Liebig's Letters on Chemistry. 



Letter 25- Hopeful prospects of Physiological Sci- 

 ence if pursued inductively; Mutual relation of natural 

 laws ; Pliysicaland Chemical ; Variation of the density and 

 boihng points of liquids accord inp; to the variations in their 

 composition ; Examples ; Relation of Specific Heat to Com- 

 position ; and to the velocity of sound in gases ; Eelation 

 of Electric Currents to Magnetism, Heat, Cnemical Action, 



&c. ; Vital properties related to other 



Progress of Anatomical Physiology ; Anatomy studif 



ithe 



Their true meaning. 

 Letter 26.— Nutritive Substances strictly so called ; 



Respiratory Food ; The Oxygen absorbed in the Lungs is 

 entirely given out in combination with Carbon and Hydro 

 gen ; Amount of Carbon daily consumed by an Adult ; 

 Amount of Oxigen required to convert it into Carbonic 

 Acid ; Respiration. 



Letter 27.— Animal Heat derived from the Oxidation 



of Carbon and Hydrogen in the Body; The Food is Burned 

 in the Body, as Fuel in a Furnace ; Effects of External 

 Cooling on the amount of Food required to keep up the 

 He;it of the Body ; A Starving Man soon yields to Cold ; 

 Clothing compensates to a certain extent for Food ; Effects 

 of Starvation, the Body rapidly Oxidised and Consumed; 

 Analogous Phenomena in Disease , The Solid and Liquid 

 Kxcreta are not Putrescent, but partially Oxidised, and 

 repiesent the Soot, Smoke, and Ashes of a Furnace; 

 Compensating Action of Organs, Kidneys and Intestines, 

 Lungs and Liver; Respiration i^ the Moving Spring. 

 Letter 28.— Effects of Respiration on the Inspired Air ; 



General and Pulmonary Circulation ; Composition of Ex- 



fired Air; Gases absorbed and given out by the Blood; 

 'rocess of Respiration ; True Cause of Death from breath- 

 ing Expired Air; Importance of Veatilation ; Quicklime 

 may be used as a substitute; One- tenth to One-fourth of 

 the Inspired Oxygen combines with Hydrogen ; The calcu- 

 lated amount of Heat from the combustion of the known 

 ■weight o^Carbon, and Hydrogen, out of the Body, agrees 

 closely with that obtained by their Oxidation in the Body. 

 Letter 29.- Nutritions or Plastic Food; The Blood; 



its fibrine, globules, and albumen; Its ashes, they contain 

 iron; importance of Albumen, as in the Fg?, it is the 

 f.iundation of all the Tissues ; Fibtine and Albumen, Flesh 

 and Blood, are the same in Composition ; Muscular Fibre, 

 convertible into Albumen, even out of the Body; Milk; 

 Caseine; Its relation to Albumen and Fibrine; Nutrition 

 of Carnivora, and of the Suckling Mammalia; of Gramini- 

 voraand Herbivora. essentially the same; Composition of 

 their Food; Vegetable Albumen, Fibrine. and Caseine 

 identical with the corresponding Animal Substances; 

 Vegetables produce the Food of Animals; Animals destroy 

 this Food, and return it to tiie Air and Soil, as Carbonic 

 Acid, Water, Ammonia, and Salts, to seri-e again as Food 

 for Plants; Products of the Oxidation of Albumen, &c. ; 

 I'lastic.or Nitrogenous, or Sanguigenous elements of food, 

 can alone form Tissues; The Non-nitrogenous, or Respira 

 tory elements of food, such as Fat, have not this property ; 

 and Fat and Water in Tissues, are only mechanically ab- 



LvTTRR 30.— Respiratory Food ; Fat, Butter, Sugar of 



Milk; Starch, Cane-sugar, Grape sugar, &c. ; Sugar of 

 Milk; Its Properties, oxidisable in presence of Alkalies, 

 undergoes the I.actic Fermentation in contact with Caseine, 

 is identical in composition with Grape-sugar; Starch, its 

 Varieties, convertible into Dextrine and Grape-sugar; 

 Table of the Relative Proportions of the Plastic to the Non- 

 nitrosenous Constit lents in difierent Articles of Food; 

