The study of the normal heart action is attracting an increasing amount of interest. Keith1 calls attention to the fact that the heart functionally consists of a central pump, the left ventricle, with three subsidiary loading pumps, the right and left auricles, and the right ventricle. Each chamber has a fulcrum, that of the auricle being applied through the fixation to the dorsal pericardial walls and through the pericardial extensions on the pulmonary vessels and lungs to the costal and diaphragmatic chest wall; the ventricles have two fulcrums, the fixed ascending stem of the aorta, and the movable fulcrum at the apex.With ventricular contraction the auricular base about the mitral and the tricuspid rings is reduced in size and through the action of muscles acting from the apical fulcrum is drawn down toward the apex, enlarging the auricles. This is the key to the venous pulse. The aortic base is unchanged and becomes the fulcrum from which the expelling musculature works. The muscles of the heart are arranged in groups of antagonistic muscles. In the left ventricle there is a circular expel¬ ling coat set between an outer and an inner spiral coat, the fixed axis passing from the mouth' of the aorta to the apex. In systole the muscles approach this axis. All of the muscular coats ultimately end in the fibers of the internal spiral coat of the left ventricle, each seg¬ ment narrowing or expanding on the principle of the iris diaphragm.The auriculoventricular bundle ends in the trabecular network of the apex where ventricular systole begins. The antagonist muscles are the internal muscles of the columnae carnae and the papillary muscles which extend from the apex to the base of the auricles and the aorta, and the external spiral muscles on the outside of the ventricle wall which end at the aortic and auricular bases. These groups are antag¬ onistic to lengthening of the heart chamber. In early systole when the auricular base descends, the circular fibers are more than antagon-1. Keith, Arthur: Brit. M. J. 1:361 (March 30) 1918. Downloaded From: http://archpedi.jamanetwork.com/ by a UCSF LIBRARY User on 06/13/2015ized, but in the later phase of systole the circular fibers become dominant, and raise the auricular base. The apico-aortic fibers are sustaining and do not change in length during systole.In the right ventricle, the pulmonary orifice is not fixed, the infundibular bands from the right base acting as the fulcrum. The septum really belongs to the left ventricle and is only passively a wall of the right, so that the internal musculature running from the apex to the base is more highly developed on the right, with the pectinate muscles forming an opponent set.Smith2 has an interesting study of the anatomy of the coronary arteries obtained by injecting the arteries with physiologic sodium chlorid solutions until the fluid returns clear and then injecting a solution consistng of 2 parts of barium suspended in 10 parts of water with a little tragacanth. Stereoscopic roentgenograms are made, and he finds studyi...
IOWA CITY THE HEARTThe electrocardiogram during the past year has become more extensively used, and more carefully studied. There are many points on which observers disagree, but certain fixed conclusions stand out clearly and its value in aiding diagnosis is undisputed. It is interesting to learn that in all of Paris Ribierre 1 knows of only two hospitals equipped for electrocardiography. To remedy this he suggests that medical societies in the smaller cities should acquire equipment to be loaned to the members.Mann 2 describes his monocardiogram, which is an attempt to combine the graphs obtained in Leads I, II and III into a single curve. It is based on the fact that Lead II equals Lead III plus Lead I or the algebraic sum of the ordinates in Leads III and I at the same instant. By finding the location of the center of negativity at subsequent time intervals and connecting these points a curve is formed representing the cardiac cycle. This monocardiogram is a fusion of the three leads into a single curve by an algebraic reversal of the process by which the leads are obtained.Hamburger 3 studies the changes in the wave, which represents the auricular complex. The physiologic complex is an upright wave which results from auricular systole. It expresses the origin of the heart beat at the normal site of the impulse formation, and the passage of the wave through the auricular tissue in definite directions. Altera¬ tions in the height, direction and configuration are caused by abnormal auricular conditions. Twenty per cent, of the 300 electrocardiograph curves at the Michael Reese Hospital (Chicago) show an inverted wave, usually in Lead III. The wave may be inverted by vagus stimulation, by the impulse originating in the lower portion of the auricle, by force expiration, and by digitalis. The wave may be Received for publication.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.