./ETIOLOGY OF TUBERCULOSIS. 
153 
whether taken from miliary tubercles or from the contents of vomicae, often lupus, 
often tuberculosis of domestic animals, the tuberculous bacilli have been com¬ 
pletely uniform in their conduct. In no way has a change made itself noticed in 
the “ culturen ” continued for a longer period, between sixteen and twenty-two 
months. If I formally made the claim that the culturen of tuberculous bacilli 
possess especially characteristic properties, by means of which the tuberculous 
bacilli could be distinguished from other bacteria, almost with greater certainty 
and certainly with more important grounds than by means of their tinctorial qua¬ 
lities, I can in confirmation of this claim appeal to a very rich amount of examined 
material. There were, namely, after the favorable properties of the stiffened blood 
serum were recognized, numberless attempts made, partly from reinculturen of 
various bacteria, partly from the sowing of the most various animal substances on 
blood serum, but vegetations which resembled the culturen of tuberculous bacilli 
never appeared. These attempts belonging, to be sure, to other experimental 
investigations, form counter-attempts, from which we see that the above described 
characteristic cultures are only to be obtained from substances which contain tu¬ 
berculous bacilli. 
It must still be of special significance for aetiology to determine whether the 
tuberculous bacilli can grow and multiply under conditions which make possible 
to them an existence independent from the body of man and of the animals. For 
the decision of this question it was first necessary to examine whether the bacilli 
only grow on the stiffened blood serum or whether they also flourish in other 
nourishing media. Attempts with liquid sterilized blood serum gave the result, 
that little particles of bacilli-culturen, which were put on the surface of the serum 
in a re-agent glass, developed themselves in the way already described, just as on 
the surface of the liquid beside the stiffened blood serum, and formed a thin whit¬ 
ish coating, which was of a fragile, brittle consistence, and which broke in moving 
the serum and sank to the bottom. The serum always remained clear. When I 
did not succeed in keeping the sowed substance floating on the surface of the 
serum, when it sank into the liquid, the result was no noticeable increase of the 
sowed pieces. 
The blood serum of vaiious sorts of animals showed, as well in a stiffened as 
in a liquid condition, no essential difference in the power of serving as breeding 
ground for the tuberculous bacilli. They appear, to be sure, to flourish best on 
the serum of sheep, cattle and calves. But the serum of horse and swine blood 
gives very vigorous culturen. Even on the serum of dogs blood the culturen do 
not grow noticeably less vigorously, in spite of the fact that this species of animals 
is quite resistent to tuberculosis. On the contrary, tuberculous bacilli do not grow 7 
on the white of eggs. At first I did not succeed in bringing about the growth of 
tuberculous bacilli in other liquids than blood serum. When one or more crumbs 
of a culture were put into a glass with neutralized meat-broth, the crumbs certainly 
appeared in the course of four or five weeks to have increased somewhat in size, 
but it was difficult to decide whether a real growth had taken place. Not until I 
had broken the pieces of the bacilli-culture and rubbed them fine, put them into 
the meat-infusion and by frequent shaking dispersed them through it, that an un¬ 
deniable development took place. It does not appear to be unimportant for the suc¬ 
cess of this attempt, that the culture should be placed in glass alembics wdth a broad, 
