458 CATARRH. 



the direct inducing agent. In this way it is argued the arrest 

 of the secretion of the skin by exposure to cokl and damp 

 throws back into the blood a material which, either of itself 

 or by virtue of ulterior changes which it undergoes in the 

 body, acts as a toxic agent. The mucous membrane of the 

 respiratory tract seems to be the structure delegated to elimi- 

 nate this noxious material thrown into the system by the sus- 

 pension of the cutaneous action through the influence of cold. 

 The symptoms of catarrh are, in this light, regarded as depen- 

 dent on the vascular disturbance in the mucous membrane 

 incident to the eliminatory process ; and until the poison is 

 excreted this disturbance Avill remain, the purification of the 

 blood being immediately followed by relief from symptoms of 

 the derangement of the mucous membrane. 



2. Contact tvitk Diseased Animals. — In many instances this 

 is abundantly evident. 



The placing of healthy horses amongst those which are 

 suffering from common catarrh has often enough been followed 

 by the strangers becoming affected. The same can be said of 

 the converse experiment, that the placing of diseased animals 

 amongst healthy has often been followed b}- the appearance of 

 catarrh amongst the latter. 



Symptoms. — Two forms of catarrh have been described, the 

 simple and the chronic ; and although both are undoubtedly 

 encountered in the horse, the chronic form, sometimes termed 

 ozceiia, is rare as comjDared with the ordinary or benign. 



In common catarrh the symptoms may bo regarded as 

 (1) Local; (2) General. The local usually precede the general 

 if these latter are developed, which in the mildest forms they 

 are not. 



1. Local Syini'Aoms. — The earliest local sj'mptoms are 

 sneezing, redness and dryness of the nasal membrane, with a 

 discharge at first of a thin, serous, irritating character, suc- 

 ceeded, after some days, by a defluxion of a turbid, yellowish 

 colour, irregularly discharged. 



With these we have also redness of the conjunctival mem- 

 brane, with a copious discharge of tears, hanging of the head, 

 with heat over the frontal sinuses, and pain exhibited when 

 these are percussed. 



From the extent of the Schneiderian membrane, and its per- 



