242 TEXT-BOOK OF BACTERIOLOGY. 



detached from the surface of their place of colonization by strong' 

 currents of air, have been shown to be erroneous, the last -mentioned 

 supposition especially having been disproved by Naegeli's investi- 

 gations. 



It may be stated from the start, therefore, that only such bac- 

 teria can enter the body by way of the air or by respiration as do 

 not succumb to desiccation. 



We have alreadj' seen that the transmission of spores (for in- 

 stance, with the anthrax bacillus) by respiration is not surely estab- 

 lished, but that the bacteria nevertheless possess a very considera- 

 ble resistance to the influence of desiccation. It may be that this 

 power must be credited to special forms or that the rods are in 

 themselves such resisting structures; but it is sufficient that the 

 fact itself is established beyond doubt, thus furnishing the first 

 condition for the infection presumed to take place. 



Where is an opportunity offered to man to inhale dried bacilli ? 

 This question is easily answered. If it be remembered that the 

 very expectoration of tubercular persons usually furnishes the 

 richest supply of rods, and if it be borne in ■ mind how carelessly 

 and heedlessly' this dangerous matter is almost everywhere treated, 

 how it is strewn and scattered about, it will be found a source of 

 infection flowing, unfortunately, so copiously that other sources 

 need hardly be looked for. 



Cornet's beautiful and signiflcant investigations have proved 

 that we are not dealing with a possibility, but with a fact founded 

 on actual conditions. Cornet ascertained that the tubercle bacilli 

 are by no means scattered all about us without choice or difference 

 (as was formerly supposed); that they are not ubiquitous; but that 

 they are only met with in definite, narrowlj^-circumscribed regions, 

 the centre of which is regularly a tuberculous and phthisical person. 



Cornet examined the dry, powdery dust usually settling on the 

 floor and in the recesses of our dwellings. A small quantity of it 

 was injected into the peritoneal cavity of Guinea-pigs, which are so 

 highly susceptible to tuberculosis. If the matter came from places 

 where consumptives had been dwelling the animals succumbed, 

 after the lapse of a few weeks, almost without exception to a pro- 

 nounced tuberculosis. Tuberculosis was mostly confined to the 

 large organs of the abdominal cavity, and as a rule the way in 

 which the spread of the infectious matter had taken place could be 

 established. Local changes had first (as alwaj'-s) occurred in the 

 immediate region of the spot where inoculation had been made. 

 The neighboring lymphatic glands were swollen and had in part 

 already become caseous ; the poison had afterward, by slowly creep- 

 ing on, conquered the territory step by step. In very pronounced 



