1. The temperature of the scrotal surface has been recorded at various air-temperatures
within the range 10°C. to 40°C. (50°F. to 104°F.).
2. At low air-temperatures (10°C. to 25°C.) the temperature on areas I,
II, and III gave a mean value of 32.0°C., 31.0°C., and 33.0°C.; at high
air-temperatures (25°C. to 40°C.) the same areas were 33.9°C., 33.8°C., and
3. Readings (28) of the skin-temperature underneath the hairy coat, taken
simultaneously, gave mean values of 33.6°C. at low air-temperatures and 36.5°C. at high air-temperatures.
4. The mean body-temperature at which the high temperature group
readings (15) were taken was 38.6°C.
5. Scrotal temperatures at areas I and II increased almost similarly with
increasing air-temperature, i .e. slow increase at low air-temperatures (0.06°C.
and 0.09°C. per 1° air-temperature increase) and more rapid increase at high
air-temperatures (0.29°C. and 0.26°C. per 1° air-temperature increase).
Scrotal temperatures of area III and skin-temperatures increased similarly
with increasing air-temperature over the whole range of 10°C. to 40°C. air-temperature. The rate of increase for scrotal area III was 0.43°C. at 10°C.
air-temperature, and 0.11°C. at 40°C. air-temperature. The rate of increase in
the skin was 0.56°C. at 10°C. air-temperature, and 0.14°C. at 40°C. air-temperature.
6. The degree of contraction and relaxation of the scrotum, as indicated
by its length from the dorsal to the ventral extremity, gave a mean value of
24.2 cm. at low air-temperatures and 29.0 cm. at high air-temperatures, a
difference of 4.8 cm.
7. From limited observations on the body-temperature, at high air-temperatures
only, there appears to be a highly significant relationship between
the body-temperature and that o£ the air and scrotal areas I, II, and III. There
was no significant relationship between body and skin-temperature.
8. An observation was carried out at artificially created low air-temperatures.
The bull was exposed to a temperature of 4°C. to 6°C. for six hours.
9. Under these conditions scrotal area I increased immediately from 30°C.
to 33°C. It then decreased and fluctuated between 31°C. and 32°C. During
the following 4 hours, scrotal area II always showed lower temperatures than
area I (up to 3°C.) . Scrotal area III increased markedly at the beginning and
then showed a slight tendency to decrease, but after one-and-a-half hours
remained 2°C. to 4°C. lower than skin-temperature.
10. There was marked shivering, which began one-and-a-half hours after
exposure, and continued until one-and-a-half hours after the bull was removed
from the cooling chamber.
11. The pulse rate per minute varied from 66 to 62 in the cooling chamber
and dropped from 64 to 58 within an hour after removal.
12. The respiration count was 16 per minute after six hours exposure and
13 per minute one hour after removal. ·
13. The skin-temperature showed steady increase, up to 35°C. (air-temperature
4°C.). It then decreased continually to 32.6°C. at the end of the
experiment, but a constant level had apparently not been reached. After removal
from the cooling chamber, there was an increase of 3°C. within an hour.
14. The length of the scrotum decreased with a fall of scrotal and skin-temperature
during exposure. There was marked relaxation upon removal to
15. The body-temperature increased by 1°C. at the commencement of
exposure, and remained remarkably constant at about 39°C. throughout the
exposure and after removal from the cooling chamber.
16. The intra-testicular temperature, measured with a thermo-needle, at
an air temperature range of 15·2° C. to 37·8° C. remained within a narrow
range, between 34.8°C. to 37°C. for the left testicle and 34.7°C. to 36.6°C.
for the right testicle.
17. Artificial displacement of the testicle to close contact with the body
resulted in an increased intra-testicular temperature of 2.5°C. and a decrease
in the temperature of the scrotal area not overlying the testicle, of 6.0°C. and
3.2°C. The scrotal surface over the displaced testicle also increased considerably
18. The heat regulating mechanism of the scrotum is extraordinarily
efficient in maintaining the testicular and scrotal surface-temperatures within
a very narrow range at air-temperatures between 10°C. and 40°C. It is suggested
that this efficiency is not purely physical, due to the action of air temperature
on the contracted or relaxed scrotum. This suggestion is strengthened
by the fact that scrotal areas I and II, in close contact with the testicle, behaved
similarly but differently -to scrotal area III and the skin. It appears probable
that vascular reaction accompanies scrotal contraction and relaxation.
19. The scrotal temperature reaction over that portion of the scrotum
removed from close testicular contact, is extraordinary in that there was a very
marked decrease in temperature to 28.2°C., i.e. 3.8°C. lower than air-temperature,
and 8.8°C. lower than intra-testicular temperature (average for
points 1 and 2). It is suggested that this reaction was an attempt by the
temperature regulating mechanism of the scrotum to maintain the testicular
temperature, which was raised by contact with the body , at the normal temperature
for prevailing air-temperature.