148 
R. KOCH. 
ORIGINAL ARTICLES. 
/ETIOLOGY OF TUBERCULOSIS. 
By Dr. R. Kooh, Privy Councillor. 
(Translated by Rev. F. Saure.) 
( Transactions of the Massachusetts Veterinary Medical Association.) 
(Continued from page 130.) 
A very different image is presented by the culturen developing from substan¬ 
ces which contain only scattered bacilli. As has already been suggested, one does 
not succeed in such cases in freeing the bacilli by rubbing and crushing the sub¬ 
stance, and spreading it on the surface of the serum. They remain, in the substance 
and form there colonies which grow almost to the size of a poppy seed. In such 
cases there can be no doubt that each single little colony proceeded from one sin¬ 
gle, or at most two bacilli, because microscopic investigation has always found 
only 1-2 bacilli in a giant cell of the tissue in question. Accordingly we can 
also further conclude that, in the formerly mentioned examples, the single scales 
developing upon the serum proceeded also from single bacilli. 
If a beginning of reinculturen of tuberculous bacilli has been obtained in 
the manner just described, they can be carried on without difficulty. For this 
purpose some of the whitish scales can be put into a re-agent glass containing 
stiffened serum by means of the platinum wire, which must be made glowing 
hot and then cooled again, immediately before its use. By the use of this wire 
the scales are also to be spread as much as possible on the serum surface, and 
rubbed to pieces. In this second sowing far more numerous bacilli reach the 
serum surface, and can there be spread more easily and evenly than was the case 
with the original inoculating material; in consequence of which one obtains in 
this and later breedings, no longer single scales, but coherent, membrane-like 
colonies. These take in general the figure which the motions of the platinum 
wire prescribed beforehaud in the sowing. They can therefore be laid on in lines, 
either in a perpendicular or horizontal direction, or may take any figure one may 
choose to construct on the serum. Vigorously growing cultures nevertheless 
spread more or less beyond the original limits of the sowing. This spread is, 
however, not the conseqm nee of independent motions of the bacilli, which, as 
already shown, they do not possess, but it takes place in consequence of the fact 
that in the constant increase of the bacilli the increase of mass does not take 
place in the diameter of the thickness, but in area. The growing bacilli do 
not heap themselves upon each other, but have the tendency to spread out in 
area and push the already formed coherent membrane away over the surface of 
the serum. This is most marked when the bacilli membrane reaches the liquid 
at the base of the re-agent glass. It does not penetrate into the liquid, but it 
forces itself over the same and forms a fine cover on the surface of the liquid. 
Very often indeed it presses up to a height of some millimeters on the opposite 
side of the glass. 
The bacilli “ culturen” have other noteworthy qualities by which they may 
be distinguished from other bacteria “ culturen ” by the naked eye. In the first 
