The Chemistry of Cookery

female, who has barely enough income to buy what are called the common necessaries of life, should yet spend a portion of her small gains in purchasing her ounce of tea. She can live quite as well on less common food when she takes her tea along with it_; while she feels lighter at the same time, more cheerful, and fitter for her work, because of the indulgence.’ (The italics are my own for comparison with those that follow.) 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