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TEE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



the results of their inquiries into the relation be- 

 tween muscular work and heat. 



It has often been a favorite pursuit of physi- 

 ologists to attempt to demonstrate the analogy 

 between muscular work and that of a steam- 

 engine. Beclard, many years ago, made this at- 

 tempt, and thought he had observed that less heat 

 was developed in a muscle when it performed 

 external work than when it contracted without 

 doing so, even against resistance. His experi- 

 ments, however, were exceedingly rough, being 

 performed with ordinary mercurial thermometers, 

 and without any sufficient precautions against 

 error. The thermo-pile as a means of research 

 was unknown to him, and he himself was dis- 

 satisfied with his results. He even proposed a 

 series of crucial tests, but did not carry them out 

 into practice. Later Dr. Solger made some in- 

 vestigations in the same direction with more re- 

 fined apparatus and method. He even detected, 

 as he supposed, some exceedingly momentary fall 

 of temperature of the muscle at the instant of con- 

 traction, which was, however, immediately fol- 

 lowed by a rise. Mayerstein and Thiry followed 

 on the same lines of experiment with doubtful 

 results, but on the whole confirming Solger's ob- 

 servations. These observations are now merely 

 of historical interest, as the more accurate investi- 

 gations of late years have demonstrated that these 

 somewhat anomalous results were due rather to 

 physical errors in experiment than to physiologi- 

 cal causes. It was shown in particular that the 

 " momentary cooling " was most probably a re- 

 sult of evaporation, as due allowance had not 

 been made by any of the observers for this event. 1 



For the only thoroughly reliable researches 

 into the quantitative relations subsisting between 

 muscular heat and work, we are indebted to Prof. 

 Heidenhain, of Breslau, whose experiments, car- 

 ried on for a long period at the Physiological In- 

 stitute, are models of care and exactitude. It 

 would be out of place here to enter into any de- 

 tailed account of his apparatus, and of his almost 

 infinite precautions against error. I may say that 

 the chief elements used were a very delicate re- 

 flecting galvanometer, a thermo-electric multiplier 



1 Hirn also attempted to draw some analogy be- 

 tween the development of heat in the steam-engine 

 and that in muscle— only a matter of interest as recall- 

 ing the verdict that was passed upon it by C. Voit : 

 "Die Bemiihungen welche Hirn zu dem Zwecke an- 

 stellte, nachzuweisen, das die mechanische Leistnngen 

 des Organismns zu seiner WSrmeprodnction in dem- 

 selhen "Verhaltnisse stehen, wie in der Dampfma- 

 schine, ?iud aus mehrfachen Grundenate gescheilert zu 

 betrachten." 



of bismuth and antimony, by means of which the 

 most minute changes in temperature, to which the 

 ordinary thermometer would be quite insensible, 

 could be readily detected, and an elaborate con- 

 trivance for suspending the muscles and keeping 

 them in equable contact with the thermo-pile, 

 both during rest and during the ever-varying 

 amounts of contraction. The contraction of the 

 muscles was induced, of course, by the action of 

 the electric current. The full account of his pro- 

 ceedings would occupy a volume. I must be con- 

 tent to give a brief resume of the most important 

 results. 



Heidenhain experimented on muscle contract- 

 ing freely without any weight or hinderance, on 

 muscle exposed to stimulation, but prevented from 

 contracting by being firmly attached to an immov- 

 able frame at each end, and on muscle allowed to 

 contract freely, but lifting varying weights. Va- 

 ried in every possible way, the general result was 

 always the same. Accompanying every action 

 of muscle, there was an elevation of temperature; 

 and this elevation was invariably greater when 

 work was performed than when the muscle con- 

 tracted without doing work ; it was also to a cer- 

 tain extent proportional to the amount of work 

 done, but not always accurately so, as the phe- 

 nomena varied according as the muscle was fresh 

 in action or wearied after many contractions. In 

 none of the many series of experiments, however, 

 was there any departure from this general princi- 

 ple, that the more external work teas done, the more 

 internal heat ivas developed in the muscle. 



The latest conclusions of accurate science on 

 this subject are very briefly sketched in Nature 

 for September 20, lSYY, and Heidenhain's experi- 

 ments are thus alluded to : 



" The fact that in the living muscle heat always 

 appears when the muscle does work (Heidenhain 

 having shown that of two muscles equally weight- 

 ed and undergoing equal contractions, one doing 

 external work, while the other does none, the for- 

 mer gives out more heat than the latter-), is an ex- 

 ception to the general rule in mechanics, that heat 

 disappears when work is done." 



Thus, then, it is demonstrated that muscle is 

 not merely 'mechanical in its action, and a fortiori 

 that the animal of which it forms a part is not a 

 machine. Its action is conditioned by forces, of 

 the essential nature of which we know nothing, 

 the correlative of which cannot be traced ; and to 

 say that these are " the compounding of inorganic 

 forces" is merely to clothe our utter ignorance 

 of the nature of life in a form of words which will 

 amuse the unphysiological ear, but which has no 



