SEXUAL ACTIVITY OF MALE RABBITS 489 
TABLE 4—Concluded 
AVERAGE HOURS PER CENT ACTIVE 
DATE TEMPERA- AFTER 
BER ireep VEEe, Ist 5th 10th 15th 20th 
Male 5 
1916 
6-15 16 2 0 0 2 
24 1 2 
24 28 0 it 
6-28 0 85 30 30 
4 70 20 15 
8 10 0 
12 60 
25 20 3 0 
data from another series of matings with a different stallion in 
support of the idea that the vitality of the sperm is reduced 
when the male is overtaxed but this case is not so demonstrative. 
Stigler (14, p. 219) obtained semen from a man two hours 
after a previous copulation and found that sperm from the 
latfer could successfully resist a high temperature for a longer 
time than the former. Held at 44.6°C. sperm from the first 
copulation ceased moving, but remained alive for 1 hour 45 
minutes while sperm from the second copulation were killed 
altogether between 10 and 45 minutes. In our work with the 
rabbit the duration of motion determinations were made on the 
specimens prepared for a study of the rate of motion, i.e., the 
semen was diluted with 9 volumes of Ringer’s solution. The 
conditions under which this work was done do not reduce, but, 
in fact, as will be shown, prolong the life of the sperm. The 
parcels of diluted semen were placed into small glass vials with 
cotton stoppers. These were all placed on the same shelf in 
the laboratory and were not exposed to direct sunlight, but were 
exposed to the varying temperatures of the room. On account of 
this temperature variation the results obtained on different days 
are sometimes not directly comparable, but the results from a 
series of specimens obtained within three or four hours of each 
other may be safely compared among themselves. 
Table 4 gives the data on duration of motion, and at the end of 
each series of observations the ‘average temperature’ is recorded. 
