286 BACTERIOLOGY. 



ute amount of the heart-blood. Apply the concave slide, 

 ringed with vaselin, and examine the hanging-drop with the 

 No. 7 objective. Study the characteristics of the anthrax 

 bacillus as it exists in the blood, and compare its size 

 with that of the blood-cell. Then label the slide and set 

 aside in the incubator for 24 hours. Examine the same on 

 the following 1 day and observe the formation of threads, of 

 sporogenic granules and possibly of spores. 



Owing to the rapid flow of blood, the anthrax bacillus 

 cannot give rise to long threads in the living body. In a 

 quiet liquid, as in the drop, the tendency to form threads is 

 favored. Stained, preparations can be made from this hang- 

 ing-drop culture. The cover-glass should be moved to one 

 side, just sufficiently to permit the forceps to pick it up. It 

 is then carefully raised, avoiding contact with the vaselin. 

 A portion of the drop culture, transferred to a droplet of 

 water on a clean slide, is spread out, dried, fixed and stained 

 in the usual way. 



Stained preparations. Place about 18 clean cover-glasses 

 on the small mounting board (7-J- X 20 cm.), or on the lid of 

 a slide-box. Pick up a piece of the spleen, kidney or liver 

 in a pair of forceps, and, while holding the cover-glass down 

 with another pair, lightly pass the cut surface of the 

 organ over the cover-glass. A very thin and even film 

 is desirable (see p. 280). In this way streak all the cover- 

 glasses; some with spleen, others with liver and the remain- 

 der with kidney tissue. Keep each set distinct. Then al- 

 low the specimens to dry in the air and fix cautiously by 

 passing once through the flame. Special care must be taken 

 not to over-heat, inasmuch as the anthrax bacillus in 

 that case will not stain readily. If, on subsequent trial, 

 a cover-glass is found to be fixed imperfectly the others 

 can be given an additional passage through the flame. 

 These cover-glasses are commonly known as streak prepar- 

 ations. 



