REGULATION OF TEMPERATURE. 



853 



its volume or weight to its surface, for weight or volume increases as the 

 cube, surface increases 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 Eegnault and Keiset, 2 show that the intake of oxygen 

 and the output of carbon dioxide are relatively greater in small than in 

 large animals 3 ; starvation is more rapidly fatal to small than to large 

 animals,* for during life they consume a relatively larger quantity of 

 proteid. 5 Further, Eubner 6 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 

 following table gives some of these results : 



Similar results have been obtained by Langlois 7 in the case of 

 children. 



1 Ann. de chim. et phys., Paris, Se>. 3, tome xiii. p. 478. 



2 Ibid., 1849, tome xxvi. p. 299 ; 1863, tome Ixix. p. 129. 



3 See article "Chemistry of Respiration," this Text-book, vol. i. pp. 706-8. 



4 Chossat, "Recherches expe"rimentales sur 1'inanition," Paris, 1843. 



5 Voit, Hermann's "Handbuch," Bd. vi. S. 88. 



6 Ztschr.f. JBioL, Miinchen, 1883, Bd. xix. S. 535. 



7 Centralbl.f. PhysioL, Leipzig u. Wien, 1887, S. 237. 



