PLACENTA. 181 



471. One of its surfaces, the fatal, inner, smooth, vascular, 

 membranous. Sic, surface, is lined by the chorion, which adheres to 

 it, and by the amnios, which can always be separated from it by 

 merely peeling it off. In spreading upon it, the principal divisions 

 of ihe vessels of the cord form a very beautiful diverging net work. 



472. Its other, external or uterine surface, viewed in the womb 

 or upon an entire ovum, appears porous and fungus-like, but even; 

 neither cracks nor orifices of sinuses are seen; it only exhibits a 

 few salient points; the anhistous membrane does not cover it; a 

 simple pellicle lines it and covers its lobes. 



When the placenta is out of the womb, this surface is, on the 

 contrary, extremely uneven, lobes of various sizes are seen upon 

 it, and they are separated by fissures of greater or less depth; and 

 this happens because, in detaching and expelling the placenta, the 

 uterus, by doubling up, lacerates the thin inorganic pellicle which 

 concealed the intervals between its numerous cotyledons. 



I have had six opportunities of observing it in situ, and in none 

 of them could I discover either sinus or opening having the least 

 resemblance to what authors have described as such. It is proba- 

 ble that the observers have been deceived by some accidental open- 

 ings and excavations, such as are often met with, but which are 

 owing to the pellicle, before mentioned, being lacerated here and 

 there, and rendering it an easy matter to penetrate into the placental 

 fissures, as into so many excavations. 



At the full term of pregnancy, the circumference of the placenta 

 is continuous, without any decided line of demarcation, with the 

 double layer of the caducous membrane; and this is doubtless what 

 has led to the belief that the first mentioned part of the ovum is only 

 a thickened portion of the latter. 



473. Arantius, Hoboken, Warthon, Ruysch, Malpighi, and many 

 other old writers; Wrisberg, Reuss, MM. Lobslein, Meckel, &c., 

 among modern ones, have made many attempts to unveil the nature 

 or structure of the placenta. It might be supposed that in this 

 respect science has nothing more to desire; but in turning over the 

 most esteemed works on the subject, one's opinion is soon altered, 

 on perceiving that twenty different sentiments yet have their antago- 

 nists and defenders. 



Warthon, opposed by Arantius, was one of the first to say that 

 the placenta consists of two halves, one uterine or maternal, and the 

 other membranous or foetal. If Warthon, and those who have 

 adopted this division of the placenta have not taken the ovum of the 

 rodentia as their model, 1 am unable to discover in the human after- 



