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PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Ludwig and Hesse have shown that the shape which the heart 

 assumes after death does not represent its shape during life, either during 

 systole or diastole. They obtained the diastolic shape of the ventricle 

 by making a plaster cast of the heart dilated under the pressure of a 

 column of defibrinated blood equal to that of the mean arterial pressure 

 (150 mm. of mercury in the dog). The systolic shape was obtained by 

 immersing the heart, immediately after death, in a hot (50°C.) saturated 

 solution of potassic bichromate, when the heart gives a single contraction 

 and remains in systole, the proteids being coagulated from heart rigor. 

 A plaster cast is then made as before. They found that in diastole the 

 shape of the ventricle is nearly hemispherical, with the posterior surface 



III !y v 



Fig. 198.— Projections of a Dog's Heart, after Ludwig and Hesse. (Landois.) 



I, posterior surface. II, left lateral surface, m, anterior surface. IV, A, aorta: PA, pulmonary 

 artery ; M, mitral, and T, tricuspid orifices. V. projection of the base in systole and diastole : RV, right, 

 and LV, left ventricles. The shaded outlines represent the projections of the heart in diastole, the dotted 

 line the outline of the heart in systole. 



flatter than the anterior, the greatest diameter being the transverse 

 diameter of the base, and the shortest from the apes to the base. In 

 systole the ventricle becomes more conical from the greater contraction 

 of the basal diameters, the curvatures of the anterior and posterior 

 surfaces being now nearly equal, and while the vertical diameter of the 

 right ventricle shortens the left remains unchanged. In the systole, the 

 area of the base of the heart is diminished nearly one-half, thus, by 

 diminishing the auriculo-ventricular openings, greatly assisting the ven- 

 tricular valves (Fig. 198). 



The transmission of the ventricular contraction may be represented 

 graphically by the cardiograph (Fig. 199). 



