276 BACTERIOLOGY. 
local lesions whatever. It would seem to be possible, 
therefore, that tubercular infection may be caused, under 
certain conditions, by absorption through serous or 
mucous membranes without the evidence of any local 
lesion. . 
The experimental production of tuberculosis by in- 
halation of bacilli has been demonstrated by Koch in 
guinea-pigs, rabbits, rats, and mice, and his results have 
since been confirmed by many others; but in these ex- 
periments the bacilli were usually inhaled in the form 
of a very thin spray in which they were suspended. 
The experimental inhalation of dry tubercular dust has 
seldom proved successful. 
Various other tubercular affections which are natural 
in man have been produced experimentally in animals, 
as, for instance, tuberculosis of the joints (Pawlowsky), 
tubercular abscess (Courmont), ete. 
It need hardly be said that the discovery of the 
tubercle ‘bacillus has elucidated the etiology of many 
diseases the origin of which was formerly doubtful. 
Among these may be mentioned the various forms 
of tuberculosis of the lungs and other organs, lupus, 
serofula, fungoid inflammations of the bones and joints, 
tuberculosis in cattle, monkeys, horses, swine, sheep, 
goats, and the so-called spontaneous tuberculosis in 
guinea-pigs and rabbits in cages in which healthy and 
artificially infected animals have heen kept together. 
Of domestic animals cattle are by far the most fre- 
quently attacked by this disease. It is also not uncom- 
mon in young swine. Monkeys, when they are kept in 
confinement, die almost invariably from tuberculosis. 
Among other domestic and wild animals it is a com- 
paratively rare disease. Birds, with the exception of 
