1 82 MANUAL OF BACTERIOLOGY. 



But be|this as it may, it is well established that the serum of 

 the blood deprived of leukocytes also has the property of 

 destroying bacteria in many cases. It has been found that 

 the serum of animals which have been inoculated with in- 

 creasing amounts of culture is greatly enhanced in bactericidal 

 power. Whether this enhanced power is due to substances 

 liberated by the leukocytes or whether it is derived from other 

 sources is a matter of dispute. It is not yet certain, in other 

 words, what is the source of bacteriolysin, but its production 

 is stimulated by the gradual inoculation of the animal with 

 cultures. 



It has already been explained that the neutralization of 

 bacterial poisons or toxins takes place by the production of 

 antitoxins (see page 176), and that the gradual injection of 

 toxins is followed by a greatly increased production of anti- 

 toxin. Bacteriolysins, then, are produced — or at least their 

 production stimulated — by injections of bacteria, antitoxins by 

 injections of toxins; and Ehrlich advanced his now celebrated 

 side-chain theory to explain these phenomena as well as the 

 formation of agglutinins, lysins and precipitins. 



Ehrlich's Side-chain Theory of Immunity.* — Ehrhch 

 was the first to offer an explanation from a chemical point of ' 

 view of the action of toxins on cellular protoplasm and the for- 

 mation of antitoxins. He assumes, to begin with, that the mole- 

 cules of the protoplasm are to be regarded as being endowed 

 with chemical groups, present in the form of lateral appendages 

 to the molecule, called side-chains. They can be illustrated 



* The literature of this subject is very extensive. An exhaustive review is 

 that by L. Aschoff. EhrHch's Seitenkettentheorie. Zeitschrijt jiir allgemeine 

 Physiologie. 1902. 



The following are also of a general character: Ehrlich's Croonian Lecture. 

 Proceedings of the Royal Society. LXII., p. 437. igoo. Ehrlich. Schluss- 

 betractungen. Nothnagel's System of Medicine. Vol. VIII. H. C. Ernst. 

 Modern Theories of Bacterial Immunity. 1903. Prudden. Medical Record. 

 February 14, 1903. Ritchie. Journal of Hygiene. Vol. 11. 1902. Bergey. 

 American Medicine. October 11, 1902. Immunity. Special Article. Journal 

 of the American Medical Association. No. 4 et seq. 1905. 



