420 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



obtained shows certain characters which are recognized by all as properly- 

 belonging to the changes of pressure within the ventricle, whether right or 

 left. These general characters, moreover, persist after the opening of the 

 chest. They are as follows (see Figs. 107, 108, 109) : The muscular cou- 



Millimeters of 

 mercury. 



Line of atmospheric 

 pressure. 



Seconds. 



FIG. 107 Magnified curve of the course of pressure within the right ventricle of the dog, the chest 

 being open ; to be read from left to right. Recorded by the elastic manometer, with transmission by air 

 (von Frey). 



traction of the systole begins quite suddenly, and produces a swift and ex- 

 tensive rise of pressure, marked in the curve by a line but slightly inclined 

 from the vertical. In the same way the fall of pressure is nearly as sudden 

 and as swift as the rise, and perhaps even more extensive. The systolic rise 

 begins at a pressure a little above that of the atmosphere ; the diastolic fall 

 continues, toward its end, perhaps, with diminishing rapidity, till a point is 

 reached often below the pressure of the atmosphere. The pressure then 

 rises, perhaps continuing negative for a longer or shorter time, but presently 

 becoming equal to that of the atmosphere. Near this it continues, perhaps 

 with a gentle upward tendency, until, near the end of the ventricular diastole, 

 the rise becomes more rapid to the point at which the succeeding ventricular 

 systole is to begin. 



It is the course of the pressure between its rapid rise and its rapid fall which 

 has been the most disputed. The observers who employ manometers with liquid 



Line of atmospheric 

 pressure. 



FIG. 108. Magnified curve of the course of pressure within the left ventricle and the aorta of the 

 dog, the chest being open ; to be read from left to right. Recorded simultaneously by two elastic man- 

 ometers with transmission by liquid. In both curves the ordinates having the same numbers have the 

 following meaning: 1, the instant preceding the closing of the mitral valve ; 2, the opening of the semi- 

 lunar valve; 3, the beginning of the "dicrotic wave," regarded as marking the instant of closure of the 

 semilunar valve ; 4, the instant preceding the opening of the mitral valve (Porter). 



transmission, have so far found that the high swift rise at the outset of the 

 systole is soon succeeded by a sudden change. According to them the pressure 

 within the manometer now exhibits fluctuations of greater or less extent which 



