A procedure analogous to the plating of bacteria is described whereby some complex tumors have been taken apart and their components separately propagated. It was the outcome of finding that the forcible injection of Locke's solution followed by air can be used to split the subcutaneous connective tissue of sucklings and weanlings horizontally over the entire expanse of their backs or bellies, without inducing any complicating inflammation. Tumor fragments suspended in Locke's were widely scattered on the surfaces thus exposed. Most of them remained where they had lodged on the body wall, and rapidly becoming fixed in place, formed growths protected by the overlying cutaneous layer—which, throughout many weeks, remained unattached either to the wall or to them.
The procedure is more searching in its disclosure of tumor constituents than those currently employed, and it has the advantage that it preserves the neoplastic components that it reveals. It has been used thus far only to rescue for experimental purposes transplantable, benign, epidermal papillomas from the hidden carcinomas deriving from their cells, and to set free and maintain the neoplastic components of complex mammary tumors of milk factor type. Success was obtained with such of the latter as were chosen for separate propagation, though successive platings were sometimes required for their isolation. Incidentally the procedure revealed two components in the mammary growths which could not have been discerned by previous methods of search. Each formed tumors peculiar to itself.