108 PRINCIPLES OF VETERINARY SURGERY 



solutions can be made from time to time. The aqueous 

 solutions have a tendency to decompose, especially the gen- 

 tian-violet ; the alcoholic keep indefinitely. 



If the smears have been made from blood or pus, where 

 histological elements also claim attention, first stain the 

 cellular protoplasm with a i% aqueous solution of eosin, 

 then use the methylene-blue as above described. This 

 method not only demonstrates the bacteria, but also differ- 

 entiates the various kinds of tissue-cells which may be pres- 

 ent. 



In case the urine is to be stained, some difficulty is usually 

 experienced in making the smear adhere to the slide, on ac- 

 count of the numerous salts and small amount of albumin 

 present. Let the urine settle first, or centrifuge it; then 

 wash the sediment with distilled water several times. The 

 sediment then forming is fairly free from the salts of the 

 urine and can usually be fixed to the glass with heat. If not, 

 a little albumin-fixative first applied to the glass will ensure 

 good fixation. 



Staining with gentian-violet is the same as with methyl- 

 ene-blue, except that the time of staining is shorter. This 

 dye is so penetrating that its tendency is to over-stain and 

 hence should be applied for two or three minutes only. A 

 fresh aqueous solution should be made up at time of using. 

 The old solutions in water are apt to be decomposed. All 

 the staphylococci and the glanders bacillus are better stained 

 with gentian-violet. 



Of the various staining-methods, three principal ones 

 will be described : the common method, the Ziehl-carbol- 

 fuchsin stain for tubercle bacilli, and Gram's method. 



The ordinary method of staining necessitates the use of 

 either methylene-blue or gentian-violet. Take one part of 

 the saturated alcoholic solution and nine parts of water. 



