XI] BACILLI : SPECIFICALLY PATHOGENIC 221 



The cause of the disease is a bacillus, which in the affected 

 tissues of the pig appears, as a rule, as a short rod, often 

 constricted in the middle ; in fluid cultivations (broth) and 

 in animals (rabbits, mice) as a cyhndrical rod, singly or in 

 dumb-bells, occasionally growing to considerable length, and 

 forming longer or shorter chains ; but there can be always 

 found short forms almost like oval cocci, rods, and cylin- 

 drical bacilli. Cover-glass specimens and cultures of the 

 lung, spleen, lymph glands, and the sub-mucous tissue of the 

 affected intestine demonstrate the presence of the bacilli. 

 These bacilli are motile, though the motility is observed in 

 a minority ; in cultivations of broth, gelatine and Agar Agar 

 many of the bacilli are motile during the first few days, but 

 lose their motility later. 



In plate cultivations the colonies are first noticed as 

 greyish dots just visible to the eye already after twenty-four 

 hours ; in two or three days they are already conspicuous as 

 whitish, round, angular specks of about the size of a large pin's 

 head ; in transmitted light they appear brownish, granular. 

 In stab culture the stab of inoculation becomes marked as 

 a white line made up (when seen under a glass) of minute 

 globules closely placed side by side ; on the surface of the 

 stab is a small, irregularly outlined, whitish plate. In streak 

 culture the line of inoculation is occupied in a few days by 

 a grey band, knobbed or crenated in its outline. On Agar 

 the growth (at 37° C.) is a greyish-brown smeary film, 

 rapidly spreading over the surface of the Agar. In alkaline 

 broth at 37° C. uniform turbidity is produced ; after a few 

 days a voluminous greyish-white precipitate is noticed at 

 the bottom of the tube. No distinct pellicle is formed on 

 the surface. 



Inoculation of swine with cultures produces the disease, 

 but this does not lead to death, and such animals after re- 



