244 PHYSIOLOGY OF THE HEART. [CH. xx. 



Another method of overcoming the imperfections of Marey's 

 tambour is by the use of Hiirthle's manometer (tig. 244). In 

 this the tambour is very small, the membrane is made of thick 

 rubber, and the whole, including the tube that connects it to 

 the heart, is filled with a strong saline solution (saturated solution 

 of sodium sulphate). 



The tracing obtained by this instrument, when connected with 

 the interior of the ventricle, is represented in the next figure. 



The auricular systole causes a small rise of pressure A B ; it 

 lasts about '05 second. It is immediately followed by the ven- 

 tricular contraction, which lasts from B to D. From B to c the 

 ventricle is getting up pressure, so that at c it equals the aortic 

 pressure. This takes '02 to '04 second. Beyond c the aortic 

 valves open, and blood is driven into the aorta ; the outflow lasts 

 from c to D (-2 second). At D the ventricle relaxes. The flat 

 part of the curve is spoken of as the systolic plateau, and according 



Fig. 245. Curve of intra-ventricuJar pressure. (After Hiirthle.) 



to the state of the heart and the peripheral resistance may 

 present a gradual ascent or descent ; it occupies about 1 8 second. 

 Almost immediately after the relaxation begins, the intraven- 

 tricular pressure falls below the aortic, so that the aortic valves 

 close near the upper part of the descent at E. 



The amount of pressure in the heart is measured by a mano- 

 meter, which is connected to the heart by a tube containing a 

 valve. This was first used by Goltz and Ga\ile. If the valve 

 permits fluid to go only from the heart, the manometer will 

 indicate the maximum pressure ever attained during the cycle". 

 If it is turned the other way, it will indicate the minimum 

 pressure. The following are some of the measurements taken 

 from the dog's heart in terms of millimetres of mercury : 



Maximum Minimum 



pressure. pressure. 



Left ventricle . . . 140 mm. - 30 to 40 mm. 



Right ventricle ... 60 mm. - 15 mm. 



Right auricle ... 20 mm. 7 to 8 mm. 



By a negative ( ) pressure one means that the mercury is 

 sucked up in the limb of the manometer towards the heart. 



