. Anthropoid apes. Apes. 170 ANTHROPOID APES. must be remembered that the comparatively short thumbs of anthropoids have not to be employed in so many different veays as the human thumb, and that we cannot therefore be surprised that the de- velopment of the short extensor is less complete. A special extensor muscle of the index finger is either altogether absent in the gorilla or very slightly developed, while it is very apparent in Eyldbates alhimanus (6, Fig, 53). In the chimpanzee. Fig. 53.—MuBcular system of the back of a gibbon's hand. I, The extensor carpi radialis longior and brevier.
. Anthropoid apes. Apes. 170 ANTHROPOID APES. must be remembered that the comparatively short thumbs of anthropoids have not to be employed in so many different veays as the human thumb, and that we cannot therefore be surprised that the de- velopment of the short extensor is less complete. A special extensor muscle of the index finger is either altogether absent in the gorilla or very slightly developed, while it is very apparent in Eyldbates alhimanus (6, Fig, 53). In the chimpanzee. Fig. 53.—MuBcular system of the back of a gibbon's hand. I, The extensor carpi radialis longior and brevier. 2, Abductor longus poUicis. 3, Extensor primi in- ternodii poliicis. 4, Extensor secundi intemodii polUcis. 5, Extensor communis digitorum. 6, Extensor indicis. V, Extensor minimi digiti. 8, Extensor carpi ulnaris. 9, First dorsal inter-osseous muscle. 10, Continuation of the same to index finger. 11, 12, The other inter-osseous muscles of this region. A, The posterior annular ligament. this muscle sends a tendon to the middle finger. In the orang there is one extensor common to the four fingers. In the gibbon's hand, this, as well as the other extensor and flexor muscles, is remark- able for its excessive slenderness. The manifold connections of the extensor tendons with each other are an interesting peculiarity (Fig. 53). In the chimpanzee I observed a superficial flexor,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hartmann, Robert, 1832-1893. New York, D. Appleton and Co.
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