THE DIPHTHERIA BACILLUS 399 



The Schick Reaction. Available evidence indicates that immunity 

 to infection with the diphtheria bacillus depends largely upon the 

 antitoxin content of the blood, and systematic studies of the anti- 

 toxin content of the blood of infants, children and adults by Schick, 1 

 Park, Zingher and Serota, 2 Park and Zingher, 3 Kolmer and Moshage, 4 

 Bundesen, 5 and Moody 6 indicate that a large percentage nearly 80 

 per cent, of young infants, 50 per cent, of children, and nearly 90 

 per cent, of adults exhibit sufficient antitoxin to protect them against 

 the disease. The demonstration of antitoxin in the blood has been 

 simplified greatly by Schick, and modified somewhat by Park. 7 It 

 is made in the following manner: an amount of diphtheria toxin 

 equivalent to one-fiftieth the minimal fatal dose for a guinea-pig is 

 made up to a volume of 0.2 c.c. in sterile salt solution and is injected 

 subcutaneously, or preferably intracutaneously, in the flexor surface 

 of the forearm. Immediately the skin is raised somewhat as the fluid 

 enters the tissues. The reaction elicited depends upon the antitoxin 

 content of the blood, a positive reaction indicating that antitoxin 

 is absent, or present in minimal amounts appears within twenty-four 

 hours as a circumscribed area of redness and a more diffuse area of 

 induration measuring from one-half an inch to more than an inch 

 in diameter. The maximum reaction appears within forty-eight hours 

 and disappears within a week. The blood of a patient reacting in 

 this manner contains less than one-thirtieth of a unit of antitoxin 

 per cubic centimeter. A fainter reaction is frequently exhibited, 

 which is interpreted to mean that the antitoxin content of the blood 

 lies approximately between one-fortieth and one twenty-fifth of an 

 antitoxin unit per cubic centimeter. If the antitoxin content is at 

 least one-twentieth of a unit per cubic centimeter, the. reaction is 

 negative; only a slight reaction results due to the wound itself. 



Practically, it has been found that individuals giving a negative 

 reaction possess sufficient antitoxin to protect them from infection; 

 nurses, doctors, ward orderlies, and patients who react negatively do 

 not need to be immunized with antitoxin if they have been, or are, 

 exposed to the infection. Persons giving a mild or severe reaction 

 should be immunized with prophylactic doses of antitoxin. 



1 Miinchen. med. Wchnschr., 1913, Ix, 2608. 



2 Arch. Pediatrics, July, 1914. 



3 Proc. New York Path. Soc., N. S. 1914, xiv, 151. 

 * Am. Jour. Dis. Child., 1915, p. 189. 



5 Jour. Am. Med. Assn., 1915, Ixiv, p. 1203. 



6 Ibid., 1915, Ixiv, p. 1206. 



7 Loc. cit. 



