IMMUNITY IN TUBERCULOSIS 235 



healthy individuals is limited to the expectoration of persons suffering 

 from tuberculosis of the lungs and upper air passages, the problem 

 before us, while still very large, is less by a considerable amount than 

 if there must also be taken into account the widely prevalent disease 

 among cattle, swine and other domestic animals. While I do not pre- 

 tend to speak in terms of great authority, yet it would seem to me that 

 the time is not yet ripe to disregard, in attempting to suppress tuber- 

 culosis, the disease in domestic animals. Greatly as I sympathize with 

 the active propaganda which is being made by instruction and material 

 help to protect tuberculous human beings from injuring themselves 

 and others, and greatly as I hope to see promoted the means of caring 

 for the tuberculous in sanatoria, etc., yet I hope that there may occur, 

 at this time, no relaxation in the efforts being made to control the 

 spread of tuberculosis among cattle and to prevent the consumption 

 of infected milk and flesh by man and other animals. That, on the 

 other hand, the suppression completely of tuberculosis among cattle 

 would not be followed by a great reduction in the morbidity due to 

 tuberculosis in man is shown by Kitasato's statistics from Japan. In 

 that country the human disease prevailed with its usual activity at a 

 time when the cattle disease, owing to the absence of cattle, was un- 

 known, and milk formed no appreciable element in the food of children. 



In dealing with the complex problem of tuberculosis — a problem 

 whose difficulties enlarge with the continued growth in size of cities — 

 we are materially assisted by the knowledge of the manner in which 

 the virus of tubercle is separated from the diseased body, the conditions 

 of its contamination of our environment, and the avenues through which 

 it endeavors to enter the healthy body. Though it is, perhaps, scarcely 

 to be hoped that a time will arrive when tuberculosis will have become, 

 through precautions against infection, as rare as are to-day smallpox 

 and typhus fever, yet it is a most hopeful result of the crusade against 

 tuberculosis that a marked reduction in the mortality, and probably 

 in the incidence of the disease, has been going on in some countries — 

 as, for instance, in England — for forty years. In New York, the sys- 

 tem organized by Biggs has brought about a reduction since 1886 of 35 

 per cent, in the mortality of the disease ; and while in Prussia the mor- 

 tality was stationary in the decade from 1876 to 1886, since that time 

 a reduction of more than 30 per cent, has been noted. These figures 

 show what may be accomplished in reducing the dangers of infection 

 with tuberculosis by a regime of education, improved conditions of 

 living for the poorer classes, and the segregation in hospitals and 

 sanitoria of any considerable number of the infective tuberculous during 

 the most dangerous period of the disease. 



The discovery of the microbic agent of tuberculosis naturally 

 awakened the hope that a specific means of treating and, possibly, of 



