ANIMAL BEAT. 345 



the latter consuming in the proportion of 100, and the former 

 150. 



At the stage where growth ceases, however, a diminution 

 is observed in the production of carbonic acid and the quan- 

 tity of animal heat ; not that the temperature is sensibly 

 lowered, for the greater the size of a body, the less is the loss 

 i that takes place by radiation ; the cold produced by radiation 

 affects an animal in proportion to its size, the surfaces by which 

 loss occurs varying in individuals of the same kind only by 

 squares, while the bulk varies by cubes; consequently an 

 adult who weighs eight times more than a child, has a surface 

 only four times as large, and loses, proportionately, only half 

 as much heat by radiation (2. 4. 8.) This explains the 

 fact that the smaller animals produce more heat (in propor- 

 tion to their weight and bulk) than the larger animals; the 

 fact being that they lose more by radiation and contact, on 

 account of their surface being larger (in proportion to their 

 bulk). 



Aged persons have less animal heat than adults, the phe- 

 nomena of nutrition and combustion being diminished in their 

 case. There is always a connection between the consumption 

 of oxygen and the production of carbonic acid and of heat 

 (see again, Physiology of the Muscle). 



Numerous instances of these facts appear in pathology. In 

 cholera, for instance, in which respiration ceases to be a func- 

 tion, properly so-called, and appears to be reduced by the 

 state of the blood to the entrance and exit of the air, the body 

 becomes perfectly cold. In febrile affections there is an in- 

 crease of caloric, which, we know, is followed by great 

 activity in the circulation and respiration, and in the com- 

 bustion which takes place in the tissues. 



The nervous system has plainly some influence upon the 

 production of animal heat, but this influence is very compli- 

 cated, and, in some respects, difficult to explain. The heat 

 produced by the organs (muscles, glands, and nervous 

 centres), being in direct proportion to the activity of their 

 functions (that is of the oxidation produced in them), it is 

 plain that the nerves, by means of which they perform their 

 functions, increase the heat by that very fact; thus Haller 

 observed, long since, that a paralyzed limb is usually colder 

 than when in health. Some physiologists have, unfortunately, 

 mistaken the nature of this.influence of the nervous system ; 

 thus Brodie and Chossat, having removed the encephalon 

 and cut the spinal cord of animals whose respiration they 



