632 MAN AS A CONQUEROR 



misgivings. The treatment proved successful and the praise of Pasteur 

 was sung all over the world. One more disease had been conquered 

 through the use of vaccines. In this particular case, the causal agent 

 has never actually been found, but it is thought to be a filtrable virus, 

 which once within the body attacks the central nervous system. 



Rabies has been dreaded most, not because of its prevalence, but 

 because of its deadly nature. In well-developed cases recovery is 

 very rare, the mortality being practically 100 per cent. In 1886, 

 when treatments at the Pasteur Institute were first being undertaken 

 on a large scale, 2671 persons were treated with a mortality of less 

 than 1 per cent. By 1912 the mortality was reduced to 0, showing 

 the efficacy of this treatment. 



Hay Fever 



Still another type of disease is fought by means of the principle of 

 active immunity. Sufferers from hay fever and from hay fever 

 hives and certain forms of food poisoning are found to be susceptible 

 to certain proteins. These may be in the form of pollens in the case 

 of hay fever sufferers, or in the form of certain types of foods, or other 

 proteins, such as hair, feathers, and even dust, in the case of asthma 

 or food-poisoning symptoms. In order to discover what causes the 

 susceptibility, extracts of different pollens or different food substances 

 are placed on small abrasions in the skin. An almost immediate 

 reddening welt is formed if the patient is susceptible to the substances. 

 Much relief is afforded and sometimes a total cure of these symptoms 

 is found in an antigen manufactured from the offending proteins which 

 is inoculated in gradually increasing doses until the body builds up 

 resistance sufficient to give tolerance to the offending substance. 



Passive Acquired Immunity 



Another type of immunity depends not on the use of bacteria, but 

 instead, on their products or toxins. Such antitoxin treatment 

 consists of neutralizing the toxin given off by bacteria in the body with 

 immune bodies which have been developed by other organisms. The 

 use of antitoxin is associated with diphtheria, since it was in connection 

 with this disease that this method of treatment was first worked out. 



In 1888, Roux, working in Pasteur's laboratory, found that the 

 diphtheria germ produces a toxin which causes the symptoms of the 

 disease, and a little later the German, von Bering, found that a 

 serum made from the blood of animals that had been made immune 



