Volume 1

A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.

Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English

Date:: 1891

Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.

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$atria contract, retract the valves towards their base, and thus make a larger openino- for the passage of the blood into the ventricles; according to Paladino, the}^ raise the valves after they have been pressed down by the Ijlood-current. This observer also described some longitudinal fibres -which proceed from the ventricles to enter these valves. There is also a concentric layer of fibres arranged near their point of attachment, and directed more towards their ventricular surface. These fibres seem to contract sphincter-like when the ventricle contracts, and thus approximate the base of the valves, and so prevent too great tension being put upon them. The larger chordae tendineee also contain striped muscle, while a delicate muscular network exists in the valvula Thebesii and valvula Eustacliii. Purkinje's Fibres consist of an anastomosing system of greyish fibres whicli exist in the sub- endocardial tissue of the ventricles, especially in the heart of the sheep and ox. The fibres are made up of polyhedral clear cells, containing some granular protoplasm, and usually two nuclei (tig. 38). The margins of the cells are striated. Transition-forms are found between these cells and the ordinary cardiac fibres ; in fact, these cells become continuous with the true fully developed cardiac / ' -.— fibres. They represent cells which ' have been arrested in their develop- ment. They are absent in man and the lower vertebrates, but in birds and some mammals they are well marked ' {Schiveigger-Seidel, Ranvier). \ .. Blood-Vessels occur in the auriculo- ^ - ^ - ventricular valves only where muscular \ - /' fibres are present, while the semi-lunar 1- - valves are usually devoid of vessels ex- --^ V , cept at their base. The best figures of V theblood-vesselsof the valves aregiven —~ ^ ^ by Langer and Darier. The network of lymphatics in the endocardium reaches -p,. towards the middle of the valves. Weightof the Heart.—According to Pui'kinje's fibres isolated with dilute alcohol. 6',^cell; W. Müller the proportion between °he /' striated substance ; 11, nucleus. x 300. weight of the body and the heart in the child, and until the body reaches 40 kilos, is 5 crrms of heart-substance to 1 kilo, of body-weight; when the body-weight is from 50 to 90 kilos, the ratio IS 1 kilo, to 4 grms of heart-substance ; at 100 kilos. 3-5 grms. As age advances, the auricles become stronger. _ The right ventricle is half the weight of the left. The weight of the heart of an adult man is about 309 grms. ; female, 274 grms. [According to Laennec the heart is about the size of the closed fist of the individual] Blosfeld and Dieberg give 346 amis for ^ n«a ^° 340 grms for the feniale heart. The specific gravity of the heart-muscle is 11 l ! ventricle in the middle in man is 11-4 mm., and in woman 11-15 ; that ot the right is 41 and 3-6 mm. respectively. 47. AUTOMATIC REGULATION OF THE HEART.-Anatomatical Investigations -The two coronary arteries arise from the first part of the aorta in the region of the sinus of Valsalva Ihe position of origin varies—(1) either the orifices lie within the sinus, or (2) their openines are only partially reached by the margins of the semi-lunar valves (which is usually the case in the left coronaiy artery of man and the ox), or (3) their orifices lie clear above the margins of the valves. Tost-mortem observations seem to show that during contraction of the ventricle it IS jery improbable that the semi-lunar valves constantly cover the origin of the coronary Automatic Regulation of the Heart.—Brücke attempted to show that during the systole, or contraction of the ventricle, the semi-lunar valves covered the openmgs 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- (6) on the contrary, a systolic filling of these arteries would oppose the contrac- tion, _ because the systolic filling and expulsion of the blood from the coronary arteries would dimmish the force of the ventricular contraction. [To this p.$