Nov. 4, 1861.] 



• KNOWLEDGE 



THE RELATION OF FOOD TO 

 MUSCULAR WORK. 



Bv Dr. W. B. C.«iPEN-TER, F.R.S. 



[In an article on the " Use and Abuse of Food," repnblished in my 

 '■ Pleasant Ways in Science," tliere is a passage in which Liebi;;'s 

 mistake abont the relation between nitrogenous or flesh-torming 

 food and work is quoted without being corrected. I was not aware 

 when the article was written ,(1867) that scientific experiments 

 were in progress which were eventually to completely expose the 

 fallacy of Liebig's position. When the article was republished 

 these experiments had long since been brought to a satisfactory 

 issue. Although the point does not importantly affect my ess.iy 

 regarded as a whole (for the material of a machine, as well as tlie 

 source of its working energj' must be kept in repair, and the work- 

 man does not get less good from his food because he takes it under 

 a misapprehension as to the particular benefit it will do him), the 

 mistake is one which should hare been corrected. The interpreter 

 of scieotific statements, too technical for general comprehension, 

 must not be content with presenting correctly and intelligibly the 

 accepted teaching of an authority in any special branch of science. 

 He must assure himself, as time passes, that the teaching which 

 was regarded as sound when the subject was first dealt with, has 

 not undergone correction in the mean time. If I had done this in 

 the present case (as I have in general been careful to do), the error 

 in question would not have appeared in the pages of " Pleasant 

 Ways in Science." The following exceedingly interesting paper, by 

 Dr. Carpenter, puts the matter in the proper light. He speaks, I 

 need hardly say, "as one having authority." I may point out that 

 it is one of the great advantages of a journal like the present that 

 errors into which even the most careful will fall from time to time, 

 will here be corrected at once. In the columns of a monthly 

 magazine correspondence would be inconvenient, even if permitted. 

 Here the freest ((uestioning and discussion is invited, and it is par- 

 ticularly desired that those having special knowledge of a subject 

 will call attention to, and correct, any statements which may appear 

 to them erroneous. — Ed.] 



PART I. 



THAT " the evil which men do Uves after them,"' is often 

 exemplified by the continued prevalence of scientific 

 doctrines accredited by the authority of great names, long 

 after their fallacy has been demonstrated by the subsequent 

 researches of other inquirers to the satisfaction of all 

 competent judges. For, if these demonstrations be not 

 presented to the world under the sanction of a like 

 authority, tlie old errors are continually reproduced by 

 popular expositors, and unquestioningly accepted by ordi- 

 nary readers. 



Having met with a notable instance of this kind not 

 long ago, in the reproduction, as an accepted physiological 

 verity, of the doctrine of Liebig as to the direct depend- 

 ence of muscular energy on the expenditure of nitrogenous 

 food, I think that a journal which aims to communicate 

 positive " knowledge " to its readers may be an appro- 

 priate medium for a brief statement of what are now 

 accepted by all scientific Physiologists as the facts of the 

 case. 



It is no derogation to the well-established fame of Liebig 

 as one of the greatest Chemists of his day,* to aflirm that 

 when he passed out of his own domain into that of 

 Biology, he made many and flagrant mistakes. Looking 

 back after an interval of nearly forty years, at his " Organic 

 Chemistry in its Relations to Physiology and Pathology," 

 I am really astonished at the reckless audacity of some of 

 his assertions; as, for instance (1st edit 1842, p. 219), 

 that " we know with certainty that the nerves are the con- 

 ductors of mechanical effects, and that by means of them 

 motion is propagated in all directions ; " and that "the 

 heart and intestines do not generate the moving power in 

 themselves, but receive it from other quarters." He might 



• See "The Life-Work of Liebig," by Prof. Hofmann, the 

 " Faraday Lecturer" for 1875. 



just as well have said that " we know with certainty that 

 when a charge of gunpowder or dynamite is exploded by 

 an electric spark, it is the conducting wire that supplies 

 the energy which rends asunder the rock." For nothing 

 was even then more certain, than tliat the heart, intestines, 

 and all other muscles fumisli, in virtue of their own con- 

 tractility, the power (or, as it would now be called, the 

 " potential energy ") which protluces their mechanical 

 effects, this being simply called into action by the nervous 

 stimulus. 



Another most noteworthy example presents itself in 

 Liebigs denunciation of the " germ-doctrine " of fermen- 

 tation and contagion, which was then being built-up on 

 the basis supplied liy the microscopic discoveries of 

 Cagniard de la Tour on the fungoid nature of yeast, and of 

 Audouin and Milne-Edwards on the like character of the 

 ^Muscardine-disease of silkworms. " A theory," he says 

 (3rd edit. 1846, p. 212), "of the cause of fermentation and 

 putrefaction, which is utterly fallacious in its fundamental 

 principles, has hitherto furnished the cliief .support of the 

 parasitic theory of contagion. The advocates of this 

 theory regard putrefaction as a decomposition of organic 

 beings caused by infusoria and fungi, and consider every 

 putrefying body as a breeding-place for infusoria or a 

 nursery for fungi ; and where organic bodies putrefy over 

 a large surface, the whole atmosphere, according to this 

 view, must be filled with the germs of these infusoria 

 and fungi. The germs of these organised beings are, in 

 this theory, the germs of disease or of the causes of 

 disease." Yet it is this very doctrine, the complete estab- 

 lishment of which by the admirable researches of Pasteur, 

 and of those who have followed in the line of inquiry 

 which he so clearly marked out, has not only given the 

 true interpretation of the phenomena of Fermentation, but, 

 in its application to Pathology, is now serving as the basis 

 for " preventive " medicine and " antiseptic " surgery. 

 And I feel sure that Liebig himself, had he lived into the 

 present era, would have been quite ready to admit its truth ; 

 for he was the last man to persist in views no longer tenable, 

 merely because he had himself advanced them. " There is 

 no harm in a man's making mistakes," he used to say, 

 " but great harm in his making none, for he is sure not 

 to have worked." And Professor Hofmann records ha%'ing 

 been exhorted by Liebig " not to keep in your house from 

 night till morning an error you liave become cognisant of." 



Now Liebig's chemical diWsion of food-materials into 

 plastic, or "tissue-forming," and respiratory, or "heat- 

 producing," was unquestionably an immense advance ; and 

 the basis of it is still universally recognised as sound. I 

 can myself remember the time when it was a question 

 whether the nitrogenous components of the blood, and the 

 tissues formed at their expense, can be built-up in the 

 animal body, with the aid of atmospheric nitrogen, out of 

 starch, sugar, fat, and other non-nitrogenous h^'drocarbons. 

 Chemistry had not then shown the almost e.xact conformity 

 of many Vegetable compounds to the albumen which was 

 regarded as the fundamental constituent of Animal food ; 

 and while it was by Mulder that the doctrine of the 

 /(ro/t'in-compounds was worked out, which, with some 

 modifications, is now generally accepted, it was by Liebig 

 that the impossibility of supposing that animals can form 

 their tissues out of anything else than the "proteids" 

 originally generated by Plants, was first definitely insisted 

 on. He was not aware, however, that the formation of 

 " protoplasm " requires fat as well as proteids ; and that 

 thus fat is to some extent a tissue-food. But he was 

 unquestionably right in affirming that animal tissues 

 cannot be manufactured out of sacchariiie compounds (as 

 starch and sugar), unless these have been pre\'iously 



