266 A MANUAL OF BACTERIOLOGY 



where the disease has been conveyed from one individual 

 to another. 



The disease occurs in all grades of severity, from the 

 classical ones with wash-leather-like membrane and great 

 prostration, to those which present a mild tonsillitis or 

 angina. 



The bacteriological study of diphtheria was commenced 

 as long ago as 1882 by two German investigators, Klebs 

 and Loffler. Klebs especially investigated the pathological 

 histology, and ascribed the disease to small rod-shaped 

 organisms, which he observed in the membrane. It was 

 reserved for Loffler to place this observation of Klebs on 

 a firmer basis by the isolation and cultivation of the 

 bacillus from the membrane, and by the production of 

 certain phases of the disease by inoculation with the 

 isolated organism. The cause of diphtheria is, therefore, 

 this diphtheria bacillus, which, from its discoverers, is 

 frequently known as the Klebs-Loffler bacillus. 



The isolation of the specific organism was by no means 

 an easy matter, as a number of other species of bacteria 

 is frequently associated with it in the membrane, but was 

 accomplished by Loffler by the use of a special culture 

 medium now known as Loffler's blood-serum, which 

 consists of a mixture of blood-serum (ox serum was that 

 originally used) 3 parts and glucose bouillon 1 part, the 

 whole being coagulated (see p. 61). On this medium the 

 diphtheria bacillus grows and multiplies exceedingly well, 

 while the other organisms associated with it in the mem- 

 brane are to a large extent inhibited in their growth. By 

 rubbing a small piece of membrane from a case of 

 diphtheria over the surface of two or three tubes, or 

 of a plate of Loffler's serum, and incubating at 37 C. 

 for twenty to twenty-four hours, colonies of the diph- 

 theria bacillus will be found more or less isolated according 

 to the number of organisms present in the membrane, 



