RESPIRATORY APPARATUS. 117 



dition is acute (strangles). If the enlargement of the gland 

 is firm, cold and painless, it points to glanders, chronic catarrh, 

 tumors or hyperplasias [leucemia]. 



e. M o v a b i 1 i t y of the glands. If the irrita- 

 tion is chronic and attended with the formation of new con- 

 nective tissue, the process involves the environing tissue, form- 

 ing adhesions with its neighborhood. In acute purulent in- 

 flammation of the glands there develops in the vicinity, name- 

 ly, directly beneath the skin, an inflammatory edematous and 

 later a phlegmonous swelling. 



The extirpation of a diseased lymph gland is recommended 

 where glanders is suspected. Its object is the patho-anatomical 

 or bacteriological examination of the gland. The operation can 

 be performed on the standing animal when local anesthesia is 

 employed, and is not dangerous. 



VI. Cough. 



Cough is a sudden expulsion of air 

 from the lungs, following a deep inspira- 

 tion. The glottis is forcibly opened dur- 

 ing the act, causing a sound to be emitted. 

 By coughing accumulations of mucus are removed from the 

 bronchi, trachea or larynx. In animals cough is a reflex 

 action which can to a certain extent be suppressed. Al- 

 though it can be induced by irritation to many peripheral 

 nerves, as a rule it emanates from branches of the vagus nerve 

 in the respiratory apparatus. Most sensitive in this particular 

 is the superior laryngeal nerve, which is the sensory nerve of 

 the larynx, and the first three rings of the trachea. The mucous 

 membrane of the trachea is less sensitive, except at the bifur- 

 cation of the bronchi. The bronchi are just as easily irritated 

 as the larynx ; but cough can not be excited from 

 the parenchyma of the lungs. It can, however, 

 arise from the pleura when this organ is in a state of irritation. 

 Peripheral irritation is transmitted to the cough-center in the 



