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 

 (6) 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 cistema. 



in (6) 



a. The lymphatic epithelium, consisting of flat 

 cells, smaller than the peritoneal epithelium, 

 and with a very irregular sinuous outline. 



/3. The stomata ; very much as in (a). 



2. Treat with nitrate of silver' 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 suffioiently familiar with 

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



