LABORATORY MANUAL OF PHYSIOLOGY. 



(h) Stimulate one superior laryngeal nerve with a weak tetaniz- 

 ing current. Note the effect on the respiratory movements. Stim- 

 ulate with a stronger current and note the effect. 



(i) Now tie and cut the other vagus nerve. Both vagi are now 

 severed. What is the effect on the rhythm, rate, and depth of the 

 respiratory movements ? 



(y) Stimulate both central ends of the cut nerves with a weak 

 tetanizing current. Note the effect on the rate, rhythm, and char- 

 acter of the respirations. Stimulate with a stronger current. 

 Result? 



(k) Stimulate both vagi with a weak tetanizing current, and, 

 when the effect of such stimulation begins to show, stimulate 

 both superior laryngeal nerves with a medium strong current. 

 Result ? 



In all of the above experiments, marks should be made upon 

 the tracings to indicate the operative procedures and their time 

 relation to the tracing; the nerves stimulated and the strength and 

 nature of the stimulus employed. 



(/) Stimulate the peripheral ends of the divided vagus nerves. 

 Is there any effect on the respiratory movements ? 



From the above experiments what conclusions can you draw 

 concerning the function of the vagus nerve in relation to respira- 

 tion ? Is the vagus chiefly an afferent or an efferent nerve in re- 

 lation to the lungs? 



The vagus has now been studied, in part, in connection with the 

 circulation, digestion, and respiration. Compare its functions in 

 relation to the three systems. It contains both afferent and effer- 

 ent fibres for circulation, digestive tract, and respiratory tract. 

 Summarize your knowledge on the subject, secured in part through 

 your own experiments in the laboratory. 



V. INNERVATION OF THE DIAPHRAGM. 



i. Still using the same rabbit that was used in the previous ex- 

 periments, expose the phrenic nerve of the right side. This may 

 be done in the following manner: Enlarge the cervical incision to 



