SEXUAL ACTIVITY OF MALE RABBITS 491 
TABLE 5 
Duration of motion-‘natural’ semen compared with ‘diluted’ 
PER CENT ACTIVE 
HOURS 
DATE AFTER Ist 5th 10th 
RECOVERY 
Natural Diluted Natural] Diluted Natural Diluted 
10-13 28 0 70 | 
48 0 
11-14 28 15 30 
10-31 16 50 55 
28 40 45 
44 0 21 
52 0 
10- 6 20 30 50) > 
10-22 24 0 37 22 90 20 83 
44 5 30 0 16 
10- 1 20 0 72 
10-15 28 0 0 
11- 9 20 58 75 
24 21 29 
However, we feel that a study of the data as above suggested 
will leave one with a decided opinion that there is a well-marked 
tendency for the sperm in semen from the higher-service groups to 
show less ‘vitality’ or ‘potential energy,’ as measured by the 
duration of motion which they will display. 
Table 5 is inserted here to compare the duration of motion of 
sperm in semen as it was recovered from the female with sperm in 
semen diluted with ten volumes of an isotonic solution. The 
counts of ‘per cent active’ are much less accurate with undi- 
luted semen than with diluted because of the crowding of the 
sperm. Moreover, they are so close together that the agita- 
tion set up by one active individual may cause several others to 
appear active, whereas they are not actually of themselves motile. 
But the point at which all sperm are inactive may of course be 
determined with as great accuracy in one case as in the other. 
Though the table is not extensive, the deduction to be made 
from these figures is plain; namely, that sperm in diluted semen 
display a longer duration of motion than sperm in ‘natural’ 
semen. The probable cause of this phenomenon is that in the 
