CH. I] THE SCOPE OF THE ENQUIRY 7 



power was possessed by them all." (Andrewes and Horder, 

 1906.) 



In 1891 von Lingelsheim (ibid.) proposed a division into two 

 groups according to the length of chains formed r "strepto- 

 coccus brevis" and "streptococcus longus." Andrewes and 

 Horder (1906) with a view to further classification on the same 

 lines suggested the adoption of the terms brevissimus, brevis, 

 medius, longus, longissimus, conglomeratus. The quality of 

 cohesiveness by itself was, however, considered too trivial a 

 character to base a fundamental classification upon. 



The power of retaining stains was found to ofier no means 

 of dififerentiation, since all stained well. 



Minute differences in their mode of growth on different 

 media were found to be too inconstant to be of any value, 

 though Schottmiiller (quoted byMuir and Ritchie) attempted to 

 classifythe streptococci according to the appearance of colonies. 



Classification according to pathogenicity and virulence 

 appeared to have the advantage of being practical and signifi- 

 cant from a clinical standpoint. Virulence, however, was 

 likewise found to be an inconstant character, being lost and 

 regained with great readiness by these organisms. It was lost 

 after a few days on certain culture media. On the other hand, 

 after a few "passages" through a susceptible animal, a strepto- 

 coccus of feeble virulence might become intensely pathogenic. 

 Clinical experience confirms this variability in virulence. " One 

 and the same strain of streptococcus may at different stages 

 in its career produce now a rapidly fatal septicaemia, now a 

 spreading erysipelas, now a localised suppuration and now no 

 effect at all" (Andrewes and Horder, 1906), so that the degree 

 of virulence was an uncertain aid to classification. The 

 streptococcus erysipelatis, for instance, is no longer considered 

 on account of its virulence to be a distinct species from the 

 streptococcus pyogenes. 



Agglutination tests have not been found to be sufiiciently 

 specific. 



Marmorek's contention, therefore, for the unity of species of 

 the human streptococci continued to hold the field successfully 

 until the introduction of Gordon's tests. 



