CHAPTER V. 



THE INFLUENCE OF INTERNAL FACTORS UPON THE STANDARD 



METABOLISM. 



THE fundamental problem which ought to be dealt with in the present 

 chapter is this : Supposing all external factors to remain constant and 

 the supply of oxidative material and oxygen to be sufficient, is the 

 oxidative energy of the 'resting cells a constant quantity or can the 

 oxidations be increased without any functional activity taking place ? 

 This fundamental problem which involves the determination of basal 

 metabolism cannot at present be solved, and we must confine ourselves 

 to the results obtained by the study of the standard metabolism. 



The Influence of the Central Nervous System. 



There is at present no proof that an increase in metabolism can be 

 induced from the nervous system without a corresponding increase in 

 functional activity, but in certain cases the possibility cannot be ex- 

 cluded and further experimentation is therefore highly desirable. 



Rubner [1887] found that when warm-blooded animals (especially 

 dogs) were exposed to low temperatures there was a considerable in- 

 crease in metabolism. In many cases muscular movements could 

 not be observed, the animals lying absolutely quiet. He introduced 

 the term " chemical heat regulation " for this process, and was of opinion 

 that the metabolic processes in muscles remaining at rest could be 

 increased through nervous stimulation. It has not been proved, how- 

 ever, that the muscles really remained at rest. Slight shivering move- 

 ments may easily have escaped attention, and there may have been an 

 increased muscular tone apart from actual movements. The graphic 

 records obtained by Benedict and Homans [1911] on a dog show 

 shivering movements at all temperatures below 25 and increasing 

 regularly in intensity with decreasing temperature. 



It remains to be demonstrated, however, that there is a quantitative 

 correspondence between the muscular movements recorded during 

 " chemical heat regulation " and the measured increase in metabolism. 



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