APPENDIX II. 157 



after the ascent the percentage had increased to *14 

 per cent., then the amount of creatin thus exception- 

 ally retained would amount to 4*64: grams, which 

 would be derived from 8 '4 grams of muscle. 



The speaker had been unable to determine the 

 calorific effect of creatin, and consequently the 

 actual energy developed by the transformation of 

 muscle into creatin ; for, although he was kindly 

 furnished with an ample supply of this material by 

 Dr. Dittmar, yet all attempts to burn it in the calo- 

 rimeter were fruitless. Even when mixed in very 

 small proportions with chlorate of potash and other 

 combustibles of known value, the mixture invariably 

 exploded violently on ignition. Although actual 

 determination thus fails us, there can be no doubt 

 that the transformation of muscle into creatin and 

 other non-nitrogenous products must be attended by 

 the liberation of far less actual energy than its 

 transformation into urea, carbonic acid, and water. 

 To be convinced of this, it is only necessary to com- 

 pare (under equal nitrogen value) the formulae of 

 muscle, creatin, and urea, remembering at the same 

 time that the nitrogen probably possesses no thermal 

 value, and that each atom of oxygen destroys 

 approximately the thermal effect of two atoms of 

 hydrogen: 



Comparable Powerful or 



formulas. unburnt matter. 



Muscle . . . C 24 H 37 N 6 O 7 C 24 H 23 



Creatin . . . 0, H 18 N 6 O 4 C 8 H 10 



Urea . . . C 8 H 12 N 6 O 3 C 3 H 6 



Thus it is evident that the amount of creatin 



