78 



SCIENCE 



[N. S. Vol. XLII. No. 1072 



quietly withoiit breakfast, but not asleep. 

 If the subject is sitting up, the metabolism 

 is increased, and if he is doing work it is 

 increased in proportion to the amount of 

 work. The approximate normal output of 

 carbon dioxide and heat for a man of aver- 

 age weight with varying conditions of 

 muscular activity is shown in Table I. By 

 means of this table one may calculate the 

 approximate carbon dioxide and heat out- 

 put of a man during twenty-four hours. 

 (See Table II.) 



TABLE I 



Average Normal Output of Carbon Dioxide and 

 Seat from the Body 



Average Quantities 



Per Hour 

 Carbon 



Dioxide, Heat 



Conditions of Muscular Activity Gm. Cals. 



Man at rest, sleeping 25 65 



Man at rest, awake, sitting up... 35 100 

 Man at light muscular exercise. . . 55 170 

 Man at moderately active muscu- 

 lar exercise 100 290 



Man at severe muscular exercise. 150 450 

 Man at very severe muscular exer- 

 cise 210 600 



TABLE II 



Average Daily Output of Heat of a Man at Light 

 Muscular WorTc 



Heat 

 Out- 

 Daily Program put 

 At rest, sleeping, 8 hours, 65 calories per 



hour 520 



At rest, awake, sitting up, 6 hours, 100 cal. 



per hour 600 



Light muscular exercise, 10 hours, 170 cal. 



per hour 1,700 



Total output of heat, 24 hours 2,820 



It is of no avail to make investigations in 

 pathology unless we have a suitable base 

 line or ground for comparison, and in prac- 

 tically all our clinical studies we have had 

 to supply the deficiency in normal data. 

 While the temptation is at times very great 

 to carry out a series of experiments which 

 will most certainly promise striking re- 



sults, we have felt constrained to plod 

 along and secure fundamental basal values, 

 and thus contribute steadily to the knowl- 

 edge of the physiology of man. To do this, 

 and to secure information as to the influ- 

 ence of variations in height, age, weight and 

 sex of normal individuals, we have studied 

 90 or more normal men, and nearly as many 

 normal women, and have secured approxi- 

 mate basal values for these individuals. 

 Studies have like^vise been made of athletes 

 and vegetarians. For the most part these 

 observations were made with the small 

 respiration apparatus and not with the 

 calorimeters; indeed, at times as many as 

 four respiration apparatus have been used 

 simultaneously in our large calorimeter 

 room, in studying the metabolism of four 

 individuals. 



Two factors that affect normal metabolism 

 more than any others are the ingestion of 

 food and muscular activity. In Table I., 

 the somewhat vague terms of "Light," 

 "moderately active," "severe" and "very 

 severe" muscular work were used. These 

 really have no quantitative meaning, and 

 it is necessary for us to measure accurately 

 the amount of mechanical work performed 

 when studying the metabolism of a person 

 doing severe muscular work. For this pur- 

 pose several forms of bicycle ergometer 

 have been used by means of which the rider 

 transforms a certain amount of muscular 

 work into heat. The ergometer may be 

 placed inside a respiration calorimeter, or 

 the subject may be connected with a suita- 

 ble mouthpiece to a simple respiration ap- 

 paratus. The series of studies on this 

 apparatus have proved most illuminating, 

 and show that the human body is really a 

 very efficient engine. While in certain 

 cases as much as 35 per cent, of the total 

 energy transformed during muscular work 

 may be transferred to the pedals of the 

 ergometer, there to be transformed into 



