^ETIOLOGY OF TUBERCULOSIS. 
125 
method of culture upon firm, transparent breeding ground was adopted, because 
this is superior to all other methods of reinculturen in certainty and ease of man¬ 
agement. With reference to the principle which lies at the foundation of this 
method, as well as in regard to its difference from other treatment, and the manifold 
advantages which it offers, I would refer to the minute description of the same 
given in the earlier pages of this paper. 
At first it was attempted to grow the bacilli from crushed lung tubercles on 
“ nahrgelatine ” (meat-water-pepton-gelatine), but without success. These at¬ 
tempts had been made in the temperature of the room, because in greater heat the 
gelatine becomes liquid and thereby loses all the advantages of a firm breeding 
ground. Since it seemed probable that the attempts failed because a temperature 
of 20° C. was not sufficient for the growth of the bacilli, it was necessary to supply 
another firm, and at the same time transparent, breeding ground, which should 
contain all the component parts demanded for the nourishment of bacilli. Such 
an one seemed to offer itself in stiffened blood serum. I had found in experiments 
made for the purpose of sterilizing blood serum by repeated warming, according 
to the method first given by Tyndall for hay-infusion, that the serum when warmed 
for a considerable time over 65° C., remained stiffened and transparent. Such a 
breeding ground can be exposed for a considerable time to temperatures which 
correspond with the temperature of the body, without undergoing any changes. 
Bacilli-bearing substances were spread out on such stiffened transparent blood- 
serum, and left in a breeding apparatus at 37° C. The direct examination fre¬ 
quently undertaken under slight magnifying power showed after some days the 
appearance of peculiarly shaped colonies, which, as was recognized under a stronger 
magnifying power, and with the use of color reaction, consisted only of tuberculous 
bacilli. Nevertheless, before I proceed to the more exact description of these ba¬ 
cilli cultures, I have still to describe the preparation of the stiffened blood serum, 
which in course of time has proved itself to be the most practical. 
Even the flowing of the blood into the necessary vessels demands several pru¬ 
dential measures. As vessels for catching the blood rather high cylindrical glasses 
provided with a glass stopper are suitable. These are well cleaned, tben washed 
out with a one per cent, sublimate solution, in order to kill any bacteria germs 
possibly clinging to them, and then washed again with alcohol to remove the sub¬ 
limate. Then one lets the blood of the slaughtered animal flow immediately from 
the cut into these purified vessels. Nevertheless it is well not to catch the blood 
first flowing after the stab, because it carries away with it cut hairs and particles 
of dirt from the skin and fur. The vessel should be filled nearly to the rim, closed 
with a stopper and placed immediately in a refrigerator. As soon as the coagula¬ 
tion of the blood begins the vessel must be kept perfectly still, as otherwise the 
formation of a firm cruor would be disturbed and a quantity of red blood-corpuscles 
would be mixed with the serum. The blood-filled vessels remain in the refrigera¬ 
tor from twenty-four to thirty hours and even longer, until a good-sized layer of 
completely transparent amber yellow serum has formed over the cruor. When 
the serum is colored more or less bloody, then it contains too many red blood- 
corpuscles and becomes opaque in warming. The serum is now filled by means 
of a pipette into re-agent glasses which are provided with a wadding stopper. The 
pipette as well as the re-agent glasses and the wadding stopper, are previously made 
