CHAP, iv.] 



THE VASCULAR MECHANISM. 



179 



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 mammalian heart. 



4. The movements of the ventricle may be registered by introducing 

 into it through the auriculo- ventricular orifice a so-called 'perfusion' 

 cannula, Fig. 39 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 a, enters the ventricle, 

 and returns by the tube b. 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. 39 n., 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 b the interior 



FlG. 39. PUBELT DIAGRAMMATIC FIGURES OP 



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

 a, wall of ventricle; , ligature. 



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

 and oil, containing the ventricle a tied on to perfusion Ccinnula/. b, tube leading 

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



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 

 ventricle subsequently becomes distended the pressure in the chamber 

 is increased, and the piston and lever sink. In this way variations in 

 the volume of the ventricle may be recorded, without any interference 

 with the flow of blood or fluid through it. 



TO O 

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