The sexual behavior of three inbred strains of mice was studied. Sixteen different behavioral measures were scored; twelve of these sixteen measures revealed statistically significant behavioral differences. The results were as follows: I. C57BL males are characterized by speed. They gain intromission sooner, spend less time between intromissions, and ejaculate sooner than do the other two strains. 2. DBA/2 males show significantly longer intromission latencies, interintromissior. intervals, preintromission mount durations, and mounts than do the C57BL and BALB/c males. DBA/2 males ejaculate with fewer intromissions and thrusts than the other two strains. 3. BALB/c males require the longest time (over one hour), the greatest number of intromissions, and the greatest number of thrusts prior to ejaculation. The sexual behavior of the inbred strains of mice was compared to the sexual behavior of the rat, hamster, and guinea pig. Mention was made of the possibility for genitical and physiological studies of the behavioral differences.

Male mice were forcibly removed from oestrous females at times ranging from 1 to 7 sec following the beginning of the ejaculatory reflex. Females were then tested to determine if luteal activity had been induced. The results indicate that the stimulus inducing luteal activity in the female is initiated 3 or 4 sec after the beginning of the ejaculatory reflex. Observations of the penis during this reflex revealed a large increase in the diameter of the erect organ, particularly at the distal end. This anatomical change continued for 5 to 12 sec. It was suggested that the luteal-inducing stimulus is the mechanical stretching of the vagina and/or the cervix which results first from the swelling of the penis and is normally continued by the copulatory plug. Speculation concerning the events occurring during the transport of spermatozoa from the male to the uterus of the female is reported. Possible methods of improving the current techniques of artificial insemination in mice are discussed.

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The information elicited in this study is applicable to laparoscopic training.

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