PRACTICAL EXERCISES 



183 



factorily arranged, set off the clockwork which moves the plate D, 

 and a pulse tracing will be obtained. Study the changes which can 

 be produced in the pulse curve (a) by altering the position of the 

 body (sitting, standing, and lying down) ; (b) by exercise ; ( f ) by in- 

 halation of 2 drops of amyl nitrite poured on a handkerchief; (d) by 

 raising the arm above the head 

 and letting it hang at the side; 

 (e) by compression of the brachial 

 artery at the bend of the elbow; 

 (/) by altering the pressure of the 

 pad. Varnish the tracings after 

 marking on them the conditions 

 under which they were obtained. 



A Dudgeon's sphygmograph 

 (Fig. 68A) may also be employed. 

 Or a small glass funnel connected 

 with a recording tambour may be 

 pressed over the carotid artery. 

 The lever of the tambour writes on 

 a drum, on which at the same time 

 half or quarter seconds are marked by an electro-magnetic signal. 



17. Plethysmographic Tracings. Connect the vessel C (Fig. 39, 

 p. 1 1 6) with B, place the arm in it, and adjust the indiarubber band 

 to make a watertight connection. Support C so that the arm rests 



FIG. 69. EFFECT OF EXERCISE ON 

 THE PULSE (MAREY). 



Upper tracing, normal ; lower tracing, 

 after running. 



FIG. 70. EFFECT OF AMYL NITRITE ON THE 



PULSE (MAREY). 



Upper tracing, normal ; lower, after inhalation 

 of amyl nitrite. 



FIG. 71. PULSE -TRACINGS 



FROM DIFFERENT ART. RIES. 



T, temporal ; /?, radial ; P, 

 artery of foot. (v. Frey.) 



easily within it, and fill it with water at body temperature. Adjust a 

 writing-point, carried by the float A, to write on a drum, and close 

 the upper tubulure of C with a cork. The quantity of blood in the 

 arm is increased with every systole of the left ventricle, diminished in 

 diastole. The float will therefore rise when the ventricle contracts, 

 and sink when it relaxes. Or C may be connected by a rubber tube 

 with a recording tambour writing on the drum. No water must get 



