ANTITOXIC CONSTITUENT 197 



tion hypothesis of Bordet. Specificity, it is true, is not com- 

 pletely explained thereby, nor is it explained by any other 

 hypothesis. 1 



The antitoxic constituent of antitoxin seems to be a protein 

 body, probably allied to globulin, and, as already mentioned, 

 the globulin content of the blood of an animal treated for anti- 

 toxin production increases in some cases. Tizzoni, by precipitat- 

 ing the antitoxic serum by saturation with magnesium sulphate 

 at 30 C., obtained the antitoxin in the precipitate. By partial 

 saturation of antitoxic serum with ammonium sulphate, the anti- 

 toxin is carried down with the second precipitate, that is with the 

 pseudo-globulin fraction, and various methods have been devised 

 by which the antitoxin can be concentrated and recovered from a 

 comparatively weak serum by means of precipitation with salts. 2 



ANAPHYLAXIS. An animal usually becomes more and 

 more tolerant to injections of an antigen, e.g. to diph- 

 theria and tetanus toxins in the preparation of the corre- 

 sponding antitoxins. Sometimes, however, the opposite 

 effect is produced, viz. increased sensitiveness. This has 

 occurred in the preparation of tetanus antitoxin ; after 

 the animal has received a few doses of the toxin without 

 ill effect, a smaller dose of toxin may cause fatal tetanus. 

 The tuberculin reaction is, probably, another example ; 

 tubercle toxins circulating in the tuberculous individual 

 render him peculiarly sensitive to a minute dose of tuber- 

 culin (i.e. tubercle toxin) which in a normal person pro- 

 duces no effect. The peculiar sensitiveness of certain 

 individuals to such varied substances as pollen, poison 

 ivy, primula, animal emanations, etc., may be of -the same 



1 On the toxin -antitoxin reaction see Craw, Proc. Roy. Soc. Lond., B, 

 vol. Ixxvi, 1905, p. 179 ; Journ. of Hyg., vol. vii, 1907, p. 501 ; and ibid. 

 vol. ix, 1909, p. 46 ; Arrhenius, Immuno-chemistry, 1907, and Journ. of 

 Hyg., vol. viii, 1908, p. 1 : Madsen, Brit. Med. Journ., 1904, vol. ii, p. 567 ; 

 Bordet, Ann. de VInst. Pasteur, xvii, p. 161 ; McKendrick, Proc. Hoy. Soc. 

 Lond.. B, vol. Ixxxiii, 1911, p. 493 ; Gengou, Journ. of State Med., xx, 1912, 

 pp. 65 and 141 (Bibliog.) ; Dean, Lancet, 1917, vol. i, p. 45 (Bibliog.). 



2 See Homer, Journ. of Hygiene, vol. xv, 1916, p. 388. 



