I had in mind calling attention to certain recent developments in cancer research. As it would be impossible, however, in the limits of this paper, to outline the advances made in so extensive a field, I shall attempt to appraise the value of certain new discoveries, without attempting sweeping generalizations, in the belief that this will prove more profitable than a more general survey of the subject.
Perhaps the more important problems in cancer research center in the so-called parasitic theory. In the past there has been intense and at some times almost bitter controversy over the tenability of this theory. To-day, however, through the discoveries of filterable viruses causing different types of sarcoma in chickens, we may assume that the parasitic hypothesis is at last justified. When it has been determined that one genuine neoplasm is caused by a viable agent or organism, those who have contended for the