210 NAVm ON THE HOESE. 



slioulder and chest, and opens out at the back of the forearm 

 at the point of the elbow, or it may open in front of the arm. 



Not imfrequently the broad processes of bone which rise up 

 from the back-bone to form the elevation of the withers, as well 

 as the shoulder-blade, may be attacked and wasted away by 

 the ulceration. 



Thus the disease advances, becoming worse and worse at 

 every stage of its destructive march, and the poor animal is 

 doomed to drag out a miserable existence, from wiiich there is 

 no escape until the weary powers of life succumb to the exhaust- 

 ins: rava2;es of the disease. 



Causes. — The immediate cause of fistula is an inflammation 

 starting at some point deeply seated in the part of the shoul- 

 der or withers where the disease occurs. The particular tissue 

 •or structure in which this inflammation begins has not been 

 -pointed out, whether it is the cellular tissue, the sheath of the 

 muscles, or the lymphatic vessels. (For a description of 

 " The Lymphatic Vessels," see the article under that head in 

 canother part of this work.) 



The causes which are universally given by authors as pro- 

 •ducing fistula are, the effects of bruises produced by strokes, 

 tight collars, striking the withers against beams in a low 

 stable, the biting of other horses, and especially the saddle 

 pushing too far forward. So long, generally, and often have 

 these causes been assigned, both by learned veterinarians and 

 the people generally, that it would seem like presumption to 

 ■question the correctness of this opinion. 



IN^evertheless, from a careful study of the nature of the dis- 

 ^ease, and many observations which I have made within the 

 past few years, I have become convinced that a far more im- 

 .portant cause is lurking in the dark, and plays a leading part 

 in the production of fistula and poll-evil. 



I regard poll-evil and fistula as of scrofulous origin. They 

 .are the local manifestation of disease existing in the con- 

 ,-stitution. It is well known to physicians that a large 



