INTRODUCTION. 25 



present fluid accumulations occurs which constitute 

 CEdema when they are in areolar tissue, and Dropsy 

 (hydrops) when into cavities of various kinds. These may 

 take place apart from inflammation when an excess of 

 liquid material exists in the blood, or when the vessels 

 are over-distended. The former condition occurs in cases 

 of debility resulting from defective supply of nutritive 

 matter ; also certain poisonous materials aggravate their 

 effects by causing excessive fluidity of the vital fluid. An 

 illustration of the latter condition may be drawn from 

 general dropsy, whereby excessive distension of the veins 

 is relieved when any obstruction prevents return of the 

 blood to the right side of the heart. When the material 

 added to a part has a more solid character, it primarily 

 assumes the form of Coagulable Lymph. This is fibrinous 

 material which is deposited between tissue elements, ren- 

 dering the parts abnormally hard, or as bands extending 

 across cavities, also membranes lining them, and it will 

 be noticed in the straw-coloured liquid portion of the 

 serous effusion. When all active inflammatory change 

 has subsided, the lymph tends either to permanency or 

 to disappearance. It may be rendered permanent either 

 by organisation, when vessels shoot into it by ordinary 

 processes of development and it thus becomes vascular and 

 in process of time somewhat like areolar tissue, or by 

 calcareous deposition in its substance. The former change 

 occurs in the repairs of any large gap of living tissue which 

 has resulted from injury. It causes filling up of abscess 

 cavities, and of deep penetrating wounds, but is not 

 always so salutary ; for when it occurs in such a cavity as 

 the pleural sac, by uniting the lungs to the wall of the 

 chest, it may seriously impede respiration. Calcification is 

 the process which normally occurs in the hardening of lymph 

 between the fragments of a broken bone forming the mass 

 known as callus. Its appearance is not always desirable, 

 thus when it takes place in the walls of arteries it renders 

 them liable to rupture, and frequently its presence acts as an 

 impediment to movement, as when false anchylosis results 

 from the calcification of ligaments around joints. 



