BACTERIUM DIPHTHERIA 103 



For immunizing purposes, that is, to protect persons exposed 

 but not yet suffering from the disease, from 300 to 1000 units 

 are used. In both cases a repetition of the dose is frequently 

 demanded, and in case the exudate does not fade, the injec- 

 tions may have to be given several times. The effect is a 

 passive acquired immunity, as it is the addition of a toxin- 

 neutralizing substance to aid tissues, for which they them- 

 selves have not worked. The visible effects of antitoxin 

 administrations are a rather rapid disappearance of the false 

 membrane, a fall of temperature, and a lessening of consti- 

 tutional prostration. 



For the best results in the treatment of diphtheria, anti- 

 toxin should be used early. Each hour of delay in using it 

 after the diagnosis has been made reduces the good changes 

 of the patient. For large cities the decrease in mortality 

 has been 50 per cent., and in the favorable cases, even 75 

 per cent. 



As is well known not all persons are susceptible to diph- 

 theria, indeed a rather small percentage do contract the dis- 

 ease. This is due to the fact that the blood serum of unsus- 

 ceptible individuals contains natural antitoxin, so that viru- 

 lent bacilli alighting on the throat find an unfavorable place 

 to grow. Advantage has been taken of this condition in the 

 Schick test which consists of the introduction of a minute 

 amount of diphtheria toxin into the layers of the skin. If the 

 person be susceptible to diphtheria, that is, has no natural 

 antitoxin, a red swollen area will appear in twenty-four to 

 forty-eight hours. If, on the other hand, antitoxin is present 

 no reaction occurs because the small amount of toxin put 

 into the skin has been neutralized; such an individual is 

 rather certain not to contract diphtheria and does not require 

 the immunizing dose of antitoxin if exposed. About 80 per 

 cent, of infants and adults give a negative reaction; children 

 and adolescents give a lower percentage, showing what is 

 borne out by clinical observation, that they are more sus- 

 ceptible to the disease. This test saves much time and 



