Carpenter's principles of human physiology . structure and * See Princ. of Comp. Phys., chap. v. A very full and comprehensive account of thecirculation and the apparatus by which it is effected in plants, in the lower animals, andin Man, will be found in Dr. J. Bell Pettigrews work on the Physiology of the Circu-lation, 1874. t Luschka, quoted in Krauses Histologie, 1876, p. 299, and in Freys Histology,Barkers translation, 1874, p. 403. % Phil. Trans., partiii. 1864,p. 445. § Journ. of Anat. and Physiology, vol. iv. 1870, p. 83. OF THE CIRCULATION IN GENERAL. 273 functional actions of the two
Carpenter's principles of human physiology . structure and * See Princ. of Comp. Phys., chap. v. A very full and comprehensive account of thecirculation and the apparatus by which it is effected in plants, in the lower animals, andin Man, will be found in Dr. J. Bell Pettigrews work on the Physiology of the Circu-lation, 1874. t Luschka, quoted in Krauses Histologie, 1876, p. 299, and in Freys Histology,Barkers translation, 1874, p. 403. % Phil. Trans., partiii. 1864,p. 445. § Journ. of Anat. and Physiology, vol. iv. 1870, p. 83. OF THE CIRCULATION IN GENERAL. 273 functional actions of the two divisions of the Heart, which should be hereadverted to.—The walls of the left Ventricle are considerably thicker than thoseof the right; and its force of contraction is much greater. The following arethe comparative results of M. Bizots measurements,* taking the average otMales from 16 to 79 years:— Base. Middle. Apex. Left Ventricle . . 4i lines ... 5& lines ... 3| lines. Right Ventricle 1H- H 1§ lines 14* lines. Fig. Segment of human semilunar valve from the pul-monary artery suspended from the fibrous band a, a,x. r. Lunula?, which when the valve is in actionbecome accurately applied to corresponding lunulain the two remaining segments, c, Corpus Arantii,or portion usually thickened in old, though not inyoung people; n, thickened convex border attached tofibrous ring of pulmonary artery ; o, thinner portionof segment, s s Fibrous bands which break up inthe mesial line of the segment to support andstrengthen it. Fig In the Female, the average thickness is somewhat less. It will be seen that thepoint of greatest thickness in the leftVentricle is near its middle; while in theright, it is nearer the base. The thick-ness of the former goes on increasingduring all periods of life, from youthto advanced age; whilst that of thelatter is nearly stationary. During preg-nancy there is an hypertrophy of theleft Ventricle to the extent of l-4th oreven 1-ord of the original
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