181 
from the latter; only by the employment of very dilute watery 
solutions of methylene blue could any distinguishing feature be ob- 
served, viz, that bacilli from a culture of bacillus tuberculosis stain 
only at one spot, the rest of the bacillus remaining unstained ; while 
in the case of bacillus pseudo-tuberculosis the whole bacillus stains 
faintly and generally uniformly, seldom showing a more deeply 
stained part. 
Cultural differences, however, occur. On agar, the bacilli taken 
direct from an infected animal produce visible colonies on the second 
or third day. At first the agar surface is covered with a thick, moist, 
creamy layer; in old cultures by a folded membrane often orange or 
copper colored. After repeated passages through animals cultures 
on agar or glycerin-agar show a dr}^, brittle, crumpled membrane 
resembling that of bacillus tuberculosis. In plate cultures the deep 
colonies are gray in color, round or oval, and uniformly gi^anular. 
On the surface, colonies are better developed, have a uniform granu- 
lar gray center, and a clear, wavy outer zone. The surface of the 
colony is often dry and conical. On butter-agar in fresh cultures the 
colonies are small, white, and dry, later spreading over the whole sur- 
face and becoming yellow or copper colored. On potato a luxuriantly 
growing, moist, gray layer is formed. In gelatin, growth proceeds 
very slowly at ordinary room temperatures, colonies becoming visible 
on the third day. In broth, and especially in glycerin broth, growth 
is rapid, forming in two or three days a folded membrane on the 
surface, the broth remaining clear, the culture closely resembling that 
of bacillus tuberculosis. Broth cultures are distinguishable from 
those of bacillus tuberculosis by their characteristic odor, being un- 
pleasant and ammoniacal; that of bacillus tuberculosis being agree- 
able and resembling the odor of flowers. A small quantity of indol 
is formed in broth cultures, which is not so in bacillus tuberculosis 
cultures. Milk is not coagulated, and on the surface is an abundant 
yellowish-red layer which clings firmly to the glass. On albumin- 
free colorless media a growth appears in two or three days, becoming 
in ten days a thick, yellow, folded membrane ; bacillus tuberculosis in 
the same time on such media forming a thin layer just covering the 
surface and just beginning to fold. The presence of fat in these ba- 
cilli can easily be demonstrated, as in the case of bacillus tuberculosis. 
PATHOGENIC PROPERTIES OF BACILLUS PSEUDO-TUBERCULOSIS: 
The following are the post-mortem appearances observed in a 
guinea pig killed three or four weeks after intraperitoneal injection 
of butter containing the bacillus pseudo-tuberculosis: There is a 
slightly distended abdomen; also peritonitis, with adhesions varying 
in nature from delicate fibrinous bands to firm connective tissue. 
