PATHOGENIC ORGANISMS IN MOUTH CAVITY 403 



but at tolerably regular intervals along each rod are seen 

 alternating stained and unstained points. These rods may 

 be found singly, in groups of twos and threes, and sometimes 

 in clumps consisting of large numbers. When in twos or 

 threes it is not uncommon to find them describing an X or a 

 V in their mode of arrangment, or again they may be seen 

 lying parallel the one to the other. 



If contrast-stains are used, these rods will be detected 

 and recognized by their retaining the orginal color with 



FIG. 74 



v vvv it' 



' -fif* ^\ '&>': 



^ H ^ il C '"'" ' 

 "' -A /* / ^ t.' // 



Tuberculous sputum stained by Gabbett's method. Tubercle bacteria seen 

 as red rods; all else is stained blue. 



which they had been stained; whereas all other bacteria 

 in the preparation, as well as the tissue-cells which are in 

 the sputum, will take up the contrast-color. (Fig. 74.) 



This delicate, beaded rod is bacterium tuberculosis. The 

 lancet-shaped diplococcus with the capsule is bacterium pneu- 

 monia?. The cocci grouped in fours are sarcina tetragena. 



Inoculation Experiment. Inoculate into the subcutaneous 

 tissues of a guinea-pig one . of the small, white, caseous 

 masses, similar to that which has been examined micro- 



