THEORIES OF IMMUNITY. 



blood after a short time, even if no more toxine 

 be injected to induce its return. This has also 

 been shown by Roux and Yaillard in the case of 

 a rabbit immunized against tetanus, in which 

 practically the whole of the blood was removed 

 during a series of days, with no sensible lessen- 

 ing of the antitoxic power; whilst a similar 

 thing was demonstrated by Salomonson in goats 

 immunized against diphtheria. (Ann. de l'Inst. 

 Past., 1893, VIL, p. 65; and Ibid., 1898, XII., 

 p. 763.) 



All of these instances would seem to indicate 

 that the production of antitoxine is in the nature 

 of a hypertrophy of function, and how great this 

 may be is illustrated in not an extreme degree 

 by Ritchie (I. c, p. 236), in which he demon- 

 strates that an antitoxic serum may be produced 

 one hundred times stronger than the toxine 

 originally introduced; i.e., if tetanus toxine be 

 acted upon by hydrochloric acid until its tox- 

 icity be destroyed, it still retains the capacity of 

 giving rise to immunity. By acting for the 

 same time on different portions of the toxine 

 there is no doubt that on each occasion the 



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