File:Stockard Papanicolaou1917 figA.jpg

Length in Days of Guinea-pig Diestrous Cycle during the Year

--Mark Hill (talk) 20:41, 4 November 2013 (EST) Note these months relate to the northern hemisphere seasonal changes.

The curve shown in figure A indicates graphically this slight fluctuation, operated animals are excluded. The lowest average 15.50 days, or the shortest oestrous cycles, was found in the month of October, while the highest 16.14 days is shown during January. The heavy line at 15.82 days indicates the mean between these two extremes. It is probably not without significance that the averages during the months December, January, February, March and April fall above the mean line, while the averages during the months of May, June and October are below the line. From the cases considered this indicates that the length of the oestrous cycle is probably a little shorter during the warm time of the year and a little longer during the cold weather. We must, however, admit that the number of considered cases, as given in table 1, is actually small and these slight seasonal variations may be more suggestive than demonstrative in importance, yet there is certainly a striking consistency in their arrangement.

Links: Guinea Pig Development | Estrous Cycle

Reference

Charles R. Stockard and George N. Papanicolaou. The existence of a typical oestrous cycle in the guinea-pig— with a study of its histological and physiological changes. The American journal of Anatomy Vol 22.