290 Prof. Matteucci on the Origin of Muscular Power. 



gical investigations, and which appear to me to contribute at the 

 present moment towards the completion of our knowledge on this 

 important part of animal physics. 



In the first place I may remark, in reference to the Table of 

 results of Dr. E. Smith's investigations on the quantity of car- 

 bonic acid exhaled during rest, and during the muscular exertion 

 of man in various kinds of work, that it may be of service, as 

 regards the conclusion which it is sought to draw from these 

 results, to call to mind some experiments of mine upon the ex- 

 halation of carbonic acid, by muscles deprived of blood, during 

 repose and during contraction. I believe, in fact, that in the 

 experiments of Dr. E. Smith, the greater part of the carbonic 

 acid exhaled is derived from the carbonic acid dissolved in the 

 blood, and which is exhaled in abundance owing to the greater 

 activity of the work of respiration during exercise ; whilst, on 

 the other hand, in the muscles of frogs prepared as in my expe- 

 riments, the greater part of the carbonic acid which is given off 

 by those muscles during contraction must be attributed to the 

 oxidation of the muscular matter, or of the substances which are 

 mixed with it. I may add that in recently repeating, with the 

 same results, these experiments on the muscles of frogs which 

 had been washed several times in water, it appeared to me that, 

 whilst entirely admitting the accuracy of your conclusions, and 

 of those drawn from the experiments of Fick and Wislicenus, one 

 cannot avoid conceding that the muscular fibre itself is also oxi- 

 dized and burnt during contraction. 



You say in your memoir, "a command is sent from the brain 

 to the muscle, the nervous agent determines oxidation ; the po- 

 tential energy becomes actual energy, &c." On this part of the 

 subject I wish to mention a conclusion drawn rigorously from 

 experiment, and which throws much light precisely upon this 

 point. It is easy to imagine an experiment in which the 

 crural nerve of a prepared frog is excited by the interrupted 

 passage of an electric current, whilst the work of the muscle 

 thrown into contraction by this excitation is determined in 

 metrekilograms. This experiment is doubtless not free from 

 error, which, however, operates in the same direction, viz. 

 to diminish the total muscular work developed by the mus- 

 cular contraction. In fact it is known that there are muscles 

 which, in the sum total of contractions, act to diminish the height 

 to which the little weight attached to the leg is lifted. I have 

 proved that there is also heat developed by the contraction of 

 muscles deprived of blood. I repeat, then, the work calculated 

 from the lifting of a weight, and the height to which it is lifted, 

 is certainly inferior to the total work of muscular contraction. 

 On the other hand, however, whilst employing the most feeble 



