IMPORTANCE OF SURFACE DEVELOPMENT 521 



important degree. " 17 To determine the maintenance ex- 

 change (minimal metabolism) 18 it is obvious that complete 

 body rest and a state of fasting are essential. Eeference 

 has been made repeatedly to the fact that any sort of mus- 

 cular activity increases exchange in a marked degree. 

 Johannson recognizes three types of "rest": complete en- 

 forced rest, rest in bed, and rest in the room, in the last of 

 which there may be permitted alternation of quiet sitting, 

 reading, writing and other light occupations. It is very 

 instructive to note that the exchange in rest in bed is upwards 

 of twenty per cent., and in rest in the room fifty to sixty per 

 cent, higher than that in enforced rest. It may thus be per- 

 ceived that the actual determination of the maintenance ex- 

 change is by no means an easy task. It is essential to ex- 

 clude not only the activity of the striated musculature but 

 also that of the involuntary muscle of the gastrointestinal 

 canal, and of that of the periodically acting glands as well. 

 That this is not possible in a literal sense of course goes 

 without stating; we do the best we can, and are careful to 

 determine the gas exchange in a period of fasting, about 

 twelve hours after the last meal, in a restful posture, and 

 with most careful avoidance of all voluntary movements. 

 The fact is, however, that for one and the same person 

 under these conditions, in the course of many years, exactly 

 the same oxygen consumption and the same carbonic acid 

 production are usually obtained in the same period of ob- 

 servation. 19 Sleeping or waking play no important part. 



Significance of Surface Development and Volume of 

 Body Protein. It will be readily appreciated that in com- 



17 A. Lowy, Handb. d. Biochem., 4', 172, 1908. 



18 Literature upon Maintenance Exchange : A. Magnus-Levy, Handb. d. 

 Pathol. d. Stoffw., 2d ed., 1, 213, 222-225, 279-296, 1906; A. Lowy, Handb. d. 

 Biochem., 4', 172-199, 1908. 



"Thus, for example, A. Lowy (Deutsche med. Wochenschr., 1910, 1797) 

 observed in an experiment subject at absolute rest and during fasting the 

 following oxygen consumption (cubic cm. pro minute) : in 1888, 236.0; in 

 1895, 227.9; in 1901, 230.7; in 1902, 238.1; in 1903, 228.0. 



