CORYNEBACTERIUM DIPHTHERIA. 399 



ture x consists in the toxicity of the filtrate of a culture of 

 a certain age. 



In the interest of rapid work, Escherich recommends 

 for the estimation of virulence a statement of the quan- 

 tity, expressed in percentage of the body-weight, of feebly 

 alkaline twenty-four hours' bouillon culture which just 

 suffices, when introduced subcutaneously, to kill a guinea- 

 pig with acute diphtheria. With 1.5 c.c = 0.5% of the 

 body-weight, Escherich never obtained a negative result; 

 with his most virulent cultures, 0.1 to 0.3 c.c. — i.e., 

 about 0.05% — sufficed. Aronsohn has cultivated still 

 more virulent bacteria, of which 0.02% to 0.025% of 

 bouillon filtrate was certainly fatal. 



Also, for infection experiments 2 the best animal for use 

 is the guinea-pig. Death is caused by 0.02 c.c. of a viru- 

 lent culture in two days; by 0.01 c.c. in three or four days. 

 Usually 0.5 to 1 c.c. is injected. About twenty-four hours 

 after the subcutaneous injection the following picture 

 develops: The animal is weak, without appetite, the hair 

 bristling, snout cold and bluish, respiration very harsh. 

 There is infiltration at the place of injection, and often 

 also for some distance beyond. Death occurs after twenty- 

 four to sixty hours. There may be entire absence of 

 special symptoms of disease except loss of weight. 



Autopsy : At the point of injection a whitish infiltration 

 surrounded by hemorrhagic edema, and, in chronic cases, 

 callosities discolored by hemorrhage. The most important 

 changes in the internal organs are: Suprarenal capsules 

 h} T peremic; exudate into pleurae, often also into pericar- 

 dium; spleen unchanged ; often parenchymatous nephritis 

 and myocarditis. The upper part of the intestine is red- 

 dened. Escherich observed cultures with which the in- 

 oculation was never followed by pleural exudate. In 



1 See De Martini (C. B. xxiv, 420) regarding occasional discrepan- 

 cies of toxin formation and infectiousness in the same culture. 



2 In order to recognize diphtheria bacilli of doubtful and very 

 slight virulence as still virulent, Trumpp injects them simultaneously 

 with a sublethal dose of diphtheria toxin. The animal must die, in 

 contrast to a control animal, and with reinoculation of definite quan- 

 tities into new animals the virulence must constantly increase, so that 

 finally the inoculated animals die without any additional diphtheria 

 toxin (C. B. XX, 721). 



