FILAMENTS OF THE PERITONEUM OF THE FROG. 49 



tained, parasites, crystals, and granular masses varying much 

 in size and form! Sometimes they are present in such numhers 

 that the vesicles are filled with them. In other cases a 

 part only of the interior is thus filled. 



From what has been above adduced it is, therefore, clear 

 that vesicular structures which are covered with cilia in a 

 certain stage — not, indeed, standing in direct relation to their 

 size — are developed in the same way that I have described in 

 the endothelial vesicles of the growing blood-vessels of the 

 embryo chick. (' SitzungsbericJite der Wiener K. Acadc^nie 

 d. Wissenschaften,'' Part for March, 1871.) 



As regards the nature of these vesicles, Ave must, in the 

 first place, pronounce them to be sinuses belonging to the 

 lymphatic vessels ; and, in the second place, Ave must say that 

 a portion of them are there present from the first, and become 

 covered with ciliated endothelium, it may be only under 

 pathological conditions. They may, also under pathological 

 conditions, contain parasites and other foreign bodies, xinother 

 portion of the vesicles is a new formation. 



What Avas said about the mesogastrium applies in a similar, 

 but more restricted sense, to the mesentery and to the septum 

 of the Cisterna lymphatica magna. In regard to the last 

 mentioned, I Avish further to remark, that the ciliated 

 endothelium knoAvn to Uogiel and SchAveigger-Seidel 

 (' Berichte a us dem physiologischen Institute zu Leipzig,'' 

 1866), which in the normal condition is to be found there 

 but sparingly, is in our case extensively distributed. Indeed, 

 in some tracts of great extent nothing but such can be 

 found. In some places it appears to be especially con- 

 nected Avith the stomata perforating the membrane made 

 known to^ us by the researches of these authors ; that 

 is to say, there is a thick Avail bordering and lining the 

 stomata, composed of endothelial cells bearing cilia, of cubical 

 shape, and in a state of proliferation. Let us remark here, 

 by the Avay only, that the description Avhich Dogiel and 

 SchAveic^orcr-Seidel have given of the structures bordering 

 the stomata and the canals Avhich traverse the membrane, 

 is, in the strictly normal condition, applicable to small parts 

 only; for they do not, in general, appear as discontinuities 

 between the flat endothelial cells of the peritoneal surface, on 

 the one side, and that of the cisterna lymphatica magna on 

 the other — into Avhich (discontinuities) the nuclei of the flat 

 endothelial cells, Avhich border them, project. They represent, 

 on the other hand, canals which are, in most cases, lined Avith 

 a special layer of small young cubical endothelial cells, 

 supporting cilia. 



VOL. XII. NEW SER. D 



