RESPIRATORY METABOLISM 371 



tein to carbohydrate, or incomplete oxidation of carbohydrate. The ex- 

 planation of Mast et al. is that carbohydrate was being synthesized from 

 carbon dioxide. This explanation is based on previous nutritional studies, 

 but these are open to question (review. Hall, 1939). One obvious possi- 

 bility is that COo may be retained in the immersion fluid, but Mast 

 and his coworkers obtained only a slightly higher R.Q. value when the 

 bound COo was liberated by acid (single experiment only). In these 

 cases the explanations offered must be considered as only tentative, until 

 the possibilities of NH3 production and COo retention are positively 

 eliminated. Mast and his coworkers also reported for Chilomonas that 

 under certain conditions starch was converted to fat, and that fat oxida- 

 tion could be decreased by depriving the organism of sulphur. However, 

 values obtained for the R.Q. were variable and showed no definite cor- 

 relation with these conditions. 



Values of the R.Q. reported for members of the family Trypano- 

 somidae are within the normal range. Soule (1925) obtained an R.Q. 

 of 0.84-0.91 for Leishmania tropica and 0.74-0.89 for Trypanosama 

 lewisi in blood agar medium. When glucose was present, the R.Q. rose 

 to 0.95 for L. tropica and 0.94 for T. letvisi. Novy (1932) reported res- 

 piratory quotients of 0.93 to 1.0 for T. lewisi, L. tropica, L. donovani, L. 

 infantum, Strigonionas oncopelti, S. culicidarum, S. culicidarum var. 

 anophelis, S. lygaeorium, S. media, S. muscidarum, and S. parva, when 

 grown on glucose-blood agar. When grown on glycerol-blood agar or 

 plain blood agar, the R.Q. was about 0.8 to 0.87 for the four species of 

 Leishmania. Von Fenyvessy and Reiner (1924) found an R.Q. of 0.60 

 for Trypanosoma equiperdum in diluted blood. A. Lwoff (1933) ob- 

 tained R.Q. values of 1.0 for Strigomonas oncopelti and S. jasciculata, 

 and a value of 0.88 for Leptomonas ctenocephali. 



Apparently the only R.Q. measurement on a rhizopod is that of 

 Emerson (1929) on Amoeba proteus, which gave a value slightly less 

 than 1.0. 



Another method, in addition to that of the respiratory quotient, which 

 might be used as an index of the source of energy in an organism is 

 the calorific quotient. Since the ratio of heat produced to oxygen con- 

 sumed differs with carbohydrate, fat, and protein (3.5, 3.3, and 3.2, 

 respectively), it is possible to measure heat production and Oo con- 

 sumption and to use this ratio as an index of the substrate being utilized. 



