19 



pointing out that already in 1830 he had observed the same 

 bacterium in preparations sent to him by M. Kirchner who has 

 even pictured one of these preparations in a communication 

 on his bacteriological investigations in influenza. Although 

 Pfeiffer's bacillus cannot be detected with absolute certainty 

 by the microscope alone this claim is in all probability correct; 

 but it is by no means proved that the bacterium at that time 

 had approximately the same wide distribution as when Pfeiffer 

 carried out his later investigations. As it must be assumed 

 that in the microscopic examination of sputum which has been 

 made by different observers a considerable number of times, 

 stains have frequently been employed which are suitable to 

 make Pfeiffer's bacillus visible (carbol-fuchsin, alkaline me- 

 thylene blue), it is difficult to imagine this organism could 

 have been overlooked if it occurred with the same regularity 

 and in the same abundance during the whole epidemic. 



As an example it may be mentioned that Weichselbaum (1) in 

 the early pari of the pandemic examined the expectoration of 21 

 influenza patients, for the most part uncomplicated cases. The 

 examination was made immediately after admission to hospital, the- 

 refore usually in the early stage of the disease. The sputum was 

 investigated shortly after it was coughed up, carbol-fuchsin being 

 used as a stain followed by slight decolourisation in alcohol. Although 

 all the conditions for the demonstration of Pfeiffer's bacillus seem 

 to have been fulfilled, Weichselbaum found almost exclusively, 

 bacteria having the appearance of Pneumococci, usually in large 

 numbers. 



It must however be admitted that, as is well known, a 

 phenomenon may be overlooked often in a surprising way 

 before it has been discovered; and it is feasible that Pfeiffer 

 (2) is right in maintaining that some of the earlier observers 

 may have seen his bacillus but looked upon it as a diplococcus 

 or streptococcus. 



As already observed it should be further noted that Pfeif- 

 fer's bacillus does not belong to the bacteria which stain most 

 easily. According to concordant statements by numerous au- 

 thors (Pfeiffer (2), Baumler, Kruse (1), Lindenthal, Jun- 

 dell, Beall, Wohi.will; Fildes, Baker, & Thompson, Prein 

 and others) it stains very badly, particularly in sputum and 



