ANIMAL HEAT 503 



from 395 c.c. to 256 c.c. ; 139 c.c. (say 140 c.c.) per kilo of body- 

 weight, or 350 c.c. per kilo of muscle, may therefore be taken as the 

 portion of the oxygen consumption of the skeletal muscles of a dog 

 at rest, which is under the control of the nervous system. Adding 

 150 c.c., the hourly oxygen consumption of a kilo of isolated muscles, 

 we get 500 c.c. per kilo per hour as the total consumption of skeletal 

 muscles connected with the nervous system, though not in active 

 contraction. * In a dog of 26 kilos body-weight (with, say, 10-5 kilos 

 of muscles) this would give 5,250 c.c. of oxygen as the consumption 

 of the resting muscles in an hour. The 15*5 kilos of the animal's 

 body left after deducting the muscles used up, therefore, in Zuntz's 

 experiment about 5,000 c.c. of oxygen, or 320 c.c. per kilo per hour. 

 If the work of the heart is taken as 27,000 kilogramme-metres in 

 twenty-four hours (p. 126), the total heat produced by this organ 

 will be equivalent (on the assumption that it converts one-third of 

 its energy into work) at least to 81,000 kilogramme-metres, or about 

 190,000 small calories, since, practically, the whole work is expended 

 in overcoming the friction of the vessels, and finally appears as heat. 

 Enough energy is transformed in twenty-four hours in the heart of 

 the colonel of a regiment of 1,000 men to lift the whole regiment 

 to a height of more than a metre, if it could be all changed into 

 mechanical work. The work of the inspiratory muscles may be 

 reckoned at 13,000 kilogramme- metres, equal to 30,500 small calories, 

 and the heat produced by them at, say, 90,000 small calories. In 

 sum, the muscular work of the circulation and respiration is respon- 

 sible for the production of at least 280,000 small calories (without 

 including the heat produced by the smooth muscle of the bronchi 

 and bloodvessels), or nearly one-eighth of the total production of a 

 man doing ordinary labour. During eight hours of sleep a man 

 produces altogether about 320,000 small calories. Of this the share 



280,000 

 due to the heart and respiratory muscles may be taken as 



93,300 ; or, since the work of the circulation and respiratory system 

 is less during the hours of rest, say, 90,000 small calories, i.e., between 

 one-third and one-fourth of the total heat-production during sleep. 



The glands, and then the central nervous system, rank 

 after the muscles, though at a great distance, as seats of 

 heat-production. The liver and brain (?) are the hottest 

 organs in the body ; and that this is not altogether due to 

 their being well protected against loss of heat is shown, in 

 the case of the liver, by the excess of temperature of the 

 blood of the hepatic over that of the portal vein. In view, 

 however, of the exaggerated importance which some have 

 given to these organs, as foci of heat-production, it may 

 be well to point out that although many of the chemical 



* Separation from the nervous system therefore cuts away more than two- 

 thirds of the muscular metabolism, and leaves less than one-third intact. 



