Vaginal anatomy of the domestic cat (Felis catus) in relation to copulation and artificial insemination.

In the course of an investigation of artificial insemination (AI) in the domestic cat, the site of deposition of the semen during vulval insemination was questioned. A limited study was carried out to ascertain both the anatomy and distensibility of the vagina and urogenital sinus, and the location of the cervix in relation to the vulva. In live restrained female cats a 4 mm diameter Teflon probe could not be inserted more than 20 mm, and elicited a cry similar to the copulatory vocalization when the resistance was encountered. However, a 1 mm diameter ball-tipped needle was passed to a depth of 40 mm. To confirm these observations, four adult female domestic cats were dissected. The cervix was located approximately 45 mm cranial to the vulva. The urogenital sinus narrowed approximately 17.5 mm from the vulva, preventing the passage of a 4 mm probe, and led to a constricted vagina, which permitted the passage of a 1 mm diameter probe to the depth of the cervix. A radiological investigation of a single anaesthetized cat supported these results. The erect penis of the adult male was measured during sexual arousal in five animals; the mean length and width (+/- SD) was 21.2 +/- 2.2 mm and 5.1 +/- 0.5 mm, respectively. These observations lead us to conclude that the stimulus for vocalization during natural mating is distention of the posterior vagina, where semen is probably deposited. The site of semen deposition is uncertain in several accounts of artificial insemination, as the passage of the insemination device depends on its diameter.