INFECTION 77 



organisms are distinct and the poisons they produce have 

 specific characteristics. 



The Nature of Toxins. Very similar to the venom of ser- 

 pents; highly poisonous in minute doses ( T oVo g^ 111 of tetanus 

 toxin will kill a horse weighing 600 kilos 1200 pounds). At 

 first toxins were called ptomains, or cadaveric alkaloids; but 

 this term is applied now to such poisons as have a basic nature 

 and arise in decomposing meat, cheese, and cream as a result 

 of chemical change in the material, the bacteria causing the 

 change. Then they were called toxalbumins, and were supposed 

 to belong to an albumin series; but when the bacteria are grown 

 in non-albuminous media, the toxins correspond more in their 

 chemical composition to & ferment, and therefore it is supposed 

 that the albumin part of the toxin is furnished by the blood or 

 albuminous media in which it is formed. The term toxin is to 

 be preferred in speaking of bacterial poisons. 



Toxins may be of two sorts: (a) Chiefly within the bodies of 

 the bacteria, so that they are set free by the disintegration of 

 the organisms. This group comprises most of the pathogenic 

 bacteria and must be combated by the use of antibacterial 

 serums, (b) The poisons seem to be excreted by the bacteria 

 and are found in the surrounding medium. Antitoxic serums 

 are applicable to this group, which includes the bacilli of diph- 

 theria and tetanus. Welch has suggested that even bacteria 

 which do not appear to form toxins in artificial cultures may 

 do so in the human body. In the effort to adapt themselves 

 to their environment and resist the hostile agencies of the body 

 they produce the poisons we call toxins. (For method of pro- 

 duction of an antitoxin, see article on Diphtheria.) 



Toxins are not stable; they are uncrystallizable, soluble in 

 water; they are allied to albumose in that they are precipitated 

 by alcohol and ammonium sulphate. 



Aggressin. A name given to a form of toxin developed in the 

 animal body that has the power of rendering a germ more active 

 (aggressive) . If such a toxin is obtained from an experiment 

 animal and added to a growth of bacteria, it makes that culture 

 particularly virulent. Aggressins are supposed to have a par- 

 alyzing influence on the phagocytes, 



