LESSON XXVIII 



RESPIRATION (Continued) 



NERVOUS REGULATION OF RESPIRATION 



1. Accessory Movements of Respiration. Anesthetize a mammal 

 and continue the anesthesia throughout the following experiments : 

 Perform tracheotomy. Observe the movements of the facial muscles 

 and note especially the changes in the size of the nostrils during inspira- 

 tion and expiration. Render these movements more conspicuous by 

 temporarily occluding the rubber tube attached to the tracheal cannula. 



2. Self-regulation of Respiration. Attach a pair of bellows to the 

 tracheal cannula. Suddenly inflate the lungs. Note the expiratory 

 effort immediately ensuing. Suddenly deflate the lungs and observe 

 that the animal makes an immediate effort at inspiration. Explain 

 these results upon the basis of the self-regulatory function of the vagi 

 nerves. 



3. The Trigeminal and Glossopharyngeal Nerves. Apply a stetho- 

 graph to the chest of this animal and register the respiratory movements 

 upon the paper of a slowly revolving kymograph. Stimulate the nasal 

 lining by means of a small plug of cotton attached to the end of a stick 

 of wood. Note the resultant inhibition of respiration and forced ex- 

 piratory efforts (act of sneezing). Enumerate the different nervous 

 parts involved in this reflex. Stimulate the lining of the fauces and 

 pharynx in the same manner, producing thereby those modifications of 

 respiration which constitute the act of coughing. Trace the course of 

 this reflex. 



4. The Larynx. Make a median incision through the skin covering 

 the -region of the larynx and hyoid bone. Ligate the vein crossing the 

 larynx and reflect the skin. Identify the thyroid and cricoid cartilages. 

 Note the movability of the larynx and trachea. Isolate the superior 

 and inferior laryngeal branches of the vagus on both sides, and place 

 them in loose silk ligatures. 



Annotation. The superior laryngeal nerve pursues a course transversely across 

 from the vagus nerve, and enters the lateral aspect of the thyroid cartilage. It is 

 the largest nerve of this region. The inferior laryngeal nerve is isolated most 

 readily below the larynx. It pursues a course upward along the trachea to enter 

 the inferior aspect of the larynx. 



Cut across the pharynx between the hyoid bone and upper margin 

 of the thyroid cartilage. Bring the tip of the epiglottis through the 

 incision and secure it by means of a pair of artery forceps. Enlarge 

 the incision laterally so that the larynx may be raised and an unob- 

 structed view be obtained of its interior. Identify the true and false 

 vocal cords, the glottis, and the ventricles. Observe the alterations in 

 the size and shape of the glottis in quiet inspiration and expiration. 



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