52 FRANKLIN P. MALL 



tegratioii of the ovum, leaving only a few villi. Having made 

 numerous efforts to classify these s]ieeimens, I have finally 

 lesolved them into seven groups which I shall consider in their 

 reverse numerical order. 



The seventh group, shown in figure 7, is composed mostly of 

 larger specimens which are either dried up and deformed, or 

 macerated and soft. These, of course, apparently merge into 

 each other, and for this reason we have had to consider them as 

 a single group. We hope, however, in the course of time to be 

 able to subdivide them, for it is well known that fetus compres- 

 sus is extremely rare in pigs and other lower animals, w^hile 

 edematous and macerated embryos are quite common. It 

 appears that the type of fetus in this group develops as a normal 

 embryo during the first portion of pregnancy, and then dies 

 slowly, either undergoing maceration, or being transformed into 

 a fetus compressus. In the latter the cord is long, thin and 

 greatly twisted The structures of the embryo show that there 

 has been a slow^ tissue growth w^hich has not been sufficiently 

 rapid to allow the normal development of the extremities. In- 

 stead the hands and feet are club-shaped, and in several in- 

 stances there are adhesions beween the extremities and the 

 body We also find very pronounced and quite characteristic 

 changes in the placenta of the fetus compressus, there being 

 bcw^een the villi lage masses of chromatin substance presenting 

 much the same picture as the photograph of a comet, a central 

 nucleus with scattered granules extending from it. Generally 

 in our notes we speak of this substance as nuclear dust. 



The sixth group of specimens we term stunted (fig. 6). The 

 form of the embryo is easily recognized, but the head is atrophic 

 as are also usually the extremities. At the time of the abortion 

 the tissues are quite transparent, giving every appearance of 

 a living embryo, but with, increasing knowledge concerning 

 tissue cultures and growing isolated cells, we can see in speci- 

 mens of this sort an active but circumscribed tissue culture of 

 a clump of differentiated tissues. In other words we have a 

 tissue culture of the entire embryo, w^hich on account of faulty 

 or arrested circulation, growls in an irregular manner. Changes 



