jriLLER — CONTRIBUTIONS FROM ANATOMICAL LABORATORY. 243 



circular openings were seen at the center of four or five radially 

 disposed cells, PI. 15, figs. 7, 8, 9. At first they were thought 

 to be examples of openings plugged by lymph-corpuscles, as 

 ^mentioned by Ellenberger, but a careful study of such speci- 

 mens stained with nitrate of silver alone or in combination with 

 nuclear stains showed that such was not the case. In addition 

 to these forms still others, usually smaller than the above and 

 more uniform in size and shape, were, found. These instead of 

 resembling small openings had the appearance of dots; they 

 were often located at the intersection of intercellular lines or 

 on the cells themselves, PI. 14, fig. 5. 



Closely allied to these, but less frequent in occurrence and of 

 much greater significance, were small circular figures situated 

 at the intersection of intercellular lines. The peculiarity of 

 these figures was that the cell boundaries were visible either 

 above or beneath them, and could, by careful focusing, be traced 

 to a point of intersection.* These undoubtedly represent cases 

 in which, owing to a slight injury, the albuminous material in 

 the cement substance exuded in insufficient quantity to entirely 

 obscure the underlying boundary lines ; or, owing to the same 

 cause, the silver solution penetrated beneath the epithelial cells, 

 giving rise to a slight diffusion, PL 15, fig. 10. 



All figures which resembled mere discontinuities or clefts 

 were usually quite distinct and were bounded by lines very simi- 

 lar to the intercellular lines themselves. The more symmetrical 

 figures were largely outnumbered by the irregular ones. This 

 irregularity was not only one of size and shape, but also of dis- 

 tribution. 



Stretching of a membrane at the time of its removal had the 

 effect of producing discontinuities along the intercellular lines, 

 PI. 15, fig. 11. Schwartz (20) and Muscatello (14) have shown 

 that the differences in form of endothelial cells are dependent 

 upon the degree of contraction or distention of the organs which 

 they line; or in other words, that the shape of the cells is de- 



•The study of these figures Is greatly facilitated by the use of Abbe's stereo- 

 scopic cye-plece made by Zeiss of Jena. 



