708 PHILOSOPHICAL TRANSACTIONS. [aNNO 1702. 



For, were it not for that small share of muscular motion, which it exercises in 

 the womb, it might without absurdity be accounted for as a graft upon, or 

 brancli of the mother. 



Then follow some observations on the foetal circulation, and on the hy- 

 pothesis advanced by some writers, that the placenta supplies the fcEtus with air, 

 from the mother's blood ; whereas he supposes that " the uterine arteries 

 transmitting their blood immediately* to the umbilical vein, may very easily 

 transmit such nutritious juices or aerial particles as are contained in the blood, 

 along with it, without depositing them by the way." 



This opinion (he adds) is favoured by the structure and disposition of the 

 blood vessels on both parts ; so there is nothing in it difficult to be conceived, 

 or repugnant to experience. Late discoveries have made it appear, that the 

 arteries and veins are continued tubes, and that the latter contain nothing 

 but what they receive from the former ; and no reason appears why we 

 should think this method to be varied in the placenta. On the other hand, 

 if the arteries of the uterus were continued to the veins of the same part, and 

 those of the foetus in like manner, without communicating with each other, 

 their confluence in the placenta seems to be altogether impertinent, and of no 

 use, and the umbilical arteries and vein framed for no other service or purpose, 

 than to give the blood room for an idle sally. 



Thus the reasonableness of this old opinion may be vindicated ; but the cer- 

 tainty of it rests upon stronger proof. Mr. Cowper, to whose happy industry 

 we owe the confirmation of many ancient discoveries, and the benefit of some 

 new ones, has the honour to re-establish this old, but long exploded truth. 

 For by pouring mercury into a branch of the uterine artery of a cow, that went 

 into one of the cotyledons of the uterus, he filled those branches of the um- 

 bilical veins, which went from that cotyledon to the navel of the foetus. 



It would be a weak objection, to allege that the observation and experi- 

 ment being made on the uterus of a cow, the inference would not hold from 

 thence to a woman, the one being glanduliferous, and the other placenti- 

 ferous ; since every one of these cotyledons, or uterine glandules, is in all 

 respects a little placenta, and all the difference between them is in number, 

 name, and magnitude. But the great flux of blood which constantly follows 

 upon drawing the placenta from women, is as plain a demonstration to reason 

 of the continuity of the vessels, as Mr. Cowper's experiment is to the eye.-f- 



* It will be pointed out in a subsequent note that the uterine arteries do not immedialely transmit 

 their blood to the umbilical vein. 



f Nevertheless all attempts that have been made in the human subject to inject the umbilical vessels 

 from the uterine, and, vice versa, the uterine vessels from the umbilical, have constantly failed ; whence 

 it is to be inferred that there is no coutinuicy of vessels (as Dr. Drake supposes), no direct circula- 



