407 



Monday^ 20</t February 1843. 



The Right Honourable Lord GREENOCK, Vice-President, 



in the Chair. 



The following communications were read : — 



1. On the Anatomy of the Human Placenta. By John 

 Goodsir, Esq., Conservator of the Museum of the Royal 

 College of Surgeons of Edinburgh. 



In the first section of the paper, the author described the parts 

 which enter into the structure of the villi of the placenta. The 

 villi are covered by a membrane with which anatomists are already 

 familiar. Within tliis membrane, and attached to its internal surface, 

 is a layer of cells, which has also been observed, and described as 

 epithelium. The cells composing this layer, Mr Goodsir denomi- 

 nated the external cells of the villus. The next structure is a mem- 

 brane not hitherto described, and named by the author the internal 

 membrane of the villus. The adhesion of this membrane to the 

 external cells is so slight, that it is generally seen at some distance . 

 from them, even in villi which have undergone no violence. With- 

 in the internal membrane of tlie villus, a set of very transparent 

 cells, hitherto undcscribed, is situated. These the author denomi- 

 nated the internal cells of the villus. The ultimate loops of the 

 umbilical capillaries are imbedded in this mass of cells, the cells and 

 vessels being closely bound up by the intei'nal membrane of the villus. 



The second section of the paper was devoted to the description of 

 the foetal portion of the organ. Mr Goodsir described the develop- 

 ment and structure of the tufts of the chorion. lie stated that the 

 <levelopment consists in the addition of cells to the extremity of each 

 villus of the tuft, these being supplied by a germinating mass, which 

 resembles the spongiole of the root-fibre of a plant. These tufts and 

 villi are entirely cellular, and are covered by a fine membrane. 

 Before the villi become vascular, the ovum derives nourishment from 

 the decidua, by the absorbing agency of the cells of the spongioles at 

 the extremities of the villi of its chorion. When bloodvessels have 

 formed in the villi, the cells, although less numerous, still remain, and 

 are believed by Mr Goodsu* to be the active absorbing agents in the 

 villi of the placenta. In the perfect placenta, the villi of the chorion 

 appear as the internal membrane, and the internal cells described in 

 the first part of the paper. These, along with the umbilical vessels, 

 constitute the faital portion of the placenta. 



