850 



ANIMAL HEAT. 



Forbes l 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*1 for the male, and 33'8 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 (Thynnus pelamys) to be 37'2, 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 lacked 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 Barensprung 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 EEGULATION 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 : 



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. 

 "Researches," London, 1839, vol. i. p. 219. 



3 Pembrey, Gordon, and Warren, Journ. PhysioL, Cambridge and London, 1894-95, 

 vol. xvii. p. 331. 



4 Arch.f. Anat., Physiol. u. wissensch. Med., 1851, S. 131. 



