Cultivation 599 



These investigations entirely change our ideas of the im- 

 portance of the hog-cholera 'bacillus, whose relation to the 

 disease now comes to resemble that of Bacillus icteroides 

 to yellow fever. However, as the organism is a definite 

 entity and of some importance as a lesion producer, a 

 description of it may not be out of place. 



The bacillus of hog-cholera was first found by Salmon and 

 Smith,* but was for a long time confused with the bacillus 

 of "swine-plague," which it closely resembles, and in asso- 

 ciation with which it frequently occurs. It is a member of 

 the group of bacteria to which Bacillus icteroides and Bacil- 

 lus typhi murium belong. The organism was secured by 

 Smith from the spleens of more than 500 hogs. It occurs 

 in the blood and in all the organs, and has also been culti- 

 vated from the urine. 



Morphology. The organisms appear as short rods with 

 rounded ends, 1.2-1.5 n long and 0.6-0.7 P- in breadth. 

 They are actively motile and possess long flagella (peritricha), 

 easily demonstrable by the usual methods of staining. No 

 spore-production has been observed. In general the bacillus 

 resembles that of typhoid fever. It stains readily by the 

 ordinary methods, but not by Gram's method. 



Cultivation. No trouble is experienced in cultivating 

 the bacilli, which grow well in all the media under aerobic 

 and anaerobic conditions. 



Colonies. Upon gelatin plates the colonies become 

 visible in from twenty-four to forty-eight hours, the deeper 

 ones appearing spheric with sharply defined borders. The 

 surfaces are brown by reflected light, and without markings. 

 They are rarely larger than 0.5 mm. in diameter and are 

 homogeneous throughout. The superficial colonies have 

 little tendency to spread upon the gelatin. Their borders 

 may be circular and rounded, or irregular. They rarely 

 reach a greater diameter than 2 mm. The gelatin is not 

 liquefied. There is nothing distinctly characteristic about 

 them. 



Upon agar-agar they attain a diameter of 4 mm. and 

 have a gray, translucent appearance with polished surface. 

 They are round and slightly arched. . 



Gelatin. In gelatin punctures the growth takes the form 



* "Reports of the Bureau of Animal Industry," 1885-91; and 

 "Centralbl. f. Bakt. u. Parasitenk.," Bd. ix, Nos. 8, 9, and 10, March 



2, 1891. 



