The chemical nature of amyloid, as well as the mechanism of its formation, has been very obscure. Experimental investigation of the problem has until recently encountered the difficulty that amyloid could not regularly be produced in animals. Thanks to the work of Kuczinski, Jaffé, Letterer and others, this difficulty no longer exists. By parenteral injection of sodium caseinate and various other proteins and non-protein substances, as well as by feeding excessive amounts of protein, amyloidosis is produced in mice in the majority of those animals. In the course of the work of these investigators, certain observations have been made that greatly increase the interest of the problem of amyloid disease. In experimental amyloidosis as well as in the spontaneous condition as it occurs in man, excessive breakdown of tissue proteins is known to take place. There is evidence that this is followed by an increased production of serum globulin, which apparently acts as the mother substance of amyloid. It has been stated that on further injection of casein or other substances employed, globulin is precipitated in the tissues in altered form and that the resulting deposits constitute amyloid. The well recognized close relation of globulin to antibodies suggests that the whole process of amyloid formation is akin to an immunological reaction. This suggestion is at least worth testing, since, if true, experimental production of amyloid would be a most useful method in studying the mechanism of certain immunological reactions, having the unique advantage of producing easily recognizable and characteristic morphological changes. The best line of attack appears to be study of changes in blood chemistry during the course of production of amyloidosis. For this purpose an animal larger than the mouse is highly desirable. Guinea pigs and rabbits have, in the hands of other workers, given negative results. The rat was, therefore, selected as a possibly suitable animal.