LX.] 



HEART-VALVES. 



28; 



noting that the first sound is heard loudest at the apex beat, while 

 the second is heard loudest at the second right costal cartilage at 

 its junction with the sternum. 



4. Cardiograph. Several forms of this instrument are in use, 

 including those of Marey, B. Sanderson, and the pansphygmograph 

 of Brondgeest. Use any of them. 



(a.) Place the patient on his back with his head supported on a 

 pillow. Feel for the cardiac impulse between the fifth and sixtl: 

 ribs on the left side, and about half an inch inside the mammary 

 line. 



(/>.) Arrange the cardiograph by connecting it (fig. 208) with 

 thick-walled india-rubber tubing to a recording Marey 's tambour 

 adjusted to write on a drum (fig. 

 1 50). It is well to have a valve 

 or a y-tube capable of being 

 opened and closed between the 

 receiving and recording tambours, 

 in order to allow air to escape if 

 the pressure be too great. 



(('.} Adjust the ivory knob of 

 the cardiograph (p) over the car- 

 diac impulse where it is felt most, 

 and take a tracing. Fix, varnish, 

 and study the tracing or cardio- 

 gram. 



FIG. 208. Marey's Cardiograph, p. Button 

 placed over cardiac impulse ; s. Screw 

 to regulate the projection of p ; t. 

 Tube to other tambour. 



5. Effect of Swallowing on the 

 Heart-Beats (Man). 



With a watch in front of you, 



count the number of your own pulse-beats per minute, and then 

 slowly sip a glass of water, still keeping your finger on the pulse. 

 Count the increase in the number of pulse-beats during the 

 successive acts of swallowing. This is due to the inhibitory action 

 of the vagus being set aside. 



6. Reflex Inhibition of the Heart (Rabbit). 



Place one hand over the chest of a rabbit and feel the beating of 

 the heart. With the other hand suddenly close its nostrils, or 

 bring a little ammonia near the nostrils, so as to cause the animal 

 to close them. Almost at once the heart is felt to cease beating 

 for a time, but it goes on again. 



7. Goltz's Tapping Experiment (Frog). 



(a.) Destroy the cerebrum and optic lobes of a frog. Pin it out on a frog- 

 plate, and expose its heart, or attach the heart to a GaskelPs lever. Expose 



