CONTROL OF DISEASE 



341 



First 

 Day 





 Deaths 



Second 

 Day 



43 

 Deaths 



If now a larger quantity of poison is introduced, some of it will 

 be at once neutralised by the free antitoxin ; and if the animal 

 is in good health, an additional quantity of antitoxin will be 

 produced. In this way we may increase the amount of antitoxin 

 in the blood until it contains several hundred times as much as 

 would be necessary to neutralize very many fatal doses of the 

 poison. 



The use of antitoxin is coming to be quite general in the treat- 

 ment of diphtheria and in the prevention of diphtheria in people 

 who have been exposed 

 to infection. We can 

 measure the value of an- 

 titoxin in terms of lives 

 saved, in two different 

 ways : ( i ) Out of all the 

 population, what reduc- 

 tion is there in the num- 

 ber killed by diphtheria ? 

 (2) Of all the people who 

 get the disease, what re- 

 duction is there inthepro- 

 portion that die? Both of 

 these questions are an- 



Fifth 



Day 



or later 



186 

 Deaths 



Fig. 160. Danger in delay 



Each rectangle represents one thousand chil- 

 dren suffering from diphtheria. Antitoxin was 

 administered to all the children on the days 

 indicated. The number of deaths in a group 

 increases with each day's delay in the use of 

 antitoxin 



swered in part by the dia- 

 gram in Fig. 159. The efficacy of the treatment depends upon 

 applying it early after the infection, so that the bacteria may 

 get no headway in the body of the patient. The advantage of 

 the early use of antitoxin is shown in Fig. 160. 



Antitoxin serums have been prepared for tetanus (lockjav/), 

 for snake bite, for scorpion sting, and for castor-bean poisoning. 



258. Precipitin. Another type of reaction to foreign protein is illus- 

 trated by the results of introducing white of egg into the blood of a 

 mammal. We know that in the stomach this substance is readily di- 

 gested, but in the blood of a mammal (a rabbit, for example) it will have 

 a peculiar effect. If the blood is allowed to clot after a number of injec- 

 tions, the serum will react to fresh white of egg by forming with it a 



