8 5 o 
ANIMAL HEAT. 
Forbes a made similar observations, and found, as the average temperatures 
between the folds of the body, 30° and 31° - 7 in the case of the male and 
female respectively; the maximum was 32°'l for the male, and 33 0, 8 for 
the female. The greatest difference between the temperature of the air and 
the surface of the snake was 4°"6 in the male, and 5°"3 in the female ; between 
the air and the coils of the snake, 6°*4 in the male, and 9°*3 in the female. It 
is worthy of note that the female took no food and little exercise for many 
weeks before and during incubation. 
In some fishes a temperature several degrees above that of the water has 
been observed. Thus Davy 2 found the temperature of deep-seated muscles of 
the bonito (Thynnns pelamys) to be 37 0- 2, when that of the sea was 26° # 9. 
The tunny {Thynnus thynnus) is said to have a similar high temperature. 
The embryo of the chick must be looked upon as a cold-blooded animal, 
for it responds to changes of temperature in a similar manner, 3 yet even at an 
early stage the production of heat within its tissues can be shown to be 
considerable. Thus Biirensprung 4 found that the temperature of an egg on 
the fourth day of incubation was - 6 above that of a dead egg and *8 above 
that of the incubator. 
The Kegulation of Loss of Heat. 
An animal may lose heat in various ways — by direct conduction and 
radiation from the skin, by evaporation of sweat, by the warming of air 
during respiration and by evaporation from the different parts of the 
respiratory system, by raising cold food and drink to the temperature 
of its body, and by the discharge of urine and faeces. Loss of heat is 
controlled chiefly by the skin and the lungs. 
The distribution of the loss of heat by an adult man in twenty -four 
hours has been estimated by various observers as follows : — 
Vierordt. 
18 % by urine and faeces . . = 
3 '5% by expired air . . . . = 
7 - 2% by evaporation from lungs = 
H-5% ,, „ ,, skin = 
73 - 0% by radiation and conduction 
from skin 
47,500 calories. 
S4,500 
1S2.120 
364,120 
1,791,820 ,, 
2,500,000 
Helmholtz. 
= 2-6 50 
= 2-6% 
= 14-7%' 
=80-1 % 
2,732,000 
calories. 
Ludwig. 
Loss of heat by the skin— Radiation and conduction. — The 
amount of heat lost by radiation and conduction is, within certain 
limits, in proportion to the difference in the temperature of the body 
and of its surroundings ; the warmer the skin and the colder the 
surroundings, the greater will be the loss of heat. The heat of the skin 
is controlled by the cutaneous circulation, and this in turn is regulated 
by the central nervous system. The general result is that the cutaneous 
blood vessels are contracted, the circulation is smaller, and the skin 
pale and cold, when the external temperature is low ; on the other 
hand, the vessels dilate, the circulation becomes greater and the skin 
red and warm, when the temperature of the surroundings is high. 
1 Proc. Zool. Soc. London, 1881, p. 960. 
2 "Researches," London, 1839, vol. i. p. 219. 
3 Pembrey, Gordon, and Warren, Joum. Physiol., Cambridge and London, 1894-95, 
vol. xvii. p. 331. 
4 Arch. f. Anat., Physiol, u. wisscnsch. Med., 1851, S. 131. 
