Io6 PRACTICAL BACTERIOLOGY. 



sible on a good razor strop. It is equally important 

 to thoroughly harden the material to be out; only well 

 hardened substances can be cut in thin slices by hand 

 with a razor, and it is better to change the alcohol too 

 often than too seldom, in order to save subsequent 

 time and worry. The pieces of tissue may be gummed 

 on to pieces of cork as before, in order to have some- 

 thing to hold them by. When a section is to be cut, 

 the blade of the razor should be thoroughly moistened 

 with alcohol; a rapid slanting cut should then be 

 made. It is not a good plan to draw the razor back- 

 wards and forwards, as in that manner a jagged cut, as 

 if made by a saw, is produced. If the razor is pressed 

 vertically downwards, as a rule the tissue gets con- 

 siderably torn. These sections are further treated just 

 like those cut with the microtome. 



Many organisms are successfully stained in sections 

 with aqueous solutions only, such as the micrococci of 

 suppuration, whilst others, like the tubercle bacillus, 

 require even stronger staining solutions than LoflSer's 

 methylene blue. If it is not known whether the 

 tissues to be examined contain bacteria or no, it is 

 always best first to use Loffler's solution, and then if 

 that produces no effect, the more complicated staining 

 solutions described in the following chapter. 



According to Frey, blood may be included amongst 

 the tissues. If this is to be examined for bacteria, the 

 same methods are employed as those used for cover- 



