9 1 6 METABOLISM. 
cumstance of the fat and liver cells seizing upon non-proteid materials and storing 
them as fat and glycogen in an animal in this condition, is not surprising, 
and is quite compatible with the view that in a normally nourished animal, 
where they are in excess, the non-proteids are the main energy producers. 
The most probable view appears to be that muscle, like other cells, 
although it can only actually build up its bioplasm out of proteicl, is 
nevertheless able to produce muscular energy by oxidation — perhaps 
occurring outside the actual molecules of the bioplasm, but under their 
direct influence — of any or all the organic foodstuffs, 1 and that this 
process is attended only by such small disintegration and loss of the 
proteid material of the bioplasm as is necessarily attendant upon its 
functional activity — a loss which is comparable to the wear and tear of 
the working parts of a machine as distinct from its consumption of fuel. 
As a matter of fact, it has been shown by Zuntz, 2 that in a dog, 
abundantly fed on a mixed diet and caused to produce external work, 
the amount of extra proteid used during the period of work was less 
than one-twentieth part of the amount the oxidation of which would 
have been necessary to account for the work done. Moreover, in in- 
anition it is the glycogen and fat of the body which is first drawn upon, 
and this both at rest and during work. When the same dog was made 
to work during fasting, the N-secretion rose only very slowly ; the 
w T ork was almost entirely clone on the non-proteids of the body. 
It may be remarked that muscular activity is always accompanied 
by a production of energy far in excess of that which is necessary for 
the performance of the external work done. Thus it was found by 
Hanriot and Bichet 3 that when work was done there was seven times 
as much C0 2 produced as would have been accounted for by the oxida- 
tion necessary to perform the work. The additional energy appears of 
course as heat. On the other hand, it has been doubted whether there 
is any production of heat in the total absence of muscular activity.' 1 
Hanriot and Richet found the C0. 2 to increase in greater proportion than 
the oxygen absorbed, so that the respiratory quotient became larger. Severe 
muscular exercise is stated to increase both the phosphoric acid 5 and the 
sulphur of the urine ; 6 the former more in proportion than the increase of N 
which may occur ; the latter about in proportion to the increased N", and in 
the form of ordinary sulphates. 7 Along with the increase of phosphoric acid, 
there is also an increased excretion of lime, indicating, according to I. Munk, 
destruction of bony tissue. 
Metabolism of Carbohydrate. 
The formation of glycogen. — The carbohydrates of the food are 
mainly converted by digestion into maltose, which passes in the process 
of absorption and assimilation into dextrose, this being the only sugar 
1 Cf. NoUl Paton, Ediu. Med. Journ., June 1895. Also Rep. Lab. Boy. Coll. Phys., 
Edin., 1891, vol. iii. 
2 With Frentzel and Loeb, Arch./. Physiol., Leipzig, 1894, S. 541 (Vcrhandl. d. 
physiol. Gesellsch, zu Berlin). See also Speck, ibid., 1895, S. 465. 
3 "Travaux du laboratoire de Ch. Richet," 1893, tome i. 
4 Cf. on this subject Speck, Ccnlralbl. f. d. med. Wissensch. , Berlin, 1889 ; also article 
"Animal Heat," p. 840. 
5 Klug and Olsavsky, Arch./, d. ges. Physiol., Bonn, 1S93, Bd. liv. S. 21. 
6 Beck and Benedikt, ibid., S. 27. 
7 I. Munk, Vcrhandl. d. physiol. Gesellsch. zu Berlin, 5th April 1895 (in Arch. f. 
Physiol., Leipzig). 
