49 



fluenza and meningitis form indol, while those that do not 

 produce it occur in a wider distribution, hut usually in fewer 

 numbers than the indolpositive strains, in healthy people. 



Indol formation, as is well known, is a characteristic of 

 certain groups of Gram-negative bacteria (Coli etc., cholera 

 and various other vibrios, Proteus, and some of the dysentery 

 organisms). It might seem' possible therefore that indol-positive 

 and indol- negative Pfeiffer's bacilli had hitherto been wrongly 

 classed as the same bacterium, and that in the future they 

 must be rigidly separated from one another and be looked 

 upon as just as distinct as, for example, coli and typhoid ba- 

 cilli. Yabe writes I bus: „The absolute distinction between 

 strains of influenza bacilli is in the property of indol forma- 

 tion". It will later on be further discussed whether such a 

 view is justifiable. 



The first investigations of the action of Pfeiffer's bacillus on 

 carbohydrates and alcohols were made by Levinthal (1) 

 (1918) who, on cultivating it on the medium he devised with 

 the addition of litmus and lo/o of various substances (glucose, 

 laevulose, lactose, mannite, maltose), found a slight red co- 

 louration of the plates containing glucose only, all the other 

 substances being unacted upon. Messerschmidt, Hundeshagen, 

 & Scheer with the same technique obtained slight acid pro- 

 duction on the glucose plates, lactose, saccharose, and mannite 

 remaining untouched. Some strains fermented maltose and 

 dextrin. 



A number of authors (Stillman & Bourn, Rivers (2), Ri- 

 vers & Kohn, Povitzky & Denny, Thjotta, Malone (3)) have 

 devised more elaborate experiments, mostly with the use of 

 fluid media and they have found a more pronounced fermen- 

 tation of the different kinds of sugars than the foregoing 

 authors. But it must be pointed out that the power of Pfeif- 

 fer's bacillus to form acid cannot be compared with that of 

 the powerful acid-producers. The greatest degree of acidity 

 that can be produced in media containing glucose corresponds 

 to Ph' 6 to 6.4 (while Streptococcus for example can produce a 

 Ph- value of 5 and under). Furthermore the power of fer- 

 mentation is largely dependent upon the constitution of the 

 medium. Thus Rivers, in his first experiment in which he 



4 



