1 68 SUPPURATION AND ALLIED CONDITIONS. 



is now generally held that erysipelas is produced by the 

 streptococcus pyogenes of a certain degree of virulence. It 

 must be noted, however, that erysipelas passes from patient 

 to patient as erysipelas, and purulent conditions due to 

 streptococci do not appear liable to be followed by erysipe- 

 las. On the other hand, the connection between erysipelas 

 and puerperal septicaemia is well established clinically. The 

 conditions which produce the special degree of virulence in 

 the streptococcus for the occurrence of erysipelas are not 

 yet fully known. 



In a case of erysipelas the streptococci are found in large 

 numbers in the lymphatics of the cutis and underlying tissues, 

 just beyond the swollen margin of the inflammatory area. 

 As the inflammation advances they gradually die out, and 

 after a time their extension at the periphery comes to an 

 end. In the affected area there are the usual changes 

 found in inflammation, great leucocytic emigration and 

 serous exudation with formation of fibrin at places, but 

 there is no suppurative liquefaction of the tissues. The 

 streptococci may extend to serous and synovial cavities and 

 set up inflammatory or suppurative change, peritonitis, 

 meningitis, and synovitis may thus be produced. 



Methods of Examination for Pyogenic Bacteria. These 

 are usually of a comparatively simple nature, and include 

 (i) microscopic examination, (2) the making of cultures. 



(1) The pus or other fluids should be examined micro- 

 scopically, first of all by means of film preparations in order 

 to determine the characters of the organisms present. The 

 films should be stained (a) by one of the ordinary solutions, 

 such as carbol-thionin blue (p. 98), or a saturated watery 

 solution of methylene-blue ; and (b) by Gram's method. 

 The use of the latter is of course of high importance as an 

 aid in the recognition. 



(2) As most of the pyogenic organisms grow readily on 

 the gelatine media at ordinary temperatures, pure cultures 

 can be readily obtained by the ordinary plate methods. 

 But in many cases the separation can much more frequently 

 be effected by the method of successive streaks on agar tubes 



