354 PRINCIPLES OF VETERINARY SURGERY 



When an abscess is near a mucous cavity in the interior 

 of the body it progresses dow^nward, and frequently bursts 

 within the cavity. It is usual for pus to burst into the mouth, 

 into the pharynx, into the oesophagus, and into the rectum or 

 vagina. On the other hand it is exceptional to see it pene- 

 trating into the peritoneum. 



TERMINATION.— Whether the abscess bursts spon- 

 taneously or in consequence of a liberating incision, the flow 

 of pus is established, and the purulent secretion continues for 

 several days, if the interior of the pus cavity is not modified. 



PATHOLOGICAL ANATOMY.— The pathological 

 anatomy of an abscess comprises the study of two essential 

 parts: (i) The container, the sac previously described as the 

 "pyogenic membrane," and (2) the contents, the pus. 



I. Study of the Container — the Sac. — Since Delpech's 

 work the internal face of the pus sac has been described by 

 the term "pyogenic membrane." The cavity is sometimes 

 traversed by vessels and nerves that have resisted the dis- 

 solving action of the pus. The walls of the cavity which the 

 pyogenic membrane confines are tomentous and draped with 

 connective tissue cells in the course of proliferation. Ac- 

 cording to Le Tulle the pyogenic membrane resembles a 

 serous membrane in the state of irritation. It differs in no 

 way from inflammation of the peritoneum. It leads to an 

 excessive diapedesis. The pyogenic membrane is consti- 

 tuted at the expense of the connective tissue in which the 

 abscess is developed. Sometimes it leans against a muscle, 

 a tendon, an aponeurosis, a bone, a blood-vessel or a nerve, 

 which react more or less to the inflammation. 



The muscles offer little resistance to the dissolving ac- 

 tion of the microbian products, especially when they -are not 

 protected by a thick fibrous membrane. On the other hand 

 the aponeurosis and the tendons are not easily encroached 

 upon. Their close texture protects them against destruction 



