106 STUDY AND IDENTIFICATION OF BACTERIA 



makers, the principle being that the antitoxin in the horse serum is precipitated 

 with the globulins which come down on half saturation with ammonium sulphate. 

 In this way, as the content in horse-serum proteids is lessened, the anaphylactic 

 dangers are lessened. 



As a curative measure, from 2500 to 5000 units should be injected. 

 If the injection is delayed or the case very serious the dose should be 

 10,000 units. As much as 50,000 units has been given in severe cases. 

 The prophylactic dose is 500 units. 



Schick Reaction. By the employment of this reaction we can under- 

 stand why one child develops clinical diphtheria and another only shows 

 the organism in the throat (laboratory diphtheria). We find that cer- 

 tain persons have sufficient amount of diphtheria antitoxin normally in 

 the circulation to protect against the soluble toxin elaborated by the 

 organisms localized in throat or nose. Such cases show either a mini- 

 mal or negative reaction. 



Persons not having any antitoxin in the circulation show a positive reaction. 

 The test is performed as follows: With a small sharp hypodermic needle we inject 

 intradermally ^ f a minimum lethal dose (i M. L. D.) of diphtheria toxin as 

 determined for a 25o-gram guinea-pig. The standardized toxin is so diluted with 

 a ^% carbolic acid solution that o.i c.c. contains ^so of a M. L. D. A positive 

 reaction shows within twenty-four hours, reaching its maximum intensity in two 

 days, as a reddened area, about i inch in diameter with more or less induration. 



The reaction persists for about a week, leaving a brownish pigmentation. Positive 

 reactions show that the patient has less than % Q oi a. unit of antitoxin in i c.c. of 

 his blood-serum and that he possesses no immunity to diphtheria. 







This test is of great value as showing the cases needing prophylactic 

 injections of antitoxin. Furthermore nurses showing a positive reac- 

 tion should not take care of diphtheria patients. Carriers of true 

 diphtheria usually show a negative reaction as contrasted with 

 pseudodiphtheria ones. 



It is of value in showing duration and degree of immunity following antitoxin 

 injections and such investigations have shown that intravenous injections are the 

 most efficient, next the intramuscular and least efficient the subcutaneous route. 

 Moody obtained an average 'of 45.2% positives in 524 people examined. 



Sudden death after administration of antitoxin has been reported in 

 cases of status lymphaticus. (See anaphylaxis.) 



Laboratory Diagnosis. In obtaining material from a throat, be sure that an 

 antiseptic gargle has not been used just prior to taking the throat swab. The part 

 of the swab which touched the membrane or suspicious spot should come in contact 

 with the serum slant. This is best accomplished by revolving the swab. An im- 



