220 INFECTION AND IMMUNITY 



tered through a Berkefeld candle for the purpose of sterUization, after 

 the addition of 0.8 per cent sodium chlorid. According to Gibson, this 

 method produces a yield of antitoxin which equals about four-fifths 

 of the original quantity but is concentrated five- to seven-fold. The 

 method has more recently been modified as follows': 



After heating to 56° C, as above, and cooling, ammonium sulphate is 

 added to the serum to thirty per cent saturation. This brings down all 

 the euglobulins. This is then filtered and the filtrate, which contains 

 the pseudoglobulins with the antitoxin, is again precipitated with 

 ammonium sulphate in a concentration of fifty-four per cent of satura- 

 tion. The precipitate is then separated on a paper, pressed to dryness, 

 and directly dialyzed.^ 



Park and Thorne ' have found that the use of such concentrated 

 antitoxin is, therapeutically, equally efficient as the unconcentrated, 

 and possesses the advantage of less frequently giving rise to the sec- 

 ondary reactions in skin and mucous membranes occasionally noticed 

 after the use of ordinary antitoxin, and referable, probably, to some 

 other constituent of the horse serum. 



Diphtheria antitoxin is therapeutically used in doses ranging from 

 3,000 to 20,000 units. For prophylactic immunization of healthy 

 individuals, about 500 units should be used. 



TETANUS ANTITOXIN 



Production of Tetanus Antitoxin. — The production of tetanus anti- 

 toxin is, in every way, analogous to that of diphtheria antitoxin. It 

 is necessary in the first place to produce a powerful tetanus toxin. The 

 methods of procuring this will be discussed in the section upon tet- 

 anus toxin, page 458. Suffice it to say here that the most satisfactory 

 method of obtaining toxins consists in cultivating the bacilli upon veal 

 broth containing five-tenths per cent to two per cent sodium chlorid 

 and one per cent pepton. It has been advised, also, that the broth should 

 be neutralized by means of magnesium carbonate rather than with 

 sodium hydrate. The bacilli are cultivated for eight to ten days at incu- 

 bator temperature and the broth filtered rapidly through Berkefeld 

 filters. The toxin may be preserved in the liquid form with the ad- 

 dition of five-tenths per cent carbolic acid, or may be preserved in the 

 dry state after precipitation with ammonium sulphate. 



' Dr. Bamhaf, personal communication. 



'Park and Throne, Amer. Jour. Med. Sci., Nov., 1906. 



