Deo. f), 1884.] 



♦ KNOV/LEDGE ♦ 



455 



MAGAZINE OF SCIENCE 

 PlainlyWorded-exactlydescribed 



LONDON: FRIDAY, DEC. 5, 1884. 



OONTBNTS OP No. 162. 



The Chemistry of Cookery. XLVIII. 

 By W. Mattieu Williams 455 



Chats about Geometrical Measure- 

 ment. (lUua.) By K. A. Proctor 456 



Sunspots, Temperature, and After- 

 glow 458 



The Entomology o£ a Pond. By 

 E. A. Butler 458 



The World's First Meridian. By 

 Hichard A. Proctor 460 



Our Scientific Industries : Gas. By 

 W. Slingo 462 



The Tricycle in 1S84 463 



Earth's Shape and Motions. ^Illus.) 464 



TlOB 



Gotham's Pupil Photometer. 



{nim.) 465 



Standard of Politics in America ... 466 

 Chapters on Modem Domestic 



Economy ; The Dwelliug-House... 466 



Re\-iews 467 



Face of the Sky. By F.R.A.S 469 



Crows verifus Woodchuck 469 



Our Inventors' Column 470 



Correspondence : Doctoring "Wine 



Statistics of Barataria — Noah'a 



Rainbow, &c 471 



Our Whist Column 473 



Our Ch»3a Column 4^4 



THE CHEMISTRY OF COOKERY. 



By W. Mattieu Williams. 

 XLVIII.— THE WEAR AND TEAR OF THE BODY. 



IN the course of these papers I have repeatedly spoken of 

 the nitrogenous and non-nitrogenous constituents of 

 food, assuming that the nitrogenous are the most nutritious, 

 are the plastic or flesh-building materials; and that the 

 non-nitrogenous materials cannot build up flesh or bone or 

 nervous matter, can only supply the material of fat, and by 

 their combustion maintain the animal heat. 



In doing so I have been treading on loose ground — I 

 may say, on a scientific quicksand. When I first taught 

 practical physiology to children in Edinburgh, many years 

 ago, this part of the subject was much easier to teach than 

 now. The simple and elegant theory of Liebig was then 

 generally accepted, and appeared quite sound. 



According to this, every muscular efibrt is performed 

 at the expense of muscular tissue ; every mental effort, at 

 the expense of cerebral tissue ; and so on with all the forces 

 of life. This consumption or degradation of tissue demands 

 continual supplies of food for its renewal, and as all the 

 working organs of the animal are composed of nitrogenous 

 tissue, it is clearly necessary, according to this, that we 

 should be supplied with nitrogenous food to renew them, 

 seeing that the nitrogen of the air cannot be assimilated by 

 animals at all. 



But besides doing mechanical and mental work, the 

 animal body is continually giving out heat, and its tempera- 

 ture must be maintained. Food is also demanded for this, 

 and the non-nitrogenous food is the most readily combus- 

 tible, especially the hydro-carbons, or fats ; the carbo- 

 hydrates — starch, sugar, ic. — also, but in lower degiee. 

 These, then, were described as fuel food, or heat-producers. 



This view is strongly confirmed by a multitude of familiar 

 facts. Men, horses, and other animals cannot do con- 

 tinuous hard work without a supply of nitrogenous food ; 

 the harder the work the more they require, and the greater 

 becomes their craving for it. On the other hand, when 

 such food is eaten in large quantities by idle people, they 

 become victims of inflammatory disease, or their health 



otherwise suffers, according, probably, to whether they 

 assimilate or reject it. 



Man is a cosmopolit.tn as well as an omnivorous aoimal, 

 and the variations of his natural demand for food in 

 different climates affords very direct support to Liebig's 

 theory. Enormous quantities of hydrocarbon, in the form 

 of fat, is consumed by the Esquimaux and by Europeans 

 when they winter in the Arctic regions. They cannot live 

 there without it. In hot climates some fuel food is re- 

 quired, and the milder form of carbo-hydrates is chosen, and 

 found to be most suitable ; rice, which is mainly composed 

 of starch, is an example. Sugar, also. Offer an Esquimaux 

 a tallow candle and a rice pudding, he will reject the latter, 

 and eat the former with great relish. 



A multitude of other facts might be stated, all supportiug 

 Liebig's theory. 



There is one that just occurs to me as I write, which I 

 wUl state, as it appears to have been hitherto unnoticed. 

 Some organs which act in such wise that we can see their 

 mode of action are visibly disintegrated and consumed by 

 their own activity, and may be seen to demand the per- 

 petual renewal described by Liebig. There are certain 

 glands of cellular structure which cast off their terminal 

 cells containing the fluid they secrete ; do their work by 

 giving up their own structural substance at their periphersil 

 working surface. 



Where, then, is the quicksand ? It is here. If muscular 

 and mental work were done at the expense of the nitro- 

 genous muscular and cerebral tissues, the quantity of 

 nitrogen excreted should vary with the amount of work 

 done. This was formerly stated to be the case without 

 hesitation, as the following passage from Carpenter's 

 " Manual of Physiology " (3rd Edition, 1856, page 256) 

 shows : " Every action of the nervous and muscular 

 systems involves the death and decay of a certain amount 

 of the living tissue — as is indicated by the appearance of 

 the products of that decay in the excretions." 



More recent experiments by Fick and Wislicenus, Parkes, 

 Houghton, Kanke, Voit, Flint, and others contradict this 

 by showing that the waste nitrogen varies with the quantity 

 of nitrogenous food that is eaten, but not with the muscular 

 work done. For the details of these experiments I must 

 refer the reader to standard modern physiological treatises, 

 as a description of them would carry me too far away from 

 my immediate subject. (Dr. Pavy's "Treatise on Food" 

 has an introductory chapter on "The Dynamic Relations of 

 Food," in which this subject is clearly treated in sufiicient 

 detail for popular reading.) 



It is quite the fashion now to rely upon these later ex- 

 periments ; but, for ray own part, I am by no means 

 satisfled with them — and for this reason, that the perspira- 

 tion from the skin and the vapour from the lungs were not 

 examined. It is just these which are greatly increased by 

 exercise, and their quantity is very large, especially those 

 from tiie skin, which are threefold, viz., the insensible per- 

 spiration, which is transpired by the skin as invisible 

 vapour, the sweat, which is liquid, and the solid particles 

 of exuded cuticle. 



Lavoipier,^ and Seguin long ago made very laborious ex- 

 periments upon themselves in order to determine the 

 amount of the insensible perspiration. Seguin enclosed 

 himself in a bag of glazed taffeta, which was tied over him 

 with no other opening than a hole corresponding to his 

 mouth ; the edges of this hole were glued to his lips with 

 a mixture of turpentine and pitch. He carefully weighed 

 himself and the bag before and after his enclosure therein. 

 His own loss of weight being partly from the lungs and 

 partly from the skin, the amount gained by the bag repre- 

 sented the quantity of the latter ; the difference between 



