204 SECTIONAL ADDRESSES 



20 per cent. In column 2 is given the number of subjects in each 

 category, and in columns 3 and 4 the number of cases in which 

 equation 16 or 17 respectively gave a result closer to the carbon dioxide 

 found experimentally. The meaning of the figures in the last two columns 

 in this table may be expressed as follows : Suppose 200 c.c. COg are 

 excreted per min., then since 90 per cent, of observations probably fall 

 within I • 61 1 times the standard deviation (Pearl), we may assume that for 

 the 127 subjects in the top line 90 per cent, of values calculated by 

 equation 16 would probably lie between 176-7 and 223-3 c.c, while the 

 corresponding limits for equation 17 would be 177-3 ^^^ 222-7 ^■^- ^^ 

 is clear from these figures that the variation between the two equations 

 is negligible, and so it may be argued that it is more physiological to use 

 equation 16, which involves only body weight and age, because, if height 

 is really important, the improvement with equation 17 should be more 

 marked. Although in this particular series of results from which both 

 equations were derived equation 17 gives for mathematical reasons slightly 

 closer results, it does not follow that this would be the case if these 

 equations were applied to another series of normal individuals. Hence 

 equation 16 which involves fewer measurements has been retained as the 

 chosen prediction equation. 



Effect of Sex and Age on Basal Metabolism. — From 5 or 6 years onwards 

 girls have a lower basal metabolism for their weight than have boys. 

 The differentiation of the sexes as regards their metabolism, which begins 

 after the erect posture is attained and exercise is being freely taken, is of 

 great interest, as it appears long before any secondary sexual characters. 

 It is possibly due to the fact that from about 5 to 6 years onwards girls 

 on the whole take less exercise than boys and consequently their muscles 

 are less developed and so the basal metabolism which must largely depend 

 on muscular development is lower. Athletes have a higher metabolism 

 than ordinary men. In babyhood there is no noticeable difference in 

 activity between the sexes and their basal metabolisms are the same. 

 From puberty onwards the difference in activity is marked and the 

 difference between the metabolisms is at a maximum. We have suggested 

 that the falling off of metabolism with age is also due to lessening 

 muscular activity with consequent muscular atrophy ; this takes place 

 more rapidly in men than women, and this would agree with the more 

 rapid drop of the metabolism in men. It would be of particular interest 

 to compare the metabolisms of very old men and women ; on this 

 hypothesis they should be the same, since muscular activity in both would 

 be at a minimum. 



Practical Indirect Calorimetry. 



I use the ' open ' method of Krogh and Lindhard for determining the 

 carbon dioxide in clinical work. Fresh outside air is supplied to the 

 subject by a mask and valves ; from the subject the expired air passes to 

 the bottom of a wide-mouthed bottle of about 2 litres capacity, which in 



