Abnormal pigmentation of the body, as well as the appearance of unusual pigments in the fluids and secretions of the organism, has always elicited the interest of physicians. In recent years a new appreciation of the significance of some of these manifestations has come through the recognition that certain ingested pigments, notably the so-called carotinoids, are easily incorporated into the tissues. Under the general designation of "lipochromes" they have been recognized as the coloring matters of milk fats and body fats, of egg yolk, of the corpus luteum, and of other structures. Recently the lipochrome of nerve cells has also been identified as carotinoid coloring matter—carotin and xanthophyll pigments—derived from the food.
Through numerous researches of Palmer and his associates1 in this country, it has become known that differentspecies vary in their tendency to carry carotinoids in the blood serum. Man represents one of those capable of such distribution