446 BACILLUS WELCHII 



within twenty- four hours. In some cases the affection may be 

 confined to individual muscles, and resection of these has been 

 carried out, sometimes with success. Within a muscle, the 

 necrotic change may spread along individual fibres with great 

 rapidity, leaving others in relation to them unaffected. The 

 stages as described by M'JSTee and Shaw Dunn are as follows. 

 The bacilli spread with great rapidity along the interstitial tissue 

 of the muscle, and may be found beyond the actual site of 

 gangrene. They are present often in very large numbers and in 

 practically pure culture. The fibres thus surrounded become 

 somewhat swollen, altered in staining reaction, and separated 

 from the interstitial tissue by a zone of serous fluid, poor in 

 protein. The fibres then become completely necrosed, the 

 sarcolemma nuclei losing their staining reaction, and about this 

 time the fluid within the sarcolemma comes to contain the bacilli 

 in large numbers. There is then evolution of gas, and the 

 muscle substance becomes broken up and disintegrated, though 

 the transverse striation may persist for a considerable time 

 (Fig. 126). Finally the dead muscle may become invaded by 

 other organisms, and. become putrid and softened. Along with 

 these changes in the muscle there occur oedema and emphysema 

 in the interstitial and" subcutaneous connective tissue, while 'the 

 skin shows various kinds of discoloration, and the affected part 

 is swollen, tense, and gives crackling on palpation. 



To the naked eye the affected muscle is at first swollen and 

 pale and has lost its elasticity ; it soon assumes a brownish-red 

 colour, is beset with gas bubbles and is putty-like in consistence, 

 while later it becomes brownish yellow, greenish, or dark red. It 

 must be noted, however, that the bacillus does not cause the 

 ordinary changes of putrefaction. 



The essential feature is thus seen to be the extraordinary 

 extent and rapidity of the growth of the bacilli, which is 

 attended by evolution of gas, chiefly from the muscle carbo- 

 hydrates, and associated necrosis of muscle. Wright has found 

 that locally there is a fall in the anti-tryptic action of the serum 

 along with increased acidity, and he considers that the co- 

 existence of these factors favours the growth of the bacilli and 

 leads to their rapid spread. He also finds that in grave cases 

 there is a fall in the alkalinity of the blood — an acidsemia. 

 The spread of the bacilli is also attended by marked oedema, but 

 with practically no leucocyte reaction, unless when the spread is 

 becoming arrested or when it takes place around other organisms. 

 The growth of the bacilli is essentially local, but they may enter 

 the blood shortly before death, when they have been found 



