HAEMORRHAGIC INFARCTION OF THE LUNG. 159 



organs whose arteries an embolus could not have reached, without first 

 passing through the capillaries of another organ (for instance, infarc- 

 tion of the liver in thrombosis of a peripheral vein), it seems probable 

 that the embolus at first has been minute, but that during its course 

 through the system it has grown larger by accretion of fibrin. 4 The 

 very common occurrence of haemorrhagic infarctions after injuries of the 

 skull, where the diploe* have been penetrated, is simply due to the 

 gaping of the walls of the veins of this region, which, being adherent 

 to the tables of the skull, are prevented from collapsing, so that the 

 entrance of coagula into them of course is facilitated. 



In the hsemorrhagic infarctions which so often arise in diseases of 

 the heart, especially in cases of disease of the mitral valve, the existence 

 of clots in the arteries leading to them has long been known. But the 

 explanation generally has been that the escape of blood into the vesicles 

 and their interstices has compressed the capillaries and prevented the 

 outflow of blood from them, and that in consequence -of the stagnation 

 so produced the arterial contents have coagulated. This was formerly 

 my opinion, although I could not ignore that the extreme obstruction 

 of the blood in the pulmonary circulation, to which I ascribed the infarc- 

 tion in disease of the heart, did not at all account for the restriction of 

 the capillary haemorrhage to separate and abruptly-defined sections of 

 lung. I am now convinced that, in disease of the heart, haemorrhagic 

 infarction also arises from embolism, as has been proved by Rokitansky 

 and Gerhardt. The emboli which block the artery in disease of the 

 heart do not come from the greater circulation, like the emboli which 

 produce metastatic infarction, but from the right side of the heart, 

 especially from the right auricle, in which clots usually exist firmly en- 

 tangled in the trabeculae, and which are one of the results of the slug- 

 gishness of the circulation. If a particle of this clot be torn off and 

 washed away by the current of the blood, a branch of the pulmonary 

 artery becomes obstructed by it, and haemorrhagic infarction ensues. 

 The fibrinous coagula thus detached from cardiac thromboses are gen- 

 erally larger than those which come from the aortic circulation. We 

 thus find a very simple explanation of why the infarctions of heart-dis- 

 ease are more extensive than metastatic infarctions, as well as of why 

 the former are often found in the interior of the lung, near its roots, 

 while the latter are generally situated near the periphery. As very 

 minute particles also may be washed away from the thromboses of 

 the right heart, we likewise see how, besides the larger infarctions at the 

 roots, smaller peripheral ones also occur in heart-disease. 



The process still remains to be explained by which obstruction of an 

 afferent arterial branch produces capillary haemorrhage in the region 

 about the obstructed vessel, a process which, at the first glance, seems 



