PREPARATION AND STAINING OF TISSUE SECTIONS. 55 



larly sections selected from those cut with Jung's 

 microtome, may be transferred from the spirit to 

 absolute alcohol. The sections may be then stained 

 by any of the methods to be described. 



It is often advisable to employ some method 

 which will enable one to study the structure of the 

 tissue itself. In the same way with sections how- 

 ever prepared, one should always examine with a 

 low power (Zeiss' AA) first; this enables one to 

 recognise the tissue under examination in most 

 cases, and even to examine in many cases the topo- 

 graphical distribution of masses of bacteria. With 

 Zeiss' DD., Oc. 2, a power of about 250 diams., 

 very many bacteria can be distinguished, and with 

 the oil immersion lenses the minutest bacilli and 

 micrococci can be recognised, and the exact form 

 of individual bacteria accurately determined. As 

 Zeiss' microscopes are, like most good modern 

 instruments, provided with a triple nosepiece, there 

 is no loss of time in examining a preparation suc- 

 cessively with these different powers. 



Weigert's Method. A very useful method for 

 staining both the tissue and the bacteria is as 

 follows : Place the sections for from six to eighteen 

 hours in a one per cent, watery solution of any of 

 the basic-aniline dyes (methyl violet, gentian violet, 

 fuchsine, bismarck brown). To hasten the process 

 place the capsule containing the solution in the 

 incubator, or heat it to 45 C. A stronger solution 

 may also be employed, in which case the sections 



