Respiration and Metabolism 275 



The literature unfortunately abounds with respiratory quotient determina- 

 tions of doubtful value. Such determinations on animals subjected to partial 

 anaerobiosis are worth little unless carbon dioxide during and after anaero- 

 biosis is quantitated against post-anaerobic oxygen utilization. An "infinite" 

 R.Q. value reported by various investigators (e.g., Maloeuf-^0 is of little 

 significance except to enunciate the temporary oxygen deficiency or the sudden 

 release of large quantities of stored carljon dioxide. The fixation and release 

 of carbon dioxide from calcium carbonate deposits in or about the body have 

 supplied "false" R.Q. values in some of the earlier investigations."*'' The lobster, 

 Homanis, for example, gives a normal but "false" R.Q.. of 1.39 when the 

 specimens are untreated, but lower values of 1.00 when the specimens are 

 coated with paraffin, and 0.92 when they are covered with collodion. Sub- 

 normal respiratory quotients, as low as 0.4 in the marmot, for instance, are 

 probably to be attributed to the slow release of carbon dioxide from the tissues, 

 at low body temperature.-^ 



Another source of possible error in R.Q. values is pointed up by recent 

 work on carbon dioxide fixation and its synthesis into carbohydrate. ■''•^' ^^^ 

 Fasted rats and rabbits, when fed bicarbonate tagged with radioactive carbon, 

 form labelled glycogen in two to three hours after administration. It is obvious 

 that under these conditions the respiratory quotient may be changed, owing 

 to utihzation of this inorganic source of carbon and synthesizable carbonate. 

 An interesting use of radioactive carbon in the study of respiratory gases was 

 the recent demonstration of the previously suspected carbon monoxide-carbon 

 dioxide conversion, in which C^^O administered to turtles and mice appeared 

 in significant quantities as C^^Oj.^'* 



The respiratory quotient may vary with gas tension or be independent of 

 it. It is apparently independent in Chironomus, perhaps owing to a kind of 

 metabolic control as well as to the presence of blood pigment.^^^ The R.Q. of 

 Tuhifex is dependent on dxygen tension: 0.70 in 21 per cent oxygen and a 

 high and perhaps misleading 2.75 in 0.8 per cent oxygen. ^""^ Lwnhriciis com- 

 munis gives an R.Q. of 0.75 in 21 per cent oxygen, and 0.99 in 5 per cent 

 oxygen.-^'' The work of Rahn and Otis-"^ on human subjects carried to simu- 

 lated altitudes of 22,000 feet in a decompression chamber demonstrates a shift 

 in respiratory quotient toward a higher value (1.2), owing to hyperventilation 

 and the blowing off of carbon dioxide, which then decreases while remaining 

 "aloft." On descent, the respiratory quotient is low (0.55) but is shifted toward 

 normality (0.8) as the respiratory balance is regained. 



The conversion of food substances within the organism is attended bv varia- 

 tions in the respiratory quotient. Thus during the formation of fat from carbo- 

 hydrate sources a high respiratory quotient prevails as a result of the conserva- 

 tion of oxygen in the organic transformation. The fattening process in livestock 

 in which forced feeding with carbohydrate results in fat formation is accom- 

 panied by a high R.Q. This is shown by values as high as 1.49 in overfed 

 geese (Fig. 64).-^ Likewise, the utilization of fats and proteins and their 

 possible conversion to carbohydrate is characterized by low respiratory quo- 

 tients. Low R.Q. values are found in fasting and starved* animals, most of 

 which have an R.Q. near or a little below 0.7. 



Changes in the R. Q. occur with activity, inasmuch as carbohydrate stores 

 are first oxidized and with their depletion, as when available glycogen is used 

 up during long sustained moderate exercise, more and more fat and protein 



