CHAPTER YIII. 

 HEMORRHAGE. 



HiEMORRHAGE is the flow of blood from its natural 

 channels, resulting from a breach or other defect in an artery, 

 a vein, or the capillaries. It occurs in two .distinct forms: — 

 (i) Haemorrhage by rhexis or division of the vessel wall 

 and (2) haemorrhage by diapedesis, or oozing of the blood 

 from, the vessels, without any perceptible breach in their 

 continuity. 



1. Haemorrhage by rhexis (diabrosis) occurs from 

 breaches in the walls of arteries, veins or capillaries, or in the 

 heart itself. It may be caused by any disease, any injury 

 or any increase in the blood pressxire that is capable of per- 

 forating the blood vessels, or capillaries. The degenerative 

 changes in the walls of blood vessels most likely to cause 

 haemorrhage are aneurisms, atheromata, arterial sclerosis, 

 abscesses, malignant neoplasms and fatty degeneration. 

 These morbid conditions often act as predisposing causes 

 when the blood pressure is markedly increased, or when the 

 diseased part is subjected to some form of indirect violence, 

 such as strain, traction, etc. The most common cause of 

 haemorrhage, however, is traumatism, which produces a di- 

 rect mechanical solution of continuity in the blood channel. 



2. Haemorrhage by diapedesis is synonymous with 

 haemorrhagic exudation. It consists of a transudation of 

 somewhat limited quantities of blood into the tissues of a 

 circumscribed area. It is called petechial when the blood 

 gathers in a number of small spots under epithelial tissues. 

 The spots are called petechiae. It is designated as ecchy- 



187 



