SECRETORY FUNCTIONS IN HUMAN PLACENTA 503 



the fusion of the smaller vacuoles which are connected with 

 one another can be often proved in these stroma cells (fig. 38). 

 The plastosomes are mostly rod-shaped and lie scattered in the 

 protoplasm located between the vacuoles, though they some- 

 times crowd together in a somewhat larger number in certain 

 places (figs. 31, 32, 36, and 38). The lipoid granules are gener- 

 ally few in number and are found between the vacuoles, though at 

 times they are present within the small vacuoles (fig. 36). 

 The smallest of these lipoid granules, at a glance, bears a close 

 resemblance to the granular plastosomes; however, since they 

 are mostly very distinctly bordered, besides being stained darker, 

 it is easy to distinguish them from the former (figs. 36, 37, 

 and 31). Figure 34 looks somewhat different from the vari- 

 ous cells described above in that the cell is nearly spherical, 

 with a remarkably large nucleus within, besides a small number 

 of somewhat large vacuoles and plenty of lipoid granules in 

 the cell body. These granules have various sizes, but are in 

 general of middle size and a few of them are distinctly included 

 in the vacuoles. The plastosomes are extremely limited in num- 

 ber, and lie scattered in the protoplasm between the vacuoles. 

 It is very seldom that this kind of cells makes its appearance, 

 and a great majority of cells in the stroma, as are chiefly illus- 

 trated by figures 35 to 38, present a distinct vacuolar formation. 

 The plastosomes in the stroma cells have in general a very 

 strong staining power, and are therefore more easily detected 

 than other cell groups. It is, moreover, very rare that the cells 

 which have no plastosomes are met with, but in stroma cells the 

 lipoid granules seldom appear. The stroma cells appear distinctly 

 and are therefore most easily found during the period from the 

 second to sixth or seventh month of pregnancy. In the eighth 

 month, usually, numberless capillary blood vessels suddenly grow 

 and increase within the villi, so that it is impossible to examine 

 the cells. With every possible method it was difficult to detect 

 the cells, and, therefore, I am inclined to believe that the stroma 

 cells suddenly cease to exist at this stage of pregnancy. 



