CHAP, iv.] THE VASCULAR MECHANISM. 



281 



force of the ventricular systole is brought to bear on the manometer, 

 the index of which registers in the usual way the movements of 

 the mercury column. Newell Martin has succeeded in 

 applying a modification of this method to the mamma- 

 lian heart. 



4. The movements of the ventricle may be regis- 

 tered by introducing into it through the auriculo- 

 ventricular orifice a so-called 'perfusion' cannula, Figs. 

 52 and 53 I., with a double tube, one inside the other, 

 and tying the ventricle on to the cannula at the 

 auriculo-ventricular groove, or at any level below that 

 which may be desired. The blood or other fluid is 

 driven at an adequate pressure through the tube , 

 enters the ventricle, and returns by the tube 6. If b 

 be connected with a manometer as in method 3, the 

 movements of the ventricle may be registered. 



5. In the apparatus of Roy, Fig. 53 II., the exit- 

 tube is free, but the ventricle (the same method may be adopted for the 

 whole heart) is placed in an air-tight chamber filled with oil or partly 

 with normal saline solution and partly with oil. By means of the tube 



FIG. 52. A PER- 

 FUSION CANNULA. 



FIG. 53. PURELY DIAGRAMMATIC FIGURES OF 



I. Perfusion cannula tied into frog's ventricle, a, entrance, 6, exit-tube; 

 a, wall of ventricle ; /3, ligature. 



II. Eoy's apparatus modified by Gaskell. a, chamber filled with saline solution 

 and oil, containing the ventricle a tied on to perfusion cannula /. 6, tube leading 

 to cylinder c, in which moves piston d, working the lever e. 



b the interior of the chamber a is continuous with that of a small cylinder 

 c in which a piston d secured by thin flexible animal membrane works 

 up and down. The piston again bears on a lever e by means of which 

 its movements may be registered. When the ventricle contracts, and 

 by contracting diminishes in volume, there is a lessening of pressure in 

 the interior of the chamber, this is transmitted to the cylinder, and 

 the piston correspondingly rises, carrying with it the lever. As the 



