2 2 THE ME CHANISM OF THE CIR C ULA TION. 



middle of the ascending limb of the ventricular curve. The period 

 of systolic output extends from the opening to the closure of the semi- 

 lunar valves, and that is the period during which the ventricular pressure 

 is higher in the differential tracing (Fig. 15, 1 to 3). This time of 

 output, according to Hurthle, is from 178 to 195 sec. in the dog, and 

 is, as already stated, hut slightly altered either by variations in aortic 

 pressure or in the frequency of the heart. 



The maximal pressure in the ventricles. — By means of their graduated 

 cardiac sounds Chauveau and Marey 1 reckoned the maximal pressure in 

 the right ventricle of the horse to be 24 to 30 mm. Hg ; in the left ven- 

 tricle 95 to 140 mm. Hg. With the maximal manometer, Goltz and 

 Gaule found the pressure in the dog to be — 



Right ventricle, .... 35-62 mm. Hg. 



Left ,-, .... 114-135 



de Jager 2 employed a maximal manometer, but lessened the 

 resistance by using large cannulse. He measured the maximum in 

 the ventricle, and then, after pulling the cannula out into the aorta, 

 immediately measured the aortic maximum. The results recorded 

 were — 



Left ventricle, .... 150-234 mm. Hg. 



Aorta, . . . . . . 156-216 



Right ventricle, . . . . 26-72 



These results were obtained during morphia narcosis, and are 

 perhaps too high. The relation of the right to the left ventricular 

 maximum is therefore from 1:3 to 1:6. This agrees closely with the 

 relation found between the pulmonary arterial and the aortic pressures. 

 Thus by Beutner 3 this was found to be 1 : 3 in dogs, 1 : 5 in cats, 1 : 4 in 

 rabbits, and by Colin, 4 1 : 3 or 1 : 4. 



In order that the systole may be efficient, the intraventricular 

 pressure must rise to a higher point than the aortic pressure. In certain 

 conditions of the heart some of the beats may be inefficient, and so 

 produce no sign on the aortic curve. 



After considerable loss of blood, the intraventricular pressure at each 

 systole exceeds the aortic pressure by a comparatively greater amount. 

 The auricular pressure curve. — The systolic pressure in the auricle 



reaches its maximum in 1 sec. 

 in the horse, while the ven- 

 tricular contraction up to the 

 end of the plateau lasts 1 sec. 

 This short duration of the 

 auricular systole found by 

 Chauveau and Marey has not been confirmed by all observers. 5 



The pressure curve of the auricle has been obtained by the same 

 instruments as were employed for ventricular observations. The tracings 

 obtained by Chauveau, Marey, and Fredericq with the sphygmoscope, and 



1 Loc. ciL, p. 305. 2 Arch. f. d. ges. Physiol., Bonn, 1883, Bd. xxx. S. 504. 



3 Ztsehr.f. rat. Med., 1852, N. F., Bd. ii. S. 118. 



4 Bull. Acad, de mid., Paris, 1874, p. 398. 



s "Trav. du labor, de Marey," 1877, tome iii. p. 311. Cf. Samways, "Le Role de 

 loreilette gauche," Paris, 1896. 



B 



Fig. 16. — Auricular pressure curve. — Porter. 



