78 STUDIES ON PATHOLOGIC OVA. 



One of the most interesting of these nodular embryos is No. 7886, received 

 from Dr. Anfin Egdahl, shown in figure 19. This is one of double-ovum twins in 

 which the chorionic vesicles were wholly distinct. The smaller of the twins is 

 but 2 mm. long, with a greatest diameter of about the same dimension. The mate, 

 on the contrary, is relatively a normally formed, somewhat stunted fetus, with a 

 crown-rump length of 17 mm. The abortus containing the chorionic vesicle with 

 the little nodule was somewhat larger than the one containing the fetus, although 

 both chorionic vesicles were covered by approximately the same quantity of 

 decidua. The dimensions of the chorionic vesicle belonging to the stunted embryo 

 were 60 by 45 by 40 mm., and those of the one containing the nodular embryo 

 65 by 55 by 40 mm. The greater size of the latter was due probably to the greater 

 distension of the chorionic membranes, which are thinner and possess only poorly 

 developed villi. The other vesicle, on the contrary, shows very definite placental 

 development, although one of its dimensions actually was smaller than the cor- 

 responding dimension of the chorionic vesicle belonging to the small nodule. 

 Both specimens evidently were very decidedly macerated when aborted. 



As shown in figure 20, this small nodule contains a large cavity lined by 

 epithelium, within which there is a large mass of cells, probably erythroblasts. 

 The exterior is covered by ectoderm, and the wall, which varies greatly in thick- 

 ness, is composed largely of mesenchyme containing blood-cells, particularly 

 erythroblasts, some of which lie in exceedingly thin- walled vessels. In the thickest 

 region a degenerate rudiment of the central nervous system and a mass of some- 

 what differentiated cells, which may be rudimentary myotomes, are indicated. 

 At one point on the periphery there is also a small, round knob, which looks like 

 the remnant of the cord, and at another point a small, denser, and more differen- 

 tiated protuberance which may be an early limb-bud. The caudal and cephalic 

 extremities can not be differentiated even with the microscope. 



The other fetus, shown in figure 21, which is to be described in group 6, is a 

 relatively well-formed specimen of 27 somites. It is somewhat atrophic and the 

 head adheres to the chest, but in development it is far in advance of its nodular 

 mate. Since the latter measures only 2 mm., it is evident that the respective 

 chorionic vesicle is much too large, and since it is wholly inconceivable that this 

 small nodule could ever have reached, even approximately, the stage of develop- 

 ment represented by its mate, it would seem that the accompanying chorionic 

 vesicle must have continued to grow some time after the death of the small embryo 

 which never reached any special differentiation. Furthermore, since there is no 

 very evident difference in the degree of the degeneration of the chorionic vesicles, 

 it is not unlikely that the one containing the minute nodule survived almost as 

 long as the other. The villi and membranes of both are non-vascular and the 

 stroma clear, suggesting hydatiform degeneration. 



The decidua is well preserved but infiltrated. However, a severe infection 

 could not cause a gradual inhibition of growth. A mild process, on the other 

 hand, can conceivably exert a general inhibition over a considerable period of 

 time, and thus possibly lead to all the changes, remarkable though they be, which 



