128 PYAEMIA. 



then takes place in the same manner as in cases of intravascular 

 infection after thrombo-phlebitis. Ordinary pyogenic microbes 

 may and do cause pyaemia if they enter the blood attached to por- 

 tions of blood-clot, or other solid materials, which after they have 

 become impacted in bloodvessels by embolism, prepare the soil in 

 distant organs for their localization and multiplication. The 

 importance of thrombosis and embolism as factors in the causation 

 of pyaemia has been clearly established by clinical observation and 

 experimental research. Emboli may originate in the lymphatic 

 vessels when these are the seat of invasion by pyogenic microbes, 

 which, however, is very seldom the case. In chronic pyaemia, in 

 which multiple metastatic abscesses are formed, embolism takes no 

 essential part in the process, the microbes enter the circulation and 

 are brought in direct contact by mural implantation with the tissues 

 weakened by injury, or other debilitating causes. Experimental 

 research has shown conclusively that the introduction of pus- 

 microbes into the circulation is not necessarily or even usually 

 followed by pyaemia, and their accidental entrance in the course of 

 a suppurative inflammation is not always followed by serious con- 

 sequences. There can be no doubt that some pus-microbes reach 

 the circulation in nearly every case of suppuration, but their patho- 

 genic action is prevented, or neutralized, by an adequate resistance 

 on the part of the tissues with which they are brought in contact 

 and their rapid elimination through healthy excretory organs. A 

 limited number of pus-microbes injected into the circulation of a 

 healthy animal, or accidentally introduced into the blood of an other- 

 wise healthy person, are effectively disposed of by the white blood- 

 corpuscles. If, however, the same number of microbes are present 

 in combination with fragments of a blood-clot, the latter produce 

 such alterations in the tissues surrounding them as to prepare the 

 parts for their pyogenic action. The same happens if free pus- 

 microbes localize in a part the vitality of which has been previously 

 diminished by a trauma, or antecedent pathological changes, which 

 constitute a locus minoris resistenfice for the growth and reproduction 

 of pathogenic microorganisms. Pyaemia, therefore, must be looked 

 upon rather as a serious and fatal complication of suppurative 

 lesions rather than an independent specific disease. 



