884 SPECIAL PHYSIOLOGY. 



whether in excess or deficiency, or whether absolutely withdrawn, as 

 in starvation, and to exercise (pp. 842-847), which increase the activity 

 of the respiration and the amount of carbonic acid given off, raise the 

 temperature of the body ; whereas all those which diminish the respi- 

 ratory actions and their chemical products, lower that temperature. 

 The relations, as to respiration and temperature, in the lower animals, 

 confirm this view. It has been objected, that not only the respiratory 

 function, but all the other functions of the body, are similarly modified 

 under the above-named conditions ; and that, therefore, the variations 

 of temperature may be referable to other processes as well as to the 

 respiratory interchanges. But since no function of the body whatever, 

 whether it be that of sensation, the guidance of motion, motion itself, 

 nutrition, secretion, or any other function, can be performed without 

 concomitant changes in the chemical molecules of the tissues or organs 

 concerned, and as all these changes are but steps or stages towards a 

 more or less complete oxidation, so any production of heat by them 

 must ultimately be referred to this chemical action. According to any 

 other view the heat would be produced from nothing, or without that 

 accompanying conversion or change in the condition of force and mat- 

 ter, which we now know is necessary for its production. 



The Cold-blooded animals expire but small quantities of carbonic 

 acid, and their respiration is feeble ; whilst opposite conditions are 

 noticeable in the Warm-blooded animals. The most active of these 

 latter give off more carbonic acid, and manifest a higher temperature, 

 the Carnivorous Mammalia being, in both these respects, above the 

 Herbivorous, the smaller quadrupeds above the larger ones, and, as a 

 Class, the Birds above the Mammals. The relative complexity of the 

 pulmonary organs, the extent of the respiratory surface for the ex- 

 posure of the blood in the capillaries, and the contrivances for the 

 more frequent renewal of air in the air-cells, keep pace with the 

 increase of temperature in the animals themselves. In the hottest 

 animals known, viz., Birds, special peculiarities exist in the air-cells, 

 and the air-cavities in the bones, with which are associated great force 

 of the heart, great rapidity of its action, a high rate of motion of the 

 blood through the capillaries, a large number of red blood corpuscles, 

 a small amount of evaporation from the skin, and a solid condition of 

 the urinary excretion, involving less loss of heat in its production than 

 if it were fluid. The urinary products of Birds are, moreover, chiefly 

 composed of urate of ammonia, which contains less oxygen than urea, 

 so that more of that element passes off as carbonic acid. (J. Davy.) 



The importance of the relation between the quantity of the red cor- 

 puscles in the blood, and the temperature of the body, is illustrated 

 by the following numbers, which show the quantity of dried solids of 

 the clot, in 1000 parts of blood, in a series of animals belonging to 

 the several Classes of the Vertebrata. The hen, 157.1 ; the dog, 

 123.8; the tortoise, 80; the frog, 69; and the eel, 60 parts in 1000. 

 (Prevost, Dumas, J. Marshall.) 



Animal heat being regarded as the result of a process of oxidation, 

 the small amount generated by the Cold-blooded animals may be 

 supposed to be derived from the metamorphosis of their own tissues or 

 blood. The same may be true as regards the large Carnivorous animals, 



