86 A MANUAL OF PHYSIOLOGY 



described. Sometimes a double sound was employed, armed with 

 two ampullae, placed at such a distance from each other that when 

 one was in the right ventricle the other was in the auricle of the same 

 side. Each ampulla communicated by a separate tube in the 

 common stem of the instrument with a recording tambour, and the 

 writing points of the two tambours were arranged in the same vertical 

 line. When any change in the blood-pressure takes place, the 

 degree of compression of the ampullae is altered, and the change is 

 transmitted along the air-tight connections to the recording tambours. 

 Simultaneous records of the changes in the blood-pressure in the 

 right auricle and ventricle obtained in this way indicate a sudden 

 rise of the auricular pressure corresponding with the auricular systole, 

 followed by a sudden fall (Fig. 20). This is represented on the ventri- 

 cular curve by a smaller elevation, which shows that the pressure in the 

 ventricle has been raised somewhat by the blood driven into it from 

 the auricle. Then follows immediately a great and abrupt increase 

 of ventricular pressure, the result of the systole of the ventricle. 



FIG. 25. DIAGRAM OF CARDIAC SOUND FOR SIMULTANEOUS REGISTRATION 

 OF ENDOCARDIAC PRESSURE IN AURICLE AND VENTRICLE. 



A, elastic ampulla for auricle ; V for ventricle ; T, tubes connected with recording 

 tambours. 



The beginning of this elevation is synchronous with the beginning of 

 the first sound ; it remains for some time at the maximum, and then 

 the curve suddenly sinks as the ventricle relaxes. On the descending 

 limb there is a slight elevation, due, as Marey supposed, to the 

 closure of the semilunar valves, which causes a better-marked and 

 simultaneous elevation in the curve of aortic pressure when this is 

 registered by means of a sound passed into the aorta through the 

 carotid artery. Both the auricular and ventricular curves now begin 

 again to rise slowly, showing a gradual increase of pressure as the 

 blood flows from the great veins into the auricle, and through the 

 tricuspid orifice into the ventricle. This slow rise continues till the 

 next auricular systole. 



It is probable that some of the smaller elevations on the 

 curves of Chauveau and Marey, and particularly that 

 which they associated with the closure of the semilunar 

 valves, were due to the oscillations of their apparatus. For 

 it is a remarkable fact that on most of the endocardiac 

 pressure tracings of the best modern manometers, whether 



