i86 



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 appropriately curved glass cannula introduced through an opening in the 

 auricular appendix. The cannula is then passed through the auriculo-ventric- 

 ular 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 atmospheric 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 o . 7 5 per cent, saline solution, or with 

 a solution of sodium bicarbonate of specific gravity 1.083. 



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 



FIG. 165. Curve with a Dicrotic Summit from the Left Ventricle; the Abscissa Shows the 



Atmospheric Pressure. 



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 ribbon, 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 around a small pin at the 

 side of the lever, enters the groove in the pulley from above downward, and 



