. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. ACTIVITIES OF THE OVARY 75 While one Graafian follicle in only one ovary is generally developed in the human, monkey, cow, ewe, elephant, etc., at each reproductive period, a multiple condition is found in many other mammals. Each ovary in the opossum may ripen seven or more follicles, in the bitch (female dog) from 2 to 7 follicles, and in the sow from 4 to 10 follicles at each reproductive period. b. Structure of the Prototherian Egg Follicle Th
. Comparative embryology of the vertebrates; with 2057 drawings and photos. grouped as 380 illus. Vertebrates -- Embryology; Comparative embryology. ACTIVITIES OF THE OVARY 75 While one Graafian follicle in only one ovary is generally developed in the human, monkey, cow, ewe, elephant, etc., at each reproductive period, a multiple condition is found in many other mammals. Each ovary in the opossum may ripen seven or more follicles, in the bitch (female dog) from 2 to 7 follicles, and in the sow from 4 to 10 follicles at each reproductive period. b. Structure of the Prototherian Egg Follicle The follicle of the prototherian mammals contains a relatively large egg, while the surrounding fluid and follicular tissue in comparison is small in quantity (fig. 46). In these mammals the egg fills most of the follicular cavity, with the exception of a small fluid-filled space intervening between it and the zona pellucida which lies contiguous to the granulosa cells. Internal and external thecal tissues surround the granulosa cells as in the Graafian follicle of the higher mammals. c. Egg Follicles of Other Vertebrates The fully-developed egg follicle in most vertebrates is similar to that found in the prototherian mammals in that the egg tends to fill the entire follicle. The general structural relationships also are similar (figs. 45, 47). 6. Ovulatory Process; Possible Factors Controlling Ovulation The following description of the ovulatory process in the mammal and in other vertebrates should not be construed as a description of the mechanism, as the exact mechanism is unknown. However, a certain amount of general information has been obtained concerning ovulation and the factors involved. Much of this information has been obtained from studies of the ovulatory THECA INTERNA. CONTRACTED FOLLICLE AFTER EGG DISCHARGE OC ES S I ON Fig. 45. (A) Young egg follicle of Cryptohranchus alleganiensis, a urodele. (From Noble: "Biology of the Amphibia," New York, McGraw-Hill
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