872 



CLOSTRIDIUM 



clearly and unmistakably from other forms which have been described and named. 

 Some of these we have included in Table 57 and others are described at the end 

 of the chapter. Nevertheless, a large number of named forms remain, whose 

 place in the Clostridium group is still a matter of conjecture, as reference to the 

 monograph of Weinberg, Nativelle and Prevot (1937) will show. Prevot (1938) 

 rejects the genus Clostridium as incapable of covering all the anaerobic spore- 

 bearing bacilli, and proposes to create four families and nine genera, of which 

 Clostridium is one ; this classification in our opinion places too much weight on 

 morphological distinctions. The recognition of variation of the S — > R type and 

 detailed serological studies are helping to resolve some taxonomic difficulties, but 

 it is clear that a large number of Clostridia so far studied are antigenically hetero- 

 geneous, and that the variety of antigens, H, thermostable 0, labile 0, etc., is 

 probably as great as that displayed by the salmonellse. 



TABLE 56. 

 Giving a Classification of the Clostridia. 



(For classification see Weinberg and Seguin 1918, Report 1919, Heller 1921, and Hall 1922.) 



The grouping of the species within the genus Clostridium presents even greater 

 difficulties. Whether the primary division should be made on morphological 

 grounds — mainly on the shape and position of the spore — or on physiological 

 grounds — mainly on the relative activity of proteolytic and saccharolytic fermenta- 

 tion — must at the moment remain a matter of choice. We give in Table 57 (pp. 874, 

 875) the more important characters of the recognized species. We also append 

 a summarized description of each of a number of recognized sjDecies. It should 

 be noted that we have omitted to discuss Clostridia like CI. acetobutylicum (see 

 Chapters 3 and 6), which are of interest to the biochemist, and have made only 

 a brief reference to the Clostridia associated with the spoilage of canned foods. 

 Of particular interest is CI. thermosaccharolyticum (McClung 1935), which is an 

 apparently non-pathogenic thermophilic organism having an optimum temperature 



