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Summary.

The most important results indicated are:–(1) the left hand and foot are longer than the right hand and foot, but the toes of the right foot are more mobile than those of the left. (2) Antagonism of the dexterity of the extremities (a, the left hand is more mobile than the right; b, the right foot is more mobile than the left). The gorilla is left-handed and right-footed. (3) The hand and foot of the gorilla are more similar to the extremities of man than the hand and foot of the orang utan and the chimpanzee. (4) Four crease-lines of the hand demarcate the hollow of the palm by a quadrangle. (5) The crease-lines differ only slightly in each hand. (6) The papillary ridges on the fingers are more primary than those of man. The papillary ridges on the balls at the base of the fingers are more complicated than those of man. (7) The papillary ridges on the terminal phalange of the thumb are like those of a special type on the human thumb. (8) The papillary ridges on the thumb show the same conformation on both phalanges, differing only in position. The papillary ridges on the thumb merit special consideration. For thousands of years the thumb-print has been a method of identification, and there is much evidence that the papillary ridges, especially those of the thumb, have a correlation with the gyri of the brain, as stated by Alix and Kollmann. The latter even names the papillary ridges “gyri of the skin,” and says that the development of the gyri of the skin is analogous to that of the gyri of the brain.

The papillary ridges on the gorilla's thumb are quite different from those on the fingers. They differ (1) by a more complicated conformation similar to man, and (2) by the fact that they are alike on both phalanges.

This is of unusual psychological interest. We do not find this arrangement of papillary ridges in any of the primates or in man. If we assume that there is a correlation of the gyri of the skin and those of the brain, the phenomena described may reveal a different mentality and perhaps even temperament of the gorilla. Also owing to the unique conformation on the second phalange of the thumb it is possible that the gorilla has some highly developed mental functions which are not found in man.