XVIII.] THE LYMPHATIC SYSTEM. 201 



expose to light. After twenty-four hours, divide 

 it in two pieces, mount them in glycerine, one (a; 

 with the peritoneal surface uppermost, the other 

 (b) with the cisternal surface uppermost. Observe 



in (a) 



a. The peritoneal epithelium, consisting of large 

 flat cells with a slightly sinuous outline. 

 This is the usual character of the cells lining 

 serous cavities. 



0. Where several more or less triangular cells 

 seem to radiate from a common point, note 

 at their apices the small granular nucleated 

 cells surrounding the orifice or stoma lead- 

 ing from the peritoneum to the cisterna. 



in (6) 



a. The lymphatic epithelium, consisting of flat 

 cells, smaller than the peritoneal epithelium, 

 and with a very irregular sinuous outline. 



ft. The stomata ; very much as in (a). 



2. Treat with nitrate of silver 1 the peritoneal 

 surface of the diaphragm of a guinea-pig and 

 when stained mount a piece of it with the 

 peritoneal surface uppermost in Canada balsam. 

 Observe 



a. The tendon bundles of the diaphragm arrang- 

 ed in two layers. The spaces between the 



1 The Student should by this time be sufficiently familiar with 

 the method of using silver nitrate to require no further instructions. 



