J94 CHAPTER 20. 



If there is a free depending exit for the matter, there is no need of an 

 abscess ; but it often happens that there is no such exit, and conse- 

 quently the matter cannot get out. In such cases nature makes provi- 

 sion for its temporary retention and ultimate expulsion by means of an 

 abscess. If the pus were to float about free among the tissues it might 

 affect them very injuriously, and might act as a poison, or at least as a 

 foreign body. 



To obviate this, nature, by means of the fibres of the lymph surround- 

 ing the outer circle of the inflamed part, forms a membrane with a 

 smooth, villous, secreting surface. In this sac the pus is retained, in- 

 stead of floating about among the tissues. The contained pus, however, 

 gradually seeks to reach the surface of the skin or a mucous membrane ; 

 and then by means of pressure, which causes ulceration and rupture of 

 the tissues between the cyst and the external air, the pus is evacuated. 

 The submaxillary tumour in strangles is a very good example of an 

 abscess. 



Sometimes the abscess is not able thus easily to discharge its contents, 

 but a communication is established with the surface by means of a 

 narrow canal with walls of a membrane similar to that enclosing the 

 abscess. This canal is called a Sinus. When the sinus is constricted at 

 its external orifice, it is called a Fistula. In cases of long standing the 

 walls of the sinus often secrete a thin,, serous, and sometimes offensive 

 secretion. 



The formation of an abscess, especially if acute, is often accompanied 

 with fever. The part is painful, red, and swollen. Indications of relief 

 are given by the tumour becoming softer and beginning to point ; and 

 at the same time fluctuation may be felt in it. Ultimately the integu- 

 ment ulcerates, and the pus is discharged. As soon as suppuration 

 occurs, there is abatement of the fever. 



396. Treatment of an Abscess. 



The treatment required is local. Herein often lies a difficulty. In 

 very many cases we can do nothing, because the part, as for instance in 

 the lungs, cannot be examined. Improvement in the condition of the 

 animal will, however, assist in bringing about the curative process. 



When the parts can be reached, the best plan is to open the abscess at 

 its most depending point, as soon as we judge by the softening of the 

 external membrane and by the sensation of pulsation or fluctuation that 

 it is ripe or nearly ready to burst ; or in the case of a chronic abscess it 

 may be necessary to open it to the bottom and to apply stimulants. If 

 the abscess is internal, we must wait until by the operation of nature it 

 bursts. 



If the suppurative matter has burrowed and formed sinuses, it will be 

 necessary to afford it a free exit ; and in very many cases it will be 

 necessary to cut the walls of the sinus completely through to the bottom, 

 so as to convert it into an ordinary incised wound, which may be healed 

 by granulation. 



