SYSTEMATIC AND DESCRIPTIVE. 227 



followed. Guinea-pigs proved to be susceptible 

 in some cases, but thirty- two mice, after injection 

 of a cultivation diffused in sterilised water into the 

 lungs, died without exception. The lungs were 

 red and solid, and contained the cocci, which were 

 also present in the blood, and in enormous numbers 

 in the pleural exudation. Inhalation experiments 

 by spraying the cocci diffused in water into mouse 

 cages succeeded in producing pneurnonia and 

 pleurisy in three out of ten mice. The nail-shaped 

 cultivation is not always produced, nor are these 

 conclusions accepted by all investigators.* 



METHODS OF STAINING THE BACTERIA OF 

 PNEUMONIA. 



(Pneumonie- Coccen, Fried lander.) 



Cover-glass-preparations (p. 48) of pneumonic sputum 

 or exudation may be treated as follows : 



(a) Stain by the method of Gram, and after-stain with 

 eosin (p. 59). 



(b) Treat with acetic acid, then stain with gentian-violet 

 or bismarck-brown. Examine in distilled water, or dry and 

 preserve in Canada balsam. 



(c) Float them on weak solutions of the aniline dyes 

 twenty-four hours ; differentiation between coccus and 

 capsule is thus obtained. 



(//) Stain with osmic acid; the contour of the capsules 

 is brought out. 



Sections of pneumonic lung should be stained by 



(a) Method of Gram. 



(b) Method of Friedldnder. This method is employed 

 to demonstrate the capsules in tissue sections. It consists 



* Klein, Micro-organisms and Disease. 1885. 



