The Anatomical And Histochemical Properties On The Skin Of The External Genitalia Of The Primates

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Abstract
The thickness of epidermis, development of epidermal ridges, complexities of subepidermal blood capillaries, size of genital corpuscles, and the combined presence of apocrine and eccrine glands in the external genitalia of primates show some phylogenetic ascendancies. The distribution of both epidermal and dermal melanotic melanocytes shows such remarkable species, sexual, and regional differences that phylogenetic significances are not confirmed. In the gorilla, chimpanzee, yellow baboon, Celebes ape, woolly monkey, howler monkey, and tamarin, the epidermis is heavily pigmented. The dermal melanocytes, absent in the lowest prosimians and highest simioids, are abundant in the Cercopithecidae. In most of the subhuman primates, the melanocytes, absent in the epidermis, are present in the dermis and vice versa. A unique characteristic is the presence of melanocytes in the apocrine glands of the tamarin, in the eccrine sweat ducts of howler and woolly monkeys, and around the blood vessels of green and Sykes'' monkeys. Similar unique features are: the alkaline phosphatase-positive dendritic cells in the epidermis of 5 species of African Lorisidae; the alkaline phosphatase-positive hair follicle nerve end-organs in the tree shrew, lesser bushbaby, potto, and woolly monkey; and the alkaline phosphatase in the sebaceous glands of the tree shrew, mongoose lemur, ringtailed lemur, tamarin, squirrel monkey, rhesus monkey, and baboon. The eccrine glands are enwrapped by acetylcholinesterase-rich nerve fibers in the tree shrew, woolly monkey, green monkey, pigtailed macaque, Celebes ape, and gorilla as well as in man. The content ratio of acetyl- and butyrylcholinesterase indicates remarkable species differences.