200 INFECTIONS OF THE DIGESTIVE TRACT 



Passini 1 obtained positive results in some of his cases 

 not only with homologous strains but also with unre- 

 lated ones. In this case, however, the agglutinative 

 action of the immune serum was less marked than in the 

 case of the sera obtained by Werner. It is evident that 

 there is still much to be learned in relation to the im- 

 munizing action of B. aerogenes capsulatus and that such 

 an action hi man may yet be discovered. 



The organisms we have classed as belonging to the 

 B. aerogenes capsulatus type are large, plump, usually 

 straight bacilli, which as they occur in the faeces, can 

 usually be shown to be provided with a capsule. Organ- 

 isms which have developed in a living or dead rabbit 

 always acquire capsules. The organisms occur very 

 often in pairs, end to end, sometimes singly ; sometimes 

 in chains; sometimes as threads, which may be nearly 

 straight or sharply bent on themselves. The ends of 

 adjacent bacilli are slightly rounded or squared, though 

 not so sharply squared as in the case of anthrax bacilli. 

 They are immobile when viewed in hanging drops. 

 Spore formation occurs with difficulty ; i.e. chiefly under 

 very special conditions, such as on a medium containing 

 blood serum or within the body of an animal. Occa- 

 sionally spore formation is seen in blood-agar colonies, 

 the bacilli from which in other respects conform to the 

 characters of B. aerogenes capsulatus. On sugar bouillon 

 gas formation is abundant and rapid, twice as much gas 

 (or more) being formed in twenty-four hours as is usually 



1 "Variabilitat der Bakterien und Agglutinatinosphanomen," 

 Munch, med. Wochenschr., li, p. 1283, 1904. 



