500 PROFESSOR TURNER ON THE GRAVID UTERUS AND 



sented by those anatomists, differs from that in the whale in the sinus-like 

 dilatation of the maternal blood-vessels, and in the much more intimate relation 

 of the tufts of foetal villi to those sinuses ; the closer approximation of the 

 foetal and maternal vascular systems being effected not only by the projection 

 of the tufts into the uterine sinuses, but by the absence, or at least the non- 

 recognition, of the epithelial investment of the villus. In the whale again, the 

 utricular glands have not, except perhaps at their mouths, lost their tubular 

 character, whilst the space between the two systems of cells in the human 

 placenta, which Goodsir regards as the cavity of a secreting follicle, has, if we 

 conceive it to be formed by a dilated uterine gland, altogether lost its tubular 

 form. 



It is generally admitted by physiologists that the placenta is an organ in 

 which a double function is performed — nutritive and respiratory. But there is 

 a difference of opinion as to how far these different functions are carried on by 

 the same structures in this single organ, or how far there may not be separate 

 structures set aside for the performance of each function. 



In the early stages of development of the ovum it has indeed been generally 

 admitted that the uterine glands, and the cells of the decidua reflexa and 

 serotina, where such exist, elaborate a material which, when absorbed by the 

 chorionic villi, is engaged in the nutrition of the embryo. But the idea has 

 been also entertained, that, after the new blood-vessels have been developed, 

 both in the villi of the chorion, and in the maternal portion of the placenta, 

 the uterine glands cease to perform their office, and the nutrition of the foetus 

 is effected by the passage of materials from the blood in the maternal 

 to that in the foetal blood-vessels. Some have held that the mode of passage 

 consists in the simple transudation of these materials through the walls of 

 the vessels from the maternal to the foetal vascular systems. Others again 

 have contended,' 7 ' that two sets of cells intervene between the two systems of 

 vessels, a uterine set (external cells of villus of Goodsir), which selects from 

 the maternal blood, and transmits the selected material into the villus; and a 

 chorionic set (internal cells of villus of Goodsir), which absorbs the material 

 transmitted prior to its passage into the foetal vascular system. 



Ercolani again has advocated a doctrine which, in some important parti- 

 culars, differs from those of his predecessors. He admits that the utricular 

 glands do furnish materials for the nutrition of the embryo, but only in the 

 early period of its development. And he strives to prove that, from a transfor- 

 mation and greatly increased growth of the uterine mucous membrane, and of 

 the sub-epithelial connective tissue, a new maternal glandular organ is formed, 

 which in its simplest form consists of secreting follicles, arranged side by side 

 and opening on the surface of the mucous membrane. In the human subject, 



* See the Memoirs of Professor Goodsir, and Drs Arthur Earre and W. 0. Priestley. 



