lxl] pulse, 291 



9. Meiocardia and Auxocardia (Ceradini). 



(a.) Bend a glass tube about 20 mm. in diametei into a semicircle, with 

 a diameter of about 6-8 inches. Taj)er off one end in a gas- flame to fit a 

 nostril, and draw out the other end of the tube to about the same size. 

 Round off the edges of the glass in a gas-flame. 



(b.) Fill the tube with tobacco-smoke, place one end of it in one nostril, 

 close the other nostril, cease to breathe, but keep the glottis open. Observe 

 that the smoke is moved in the tube, passing out in a small puff during 

 auxocardia, i.f., when the heart is largest; while it is drawn farther into 

 the tube during meiocardia, i.e., when the heart is smallest. 



These movements, sometimes called the * ' cardio-pneumatic movements," 

 are due to the variations of the size of the heart during its several phases at 

 fulness altering *he volume of air in the lungs. 



LESSON LXI. 



PULSE— SPHYGMOGRAPHS—SPHYGMOSCOPE— 

 PLETHYSMOGRAPH. 



1. The Pulse. 



(a.) Feel the radial pulse of a fellow-student, count the number 

 of beats per minute ; compare its characters with your own pulse, 

 including its volume and compressibility. Observe how its charac- 

 ters and frequency are altered by (i) muscular exercise; (2) a 

 prolonged and sustained deep inspiration ; (3) prolonged expira- 

 tion ; and (4) other conditions. 



(/;.) Feel the radial pulse-beat and heart-beat (the latter over the 

 cardiac impulse) simultaneously. Note that the former is not 

 synchronous with the latter, the pulse-beat at the wrist occurring 

 about ^ second after the heart-beat, i.e., the pulse-wave takes this 

 time to travel from the heart to the radial artery. 



(r.) Ivisten to the heart-sounds at the same time that the radial 

 pulse is being felt. Note that the pulse is felt after the first sound 

 about midway between the first and second sounds. 



(r/.) By appropriate recording apparatus one can readily show 

 that the pulse is not simultaneous throughout the arterial system : 

 thus the carotid precedes the femoral, &c. 



2. Sphygmograph.— Many forms of this instrument are in use. 

 Study the forms of Marey and Dudgeon. 



Marey's Sphygmograph (fig. 2 1 4) — Application of. 



(a.) Cause the patient to seat himself beside a low table, and 

 place his forearm on the double-inclined plane (fig. 214), which, 

 in the improved form of the instrument, is the Hd of the box so 



