812 NUTRITION AND HEAT REGULATION. 



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-proteid 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-proteid 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 CO 2 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 temperature 

 nerves of the skin are affected by a fall in outside temperature, 

 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 mus- 

 cular tension no increase in the C0 2 excretion results. This fact 

 suffices 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 

 consumption of non-proteid material falls in, therefore, with the 

 conception 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, proteid 

 as well as non-proteid, 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 in- 

 creased production of urea as well as of C0 2 . 



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 proteid, 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 proteid 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. 



