IMPORTANT PATHOGENIC BACTERIA 



III 



h) Stain with a saturated alcoholic (60 per cent) 

 solution of Griiber's eosin. 



i) Wash in water and blot. 



j) Clear and mount in balsam. 



Whichever method is appUed, the capsule should 

 appear as a lightly stained zone with a well-defined 

 outUne around the deeply stained cell. Capsules are 

 rarely demonstrable unless the organisms are culti- 

 vated in media rich in proteins, or are mixed with 

 serum previous to staining. 



Fig. 32 

 Mouse-Holder 



Special study. — ^Inoculation of a mouse with Str. 

 pneumoniae. 



1. Fasten the mouse in the holder (Fig. 32). 



2. Shave a place on the back above the tail. 



3. Wash with a solution of mercuric chlorid 

 (1:1,000), followed by alcohol. 



4. Inject 0.2 c.c. of a milk culture of Str. pneu- 

 moniae. 



5. When dead, perform an autopsy, and study the 

 lesions in the usual manner. 



6. Make cultures in milk and on slant agar from 

 the heart's blood or the spleen. 



7. Make a capsule stain from the heart's blood, 

 spleen, or other organs. 



