THE CIRCULATION OF THE BLOOD 513 



The side branch substitutes a wide channel for the 

 narrow ones, and thus is equivalent to a dilatation of 

 the vessels. 



The pressure in the ventricle is varied through a 

 tambour covered with rubber membrane. The mem- 

 brane is grasped between two disks, one below and 

 one above. The upper disk is screwed down upon 

 the lower until the membrane is tightly held. To 

 these disks is fastened a rod which ends in a yoke. 

 The yoke rests upon a small wheel, which in turn is 

 supported by a brass plate eccentric in form. This 

 brass plate is revolved by turning a handle attached 

 to the axle. As the plate revolves the small wheel 

 bears upon the eccentric rim and rises and falls with 

 the rise and fall in the rim of the plate. The motion 

 of the small wheel is transferred through the yoke, 

 rod, and disk to the rubber membrane, and thus to the 

 interior of the ventricle. 



The rim of the eccentric brass plate reproduces the 

 intra ventricular pressure curve in the dog. In pro- 

 jecting this curve upon the plate the periphery is 

 divided into fractions of a second, and the radii are 

 divided into millimetres of mercury pressure. 



Each revolution of the eccentric plate reproduces in 

 the ventricular tube both the time and the pressure 

 relations of the ventricular cycle in the dog. The 

 intraventricular pressure curve may be written by 

 connecting the side tube with a membrane manometer, 

 and clamping off the arterial mercury manometer to 

 be mentioned shortly. 



