68 EXPERIMENT STATION RECORD. 



the use of beef pancreas instead of castor bean for the cleavage of fat. The 

 method which ho recommends for the estimation of fatty acids is outlined. 



The influence of muscular and mental work on metabolism and the effi- 

 ciency of the human body as a machine, F. C. Benedict and T. M. Carpenter 

 ([/. 8. Dcpt. Agr., Office Expt. hitas. Bui. 208, pp. 100, figs. .3).— The first of the 

 two papers reports data of 19 experiments on the effects of muscular work on 

 metabolism and the efficiency of the human body as a machine, and the second 

 44 experiments on the effects of mental work on metabolism. lu all of these 

 experiments the respiration calorimeter was used. The bicycle ergometer was 

 used in the work experiments and is described. 



From the data reported in connection Avith the experiments on muscular work 

 the authors compute that as regards the effectiveness of the body as a machine 

 it shows an efficiency of 20 per cent; that is, for every calorie of muscular 

 work produced by the body a total of 5 calories is expended. 



In the experiments on the influence of mental work on metabolism the stu- 

 dents who served as subjects each took a more or less ditficult examination in 

 some college study while in the respiration chamber, comparison being made 

 with a similar period in which the same subjects engaged in reading or copying 

 some material which would demand little mental effort. 



"From the results of the data accumulated in this series of experiments on 

 Ihe effects of mental work on metabolism it would appear that the pulse rate 

 was slightly increased, the body temperature somewhat higher, the water vapor 

 output increased by about 5 per cent, the carbon dioxid production increased by 

 about 2 per cent, the oxygen consumption increased by about 6 per cent, and 

 the heat production increased by about one-half of 1 per cent as a result of 

 sustained mental effort such as obtains during a college examination. Of these 

 factors, those most accurately measured are undoubtedly the carbon dioxid 

 elimination and the heat production. On the whole, however, the increase of 

 both of these factors accompanying the mental exertion is so small and the 

 exceptions are so numerous that it would not be wise to say whether or not the 

 mental activity exercised a positive influence on metabolic processes in general. 

 Indeed, more than half of the subjects studied produced more heat in the con- 

 trol than in the mental work test, which might be considered as negative 

 evidence. This is especially so when it is considered that although every pre- 

 caution was taken to eliminate all other extraneous influences it still remains 

 a fact that, with many of these subjects, the . . . [experimental period with 

 mental work] was their first experience inside of a complicated respiration 

 chamber aud they were more or less disturbed by the novel experience, and 

 perhaps more restless — that is, made more muscular movements than during 

 the control period. In view of this fact, we are very strongly of the opinion 

 that the results obtained in these experiments do not indicate that mental eft'ort 

 has a positive infiuence on metabolic activity." 



The influence of oxygen inhalations on athletes, L. E. Hill {Brit. Med. 

 Jour., 1908, No. 2^86, pp. ^99, 500). — Respiratory quotient experiments are sum- 

 marized with both ordinary breathing and forced breathing of oxygen. In both 

 cases, pai'ticularly the latter, the oxygen was a benefit in athletic contests. 



" It has been proved conclusively that excess of oxygen docs not increase the 

 rate of metabolism of living matter. It is not a question hero of fanning up 

 the fire of life, but of assuring the athlete an adequate respiratory exchange in 

 his muscle during his supreme efforts." 



Oxygen as a substitute for training {Illus. London News [Amer. Ed.], 4i 

 (1909), No. 1138, pp. 289, 290, fig. 1).—A very brief description of the use of 

 oxygen by athletes in experiments by L. E. Hill (see above), with an illustration 

 showing the way in which the oxygen is taken. . 



