44 THE PRINCIPLES OF IMMUNOLOGY 



McConkey has given the following rates of deterioration : 



Temperature Deterioration in 6 months 



36 C. 37 per cent. 



6-i6 C. 14 per cent. 



Ice chest 7 per cent. 



The second figures in McConkey's table indicate room temper- 

 ature in winter and summer. Although the two series of investi- 

 gations differ in actual figures, they serve to show that the only 

 temperatures for satisfactory preservation are those of the ice chest. 

 Antitoxin is destroyed by putrefaction of the serum, by acids and 

 alkalies, by ultra-violet rays and deteriorates in solution, by expo- 

 sure to light and air. Ingestion into the alimentary tract destroys 

 antitoxin. Nevertheless, it is stated that suckling infants can absorb 

 antitoxin from the mother's milk. Toxin disappears from the blood 

 in the neighborhood of from seven to .eleven days after injection, it 

 being in part destroyed, in part bound by the tissues, and in very 

 small part excreted in the urine. Antitoxin appears in man very 

 early in life, as determined by the Schick test (see page 53). It has 

 not been proven why the antitoxin develops, that is, whether it is 

 natural or the result of slight attacks of the disease. As indicated 

 above, it may possibly be transferred in mother's milk. Sherman 

 states that lysins and complement are inappreciable in the youngest 

 swine embryos, but that after the ninth week of gestation they can 

 be demonstrated in varying amount. Whether they are autoch- 

 thonous or transmitted from the mother has not been determined. 

 Wells states that, " taken together, the evidence indicates a closer 

 resemblance of antitoxins to proteins than has been shown for the 

 toxins, and all attempts to separate antitoxins from proteins have 

 so far failed." 



The manner in which antitoxin neutralizes toxin is the subject 

 of much discussion, experiment, and hypothesis. Before discussing 

 the matter from a theoretical point of view, it is advisable to explain 

 some of the technical operations in the standardization or titration of 

 the antitoxin. From the practical point of view this is now rela- 

 tively simple, although requiring an extremely precise method, but 

 the earlier investigators were beset with many difficulties. 



Standardization of Diphtheria Antitoxin. In diseases such as 

 diphtheria and tetanus, where the symptoms are the results of the 

 action of the toxin, it is necessary to determine the amount of anti- 

 toxin required to protect an animal against the effect of a given 

 amount of toxin. The earlier investigators attempted to determine 

 the amount of antitoxic serum necessary to protect against inocula- 

 tions with living organisms, but the variability in biological proper- 

 ties of growth and toxin production, infection, and resistance, soon 

 showed the unreliability of this method. Behring then took up the 

 determination of antitoxin against toxin, but found it difficult to 

 standardize such a method over a wide geographic area because of 