 West Proportion supplied by Nature in Milk and Grain, or 

 in some kinds of Flesh; Popular Mixtures, such as Beans 

 and Bacon, Peas and Pork, Potatoes and Meat. &c., give 

 good Proportions which have been indicated by the instinct ; 

 Alcohol as a Respiratory Element of Food ; Relation of 

 F'ood to Work performed ; Rations of Labouring Men, 

 Soldiers, &c ; Feeding of Stock, Fattening; The Plastic 

 Matters do not contribute to the Animal Heat ; Functions 

 of Sugar,&c.; Accumulation of Fat. its Origin from Sugar; 

 Table of the Comparative Value of Fat, Starch, Sugar, 

 Alcohol, and Flesh, in regard to the Heat derived from 

 them in the Body ; Proportion of Nitrogen to Carbon in 

 the Tissues and Excreta. 



Letter 31.— Essential Importance of the Mineral or 



Incombustible Elements of Food ; The Ashes of Vegetable 

 Food are the same as those of Blood and 1- lesh ; The Blood 

 invariably Alkaline, and this is a Condition essential to its 

 Fluidity and to all its Functions ; The Alkaline Salt is the 

 Phosphate of Soda, wlule in all the Tissues, and in the 

 Juice of Flesh, the Phosphoric Acid is in excess, but in 

 Herbivora the Phosphate is partly replaced by another 

 Alkaline Salt, the Carbonate of Soda; A knowledge of the 

 Ashes of the Food enables us to predict the pncise Salts in 

 the Blood, the Urine, and the solid Excreta ; X lie soluble 

 Salts are found in the Urine, the insoluble in the Fwces ; 

 Relations of the Salts of the Blood to the Secretions and 

 Excretions; Table of the Urine with Animal Food and with 

 VegeUble Food; In Disease, the Analysis of the Ashes of 



Urine and Blood will become a valuable aid to the Physi- 

 cian ; The Alkalinity of the Blood essential to the Oxida- 

 tion of the Respiratory Food, and of the Products 

 of the change of Matter, such as Uric Acid, which, 

 although formed, never reaches the Kidneys in the Herbi- 

 vora, whose Urine is Alkaline ; Salts of Vegetable Acids, in 

 the Body, become Carbonates; The Excretion of the free 

 Acids in the Urine of Carnivora is essential to preserve the 

 Alkahnity of their Blood ; The Nature of the Blood and of 

 the Urine may be changed by Diet; Iron in the Fo»d, essen- 

 tial to the Blood ; Functions of common Salt, in the Food 

 and in the Blood ; Experiments on its use, and suggestions 

 on this point; Endosmosis of Saline Solutions; Effects of 

 drinking Spring Water, and Solution of Salt ; Salt a neces- 

 sary of Life. 



Letter 32.— VegetaWe and Animal Food; Composi- 

 tion of Flesh, its Fibrine, Albumen, &c. ; Proper mode of 

 boiling and roasting Meat, and of making Soup ; Constit- 

 uents of watery Extract of Flesh ; Kreatine, Kreatinine, 

 &c. ; Value of Soup and of Flesh as Food ; Importance of true 

 Extract of Flesh for Hospitals, Armies, &c. ; Portable Soup 

 of Commerce was chiefly Gelatine, which has no Nutritive 

 value; Directions for making pure Extract of Meat; Its 

 great value depends on its Inorganic Salts ; The loss of 

 Nutritive value in Salted .Meat depends on the Expulsion of 

 a great part of the juice ; Different kinds of Meat differ in 

 Nutritive value ; Veal inferior to Beef, and why ; Import- 

 ance of Iron ; Cheese, Fish, Salted Fish, Eggs, are all defi- 

 cient in Alkalies and Iron ; This is probably the reason 

 why they are admitted in fasting ; Table of the relative 

 proportion of Nitrogen and Carbon in Animal Substances, 

 from Albumen to Urea; Chemical relations of Albumen, 

 Fibrine, Caseine, Gelatine, Chondrine, Bile, and Urine ; 

