140 THE TOXINES PRODUCED BY BACTERIA. 



The two diseases in which they most probably exist are 

 diphtheria and tetanus. Apart from the evidence that a 

 digestive action has occurred, which the presence of albu- 

 moses in the body of an animal dead of these diseases affords, 

 the chief available evidence for the existence of ferments 

 lies in the fact, that the toxic products of the bacteria involved 

 lose their toxicity by exposure to a temperature which puts an 

 end to the diastatic activity of such an undoubted ferment 

 as that of the gastric juice. If a bouillon in which the B. 

 diphtherias has been growing be filtered germ-free it is toxic, 

 and reproduces the symptoms of the disease when injected 

 into animals. If such a bouillon be heated at 65 C. for 

 one hour, it is found to have lost much of its toxic effect. 

 There is evidence, however, that there remains a sub- 

 stance unaffected by the heat which, as we shall see later, 

 is also toxic. In the case of the B. tetani growing in arti- 

 ficial media similarly treated, all the toxicity is lost by 

 exposure at 65 C. ; but there is some evidence that in 

 tetanus, as it occurs in animals, there are bodies present in 

 the tissues which are not destroyed by heat, and which give 

 rise to the characteristic toxic effects which manifest them- 

 selves in the disease. In this disease there is a still further 

 fact which leads us to suppose that a ferment is concerned 

 in the toxic action, namely, the existence of a definite period 

 of incubation between the injection of the. toxic bodies and 

 the appearance of symptoms. This may be interpreted as 

 showing that after the introduction of say a filtered bouillon 

 culture, further chemical changes have to be set up in the 

 body before the direct effect in stimulating the nervous 

 system, which is the essential feature in the disease, is pro- 

 duced. Strychnine has probably a very similar effect to that 

 of the body which produces the spasms in tetanus, but if 

 strychnine be injected into an animal the effect is practically 

 immediate. In tetanus we have the further interesting fact 

 that, according to one set of observations, the substance exist- 

 ing in the tissues of a tetanic animal, to which reference has 

 been made as not being destroyed by heat, has such an 

 immediate effect without the intervention of an incubation 



