CIBCULA TION. 



187 



0. Solutions which Maintain the Beat of the Heart. 



The beat of the heart is maintained during life by a constant supply of 

 oxygenated blood. The blood, however, is a very complex fluid, and it can 

 hardly be supposed that all of its constituents are of equal value to the heart. 

 The systematic search for those constituents of the blood which are of import- 

 ance to the nutrition of the heart was begun in Lud wig's laboratory iu 1875 

 by Merunowicz. The first step toward the method used by Merunowicz and 

 his successors was taken by ('yon. Cyon tied cannulas in the vena cava 

 inferior and in one of the aortse of the extirpated heart of the frog, and 

 joined them by a bowed tube filled with serum. The ventricle pumped 

 the serum through the aortic cannula and the bowed tube into the vena 

 cava, whence it reached the ventricle again. The force of the contraction 

 was measured by a mercury manometer which was joined by a side branch 

 to one limb of the bowed tube. 



The frog heart manometer method thus introduced by Ludwig and (yon 

 has undergone various modifications at the hands of Blasius and Fick, Bow- 

 ditch, Luciani, Kronecker, and others. Blasius and Fick were the firs! to 

 register changes in the volume of the heart by the plethysmography method, 

 the organ being enclosed in a vessel filled with normal saline solution and 

 connected with a manometer. This idea reappears in the Strassburg apparatus 

 described below. 



A valuable improvement was made by Kronecker, who invented a double 

 cannula, through one side of which the " nutrient " fluid enters the ventricle 

 while it passes out through the other (Fig. 4 1 ). 

 The contents of the ventricle are thus contin- 

 ually renewed. In 1878, Hoy constructed the 

 instrument shown in Figure 42, by means of 

 which the changes in the volume of the heart at 

 each contraction are recorded on a moving cylin- 

 der. A great advance was made by Williams, 

 in the invention known as " Williams's valve," 

 which is the essential feature of the apparatus 

 devised by this investigator and others in 

 Schmiedeberg's laboratory at Strassburg. The 

 present form of this apparatus is illustrated in 

 Figure 43. A perfusion cannula is introduced 

 into the ventricle through the aorta. Through 

 one tube of the cannula the heart is fed from a 

 reservoir placed above it. Through the other 

 the heart pumps its contents into a higher reser- 

 voir or into the same reservoir. Thus the heart is " Loaded " with a column 

 of liquid of known height and pumps againsl ;i measurable resistance. A 

 Williams valve in the inflow lube prevents any flow except in the direction 

 of the heart. A similar valve reversed in the outflow tube prevents any How 



Fig. 41.— The perfusion cannula 

 of Kronecker. The ventricle is tied 

 ..n the cannula at d, a ring heing 

 placed here to prevent the ligature 

 from slipping. The double tube, 

 shown in cross section at ■ , 'li\ Idea 

 into the large brani b a and the 



small branch 6, The nutrient BOlU- 

 tinn enters tic bearl through '- and 

 escapee through <<. The Bilver wire 

 e can ho connected \\ Itb one pole of 

 11 battery, the cannt ae one 



electrode, and the fluid Burrounding 

 the bearl as i be other. 



