iN SUSCEPTIBLE ANIMALS. 
513 
gelatin, and the branching, cloud-like growth is not as delicate; 
Fliigge compares it to the brush of bristles used for cleansing test 
tubes. In old cultures in nutrient gelatin a 
slight softening of the gelatin occurs along the 
line of growth, and as a result of evaporation 
and desiccation a funnel-shaped cavity is formed 
in the culture medium in the course of two or 
three weeks. In gelatin plates colonies are 
developed in the course of two or three days in 
the deeper layers of the gelatin, but not upon 
the surface; these are nebulous, grayish-blue, 
radiating masses, which are so delicate as to be 
scarcely visible without the aid of a lens or a 
dark background. Under a low power they 
appear as branching feathery masses, which 
have been compared by Fligge to the radiating 
growth of ‘‘bone corpuscles.” In older cultures , 
they coalesce and cause a nebulous opacity of 
the whole plate, which has a bluish-gray lustre. 
Upon the surface of nutrient agar or blood 
serum a very scanty development occurs along 
the line of inoculation. No growth occurs upon 
potato. In bouillon the bacilli cause a slight 
cloudiness at the outset, and later a scanty gray- 
ish-white deposit upon the bottom of the test 
tube; no film is formed upon the surface. 
Fic. 135.— Bacillus of 
mouse septicemia; 
culture in nutrient gela- 
tin, end of four days at 
18°C. (Baumgarten.) 
The thermal death-point of this bacillus, as determined by the 
writer (1887), is 58° C., the time of exposure being ten minutes. In 
the experiments of Bolton it was destroyed in two hours by mercuric 
chloride solution in the proportion of 1:10,000; by carbolic acid and 
Fic. 136.—Bacillus of mouse septicaemia; single colony in nutrient gelatin. x 80. (Fliigge.) 
by sulphate of copper in one-per-cent solution. 
These results are 
opposed to the view that the minute refractive granules which may 
sometimes be seen in the interior of the rods are reproductive spores, 
33 
