INTRODUCTION. 15 



Two years later the classic monograph of Rubner and Heubner 1 

 appeared. In discussing the earlier observations of Forster, they add 

 the significant fact that Forster's experimental periods were but one 

 hour long. As their own work was done with the Pettenkofer chamber, 

 they criticize adversely the closed-circuit apparatus used by Scherer 

 and particularly the fundamental principle of using experiments with 

 short periods, their paper setting forth fully the arguments in favor of 

 the long experimental period and the Pettenkofer type of respiration 

 chamber as compared with the short period and the Regnault-Reiset 

 chamber. The Pettenkofer chamber, which had previously been de- 

 scribed, 2 was slightly modified for the studies of Rubner and Heubner, 

 a small chamber being used. 



The fundamental question studied by Rubner and Heubner was the 

 nourishment of an infant from a practical standpoint; and they were 

 accordingly more interested in the average daily requirement of an 

 infant for nourishment than in the physiological fact of the minimum 

 requirement for comparison with other individuals. The subject — a 

 "normal" infant — was 9 weeks old at the time of the observation and 

 weighed 5,220 grams. The infant was placed in the respiration chamber 

 and removed and fed from 6 to 8 times each day, the time thus lost 

 being carefully recorded. Ocular observations of the muscular activity 

 were made and a general impression for each day recorded. Much of the 

 time, the infant was awake but not crying. On the basis of 24 hours the 

 authors found a difference of 22 per cent between minimum and maxi- 

 mum carbon-dioxide production. They state that this difference is 

 due to the unequal activity of the infant, emphasizing especially the 

 fact that disturbance of sleep during the night influences the total daily 

 average of the metabolism. 



Using Meeh's formula 3 (S = 11.9^/W) and a body-weight of 5.1 kg. 

 they compute the body-surface to be equal to 3,500 sq. cm. and find a 

 carbon-dioxide production of 13.5 grams per square meter of body- 

 surface per hour. Comparing this value with those found with adults, 

 they state that the infant excreted less carbon dioxide per square meter 

 of body-surface than did the adults and explain this by the fact that 

 the infant was asleep a part .of the time while the determinations with 

 adults were made only when the subjects were awake. Having pointed 

 out that their results contradict those of Sonden and Tigerstedt, 4 which 

 showed an increased production of carbon dioxide in youth, they em- 

 phasize the fact that the carbon dioxide is essentially proportional to the 

 body-surface with human individuals of any size. 



Shortly after the publication of their investigations with a normal, 

 breast-fed infant, Rubner and Heubner 5 reported a comparative study 



Rubner and Heubner, Zeitschr. f. Biol., 1898, 36, p. 1. 



2 Wolpert, Archiv f. Hyg., 1896, 26, p. 32. 



3 Meeh, Zeitschr. f. Biol., 1879, 15, p. 425. 



'Sonden and Tigerstedt, Skand. Archiv f. Physiol., 1895, 6, p. 1. 



'Rubner and Heubner, Zeitschr. f. Biol., 1899, 38, p. 315. 



