168 APPENDIX II. 



It has been already stated as a proposition upon 

 which all are agreed, that food, and food alone, is 

 the ultimate source from which muscular power is 

 derived ; but the above determinations and conside- 

 rations, the speaker believed, prove conclusively, 

 firstly, that the non-nitrogenous constituents of the 

 food, such as starch, fat, &c., are the chief sources 

 of the actual energy, which becomes partially trans- 

 formed into muscular work ; and secondly, that the 

 food does not require to become organized tissue 

 before its metamorphosis can be rendered available 

 for muscular power; its digestion and assimilation 

 into the circulating fluid the blood being all 

 that is necessary for this purpose. It is, however, 

 by no means the non-nitrogenous portions of food 

 alone that are capable of being so employed, the 

 nitrogenous also, inasmuch as they are combustible, 

 and consequently capable of furnishing actual energy, 

 might be expected to be available for the same pur- 

 pose ; and such an expectation is confirmed by the 

 experiments of Savory upon rats,* in which it is 

 proved that these animals can live for weeks in 

 good health upon food consisting almost exclusively 

 of muscular fibre. Even supposing these rats to 

 have performed no external work, nearly the whole 

 of their internal muscular work must have had its 

 source in the actual energy developed by the oxida- 

 tion of their strictly nitrogenous food. 



It can scarcely be doubted, however, that the 

 chief use of the nitrogenous constituents of food is 

 for the renewal of muscular tissue ; the latter, like 

 * The Lancet, 1863, pages 381 and 412. 



