608 JOHN R. MURLIN 



to the absence of reflexes, with possibly a factor due to the suppression of 

 neural activity in the brain, spinal cord and peripheral nerves. In time 

 it may become necessary to revise the standard conditions for basal metabo- 

 lism and to include, in addition to complete muscular rest and complete 

 alimentary quiescence, neural rest. For the present sufficient data do not 

 exist to warrant the change in standard ; hence, the basal metabolism as 

 ordinarily defined will be used in this chapter to determine the influence of 

 age, sex, physical characteristics, etc., in the normal individual. 



Even under the most uniform conditions thus far applied the basal 

 metabolism has been found to vary from day to day and from hour to 

 hour in the same individual, and even more in different individuals. For 

 example, Johansson found on himself an average CO 2 production per 

 hour of 22.2 grams with an average deviation from the mean of 3.6 per 

 cent. Nevertheless, he found this metabolism to remain constant within 

 the variation given over a period of seven months. Magnus-Levy (&) ob- 

 served a similar degree of constancy over a period of two years. In a series 

 of 51 observations made during comple'te muscular rest upon an athlete 

 Benedict and Cathcart found a standard deviation from the mean of 4.9 

 per cent When different individuals are considered the variation is 

 much greater. The simple average percentage deviation from the mean 

 in 35 different subjects observed by Benedict was 13.9 per cent. 



1. The Influence of Physical Characteristics. From an exhaustive 

 biometric study of basal metabolism in the normal human adult including 

 137 men and 103 women, Harris and Benedict find that the most intimate, 

 correlations are obtained when correction for body size is made by express- 

 ing heat production in calories per square meter of body surface. 7 



As regards the effect of body weight upon the energy metabolism Har- 

 ris and Benedict find that an increase of 1 kgm. of weight in the adult man 

 increases the consumption of oxygen on the average 2.27 c.c. per minute 

 and the carbon dioxid 1.87 c.c. per minute; for women the values are 1.17 

 c.c. oxygen, and 1.02 c.c. carbon dioxid. A kilogram of body weight added 

 to the adult increases the total heat production for twenty-four hours on 

 the average 15.8 Cal. for men and 8.27 Cal. for women. There is also 

 a distinct and independent correlation between stature and- energy metab- 

 olism, but this is not so close as with body weight. For each 1 cm. in- 

 crease in stature the heat production increases about 16.6 Cal. per day in 

 man and 6.9 Cal. per day in women. The same authors find that there 

 is no very high degree of correlation between heat production and heart 

 activity as measured by pulse rate, unless correction is made for body 

 weight or body surface. 



7 This admission the authors are obliged to make although they do not believe 

 that the closer agreement between heat production by different individuals and their 

 surfaces than between heat production and body weight is due to any causal relation- 

 ship ( see page 597 ) . 



