496 APPLICATION OF METHODS OF BACTERIOLOGY 



microscopic examination of materials from various sources, 

 including the pharynx, one occasionally encounters micro- 

 organisms whose morphology is so like that of the genuine 

 bacterium diphtheriae as to create suspicion, and yet they 

 are at the same time sufficiently unlike it to make one cau- 

 tious in forming an opinion as to their real nature. 



Variations. The pleomorphism of bacillus diphtherise, 

 together with its many irregularities in physiological func- 

 tion, render some satisfactory grouping or typing, highly 

 desirable. Numerous efforts in this direction have been 

 made but none as yet with entirely satisfactory results. 



The efforts to group the varieties of this organism accord- 

 ing to minute peculiarities of form, structure and staining 

 peculiarities and to attribute to one such group pathogenic 

 powers and to another no such power, involves far too 

 much that is subjective 'to be of permanent value, in fact 

 it is in most instances misleading. 



The grouping or typing according to certain functional 

 characteristics, such as zymogenesis, has been of use, but it 

 still leaves something to be desired. 



The grouping in accordance with pathogenic potency is 

 surrounded by too many complications to be routinely 

 useful. 



The efforts to group the large number of varieties of this 

 species, though specific' agglutinating reactions, as has 

 been done with pneumococci, streptococci, meningococci 

 and certain other organisms, though not far advanced, holds 

 out, nevertheless, much promise of success. Up to the 

 present the results of the efforts may be summarized about 

 as follows: 



1. There is apparently no constant relationship between 

 morphology and antigenic power. 



