Hooded rats react to intracutaneous injections of complete Freund's adjuvant with an adjuvant disease, which is externally perceivable by massive polyarthritis, by skin and ear nodules, and by other known symptoms. In contrast to Wistar rats, however, they show no tendency to develop clinically or histologically provable eye manifestations such as an uveitis anterior (adjuvant uveitis). This fact has been connected with the genetic differences between the two strains of rats.