866 ANIMAL HEAT. 
production of carbon dioxide fall, and they resemble cold-blooded animals. 
About the fifteenth day after birth, they respond to a fall in the temperature 
of their surroundings with increased muscular activity and output of carbon 
dioxide, and thus maintain their temperature (Pembrey 1 ). 
In the lowest mammals the temperature is much lower than in the higher 
members of the group. Thus the temperature of the Echidna hystrix is 27°'5, 
and that of the Ornithorhynchus, 24° •8.'-' 
Further, a hibernating mammal is an instance of an animal at one time warm- 
blooded and at another time cold-blooded, and its power of regulation is in 
many respects similar to that of an immature mammal."' Additional proofs 
of the gradual development of the power of maintaining a constant tempera- 
ture are found in the unstable temperature of infants and animals. In 
premature and weak infants the power is imperfect, and the temperature is 
below the normal. 4 It is in man that the perfection of this poAver is reached ; 
he of all animals has the most constant temperature under extreme differences 
of external heat and cold. 
It is impossible with our present knowledge to state what are the 
structural differences which accompany the development of the power of 
regulation. This much we may say : the power appears to be associated 
chiefly with the control of the nervous system over the skeletal muscles and 
those of the blood vessels. An anaesthetic, or curari, or section of the spinal 
cord reduces a warm-blooded animal to a cold-blooded condition ; its tempera- 
ture and production of carbon dioxide vary with, and in the same direction as, 
the temperature of its surroundings. In a hibernating animal the fall of 
temperature is accompanied by greatly diminished activity of the muscular 
and nervous systems ; and the sudden rise in temperature, when the animal 
awakes from its torpidity, is marked by a sudden increase in the discharge 
of carbon dioxide and in muscular activity. Those young mammals and birds 
which are born with well-developed control over their muscular system, are 
able to regulate their temperature even at birth, whereas those born in a 
helpless condition do not attain this power until a week or two after birth, 
at a time when their power of co-ordination is much increased. 
The Temperature of the Body after Death. 
After death the temperature of the body generally falls, the loss of heat 
varying according to the difference between the temperature of the corpse 
and that of its surroundings ; another important factor is the surface of the 
body in relation to its mass, for the corpse of an infant or of a wasted 
subject cools more rapidly than that of a well-developed adult. 5 In some 
cases, however, a rise of temperature is observed in the corpse, especially 
when death has resulted from tetanus, acute rheumatism, typhoid fever, small- 
pox, cholera, or injuries to the brain and spinal cord. A few of the cases 
recorded are given in the following table : — 
1 Journ. Physiol., Cambridge and London, 1895, vol. xviii. p. 363. 
- Mikloucho Maclay, Proc. Linn. Soc. Neio South Wales, 1883, vol. viii. p. 425 ; vol. ix. 
}). 1205 ; Semon, Arch. f. d. ges. Physiol., Bonn, 1894, Bd. lviii. S. 229. 
3 Pembrey and Hale White, Journ. Physiol., Cambridge and London, 1896, vol. xix. 
p. 477. 
4 Crombie, Indian Ann. Med. Sc., Calcutta, 1873, vol. xvi. p. 597; Randnitz, Ztschr. 
f. Biol., Miinchen. 1888, Bd. xxiv. S. 423. 
5 Taylor and Wilks, Guy's Hosp. Rep., London, 1863, p. 184 ; observations on one 
hundred cases ; Sutton, Brit. Med. Journ., London, 1874, vol. i. p. 153 ; Bidder and 
Schmidt, "Die Verdauungssat'te nnd der Stoffwechsel," S. 323 ; Womack, St. Barth. Hosp. 
Rep., London, 1887, vol. xxii. p. 193; Twderkorn, " De la rigidite cadaverique chez 
l'homme," Paris, 1872. 
