204 INFLAMMATION AND SUPPURATION 



saccharose and lactose, and sometimes the glucosides ; it produces an acid 

 reaction in milk but no clotting, and often reduces neutral-red. (b) The 

 streptococcus pyogenes, which is the most important pathogenic variety, and 

 has the characters described above, (c) The streptococcus salivarius, which 

 corresponds to the streptococcus brevis of the mouth, and which, as 

 regards fermentative action, seems to bear the same relation to the next 

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

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

 rarely innlin ; it clots milk and reduces neutral-red. (d) The strepto- 

 coccus anginosus, which corresponds with the so-called streptococcus 

 scarlatinas and the streptococcus conglomeratus. It ferments saccharose 

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

 haemolytic. It usually clots milk and does not grow on gelatin at; 20° C. 

 (e) The streptococcus foecalis, 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 haemolytic action. (/) The 

 sixth variety is the streptococcus e-quinus, which is common in the air and 

 dust of towns, and appears to be derived from horse dung. ' 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. 



Gordon has summarised as follows the chief features of the three most 

 important pathogenic streptococci : 



Str. pyogenes 

 Str. salivarius 

 Str. fetalis 



Neutral-Red. Eaffinose. , Mannite. 



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. Nevertheless 

 fermentative activity has been generally accepted as of great service in 

 classification, especially when the organisms have been recently isolated. 



Hemolysis (i-ide also p. 202). — Schottmuller has employed the appear- 

 ance of the colonies of streptococci on blood agar as a means of separating 

 varieties. The medium used by him consisted of two parts human blood 

 (rabbit blood may likewise be used) and five parts melted agar ; it is, 

 however, better to add the blood in the proportion of 5-10 per cent. He 

 distinguished the streptococcus longus or erysipelalis, which forms grey 

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

 riridans, a short-chained organism, which produces small green colonies 

 and very 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 



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

 September 1906, ii. 708, etc. 



