SENTIMENTS OF SABATIER, ETC. 535 



The theory of Sabatier appears to be this : the umbilical vein brings from the 

 placenta blood which has a quality essential to the animation of the foetus. 

 If there were no particular provision to the contrary, a large portion of this 

 blood, after passing from the umbilical vein by the inferior cava into^rhe right 

 auricle of the heart, would proceed by the right ventricle through the pulmo- 

 nary artery and arterial canal, into the aorta, below the origins of the carotid 

 and subclavian arteries ; and consequently none of it would pass to the head 

 and upper extremities, but a considerable part would return again by the 

 umbilical arteries to the placenta, without circulating through the body : while, 

 on the other hand, the blood which passed by .the carotid and subclavian 

 arteries to the head and upper extremities returning from them to the heart 

 by the superior cava, might pass from the right auricle to the left auricle and 

 ventricle and the aorta, and so to the head and upper extremities again, 

 without passing through the placenta. But by means of this valve, the blood 

 of the lower cava, and of course of the umbilical vein, is directed to the left 

 auricle and ventricle and the aorta, by which a considerable portion of it will 

 necessarily pass to the head and upper extremities ; while the blood which 

 returns from these parts by the superior cava, must consequently pass from 

 the right auricle into the right ventricle and pulmonary artery; from whence 

 a large portion of it will proceed through the arterial canal into the aorta 

 beyond the carotids and subclavians, and of this portion a considerable part 

 will go to the placenta by the umbilical arteries. Sabatier 'compares the 

 course of the blood in the foetus to the course of a fluid in a tube which has 

 the form of the numeral character 8.* If this doctrine be true, the progress 

 of the blood in the fostus and placenta is very analagous to that of the double 

 circulation of the adult ; the character 8 answering equally well in the 

 description of either subject. 



According to Sabatier, the blood of the placenta takes this peculiar course 

 through the heart, in order that some of it may be carried to the head and 

 upper extremities. But an additional reason may be suggested, which appears 

 to be of great importance ; namely, the supplying of the coronary or proper 

 vessels of the heart, with some of the same blood. 



The heart of the adult, as has been before stated, cannot act without its proper 

 or coronary arteries are supplied with arterial blood. The heart of the foetus 

 performs a more extensive circulation than that of the adult, and, therefore, 

 is probably in greater need of such blood. But unless the blood of the placenta 

 pass through the foramen ovale into the left auricle and ventricle, and so to the 

 aorta, it cannot enter the coronary arteries which originate at the commencement of 

 the aorta ; for the blood which flows from the right side of the heart through 

 the arterial canal, passes into the aorta at so great a distance from the orifices 

 of the coronary arteries, that it certainly cannot enter them. 



The whole of this doctrine seems to be supported by a fact very familiar to 

 accoucheurs, viz. the occurrence of death in the foetus whenever the circula- 

 tion through the umbilical cord is suspended during fifteen or twenty min- 

 utes ; for as the placenta imparts to the foetal blood a quality essential to 

 life, some arrangement seems necessary to provide for the equal distribution 



* See Sabatier's Paper on this subject, in the Memoirs of the Academy of Sciences, for 

 1774. 



