626 Bacillus Suipestifer 



from this disease in the United States range from $10,000,000 to $25,000,000. 

 For years it was thought to be caused by the Bacillus suipestifer, but 

 DeSchweinitz and Dorset* were able to transmit the disease from one hog to 

 another in certain of the body fluids that had been passed through the finest por- 

 celain filters and were shown by inoculation and cultivation to be free of bacilli. 

 It therefore depends upon a filterable and unknown virus. 



This observation was received with approval by those who had any experience 

 with the effect of hog-cholera bacilli upon hogs, all of whom must have observed 

 that though infection with the bacilli occasionally caused the death of an animal, 

 the dead animal usually did not show the typical lesions of the disease and never 

 infected other animals with which it was kept. The papers upon the subject by 

 Dorset, Bolton, and McBrydef and by Dorset, McBryde, and Nilest are worth 

 reading. 



These investigations entirely changed our ideas of the importance of the hog- 

 cholera bacillus, whose relation to the disease now comes to resemble that of 

 Bacillus icteroides to yellow fever. 



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 resem- 

 bles, and in association with which it frequently occurs. It is a member of the 

 group of bacteria to which Bacillus icteroides and B. tj?phi 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 cultivated from the urine. 



Morphology. — The organisms appear as short rods with rounded ends, 1.2 to 

 i.S M long and 0.6 to 0.7 fi. in breadth. They are actively motile and possess long 

 flageUa (peritrichia), 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. 



Cultivatioii. — 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 define^ 

 borders. The surfaces are brown by reflected light, and without markingsd 

 They are rarely larger than 0.5 mm. in diameter and are homogeneous through-, 

 out. The superficial colonies have little tendency to spread upon the gelatin. 

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



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 of a nail with a flat 

 head. There is nothing characteristic about it. The medium is not liquefied. 



Agar-agar. — Linear cultures upon agar-agar present a translucent, circum- 

 scribed, grayish, smeary layer without characteristic appearances. 



Potato. — Upon potato a yellowish coating is formed, especially when the culture 

 is kept in the thermostat. 



Bouillon. — ^Bouillon made with or without peptone is clouded in twenty-four 

 hours. When the culture is allowed to stand for a couple of weeks without being 

 disturbed, a thin surface growth can be observed. 



Milk is an excellent culture-medium, but is not visibly changed by the growth 

 of these bacteria. Its reaction remains alkaline. 



Vital Resistance. — The bacillus is hardy. Smith found it vital after being dry 

 for four months. It ordinarily dies sooner, however, and difficulty may be ex- 

 perienced in keeping it in the laboratory for any length of time unless frequently 

 transplanted. The thermal death-point is S4°C., maintained for sixty minutes. 



Metabolic Products. — Gas Production. — The hog-cholera bacillus is a copious 

 gas-producer, capable of breaking up dextrose and lactose into CO2, H, and an 



* " Circular No. 41 of Bureau of Animal Industry," U. S. Dept. of Agriculture, 

 Washington, D. C. 



f'Bull. No. 72 of Bureau of Animal Industry," U. S. Dept. Agriculture, 

 Washington, D. C, 1905. 



f'Bull. No. 102 of Bureau of Animal Industry," U. S. Dept. Agriculture, 

 Washington, D. C, Jan. 18, 1908. 



§ "Reports of the Bureau of Animal Industry," 1885-91; and "Centralbl. f. 

 Bakt. u. Parasitenk.," March 2, 1891, Bd. ix, Nos. 8, 9, and 10. 



