Aqueous. Water is required not only as the medium of conveying the other substances into the body, but it forms a prominent constituent of the body itself. Blood contains 790 parts of water to 210 of solid matter in every 1000. Muscles contain 770 parts of water to 230 solid ingredients. The brain and nerves contain about 800 parts of water in 1000. If food does not contain water naturally, it is taken into the system in the form of tea, coffee, beer, and also in its pure state. The quantity of water taken with the food should be about in the proportion of four to one, as we find it in milk. We cannot, however, judge of the quantity contained in solid food till we know its composition. Thus many substances which appear solid contain large quantities of water. In potatoes, for instance, there are 75 parts of water in every 100 parts.