ELEMENTARY EXPERIMENTAL PHYSIOLOGY 61 



B. Having recorded (1) the respiration and (2) the systolic blood 

 pressure, (3) counted the pulse and (4) measured the height of the 

 hand above the heart at which the veins collapse, make the subject 

 perform 10 minutes' strenuous mental work and again examine 

 and record systolic arterial blood pressure, pulse, venous pressure 

 and respiration, and note the colour of the face. 



C. Now make him take strenuous muscular exercise till he is 

 breathless, and repeat all the observations. 



Formulate your conclusions as regards the effect of mental work 

 and of muscular work upon 



The rate of the heart. 



The systolic arterial pressure. 



The condition of the peripheral vessels. 



The venous pressure. 



The rate and depth of respiration. 



Lesson XIII. To be provided for each pair of Students. 



1. Schema of circulation. 2. Web of frog's foot under low power of 

 microscope. 3. Dudgeon's sphygmograph. 4. Riva Rocci apparatus. 

 5. Stethoscope (binaural). 6. Recording tambour and tube. 



LESSON XIV 

 MODE OF ACTION OF THE HEART IN THE FROG 



I. The Cardiac Cycle 



1. Study the Exposed Heart in the Frog. 



Kill a frog by cutting off its head behind the tympanic membranes 

 or by thrusting a stout pin into the occipito-atlantoid joint and 

 destroying the brain. Thrust a thick pin down the spinal canal 

 (see Fig. 21, p. 31). - 



Pin the body on its back on a cork plate. Open the abdomen by 

 an incision in the middle line, and carry the incision up through the 

 shoulder girdle in the middle line, taking care that the point of the 

 scissors does not injure the heart. Separate widely the two sides 

 of the girdle, pinning each back firmly, and thus expose the heart in 

 the pericardium. Snip through the pericardium and study the 

 auricles, ventricle and bulbus as seen from the front. 



Study and describe the changes in shape which each part under- 

 goes the relative duration of each change in each part and the 

 sequence of events in the different parts and record your obser- 

 vations. Time and note the number of contractions of the ventricle 

 in one minute. 



Now take the tip of the ventricle in fine-pointed forceps or pass a 

 fine needle with a fine thread through the tip of the ventricle, lift it 

 up and observe a fold of pericardium, the frsenum, which is attached 

 to it behind, and carefully snip this through. Then turn the 

 ventricle freely forward and study the changes which occur in the 

 sinus venosus, and the relation of these changes to the changes in 

 the other parts of the heart. 



