260 IMMUNOr.OGY 



doses of toxin in a 2 liter flask and add 3,000 units of diluted 

 antitoxin to the toxin. After mixing:, the contents of the flask is 

 then added to enough 0.8 per cent saline containing 0.5 per cent 

 phenol to make the desired volume of 40 liters. The toxin-antitoxin 

 mixture thus prepared is then sterilized by filtration and its toxic 

 property and immunizing value tested by guinea pig inoculation. 

 "When a properly balanced mixture is injected into standard weight 

 guinea pigs, one should find that 0.25 c.c. gives no symptoms, 0.5 

 c.c. may give slight paralysis after 18 days with recovery, 1.0 c.c. 

 paralysis in 14 to 20 days and death Avith complete paralysis in 

 20 to 30 days. Five cubic centimeters should kill a standard 

 weight guinea pig in from four to seven days. The pigs that sur- 

 vive are tested five weeks later to determine their resistance to 

 diphtheria toxin. Those that received 0.25 c.c. and 0.50 c.c. of 

 T.A.T. should witlistand 5 ]\I.L.D. 's and 10 M.L.D. 's of diphtheria 

 toxin respectively. 



Advantages of New Toxin-Antitoxin IMixture, — This new 

 preparation causes fewer local reactions, since it contains less toxin 

 and bacterial protein tluin the earlier mixtures employed. It is 

 also safer and the first injection will serve for children under eight 

 years of age both as a substitute for the Schick test and to initiate 

 the production of antitoxin. In older individuals the reaction 

 does not correlate so well with the Schick test. This is due to the 

 greater toxicity and larger content of bacterial protein in the toxin- 

 antitoxin mixture to which many older individuals are sensitive 

 and give pseudopositive reactions. 



Park (1932) says that since about 1929 they have been using 

 diphtheria antitoxin obtained from goats in the preparation of 

 toxin-antitoxin mixtures. This is done to avoid sensitizing those 

 injected to horse serum. 



Results Determined by Schick Test. — The i-esults of toxin- 

 antitoxin immunization have been determined by means of the 

 Schick reaction and by observing the incidence of diphtheria in 

 school populations and other groups of immunized individuals. 

 In Park's series, the Schick test indicates that only 30 to 40 per 

 cent become immune within 3 weeks after the first injection, 

 approximately 50 per cent at four weeks, 70 to SO per cent within 

 six weeks and 80 to 85 per cent within 12 weeks. 



