HOPBAUER CELLS. 307 



the mesenchyme was degenerating. Sometimes a considerable number were con- 

 tained in one villus and none in an adjacent one. As many as 12 might lie in one 

 field and none in the next. In rare instances there was a solid mass of them, 

 as shown at one side of the villus in figure 128 (plate 12, Chap. VIII), but 

 usually they were scattered about at random, although groups were also seen. 

 The better-preserved cells were small, the poorer-preserved larger, the size varying 

 from 8.5 n to 30 n. The smaller cells were usually quite circular in outline, stained 

 evenly, and possessed a non-granular cytoplasm with a nucleus quite centrally 

 located. Binucleate cells, as described by Grosser, were not uncommon, and 

 multinucleated cells fusion products were also found. The nuclei of the latter 

 were frequently more unequal in size, and usually also more oval in outline, than 

 the single nucleus of the typical Hofbauer cell. Measurements of some of the 

 largest cells, made with a micrometer caliper, gave the following results: 25.5 

 by 20.4, 30.4 by 27.5, 18.0 by 12.0, 21.5 by 25.5, 18.0 by 14.0 ?. These figures 

 are considerably above those given by Hofbauer, whose estimation of a size of 

 10.5 fj. to 12.5 fj. applies to the average-sized cell. 



However, the size of the cells varied from specimen to specimen of chorionic 

 vesicle, but not nearly so much as their state of preservation. This, no doubt, is 

 partly due to the varying state of preservation of the villi themselves. 



In outline they varied from irregular to circular, as stated by Hofbauer, and 

 as represented by Minot (1911) in his series showing progressive degeneration. 

 Although it was easy to distinguish the vacuolated Hofbauer cell from the well- 

 preserved mesenchyme cell with cylindrical nucleus and many processes, speci- 

 mens which represent transition forms, as stated by Marchand, and as shown in 

 figures 235 to 237, were quite common. The latter generally were oval or slightly 

 irregularly formed cells with a number of short processes, which latter, as well as 

 the character of the nuclei and the form of the cell itself, certainly suggested a 

 mesenchymal origin. They were also most numerous in villi, the stroma of which 

 had become glassy, vacuolated, or fenestrated. In these the reciprocal numerical 

 relationship between the Hofbauer and the mesenchyme cells was often especially 

 evident. In certain areas in which almost no mesenchyme cells remained intact, 

 numerous Hofbauer cells occurred in all stages of degeneration. In other portions 

 of the chorionic membrane or of the villi, mesenchyme cells with processes in all 

 stages of retraction were also clearly outlined in the homogeneous ground sub- 

 stance. Such evidences naturally remind one of Hofbauer's statement that Mar- 

 chand called his attention to the fact that these cells were mesenchyme cells, a 

 conclusion which Hofbauer accepted. My implication, however, is not that 

 degeneration of the mesenchj^me or of individual mesenchyme cells can proceed 

 only through a Hofbauer stage, but that, especially in the chorionic villi, a form 

 of degeneration of the mesenchyme seems to occur which gives rise to this peculiar 

 cell-form, the degenerate character of which rightly impressed Minot. This rela- 

 tionship also attracted the attention of Mall (1915), who represented degenerating 

 villi and stated: 



