• CADUCA. 155 



in regard to the ovule, as the pleura is in relation to the lung, or as 

 the serous membrane of the pericardium is in respect to the heart. 



401. The external surface of the caduca is uneven and porous, 

 in contact with the interior of the womb, and invests the chorion as 

 far as to the circumference of the placenta, but is not prolonged 

 over the spongy surface of that body: to the former its adherence 

 is very slight and is effected only by means of mucous filaments 

 very easy to break, and which certainly are neither vessels nor nerves; 

 to the latter the union is much more intimate, and so much the 

 more so as the development of the ovum is more advanced. During 

 the first two months indeed it is pretty easy to extract the ovule from 

 that portion of the sac which constitutes its epichorion; while at a 

 later period, the numerous lilaments that habitually invest the germ 

 contract such solid adhesions with the reflected caduca, that it be- 

 comes more and more difficult to effect this separation without rup- 

 ture. 



403. The internal surface being moistened by a fluid, although 

 tuberculated, is nevertheless smooth, and lined with an extremely 

 delicate pellicle. After the fluid has disappeared and the reflected 

 portion has come to be in contact with the uterine layer, this sur- 

 face soon assumes the characters of the former. The liquid which 

 fills the cavity of the caduca, and keeps its two surfaces apart, is 

 sometimes quite limpid, but most commonly reddish, viscid, similar 

 to melted glass, or rather to white of eggs, and appears to be com- 

 posed of a large proportion of water, and of albumen, and gelatin. 



403. Circumference. At the place where the caduca turns back 

 so as to invest the ovum, it forms a circle, which at first exhibits the 

 form of a fold more or less regularly rounded, but which afterwards 

 is gradually transformed into a thin and sharp edge, and ends at last 

 by being more or less evidently continuous with the circumference 

 of the placenta. 



This is a point in the history of the connecting membrane on 

 which I most insisted in 1824, and is, notwithstanding, one on which 

 the greatest doubt has remained in the minds of observers. 



404. Hunter, Baillie, Wrisberg, Krummacher, Blumenbach, Stein, 

 MM. Lobstein, and Meckel, Beclard, &c., have indeed admitted the 

 two lamina? of the caducous membrane, but still persist in the belief 

 that the placenta does not fix itself to the womb until after having 

 passed through them. 



405. Chaussier and M. Duges, on the contrary, suppose that the. 

 uterus is at first merely filled with lymph or coagulable albumen; 

 that the little egg, on arriving from the ovary, dips into the midst of 

 this substance, and becomes covered with it; that the villi of the 



