ON THE FATE OF THE HUMAN EMBRYO IN TUBAL PREGNANCY. 41 



that these plaques first arise within the magma fibrils of the ovum quite independ- 

 ently of the yolk sac. They grow in large masses, and with the destruction of the 

 ovum they are also spilled out into the tube lumen. The plaques are stratified, 

 forming layers that alternatingly take on the haematoxylin more intensely. When 

 cut transversely they resemble sections from an onion with a central nucleus, as 

 shown in plate 11, figure 4. The central point is generally intensely stained. When a 

 section is not cut transversely, the markings are more or less parallel, as shown in 

 the other portion of this same figure. Gradually, in the later development, these 

 plaques run together and form a spongy substance which stains intensely with 

 haematoxylin; the individual portions of the plaques, however, always show strati- 

 fication. Whether the last word has been said about granular magma it is difficult 

 to determine at present. It may be that only a portion of granular magma takes 

 on this stain, while the other portion does not. At any rate, it is established that the 

 reticular magma is formed of connective tissue fibrils which belong to the cells of the 

 chorionic wall. They are not elastic nor white fibrils, but practically identical with 

 the connective-tissue syncytium of the embryo and the chorion. The granular 

 magma is a peculiar substance composed of individual particles that are stratified 

 and stain intensely with hsematoxylin. 



DEGENERATION OF VILLI AND CHORION. 



We have repeatedly alluded to the various kinds of degeneration of villi and 

 their covering. It remains now to consider this question in a somewhat connected 

 way, as it is perfectly well known that villi are constantly undergoing degeneration 

 in normal development. The trophoblast becomes active in regions where it 

 receives nutrition, but when this nutrition is cut off it degenerates. In general, 

 the stroma of the villi responds in a similar way. After the trophoblast has become 

 necrotic, the body of the villus degenerates. When the trophoblast is active the 

 villi sprout and grow. We have a condition which is frequently seen in organic 

 nature and is well illustrated by the growth of the vine over the lattice- work; the 

 favored twigs grow and the rest fail. 



Trophoblast. When the larger villi are detached from the decidua in normal 

 development, they contract and form small nodules composed mostly of trophoblast 

 cells. These soon become white and necrotic, and can readily be observed with the 

 naked eye, as they measure about 1 mm. in diameter. In the course of time these 

 necrotic masses are invaded by new trophoblast cells, usually from neighboring 

 villi, and we have here an interesting phenomenon, the dead cells being eaten up 

 by the living. This may be seen in the normally developed ovum. A modification 

 of this process is observed at the point of juncture of the villi with the decidua. 

 Here also the necrotic masses, often spoken of as fibrinoid substance, are invaded 

 by new trophoblast cells, giving in transverse section the appearance of cartilage. 

 Fibrinoid substance is probably derived from a variety of sources, trophoblast, 

 epithelial cells, blood, and also fibrin. This is well shown in plate 2, figure 3, which is 

 from an ovum containing a normal embryo. The figure pictures the tips of the 



