^0 Roaring in Horses, 



approximation occurs during swallowing, and in some other 

 musculai' movements in this region. 



The " ventricles of the larynx " or " Morgagni's ventricles" 

 (Figs. 1 , c ; 3, /^ ; 4, e e ; 5, 6) are two somewhat capacious 

 sacs or pouches of mucous membrane, one on each side of 

 the cavity of the organ, the entrance to them being rather 

 wide, and lying between the ventricular bands and vocal 

 cords. These sacs are oblong in shape, and pass out between 

 the upper and lower portions of the thyro-arytsenoid muscles. 

 They extend only a short distance forward towards the 

 origin of the vocal cords, but dip down to the base of these, 

 and are continued behind the processi vocales of the aryt^e- 

 noid cartilages. They are very dilatable, have numerous 

 mucous glands, and permit free movements and vibrations 

 of the vocal cords. 



Physiology of the Larynx. 



The essential function of the horse's larynx is related to 

 respiration, and in a lesser degree to deglutition, as well as 

 to coughing, sneezing, deftecation, and other expulsive 

 efforts of a voluntary or reflex kind ; it is rarely required 

 for phonation or voice-production, which is one of its chief 

 uses in mankind. 



It has been already stated that the larynx is always more 

 or less open, for the passage of air to and from the lungs, 

 except during the acts above-mentioned, the degree of 

 patency depending upon the inspiratory effort. During 

 respiration, the arytienoid cartilages and vocal cords move 

 in a combined and rhythmical manner. In inspiration, by 

 the action of the abductor (posterior crico-arytaenoid) 

 muscles, we have seen that these cartilages are drawn 

 upwards and outwards, the cords, being attached to their 

 anterior extremity, passing in the same direction towards 

 the sides of the thyroid cartilage, against which they lie 

 flat when inspiration is deep. By this movement, the 

 middle space {rima glottidis) is enlarged to a degree 



