348 SCIENCE PROGRESS 



Nature of Tuberculous Infection 



Having very briefly summarised a few of the more important 

 results of tuberculous infection in man and indicated their 

 special incidence in organs and groups of organs at the several 

 periods of life, it remains to consider each of the several sources 

 of infection in light of the evidence adduced. 



Clearly, tuberculous infection — other than infection of the 

 skin — enters the body by the air passages or the alimentary 

 system ; once in the lungs or intestine, the bacilli pass readily 

 through lymphatic channels and reach lymphatic glands, a 

 method of spread in many ways characteristic of children. 



On the other hand, in adults, infection of the air passages 

 is common ; infection by way of the gut seldom occurs. Possibly, 

 the strongly acid character of the gastric juice is normally a 

 factor in promoting destruction of the bacilli. 



When tuberculous ulceration of the intestine occurs in adults, 

 it is most usually due to infection by the bacilli swarming in 

 the sputum coughed up and swallowed by patients in the last 

 stages of pulmonary tuberculosis. 



The two possible sources of infection, however, from ingested 

 food — particularly cows' milk — and inspired air are of import- 

 ance in children. Food taken into the mouth, after mastication, 

 is passed through the fauces into the oesophagus and swallowed, 

 passing across the tonsils on its way to the pharynx. 



It is particularly worthy of note that advanced caseating 

 tuberculosis of the human tonsil is very rare, though caseation 

 of glands in the neck is by no means uncommon. 



Now it has been pointed out by the Commissioners on 

 Tuberculosis that bacilli isolated from glands in the neck show 

 bovine l characters and in their opinion there is therefore pre- 

 sumptive evidence that the glands were infected from milk. 



Furthermore, in 15 out of a series of 96 cases in children in 



1 It should be clearly understood that by bacilli of bovine type is meant bacilli 

 difficult to cultivate on media in the laboratory, capable of producing fatal disease 

 rapidly when inoculated into animals ; it is in no way implied that the bacilli are 

 necessarily derived from oxen. The use of the term in this latter sense in 

 the Reports has not only misled the Commissioners, but has given fictitious 

 support to the view that milk is an effective source of tuberculosis in children. 

 No more unfortunate expression could have been used in discussing an issue 

 which turns entirely on the question whether or no organisms derived from 

 cattle have been introduced into the human system. 



