HEART. 670 HEART. ln.v. — da. in the left heart prevents regurgitation of blood to which it is ascribed by physiologists. Thus into the rignt auricle, and the tricuspid valve in we liave (1) the impulse of the apex of the heart llie riglit heart prevents a lil<e accident in the against the side of the cliest; (2) the contraction case of the left auricle. The semilunar valves, of the muscular walls of the ventricles; (3) the as stated, prevent regurgitation at the end of the tension of the auriculo-ventricular (tricuspid contraction, or systole. The diastole, or expan- and mitral) valves and of the chordis tendinece. sion, of the heart begins at once, and the auricles (See Circulation.) The second sound is caused dilate, the right one receiving blood from the by the sudden closure of the valves of the aorta two ven* cavae. which carry venous blood from and of the pulmonary artery as the currents of the upper and lower parts of the body: the left blood reverse at the instant the heart relaxes one receiving arterial blood from the lungs and begins to dilate. When the valves are changed by disease, the sounds undergo special alterations, which are of the highest importance in diagno- sis. The normal sounds may be intensified or weakened, or they may disappear entirely and be re- placed by murmurs ; or abnormal sounds may be heard simultaneous- ly with, or in the intervals be- tween, the normal ones. Thus we find murmurs of regurgitation in valvular insufficiency; murmurs of obstructed flow of blood in valvu- lar stenosis ; aneurismal murmurs ; friction sounds in pericarditis, etc. HEART, Diseases of the. Heart disease is a term including many affections of the organ as well as disturbances in its action due to disease elsewhere. Galen (q.v. ) was the first to write of disease of the heart, which Hip- pocrates (q.v.) had denied, though to Vesalius (q.v.) is due the credit of accurate and intelligent grasp of POSTERIOR VIEW OF THE LEFT CHAMBER OF THE HEART, WITH THE GREAT the SubjCCt. TllC disCOVCry of the l.auaf. int.iau. gcar.v. vagcarv. arUjntva. compcmt.p.m. fmcolcan com.Lp.a- Ipv. 'for. or. 7':rr — va.o.cor.sL ^ — post.mi.va. 'T dio ten. comppost.pnu col. car. Cora w. I vent. BLOOD-VE&SELB AND CORONARY SINUa LAID BARE. l.c.a., left carotid arterj; I.sc.r.. left subclavian vein; a., aorta; l.au.ap.. left auricular appendix; int.I.au.. interior of left auricle; g.car.T., great car- diac vein; VH.g.car.r., valve of great cardiac vein; ant.mi.va.. anterior seg- ment of mitral valve: comp.ant.p.m., compound anterior papillary muscle: t'.m.col.rar.. fine mesli-work of c^olumnie carnete at the apex of ventricle: in. v., innominate vein: cl.a., ductus arteriosus: com.l.p.a., oonimencement of left pulmonary artery; l.p.v., left pulmonary veins; for.ov., concave edge of the foramen ovale; r.p.v., right pulmonary veins; Lau.vent.A^lt auriculo-ventricular opening; va.o.cor.sL, valve orifice of vein in coronary sinus; cor.s;., coronary sinus; va.t.. valve of Thebesius; v.c.;., vena cava In- ferior;posC.mi.ra., posterior segment of mitral valve: cbo.ten., ehordte ten- dineae; comp.po.-'f. p.m., compound posterior papillary muscle; co7. car., colum- n£e carnete; cor.a., coronary artery: w.l.vent., section through wall of left ven- tricle. circulation of the blood by Harvey (q.v.) in 1028 led the way for the investigations which, nearly a cen- tury later, gave clinicians absolute knowledge of certain affections of the heart. Vieussens, Lancisi, Morgagni, Senae, and Auenbrug- ger deserve mention in the history of this subject. La6nnec (q.v.), who, in 1819, added the method of auscultation to that of percus- sion, advanced by his teacher Cor- through the four pulmonary veins. The ven- visart, and who invented the stethoscope, opened tricles then expand, and the blood passes through the field to all explorers. Richard Bright (q.v.) the auriculo-ventricular orifices from the auricles detected the enlargement of the organ which until they are full, and the diastole is then com- accompanies Bright's disease of the kidneys, plete. (See Ciecui:..a.tio.n. ) Previous to birth, Kreysig and Bouilland recognized endocarditis, the circulation in the infant differs, because of Virehow (q.v.), in 1850, elucidated thrombosis structural differences. Sec Fcetus ; Embryo. Sounds of the Heart. On applying the ear to the cardiac region of a living man or mammal, in a state of health, two successive sounds are heard, each pair of which corresponds with one and embolism. Diseases of the heart are either (1) func- tional, or (2) organic. In functional diseases there is no discoverable alteration in structure, md the disorder of function is due to nervous pulsation. These are known as the first and the iiifluenees. In organic di.seases structural altera- second sound. The first sound is dull and pro- tion is present. Ir"^'?;^ '"'*" ^^l '"'""t. '" •""■ ?,"'^ sharp, and functional heart diseases. the ditlerence between them is well expressed by . ^i i i- t n articulating svllables, lubb, dup. The first sound These include disorders m the beating of the continues during three-tenths of the pulsation, I'cart and in the nature of its contracl^ions as then follows the 'short pause' lasting one-tenth, '^vell as neuralgic pains in the heart. Pal- next the second sound lasting two-tenths, lastly pitation is the term given to a rapid and the 'long pause' lasting four-tenths. more or less distressing beating of Ihc heart. The cause of the first of these sounds has been in which the pulse may be accelerated from the a subject of much discussion. During the first normal 7-5 to 80 beats a minute to liiO or more sound several distinct actions are taking place, a minute. This condition may be due to organic
