The Mttabolism of Voluntary Muscle 229 



It may be concluded, therefore, that when the blood supply is adequate 

 and the period of rest sufficient as compared with that of activity, there 

 is, pari passu, a complete restitution of the substances used up by muscle 

 in contraction. 



Whni, however, the blood supply is restricted, this does not occur. 

 There is then a reduction of the store of energy-yielding solids held in 

 the mu.scle, and the loss is not confined to non-nitrogenous organic sub- 

 stances, but extends to the creatine as well. In what form the creatine 

 leaves the muscle has not been ascertained. This and other problems 

 concerned with the metabolism of active muscle have yet to be 

 investigated. But it may be recalled that Weber (24), as also Howell and 

 Duke (25), found creatine to be given oti" by the surviving heart to the 

 tiuid circulating throufrh it. 



Analyses of the creatinine in the resting and active muscles by Folin's 

 recent method gave very discordant results, and no trustworthy deductions 

 can be drawn from them. 



Conclusions. 



1. In voluntary muscle with intact circulation, excited intermittently 

 for over two hours in periods of one-minute excitation followed by two- 

 minutes rest, there is no loss of creatine, of total nitrogen, or of 

 total solids. 



2. On the other hand, in voluntary muscle with restricted circulation, 

 excited in the same way and for the same length of time, there is a loss 

 of the solids amounting to over 10 per cent. ; of creatine to over 6 per cent.; 

 and of total nitrogen to over 4 per cent. 



3. It would appear, therefore, that under normal conditions with intact 

 blood supply the substances used up to furnish the energy of contracting 

 muscle are restored as fast as they are consumed. But if the blood supply 

 be deficient the store of energy-yielding material is depleted, and the loss 

 is not confined to non-nitrogenous material, but extends to creatine and 

 possibly to other nitrogenous substances as well. 



LITERATURE REFERENCES. 



(1) LiEBiG, Amialen, 1847, Ixii. 257-369. 



(2) Sarakow, "Beitrag z. Physiologie d. Muskelstoffwechsels," Virch. Archiv, 

 1863, xxviii. 544. 



(3) SczELKOW, "Ueber Kreatingehalt cl. Muskeln," Centralbl. f. d. med. 

 Wissensch., 1866, jN^o. 31, p. 481. 



(4) MoNARi, Atti R. Accad. d. Sci. d. Torino, 1887, xxii. 846-864; Abstr. 

 Maly's Jahresb., 1887, xvii. 311-312. 



(5) Nawrocki, "Beitnige z. Stoffwechwechsel im Muskel," Centralbl. f. med. 

 Wissensch., 1865, p. 417. 



