SECRETORY FUNCTIONS IN HUMAN PLACENTA 509 



should belong. Now, the result of my careful examination of 

 the appearance and distribution of these cells as compared with 

 the time of pregnancy has been that, in the material which was 

 taken a fortnight after conception, this being the earliest I have 

 on hand, the cellular ingredients of the decidua chiefly consist 

 of the small-type cells described above. In a little more advanced 

 stage (i.e., about 17 or 18 days after pregnancy) the decidua 

 shows also the appearance of a large quantity of the 'interme- 

 diate-type cells,' while in the few days following (i.e., about 22 

 or 23 days after pregnancy) with the decidua already of definite 

 growth, all kinds of cells, especially the large-type ones, can be 

 detected in comparatively large quantities. One month after 

 pregnancy the large and intermediate type cells appear as the 

 principal ingredients of the decidua, while on the contrary the 

 small-type cells retrograde gradually and are met with only in 

 the interstitial tissue. Such condition is maintained until the 

 end of the last month of pregnancy. In short, I conclude from 

 the histological and histogenetical point of view, that the various 

 kinds of cells described above all belong to one class, and con- 

 sequently it follows that the division of decidual cells into large 

 and small types, is faulty. In other words, the term ' small-type 

 decidual cells' applies only to the cells which are still at the 

 early stage of growth, while the * large-type cells ' are those in 

 the last stage of growth. The time taken in such growth is, 

 according to my observations at the earliest stage of pregnancy 

 at least, comparatively small, thus the small-type cells being 

 perfected into the 'definite large-type cells' in so short a time. 



The appearance of lipoid granules and vacuoles in the decid- 

 ual cells is most remarkable from the end of first month to the 

 second month of pregnancy, and they gradually decrease in the 

 months following, though very infrequently they can be demon- 

 strated even at the end of pregnancy. The plastosomes could 

 no longer be demonstrated in any of the decidual cells after the 

 seventh month of pregnancy. 



And, in the interstitium of the decidua, such extremely strange- 

 looking productions as are illustrated by figure 70 may some- 

 times be detected. They are stained dark and consist mostly 



