74 



Microscopic preparations (Gram-staining -f- dilute carbol- 

 fuchsin) were made of all the sputa as well as the examinations 

 by cultivation. The microscopic picture and the results of 

 cultivation were far from always agreeing. In about half the 

 cases where Pfeiffer's bacillus was cultivated it could not 

 be observed with certainty in the microscopic preparations. 

 In many cases on the other hand numerous bacilli were found 

 microscopically with the appearance of Pfeiffer's bacillus but 

 they could not be cultivated. There were however many sputa 

 where the microscopic picture was quite „classical" (as in 

 figure I in Pfeiffer's (2) article) with dense masses of Pfeiffer's 

 bacilli enclosed in pieces of mucus, and where the bacilli could 

 also be cultivated in large numbers, sometimes even in pure 

 culture. The Pfeiffer's bacilli were nearly always extracellular. 



The lack of correspondence between the microscopic pic- 

 ture and the cultivation experiment m'ay perhaps be explained 

 in some cases as the consequence of too deep staining of the 

 preparation, so that Pfeiffer's bacillus did not stand out distinctly 

 enough. This factor however could presumably only be of 

 subordinate importance, because in those cases where Pfeiffer's 

 bacillus was found microscopically it was usually very distinct. 



On the other hand there is no doubt that Pfeiffer's bacillus 

 can often be demonstrated by cultivation even though it occurs 

 in too small numbers to assert itself in a direct microscopic 

 examination. 



A ^negative result on cultivation in spite of a positive di- 

 rect microscopic finding is undoubtedly in some cases due 

 to the fact that the bacilli were dead, because the sputum had 

 been kept too long. In other cases it may be caused by con- 

 fusion with other small Gram-negative bacteria. It must be 

 emphatically asserted that it is impossible by direct micro- 

 scopic examination of sputum' etc. to accurately distinguish 

 between Pfeiffer's bacillus and other small Gram-negative rods, 

 e. g. the whooping-cough bacillus. According to the expe- 

 rience of many authors Pfeiffer's bacillus in sputumi can also 

 easily be confused with Micrococcus catarrhalis. I have no 

 experience of this special point, but cannot deny it because 

 the sharp distinction between Gram-negative cocci and Gram L 

 negative rods, referred to above, may not always be so sim'ple 

 to demonstrate in sputa as in cultures. 



