208 



PHAGOCYTOSIS. OPSONINS AND BACTERIOTROPINS 



facilitated by scratching the edges of the slide with a glass cutter at the 

 point where it is desired to break it. The editor has broken as many as 

 twenty to thirty slides before a proper spreader was obtained. It pays 

 to do this, because upon the sharpness of the fracture and cleanliness of 

 the spreader depends the edge of the film, and secondarily the ease, 

 rapidity, and accuracy of the count. If the film be well made, it will 

 have a straight edge within which will be found practically all the leuco- 

 cytes, as they are larger than the red blood cells, and therefore dragged 

 to the end of the film. 



FIG. 27. Phagocytosis of tubercle bacilli. 



The preparations are fixed in a saturated solution of corrosive subli- 

 mate for two or three minutes, washed with water, and stained with 

 methylene blue or carbol-thionin (1/4 per cent, thinonin, and i per cent, 

 carbolic acid). Carbol thionin is preferable. It should be slightly diluted 

 and warmed before being poured upon the slide. Here it is allowed to 

 remain for several minutes, then washed off in water, and the slide dried 

 with filter-paper. The tubercle films are best fixed with formalin vapor, 

 stained with hot carbol or aniline fuchsin, decolorized in 2.5 per cent, of 

 H 2 SO4, treated with 4 per cent, acetic acid to dissolve the erythrocytes and 

 counter stained with 1/2 per cent, of methylene blue in 1/2 per cent, of 

 sodium carbonate. It is most important that tubercle films be carefully 

 stained because it is desirable to color every bacillus and yet not break up 

 the leucocytes (Fig. 27). 



With a i/i 2 inch oil immersion lens a minimum number of one hundred 



