VARIETIES OF STREPTOCOCCI 213 



variety as the streptococcus mitis does to the streptococcus pyogenes. It 

 ferments saccharose, lactose, and raffinose, sometimes the glucosides and 

 rarely inulin ; it clots milk and reduces neutral-red, (d) The strepto- 

 coccus anginosus, which corresponds with the so-called streptococcus 

 scarlatinse and the streptococcus conglomeratus. It ferments saccharose 

 and lactose, and sometimes raffinose, reduces. neutral-red, and is actively 

 hsemolytic. It usually clots milk and does not grow on gelatin at 20 C. 

 (e) The streptococcus fcecalis, a short-chained form, which abounds in the 

 intestine and which has great fermentative activity, and reacts positively 

 to all Gordon's tests with the exception of raffinose and inulin. It forms 

 sulphuretted hydrogen, and is devoid of hsemolytic action. (/) The 

 sixth variety is the streptococcus eguinus, which is common in the air and 

 dust of towns, and appears to be derived from horse dung. 1 It ferments 

 saccharose and the two glucosides, and forms little or no acid in milk. 

 It is, however, to be noted that to all these varieties variants are met 

 with. 



Ainley Walker in studying this question, however, has found that 

 various strains of streptococci show considerable variability in their 

 fermentative powers when kept for some time under ordinary conditions 

 of growth, and Beattie and Yates have observed corresponding changes 

 when streptococci are passed through the animal body. It accordingly 

 does not seem justifiable to claim that the fermentative activity of a 

 given streptococcus is a stable property, though fermentation tests may 

 be of service in the classification of streptococci when freshly cultivated. 



Schottmiiller has employed the appearance of the colonies of strepto- 

 cocci on blood agar as a means of separating varieties, the medium used 

 consisting of two parts human blood and five parts melted agar. He 

 distinguishes the streptococcus longus or erysipelatis, which forms grey 

 colonies and has a marked hsemolytic action ; a streptococcus mitior or 

 viridans, a short-chained organism, whicli produces small green colonies 

 and A r ery little haemolysis ; and a streptococcus mucosus encapsulatus, 

 which, as its name indicates, shows well-marked capsules and produces 

 colonies which have a slimy consistence. Mandelbaum adds to these the 

 streptococcus saprojjhyticus, which is without hsemolytic action. It should 

 be noted that on blood agar the pneumococcus forms green colonies and 

 produces little or no haemolysis. Levy finds that a 2 '5 per cent, solu- 

 tion of taurocholate of sodium in bouillon produces complete bacterio- 

 lysis of the pneumococcus and the streptococcus mucosus, while it has 

 no effect on other varieties of streptococcus. He considers the strepto- 

 coccus mucosus to be a variety of pneumococcus. The general statement 

 may be made that most of the streptococci from lesions in the human 

 subject have haemolytic action, but that occasionally streptococci without 

 this property are found even in severe infections. 



It will be thus seen from this account that the streptococcus 

 pyogenes as described above is the organism most frequently 

 associated with the pathogenic processes, and that short-chained 

 forms are common saprophytes in the human body, although 

 they may be associated with conditions of disease ; these may 

 be provisionally classified according to their fermentative activity 



1 For further details, reference must be made to the original papers, Lancet, 

 September 1906, ii. 708, etc. 



