BACTERIOLOGICAL DIAGNOSIS 271 



One or two important inferences may be drawn from the result of micro- 

 scopical examination, when positive. As a rule, the finding of numerous 

 bacilli of the " long " type denotes a severe infection, and a similar inference 

 may be drawn if streptococci are found associated with the specific micro- 

 organism. On the other hand the presence of the Brisou coccus generally 

 indicates a mild infection. 



2. Sections. Harden in alcohol, embed in paraffin and cut sections per- 

 pendicularly to the surface of the membrane. For staining, Gram's method 

 with double counterstain gives very good preparations. 



', ,?*, ' 



> \ 



*+ ** . I, 



FIG. 171. Section of tracheal membrane from a case of diphtheria, showing 

 diphtheria bacilli (Eosin and methylene blue), oc. 2 ; obj. T l 5 th, Zeiss. 



From an histological study of diphtheria membranes it can be shown that they 

 are made up of three layers : the deepest layer that next the body surface 

 (mucous membrane or skin) consists of a network of fibrin enclosing epithelial 

 cells and leucocytes : the middle layer is made up of granular fibrin with but few 

 cellular elements, while the most superficial layer consists almost entirely of micro- 

 organisms ; the bacilli, many of which are swollen at the ends, are arranged in 

 masses parallel to one another, and side by side with the diphtheria bacillus are 

 found the organisms associated with it. 



B. Cultures. Cultures should be sown on coagulated blood serum. If 

 however this medium be not available, white of egg may be used instead. 



The various serum media of Lcefner, Tochtermann, Joos, etc., give no better 

 results than coagulated blood serum while they have the disadvantage of needlessly 

 complicating the technique. [Many observers, however, state that Lceffler's serum 

 (p. 52) is by far the best medium for the cultivation of the diphtheria bacillus. 



[Lorrain Smith prepared a transparent serum medium by adding O'l per cent, to 

 0*15 per cent, of caustic soda to ox serum and heating the mixture at 120 C. 



[Cobbett added about 1 c.c. of a 10 per cent, solution of caustic soda to 100 c.c. of 

 ox or horse serum and after thoroughly mixing added 1 per cent, of glucose and 

 sterilized at a temperature of 87 C. ] 



[Coplans has recently introduced the following medium for the routine recognition 

 of the diphtheria bacillus : 



Sheep's serum, 75 parts. 



Broth, - 25 



Glucose, 0'5 per cent. 



KCNS., 1 



CaCl 2 , 1 



1 per cent, aqueous solution of neutral red, - - - 0*25 



