92 DISEASES OF THE HOESE. 



shoulder. The reason of this is easy of explanation, for 

 when these parts get injured, and suppurative action is set 

 up, the pus, instead of pointing to the outward surface, 

 burrows down in among the loose textures, and forms 

 sinuses or pipes, pointing in several directions. Pistula 

 differs from a simple abscess in this particular, and therefore 

 is difficult of cure. The pus secreted is nearly the same. 

 The pus in a simple abscess is secreted from, and is a liqui- 

 fication of, the surrounding tissue; but the pus of fistula is 

 secreted from the Avails of a fibrous sack, which is formed in 

 most cases of fistula. The fistula may be open or whole, 

 presenting a large swelling. 



Symptoms. Pain on pressure of the parts affected, fol- 

 lowed by heat, pain, and swelling, circumscribed in shape, 

 hard at first, and becoming soft and fluctuating upon 

 pitsssure by the finger — a sure indication of fluid within. 

 This swelling, from the firmness and integrity of the sack 

 and skin in which it is enclosed, does not break, nor yet 

 form sinuses that take on the character of an encysted 

 tumor, which does not break of its own accord, as simple 

 abscesses do. At other times, the fistulous tumor breaks 

 or opens in several places, and small holes discharge pus, 

 some to-day and none to-morrow. The day the discharge 

 is free, the pain and swelling is less. Among the pus will 

 be observed organized •matter similar to cheese, or in other 

 words, not uniform in thickness or appearance. This is a 

 disease that rarely ever gets well of its own efforts, 

 from the fact of the sore having a sack, which is only re- 

 moved by art; also, from the situation of fistula presenting 

 no depending opening for the outlet of the pus. 



Causes. Bruises, accidents, caries of the bones, (which 

 see,) inflammation of the bone, or any accident that will 

 cause a simple abscess, vv'ill cause fistula. 



