REGULATION OF TEMPERATURE. 
353 
its volume or weight fco its surface, Eor weight or volume iucreases as the 
cube, surface iucreases as the square. Thus, if the dimensions of a body 
be increased from 1 to 2, the surface increases from 1 to 4, and the cubic 
content from 1 to 8. A small animal, therefore, has a far greater 
surface in relation to its weight than a large animal, and if it is to 
maintain its temperature at a similar height, it must have either special 
means for preventing an excessive loss of heat or a more rapid produc- 
tion of heat. Both of these means are employed, and so effective are 
they, that the temperature of the smallest mammals and birds is often 
higher than that of the biggest, A mouse has a thicker covering 
of hair, and, relatively to its weight, a greater production of heat, than a 
horse. Further, as remarked by Bergmann, the smaller animals need a 
relatively greater supply of food. 
The large animals living in the tropics, such as the elephant and 
hippopotamus, are often remarkable for the small amount of hair upon the 
body and for their love of bathing, whereby the loss of heat is favoured. 
The largest mammals, the whales, are able by means of their enormous 
size and special layers of fat to resist the cold of the Arctic seas, and 
maintain a temperature equal to that of mammals living in the tropics. 
Water-fowl, especially those which inhabit cold regions, are noted for 
the protection afforded against cold by their down and feathers. 
These indications from the natural history of animals are fully con- 
firmed by experimental observations. The determinations made by 
Letellier, 1 and by Begnault and Keiset, 2 show that the intake of oxygen 
and the output of carbon dioxide are relatively greater in small than in 
large animals :; : starvation is more rapidly fatal to small than to large 
animals, 4 for during life they consume a relatively larger quantity of 
proteid. 5 Further, Bubner G has determined the heat production of dogs 
of different size, and finds that the smaller animals produce relatively 
more heat in proportion to their weight than the larger animals, and that 
the heat production is proportional to the surface of the body. The 
folio wing table sives some of these results : — 
Weight. 
Surface. 
Surface per Kilo. 
Weight. 
Heat Production per 
Kilo, per Day. 
Air=15°. 
Heat Production per 
Square Metre of 
Surface. 
Kilo. 
31-2 
18-2 
9-6 
6-5 
3-19 
Sq. Cm. 
10,750 
7662 
5286 
:J724 
2423 
Bq. Cm. 
344 
421 
550 
573 
726 
Kilo-cal. 
35-68 
46-20 
65-16 
66-07 
88-07 
Kilo-cal. 
1036 
1097 
1183 
1153 
1212 
Similar results have been obtained by Langlois 7 in the case of 
children. 
1 Ann. de chim. et phys., Paris, Ser. 3, tome xiii. p. 478. 
2 Ibid., 1849, tome xxvi. p. 299 ; 1863, tome lxix. p. 129. 
3 See article "Chemistry of Respiration," this Text-book, vol. i. pp. 706-8. 
4 Chossat, "Recherches expeVimentales sur l'inanition," Paris, 1843. 
5 Voit, Hermann's "Handbuch," Bd. vi. S. 88. 
6 Ztschr.f. Biol., Miinchen, 1S83, Bd. xix. S. 535. 
7 Centralbl.f. Physiol., Leipzig u. Wien, 1887, S. 237. 
