70 STUDIES ON PATHOLOGIC OVA. 



be detached completely from the chorion and bear only a small sessile embryo. 

 Whether or not the amnion can be recognized in the gross specimen depends not 

 alone upon age or upon whether it has fused with the chorion, but also upon the 

 condition of the other content of the chorionic vesicle. If the contained fluid 

 is a clear liquid of the character of the normal amniotic fluid, it is usually very 

 easy to detect the amnion, but if the fluid is exceedingly turbid from degeneration 

 products of the embryo and blood, the recognition of the amnion becomes much 

 more difficult, especially if the latter is partly disintegrated. This difficulty is 

 increased still further if the chorionic vesicle and the amnion are filled with a 

 flocculent magma or with a dense, blood-tinged coagulum. The ease of recognition 

 of the amnion depends also upon the degree of distension of the amnion itself. 

 Nevertheless, even if it be distended and splendidly preserved, but fused together 

 with the chorion, detection becomes possible only upon microscopic examination. 

 Since fusion of the fibrous layers of both chorion and amnion in these abortuses 

 is often so intimate that no line of demarcation can be detected between the two 

 membranes even by means of the microscope, the presence of the amniotic epithe- 

 lium remains the only criterion. 



Very often, too, the amnion is not preserved in its entirety, but is represented 

 by tags of membrane only. Whenever it is practically coextensive with, but not 

 adherent to, the chorion it is easily recognized, because it is distended and also 

 because of the presence of a narrow extra-amniotic or peri-amniotic space con- 

 taining a clear fluid and some strands of "magma." Rarely, the amnion has 

 collapsed completely and lies in folds forming small masses which it is not always 

 possible to distinguish from small cyemic or cordal remnants by inspection alone. 



Since, as His (1882) stated, the amnion is folded closely around embryos 

 1 cm. in length, remains only a few millimeters distant when an embryonic length 

 of 15 mm. is reached, and is coextensive with the chorionic cavity at a length of 

 about 25 mm., the ease of its recognition depends also upon the age of the particular 

 specimen, although its relative size is subject to considerable variation. More- 

 over, in the case of very young conceptuses, a further difficulty in identification 

 by the unaided eye is introduced through the presence of a thin, distended yolk-sac. 



Although the amnion is an exceedingly delicate membrane, it is undoubtedly 

 true, as stated by Miiller, that it may be preserved, for a considerable period after 

 the death of the embryo, in conceptuses of not altogether too early an age. Never- 

 theless, its destruction no doubt is much more rapid before it is fused with the 

 chorion. This is true particularly in case of intrachorionic infections which 

 quickly lead to disintegration of the amnion if they occur in the period before 

 fusion with the chorion has occurred ; after this period, on the contrary, the amniotic 

 epithelium, unless degenerate, seems to act as a formidable barrier to the passage 

 of the infection into the chorionic membrane, in the same manner as does the 

 chorionic epithelium in cases of extramural infection. If the chorionic vesicle is 

 infected previous to the fusion of the fetal membranes, the infection can easily 

 enter the stroma of both the amniotic and chorionic membranes and destroy them, 

 especially the amnion, in a relatively short time, thus leaving villi only. 



