letters 191 



and growth, are essentially the same. An animal, 

 therefore, naturally grows in the same manner as it 

 receives immediate nutriment from the first. Now 

 it is a most certain fact (as I have shown elsewhere) 

 that the embryos of all red-blooded animals are 

 nourished by means of the umbilical vessels from 

 the mother, and this in virtue of the circulation of 

 the blood. They are not nourished, however, imme- 

 diately by the blood, as many have imagined, but after 

 the manner of the chick in ovo, which is first nourished 

 by the albumen, and then by the vitellus, which is 

 finally drawn into and included within the abdomen 

 of the chick. All the umbilical vessels, however, are 

 inserted into the liver, or at all events pass through it, 

 even in those animals whose umbilical vessels enter the 

 vena portal, as in the chick, in which the vessels proceed- 

 ing from the yelk always so terminate. In the selfsame 

 way, therefore, as the chick is nourished from a 

 nutriment, (viz. the albumen and vitellus,) previously 

 prepared, even so does it continue to be nourished 

 through the whole course of its independent existence. 

 And the same thing, as I have elsewhere shown, is 

 common to all embryos whatsoever : the nourishment, 

 mingled with the blood, is transmitted through their 

 veins to the heart, whence moving on by the arteries, 

 it is carried to every part of the body. The foetus 

 when born, when thrown upon its own resources, and 

 no longer immediately nourished by the mother, makes 

 use of its stomach and intestines just as the chick 

 makes use of the contents of the egg, and vegetables 

 make use of the ground whence they derive concocted 

 nutriment. For even as the chick at the commence- 

 ment obtained its nourishment from the egg, by means 

 of the umbilical vessels (arteries and veins) and the 

 circulation of the blood, so does it subsequently, and 

 when it has escaped from the shell, receive nourishment 

 by the mesenteric veins ; so that in either way the chyle 

 passes through the same channels, and takes its route 



