PROBLEM 2. How We Call Conqj/er Some Diseases 



329 



Fig. 297 Bleeding a horse 

 for antitoxin. WJ?y is this 

 horse able to supply anti- 

 toxin? (new yorjc axY 



BOARD OF health) 



ulated, each time with a stronger dose. 

 In this way the horse never develops the 

 disease, but its body produces large 

 amounts of diphtheria antitoxin. This is 

 carried in the plasma. 



Bleeding the horse, clotting the blood, 

 refining and preparing the serum with 

 its contained antibodies, testing it out on 

 a laboratory animal, and finally bottling 

 it are the steps in a long and costly proc- 

 ess, for all these operations must be per- 

 formed with the greatest care and accu- 

 racy. 



Active immunization against diphthe- 

 ria. When Behring's antitoxin is used as 

 a treatment against the disease which has 

 already set in, it prevents many deaths 

 (see Fig. 298). When it is used to immu- 

 nize, it has far less value because the im- 

 munity lasts only a few weeks; the in- 

 jected antitoxins quickly disappear from 

 the blood. In an attempt to wipe out 

 diphtheria as completely as smallpox has 

 been wiped out, scientists set themselves 

 the task of developing an active immuni- 

 zation. Dr. Bela Schick, a Hungarian 

 physician now living in the United States, 

 succeeded in this. He injected some 



diphtheria toxin into the arm of a healthy 

 person. For safety he gave some anti- 

 toxin with the toxin. The mixture is 

 called "toxin-antitoxin." Schick started 

 with a weak dose and gave the cells time 

 to make some antitoxin. Then he gave a 

 second stronger inoculation and after 

 a while a third. Nowadays toxoid, a 

 weakened toxin, is injected instead of 

 toxin-antitoxin. It has been found that 

 one to three injections are needed to give 

 a child active immunity for life. 



Fig. 298 Cojnpare the percetttage of deaths 

 from diphtheria when antitoxin is given the 

 first day with the percentage of deaths when it 

 is given on the sixth day. (saunders) 



