1894.] 3IICR0SC0PICAL JOURNAL 209 



acetic acid to ruu under, and, when the tissue is trans- 

 parent, add glycerine 



SEROUS MEMBRANES. 



Serous membranes present on the surface an endothe- 

 lial lining readily demonstrated by silver nitrate. It is 

 well to study the forms and relations of the cells in the 

 perforated and unperforated serous tissues. For the 

 former select the mesentery of the frog or of a young 

 rat ; for the latter the omentum of man or an adult 

 rat.... Cut the omentum rapidly without touching it 

 with the fingers. It is better, if not soiled by blood, to 

 place it at once in the silver solution ; otherwise wash 

 quickly in water. . . Use a weak silver solution and agi- 

 tate the membrane continuously while exposed to the 

 sun. Wash in a large quantity of water, partly dry as 

 described, stain with alum carmine, mount in balsam. 



The connective stroma of these tissues may be studied 

 thus : 



1 • — A piece of mesentery or of omentum is stained with 

 picro-carmine, washed to remove the yellow color, and 

 mounted in glycerine or in balsam. This will show the 

 cells and the connective fibres of the mesentery ; other 

 parts we reserve for future consideration. In these 

 preparations the cement between the connective fibres 

 may be shown, if Ranvier's method be used. The mem- 

 brane spread on glass is deeply stained with picro-car- 

 mine, treated with absolute alcohol, cleared by clove oil ; 

 make an incision with an exceedingly sharp razor, and 

 upon the edge of the cut, between the fibres will be seen 

 the pale rose-colored cementing substance. 



2. — To demonstrate the layers of the mesentery de- 

 scribed by Ranvier proceed thus. Introduce a slender 

 pipette near a vessel in the mesentery spread on a glass 

 plate. With the breath form a bladder ; cut away the 

 upper surface, the lower remaining adherent to the glass. 



