476 APPLICATION OF METHODS OF BACTERIOLOGY 



Do the diphtheria organisms disappear from the throat 

 with the disappearance of the membrane? How long do 

 they persist? When obtained from the throats of convales- 

 cents are they still pathogenic for guinea-pigs? 



Prepare a bouillon culture of virulent bacillus diphtheriae; 

 after it has been growing for thirty-six hours at 37°-38° C. 

 inoculate a guinea-pig subcutaneously with about 0.1 c.c. 

 of it. If the animal dies, note carefully the findings at 

 autopsy, especially the distribution of the bacilli. Now add 

 to this culture suflScient pure carbolic acid or trikresol to 

 kill all bacteria in it, and inject under the skin of another 

 guinea-pig varying amounts of the culture so treated, 

 beginning with 0.05 c.c. ; determine the minimum fatal dose, 

 and note in which respects the postmortem findings simulate 

 and in which they differ from those of the first animal. 

 Should any of the animals survive the injections of the 

 disinfected culture, note carefully their condition from day 

 to day, particularly any fluctuations in weight. When 

 they have quite recovered inoculate them with living, 

 virulent diphtheria organisms. Do the results correspond 

 with those obtained with guinea-pigs that have never been 

 treated at all? Explain the results. 



Diphtheria Antitoxin. — As stated above, the growth of 

 bacterium diphtheriae is accompanied by the elaboration 

 of a poison of remarkable toxicity that is accountable for 

 the constitutional symptoms and pathological lesions by 

 which the disease is characterized. If by appropriate 

 methods this poison (toxin) be separated from the bacteria 

 by which it was formed, it is capable, when injected into 

 susceptible animals, of causing death and practically all the 

 lesions that accompany the disease when due to the invasion 

 of the living bacteria. If, on the contrary, the dose of poison 



