SECRETORY FUNCTIONS IN HUMAN PLACENTA 537 



body is remarkably large, the plastosomes decrease more or 

 less remarkably in quantity (figs. 28 and 34). The lipoid 

 granules, as mentioned above, do not appear in very large 

 numbers and, since they arise from very small granular bodies, it 

 is very difficult to clearly discriminate the latter from the ordinary 

 granular plastosomes (figs. 28, 29, 31, 36, and 37). Therefore, 

 in consideration of this fact and of the quantitative relations 

 between lipoids and plastosomes as described above, I am in- 

 clined to trace the mother-ground of the lipoid formation 

 in the plastosomes. Then, with regard to the vacuolar forma- 

 tion, we may infer from the conspicuous halos which often ap- 

 pear around the lipoids, or from a phenomenon in which the 

 lipoid often occupies the position of a nucleus within the vac- 

 uole (figs. 29, 34, and 36), as in the case of the epithelium of 

 villi as described above, that the vacuole should of necessity 

 be the liquefied product of a lipoid. In short, it may be stated 

 that the secreting phenomena of these cells, if looked at from 

 the histological view-point, are very simple indeed, and plas- 

 tosomes first bring forth lipoids, which latter in turn change 

 into vacuoles, and the reason why the lipoids are comparatively 

 scant is that the period of their appearance is exceedingly short. 

 And, while perhaps on one hand the contents of vacuoles, 

 viz., secretions, are gradually drained out of the cell body, on 

 the other the protoplasm and therefore the plastosomes bring 

 about a prospective new growth and multiplication, presum- 

 ably to provide for the materials of the next secretion, and in 

 this manner the afore-mentioned process, as simply it may be, 

 is repeated and follows in succession. At different times and 

 in different places, to make a secondary or tertiary secreting 

 process within a cell all the time, the cell develops and grows 

 in size gradually, and its structure therefore becomes extremely 

 complicated, and in this way I suppose that, even in one 

 and the same, cell body, the various periods of the phenomena 

 of secretion make a simultaneous appearance according to the 

 ingredients contained. This is a mere hypothesis of mine, 

 and yet since it was early refuted by M. Heidenhain that the 

 secretory granules of all kinds start their individual function 



