THE WAR WITH THE MICROBES. 493 



daily yielding new and brilliant results, to find means for controlling a 

 disease which annually causes one-seventh of the deaths of the popu- 

 lation of the globe? 



However, it is not only for protection against the two diseases, teta- 

 nus and diphtheria, just mentioned, that antitoxic serums can be pre- 

 pared. Recent investigations have proved that typhoid fever, cholera, 

 anthrax, the plague, etc., are amenable to similar treatment and in 

 the same department in this city that chemical vaccination received its 

 first impetus, but by workers in the biochemic laboratory it has been 

 demonstrated that two diseases that cause such losses to the farmers 

 of the country may be controlled by antitoxic serums. Investigators 

 in this same laboratory have shown also that a substance antitoxic to 

 tuberculosis can be produced in the serum of animals when they are 

 properly treated, which has undoubted and pronounced effect in check- 

 ing experimental tuberculosis in small animals. 



When we inquire the character of these antitoxins we are almost as 

 yet more in the dark than in our efforts to discover the exact nature of 

 the poisons of germs. However, it has been possible to separate in a 

 fairly pure form the antitoxic principle from diphtheria serum, a minute 

 amount of which will confer immunity and the antitoxic principle of 

 swine plague, 0.002 gram of which has been found to cure animals 

 weighing 1 pound, and even a solid antitoxic-like substance for tuber- 

 culosis has been obtained in an impure form. All these solid antitoxic 

 principles resemble each other very closely in their chemical tests and 

 methods of separation, showing albuminoid reactions, but in their cura- 

 tive properties they are totally independent the one of the other. The 

 diphtheria antitoxic serum does not cure tetanus; the swine plague 

 serum does not cure the cholera. 



In the case of the venom of serpents it has been found that repeated 

 injections will make the serum of an animal antitoxic and curative 

 against other venoms. The antitoxic serum produced by the cobra 

 venom will protect animals and men against the bite of the rattlesnake 

 as well as its own bite. It would seem from this that there is a very 

 close relationship between the poisons of venomous snakes, and that 

 immunity to one also gives protection from the other. It appears very 

 probable, also, that the poisons of germs belonging to the same genus 

 will be closely allied and that an antitoxin for one will also be an anti- 

 toxin for the other. In fact, it has been demonstrated that the 

 products of the bacillus coli communis will protect animals from the 

 typhoid germ, to which it is closely allied. The same effect will proba- 

 bly be obtained with many other diseases where the germs are related. 



The difficulty of separating these antitoxins completely from the 

 other constituents of the blood has made it impossible as yet to obtain 

 positive information as to their true chemical character. 



As to their action in producing immunity, one theory is that they 

 directly neutralize the poisons which the germs produce, but this does 

 not seem to be substantiated by experiment. 



