188 
PARALYSIS OF MUSCLES OF THE LARYNX. 
a quiet stall, and care taken that the air he pure and the temperature 
suitable. Caution must be observed in the use of morphine ; doses over 
8 grains often cause excitement. Clysters of chloral hydrate deserve 
preference. Preisnitz’s poultices, prepared by dipping poroplastic or thick 
felt in hot water, may be applied to the throat and neck, but must not be 
heavy, and may sometimes be preferably replaced by dry coverings. 
Myopathic paralysis of single muscles, or of groups of laryngeal 
muscles, is not known in animals, but may possibly occur. Neuropathic 
paralysis of the muscles of one side of the larynx (hemiplegia laryngis) 
is, however, very frequent in horses. The greater number, if not all the 
muscles of the larynx, which move the vocal cord are supplied by the 
recurrent nerve. Of late a second branch of the vagus has been 
recognised by Exner as a motor nerve to the larynx, but it has not yet 
been determined what influence it exerts'on the function of its muscles. 
From the construction of the larynx, as a valve opening outwards, it is 
clear that simultaneous paralysis of the constrictors and dilators must 
cause disturbed breathing during inspiration. Cramp of the constrictors 
alone might produce expiratory dyspnoea, but this very rarely occurs, for 
the expiratory muscles, assisted by abdominal pressure, are almost 
always sufficiently powerful to open the larynx, even against the con¬ 
strictors. It is otherwise in inspiration. Should the dilators of the 
larynx become paralysed, the arytenoid cartilage is forced towards the 
opening of the glottis by the instreaming air, and roaring results. With 
a few exceptions it is caused by paralysis of the recurrent nerve, and is 
so described in the text-books, as well as in another section of the 
present work. This paralysis is usually incurable, but the associated 
dyspnoea may be relieved either by removing the arytenoid cartilage, 
which has fallen below its position in the larynx, or by tracheotomy, 
thus providing a direct entrance for the air below the larynx. Both 
operations are fully described in sections 5 and 6 immediately hereafter. 
Boaring is also occasionally seen in other animals besides the horse; 
Utz and Ollmann found it in cows. Esser has described paralysis of the 
recurrent in a dog, and Holler noted the disease in two dogs. Holler 
also records several cases of double-sided paralysis of the larynx (diplegia 
laryngis) in horses and dogs producing severe inspiratory dyspnoea. 
After being walked for a short time, whistling or roaring was produced. 
The condition generally pursues a chronic course, and may he taken for 
chronic inflammation or tumour formation in the larynx. 
Diagnosis of roaring belongs to the province of special pathology, but 
the detection of double-sided paralysis of the larynx and its distinction 
from chronic inflammation or tumour formation may call for operative 
interference, or for the use of the rhino-laryngoscope. By using the 
latter instrument one sees clearly at the moment of inspiration that the 
