212 
R. KOCH. 
tuberculous animals. But if one thinks, that to the most various sorts of ani¬ 
mals (cats, rabbits, guinea pigs, field mice) by inoculation with masses of 
perlsucht and the pure cultures gained from them, a disease can be generated 
with the greatest regularity which anatomically is exactly like the disease 
caused by inoculation with tuberculous masses, and which kills the animals 
with the same certainty as the last, then it is not to be expected that man 
should be an exception to this disease-poison. If in the course of further in¬ 
vestigations again a difference between the perlsucht and the tuberculous bacilli 
should show itself, which would compel us to consider the same as only near 
relations, we should even then have all cause to hold the perlsucht bacilli as 
suspicious in the highest degree. From the hygienic standpoint the same mea¬ 
sures must be taken against it as against the infection through tuberculous 
bacilli, so long as it is not proved that man can bring perlsucht bacilli in con¬ 
tact with skin-wounds without danger, that he can inhale the same or bring 
their spores into his intestinal canal without becoming tuberculous. 
The considerable variety in the course of the disease in various individuals 
of the same species, and in their sensitiveness to the tuberculous virus, appears 
to speak against a common classification of all the disease-forms conditioned 
by tuberculous bacilli. These are nevertheless appearances which reappear 
in more or less marked a manner. One helps himself in this case by supposing 
a different disposition for the disease, as well as what concerns the attack of 
the same and its more or less intense course, without that an explanation of the 
same is given by this characterizing of the appearance. A number of vsuch 
differences in the form of tuberculosis is already simply explained by the dif¬ 
ference of the point of infection. Then the quantity of the infectious material 
originally taking effect seems to be of essential importance. Single infectious 
germs are held within bonds more easily and for a longer time by the organism 
on account of their slower development, so that they remain localized ; while, 
when many germs are imported at once, they support each other in their work 
of destruction. A definite representation of that which is characterized as 
individual disposition one can make for all conditions, in which according to 
our previous supposition, certain favorable moments, such as are afforded by 
defects in the epithelial covering of the respiratory mucous membrane, stag¬ 
nating secretions, disturbances of respiration, etc., aid the establishment of the 
tuberculous bacilli. 
If then a large number of the appearances combined under the expression 
disposition may be referred to simple and easily explainable relations, there 
nevertheless remain some facts hard to explain, or not to be explained, which 
compel us to allow the supposition of a disposition to exist for the present. 
This is above all the striking difference of tuberculosis in its course in children 
and in grown people ; further, the undeniable predisposition of many families 
for tuberculosis. Id the last case many cases of tuberculosis laid at the door 
of this predisposition might much better be referred to the increased opportu¬ 
ne y of infection. One can also think of special predisposing causes belonging 
to the family character, such as inclination to catarrh of the respiratory organs, 
defective structure of the thorax. Nevertheless there are many observations 
relative to this point which do not admit of such explanations. Moreover, 
