The nature of the thermostable extracts from the tissues of T. equiperdum infected animals appears at least to be a co-mingled protein, even though a large portion of it may be carbohydrate.
The extracts of the tissues of the organs that are more active in hemotopoiesis and hemoclasis contain the greatest amount of the thermo-precipitinogenic substance.
The extracts of the spleen and lymph node of young offspring of infected guinea pigs' mothers give a positive reaction while the bone and marrow and heart muscle extracts give negative results.
The titer of immune sera from infected rabbits was higher than from other infected laboratory animals tested. This varied, however, with the virulence of the strain of the organism and the degree of spleen response as shown by development.