5 14 PATHOGENIC BACTERIA. 



growth on agar-agar is similar to that of the colon bacil- 

 lus. The organism produces no indol. It coagulates milk 

 in a few days. Its fermentative powers have not been 

 sufficiently studied. It reduces litmus. Upon potato it 

 forms a yellowish-white, shining layer. 



The bacillus is pathogenic for mice, guinea-pigs, pig- 

 eons, lambs, and kids, but not for dogs, cats, rats, or 

 sparrows. The infection may be fatal, whether given 

 subcutaneously or intraperitoneally, for mice and guinea- 

 pigs, and may sometimes be fatal when the bacilli are 

 ingested. 



The bacilli are found scattered throughout the organs 

 in small groups, resembling those of the typhoid bacillus. 



At the autopsy a marked enteritis and swelling of the 

 lymphatic follicles and patches, and occasional hemor- 

 rhages, are found. The bacilli occur in the intestinal 

 contents. The spleen is somewhat enlarged. 



The bacillus is differentiated from the colon bacillus 

 chiefly by the absence of indol-production, by its ability 

 to produce infection when ingested, and by the fact that 

 it elaborates a toxic substance capable of producing sim- 

 ilar symptoms to those seen in the infection. 



It may be distinguished from the Bacillus lactis 

 aerogenes by its motility. It is with great difficulty 

 separable from certain water bacteria ; but as far as is 

 known its pathogenesis can be made use of for, assisting 

 in the differentiation in doubtful cases. 



Bacillus Dysentericus (Shiga 1 ). 



As the result of considerable investigation of the epi- 

 demic dysentery which has been very prevalent in Japan, 

 Shiga has come to the conclusion that a bacillus which 

 he calls the Bacillus dysentericus is the specific cause. 



The organism is a short rod, having morphological 

 characteristics identical with those of the typhoid and 

 colon bacilli. Like the typhoid bacillus, it is prone to 

 undergo involution. It is usually solitary, but may form 



1 Centralbl.f. Bakt. u. Parasitenk., 1S98, xxiv., Nos. 22-24. 



