Page:The Harveian oration 1888.djvu/37

29 develope and flourish. Or it may be that these poisonous substances 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 Metschnikoff'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