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1-14 with 0.025 c.c., mice 15-28 with 0.15 c.c. Higher percentage and more rapidly growing tumours with the larger dose.

11-19 0.05 cc., and 20-31 0·1 cc. The sizes attained by the tumours in ten days, and their subsequent rates of growth are progressively greater with increased initial dose (cf. exp. JRS/10 A and exp. 32/23 E. Exp. J/102 C (fig. 22) shows a different result. The disposition of the experiment is the same, but while tumours appeared and grew in the mice with the smallest and the largest doses, only one small slow growing tumour was obtained in the group inoculated with the medium dose (0.05 cc., 11-19). These phenomena will be discussed on a later page. They are probably due to the quantitative relations between the dose of tumour and the reaction of the animals, and to concomitant immunization which was not effective in the small dose, was effective and not overcome by the medium dose and overcome by the large dose. The contrast between the behaviour of tumours 32 and Jensen at different times, with respect to the effects of variations in the dose of material inoculated, can only mean that the cells are biologically different at different times. The phenomenon is also seen in similar experiments with most other transplantable tumours. It is important to note that the experimental sarcoma developed during the propagation of tumour 37, exhibits it also, in contrast with Jensen's rat sarcoma, which in our experience does not. At times large doses give a higher percentage of more rapidly growing tumours than small doses, at others the initial proliferation from large doses is followed by spontaneous absorption. The transplantable chondro-osteo-sarcoma (tumour 92) behaves in the

same way.

(7) Effect of Concomitant Immunization and of Alternations
in Tumour Cells.

The effect of absorption of tumour-tissue concomitantly with the initiation of growth after inoculation is manifested not less clearly, though to a slighter degree, and in another way, in practically every graphic record. This particular effect must be discussed here, because of its important bearing on the interpretation of percentage-curves and graphic records of growth, as an analysis of cancerous proliferation. It will not have escaped notice that in most series of inoculations of which illustrations have been given, a number of animals occur in which temporary proliferation is followed rapidly by absorption of the tumour nodules. This phenomenon is a feature of all propagable tumours

*This temporary proliferation is quite different from the phenomenon described and figured in detail by Bashford, Murray and Cramer in the Second Scientific Report as natural healing of a large tumour, and recorded independently by Clowes.

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