ABSTRACT
In our previous paper (1934) it was shown that the recurrence of oestrus in the female ferret is greatly accelerated by irradiation with light, and is retarded by darkness, thus confirming and extending the observations of Bissonette (1932). It was also shown that heat rays and the near infra-red (λ7500Å.) were inactive. The active radiation extended throughout the spectrum from the red (λ 6500 Å.) to the ultra-violet (λ3650Å.). Further, the animals irradiated with ultra-violet light remained on heat far longer than any of the others, although the irradiation had been for a long time discontinued. Of the two ferrets which are recorded as having been still on heat on August 1, 1933, one (No. 2) remained in a state of full oestrus until August 28, but the vulval swelling did not finally disappear until October 2, while the second ferret (No. 14) began to go off heat on September 11, but was not completely anoestrus until November 14.
The intensities were measured with a quartz screen in front of the thermopile so that the very long heat radiation was not included.
The “normal” time for coming on heat is taken as being the same as that recorded in our previous paper, viz. 146 days from December 1. The results for the normal control ferrets during the present year fully confirmed the previous observations, the animals coming on heat at the end of March or beginning of April.
