74 SELF-STEERING ACTION OF THE HEART. 



The Self-Steering Action of the Heart. Briicke attempted to show 

 that during the systole, or contraction of the ventricle, the semi-lunar 

 valves covered the openings of the coronary arteries, so that these 

 vessels could be filled with blood only during the diastole or relaxation 

 of the ventricle. To him it seemed that (a.) the diastolic filling of the 

 coronary arteries would help to dilate the ventricles ; (&.) on the con- 

 trary, a systolic filling of these arteries would oppose the contraction, 

 because the systolic filling and expulsion of the blood from the 

 coronary arteries would diminish the force of the ventricular contrac- 

 tion. To this arrangement, Briicke gave the above name. 



Arguments against B^ucke's View. The following considei-ations militate 

 against this theory :(!.) Filling the coronary vessels under a high pressure in a 

 dead heart causes a diminution of the ventricular cavity (v. Wittich). (2.) The 

 chief trunks of the coronary arteries lie in loose sub-pericardia! fatty tissue, in the 

 cardiac sulci, hence a dilatation of the ventricle through this agency is most 

 unlikely (Landois). (3.) Experiments on animals have shown that a coronary 

 artery spouts, like all arteries, during the systole of the ventricle. Von Ziemssen 

 found that in the case of a woman (Serafin), who had a large part of the anterior 

 wall of the thorax removed by an operation, the heart being covered only by a 

 thin membrane, the pulse in the coronary arteries was synchronous with the 

 pulse in the pulmonary artery. H. N. Martin and Sedgwick placed a manometer 

 in connection with the coronary artery, and another with the carotid in a large 

 dog, and they found that the pulsations occurred simultaneously. When a coronary 

 artery is divided, the blood flows out continuously, but undergoes acceleration during 

 the systole of the ventricles (Endemann, Perls). (4.) If a strong intermittent 

 current of water be allowed to flow through a sufficiently wide tube into the left 

 auricle of a fresh pig's heart, so that the water passes into the aorta, and if the aorta 

 be provided with a vertical tube, the water flows continuously from the coronary 

 arteries, and is accelerated during the systole. (5.) It is exceedingly improbable 

 that the coronary arteries should be tilled during the diastole while all the other 

 arteries are filled during systole of the ventricle. (6.) There is always a sufficient 

 quantity of blood in the sinus of Valsalva to fill the arteries during the first part of 

 the systole. (7. ) The valves, when raised, are not applied directly to the aortic 

 wall (Hamberger, Eiidinger) even by the most energetic pressure from the ventricle 

 (Sandborg and Worm Miiller). (8.) Observations on voluntary muscles have shown 

 that the small arteries dilate during contraction of the muscle, and the blood 

 stream is accelerated. (9.) By the systolic filling of the aorta the arterial path is 

 elongated this elastic distension is compensated before the diastole occurs. By 

 the recoil of the aortic walls the layer of blood in them is driven backwards and 

 closes the valves (Ceraclini). According to Sandborg and Worm Miiller, the semi- 

 lunar valves close just after the ventricles have begun to relax, which agrees with 

 the curve obtained from the cardiac impulse (Fig. 25a, A). 



During the systole, the small arterial trunks lying next the ventricu- 

 lar cavities have to bear a higher pressure than that borne by the 

 aorta, and their lumen must be compressed during the systole so that 

 their contents are propelled towards the veins. 



Peculiarities of the Cardiac Blood- Vessels. The capillary vessels of the 



myocardium are very numerous, corresponding to the energetic activity of the 



