IN SUSCEPTIBLE ANIMALS. 415 



The superficial colonies may attain a diameter of two millimetres ; 

 they present no distinctive characters. Upon agar plates the colonies 

 may have a diameter of four millimetres ; they have a grayish, trans- 

 parent appearance and a shining surface. In gelatin stick cultures 

 small, yellowish-white colonies are developed along the line of in- 

 oculation, which may become confluent ; upon the surface a thin, 

 pearly layer is developed about the point of inoculation, which may 

 have a diameter of six millimetres or more. Upon potato a straw- 

 yellow layer is developed, which later acquires a darker color. In 

 slightly alkaline bouillon a slight cloudiness may be observed at the 

 end of twenty-four hours, and at the end of one or two weeks, if 

 not disturbed, a deposit is seen at the bottom of the tube and a thin, 

 broken film may form upon the surface. The development of this 

 bacillus in milk produces a direct solution of the casein without pre- 

 vious coagulation ; when a solution of litmus has been added to milk 

 it retains its blue color in presence of this bacillus, while the bacillus 

 previously described causes it to change to red. Neither phenol 

 nor indol is produced in solutions containing peptone (Bunzl-Federn) 

 another distinguishing character from the Bacillus septicsemise 

 hsemorrhagicse. This bacillus may be cultivated in slightly acid 

 media, which after a time acquire an alkaline reaction. 



In Smith's experiments this bacillus was found to resist desicca- 

 tion from nine days to several months, according to the thickness of 

 the layer dried upon the cover glass ; bacilli from an agar culture in 

 some experiments failed to grow after seventeen days, and in others 

 still gave cultures after four months. Bouillon cultures are steril- 

 ized in four minutes by a temperature of 70 C., in fifteen minutes 

 by 58 C., and in one hour by 54 C. (Smith). Novy has isolated 

 from cultures of the hog-cholera bacillus a toxic basic substance 

 which he calls susotoxin. This was obtained by Brieger's method ; 

 it is a yellowish-brown, syrup-like liquid, which, when injected into 

 rats in doses of 0.125 to 0.25 cubic centimetre, causes their death in 

 less than thirty-six hours. He also obtained by precipitation with 

 absolute alcohol, from cultures concentrated in a vacuum at 36 C., 

 a toxalbumin which when dried was in the form of a white powder 

 easily soluble in water. Rats died in three or four hours after re- 

 ceiving subcutaneously a dose of 0. 1 to 0. 5 gramme. 



Pathogenesis. Pathogenic for swine, rabbits, guinea-pigs, mice, 

 and pigeons. 



In certain parts of the United States the disease known as ' ' hog 

 cholera " frequently prevails among swine as a fatal epidemic. It 

 may occur as an acute and quickly fatal septicaemia, or in a more 

 chronic form lasting from two to four weeks or even longer. In 

 the acute form death may occur within twenty -four hours, and haem- 



