350 Veranus Alva Moore 



on the cover-glasses is heated to a temperature of about 

 40-45° C. and the preparations placed at once in the incubator, 

 the bacteria are more evenly distributed. 



After the preparations have dried the bacteria are fixed to 

 the cover-glass by heat. This can be accomplished either by 

 passing them, film upward, twice through the flame of a spirit 

 lamp or Bun.sen burner, or by heating them from i20°-i40° C. 

 for from five to ten minutes in a hot air chamber. The latter 

 is to be recommended when facilities will permit. 



The applicatio7i of the mordant and staining fluid : In ap- 

 plying the mordant the preparations are completely im- 

 mersed in the fluid. In place of a watch glass as formerly 

 recommended, I have used a large (one inch) test tube for 

 this purpose. From three to four c. c. of the mordant is placed 

 in the tube into which the cooled, heated cover-glass prepara- 

 tion is dropped. The tube is held over a flame until steam is 

 given off when it is removed. The mordant should be fre- 

 quently agitated by gently shaking the tube. After from five 

 to ten minutes the cover-glass is removed by the use of a wire 

 hook on the end of a glass rod and with a pair of fine forceps. 

 The cover is thoroughly rinsed in clean water, or better, in a 

 stream from a spigot or wash bottle. If there is a grayish 

 film on the preparation it can usually be removed by rinsing it 

 in strong alcohol and again in water. 



The staining fluid is applied in a test tube in preciselj^ the 

 same manner as the mordant. It is allowed to act for from 

 one to three minutes. 



The mordant should be fresh and al ways 7?//<?rd?(/ before it is 

 used. The carbol fuchsin can be kept in stock solution for a 

 considerable time. The success of the operation depends 

 very largely upon the care with which it is performed. The 

 method as described gives excellent results with the three 

 species of bacteria under consideration, and it has been suc- 

 cessfully applied to a few others.* 



*In the application of the method to other bacteria whose flagella 

 will not stain by the use of a neutral solution, trials must be made with 

 acid and alkaline mordants, and possibly with mordants containing 

 different quantities of tannic acid, until a successful combination is 

 found. 



