/ETIOLOGY OF TUBEKCULOSIS. 
129 
spleen, etc., are to be used for culturen. One must always operate with instru¬ 
ments that have been made red-hot, and these must be changed every time a new 
layer is to be exposed. All preparatory cuts which do not touch the inoculating 
substance itself are to be made with hot instruments, the inoculating mass on the 
contrary to be cut out with cooled scissors and pincette. The constant change of 
instruments is necessary in order that impurities which might attach themselves 
to the instruments in cutting the skin and the superficial layers may not be car¬ 
ried into the culturen. 
When the organs of animals which have just died or just been killed were at 
my disposal, and the sowing was carried on in the manner just described with 
substances containing tuberculous bacilli, the reinculturen have succeeded with¬ 
out exception. The result was, on the contrary, uncertain when the material 
from human corpses or cattle suffering from “ perlsucht ” was used, since there 
were always impurities on the surface, and it was moreover not wholly fresh 
when I received it. In these cases I have first repeatedly and thoroughly washed 
the surface of the object with one per cent, sublimate solution, then with con¬ 
stantly changed, glowing hot instruments taken off the upper layers one at a 
time, and cut the inoculating substance from a depth at which I could feel sure it 
was free from foreign bacteria. In this manner I usually succeeded in obtaining 
reinculturen from material of this sort, especially from little lung vomicae lying 
near the surface whose covering was removed with hot instruments after treat¬ 
ment with sublimate. 
After the stiffened serum is inoculated with a bacilli-bearing substance, the 
vessels are placed in a breeding apparatus and kept constantly at a temperature 
of 37° C. Not every breeding apparatus is adapted to the culture of tuberculous 
bacilli. The growth proceeds but slowly and the vessels must therefore remain 
for weeks at a time in the apparatus. When the breeding apparatus, owing to 
its construction, causes a rapid evaporation of liquid from the vessels, the serum 
dries before the tuberculous bacilli have developed into visible colonies. Es¬ 
pecially such apparatus as are unequally warmed, so that the steam always present 
in them condenses on the cooler places, for example on the glass cover, and must 
be constantly replaced by steam developed from the culturen vessels, cannot be 
used. The Arsonval thermostaten are very practical; the warmth is evenly di¬ 
vided and the serum keeps almost unchanged in them. 
In the first few days one will notice no change in the culturen in the breed 
ing apparatus. If a change occurs, if whitish or even other colored drops or spots 
appear on the surface of the serum, if these enlarge more or less quickly, be¬ 
cloud the liquid in the bottom of the glass, or even liquefy the serum, this is a 
sign that the cultur is not successful, and that foreign bacteria have forced them¬ 
selves in and grown more luxuriantly than the bacilli. If one examines such 
drops or spots he always finds them to consist of bacilli or micrococci which, un¬ 
der Ehrlich’s color treatment, always take a color opposite to that of the tubercu¬ 
lous bacilli, and are distinguished from them in size and shape. 
In those little glasses which have remained free from such impurities the first 
suggestions of the growing colonies of tuberculous bacilli do not show themselves 
until after ten to fifteen days. They appear as pale white little points or spots, 
which lie on the surface of the serum, are without lustre, and on that account 
