242 



PHYSIOLOGY OF THE HEART 



[CH. XXI. 



is only applicable to large animals, such as the horse. Thirdly, 

 because the intraventricular changes of pressure are communicated 

 to the recording tambour by a long elastic column of air ; and 

 fourthly, because the tambour arrangement has a tendency to record 

 inertia vibrations. Kolleston reinvestigated the subject with a more 

 suitable but rather complicated apparatus. The principle of his 

 method consisted in placing the cavity of a heart-chamber in 

 communication with a recording apparatus by means of a tube 

 containing saline solution. His recording apparatus consisted of a 

 lever connected to a piston ; the upward and downward movements 

 of the piston-rod were due to the varying pressures exerted on the 

 blood by the contraction and dilatation of the heart. 



Another and still better method of overcoming the imperfections 

 of Marey's tambour is by the use of Hurthle's manometer (fig. 222). 



FIG. 222. Hurthle's Manometer. 



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. 



FIG. 223. Curve of intraventricular pressure. (After Hiirthle.) 



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

 about *05 second. It is immediately followed by the ventricular con- 

 traction, 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. Just 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 top of the curve is 

 spoken of as the systolic plateau, and according to the state of the 



