CARBONACEOUS WASTE-PRODUCTS 539 



energy is derived, in the first place, from the oxidation of carbo- 

 hydrates. 



On the other hand, in Starvation, the respiratory quotient falls to a 

 value intermediate between that characteristic for the oxidation of 

 fats and the value for proteins, for in starvation the carbohydrate 

 reserves are quickly depleted, and thereafter the energy which is dis- 

 sipated by the body is derived from the oxidation of the fat reserves 

 and the tissue proteins. 



Extraordinarily low values of the respiratory quotient have occa- 

 sionally been obtained with Hibernating Animals during their winter- 

 sleep. Thus Pembrey obtained figures as low as 0.25 with hibernat- 

 ing dormice. For hibernating bats Hari obtained higher figures, but 

 even these values were generally less than the normal value for the 

 oxidation of pure fats. The origin of these low values has been the 

 subject of numerous surmises. It appears to be incontestable that 

 they represent incomplete oxidations, which do not proceed so far as 

 to result in the formation of carbon dioxide. A question much more 

 difficult to decide, however, is whether the excess of oxygen intake 

 over carbon-dioxide output in the winter-sleep is stored in the animal's 

 tissues, or excreted in the form of compounds other than carbon 

 dioxide. It was at first supposed that the oxygen excess was stored in 

 the tissues in the form of partially oxidized foodstuffs, as, for example, 

 carbohydrates derived from fats. It has been pointed out, however, 

 that the total accumulation of oxygen throughout the duration of the 

 winter-sleep would necessitate the production of a quantity of carbo- 

 hydrate far in excess of the total carbohydrate-content of the animals 

 under any conditions. It has been ascertained that the urine of 

 hibernating animals contains notable quantities of products of incom- 

 plete oxidation such as Lactic Acid, and it is probable that a con- 

 siderable proportion of the excess of absorbed oxygen is excreted in 

 the urine in these forms. 



Not only does the ratio of carbon-dioxide evolved, to oxygen ab- 

 sorbed, rise during the performance of muscular exercise, but the 

 total carbon-dioxide output increases in direct proportion to the work 

 performed. This has been shown in a very striking manner by the 

 experiments of Johansson who first measured his carbon-dioxide out- 

 put per hour at rest and then during the performance of the Muscular 

 Work involved in repeatedly lifting a weight. He found that his carbon- 

 dioxide output rose to the value 



CO 2 = Np + q 



where " q" was the output at rest, "N" the number of times the weight 

 was lifted and "p" the increase in output induced by lifting the weight 

 once. 



The effect of the Temperature of the environment upon the carbon 

 dioxide output is opposite in cold-blooded and warm-blooded animals. 



