THE RESPIRATORY EXCHANGE 495 



and a greater supply of food. An examination of the table for 

 the respiratory exchange of different mammals and birds will 

 show that a mouse, which weighs 25 grm. and has a temperature 

 of 37, discharges 8'4 grm. of carbon dioxide, and an ox, which 

 weighs 660,000 grm. and has a temperature of 38, discharges 

 0-5 grm. of carbon dioxide per kilo of body-weight and hour ; 

 a comparison between a sparrow, which weighs 22 grm., and main- 

 tains an internal temperature of 42, and a hen, which weighs 

 1280 grm. and has a similar high temperature, shows that the respec- 

 tive figures for the output of carbon dioxide are 10' 5 and 1-3 grm. 

 For an infant and a child, for a child and an adult, a similar 

 comparison could be made. Indeed Sonden and Tigerstedt's ( n ) 

 researches upon the respiratory exchange and total metabolism 

 of man show that over and above the greater respiratory exchange 

 due to the relation between surface and mass, there is a greater 

 combustion due to the age of the child ; the younger the child 

 the greater is this excess. It is interesting to note also that these 

 observers find that the output of carbon dioxide, whether it be 

 calculated for weight of body or for cutaneous surface, is much 

 greater in the male than in the female child even when individuals 

 of similar age and weight are compared. The average results 

 show that the ratio is as 140 to 100. This sexual difference in 

 metabolism gradually diminishes and disappears with the ap- 

 proach of old age ; it is probably due to the greater mus- 

 cular tone and restlessness of the boy, for it is not shown in 

 the results obtained by Magnus-Levy and Falk upon children 

 fasting and lying down. The following table (see p. 496) gives 

 the average results obtained by Sonden and Tigerstedt ; the 

 observations were made upon individuals sitting down and a 

 short time after a meal, two conditions which would explain the 

 increase in the respiratory exchange above that observed by 

 Magnus-Levy. 



This question is one of great practical importance, for it shows 

 that the dietary for children must not be calculated on the basis 

 of their weight ; they require relatively a much more liberal diet 

 than adults. Apart from the influence of the large cutaneous 

 surface upon the combustion of food substances in children, it 

 is obvious that active growth cannot occur unless there be a 

 surplus of intake over output. Serious mistakes have been made 

 owing to neglect or ignorance of these facts. Haldane pointed 



