426 NUTRITION 



This volatile oil is largely imported into this country, and is used for scenting soap, 

 and in perfumery. 



mrTBIEG, BUTTER OF. See Oirs. 



NUTRITION", or that process by which a living being is nourished and its 

 growth maintained, has so important a bearing upon the practical question of health, 

 that a brief exposition of the subject, especially with reference to the food of man, 

 may fairly find a place in this work. 



Every living animal organism needs a constant supply of matter from without, 

 partly to furnish materials for those chemical changes by which the forces of the 

 organism are developed, and partly to compensate for the wear and tear which the 

 structure suffers in the performance of its various functions. The quantity of matter 

 thus required in the shape of food varies in different organisms, and in the same 

 organism under different conditions ; indeed, the more work an animal performs the 

 greater its waste, and consequently the greater the amount of food which it requires. 

 It has been calculated that a full-grown man of average weight, in ordinary activity, 

 loses daily about 4,600 grains of carbon and about 300 grains of nitrogen. It is 

 clear that if the body is to remain in equilibrium, neither losing nor gaining in 

 weight, these quantities of carbon and nitrogen must be supplied from without, and 

 presented in a form available for nutrition. 



All kinds of food have been divided into two groups : those containing nitrogen, 

 and those destitute of this element. To the nitrogenous group belong all proteinaceous 

 compounds, consisting mainly of carbon, hydrogen, oxygen, and nitrogen, with more 

 or less sulphur and phosphorus. This group includes albumen, or white-of-egg ; 

 syntonin, which forms the chief constituent of muscular tissue or lean meat ; fibrin, 

 one of the derivatives of blood ; casein, obtained from cheese ; gluten, from flour ; and 

 legumin, from peas and beans. To the non-nitrogenous group belong all amylaceous 

 compounds, such as starches, sugars, and gums : these contain only carbon, hydrogen, 

 and oxygen ; and, as the hydrogen and oxygen exist in exactly the proper proportion to 

 form water, they may be appropriately called carbo-hydrates, consisting as they do of 

 carbon and the elements of water. The non-nitrogenous food-stuffs also include all 

 animal and vegetable fats and oils ; these consist, likewise, of carbon, hydrogen, and 

 oxygen, but the hydrogen is in excess of that necessary to form water with the 

 oxygen. Liebig termed the nitrogenous foods elements of nutrition or flesh-formers, 

 since he believed that they only were capable of conversion into blood, and therefore 

 of building xip the body ; whilst he characterised the non-nitrogenous principles as 

 elements of respiration or heat-givers, since he maintained that they served merely to 

 sustain the temperature of the body by the slow combustion of their carbon and 

 hydrogen by means of the atmospheric oxygen taken into the system through the 

 lungs. It is now known, however, that this sharp limitation of functions to each 

 class of foods is not strictly correct. It is true that nitrogenous compounds are abso- 

 lutely necessary to replace the nitrogen which is carried out of the system in the 

 shape of urea ; yet they may also contribute to the production of heat by oxidation 

 of part of their carbon and hydrogen. But although proteinaceous compounds are 

 thus absolutely necessary to the support of life, and may even be used alone, there are 

 strong physiological and economical reasons in favour of their due admixture with the 

 non-nitrogenous kinds of food. It should not be forgotten that it is necessary to intro- 

 duce into the diet certain mineral substances, such as common salt and the various saline 

 matters present in most animal and vegetable substances. In such a typical food 

 as milk we find the proteinaceous, saccharine, oleaginous, and mineral matters so 

 nicely balanced, that all the nutritive functions in infancy are well sustained by 

 this single article of diet. Bread and meat may also be cited as a representative 

 mixed diet; the gluten of the bread and the lean of the meat representing the 

 nitrogenous principles, and the starch of the bread and the fat of the meat being 

 non-nitrogenous, whilst mineral matters are found in both. The amount of carbon 

 and nitrogen which was previously stated to be daily excreted by a man of ordi- 

 nary activity may be replaced by a diet made up of about 2 Ibs. of bread and J Ib. 

 of meat per day. 



For further information on this subject, see Watts's ' Dictionary of Chemistry.' 



The following remarks on the law regulating the balance of the food are retained 

 from the longer article by the Lite Robert Dundas Thomson which appeared in the 

 last edition, since they place the question in a very clear light. 



During the present century a large amount of experiment has clearly demonstrated 

 that animals cannot subsist on starch, sugar, or other foods destitute of nitrogen ; and 

 therefore, the inference was fairly deduced that the animal system possessed no power 

 of assimilating nitrogen from the air (Magendie). Further consideration led to the 

 conclusion that milk constitutes the type of what nutriment should be, since it is 

 supplied for animal support by nature at the earliest period of human existence 



