DEPARTMENT OF EMBRYOLOGY. Ill 



does not necessarily follow that their presence in this condition is 

 constant. Of the 61 specimens examined, the cells were very numerous 

 in 17, all of which showed hydatiform degeneration of the villi; 34 of 

 the 37 specimens which contained only a few were not identified as 

 hj^datiform, and therefore their presence can not be taken as indicative 

 of this condition, as has been maintained by some writers. On the 

 other hand, in not a single specimen devoid of Hofbauer cells could 

 evidence of hydatiform degeneration be found. They occurred more 

 frequently in pathological specimens than in those classed as normal, 

 which is what one might expect, in view of the fact that degenerative 

 changes of the stroma are more common in the former than in the 

 latter. 



The cells were likewise more abundant in cases of advanced hydati- 

 form degeneration. Although most of the pathological specimens 

 showed maceration as well as histological degeneration, it was in those 

 in which the latter condition was the more pronounced that the 

 greater number of Hofbauer cells were observed. Therefore, a plausi- 

 ble hypothesis v/ould be that whatever causes the transformation of 

 mesenchyme cells into Hofbauer cells is also the cause of hydatiform 

 degeneration. There appeared to be nothing characteristic in the 

 distribution of the cells in the material examined, except that they are 

 more numerous where the mesenchyme was degenerating. In some 

 instances they lay in gaps and spaces in the mesenchyme of the chorion, 

 which rendered them quite conspicuous. They also lay in areas of 

 the chorionic membrane which had undergone degeneration. In some 

 villi they were mxore numerous than the mesenchyme cells themselves, 

 while in others they were totally absent. All stages of degeneration 

 were noted, even to complete disappearance of the cell. Signet-ring 

 forms were conmion, and nuclei in all stages of exti-usion and degenera- 

 tion were found. The cell boundaries were often ragged, the nuclei 

 crenated and pycnotic, the cytoplasm granular, vacuolated, webbed, 

 or fenestrated, until nothing remained but a shadow form without a 

 trace of nucleus. The poorly preserved cells were larger than the better 

 preserved ones. The smaller cells were quite circular in outline, 

 stained evenly, and possessed a non-granular cytoplasm with a cen- 

 trally placed nucleus. Binucleated and multinucleated forms (fusion 

 products) were also noted. In these the nuclei were unequal and more 

 oval in outline than the nucleus of the typical Hofbauer cell. Not 

 infrequently transitional forms between the well-preserved mesen- 

 chyme and the vacuolated Hofbauer cell were observed, but as a rule 

 the two were readily distinguishable. 



In the early period of degeneration the cells have a decidedly granu- 

 lar cytoplasm; hence the confusion with plasma-cells and their earlier 

 designation as granular wandering cells. Although Hofbauer found 

 that in the fresh state they reacted to vital stains as did plasma-cells, 



