614 JOHN K. MURLIN 



heightened metabolism of the infant one year old when reckoned on the 

 basis of a unit of surface (Murlin and Hoobler). That the rate of growth 

 itself, however, may be partly responsible, is evidenced by the fact that boys 

 at the age of prepubescence, just when growth is accelerated, experience also 

 a quickening of heat production. DuBois's results indicate that this may 

 amount to as much as 25 per cent over the normal level for adults. Whether 

 the awakened activity of the internal secretory mechanism of the sex glands 

 acts independently or only through its effect upon growth, can only be 

 decided by experiments upon animals. The latest experiments of this kind 

 by Murlin and Bailey support the view of Loewy and Richter that in 

 the female at least there is an independent effect quite outside the effect 

 upon muscular rest. The tendency to obesity following the menopause 

 in women is to be explained, therefore, as due to the absence of a stimulus 

 which was present so long as the ovary was active. Removal of the ovary 

 has the same effect. The falling metabolism of old age is to be explained 

 in part by the tendency to reduce muscular effort of all sorts to a minimum, 

 this, in turn, being traceable probably to the absence of internal stimuli, 

 whether reflex or chemical. The deposit of calcareous material in certain 

 organs, which so frequently, accompanies old age, may also of itself reduce 

 their metabolic activity. 



Statistically studied, the decrease in total heat production per 24 

 hours for each year of age is, according to Harris and Benedict, 7.15 Cal. 

 for their series of 136 adult men. For the 103 women it is 2.29 calories 

 for each year of adult life. Upon the basis of a unit of body surface, the 

 correlations with age "are of a more strongly negative character than 

 the correlations between age and total heat production," which means 

 that with each advancing year of life there is a heavier decline upon 

 ihe basis of a square meter of body surface than upon the basis of 

 total heat production. This conclusion is in accordance with DuBois's 

 curve, though it does not give exactly the same rate of change. 



3. The Influence of Sex. Impressive also is the difference between 

 the two sexes. DuBois had already drawn attention to this difference in 

 the first curve which he published showing the variation with age. His 

 curves for the two sexes ran about the same distance apart (7 per cent) as 

 do the newer ones here reproduced. Twenty years ago Magnus-Levy and 

 Falk found the difference between the two sexes both in early life and in 

 advanced age about five per cent, but were of the opinion that in adult life 

 the two sexes maintain about the same metabolism, consideration being had 

 to difference in size and age. Harris and Benedict have analyzed the results 

 of metabolism studies on the two sexes very exhaustively, .making correction 

 for body weight, body surface, age, and stature, and find that on every basis 

 the metabolism for the women is lower than that of men. Even when the 

 theoretical heat production of the woman is calculated by inserting their ac- 

 tual physical measurements in equations based on the series of men (regard- 



