211 



The last section of the paper is devoted to the consideration of the 

 mechanical effects of muscular contraction ; and experiments are 

 stated with a view to compare the effective work of a muscular con- 

 traction, as determined empirically with the work calculated according 

 to the principles of the dynamical theory of heat. 



Employing the dynamometer already described in the fourth series 

 of his researches, the author has found that the mechanical work 

 effected by a single contraction of the gastrocnemius muscle of a 

 frog may be expressed by 0' 0000 145 7 kilogramme-metres. Deter- 

 mining next the quantity of zinc required to be oxidated in the pile 

 in order to excite a single contraction, he finds that the force de- 

 veloped by the muscle is enormously greater than could be accounted 

 for on the supposition that it is produced by the conversion into 

 muscular energy of the equivalent of electricity corresponding to the 

 quantity of zinc oxidated. He accordingly concludes, that the 

 electric current which excites a muscle to action does not represent 

 the force exerted by the muscle, which is more probably to be 

 referred to the chemical changes, such as oxidation, which take 

 place in the muscular tissue during contraction. The consideration 

 of this branch of the inquiry will form the subject of the second part 

 of the Memoir. 



XII. " On the Existence of Multiple Proportion in the quan- 

 tities of Heat produced by the Chemical Combination of 

 Oxygen and other bodies." By THOMAS WOODS, M.D. 

 Communicated by Professor STOKES, Sec. R.S. Received 

 June 7, 1856. 



(Abstract.) 



This paper is, in substance, the same as a former paper, bearing a 

 similar title, read before the Royal Society on the 10th January 1856, 

 but contains a more detailed account of the mode of performing the 

 experiments. A repetition of the experiments mentioned in the 

 former paper has led to very nearly the same numerical results, 

 except in the case of molybdenum, which is found to give 4 -8 ther- 

 mal units by combining with oxygen, instead of 3'38, the number 

 formerly given. 



