226 A MANUAL OF BACTERIOLOGY 



and in addition by the formation of abscesses in various 

 situations. These arise usually from suppurative phlebitis 

 with the formation of septic emboli and thrombi. The 

 sequence of events, according to Cheyne, 1 is (a) phlebitis 

 in direct connection with the wound ; (b) a thrombus 

 impregnated with micro-organisms is formed in the vein ; 

 (c) this softens and disintegrates, and particles or emboli 

 are carried to distant parts ; (d) these lodge in the 

 capillaries, with the formation of infarctions and abscesses. 

 Suppurative pylephlebitis is a pyaemia affecting the portal 

 system of vessels. As regards the so-called chronic 

 pyaemia or multiple abscesses, Cheyne considers that it 

 differs from true pyaemia in that embolism plays no part. 

 Organisms gain access to the blood- stream, settle in any 

 spot where the vitality of the tissues is depressed, grow 

 and multiply, and there produce an abscess. 



The mere presence of micro-organisms does not always 

 suffice, however, for they may be present without pro- 

 ducing suppuration ; and the same organism, for example, 

 the Streptococcus pyogems, may at one time produce a 

 localised abscess, at another diffuse cellulitis. and at a 

 third pyaemia ; a number of factors control and modify 

 the occurrence and the particular form of septic disease. 



As already mentioned (p. 199), many micro-organisms 

 when injected into the blood-stream are rapidly disposed 

 of ; so when moderate quantities of the Micrococcus 

 pyogenes are injected into the circulation of a rabbit, 

 abscesses, as a rule, form only in the kidney. If, however, 

 the organisms be attached to gross particles, so that they 

 cannot pass through the capillaries, embolism occurs and 

 abscesses form about the embolic foci. The virulence of 

 .the infecting organism, which varies much, is another factor 

 of great importance. The effect of inflammation and 

 injury in making a part " susceptible " is also very marked. 

 1 Loc. cit. p. 881. 



