SECRETOEY FUNCTIONS IN HUMAN PLACENTA 531 



tions, appear besides the lipoids. The vacuoles later on keep 

 increasing, while, on the contrary, the lipoids decrease in 

 quantity, and, moreover, of these vacuoles those which are 

 near one another unite into vacuoles of various sizes, and it 

 will be seen that the surface vacuoles of the latter ultimately 

 rupture and open upon the surface of the syncytium layer. 

 The process of secretion described above may be followed in 

 figures 5 to 7. Should this process continue and reach its 

 highest degree, such structural images as are shown in figure 

 8 would be probably brought about in the end ! What is pecu- 

 liar in these various stages when secretion is very high is that 

 plastosomes are detected. In the next place, what is shown 

 in figure 9 is taken, similarly to what is in figures 3 and 4, for 

 a comparatively early stage of secretion. However, the former 

 differs more or less from the latter in that already a somewhat 

 large quantity of vacuoles is noticeable in it. And, especially, 

 the vacuoles are chiefly arranged close to the Langhans' cells. 

 Figure 10 demonstrates on one side a large quantity of plasto- 

 somes and on the other a region where no plastosomes are to 

 to be found. This region presents, as mention has been made 

 already, a foamy structure which can be detected only by care- 

 ful attention. Figures 11 and 12 each clearly demonstrate plas- 

 tosomes, besides a large quantity of vacuoles and a small quan- 

 tity of lipoids. That is to say, in figures 9 to 12 it is always 

 easy to demonstrate plastosomes at different periods of secretion, 

 and therefore the various periods of secretion shown therein 

 may be differentiated from those given in figures 5 to 8, though 

 it is not easy to decide what correlations these stages have peri- 

 odically between themselves in point of secreting functions. 

 However, according to the various images described above, it 

 is deemed practicable in the main to arrive at the following 

 presumptions with respect to the phenomena of secretion of 

 this cell layer: 



a. At a time when function of secretion has not yet begun, 

 the chief ingredient of this layer is plastosomes, which are found 

 in a very large quantity; however, as the function begins, 

 they suddenly decrease in quantity, and at a certain period, 



