Further observations on the factors controlling fertility and foetal atrophy

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Abstract
Ina previous paper (1) some of the factors which control fertility in domestic animals were discussed. These for purposes of clearness in investigation were divided into two groups: (1) The factors which control the number of eggs shed; and (2) The factors which control the number of eggs which develop to reach birth size. By this means the way in which the various factors which affect fertility could be determined, for example, it was shown that the effect of age on fertility, the literature of which has been reviewed by Harris (2), is due to the number of eggs shed at each oestrus period. Young sows examined had on the average 14 corpora lutea in the ovaries while old sows had 20 corpora lutea.