158 INFECTIONS OF THE DIGESTIVE TRACT 



may possibly have been done by nature and may 

 perhaps be still in progress. The existence of bacteria 

 intermediate between colon bacilli and typhoid bacilli - 

 the paratyphoid and paracolon bacteria is now es- 

 tablished, and the fact that there are these transitional 

 forms suggests that they may have been descended 

 from a common ancestor through successive slow modi- 

 fications. 1 



1 The studies of Doebert ("Die verwandtschaftlichen Bezie- 

 hungen zwischen den Bacillus faecalis alkaligenes und dem Ty- 

 phusbazillus," Archiv f. Hyg., lii, p. 70, 1905) indicate that 

 there exists a close resemblance between the bacillus of typhoid 

 fever and Petruschky's B. fcBcalis alcaligenes. A culture of the 

 latter organism furnished by Petruschky rendered litmus milk 

 blue in twenty-four hours, forming a pellicle on the surface of the 

 milk, and on potato gave a yellowish brown growth in one day. 

 With typhoid serum the organism agglutinated in 1 : 800. It is 

 stated that it was easy to modify the organism of Petruschky by 

 passing it through guinea-pigs so that it acquired the cultural 

 characters of the true typhoid bacilli. The organism modified by 

 Doebert experimentally by passage through guinea-pigs was not 

 agglutinated by the serum from guinea-pigs in 1 : 100, but was 

 agglutinated by typhoid serum in a dilution of 1 : 15,000. An- 

 other strain of B. fcecalis alcaligenes studied by Doebert could not 

 be converted in this manner into an organism so closely resembling 

 the typhoid bacillus by means of passage through animals. 



There appears to be little doubt that B. fcecalis alcaligenes is 

 sometimes responsible for the occurrence of a febrile disease at 

 present indistinguishable from mild forms of typhoid fever on 

 purely clinical grounds. Though closely related to the bacillus 

 of typhoid fever, it appears proper to regard the bacillus of Pe- 

 truschky as a distinct bacterium. (For details as to the distinction 

 of B. fcecalis alcaligenes and B, typhi see Piorkowski, "Zur Differ- 

 enzierung der Typhusbacillus und Bacillus fsecalis alkaligenes," 

 CentralbL /. Bakt., I Abt., Orig., xl, p. 437, 1905-06.) It seems 

 most reasonable to look upon B. fcecalis alcaligenes as a variant of 

 the typhoid bacillus which has lest the capacity to act fermenta- 

 tively on dextrose. Something might be said in favor of regarding 



