EFFECT OF MUSCULAR WORK AND TEMPERATURE. 843 



do not affect the body temperature. An account of the means by 

 which this regulation is effected will be found in the chapter upon 

 Animal Heat. So long as the temperature of the body remains con- 

 stant, it has been found that a fall of outside temperature may 

 increase the oxidation of non-protein material in the body, the in- 

 crease being in a general way proportional to the fall in tempera- 

 ture. That the increased oxidation affects the non-protein con- 

 stituents is shown by the fact that the urea remains unchanged in 

 quantity, other conditions being the same, while the oxygen con- 

 sumption and the carbon dioxid elimination are increased. This 

 effect of temperature upon the body metabolism is due mainly to a 

 reflex stimulation of the motor nerves to the muscles. The tem- 

 perature nerves of the skin are affected by a fall in outside tempera- 

 ture, and bring about reflexly an increased innervation of the 

 muscles of the body. Indeed, it is stated * that unless the lowering 

 of the temperature is sufficient to cause shivering or muscular 

 tension no increase in the excretion of CO 2 results. This fact suf- 

 fices to explain, therefore, the physiological value of shivering and 

 muscular restlessness when the outside temperature is low. The 

 fact that variations in outside temperature affect only the con- 

 sumption of non-protein material falls in, therefore, with the concep- 

 tion of the nature of the metabolism of muscle in activity, given 

 above. When the means of regulating the body temperature 

 break down from too long an exposure to excessively low or ex- 

 cessively high temperatures, the total body metabolism, protein 

 as well as non-protein, increases with a rise in body temperature 

 and decreases with a fall in temperature. In fevers arising from 

 pathological causes it has been shown that there is an increased 

 excretion of nitrogen as well as of carbon dioxid. 



Effect of Starvation. A starving animal must live upon the 

 material present in its body. This material consists of the fat 

 stored up, the circulating and tissue protein, and the glycogen. 

 The latter, which is present in comparatively small quantities, is 

 quickly used, disappearing more or less rapidly according to the 

 extent of muscular movements made. Thereafter the animal lives 

 on its own protein and fat, and if the starvation is continued to a 

 fatal termination the body becomes correspondingly emaciated. 

 Examination of the several tissues in animals starved to death has 

 brought out some interesting facts. Voit took two cats of nearly 

 equal weight, fed them equally for ten days, and then killed one to 

 serve as a standard for comparison and starved the other for thirteen 

 days; the latter animal lost 1017 gms. in weight, and the loss was 

 divided as follows among the different organs: 



* Johannson, " Skandinavisches Archiv f. Physiologic," 7, 123, 1897. 



