Tke Tubercle Bacilhis. 
89 
A, Isolated colonies on glycerine agar-agar after 
nearly ten months' growth. Sub-culture from 
huma'n sputum (fourth sub-culture). B, Isolated 
colony after seven mouths' growth. (From 
photographs.) 
inches of platinum w ire fused into the end of a glass rod about 
the length of a penholder. This needle can be sterilised by hold- 
ing it in the gas-flame, and when cool the point is dipped in the 
bacilli to be inoculated, and then lightly traced over tbe surface 
of the jelly. 
The individual bacilli increase, forming ' colonies,' which have 
the appearance of minute white points. These go on increasing 
in .size, and are sometimes smooth and moist, at other times dry 
and crinkled. According to the number of the bacilli inoculated 
the colonies will either remain isolated or join and form a more 
or less continuous coating. 
The appearances are much 7- 
more characteristic when 
this medium is, compara- 
tively speaking, dry. A 
semi - transparent mem- 
branous growth develops 
and thickens, and some- 
times assumes a character- 
istic lichenous appearance. 
In about six weeks to two 
months the culture has fully 
developed. In old cultures, 
especially when the individual colonies remain isolated, the 
appearance is very characteristic. The consistency of the growth 
depends upon the character of the soil and the age of the culture. 
If the medium is moist the growth is moist and viscous, but 
more often it is distinctly tallowy, and in old and dry cultures 
scaly and friable. 
In glycerine-broth, without either gelatine or agar-agar, 
luxuriant growths can be obtained in a few weeks. In four or 
five days minute flakes or specks are visible, which steadily in- 
crease in size, and, subsiding to the bottom of the flask, form 
ultimately a very copious deposit. This deposit is extremely 
tenacious, and on shaking the flask it rises in stringy masses, 
giving an appearance which is quite characteristic. If the flask 
is left undisturbed, a delicate film forms over the surface of the 
liquid, which can be readily broken up by gentle agitation. If 
undisturbed for several weeks this film increases in thickness, is 
irregularly fissured, and has more the appearance of tallow 
floating on the surface. 
To be certain that the growth we have obtained is in reality 
a growth of the tubercle bacillus, we must examine it by the 
method we employ for the detection and examination of the 
bacilli in tubercular tissues, 
