SECRETORY FUNCTIONS IN HUMAN PLACENTA 529 



of the pancreas. It should none the less be stated that a ma- 

 jority of the facts enumerated above are merely preliminary. 

 Many future investigations must be looked forward to for a 

 further enlightenment of the secretion of these organs. 



In summarizing the histological knowledge we have at pres- 

 ent of the internal secretory cells described above, almost every 

 cell has, as its constant ingredients, plastosomes, lipoids, and 

 vacuoles. Now, the plastosomes are not regular either in their 

 shape or arrangement while the lipoids are not quite regu- 

 lar in their size, quantity, and color, but the smaller ones 

 bear a resemblance to granular plastosomes, while the 

 larger ones, agglutinating with one another, form larger 

 fatty droplets. The contents of the vacuoles probably consist 

 of watery, transparent droplets, which are separated from one 

 another by a very thin partition wall. The cell body should 

 present a more or less conspicuous alveolar structure in pro- 

 portion to the quantity of vacuoles contained. The quan- 

 titative correlation by which these formative ingredients are 

 connected to one another is not free from considerable varia- 

 tions. Occasionally only one or two of them exist to the abso- 

 lute exclusion of all the rest. It must be very often the case 

 that such phenomenon may be partly due to the difference in 

 the order of animals chosen for the subject of study and partly 

 to the functional relation of the cell concerned. In short, it 

 may be said that the various formative ingredients described 

 above as being seen in internal secretory cells constitute equally 

 necessary constant elements, the same as with external secre- 

 tory cells, as has been minutely dwelt upon previously. 

 Now, it is a marvelous sight indeed to compare histologically 

 these two kinds of cells, and to look at the perfect agreement, 

 not only in their structures, but also in the various histological 

 changes which follow their functions. On this score, I am con- 

 vinced that should there be a structure like the two kinds of 

 cells described above, besides the functional changes which 

 very nearly correspond to the above, it would be no error to 

 bring such cells under the category of glandular cells, regard- 

 less of the existence of a duct in them. And, if we look at the 



