PATHOGENIC BACTERIA 



127 



of two or more blood-serum tubes (if these are not available, 

 the swab should be placed in a sterile test-tube or bottle, 

 and sent to the laboratory at once). The inoculated tubes 

 are placed in the incubator at 37 C., and examined in twelve 

 hours. If a growth is visible, a slide is made and stained with 

 Loffler's and Neisser's stain, and if bacilli are present, with 

 characteristic granules, the diagnosis of diphtheria is most 

 probable. If there are no clinical signs, the growth should be 





Fig. 65. Bacillus diphtherias, from a culture upon blood-serum (x 1000) 

 (Frankel and Pfeiifer). 



tested for toxicity by inoculating a guinea-pig; it should be 

 grown in alkaline sugar bouillon and tested in two days for 

 acid. The xerosis and Hoffman's bacilli are not pathogenic 

 for guinea-pigs and do not produce an acid reaction in sugar 

 media. 



Products. But it is not the mere presence of the bacillus that 

 gives rise to all trouble; certain products which they generate 

 get into the system and produce the severe constitutional symp- 

 toms. 



