SECRETORY FUNCTIONS IN HUMAN PLACENTA 527 



still more conspicuous toward the last period of pregnancy. Now 

 comparing this with what is observed in the Chiroptera 

 mentioned above, this period of lipoid secretion, so-called by Van 

 der Stricht, in the rabbit passes away in a comparatively short 

 time, and then slowly passes to the stage of the character- 

 istic vacuolar image; thus, it appears, it presents a certain 

 stage of secretion which is peculiar to itself. In short, it is in- 

 teresting to note that, in consideration of the changes in the 

 forms of secretion in external secretory cells, the structure, and 

 therefore the form in the secreting functions even in the same 

 luteal cells, differ according as the class of animals differs. 



That the interstitial cells of the ovary possess the same inter- 

 nally secreting functions as luteal cells, by reason of the close 

 resemblance which they bear to the latter in shape and structure, 

 has been universally acknowledged in the researches made, 

 in various kinds of animals, including the Rodentia, Chirop- 

 tera, and Carnivora, by Regaud and Policard ('01), Limon ('02, 

 '03), Fr. Cohn ('03), Regaud and Dubreuil ('06), Mulon ('11), 

 Athias ('11, '12), Van der Sticht ('12), Tsukaguchi ('12, '13), 

 Levi (' 13) . Now, according to these observers, the interstitial cells 

 also contain, as do the luteal cells and many other glandular 

 cells, important constituents, such as plastosomes, lipoid gran- 

 ules, and vacuoles. The vacuoles are especially very plentiful, 

 and they, for the most part, present a minute, delicate, and 

 peculiar vacuolar image, the protoplasm proper being barely 

 noticeable around the nucleus. The lipoid granules, as com- 

 pared with the luteal cells, are generally small in quantity and, 

 moverover, it is sometimes difficult to detect them. It is 

 customary for the lipoid granules more or less to increase in 

 quantity at the time of pregnancy. It has been equally 

 acknowledged by many observers that the lipoids of the inter- 

 stitial cells generally appear for a comparatively short period, 

 commonly fade away in color and change in quality speedily, 

 thus gradually passing into the vacuolar substance. And then, 

 many authors, except Levi, have proved and recognized, even 

 in this case, that plastosomes have a direct relation in the 

 formation of lipoids. 



