ON THE FATE OF THE HUMAN EMBRYO IN TUBAL PREGNANCY. 43 



the section is mottled, that is, when it contains both old and fresh blood; the latter 

 nearly always encircles the villi. This would indicate that when the ovum is lodged 

 in a clot fresh blood can reach the chorion only along the line of its villi. As this 

 small layer encircling the villi contains no fibrin and as the small mass of blood 

 which enters the intervillous spaces has not coagulated, it seems allowable to 

 conclude that the trophoblast produces a ferment which prevents coagulation of 

 blood. In fact, this idea seems to be acceptable to all authors who have written 

 upon this subject. So when we have relatively large ova covered with tufts of 

 villi, the fresh blood produces large patches around them, while the older blood, 

 somewhat distant, is forming the well-organized clot. This condition is shown in 

 plate 8, figure 4; plate 9, figure 3; and plate 10, figure 1. It can also be demon- 

 strated in practically any distended tube containing a pathological embryo. On a 

 smaller scale the condition is well shown in plate 7, figure 2. 



Nevertheless, we frequently find large independent clots in a normal implanta- 

 tion, both within the tube and uterus, showing that the anti-clotting property of 

 the trophoblast does not extend far beyond its own border. It prevents clotting 

 of the blood in its immediate neighborhood. When the trophoblast taps the blood 

 vessels the escaping blood does not coagulate until it has formed a larger mass 

 within the intervillous spaces, but it then forms a large rigid clot. 



The most unusual kind of degeneration of villi is fibrous. We recognize in 

 this variety an advanced stage of development; that is, a fibrous degeneration of a 

 young villus makes the stroma appear like that of an older one. Undoubtedly 

 this process may take place very rapidly. This statement is adduced from a condi- 

 tion found in specimen No. 874. Here the ovum was divided, part of it lying near 

 the point of implantation in the uterine end of the tube and the other part some- 

 what distant in the fimbriated end. In the second portion practically all of the 

 villi have undergone marked fibrous degeneration. Three stages of this process 

 are shown in plate 2, figures 1 and 2, and plate 3, figure 1. The main wall of the 

 chorion of the specimen No. 694 appears to be quite normal. The mesenchyme is 

 delicate and transparent, with active strands reaching into the cavity of the ovum; 

 but the chorion is well encircled by a clot, which in turn is perforated by a number 

 of villi containing an active trophoblast upon their tips. Many of the villi have 

 undergone mucoid degeneration and there is much nuclear dust. A few, however, 

 are undergoing fibrous degeneration, as illustrated by this figure, which shows a 

 villus lying free within the fresh clot. It is also surrounded with numerous leu- 

 cocytes not shown in the picture. Plate 2, figure 2, is taken from a specimen 

 is which only a few villi are found within the tube lumen. Most of them are more 

 fibrous than the one from which the figure was drawn. Here the stroma is denser 

 than in the previous specimen, and there is no regular trophoblast lying upon the 

 villus. At one point it forms a necrotic fibrinoid mass. It is interesting to note 

 that where a villus comes in contact with the tube wall it also is undergoing a hya- 

 line degeneration. The extent of this process is shown in the coloring in the figure. 



Plate 3, figure 1, shows a most advanced stage of fibrous degeneration. The 

 ovum has reduced itself to a single fibrous strand and the crelom is obliterated. 



