■698 PROCEEDINGS OF SECTION I. 



sneezing, the fluids of the mouth, and the foeces of the consumptive, 

 the urine in cases of tuberculosis of the urinary tract, the discharges 

 from tuberculous abscesses and sores, and finally and next in im- 

 portance to the sputum, the milk of tuberculous cows and the 

 flesh of tuberculous cattle. The bovine type of the bacillus tuber- 

 culosis differs from the human in some respects, but it has fre- 

 quently been found in the tubercular lesions of children. 



The paths of infection or channels by which the bacillus enters 

 the system are heredity and inoculation, the respiratory tract and the 

 alimentary tract. Heredity a id inoculation need not detain us, they 

 are so uncommon. A child born with tuberculosis is an exceedingly 

 rare event, and inoculation in the human being is an accidental 

 circumstance. The important thing to remember is that practically 

 there are but two portals — the respiratory and the alimentary. 

 The bacilli are in the air we breathe or in the food which we con- 

 sume. Although the evidence in favour of the entry of the bacilli 

 by the intestinal tract is much stronger than it was some years ago, 

 I am still one of those who believe that in by far the larger number 

 of cases, at any rate in the adult, they find access to the body 

 through the respiratory passages. 



We pass now to the second factor in the causation of tuber- 

 -culosis, namely the susceptibility of the individual, the condition of 

 the soil upon which the seed falls. This susceptibility or lack of 

 resisting power may be local or constitutional. The local circum- 

 stances which predispose are those catarrhal conditions of the 

 mucous lining of the air passages which are found in measles, 

 whooping-cough, pneumonia, influenza and in repeated colds. The 

 presence of the micro-organisms of these diseases renders the soil 

 fertile to the growth of tubercle bacilli. It is this fact which 

 accounts for the firmly fixed popular belief that consumption is 

 caused by neglected colds. Repeated colds do not of themselves 

 give rise to consumption, but they so affect the mucosa of the 

 respiratory tract that the bacillus of tuberculosis when deposited 

 upon it finds a suitable soil and grows luxuriantly in consequence. 

 Another local condition which makes an individual susceptible, is 

 mechanical injury of the mucous membrane of the air passages, as 

 seen in stonemasons, steel filers, rockchoppers, all of whom are 

 highly predisposed to tuberculosis of the lungs. 



The constitutional conditions which render man susceptible 

 are any of those diseases or habits which lower the general tone and 

 diminish resisting power ; convalescence from acute diseases, 

 especially the exanthemata, poor and insufficient food, alcoholism, 

 syphilis, diabetts, dissipation, exhausting pursuits, insufficient 

 exercise and above all, the occupation of dwellings and workshops 

 into which fresh air and sunlight are not freely admitted. Con- 

 sumption has been well called the " house disease." Then there is 

 an inherited constitutional susceptibility in some cases. None of 

 us believe that tubercle bacilli are inherited, but there can be no 

 question that some persons are born with a constitutional tendency 

 to tuberculosis. 



