Since Borrel (1906) pointed out the relationship between Cysticercus fasciolaris and sarcoma of the rat liver ( l ) , several investigators have reported one or more cases of Cysticcrcus sarcoma. In July 1920, the first experimentally produced Gysticercics sarcoma was observed by Bullock and Curtis ( 2 ) . This and 67 others were observed in rats purchased from several breeders, each of whom had for some time supplied the laboratory with rats from his own colony. Pregnant females from each of

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... ese stocks were isolated, and their progeny formed the "foundation stock" with which a pedigreed colony was started. At the beginning of the present analysis (June 1932) 52,223 animals from completed matings had been autopsied. Of these, 26,172 were infested with the parasite, 13,120 survived infestation for at least eight months (the minimum period of infestation observed in the case of a bearer of a Cysticercus sarcoma), and 3,285 had Cysticercus sarcoma. Besides these, 316 unpedigreed descendants of the purchased animals had the malignant complication of the Cysticercus disease. The authors (3) have recently published a brief statement of some of the major facts shown by this investigation. During the twelve years covered by the present analysk most of the Taenia eggs used to infest the rats were derived from 27 cats maintained at the laboratory, 6 of which were already infested when brought in from various parts of the city and suburbs. The other 21 were infested in the laboratory by feeding them Taenia larvae from the livers of infested rats. On a few occasions, eggs were obtained from the feces of catR riot brought to the laboratory. Taennia eggs from all of these soiirceB were effective in producing Cysticercus disease and its malignant complication. The Taenia eggs are obtained by centrifuging an aqueous 811spension of feces of an infested cat, and an aqueous dilution of this sediment is fed by mouth with a pipette. The number of eggs fed is estimated by counting a drop of the suspension. The shells of the eggs are digested in the rat's intestine and the oncospheres attach themselves to the wall of the intestine, mork their way into 894