Further evidence concerning the significance of nuclear inclusions as indicators of a transmissable agent.

In 1920 Jackson 1 reported the occurrence of what she described as a protozoan infection of the ducts of the salivary glands of guinea pigs. “Round oval, encysted organisms” were found lying in the duct cells of 54 per cent of the guinea pigs examined by this author. Jackson concluded that these structures represented the vegetative cycle of an intracellular protozoan, probably belonging to the group of coccidia.

In 1921 Goodpasture and Talbot 2 confirmed Jackson's findings. These authors found a striking resemblance between the structures described by Jackson and certain protozoan-like cells found by them in the lung, liver and kidney of a two months old baby. The occurrence of cells of this type in infants had been previously described by several observers, the majority of whom had considered these structures to be protozoan parasites. Goodpasture and Talbot, however, were of the opinion that neither the protozoan-like cells observed in infants, nor the structures in the ducts of the sub-maxillary glands of guinea pigs described by Jackson, were protozoa. They concluded that all these peculiar cells arise through the metamorphosis of certain tissue cells. They showed that the first evidence of this transformation consisted in the appearance of acidophilic intranuclear inclusions and drew attention to Tyzzer's 3 observations of similar nuclear inclusion bodies occurring in the cells of the cutaneous lesions of varicella.

Von Glahn and Pappenheimer 4 in 1925 reported the occurrence of cells similar to those observed in infants in the viscera of an adult man, and thought that the large inclusion bodies were identical in morphology and staining reactions with the inclusion bodies described by E. Lipschütz 5 , and others, in spontaneous and experimental herpes simplex.