584 A MANUAL OF PHYSIOLOGY 



crural nerves were divided and intact. In both cases the muscles 

 were at rest in the ordinary sense. But in the second experiment 

 the central * tonus ' (p. 813) was preserved, while in the first it was 

 abolished. In one experiment in which the nerves were intact the 

 oxygen consumed amounted to i'22 c.c., and the carbon dioxide 

 produced to 1*32 c.c., per kilo of tissue per minute. In the experi- 

 ment in which the nerves were severed, the corresponding numbers 

 were o - 68 c.c. for the oxygen and 0*63 c.c. for the carbon dioxide. 

 Although it is probable, from the results of Chauveau and Kauff mann 

 already referred to (p. 263), that these figures are too low for the 

 normal resting muscle, they still demonstrate that, even in the 



FIG. 198. DIAGRAM SHOWING THE HEAT-EQUIVALENT OF VARIOUS DIETARIES 

 A, proteins ; B, fats ; C, carbo-hydrates ; D, heat-equivalent. 



absence of innervation from the central nervous system, the meta- 

 bolism, and therefore the heat-production of the muscles, are by no 

 means negligible ; o - 68 c.c. of oxygen per minute corresponds to 

 40'8 c.c. per hour, or more than one-tenth of the oxygen consumption 

 per kilo per hour of a fasting dog lying at rest (Zuntz) . 



If the work of the heart is taken as 16,600 kilogramme-metres in 

 twenty-four hours (p. 127), the total heat produced by this organ 

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

 its energy into work) to about 50,000 kilogramme-metres, or not 

 much less than 120 calories, since, practically, the whole work is 

 expended in overcoming the friction of the vessels, and finally 



