LABORATORY MANUAL OF PHYSIOLOGY. 



culty in breathing, amounting to distinct dyspnoea. Note the in- 

 crease in thoracic breathing. 



Explain the difficulty in breathing following the paralysis of the 

 diaphragm. Is it due simply to the loss of the active movements 

 of the diaphragm in enlarging the vertical diameter of the thorax? 



6. Place both phrenic nerves on electrodes from the inducto- 

 rium. Stimulate with a medium strong tetanizing current, inter- 

 rupted about thirty times per minute. Is the dyspncea relieved ? 

 Does the rabbit cease attempts at thoracic breathing ? 



7. Close the trachea by means of an artery clamp and kill the 

 rabbit by asphyxiation. Note all phenomena connected with death 

 from this cause. After breathing has ceased, open the thorax and 

 observe the heart. Is this still beating? Note the color of the 

 blood. Note difference between the two sides of the heart. Excise 

 the heart. Does the heart-beat recover for a short time after ex- 

 cision ? 



VI. EFFECT OF BLOOD TEMPERATURE ON RESPIRATION. 



1. Heat. Narcotize a rabbit. Place, back down, on the rabbit- 

 board. Through a median cervical incision expose both carotid 

 arteries and isolate the vagus nerves. Arrange the apparatus for 

 recording the movements of the diaphragm. Isolate as much of 

 each carotid as possible. Separate the artery from the nerves 

 running with it, by several layers of paper. Tie each carotid, 

 gently, to a small tubing running parallel to the artery. One end 

 of this tubing is connected to a rubber outlet tube. The other end 

 is connected to a rubber inlet tube. The inlet tube leads from a 

 bottle filled with water kept at a temperature of 40 C., by immer- 

 sion in a water-bath. This bottle is elevated sufficiently to give a 

 constant flow of warm water through the tubes in contact with the 

 arteries. The blood passing through the carotids is therefore 

 warmed two or three degrees above the normal. 



Set up the arrangement as above described. First take a normal 

 respiratory tracing. Then, while a tracing is being taken, let the 

 warm water run through the tubing and note the effect upon res- 



