354 SCIENCE PROGRESS 



or lesions apparently confined to the lungs when not either 

 positive or negative to both human and bovine tests are as 

 often positive to the human as to the bovine reaction. 



Origin of Tuberculous Infection 



In view of what has been said above it is difficult to avoid 

 the logical conclusion that the mechanism of infection in 

 children as in adults is in the main by way of the respiratory tract. 



Children may become infected primarily by way of the 

 intestine but there are many possibilities in addition to those 

 afforded by infected food. Thus dirty fingers contaminated 

 with floor dust and particles of dried sputum containing 

 tubercle bacilli are immediately carried to the mouth of a 

 child ; or a tuberculous mother moistens with her lips the 

 child's rubber " comforter" and bacilli are thereby conveyed to 

 its intestinal canal. 



Milk may be and no doubt is an occasional source of 

 tuberculous infection but the importance of giving attention 

 primarily to cows' milk rather than to other hygienic measures 

 for the prevention of consumption is undoubtedly over-rated. 



No effort should be relaxed which will serve to promote the 

 provision of a pure milk supply from well-ordered dairies and 

 clean, well-ventilated, well-lighted cow-sheds ; at the same 

 time, the enormously greater probability of infection from 

 human sources, particularly from cases of pulmonary tuber- 

 culosis, cannot be exaggerated. 



After all, to struggle against tuberculosis by means of 

 measures such as are now employed or foreshadowed by 

 legislation is at best a hopeless task. The evolution of man and 

 of the tubercle bacillus on mutually antagonistic lines seems 

 likely to proceed till the end of time ; only by the gradual 

 establishment of natural immunity, built up step by step by 

 successive generations who have successfully sustained its 

 attacks, can freedom from the disease be at last attained. 



Paradox though it may seem to be, by lessening the general 

 risk of infection of the community, the proposed isolation of 

 persons suffering from tuberculosis may actually retard rather 

 than assist the struggle against consumption. 



What can and should be done is to place all individuals 

 from birth onwards under conditions most conducive to the 



