the description of the valves. The walls of the left ventricle, which are nearly half an inch in thickness, are, with the exception siderably less. The latter condition is adapted to the small amount of force which the auricles require in order to empty themselves Fig.92.-Network of muscular fibres (striated) from the heart of a pig. The nuclei of the muscle-corpuscles are well shown. X 450. (Klein and Noble Smith.) into their adjoining ventricles; the former to the circumstance of the ventricles being partly filled with blood before the auricles contract. Size and Weight of the Heart.The heart is about 5 inches long, 3 inches greatest width, and 21 inches in its extreme thickness. The average weight of the heart in the adult is from 9 to 10 ounces; its weight gradually increasing throughout life till middle age; it diminishes in old age. Structure. The walls of the heart are constructed almost entirely of layers of muscular fibres; but a ring of connective tissue, to which some of the muscular fibres are attached, is inserted between each auricle and ventricle, and forms the boundary of Fibrous tissue also exists at 1 Spectrum of Argand-lamp with Fraunhofer's line's in position 2 Spectrum of Oxyhemoglobin in diluted blood. 3 Spectrum of Reduced Hemoglobin. Spectrum of Carbonic oxide Hæmoglobin. 5 Spectrum of Acid Hæmatin in etherial solution. 6 Spectrum of Alkaline Hæmatin 7 Spectrum of Chloroform extract of acidulated Ox-bile. 10 Spectrum of Hæmatoporphyrin Most of the above Spectra have been drawn from observations by ME W Lepraik FCS. |