VACCINE-THERAPY 31 



Eosin and Neutral Red. 



These stains are most commonly used as contrast stains. 

 They are particularly clean stains, the process taking place 

 in half a minute to one minute. 



Capsule-Staining. 



Many bacteria are invested by capsules, and their 

 presence or absence assists in their identification. To stain 

 the capsule, dip the specimen in a mixture of equal parts of 

 carbol-fuchsin and distilled water for a few seconds, rinse 

 in water, stain for fifteen seconds in an aqueous solution of 

 gentian violet, wash in water, dry on filter-paper, and 

 mount. 



Flagella-Staining. 



Many organisms possess delicate plasmic outgrowths, 

 known as " flagella," and by reason of their delicate con- 

 struction thev are somewhat difficult to stain. To show 

 them to the best advantage, it is advisable to have a well- 

 diluted field of bacteria. Take a very small quantity of 

 young culture and place it on a slide. Dilute with water. 

 From this take a loopf ul and spread it rapidly on another 

 slide, and allow it to air dry; then fix by passing it 

 through the flame twice, taking care not to over-heat. 

 Various methods are adopted for staining flagella. 



Pitfield's Method is as follows : 



Take— 



(i.) Saturated solution of alum ... ... 10 c.c. 



Saturated alcoholic solution of gentian 



violet 1 c.c. 



Filter and bottle. 



(ii.) Tannic acid 1 gramme 



Distilled water 10 c.c. 



Filter and bottle. 



