186 APPENDAGES OF THE FCETUS. 



have been mistaken myself? Time and additional facts alone can 

 resolve this question, which I leave for the curious. 



Development. Anatomists have all treated of the formation of 

 the placenta; but only a few of them have studied it methodically, 

 even since Hunter made us better acquainted with the nature of the 

 decidua. It has been said, that when the ovule reaches the womb 

 there appear on its external surface certain branching villi which 

 penetrate through the anhistous membrane so as to come in con- 

 tact with the womb, and that the placenta is formed in this man- 

 ner; that these villi, at first regularly disseminated over the entire 

 surface of the ovule, soon begin to collect in groups and to assemble 

 together at one point, but becomes every where else smooth and 

 transparent; that the placenta cannot be distinguished until after the 

 end of the second month; that it then covers two-thirds or at least 

 one half of the ovum, and that its proportional breadth becomes less 

 and less as the pregnancy advances, &;c. 



481. The following is an account of what we do observe: after 

 gliding betwixt the inner surface of the womb and the caduca, and 

 becoming attached to the organ destined to contain it until the end 

 of pregnancy, one half of the villous vesicle is necessarily in contact 

 with it, while the other half pushes away the anhistous membrane. 

 From this moment one disc of the ovule is left in direct contact 

 with the living surface, without the interposition of the deciduous 

 membrane, and here the placenta is developed: this is the only spot in 

 the womb at which the germ can take up the principles of its nu- 

 trition, resembling in this respect a vegetable inclosed in a vessel, 

 and having no communication with the earth save by a small open- 

 ing at the bottom. 



It is then evident that the placenta in some sort begins to grow 

 as soon as 1,he ovule reaches the uterus, and not merely afier the 

 two first months of gestation; that the relative dimensions of it and 

 the whole ovum are about the same from first to last; and that 

 it is consequently incorrect to say that it covers more than one 

 half of the chorion at the second month, but at a later period only 

 a third, a fourth, &c. I have reason to believe that it constantly 

 augments in the same proportion as the suiface of the womb with 

 which it is in immediate contact; so that its width at birth depends 

 upon the size of the uterus or the dimensions of the point left ex- 

 posed by the decidua at the commencement of gestation. 



482, It is well known that the placenta may be attached either 

 to the fundus, the front, the back or sides, and sometimes to the 

 neck of the uterus; but hitherto the cause of these anomalies has 

 not often been inquired into. Those who say that it attaches itself 



