k 



Artificial immunity against toxins 355 



substances of the serum. It is usually regarded as belonging to 



Sie same albuminoid group of substances, though it is not possible 

 ) prove this satisfactorily. Von Behring^, however, who studied 

 lis question in collaboration with Knorr, denies the albuminoid 

 ature of tetanus antitoxin. After demonstrating that this anti- 

 3xin, when the antitetanus serum is submitted to dialysis, passes 

 through the dialysing membrane, these observers found that they 

 could not obtain the characteristic reactions of albuminoids in the 

 dialysed fluid. It must be admitted, however, that this negative 

 result is not sufficient to justify a denial of the albuminoid nature of [373] 

 antitoxin. When Nencki and Mme Sieber^ sought to produce the 

 reactions of albuminoid substances with the digestive juice of 

 Nepenthes (the well-known insectivorous plant) they got no result ; 

 but after the concentration of the juice in vacuo, it at once gave the 

 characteristic reaction with nitric acid, and also with acetic acid, 

 potassium ferrocyanide and Millon's reagent. 



The antitoxins may be precipitated along with the globulins and 



e distinguished, in general, by a fairly great resistance against 



hysical and chemical influences. In this respect they are allied to the 



agglutinins, the fixatives and the precipitins, considered elsewhere, and 



,re sharply distinguished from the cytases. The antitoxins resist 



mperatures which destroy the cytases and remain unaltered to 



beyond 60° — 65° C. They are more stable than the delicate toxins of 



tetanus and diphtheria, but they are more easily altered than the 



toxins of cholera, of Bacillus pyocyaneus and the venoms. When 



stored in a dry state in the residue of evaporated serums and protected 



from light and air, the antitoxins will keep for a very long time 



without showing any notable attenuation. This property is very 



important in practice. 



The antitoxins, in this respect also resembling the fixatives and 

 the agglutinins, are humoral substances in the strictest sense of the 

 term. They are found not only in prepared serums but abound also 

 in the plasma of the circulating blood, and in the plasmas of the 

 lymph and of exudations. Vaillard and Roux^ have shown that the 

 clear acellular serous fluid of the oedema produced by the slowing 

 of the circulation in rabbits vaccinated against tetanus toxin, is as 

 antitoxic as the blood itself. Even the aqueous humour of a strongly 



1 "Die praktischen Ziele der Blutserumtherapie," Leipzig, 1892, S. 52, 



2 Ztschr.f.physiol Chem., Strassburg, 1901, Bd. xxxii, S. 318. 

 s Ann. de I' Inst. Pasteur, Paris, 1893, t. vii, p. 81. 



23—2 



