SECRETORY FUNCTIONS IN HUMAN PLACENTA 501 



every^vhere (figs. 17 and 11). The vacuoles are extremely va- 

 ried in their size, quantity, and arrangement, and it is for this 

 reason that the structures of the cell bodies have so many special 

 features (figs. 18, 2, 3, andO) . In such vacuolar cells the rod-shaped 

 plastosomes are for the most part short in length, and they are 

 arranged either along the walls of the vacuoles or crowded together 

 in the protoplasm between the vacuoles; however, sometimes it 

 will be found that, as will be seen in figure 18, the vacuoles are 

 chiefly placed in order on the outskirts of the cells, and the 

 plastosomes accumulate in the center around the nucleus. Again, 

 it will be found that, as in figures 19 and 12, both the lipoid 

 granules and vacuoles of various sizes are simultaneously con- 

 tained in the cell bodies, in which case the plastosomes are com- 

 paratively small in number and are scattered here and there 

 in the protoplasm between the lipoid granules and vacuoles. 



In the largest cells (figs. 20 and 21) the cell bodies are in gen- 

 eral well filled with a great number of vacuoles of various sizes, 

 and consequently the protoplasm is noticeable only around the 

 nucleus and between the vacuoles. There are almost no lipoid 

 granules, which, when present, are small and are very few in 

 number; also the plastosomes decrease in quantity and are mostly 

 found around the nucleus. 



In short, the smaller-sized cells have in general only the 

 plastosomes as their material components, while the larger- 

 sized ones still contain a number of lipoid granules and vacuoles 

 and in the largest ones the cell bodies are commonly vacuolated 

 in a high degree and the protoplasm decreases considerably in 

 quantity, the plastosomes in general gradually decreasing in 

 number as the cells grow in size, though it sometimes happens 

 that it is very difficult to demonstrate them, regardless of the 

 size of the cell bodies. Of figures 22 to 26 it will be observed 

 that figure 22 shows the hpoid granules only, figure 23 chiefly the 

 small vacuoles and a few lipoid granules; in figure 24 it is 

 entirely the same as the former, however, with the distinctive 

 feature that the vacuoles are remarkably large and have lipoid 



