The Chemistry of Cookery

by W. Mattieu Williams

All this is based upon the researches of Lehmann and others, who measured the work of the vital furnace by the quantity of ashes produced—the urea and phosphoric acid excreted. But there is also another method of measuring the same, that of collecting the expired breath and determining the quantity of carbonic acid given off by combustion. This method is imperfect, inasmuch as it only measures a portion of the carbonic acid which is given off. The skin is also a respiratory organ, co-operating with the lungs in evolving carbonic acid.

Dr. Edward Smith adopted the method of measuring the respired carbonic acid only. His results were first published in ‘The Philosophical Transactions’ of 1859, and again in Chapter XXXV. of his volume on ‘Food,’ International Scientific Series.

After stating, in the latter, the details of the experiments, which include depth of respiration as well as amount of carbonic acid respired, he says: ‘Hence it was proved beyond all doubt that tea is a most powerful respiratory excitant. As it causes an evolution of carbon greatly beyond that which it supplies, it follows that it must powerfully promote those vital changes in food which ultimately produce the carbonic acid to be evolved. Instead, therefore, of supplying nutritive matter, it causes the assimilation and transformation of other foods.’

Now, note the following practical conclusions, which I quote in Dr. Smith’s own words, but take the liberty of rendering in italics those passages that I wish the reader to specially compare with the preceding quotations from Johnston: ‘In reference to nutrition, we may say that tea increases waste, since it promotes the transformation of food without supplying nutriment, and increases the loss of heat without supplying fuel, and it is therefore especially adapted to the wants of those who usually eat too much, and after a full meal, when the process of assimilation should be quickened, but is less adapted to the poor and ill-fed, and during fasting.’ He tells us very positively that ‘to take tea before a meal is as absurd as not to take it after a meal, unless the system be at all times replete with nutritive material.’ And, again: ‘Our experiments have sufficed to show how tea may be injurious if taken with deficient food, and thereby exaggerate the evils of the poor;’ and, again: ‘The conclusions at which we arrived after our researches in 1858 were, that tea should not be taken without food, unless after a full meal; or with insufficient food; or by the young or very feeble; and that its essential action is to waste the system or consume food, by promoting vital action which it does not support, and they have not been disproved by any subsequent scientific researches.’

This final assertion may be true, and to those who ‘go in for the last thing out,’ the latest novelty or fashion in science, literature, or millinery, the absence of any refutation of later date is quite enough.

But how about the previous ‘scientific researches’ of Lehmann, who, on all such subjects, is about the highest authority that can be quoted. His three volumes on ‘Physiological Chemistry,’ translated and republished by the Cavendish Society, stand pre-eminent as the best-written, most condensed, and complete work on the subject, and his original researches constitute a lifetime’s work, not of mere random change-ringing among the elements of obscure and insignificant organic compounds, but of judiciously selected chemical work, having definite philosophical aims and objects.

It is evident from the passages I have emphatically quoted that Dr. Smith flatly contradicts Lehmann, and arrives at directly contradictory physiological results and practical inferences.

Are we, therefore, to conclude that he has blundered in his analysis, or that Lehmann has done so?

On carefully comparing the two sets of investigations, I conclude that there is no necessary contradiction in the facts: that both may be, and in all probability are, quite correct as regards their chemical results; but that Dr. Smith has only attacked half the problem, while Lehmann has grasped the whole.