114
SEASONAL VARIATION IN REACTION TIME
[Vol. XXII, Part II,
Average monthly variations in 'reaction-time' and in semen characteristics
are presented in fig. I. From the figure it will be seen that the curve for 'reaction-
time' did not show any definite monthly variation. Curve for volume showed
a tendency to follow those for sperm concentration and total number of sperma-
tozoa. Curves for initial motility and pH did not show wide monthly fluctuations.
There is, however, an indication that the average pH was high during the second
year than during the first year. The curves for sperm concentration and the total
number of spermatozoa are more or less of the same type, showing a definite monthly
variation. There was a gradual decrease in both of these characteristics from April
to September after which there was a progressive increase. During the second year,
as opposed to pH of semen, both of these characteristics were low in comparison
with the first year. The curve for abnormal spermatozoa has two peak points in
the first year, one in January and the other in August, and in the second year, one
in September and the other in December. The high percentage of abnormal sperma-
tozoa in August and September was due to preponderance of tailless spermatozoa,
whereas in December and January it was due to bent tail ones.
For the purpose of studying the effect of seasons on 'reaction-time' and semen
quality the local seasons were distinguished as follows :
August to October
November to January
February to April
May to July
Autumn
Winter
Spring
Summer
Average 'reaction-time' and characteristics of semen of the rams in different seaons
are presented in Table II. Perusal of the table reveals no relationship between
the 'reaction-time' and the quality of semen produced in different seasons. There
was not much difference in the average 'reaction-time' between autumn and spring;
but judged by all the attributes of semen studied, the quality of semen in autumn
was decidedly inferior to that in spring. Percentage of abnormal spermatozoa
in autumn and winter was comparatively higher than in other two seasons. This
was because in autumn and winter large numbers of tailless and bent-tail sperma-
tozoa respectively were found in the ejaculates.
Mukherjee and Bhattacharya [1947] who studied the seasonal variations in
semen and blood qualities of bulls during the same period, when this experiment
was conducted, found that relative humidity and rainfall were highest in autumn
and lowest in spring. Average air temperature in autumn was almost as high
as in summer. Air temperature in spring was moderate. It seems, therefore,
that when air temperature was moderate with scanty rainfall and lowest humidity
as in spring the semen quality of rams improved. Whereas, in autumn when the
air temperature was very high with high humidity and rainfall the semen quality
deteriorated.
The data on 'reaction-time' and on semen characteristics were subjected to
analysis of variance. The summary of the results of analysis are presented in
Table III. The table shows that in 'reaction-time' and in all characteristics of
semen studied (except in initial motility of spermatozoa) there was highly significant