METABOLISM IN RESPIRATION AND CIRCULATION 543 



sources of body heat. In the Pikes Peak expedition, the metabolism at 

 rest was only slightly above that found at sea level for the subjects under 

 investigation. The respiratory quotient showed no change indicative of 

 abnormal combustion. Bittorf reviewed the studies at high altitudes, and 

 considered the increase generally found in the metabolism so large as to 

 be caused by more than the muscular compensations and suggested phys- 

 ical influences such as cold and violet rays. 



On the other hand, if the compensation cannot adequately meet the 

 demand of the body for oxygen a considerable number of changes in the 

 metabolism are theoretically possible. Practically very little work has 

 been done where such a condition was present. Here again one would 

 expect that the muscular compensatory efforts would raise the metabolism 

 above the basal, but it has often been questioned, especially in treatises 

 upon oxygen disturbances in anemia, as to whether the basal requirements 

 are not actually lowered when the tissues continuously receive less than 

 their normal supply of oxygen. The two influences may easily mask each 

 other and leave a practically normal metabolism. Many writers suggest 

 that oxygen-lack causes simply an incomplete combustion within the cells, 

 rather than a lowering of the basal requirements. 



The discussions in regard to incomplete combustion are founded upon 

 few facts, but the possibilities are extensive and must be considered 

 with regard to protein, carbohydrate, and fat. Either non-combustion 

 or a breaking down into abnormal end-products may result. Bache and 

 Auel, working on dogs under low oxygen pressure, repeated the findings 

 reported by Araki(c) of non-combustion of carbohydrates, and consequent 

 appearance of sugar in the urine under conditions of asphyxia. Various 

 investigators (Boycott and Haldane, Ryffel(a) (&), Barcroft), on the other 

 hand, have reported incomplete combustion of carbohydrate, as prob- 

 ably shown by the presence of a low alveolar carbon dioxid content, or of 

 lactic acid in the blood or urine. From the lowered alveolar carbon di- 

 oxid, the report from the Pikes Peak expedition assumed this, together 

 with the presence of other abnormal acid metabolites. The many treatises 

 upon the conditions due to the lack of oxygen during strenuous bodily 

 exercise show the presence of lactic acid. 



The amount of protein burned has also been reported as decreased when 

 there is oxygen-lack. Voit(fr), however, states that most work upon the 

 subject, as well as his own, shows an increase in the nitrogen output. Min- 

 kowski(fc) reports the same. Lusk(e) states that after respiration of rari- 

 fied air when lactic acid is eliminated in the urine, there is an associated 

 increase in protein metabolism with an increase in the ammonia and amino 

 acid output. Disturbances in the intermediary protein metabolism have 

 been investigated only in the urinary products. Weiss considers the 

 neutral sulphur as a measure of amino acid output. The chances for 



