Diagnosis. Projinosis. 735 



and without inspection of tlie interior of the larynx one can 

 diagnose with certainty only some stenosis of the npper air 

 passages or larynx, generally termed roaring, but only a con- 

 ditional opinion can be expressed as to whether paralysis of 

 the recurrent nerve is the cause of the condition. According 

 to Cadeac and Fleming, whistling and roaring are caused by 

 paralysis of the recurrent nerve in 95 to 99 per cent of cases. 



Whistling and roaring during work may be due to stenosis 

 of the upper air passages from other causes. Neoplasms in 

 front of or in the larynx (tumor-like growths of a glanderous 

 nature, Dexler), dilatation of the guttural pouches, curvature 

 of the trachea, proliferations of the laryngeal mucous mem- 

 brane, may cause exactly similar symptoms, as may also ste- 

 nosis of the pharynx or posterior portions of the nasal fossas. 

 While the last named type of stenosis, and that due to curva- 

 ture of the trachea or larynx can be detected by careful exam- 

 ination of the exterior, this is not so in the case of stenosis of 

 the larynx. 



Stenosis of the larynx may occur in acute diseases, and 

 especially in acute edema of the glottis, or owing to acute 

 swelling of the mucous membrane. If the stenosis is only 

 moderate, roaring and dyspnea are observed during work only. 

 In such cases a diagnosis may be based on the history of the 

 case, the course of the disease, and especially the alternation 

 of exacerbations with improvements. 



Temporary paralysis of the recurrent can only be differ- 

 entiated from the chronic progressive form of the disease by 

 observation of the course taken by the process. 



The best method of testing a horse as to whether he is a roarer is to gallop 

 it in a circle on a lunging rein with its head held in and turned slightly to the 

 right. If results are not obtained, saddle horses may be galloped or ridden at 

 a fast trot and harness horses may be driven. If possible the ground shouhl be 

 Boft in order to cause violent inspirations and to avoid masking the sound by the 

 noise made by the cart or by the horse's feet. The head should be held well in 

 because this puts the muscles of the larynx in an unfavorable position (Giinther) 

 and consequently the noise is appreciable earlier. In view of the fact that under 

 Buch conditions many sound horses breathe noisily in fast paces, particular atten- 

 tion must be paid to the nature of the sound produced. It is only a high-pitched 

 whistle or a deep roar that indicates stenosis. A sound of this type is never pro- 

 duced by a sound horse. 



Further investigations are necessary to decide how often individual muscles of 

 the larynx are paralysed, and whether the nmscles other than the dilators are 

 sometimes alone involved. Thomassen's observation that many horses show dis- 

 turbance of neighing before there is any whistling appears to indicate that the 

 constrictors only may be affected for a time. 



Prognosis. Laryngeal paralysis due to some infectious 

 disease or intoxication not rarely disappears within some 

 weeks or months, while the apparently spontaneous disease, or 

 paralysis due to compression of the nerve is constantly pro- 

 gressive and is associated with a decreased power of work or 

 loss in value. The question as to the extent to which the dis- 

 ease affects the animal's capabilities solely depends upon the 

 type of work done. Whereas, a saddle horse is rendered use- 



