iN SUSCEPTIBLE ANIMALS. 



513 



gelatin, and the branching, cloud-like growth is not as delicate; 



Flugge 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 Flugge 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. 



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 



FIG. 135. Bacillus of 

 mouse septicaemia; 

 culture in nutrient gela- 

 tin, end of four days at 

 18 C. (Baumgarten.) 



FIG. 13H. Bacillus of mouse septicaemia; single colony in nutrient gelatin. X 80. (Flugge.) 



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 



