458 Scientific Intelligence, Sfc. 



he concludes that the circulation in the imperfect foetus is carried on 

 by the action of the heart of its companion in utero. Some of these 

 authors argue that the blood proceeds from the placenta to the infant 

 by the veins, and is returned therefrom by the arteries ; others, that 

 it passes in the same course by the arteries, and is returned again by 

 the veins. Dr. Houston's observations go to establish, as a fact, that 

 the course of the blood in the cords and placentae of the two infants 

 is the same, but that in thin bodies it is different ; he considers that 

 while the blood enters both bodies at the same time by the umbilical 

 veins, it is transferred in the perfect infant to the aorta, through the 

 foramen ovale of the heart, and is thence distributed in the ordinary 

 manner ; whereas, in the imperfect infant, it is conducted all through 

 the body, without such transfer from vein to artery, and is thus 

 made to take an inverted course — the veins of the body assuming the 

 function of arteries, and, vice versa, the arteries that of veins. 



Dr. Houston considers that the presence of anastomoses between 

 the cords should rather lead to the inference, that the blood traverses 

 both placenta in the same course, than that it takes a direction in 

 the one different from that which it follows in the other. The 

 accidental effect, produced by the tumour in the cord of the foetus 

 examined by him, proves to demonstration, that, in that instance at 

 least, the blood entered the body by the veins, and returned by the 

 arteries ; and the absence of valves in the veins accommodated these 

 vessels for the reception of the blood, and for its transmission in a 

 retrograde direction through them. 



Dr. Houston suggested several good reasons in support of his 

 opinion, that the heart of the perfect foetus can exert very little 

 influence in propelling the blood into the vessels of the imperfect 

 one ; and considers that we must look to some other cause than a 

 vis a tergo for the accomplishment of this object. He is of opinion, 

 that the theory of " vital attractions and repulsions," though con- 

 veyed in terms which may be considered rather as expressive of the 

 facts than as explanatory of them, approaches more nearly to the 

 true one than any other which has been yet broached. 



Dr. Houston suggested arguments to prove that the placenta 

 possesses the same vital powers of attraction and repulsion as the 

 living foetus itself, and considers, that by such powers in mutual and 

 reciprocal operation, the blood may be carried to and fro along the 

 vessels of the cord without any farther mechanical influence what- 

 soever. 



Several drawings of the foetus were exhibited ; and the reading of 

 the paper led to a discussion, in which Dr. Prichard, Dr Carson 

 of Liverpool, Dr. O'Beirne of Dublin, Mr. Carpenter, and Dr. 

 Macartney took part. It was a conceded point, that the circulation 

 in the capillary vessels was independent of the action of the heart, 

 and it was stated, that there was no case on record, in which a 

 monster foetus existed without a perfect foetus ; nor had there been 

 ever any case discovered in which a single child had been found 

 without a heart. 



The third and last paper which occupied the attention of the 

 Section this day was one by R. Carmichael, Esq., on Tubercles. 