 Table of the formulae deduced from analyses alone ; Illus- 

 trations of their derivation one from the other ; Grinding of 

 Grain; Flour and Bran; Brown Bread of the entire flour 

 preferable to White Bread from bolted flour; Rye Bread ; 

 Adulterations of Bread, Blue Vitriol, Alum, Lime-water, 

 should be used instead ; Baking;; Yeastpreferable to Carbo- 

 nate of Soda and Muriatic Acid ; Substitutes for Bread in 

 times of scarcity are either merely local or else fallacious ; 

 The only true gain would be to save what is thrown away 

 on the Bran, and the Gluten wasted in starch manufacto- 

 ries; Superior digestibilitv of Bread from the entire Meal, 

 or the Pumpernickel of frestphalia ; The Culinary Art is 

 empirically far advanced ; Food for different Ages ; Effects 

 of Vegetable and Animal Diet ; Value of Wine ; The abuse 

 of Spirits not so much the cause as the effect of Poverty; 

 Total- abstainers eat very much more than wine-drinkers; 

 Uses of Tea, Coffee, Chocolate. &c. ; Theine, or Caffeine, 

 compared to KreatitA and Sugar of Gelatine ; Mineral 

 elements of Tea, &c ; Price of Meat in years of scarcity, 

 and of Bread; Men living on Meat must eat a great deal, 

 and take violent exercise ; Importance of Agriculture com- 

 pared with Hunting by an Indian Chief; Science teaches 

 the economy of force ; Tendency of riches to inequality of 

 distribution, and thence to universal circulation ; Money, 

 in the organism of the State, compared to the blood cor- 

 puscles in the body, by the circulation of which the change 

 of matter is effected, and life kept up ; All human actions, 

 as is proved by the statistics of births, deaths, crimes, and 

 justice, are under strict natural laws; True science ascer- 

 tains these laws, and teaches men to observe them. 



Letter 33.— Organic Life in the Ocean ; The Water 

 jields Sea-plants all their elements ; Function of the Soil 

 in Veget.ition ; to furnish the Mineral elements to Plants; 

 The Soil IS exhausted if the Minerals removed by Crops 

 are not restored by Animal manures, bone, earth, c&c ; 

 Causes of the luxuriant growth of Tropical Plants ; Peren- 

 nial Plants and Trees require less Mineral food thin 

 Annuals; Explanation of the Effects of Drought on the 

 lower leaves of Plants 



Lett I' r 34.— Agriculture is both a Science and an Art ; 

 Its Objects ; Effects of fallowing, and of the Mechanical 

 Operations of Agriculture. 



Lftter 3.5.— Importance of Alkalies and Silica; Na- 

 tural Silicates in Soil difficult of decomposition ; In Fal- 

 lows these are decomposed by the action of the Air ; Quick- 

 lime effects the same object ; Effects of burning Clay. 



Letter 36.— Manures; Origin of Animal Manures; 

 The Excreta contains the salts of the Food, the soluble are 

 in the Urine, tiie insoluble in the Dung ; The same Salts 

 ( Phosphates, &c.) from other sources are equally efficacious ; 

 Theory of Manures ; The true Problem is to restore to the 

 Soil all we remove from it ; The Excreta of an Animal fed 

 on any Crop must be the best Manure for that Crop ; Note 

 on the Author's experience and on Mineral Manures 



Appendix.— Historvot the boy with the Golden Tooth ; 

 Letter of Gahlto to Madama Christina, Granduchessa 

 Madre ; Crum's soluble Alumina; Cause of Puerperal 

 Fever in the Lying in Hospital at Vienna ; The Flesh of 

 animals tortured to death dangerous as Food ; Local Causes 

 of Intermittent Fever ; Reported case of Spontaneous 

 Combustion, letters of Regnault, Pelouze, and Carller on 

 the subject; New Estimation of the Quantity of Blood in 

 Man by Bischoff, Estimation of the food consumed by 

 working miners at the elevated mines at Gastein and 

 Kauris ; A new soup for Invalids ; a metliod for improving 

 the quality of Bread ; To bake bread from Sprouted Grain ; 

 Legends of the Rhinegau. 



London : WALTON & MABERLY, Upper Gowcr Street, and Ivy Lane, 

 Paternoster Kow. 



