INTRODUCTION. 37 



that a migration of red corpuscles (diapedesis) as well 

 as of white may occur from the vessels under certain 

 circumstances. Ha3morrhage is traumatic when due to 

 injury from without, and idiopathic when dependent 

 on intrinsic causes. Traumatic hsBmorrhage may be 

 due to injury of arteries, veins, heart, or capillaries, 

 and will be treated more at length under the heading 

 " Wounds." Idiopathic blood-extravasation may be 

 active or passive. 



Active Haemorrhage occurs in plethoric subjects, and is 

 preceded by active congestion. It results from a giving 

 way of the walls of capillary vessels, and the blood which 

 thus escapes is considerable in quantity, of a bright colour, 

 flows rapidly, and coagulates freely. Passive hemorrhage 

 generally depends upon debility and a disordered state of 

 the blood. It occurs in organs which have been weakened 

 by disease, and is often a symptom of some value. The 

 escape of blood tends to still further reduce the strength 

 of the patient. In certain blood disorders we find extra- 

 vasations of blood, either considerable infiltrations of 

 areolar tissue {hemorrhagic infarctions), or circumscribed 

 small patches of blood, petechia. Rupture of the wall 

 of a vessel, fracture of bone, and other lesions of a like 

 kind, are known in surgery as " Solutions of Continuity." 

 These give rise to disorder only when the continuity of 

 structure is essential to due performance of function ; 

 thus, a solution of continuity of horn may be present and 

 give rise to no inconvenience if the sensitive structures 

 beneath be not exposed to injury, as from compression. 

 Again, a simple incised wound, when the parts are brought 

 and maintained in contact, may become obliterated by 

 simple growth without the intervention of inflammation. 

 In bones continuity is essential to render them firm bases 

 of support. Fractures, therefore, interfere with function, 

 and must be carefully studied. The walls of blood-vessels 

 are constantly subjected to pressure by the contained 

 blood, when a solution of their continuity takes place, 

 therefore, HiEMORRHAGE results. 



In the present state of pathology we must admit the 



