142 EMBRYOLOGY IN THE SEVENTEENTH [pt. ii 



he made that the heart does not pulsate before the appearance of 

 the blood. No doubt his lack of microscopical facilities or of the 

 desire to use them affords the reason for this error, but it was a very 

 unfortunate one, for it was to a large extent upon it that he formulated 

 his doctrine "the life is in the blood". For example, he says, "I am 

 fully satisfied that the Blood hath a being before any other part of the 

 body besides, and is the elder brother to all other parts of the foetus ". 



The yolk, Harvey thought, supplied the place of milk, "and is 

 that which is last consumed, for the remainder of it (after the chicken 

 is hatched and walks abroad with the Henne) is yet contained in its 

 belly". He thus ranged himself with Alcmaeon and Abderhalden. 

 All his remarks about the relationships of yolk and white in nutrition 

 are worth consideration; in noting, for instance, that the yolk is 

 the last to be consumed, he comes very near to anticipating the 

 knowledge of the succession of energy-sources which we now possess 

 (see Section T"]). "In that Physitians affirme, that the Yolke is the 

 hotter part of the ^gg&, and the most nourishing, I conceive that they 

 understand it, in relation to us, as it is become our nourishment, 

 not as it doth supply more congruous aliment to the chicken in the 

 tggt. And this appeares out of our history of the Fabrick of the 

 chicken ; which doth first prey upon and devoure the thinner part of 

 the white, before the grosser; as it were a more proper diet, and did 

 more easily submit to transmutation into the substance of the foetus. 

 And therefore the yolke seems to be a remoter and more deferred 

 entertainment than the white; for all the white is quite and clean 

 spent, before any notable invasion is made upon the yolke." A com- 

 parison between these simple facts and our knowledge of embryonic 

 nutrition is most interesting (see Section 6-9). 



In connection with Minot's distinction of the periods of embryonic 

 growth, it is curious that Harvey says, "And now the foetus moves 

 and gently tumbles, and stretcheth out the neck though nothing of 

 a brain be yet to be seen, but merely a bright water shut up in a small 

 bladder. And now it is a perfect Magot, differing only from those 

 kinde of wormes in this, that those when they have their freedom 

 crawle up and down and search for their living abroad, but this 

 worm constant to his station, and swimming in his own provision, 

 draws it in by his Umbilicall Vessels". 



Sometimes Harvey confesses himself puzzled by problems which 

 could only be solved by chemical means, yet it does not occur to 



