166 
R. KOCH. 
Eleventh experiment: By former opportunities an essential difference in the 
sensitiveness of house mice and field mice to inoculation with tuberculosis had 
shown itself. Again, therefore, twelve white mice were inoculated with ardncul- 
tur of miliary tuberculosis (No. 22), the same which had served in the inocula¬ 
tion of the field-mice in the sixth experiment, and, moreover, at the same time as 
the field-mice. While the field-mice, as has already been said, became tubercu¬ 
lous, the w T hite mice remained for two months without any appearance whatever 
of sickness ; they were then killed and tuberculous changes found in none of 
them. 
These eleven experiments have the one common feature, that the inoculating 
substance was put into the animals subcutaneously. The effect was in general 
the same as when fresh tuberculous pieces of tissue were inoculated subcutane¬ 
ously. The little skin wound closed up and healed in the first days, then fol¬ 
lowed gland swelling, emaciation, death, and dissection showed a great far-reach¬ 
ing tuberculous erruption in lungs, spleen and liver, with the further characteris¬ 
tic changes of these organs belonging thereto. Only in so far a distinction was 
noticeable as that after inoculation of the reinculturen the course of tuberculosis 
was a more rapid one, than after the inoculation of tuberculous tissue. For 
guinea pigs this difference in time can be reckoned on the average as about two 
weeks. This appearance explains itself most naturally by the assumption that in 
the inoculation of tuberculous tissue, the tuberculous bacilli are enclosed by the 
latter and cannot, therefore, have their effect until the tissue is resorbed, while 
those in the reinculturen can get immediately into the subcutaneous tissue of the 
animal, and can immediately begin to act. The same is the case in the inoculation 
of the anterior eye-chamber of rabbits, and the iris-tuberculosis arising from it, 
and it is here the case to a more striking degree because the developement of the 
tubercles can here be observed with the naked eye. Microscopically the tuber¬ 
cles obtained by the inoculation of reinculturen resemble in every way those ob¬ 
tained by the inoculation of genuine tuberculous tissue, and just the same the 
tubercles arising spontaneously. They consisted of heaps of cells, which mostly 
had the character of epithelioid cells and closed giant cells, and contained besides 
these, tuberculous bacilli in greater or less numbers. Their virulence could be 
seen from the fact, that in all cases they had spread themselves out from the 
subcutaneous tissue over all the organs favored by tuberculosis. Besides this, in 
several cases, farther inoculations were carried out upon other animals and tuber¬ 
culosis regularly created thereby. The inoculation of the reinculturen remained 
without effect only in some species of animals, little or not at all sensitive to tu¬ 
berculosis. On the contrary it made the other numerous animals tuberculous 
without exception, and as, besides this, all the animals used for counter-experi¬ 
ments remained healthy, there could be no doubt that the question for the decis¬ 
ion of which these experiments were undertaken, must be answered in the affir¬ 
mative, and that the tuberculous bacilli are to be considered the sole cause of 
tuberculosis. 
Nevertheless, it seemed necessary not to stop here, but also to introduce the 
reinculturen of tuberculous bacilli into animals by all the other methods of infec¬ 
tion used up to this time in investigations regarding tuberculosis, in order so to 
prove in every direction their identity with the tuberculous virus. The methods 
