INTRODUCTION. 27 



and the pus which is formed accumulates in the areolar 

 tissue, it exerts a solvent action upon the white fibrous 

 elements, and thus produces an Abscess. Ordinarily we 

 may observe that the inflammatory process, where less 

 acute at a distance from the centre of pus production, 

 causes exudation of lymph which limits the infiltration 

 of pus into the neighbouring tissues, and constitutes the 

 boundary of the abscess cavity, though forming no 

 distinct membrane. This firm limiting tissue gives 

 way with extension of suppuration, and at the same 

 time, the parts external to it, which previously were only 

 the seat of effusion of serum, have lymph exuded, and thus 

 in turn prevent infiltration of pus into the undiseased 

 areolar tissue. So, in puncturing a large or a small 

 deep-seated abscess we pierce first tissue with serous 

 effusion, then tissue with lymph exudation, and so arrive 

 at the abscess cavity. In chronic abscesses the inflam- 

 mation has subsided, as also has the serous effusion. 

 The lymph deposit has become organised to form a wall 

 of the abscess cavity in which has accumulated pus, often 

 of a foetid character, but sometimes broken up into the 

 liquid serous portion and the solid materials, the latter 

 being converted into more or less regularly rounded and 

 hardened masses of a curdy or cheesy character, which 

 are bathed by the fluid. These abscesses are sometimes 

 termed cold; they are seen in deep-seated positions 

 where the inflammation has been only moderate in 

 intensity. 



Purulent Infiltration occurs when collections of pus 

 are allowed to enter the areolar tissue of an organ, either 

 by non-deposition of lymph circumscribing the seat of pus 

 formation and leading to abscess, or by the giving way of 

 only a thin layer of this material. It is especially liable 

 to occur in the less active forms of inflammation, and in 

 organs with a considerable amount of areolar tissue ; thus, 

 it may be observed in scrofulous disease of the lungs, and 

 leads to rapid spread of diseased action. Sometimes pus 

 is found in serous cavities. When the pleura is the seat 

 of this the disease is termed eyajpyema. This state seldom. 



