Tuberculosis. 473 



or from their feeding in the same troughs as the cattle or 

 swine. For swine in particular the danger is greater because 

 pf their carnivorous habits ; the rat acquires tuberculosis through 

 eating the offal of the abattoir, or the scraps of the butcher's stall, 

 or kitchen, and the sick rat is thereafter easily caught and de- 

 voured by the pig to its own undoing. To block this channel 

 of infection the destruction of vermin about slaughter houses, 

 stables and pig pens is a most important consideration. 



Flies and Other Insects as Carriers of Tuberculosis. These con- 

 gregating on tubercular sores, around the nares or lips, on the 

 skin contaminated by the virulent bowel discharges, on dishes 

 holding infecting milk, on objects soiled by infecting discharges, 

 on diseased carcasses at abattoirs, rendering works and elsewhere, 

 (Spillman, Hofmann, I,artigau, etc.,) and on graves where the 

 earth worms have brought the bacillus to the surface, (I^ortet, etc. ) 

 become more or less active'agents in disseminating the virus. In 

 this way food and water are contaminated, and exceptionally, in- 

 fection may even be implanted on sores. As the excreta of the 

 flies contain the virulent bacilli, the latter are deposited on 

 windows, walls, furniture, etc. , and may be later disseminated in 

 the dust of the apartment. 



Dewevre found tubercle bacilli in the bedbugs infecting a bed 

 in which successive cases of consumption had developed, showing 

 that other parasitic or rapacious insects besides flies must be 

 looked on as possible propagators of the bacilli. There is reason 

 to suspect lice, fleas, ticks and acari especially. The same is 

 true of leeches and other rapacious invertebrates. 



LESIONS. THE TUBERCLE. 



The characteristic lesion in tuberculosis is the tubercle, taking 

 its name from the small rounded nodule which, at first virtually 

 invisible, encreases often to the size of a millet seed, or a pinhead 

 or even larger, and which by confluence with others, forms con- 

 glomerate masses of all sizes to which the term tubercle is still 

 applied. Where the bacillus tuberculosis is implanted, the 

 fixed tissue cells are stimulated to an undue proliferation, and a 

 diapedesis of leucocytes takes place from the neighboring capillary 

 blood vessels, the whole eventuating in the formation of a rounded 

 cluster or nest of epithelioid and giant and later small rounded 



