166 THE CIRCULATION OF THE BLOOD 



The method adopted by Rolleston is as follows: 



A window is made in the chest of an anesthetized and curarized animal, and an appro- 

 priately curved glass cannula introduced through an opening in the auricular appendix. 

 The cannula is then passed through the auriculo-ventricular orifice without causing any 

 appreciable regurgitation, into the auricle, or it may be introduced into the cavity of the 

 right or left ventricle by an opening made in the apex of the heart. In some experiments 

 the trocar is pushed through the chest wall into the ventricular cavity. His apparatus 



FIG. 164. Endocardiac Pressure Curve from the Left Ventricle of the Dog. The thorax was 

 opened and a cannula introduced through the apex of the ventricle; the abscissa is the line of at- 

 mospheric pressure. G to D represents the ventricular contraction; from D to the next rise at G 

 represents the ventricular diastole. The notch, at the top of which is F, is a post- ventricular rise 

 in pressure from below that of the atmosphere, and not a presystolic or auricular rise in pressure. 



is filled with a solution of leech extract in 0.75 per cent saline solution, or with a solution 

 of sodium bicarbonate of specific gravity 1083. 



The animals employed were chiefly dogs. The movement of the column of blood is 

 communicated to the writing lever by means of a vulcanite piston which moves with little 

 friction in a brass tube connected with a glass cannula by means of a short connecting 

 tube. 



When the lower part of the tube, A , is placed in communication with one of the cavities 

 of the heart, the movements of the piston are recorded by means of the lever, C. Attached 

 to the lever is a section of a pulley, H, the axis of which coincides with that of the steel rib- 



FlG. 165. Curve with a Dicrotic Summit from the Left Ventricle; the Abscissa Shows the At- 

 mospheric Pressure. 



bon, E ; while, firmly fixed to the piston, is the curved steel piston rod, /, from the top of 

 which a strong silk thread, /, passes downward into the groove on the pulley. 



This thread, /, after being twisted several times round a small pin at the side of the lever, 

 enters the groove in the pulley from above downward, and then passes to be fixed to the 

 lower part of the curve on the piston rod as shown in the smaller figure. 



The movement of the lever, C, is controlled by the resistance to torsion of the steel 

 ribbon, E, to the middle of which one end of the lever is securely fixed by a light screw 

 clamp, F. At some distance from this clamp, the distance varying with the degree of re- 



