526 MAINTENANCE EXCHANGE AND GROWTH 



transforming a much greater amount (about quadruple) of 

 energy. 24 



Flattering as this exceptional position may be for the 

 members of the species Homo sapiens, a uniformity broken 

 by so striking an exception cannot well help arousing from 

 the very outstart serious thoughts as to the validity of the 

 law itself. From observations made in Zuntz's laboratory 

 by Gerhartz it would seem that the maintenance require- 

 ment for the growing dog is not, as Eubner has it, simply a 

 function of the surface area ; 25 and, more particularly, H. 

 Friedenthal has brought forward a series of observations 

 which in general do not conform to Buhner's laws of 

 growth. 26 It will probably be in every way more valuable 

 if, instead of stating his own opinion upon the subject, the 

 author presents the judgment of N. Zuntz, one of the best 

 authorities upon the physiology of metabolism: "The 

 views of Eubner as to the remarkably uniform amount of 

 energy (except in case of man) consumed by an organism in 

 course of growth to double its weight are in the meantime 

 shaken by the discoveries of Friedenthal, and man forced 

 from the special position which seemed to belong to him. 

 And it is impossible to suppress considerable doubt as to the 

 validity of the idea that living matter after transforming a 

 given number of calories is incapable of further activity, and 

 that, therefore, death naturally ensues when a certain num- 

 ber of calories per kilogram of bodyweight have been con- 

 verted. But the way these conceptions were developed is 



24 M. Rubner, Arch. f. Hygiene, 66, 1908; Das Problem der Lebensdauer 

 und seine Beziehungen zu Wachstum und Ernahrung, 1908; Kraft und Stoff 

 im Haushalt des Lebens, Leipzig, Akad. Verlagsanstalt, 1909. Rubner has re- 

 cently (Sitzungsber. d. preuss. Akad., 1911, 440) taken up the question of the 

 ratio of wear. It has been calculated that on full nitrogen-free diet about one- 

 thousandth of the total nitrogen supply of the body is daily eliminated in the 

 urine and faeces, so that in the course of a few years a complete renewal of 

 all tissues must necessarily take place. 



25 H. Gerhartz (N. Zuntz's Lab.), Biochem. Zeitschr., 12, 97, 1908. 



20 H. Friedenthal, Berliner physiolog. Gesellsch., June 3, 1910; Centralbl. f. 

 Physiol., 24, 705, 1910; cf. also the rejoinder by Rubner. 



