RES PI R A TION 1 5 1 



the ass is both inspiratory and expiratory, nostrils and mouth 

 each taking a share in it. The ventricles of the larynx are large 

 in the horse and relatively still larger in the ass and mule ; they 

 act as resonators and allow of free vibration of the vocal cords. 

 According to Chauveau both ass and mule have the subepiglottic 

 sinus provided with a thin membrane capable of vibrating. In 

 the ox, sheep, and goat, the larynx is very simple, there are only 

 rudimentary vocal cords and no ventricles. The bellowing of 

 the ox and bleating of the sheep are expiratory efforts through 

 the mouth. The dog and cat have a larynx something like that 

 of the horse, but the ventricles are shallow ; the voice is produced 

 almost entirely through the mouth, though both growling and 

 purring may occur through the nostrils. 



Yawning is a deep, slow inspiration followed by a short ex- * 

 piration ; the air, even in the horse, is taken in by the mouth, 

 which is widely opened and the jaws crossed. 



Sneezing and Coughing are expiratory efforts. The former 

 occurs solely through the nose, and, excepting in the dog and 

 cat, is unaccompanied by the peculiar sound attending this act 

 in the human subject. If snuff be introduced into the nostrils 

 of the horse, a peculiar though well-known vibration of the 

 nostrils occurs as if the animal were blowing its nose, and this 

 is, in fact, what it accomplishes. It is an entirely nasal sound ; 

 the mouth takes no share in the act. Coughing occurs through 

 the mouth, the long palate in the horse being raised for the pur- 

 pose. Before coughing can occur the lungs must be filled with 

 air and the glottis closed ; a forcible expiration follows, the glottis 

 opens, and the air is expelled through the mouth. 



Hiccough is due to a sudden contraction of the diaphragm. 

 While the air is rushing into the lungs the glottis closes, and 

 the incoming air, striking the closed glottis, produces the sound. 

 The condition known as spasm of the diaphragm in the horse 

 is very different from a human hiccough, and ha$ been referred 

 to more fully on p. 152. 



Pathological. 



Pneumonia and Pleurisy in the horse are very common in early 

 life, and attended by a high mortality. The lungs and pleura, 

 separately or combined, may suffer a degree of inflammation varying 

 from small localised trouble to general and extensive inflammation 

 of the pleura and lungs. The whole of the lung tissue is never 

 affected ; even in the most severe cases of pneumonia there is some 

 breathing area available : the upper portion of both lungs generally 

 escapes. Effusion of fluid into the cavity of the thorax is a common 

 sequel to pleurisy in the horse. 



Both the above pathological conditions and their progress are diag- 

 nosed by auscultation and percussion : there are many departures from 

 the normal respiratory murmur, all of which have their significance. 



