8 TOXINES AND ANTITOXINES. 



there may be very energetic growth of bacteria, whilst the 

 culture medium is absolutely non-toxic (LUBOWSKI 1 ). 



Moreover, in the case of vegetable and animal toxines, the 

 production of poison depends on manifold physiological condi- 

 tions, such as age, nutrition, &c., with which points we will deal 

 more fully in the special part. 



On the other hand, it is beyond question that certain agencies 

 increase the growth, and eventually the virulence, of the bacteria, 

 but reduce the yield of toxines. This is due to the fact that they 

 partially destroy the toxine already formed. Even when agencies 

 of this kind increase the production of toxine simultaneously with 

 the vigour of growth of the bacteria, yet, if employed too freely, 

 the amount of toxine destroyed exceeds that of new-formed 

 toxine, so that the final result is a diminished yield of toxine. 

 Thus, when such agents are employed (e.g., the admission of air 

 to diphtheria cultivations), it is possible to plot a curve, the 

 abscissae of which represent the increasing quantities of the 

 agent, and the ordinates the final yields of toxine. So long as, 

 for example, the introduction of air causes the diphtheria bacilli 

 to produce an abundance of toxine and the simultaneous destruc- 

 tion by the current of air of toxine already formed keeps within 

 narrow limits, the curve will rise. But by degrees the destruc- 

 tive effect of the air outweighs its favourable influence on the 

 production, and the curve falls again. There is thus an inter- 

 mediate point at which, with a definite intensity of air current, 

 there is a maximum yield of toxine, and its position obviously 

 depends on numerous conditions, such as the nature of the 

 growth, the culture medium, temperature, &c. This optimum is 

 hardly ever realised in practice, the result being, as we shall see 

 later, that conflicting statements are made as to the benefit or 

 injury produced by the same agents. 



In addition to the introduction of air, other factors may have 

 a similar effect. Thus, an increase of temperature may influence 

 both the production and the decomposition of a toxine. On the 

 other hand, there are apparently agents that do actually increase 

 the final yield of toxine. A considerable amount of work has 

 been done in these experiments to obtain larger quantities of 

 toxines by the use of the most suitable culture media and tem- 

 peratures, by the addition of special substances, &c., so that 

 highly poisonous cultivations of the most important toxines can 

 now be prepared. These methods, however, are of an entirely 

 special character, and it is hardly possible to give at this stage 



1 Lubowski, " Ueber einen atoxischen und avirulenten Diphtheriestamra," 

 Zeit.f. Hyg., xxxv., 87, 1900. 



