6o RESPIRATORY EXCHANGE OF ANIMALS AND MAN 



[1891]). Differences of a few per cent, are often observed (Johansson 

 [1896, 1897, 1898]), but variations of I to 2 litres in the ventilation per 

 minute are sufficient to explain them. 



In series of experiments made in short intervals during twenty-four 

 hours Magnus-Levy [ 1 893 ] and Johansson [ 1 898] observed irregular and 

 slight variations. Johansson found for instance on himself an average 

 CO 2 production per hour of 22-2 o'S gr. The average deviation is 

 3-6 per cent, of the total. If the body weight (and composition) re- 

 mains unaltered the standard metabolism will remain constant over 

 very long periods (Johansson, Magnus-Levy). Magnus-Levy's experi- 

 ments lasted two years and Johansson's seven months. A series of fifty- 

 one determinations by Benedict and Cathcart [1913] of the standard 

 metabolism of an athlete made almost daily over a period of three 

 months show a variation of fi = 4*9 per cent., 1 which is all that 

 can be desired on a person not specially trained to maintain muscular 

 inactivity. 



Experiments on several warm-blooded animals have confirmed 

 these results (Rubner, 1887), and it has been shown further that curari 

 when not given in excessive doses has no influence upon the respir- 

 atory exchange which remains the same as during natural complete 

 rest (Frank and Voit [1902], Frank and Gebhard [1902]) ; when given 

 in very large doses (Zuntz, 1876) it is stated by Mansfeld [1915] to 

 abolish the muscular tone and thereby lower the respiratory exchange 

 considerably. 



The remaining chapters of the present monograph will deal with 

 the standard metabolism, its variations under the influence of internal 

 and external factors, its alterations during the life of the individual, 

 and the differences found between different individuals, species, and 

 larger systematic groups. In a great many cases, however, experi- 

 ments must be considered in which standard conditions have not been 

 maintained, because better material is not available. 



The metabolism depending upon functional activity will not be 

 discussed in detail as that will be treated in a special monograph of 

 this series. For present purposes it is necessary only to emphasize 

 the fact that, as in isolated organs, the functional activity of the whole 

 organism causes an increased metabolism which is added to the 

 standard. Careful experiments which demonstrate this fact have 

 been made by Johansson [1901]. He found that when he lifted a 



1 Calculated by Lindhard, Pfl. Arch., 1915, 161, 346. 



