170 



m-:terix.\u\' rAi'iioLoGV. 



an engorgement of the subsurface vessels and the related areo- 

 lar tissue is infiltrated with inflammatory exudate. 



Subsurface suppuration may be circumscribed or diffuse. 

 Suppurative centers become circumscribed first by a dense wall 

 of leucocytes and later by a fibrous capsule. The capsule is m 

 nearlv all cases denser on the side next to the more important 

 tissue. Fibroblasts that form the circumscribing fibrous capsule 

 are probablv the wandering connective tissue cells or their 

 progeny. The collection of pus in tissues, or lymph spaces, and 

 as considered by some in bodv cavities, constitutes an abscess. 

 The circumscril)ed pus may. by solvent action of its ferments, 



Fiy. 1112. — .Suppurativa Nepl»ritiH. 



Normal kiiln'\- tuliiih'. b. .Suiiiauati\-.j lueus suiinuml' d \>y kidn.-y tissue 



dissdh'e or erode the limiting structure (cells or capsule), and be 

 liberated ; the erosive action being in the direction of the least 

 resistance. In this way a surface discharge is effected. The 

 channel of exit of the pus may persist and Ijecome circumscribed 

 bv a fibrous wall, thus forming a fistulous tract. If the pus 

 cavity is completely evacuated bv surgical interference or other- 

 wise, and the cause removed, the surrounding tissue will, by 

 proliferation, fill the space previously occupied bv the pus. The 

 pus in an abscess nla^' be absorbed and the destroyed tissue be 

 re])laced by regeneration. If the cajjsule is exceedingly dense 

 the contained pus may become caseated and calcified. 



Abscesses may be classified as superficial and deep; primary 

 (ir metastatic (metastatic aljscesses may or may not Ix; embolic), 

 simple or multiple, suljfascial and intermuscular. A hot abscess 



