摘要：

Laboratory studies of cancer spread should enable us to define the natural history of cancer exactly. The vast body of research into this biological phenomenon, both on cells cultured in vitro and in vivo, that is on grafted animal tumours, induced or spontaneous, and on experimental models, has contributed valuable information, but there are such variations by tumour type, animal species, cell environment and experimental technique that it is difficult to extrapolate the data to cancer in man.

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