The fats: A story of nature's art

Abstract The fatty acids that constitute the glycerides of natural fats are, over wide ranges of biological species, remarkably uniform in kind, although the particular acids vary in fats of different biological origin, e.g. those of land flora, those of land fauna and those of aquatic origin. Concurrently with this very marked regularity in qualitative composition, striking although rare exceptions occur, in all sections of natural fats, in which the fat of a single family, and even of a single species of a family, consists largely of an acid which is uniquely different from any of the more prevalent and characteristic acids. The overwhelming preponderance of natural fats that contain only a few specific mixtures of component acids is contrasted with the much less frequent and apparently erratic instances in which quite exceptional acids are to be observed. The composition of the mixed glycerides, as shown by many examples in which a natural fat has been studied by the modern method of preliminary segregation into relatively simple mixtures of mixed glycerides by intensive crystallization from solvents at low temperatures, is much more regular. Each acid behaves in exactly the same way and as an individual, with the result that it tends to be distributed as evenly or widely as possible among all the glyceride molecules. Exceptions to this generalization occur only in a very few seed fats, and in certain animal body and milk fats (chiefly those of ruminant animals).