370 RESPIRATORY METABOLISM 



(1928) reported an R.Q. of 0.69 for Paramecium, and Root (1930) 

 in a number of experiments obtained an R.Q. value of 0.62. Root also 

 found that the R.Q. varied somewhat irregularly with changes in COg 

 tension. However, there was a definite trend toward high R.Q. values 

 in media of high COg tension, and the average R.Q. at 238-423 mm. 

 Hg. was 1.43. This apparently was caused by a decrease in O^ consump- 

 tion (see above) without a corresponding decrease in CO2 production, 

 thereby giving a high R.Q. According to Root, "It is possible that the 

 suppression of oxidations under these conditions results in the produc- 

 tion of acid metabolites which drive out carbon dioxide from the bi- 

 carbonate contained in the cells and in the surrounding medium." Similar 

 experiments on Arbacia eggs did not show an increase in R.Q., and it 

 was assumed either that acid substances were not produced or that they 

 were rapidly converted into a non-acid form and did not accumulate 

 in appreciable amounts. Apparently CO, tension is a factor which should 

 be considered when making measurements of R.Q. However, if ex- 

 periments are conducted with standard manometric techniques, this factor 

 is probably not important. 



Specht (1935) measured the R.Q. of Spirostomum in manometers, 

 both with and without the presence of acid in a side arm of the manom- 

 eter flask. He found an R.Q. of 0.24 without the acid and 0.84 when 

 acid was present. This discrepancy was explained as being caused by 

 the elimination of NH3 by the organisms, and the value of 0.84 is 

 therefore accepted as more nearly correct. However, it was also demon- 

 strated that the R.Q. was 0.98 in an atmosphere of O,, and that this 

 value was not affected by the presence or absence of acid. Apparently 

 NH3 is not produced at high O^ tension. These experiments indicate 

 very clearly that ammonia secretion is a possible source of error in 

 measurements of protozoan respiratory quotients, and therefore one 

 should be suspicious of the validity of low R.Q. values unless adequate 

 precautions have been taken against the ammonia error. 



For the free-living flagellates, very low values of R.Q. have been 

 reported. Jay (1938) found R.Q. values of 0.34 and 0.56 for Astasia 

 and Khatvkinea, respectively. Mast, Pace, and Mast (1936) reported 

 R.Q. values of 0.28 to 0.37 for Chilomonas , and 0.72 for Paramecium 

 fjjulti)7iicronucleatum under similar conditions. The possible explana- 

 tions mentioned by Jay for the low R.Q. value are conversion of pro- 



