Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . , fig. 150a back view of the humerus ;fig. 151, the round head andtubercles (3, 4) ; fig. 152,the lower surface of the con-dyles, (15) is the surface onwhich the head of the radiusplays, (16) receives the sig-t, moid cavity of the ulna, and(17) is a groove for the pas-sage of the ulnar nerve. [§ 273. The fore-arm con-sists (fig. 153) of two bones,the RADIUS and the ULNA,which are the homologuesof the tibia and the bones lie n
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . , fig. 150a back view of the humerus ;fig. 151, the round head andtubercles (3, 4) ; fig. 152,the lower surface of the con-dyles, (15) is the surface onwhich the head of the radiusplays, (16) receives the sig-t, moid cavity of the ulna, and(17) is a groove for the pas-sage of the ulnar nerve. [§ 273. The fore-arm con-sists (fig. 153) of two bones,the RADIUS and the ULNA,which are the homologuesof the tibia and the bones lie nearly pa-rallel to each other, the ra-FiS- 15i- FiS- 152- dius (1) on the outer, and the ulna (11) on the inner side of the arm; they are united byligaments, and by a fibrous membrane stretched across theinterspace between them; they have, however, a considera-ble range of motion upon each other and upon the flexion and extension of the forearm is performed by theulna (1), which forms, with the humerus, a true hinge its upper part we observe the olecanon process (), which locks into a cavity (fig. 150, 19) on the posterior. OF THE FORE-ABM. 145 surface of the hurnerus ; which acting as a stop, renders exten-sion beyond the straight line impossible. The hand is attachedto the lower end of the radius ; and as that part was Yig. 153designed to perform pronation and supination, apeculiar mechanical provision was necessary forthese important motions. The round head of the ra-dius (fig. 153, n) is bound by a firm annular liga-ment to the ulna (i), and the concavity on its sur-face is received in a corresponding convexity on theouter condyle of the humerus. Hence both bonesmove upon the humerus, in acts of flexion andextension, whilst the radius rolls upon the ulna,carrying with it the hand in pronation andsupination, separate sets of muscles being as-signed to each class of movements. It is only amongthe higher mammals that any motion is permittedbetween
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
