THE BACILLUS OF HOG CHOLERA 281 



and a loose sediment is soon formed at the bottom of the tube. On 

 potatoes it either forms a colorless, almost invisible, moist, slightly shiny 

 growth or one which may show a pronounced brownish tint. In milk 

 the reaction after some time becomes decidedly alkaline and the fat 

 of the medium undergoes a process of saponification, while, simul- 

 taneously, the fluid becomes opalescent, thick, and dark colored, but 

 not viscid. It sometimes requires from three to four weeks for all 

 these characteristic changes to become manifest. In Dunham's 

 peptone water the growth is not vigorous, indol is generally not formed, 

 but occasionally it may be formed. In the presence of glucose, the 

 bacillus, according to Moore, during the first day forms, from the 

 sugar in solution, from one-fourth to one-half of the total quantity 

 of gas. By the end of the second day gas formation is nearly com- 

 pleted. The total amount formed is composed of carbon dioxide and 

 hydrogen in the proportion of one volume of the former to two volumes 

 of the latter. In the presence of glucose the reaction becomes strongly- 

 acid and the development of the organism ceases. Lactose and cane 

 sugar (saccharose) are not fermented, and no gas is formed in their 

 presence. 



Resistance. The organism well resists drying out, and may remain 

 alive in dried-out tissues for several months. Alternate drying 

 and moistening, however, kills it rapidly; also exposure to direct 

 sunlight. It may remain alive for months in feces and moist soil; 

 also for a long time in ordinary water. According to Preisz, it is 

 killed at 50 C. in sixty-six hours, at 55 C. in one hour. It is killed 

 in ten minutes or less in 1 per cent, carbolic acid, -J per cent, hydro- 

 chloric acid, 2^ P er cent, sulphuric acid, 1 to 1000 corrosive sublimate, 

 and 1 per cent, milk of lime; 1 to 2000 formalin solution destroys it 

 in three hours. 



Animals Susceptible. It is pathogenic in natural infection to hogs 

 only, but mice are quite susceptible to artificial inoculation; guinea- 

 pigs and rabbits are less so. Very large doses injected intravenously 

 may kill horses and cattle. Pigs, when injected subcutaneously, 

 generally develop local lesions only, but some fatal cases after such 

 injections have been reported. 



The Etiology of Hog Cholera and the Relation of the Bacillus Cholerae 

 Suis to this Disease. Dorsett, Bolton, and McBryde, following up the 

 earlier work of de Schweinitz and Dorset, came to the conclusion 

 that pure cultures of the Bacillus cholerae suis injected subcutaneously 

 into hogs usually produced but slight disturbance, while a severe 

 illness frequently resulted after intravenous injections or feeding. 

 ~ state that the disease produced in this manner may present the 

 symptoms and lesions of acute hog cholera, but the contagiousness and 

 the infectiousness of the blood are absent, and hogs which have 



covered from such illness are not immune when exposed subse- 

 [uently to the natural disease. They, therefore, have demonstrated 



tat pure cultures possess a very considerable pathogenic power for 



