170 EMBRYOLOGY IN THE SEVENTEENTH [pt. ii 



was forgotten until Beddoes drew attention to it in 1 790, but since then 

 many have praised it and Schultze makes him the equal of Harvey. 



The reason why he became interested in embryology is given in 

 the opening sentences of his work. "Since the necessity of breathing", 

 he says, "is so essential to the sustaining of life that to be deprived 

 of air is the same as to be deprived of common light and vital spirit, 

 it will not be out of place to enquire here how it happens that the 

 foetus can live though imprisoned in the straits of the womb and 

 completely destitute of air." He first of all gives an account of the 

 opinions held about foetal respiration and the umbilical cord. He 

 says that he disagrees (i) with the view that the embryo breathes 

 per OS while it is in the womb, for there is no air in the amnion and 

 the suctio infantuli proves nothing; and (2) with the view pro- 

 pounded by Spigelius that the umbilical vessels existed to supply 

 blood to the placenta for the nourishment of the latter. If this were 

 the case, he says, the membranes in the hen's egg could not be formed 

 before the vitelline vein, as they are, and in cases of foetal atrophy 

 the placenta would always die and be corrupted too, which does not 

 happen. Nor does he support the view of Harvey (3) that the 

 umbilical vessels supply blood for the concoction and colliquation 

 of the food of the foetus, for why should not the embryonic body 

 prepare its own nutritious juice before birth just as it does afterwards. 

 He further thinks the theory (4) that the umbilical vessels are for 

 carrying off surplus foetal nourishment quite untenable and as little 

 likely as the theory (5) that they exist for the object of allowing a 

 foetal circulation — for this could just as well be accomplished through 

 the vessels which exist in the embryonic body. 



Mayow decides therefore for the opinion of divino sene Hippo- 

 crate and Everard that the umbilicus is a respiratory mechanism, 

 carefully dissociating himself, however, from the hypothesis of 

 Riolanus that the umbilical cord with all its windings is so arranged 

 to cool the blood passing through it. He then says, "We observe, 

 in the first place, that it is probable that the albuminous juice exuding 

 from the impregnated uterus is stored with no small abundance of 

 aerial substance, as may be observed from its white colour and frothy 

 character [Needham's uterine milk]. And in further indication of 

 this, the primogenial juices of the egg, which have a great resemblance 

 to the seminal juice of the uterus, appear to abound in air particles. 

 For if the white or the yolk of an tgg be put into a glass from which 



