A contribution to our knowledge of the chemistry of coat-colour in animals and of dominant and recessive whiteness

Abstract

Our knowledge of the pigments which give rise to the coat-colour of animals is very limited, and is chiefly confined to work on the melanins, an extensive bibliography of which is to be found in a monograph by Kobert and also in a paper by von Fürth. The dark bodies which remain as a cleavage residue after the acid hydrolysis of proteins are sometimes also called melanins, as well as the artificial products formed by the action of tyrosinase upon tyrosine. Since the relationship of these substances to each other is still doubtful, it seems preferable to follow Gortner* in calling all the artificial black bodies humins, and to reserve the name melanin for the dark pigments occurring in the living organism. The origin of the pigments remained in great obscurity until Landolt suggested that melanin might be formed by a process of oxidation. But it was Bertrand's discovery among plants of tyrosinase, an oxidase capable of oxidising tyrosine to a humin, that led to the present theory. Bertrand’s discovery was confirmed by Biedermann and others who found that tyrosinase occurred among many plants and animals.