162 
R. KOCH. 
glands, caseous ulceration of the point of inoculation, emaciation and difficulty of 
breathing ; second, in dissection by the far advanced and very considerable patho¬ 
logical changes proceeding from the point of inoculation into the neighboring 
lymph glands and into the lungs, spleen and liver. Moreover, under microscopic 
examination the characteristic tissue elements of the tubercle and the presence of 
tuberculous bacilli was always proved. The manner in which the inoculation tu¬ 
berculosis conducted itself in the different animals and in the different organs has 
already been described in detail. 
Other experimenters have had less favorable results from their inoculations 
with tuberculous substance. On the other hand the regularly favorable results 
obtained by me will appear less striking when it is considered that I never used 
material in which tuberculous bacilli could not be proved, and that for my inocu¬ 
lations I always used those species of animals which are especially disposed to 
tuberculosis. Besides this, the fact that the inoculations were carried out with 
all possible care and exactness may have contributed not a little to the results. 
One might consider it an omission that no attempts were made with the inocula¬ 
tion of non-tuberculous substances. Nevertheless it did not appear to me neces¬ 
sary to make such attempts myself, because, during the course of my investi¬ 
gations, inoculation with the most manifold substances containing no tuberculous 
bacilli were made by the hundred in the same rooms, and moreover on guinea pigs 
and rabbits, and a tuberculosis traceable to the inoculation was never found. 
Especially was non-tuberculous material very often put into the anterior eye- 
chamber and not a single time did tuberculosis of the iris result, while after the 
inoculation with genuine tuberculous masses it never failed to appear. Besides, 
the abortive inoculations made with the lung tubercles of the monkey, which tu¬ 
bercles had been dried and preserved in alcohol, described in No. 27, form to a 
certain extent such attempts, for plainly by the death of the bacilli the tubercles 
had lost their virulence. The attempt was, therefore, an inoculation with dif¬ 
ferent material. 
My attempts, therefore, justify me in the conclusion that only the inoculation 
with bacilli-bearing substances can cause genuine tuberculosis in the animals used 
for experiment. A distinction in the effect of inoculation from material coming 
from tuberculous processes of various kinds, (such as miliary tuberculosis, phthisis, 
scrofula, fungous diseases of the joints, lupus, perlsucht, and other forms of animal 
tuberculosis) I have not been able to discover. But also in this regard the various 
sorts of tuberculosis show a perfectly uniform behavior. 
F.— EXPERIMENTS IN INFECTION WITH REINCULTUREN OF TU¬ 
BERCULOUS BACILLI. 
This second group of infection experiments forms the conclusion of the proof 
that tuberculosis is an infectious disease and that it is conditioned upon tuberculous 
bacilli. Up to this time it has been proved that tuberculous bacilli occur in all 
tuberculous disease processes and exclusively in these. Further, that only tuber¬ 
culous bacilli-bearing substances have the power of causing tuberculosis. But 
since in both cases the bacilli were still united with parts of the body, the suppo¬ 
sition was justified that besides the bacilli still another material of importance, 
perhaps even the real infectious material, might be present while the bacilli played 
