448 TUBERCULOSIS AND ITS PREVENTION 



greatly weakened germ material. It is hoped that this will stim- 

 ulate the body to make protective materials which will stay in the 

 blood. If the vaccinated person then comes in contact with the 

 active disease, he is already fortified and protected and should not 

 contract the disease. In France, the average mortality among 

 infants from tuberculosis is about 20 per cent. In a recent scien- 

 tific experiment 969 infants who were born of tubercular mothers 

 or were in direct contact with the disease were inoculated. 

 Among the vaccinated infants, for the two years following vac- 

 cination, the mortality for this disease was about one per cent; 

 the mortality was nil after two years. The resistance lasted more 

 than four years. Hence the infants were immunized or protected 

 for the period when tubercular infection is most dangerous. 



Prevalence and economic importance. It is estimated that 

 tuberculosis causes one tenth of all the deaths in civilized coun- 

 tries ; until recent years it was the principal cause of all deaths. 

 There are one million, five hundred thousand cases of active 

 tuberculosis in the United States ; one hundred and fifty thousand 

 deaths occur every year. The mortality, therefore, is approxi- 

 mately ten per cent. There are probably twice as many deaths 

 every year from the tubercle bacilli as there were among our 

 military forces during the World War. 



The disease is estimated to cost the United States $225,000,000 

 a year. The mortality was reduced from 224 for every 100,000 

 people in 1911 to 114.2 in 1922, a reduction of 49.2 per cent. In 

 1928 the deaths from tuberculosis were the lowest on record. 



QUESTIONS AND SUGGESTIONS 



1. What was the contribution of Dr. Villemin to the investigation 

 of tuberculosis ? 



2. Discuss the experiments of Koch. 



3. Name Koch's postulates. 



4. Look up and give a report on the life and work of Koch. 



