39 PHYSIOLOGICAL CHEMISTRY. 



with varnish without harmful result if precautions are taken 

 to prevent loss of heat. 



TIME AND PLACE OF OXIDATION. 



The determination of the respiratory quotient through short 

 intervals shows considerable variations, as pointed out some 

 pages back. The human organism has not the power of stor- 

 ing up oxygen in the free or combined form through a long 

 period, as appears to be the case with some cold-blooded ani- 

 mals, which are able to exist for a time in an atmosphere free 

 from oxygen. With man and warm-blooded animals in gen- 

 eral this is not possible; with these life without oxygen may 

 be maintained for but a few minutes at most. An exception 

 exists in the case of those animals which pass the winter in a 

 dormant condition (hibernating animals) and for human 

 beings in trance. Here the absorption of oxygen and excre- 

 tion of carbon dioxide are reduced to a minimum. But ordi- 

 narily man and the higher animals require some inflow of 

 oxygen all the time. 



The extent to which this oxygen is used depends on the 

 activity of the muscles largely. In rest periods the amount 

 of oxygen taken up by the muscles is much greater than is the 

 carbon dioxide given off, but with the contracting or working 

 muscle the reverse is the case. In experiments in which the 

 changes in the blood supply of individual muscles may be fol- 

 lowed it may be shown that for rest periods the respiratory 

 quotient for the muscle may fall far below 0.7 or even below 

 0.5. From the rapidly contracting muscle, on the other hand, 

 the evolution of carbon dioxide is relatively great. A respira- 

 tory quotient, for the muscle, of 1.5 or even 2 or more may be 

 found. This indicates that during rest oxygen may be taken 

 up from the blood and held or condensed in some manner by 

 substances within the muscular tissue, but of the mechanism 

 of this reaction unfortunately but little is known. In doing 

 work tissue is rapidly oxidized at the expense of the stored-up 

 oxygen, and a great excess of carbon dioxide is given off 



