82 Roaring in Horses. 



mucous membrane, to endow this with sensation, and to the 

 crico-thyroid muscle, which it stimulates to contraction, 

 according to physiologists. But veterinary anatomists, and 

 especially Giinther, Franck, and Moeller, maintain that the 

 motor fibres are derived from the first cervical nerve. 

 Moeller satisfied himself of this by experimenting on horses 

 while they were in a state of narcosis. He exposed the 

 crico-thyroid muscle and laid bare the first cervical nerve, 

 and in stimulating the latter he found the former to con- 

 tract promptly and energetically ; when the finger was 

 passed into the larynx through an opening in the middle 

 crico-thyroid ligament, the contraction of the muscle and 

 approximation of the cricoid to the thyroid cartilage could 

 be distinctly felt every time the nerve was excited. When 

 the superior laryngeal nerve was stimulated, this muscle, 

 as well as the other muscles of the larynx, was quite 

 unaffected. It was clearly demonstrated that, in the horse 

 at least, the muscle receives its motor fibres from the first 

 cervical nerve, and not from the superior laryngeal. 

 Mceller also concluded from his experiments that the 

 latter nerve supplied, in addition to sensory filaments to 

 the larynx, trophic or nutrient filaments to the muscles. 

 In one experiment on a middle-aged horse in which respira- 

 tion was healthy, he divided the superior laryngeal of one 

 side, immediately before it entered the larynx. The animal 

 did not exhibit any signs of disturbance or Roaring subse- 

 quently, and when it was killed, six weeks afterwards, the 

 whole of the laryngeal muscles on the operated side were 

 in a state of marked atrophy, evidenced by their smaller 

 size and pallor. The other horse, also middle-aged, was free 

 from Roaring until shortly before it was killed, more than 

 four months after the operation, when advanced atrophy of 

 the muscles on the same side was noted. In the first case, 

 the superior laryngeal nerve was found to have undergone 

 degeneration, but the recurrent did not show any change. 

 Inferior Laryngeal or Recurrent Nerves. — These 



