1911 Encyclopædia Britannica/Fat

FAT (O.E. fáett; the word is common to Teutonic languages, cf. Dutch vet, Ger. Fett, &c., and may be ultimately related to Greek πίων and πιαρός, and Sanskrit pivan), the name given to certain animal and vegetable products which are oily solids at ordinary temperatures, and are chemically distinguished as being the glyceryl esters of various fatty acids, of which the most important are stearic, palmitic, and oleic; it is to be noticed that they are non-nitrogenous. Fat is a normal constituent of animal tissue, being found even before birth; it occurs especially in the intra-muscular, the abdominal and the subcutaneous connective tissues. In the vegetable kingdom fats especially occur in the seeds and fruits, and sometimes in the roots. Physiological subjects concerned with the part played by fats in living animals are treated in the articles Connective Tissues; Nutrition; Corpulence; Metabolic Diseases. The fats are chemically similar to the fixed oils, from which they are roughly distinguished by being solids and not liquids (see Oils). While all fats have received industrial applications, foremost importance must be accorded to the fats of the domestic animals—the sheep, cow, ox and calf. These, which are extracted from the bones and skins in the first operation in the manufacture of glue, are the raw materials of the soap, candle and glycerin industries.