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develope and flourish. Or it may be that these poisonous sub- 

 stances act specially as irritants of epithelial structure, causing an 

 overgrowth of epithelial cells, just as we know will be the result 

 when any other irritant is applied to these tissues; and so the soil 

 is prepared for the lodgment of the bacillus. The human body in 

 the normal state of things may be able to destroy the bacillus 

 tuberculosis, just as the white corpuscles of the frog in Metschni- 

 koff's experiment could destroy the bacillus anthracis, but not 

 when placed in abnormal conditions. 



In connection with this view of the matter, it is significant to 

 find in the case of animals inoculated with tubercle that the 

 lymph glands in the neighbourhood of the inoculation become 

 enlarged and caseous, and this precedes general tuberculosis by a 

 longer or a shorter time. 



Nor would I maintain that the loss of function caused by the 

 swelling and caseation of the various glands was the only way in 

 which the tissue soil could be prepared for the reception of the 

 bacilli. If, as I urge, tissue in a state of decay is suitable, so then 

 I would suggest that imperfectly formed tissue would furnish 

 equally suitable food for these parasites. Such tissue as would 

 result from living in a close atmosphere with poor and insufficient 

 food and insufficient exercise. 



We could not imagine any conditions better calculated than 

 these I have just mentioned to lower the activity or vitality of 

 the epithelial cells of the pulmonary alveoli, or to interfere with 

 the perfect organisation of the tissues generally, or to conduce 

 more effectively to the accumulation of waste or effete material in 

 the circulation, or to impede generally the action of the glandular 

 structures, whereby these waste products should be rendered 

 innocuous ; and no wonder that under these conditions the 



