Outlines of human physiology . Of the Semilunar Valves. 69 The first figure of the two preceding represents thesemilunar valves half raised, as they appear upon slit-ting open the aorta or pulmonary artery. Fig. 2 representsthe ventricular surface of the valves when thrown am tempted to add another drawing from a specimenwhich I recently met with. Instead of three crescenticfolds, the semilunar valve of the aorta consisted but oftwo; yet though monstrous, the construction of thevalve was perfect, each of the two flaps being propor-tionately larger than usual, and strengthened by acentra
Outlines of human physiology . Of the Semilunar Valves. 69 The first figure of the two preceding represents thesemilunar valves half raised, as they appear upon slit-ting open the aorta or pulmonary artery. Fig. 2 representsthe ventricular surface of the valves when thrown am tempted to add another drawing from a specimenwhich I recently met with. Instead of three crescenticfolds, the semilunar valve of the aorta consisted but oftwo; yet though monstrous, the construction of thevalve was perfect, each of the two flaps being propor-tionately larger than usual, and strengthened by acentral band extending towards the sesamoid valve at the root of the pulmonary artery in thisheart presented no uncommon The heart is supplied with blood from the two coro-nary arteries, which are the first branches of the aorta;it has a large supply of lymphatic vessels; its nerves arederived from the sympathetics and nervi vagi. 70 Nature of Arteries and Vei?is. An artery is a cylindrical and highly elastic tube; itsthick texture is separable into, 1. An inner serous coat:2. A middle fibrous coat, of a yellow colour in thelarger trunks, of a redder hue in the smaller branches,composed of fibres, which are disposed transversely,but seem in some degree interwoven; they are veryelastic, and at the same time so brittle, that the pres-sure of a ligature tied upon an artery cuts through thefibrous together with the inner coat: and, 3. An outercellular coat, consisting of tough white elastic fibresclosely interwoven, which the pressure of a ligaturedoes not divide. Dr. Hales ascertained that the forcerequired for bursting one of the carotids of a dog, isequal to that of a column of water one hundred andninet
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