106 VETERINARY BACTERIOLOGY 



2. Wash and blot with filter-paper. 



3. Stain with hot anilin-gentian-violet or carbol-fuchsin over 

 a water-bath for five minutes. 



4. Wash and examine. 



Gram's Staining Method. This method was first used to 

 demonstrate bacteria in tissues, the bacteria retaining and the tis- 

 sues losing the stain. It was later found that not all bacteria 

 could be stained by this method, and it has in consequence come 

 into general use for separating bacteria into two groups, termed 

 respectively gram-positive and gram-negative, the former retain- 

 ing the stain and the latter losing it. 



1. Prepare film, dry, and fix. 



2. Stain one and one-half minutes in anilin-gentian-violet. 



3. Treat with Gram's iodin solution one and one-half minutes. 



lodin 1 gm. 



Potassium iodid '. 2 gm. 



Water 300 c.c. 



4. Decolorize with 95 per cent, alcohol for five minutes. 



5. Wash, dry, and mount. 



Blood and Protozoan Stains. Many special stains have been 

 devised for demonstrating the blood elements and protozoa in 

 the blood and in tissues. The chief of these are the Romanowsky 

 and Giemsa, each with numerous modifications. These may most 

 profitably be purchased ready for use from a reliable dealer. 

 The methods of use will be discussed in connection with specific 

 microorganisms . 



