Sex Characteristics in Monkeys.

Abstract

Female monkeys during sexually mature life show the sex characteristics of reddening and swelling of the skin about the external genital organs, on the buttocks and medial surfaces of the thighs. These phenomena disappear after double ovariectomy and can again be induced in spayed animals by injections of ovarian and placental extracts. 1 Three male monkeys in our colony had never shown this cutaneous reddening. (It has, however, been reported that male monkeys may show this reddening during the breeding season.) During the late summer and fall the 'sexual skin'rf a large 7-year-old male began to redden. During November and December the regions affected covered an area 15×13 cm. in extent. The reddening reached a moderate intensity but never approached the maximum 'sexual skin'rolor of the mature female. From our experiments with ovarian hormone in inducing this condition in spayed animals, it seemed logical to infer that this condition in the male might be due to the male sex hormone.

Needels 2 had previously reported a series of blood tests in our monkeys by a modified Manoilov technique, a test supposed to distinguish male from female blood. To our great surprise the blood of this fully grown, finely developed, 6-year-old male had consistently given a'lemale'reaction. Two younger males, one of which was immature, returned typical'lale'rests. This test seemed essentially a reduction reaction, the male blood usually causing a greater reduction of the reagents than the female blood. But Needel's results indicated fluctuation especially in females when tests were repeated upon the same individuals. Consequently a graded series of color standards were prepared for comparison. The tests ranged from no decolorization (‘female’) to complete decolorization (‘male’).

Several conclusions were drawn : (1) There was a distinct variation in individual female monkeys during the menstrual cycle.