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Show 50 PROF. GARROD ON THE INTERVERTEBRAL SUBSTANCE. [Feb. 6, It may not be out of place for me here to draw attention to one or two points which are associated with the erectness of the carriage of man, in contradistinction to the horizontal and oblique attitudes assumed by lower animals. The simple curve, concave ventrally, of the vertebral column of the higher Apes was most certainly shared by the human progenitor. In the young child it is found to exist. In its attempts to assume the upright carriage this progenitor must, equally certainly, have thrown the centre of gravity of its body directly above the hips, to do which it was necessary to bend the spine backwards. On account, however, of the thoracic region being rendered rigid by the attachment of its cage of ribs, and the sacrum being unmodifiable from its ankylosis, this flexion of the spine could only occur in the neck and loins; consequently the spinal flexures in man may be explained upon the assumption that the dorsal and sacral ventral concavities are the similar curves of the ancestral type, retained on account of the mechanical obstructions to their removal, whilst the ventral convexities of the yielding cervical and lumbar regions are the means by which the centre of gravity in the erect position is carried to a point directly above the hip-joints. This assumption of a vertical attitude by a creature originally differentiated for a horizontal position of its body, has produced but marvellously slight inconvenience. If it had resulted in many, man could scarcely have survived. There are one or two, however, which are most clearly traceable to this cause, including the painful tendency to prolapse, antiflexion, and retroflexion of the uterus in women, as well as crural hernia in both sexes, and inguinal hernia in the male. In mammalian animals with the body horizontal the weight of the uterus is transmitted to the abdominal walls, at the same time that the round and broad ligaments prevent it from leaving the pelvic region. In the Sloths and Bats these ligaments are still more called into play, on account of the peculiar attitudes assumed by them. No more satisfactory mechanism could be desired. But in the human species the condition is very different. The uterus is situated almost directly above the vagina; and the entire absence of any ligaments to suspend it, place it in a position of the greatest mechanical disadvantage, especially when congested aud depressed by stays. Unsupported, it frequently bends forward or backwards, or even drops into the cavity of the vagina, and there finding nothing to obstruct it, becomes completely prolapsed. Similarly in inguinal hernia, the abdominal walls being abnormally extended in connexion with the lumbar curve, the tendency to rupture in the region of the inguinal canal must be greatly increased, as it must likewise be by the downward tendency of the viscera. |