196 PRACTICAL HISTOLOGY. 



CHAPTER XII. 



THE LUNGS. 



Preparations 1-2. The pulmonary pleura. 



The serous membrane which covers the surface of 

 the lungs as well as that which lines the wall of the 

 thorax is prepared hy the silver process. For the 

 pulmonary pleura, the lungs of a small animal that 

 has just been killed are to be removed entire, and 

 moderately distended with air through the windpipe, 

 the bronchi being then tied and the two lungs sepa- 

 rated. One is rinsed for a moment in distilled water, 

 and a little nitrate of silver solution is allowed to 

 flow over the surface; after the lapse of a minute 

 this is washed off again with distilled water, and 

 the organ is then immersed in a beaker of spirit and 

 exposed to the light. 



The surface of the other lung is to be firmly 

 brushed with a wet camel-hair pencil, to remove the 

 epithelioid cells of the surface before treating it with 

 silver solution. This may be suffered to remain a 

 minute or two longer in contact with it than with 

 the other lung; in other respects the treatment is 

 similar. Both preparations are left in the light until 

 they appear sufficiently stained, after which they are 

 to be placed on one side in the spirit for twenty-four 

 hours. They will then be sufficiently hard to render 

 it possible to shave off a thin slice from the surface. 

 The sections so made are to be placed in water, and 

 subsequently mounted in glycerine, with the outer 

 surface uppermost. 



Preparation 3. The costal pleura is to be pre- 

 pared in situ after the removal of the lungs and heart. 

 That of one side may be brushed, the other not; on 



