56 Veterinary Medicine. 



pus being incapable of compression, presses the membrane out- 

 ward on the side in which the surrounding tissues are most loose 

 and least resistant, hence, usually, though not always, in the 

 direction of the skin ; the soft tissues become absorbed and re- 

 moved in the track of the advancing pus ; and, finally, the latter 

 reaches a free surface and escapes. Thus, an abscess usually 

 bursts through the skin, but also, at times, through a mucous 

 membrane into the lungs, bowels, etc. , or through a serous mem- 

 brane into chest, abdomen, etc. When an abscess is formed in 

 bone or dense fibrous tissues which press equally on all sides, it 

 may remain imprisoned for months and years after all inflamma- 

 tion has subsided, constituting an indolent or cold abscess. When 

 the imprisoned pus is inclosed by thick fibrous or resistant tissues 

 at all points but one, it will make its way along the narrow pas- 

 sage of yielding tissue, but as the resulting outlet is constricted, 

 long, and tortuous, the contents cannot readily escape through it 

 nor the walls of the abscess contract so as to expel the confined 

 pus, and the latter goes on forming and discharging through the 

 narrow outlet for months or years. This is a. fistula or sinus. 



Healing by Adhesion or First Intention. When a clean- 

 cut wound has the blood staunched and its lips brought together 

 without exposure to the air (or contact with pyogenic germs), 

 they adhere at once and heal without pus or almost any appreci- 

 able formation of new tissue. Here the lymph thrown out on 

 the cut surfaces agglutinates them, and the cells, multiplying, 

 form a thin layer of embryonic tissue which gradually develops 

 into a fibrous structure and repairs the breach without any per- 

 ceptible scar.^ 



Healing by Second Intention. Granulation. When a 

 wound has caused destruction of tissue, or when a simple incision 

 is left exposed to the air, the breach is filled up by new tissue 

 through the process known as granulation. The superficial layer 

 of lymph thrown out on the raw surface becomes oxidized and 

 degenerates into pus, while the deeper layers become solid, fibril- 

 lated, the seat of cell-growth, and are finally transformed into a 

 fibrous structure. New blood-vessels form in loops in the devel- 

 oping lymph and constitute the bright-red granulation-points 

 which cover the raw surface. The fibrous tissue into which the 

 lymph is transformed undergoes gradual contraction in develop, 

 ment, and thus, day by day, the edges of the adjacent healhty 



