Shortly after the bacillus which couses 

 diphtheria was discovered by Friedrich 

 Loeffler, in 1884, Emil Behring hit upon the 

 idea that a living organism "fights back" 

 against the attacking parasite by some 

 chemical means. In the meantime Emile 

 Roux, a French investigator at the Pasteur 

 Institute in Paris, found that the bacilli of 

 diphtheria produce a virulent poison. After 

 long and difficult experimenting, Behring 

 established the principle of "anti-toxin". 

 He produced a sheep serum with which he 

 cured guinea pigs and rabbits that were 

 sick with diphtheria. Roux started to make 

 gallons of antitoxin serum by using horses. 

 In 1901 Roux and Behring together received 

 the Nobel prize for their important contri- 

 bution 



EMIL VON BEHRING (1854-1917) 



organisms living in the soil, a particular species will produce a substance 

 that is injurious to some other species. This seems, indeed, to be a general 

 fact, although few particular cases have been worked out. Some species of 

 Pemcillium, the very common "blue" or "green" mold (see illustration, 

 p. 375), produce a substance that is destructive of certain species of bacteria. 

 This substance, penicillin, has been extracted and found to be a very power- 

 ful germicide, or germ-killer. It has been found so helpful during the Sec- 

 ond World War that many special plants have been established for producing 

 it on a large scale. Investigators are experimenting with the idea of growing 

 the mold Peiticillium on wound dressings and so preventing infection. 



The experiments so far made suggest an explanation for the fact that 

 when infected materials are buried in the earth, they appear in time to be- 

 come "purified". By means of experiments biologists and other scientists 

 have found that organisms react to injurious foreign substances in many 

 different ways. We may consider the formation of antibodies in larger or- 

 ganisms as adaptive changes in the blood. But since we cannot detect these 

 changes with a microscope, or even by ordinary chemical means, we look 

 for them in the behavior of the serum — the clear fluid left after the clot is 

 removed from blood. 



Blood-Serum Reactions When white-of-egg is placed in the stomach 

 of a backboned animal, it acts as food. If it is injected directly in the blood 

 (of a rabbit, for example), it produces a totally different effect. If, after 

 several such injections, we mix a few drops of serum from a treated rabbit 

 with water containing some egg albumen, a white precipitate will imme- 



240 



