146 



Pfeiffer's bacillus group, „irregular" forms were considerably 

 more in evidence than we should expect from the current 

 descriptions. On a closer study of the literature however it 

 appeared that practically all forms I have observed, had also 

 been described by other authors, but had not been generally 

 adopted. 



All my (circ.) 800 strains of Pfeiffer's bacillus were exami- 

 ned microscopically in smear preparations (Gram's method and 

 dilute carbol-fuchsin) at least once; a large number, probably 

 200—300, were examined 2 or 3 times; about 50 strains, 4 limes, 

 and 20 strains, 7 times. I have therefore a considerable num- 

 ber of microscopic slides of Pfeiffer's bacillus. Several hun- 

 dreds of the preparations were later on examined anew, in 

 order to get a collective impression of them. In spite of 

 continuously striving to establish definite criteria for the mor- 

 phology of Pfeiffer's bacillus I have been no more successful 

 than other investigators. My experience agrees entirely with 

 that reported on pp. 46—48, and it would serve no useful purpose 

 to give again a full presentation of the facts. A few points 

 only will be discussed. 



In order to give a general impression of the heterogeneous 

 picture that meets the eye, a small selection of microscopic 

 pictures is reproduced in plate 3. It is to be noticed parti- 

 cularly how greatly the microscopic picture of any one strain 

 can vary at different times and under different conditions. 



It need hardly be said that the unusual forms are more 

 numerous in the plate than in reality. 



As examples of pictures which are called typical both by myself 

 and by other authors, may be cited: I 37, I 53, and T 3. 



It will be noticed (e. g. in the various preparations of 

 I 14 and I 43) that the length of the bacilli is an extremely 

 labile character, the same strain varying considerably in this 

 respect without obvious cause. The thickness is more charac- 

 teristic (which however cannot be seen clearly in the plate). 

 Some strains consistently grow as slender rods, others as rods 

 of a considerably coarser appearance (e. g. GP 1, and GP 5), 

 but there is no fixed boundary between the two types. The 

 coarser forms are, on the whole, also more inclined to l>e 



