. Biology of the laboratory mouse. Mice as laboratory animals; Mice; Animals, Laboratory; Mice. 64 BIOLOGY OF THE LABORATORY MOUSE these conditions, survival of primitive germ cells for at least 115 days has been recorded (91). The high mortality among ova under normal conditions can be appreci- ated from figures presented by Allen (4). An average of 800 to 1000 ova are differentiated in the two ovaries of a female mouse at each estrous period, while only about 9 ova of an earlier generation mature. The percentage of survival is thus about 1%. Brambell (19) has made an interesting study of the
. Biology of the laboratory mouse. Mice as laboratory animals; Mice; Animals, Laboratory; Mice. 64 BIOLOGY OF THE LABORATORY MOUSE these conditions, survival of primitive germ cells for at least 115 days has been recorded (91). The high mortality among ova under normal conditions can be appreci- ated from figures presented by Allen (4). An average of 800 to 1000 ova are differentiated in the two ovaries of a female mouse at each estrous period, while only about 9 ova of an earlier generation mature. The percentage of survival is thus about 1%. Brambell (19) has made an interesting study of the growth of oocyte and follicle, finding the relation shown in Fig. 33. It will be seen that at first both oocyte and follicle increase in size, the relation between the two being 70 50 so- lo. 600 200 300 400 500 DIAMETER OF FOLLICLE Fig. ^^.—Graph showing the relation between oocyte size and follicle size. {From Brambell 1928.) linear. When the oocyte attains a diameter of approximately 70^1, and the follicle a diameter of 125 yu, the former stops growing while the growth of the follicle continues, so that the average follicle diameter at ovulation is 550 /z. The antrum first appears as an irregular fluid-filled cleft in the middle of the follicular cells on one side of the oocyte in follicles about 200 /jl in diameter. Ovarian regeneration.—As a result of reports in the medical literature of conception following complete double ovariectomy, there have been a number of experiments with mice and rats to determine whether or not there is any ovarian regeneration following removal of both ovaries. While the results have been conflicting, the most recent experiments seem to indicate that regeneration does not occur if the removal is complete (66, 107). If regeneration does occur it is probably the result of a small piece of ovarian tissue having been left. Regenerated ovaries contain follicles and may be fully functional (37, 105).. Please note that these images are extracted
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