Journal of Applied Microscopy. 



493 



of large numbers of connective-tissue cells imbedded in delicate intercellular 

 material. These connective-tissue cells, as observed, were mostly large, irregular, 

 thin, flat cells, arranged flatwise with the surface, and occupying the middle 

 plane of the amnion. These cells were very irregular in form, giving off irregular 

 branches and processes, some broad, some fine and filamentary. The processes 

 of neighboring cells often were directly continuous with one another. The* 

 general outlines of the smaller of these cells were often rounded, of the larger 

 roughly polygonal, or altogether irregular. In size these cells ranged from 

 .025 to .090 or even .100 mm. in extreme dimensions, measuring between the 



Figure 2. Connective-tissue cells in the amnion, (x 500.) 



extremities of the processes (see Fig. 2). Mingled with these large, irregular 

 cells, were smaller cells of rounded or oval outline, ranging from about .008 to 

 .OIG mm. in diameter. Some of these cells had one or two fine processes, others 

 had none (Fig. 2). In one place, in one of the specimens, a capillary tube 

 was traced for a short distance in the connective-tissue layer, and in its vicinity 

 were a few scattered leucocytes. 



3. In places, the outer surface of the amnion 

 (that directed toward the chorion, and in this 

 case a definite free surface) was lined with a 

 single layer of small flat cells, apparently of an 

 endothelioid nature (see Fig. 3). These cells 

 were mostly hexagonal in shape (some pentagonal 

 and heptagonal), quite regular and uniform in 

 size and shape ; their angles were slightly rounded. 

 They were united to one another by their edges 

 or sides, which were straight, not sinuous. They were of small size, ranging 

 from about .0055 to .007 mm. in diameter. They did not form a complete lining 

 over the entire outer surface of the amnion, or at least the silver nitrate showed 

 their boundaries only in patches. No nuclei appeared in them ; if present they 

 did not take the nuclear stains employed. At one point three or four of the 

 cells seemed to exhibit relatively large single or double nuclei ; but these could 



Figure ". Endothelioid cells of 



outer surface of the amnion 



(and inner surface of the 



chorion), (x 1000.) 



