[15] “It is _health_ rather than _strength_ that is the great requirement of modern men at modern occupations; it is not the power to travel great distances, carry great burdens, lift great weights, or overcome great material obstructions; it is simply that condition of body, and that amount of vital capacity, which shall enable each man in his place to pursue his calling, and work on in his working life, with the greatest amount of comfort to himself and usefulness to his fellowmen.”—Maclaren’s _Physical Education_. [16] To this classification may be added what are called albuminoids, a group of bodies resembling proteids, but having in some respects a different nutritive value. Gelatine, such as is found in soups or table gelatine is a familiar example of the albuminoids. They are not found to any important extent in our raw foods, and do not therefore usually appear in the analyses of the composition of foods. The albuminoids closely resemble the proteids, but cannot be used like them to build up protoplasm. [17] The amount of water in various tissues of the body is given by the following table in parts of 1000: Solids. Liquids. Enamel, 2 Blood, 791 Dentine, 100 Bile, 864 Bone, 486 Blood plasma, 901 Fat, 299 Chyle, 928 Cartilage, 550 Lymph, 958 Liver, 693 Serum, 959 Skin, 720 Gastric juice, 973 Brain, 750 Tears, 982 Muscle, 757 Saliva, 995 Spleen, 758 Sweat, 995 Kidney, 827 Vitreous humor, 987 [18] The work of some kinds of moulds may be apparent to the eye, as in the growths that form on old leather and stale bread and cheese. That of others goes on unseen, as when acids are formed in stewed fruits. Concerning the work of the different kinds of moulds. Troussart says: “_Mucor mucedo_ devours our preserves; _Ascophora mucedo_ turns our bread mouldy; _Molinia_ is nourished at the expense of our fruits; _Mucor herbarium_ destroys the herbarium of the botanist; and _Choetonium chartatum_ develops itself on paper, on the insides of books and on their bindings, when they come in contact with a damp wall.”—Troussart’s _Microbes, Ferments, and Moulds_. [19] “The physiological wear of the organism is constantly being repaired by the blood; but in order to keep the great nutritive fluid from becoming impoverished, the matters which it is constantly losing must be supplied from some source out of the body, and this necessitates the ingestion of articles which are known as food.”—Flint’s _Text-book of Human Physiology_.