This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
Animal foods contain much nutritive matter in a more or less concentrated form which exists in practically the same chemical combination with the body itself. They leave comparatively little residue, being quite thoroughly digested. They are agreeable in flavour, and they hold salts, including iron, which are of special value as force producers. They are, however, inferior to starches in this property unless much fat be incorporated with them.