126 PRACTICE OP EQUINE MEDICINE. 



What is the aetiology ? 



It is much more rare than the acute form; it may follow an 

 acute attack, or it may be caused by nasal polypi, or from irritating 

 substances in the nose; also from decayed teeth, or it may depend 

 on ulcerations of glanders, or an inflammation of the mucous mem- 

 brane of the sinuses, or an accumulation of pus, or be associated 

 with leucocythsemia, anaemia, or may be of specific origin. 



What is the pathology ? 



The mucous membrane is of a dark-red color, at times grayish, 

 is thickened more or less, the veins are often dilated and varicose 

 and forming polypoid enlargements, or there may be ulceration of 

 the structures with a more or less loss of substance. 



The discharge is thick, of a greenish-yellow color, and often 

 fetid. The mucus often dries on the septum or around the nostrils 

 and forms crusts. These crusts often become dislodged in the act 

 of sneezing, snorting, or coughing. The amount of discharge 

 varies. 



What is the semiology ? 



The disease is very often unilateral, and, if so, we should be 

 suspicious of glanders, which is very often difficult to differentiate, 

 except by the use of malleine. 



The mucous membranes of the nose are very frequently of a 

 bluish tint, with enlarged veins filled with blood. At times, the 

 surface of the mucous membranes presents erosions. 



There is a discharge, which varies in consistency and color; 

 in some cases it is thin and watery, while in others it is opaque 

 and contains broken-down material. 



If the head is down near the ground or the animal is in mo- 

 tion, there is an increase in the amount of discharge. 



In some cases there is swelling of the intermaxillary glands. 



How is the disease diagnosed and what is the differen- 

 tial diagnosis? 



We should first try to get the cause — that is, the disease to 

 which it is secondary. 



The diagnosis is made by the history of the case, the discharge 

 having continued for a length of time; the color of the mucous 

 membrane and the character of the discharge. 



If the discharge is due to a decayed tooth, there will be a dis- 



