142 CHEMISTRY OF IMMUNITY AGAINST BACTERIA 



and all attempts to separate antitoxins from proteids have so 

 far failed. 1 



Antitoxins are retained to greater or less extent by porcelain 

 filters, do not pass through dialyzing membranes readily, and 

 are in general easily destroyed by chemical and physical agen- 

 cies, although much less so than are most toxins. Heating to 

 60-70 injures, and boiling quickly destroys them, although 

 like the enzymes and the proteids, they resist dry heat to 140, 

 and also extremely low temperature, without change. Putre- 

 faction of the serum destroys the antitoxins (Brieger 2 ). They 

 can be preserved for a very long time when dried completely, 

 but in the serum they gradually disappear, especially if exposed 

 to light and air. Acids and alkalies destroy antitoxins, acids 

 being the more harmful in low concentrations. They are de- 

 stroyed in the alimentary tract, without appreciable absorption, 

 except in the case of new-born animals suckling mothers whose 

 blood and milk contain antitoxin (Romer and Much 3 ). When 

 subcutaneously injected, antitoxin soon disappears from the 

 blood ; part may be bound to the tissues, part may be destroyed, 

 since only traces appear in the urine. 



Toxicity of Serum. Antitoxin itself seems to be quite free from 

 poisonous effects. The intoxications observed after injections of anti- 

 toxic serum are not due to the antitoxin, but to the serum itself. Foreign 

 serums, as well as proteids of all kinds, sometimes exert a markedly 

 poisonous influence upon animals into whose circulation they have been 

 introduced. This is manifested not only by sickness and anatomical 

 lesions, but also by the production of specific precipitating bodies in 

 the blood (see "Precipitins"). But if we inject antitoxic serum (for 

 diphtheria) derived from horse blood into another horse, it is quite 

 without toxic effect. 



An interesting phenomenon has been observed in the immunization 

 of animals, namely, that whereas a small dose of a foreign serum may 

 be borne without serious effects, a repetition of the injection after an 

 interval of ten days or more is followed by profound and often rapidly 

 fatal intoxication (this has been called the Theobald Smith phenomenon). 

 The first dose of serum makes the animal susceptible to even a small 

 dose of the same serum (and somewhat susceptible to other serums) 

 which seem to act on the respiratory center. As small a quantity of 



1 An exception is claimed by Proscher (Munch, med. Wochenschr., 1902 

 (49), 1176), which Brieger could not substantiate (Festschrift f. Koch, 1903, 

 p. 445). Homer (quoted by v. Behring, Beitr. z. exp. Therap., 1905, Heft 10, 

 p. 22) found that tetanus antitoxin will partly escape through a dialyzing 

 membrane, and in the antitoxin-containing dialysate no proteid can be found 

 by ordinary precipitation reactions ; but by ultra-microscopic methods proteids 

 can be found in every antitoxin-containing dialysate. 



2 Behring states that tetanus antitoxin resists putrefaction. 



3 Jahrb. f. Kinderheilk., 1906 (13), 684. 



