ESSAYS ON BACTEEIOLQGY. 133 



minutes, according to the strength of the solution, it is 

 washed thoroughly in water, the clean side wiped dry, 

 and it is ready to examine. Under the microscope 

 the diplococci of gonorrhoea will he seen, in appear- 

 ance much like two coffeebeans, lying upon or in the 

 pus cells. They will he stained deep blue, while the 

 nuclei of the pus and epithelial cells are light blue. 

 The bacteria occur singly or in swarms, usually within 

 ' the cells, this being one of their striking character- 

 istics. The protoplasm of the cells may be counter- 

 stained with an acid anilin dye, an alcoholic solution 

 of eosin, thus making the picttire more striking and 

 the bacteria more conspicuous ; but this is of no great 

 importance. As thus carried out, the procedure is 

 sufficient for all ordinary clinical purposes. But 

 since there are other bacteria, more or less closely re- 

 sembling the gonococci, Avhich may be found in the 

 same localities, examinations requiring medico-legal 

 accuracy must be carried further. The gonococci are 

 decolorized under the Gram method of staining. 

 They occur characteristically in groups within the 

 cells. They do not grow upon the ordinary culture 

 media, such as potato, beef gelatin, or beef-agar^ 

 These tests having been applied the diagnosis he- 

 comes as nearly absolute as can be without culture 

 upon human blood serum and inociilations upon hu- 

 man beings. 



The bacteriological diagnosis of diphtheria has a 

 special importance as a measure for the protection of 



