172 



KNOWLEDGE ♦ 



[Aug. 29, 1884. 



can be placed on certain results which have been accepted 

 with considerable confidence. Not only does the rate of in- 

 crease of temperature with descent vary greatly in different 

 regions, but in some places the law is reversed. Thus, in 

 the new Almaden Quicksilver Mine in California, the tem- 

 perature is about 115° at a depth of GOO ft., while in the 

 deepest part of the mine, 1,800 ft. below the surface, and 

 500 ft. below the sea level, the temperature is not higher 

 than 80''. At the Eureka mines, California, the tempera- 

 ture, 1,200 ft. below the sea level, is not higher than it is 

 100 ft. below that level. — The Newcastle Weekly Chronicle. 



THE CHEMISTRY OF COOKERY. 



By W. Mattieu Williams. 

 XLI.— AUTHOKITIES ON TEA AND COFFEE. 



SINCE the publication of my last I have been reminded 

 of the high authorities who have defended the use of 

 the alkaloids, and more particularly of Liebig's theory, or 

 the theory commonly attributed to Liebig, but which is 

 Lehmann's, published in Liebig's "Annalen," Vol. 87, and 

 adopted and advocated by Liebig with his usual ability. 



Lehmann watched for some iceeks the effects of coffee 

 upon two persons in good health. He found that it re- 

 tarded the waste of the tissues of the body, that the pro- 

 portion of phosphoric acid and of urea excreted by the 

 kidneys was diminished by the action of the coffee, the 

 diet being in all other respects the same. Pure caffeine 

 (which is the same as theine) produced a similar effect, 

 the aromatic oil of the coffee, given separately, was found 

 to exert a stimulating effect on the nervous system. 



Johnstone ("Chemistry of Common Life") closely fol- 

 lowing Liebig, and referring to the researches of Lehmann, 

 says : — "The waste of the body is lessened by the intro- 

 duction of theine into the stomach — that is, by the use of 

 tea. And if the waste be lessened, the necessity for food 

 to repair it will be lessened in an equal proportion. In 

 other words, by the consumption of a certain quantity of 

 tea, the health and strength of the body will be maintained 

 in an equal degree upon a smaller quantity of ordinary 

 food. Tea, therefore, saves food — stands to a certain extent 

 in the place of food — while, at the same time, it soothes 

 the body and enlivens the mind." 



He proceeds to say that " In the old and infirm it serves 

 also another purpose. In the life of most persons a period 

 arrives when the stomach no longer digests enough of the 

 ordinary elements of food to make up for the natural daily 

 waste of the bodily substance. The size and weight of the 

 body, therefore, begin to diminish more or less perceptibly. 

 At this period tea comes in as a medicine to arrest the 

 waste, to keep the body from falling away so fast, and thus 

 to enable the less energetic powers of digestion still to 

 supply as much as is needed to repair the wear and tear 

 of the solid tissues." No wonder, therefore, says he, " that 

 the aged 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." 



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 deter- 



mining the quantity of carbonic acid given o£f by combus- 

 tion. This method is imperfect, inasmuch as it, onlv 

 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 this method of measuring 

 the respired carbonic acid. His results were fir.st 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 experi- 

 ments, 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 nlti- 

 matel}' produce the carbonic acid to be evolved. Instead, 

 therefore, of supplying nutritive matter, it causes the assimi- 

 lation 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 jireceding quotations from 

 Johnstone : — " 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 j* less adapted to the jyoor 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 v.-ith deficient 

 food, and thereby exaggerate the evils of the jyoor ; " 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 v:aste 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, and millinery, the absence of any refuta- 

 tion 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 sub- 

 ject, and his original researches constitute a lifetime's 

 work, not of mere random change-ringing among the ele- 

 ments 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 coutradicts Lehmann, and 

 arrives at directly contradictory physiological residts and 

 practical inferences. 



Are we, therefore, to conclude that he has blundered in 

 his analysis, or that Lehmann has done so 1 



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. 



