REVIEW OF LITERATURE. 2 Reproductive Biology of the Guinea Pig 2 Hysterectomy-MATERIALS AND METHODS Hysterectomy Chemical Destruction of the Endometrium Uterine Transplantation Unilateral Ovariectomy and Partial Hysterectomy-Miscellaneous Observations on the Effects of Reproductive Hormones RESULTS AND DISCUSSION Hysterectomy Chemical Destruction of the Endometrium 43 Uterine Transplantation 45 Unilateral Ovariectomy and Partial Hysterectomy-48 Miscellaneous Observations on the Effects of Reproductive Hormones SUMMARY LITERATURE CITED 61 ACKNOWLEDGMENTS 71 REVIEW OF LITERATURE Reproductive Biology of the Guinea Pig The guinea pig under laboratory conditions is polyestrous the entire year. Estrus lasts less than half a day and the estrous cycle is about 16.5 days. Ovulation is spontaneous and the corpora lutea of the estrous cycle are functional. Gestation is about 67 to 68 days, with a litter size of about 3 to 4 (Asdell, 1946). Estrous cycle and gestation Ishii (1920) reported the age of puberty as 55 to 70 days. Young ejt al. (1939) stated the average age of puberty is 67.8 days with a range of 33 to 134 days. The vaginal opening is closed by a membrane except for a period of about 4 days at each estrus. Kelly and Papanicolaou (1927) described this structure as a solid epithelial vulvar cord extending 1 to 2 mm.; in depth. The opening of the membrane occurs at the inflamma tory stage of the sexual cycle. Opening is caused by the cornification and subsequent desquamation of the central part of the vulvar cord. Young e_t al. (1933) and Young e£ al. (1935) reported the average length of the estrous period as about 8 hours with a range of 1 to 18 hours. The former authors report ovulation occurs within an hour after the termination of estrus. Young et al. (1935) observed about 64 percent of all heats begin be
