Artificial Production of Coat Colour in the Albino Rat: Its Relation to Pattern in the Growth of Hair

Abstract

DURING experiments on growth, which were designed to test the action of a series of flavins, a hitherto undescribed property was encountered in one of these compounds (9-phenyl-5: 6-benzo-iso-alloxazine¹), the structure of which is shown in Fig. 1. Quite unexpectedly, injection of 20–30 mgm. of this substance, in albino rats, produced an orange-yellow pigmentation of the hair. It was then observed that the coloration so produced is usually restricted to certain areas of the coat, in a way which varies considerably from one rat to another, but nevertheless conforms to a characteristic type of pattern (Fig. 2), of which the most striking feature is a pronounced degree of symmetry about the longitudinal axis. Study of some scores of similarly injected rats from the same albino colony soon revealed the regular recurrence of pattern types, which it was comparatively easy to arrange as a roughly transitional series: these facts conveyed a strong impression of a certain unity of design, in which each individual represents only one stage in a continuous rhythmic process. That the pattern which may be elicited in individual animals is variable was proved by administration of the compound at intervals of one to three weeks, fresh zones of colour appearing in response to each such injection: hence its form depends (in the majority of cases at least) upon a fluctuating process, and not upon one which is fixed, or pre-determined, genetically or otherwise.