THE MANUFACTURE OF ANTISERUMS ' 587 



the third day a marked cutaneous eruption appears at the point of 

 inoculation. 



Antigens. — Certain antigens, such as gonococcus and s)Tphilitic 

 antigen, are of value for the purpose of conducting complement fixation 

 tests in laboratory diagnosis. Gonococcus antigen consists of an ex- 

 tract or filtrate prepared from a suspension of poljrvalfent gonococci. 

 Syphilitic antigen consists of an extract prepared from either luetic 

 or certain normal tissues such as beef or human heart muscle. Tuber- 

 culosis antigen, as described by Craig,* consists of the filtrates of 

 specially prepared cultures of Bact. Tuberculosis. 



The Schick Test. — The susceptibility or non-susceptibility of 

 individuals to diphtheria may be determined by the application of the 

 test described by Schick, f For this purpose standardized diphtheria 

 toxin is required. 0.1-0.2 c.c. of a relatively fresh normal saline solu- 

 tion containing )^o minimum lethal dose of diphtheria toxin, for a 

 2So-g. guinea-pig, is injected intracutaneously. The appearance of a 

 circumscribed area of redness at the site of injection after twenty-four 

 to forty-eight hours indicates that the individual possesses practically 

 no immunity against diphtheria. 



t Craig, Am. Jour, Med. Sci., 1915. 150, p. 781. 

 * Schick, Munch, Med. Woch. 1913, 60, p. 2608. 



