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GENERAL RESULTS OF PROPAGATION OF

MALIGNANT NEW GROWTHS.

By E. F. BASHFORD, M.D., J. A. MURRAY, M.B., B.Sc., M. HAALAND, AND W. H. BOWEN, M.S., F.R.C.S.

(1) Practical Value of Propagation.

The experimental investigation of cancer has now passed from the preliminary stage of having successfully achieved the transference of malignant new growths from one animal to another and elucidated the process of transmission. It now concerns itself with the biology of the cancer cell and the relations of malignant new growths to their hosts during continued propagation. We have now studied the processes of successful transference of seventy distinct tumours, forty of which continue under propagation at the present time. Their investigation has fully confirmed the conclusions advanced in the First and Second Scientific Reports as to the nature and significance of the process. These results have now received general recognition, and need not be detailed beyond repeating that the experimental reproduction of the lesions of cancer in sound animals occurs only under conditions rendering it highly improbable that the disease is usually, or even occasionally, communicated from one living being to another. The experimental communication of cancer is only possible by implantation and continued growth of living cells, and this form of transmission is certainly not the cause of the frequency of cancer, either in human beings or in mice, even if it be conceded that under exceptional circumstances, a possibility for its occurrence is presented.

The attainment of one of the primary objects of the experimental study of cancer permits of conclusions which, while of a negative order, are of great importance. It is of great practical value that the results. of experiment re-enforce opinions often expressed for other reasons.

The public can be assured with greater certainty than hitherto that the presence of some 50,000 persons suffering from cancer in England and Wales does not constitute a direct menace to the health of those near and dear to them or to the health of the population generally. Notwithstanding what unwise enthusiasts may assert from time to time, what was a justifiable cause of public alarm has been removed by experiments on the transference of cancer and the housing of large numbers of cancerous with sound animals over a period of six years, i. e., more than double the span of life in the mouse, the animal on which most of the observations have been made.

Thereafter, the experimental transference of cancer dropped into the position of an item in laboratory routine, a mere preliminary procedure to most of the investigations which it renders possible, and here results of a positive order and of constructive value have already been elicited.

Just as the culture of bacteria is a necessary routine procedure in most bacteriological researches, so is that of the cancer cell in cancer research. But there are fundamental differences between the two. The propagation of cancer is not a mere cultivation of cancer cells, comparable to a culture of bacteria. The cancer cells only grow as a tissue and by becoming part and parcel as it were of a living animal. This greatly complicates the labour involved and the procedure necessary in propagation. The cancer cell will only grow in a satisfactory manner in the living animal, and only in animals of the species from which it was derived. Thus the "in vitro" cultures obtained by the bacteriologist are replaced by "in vivo" cultures in the case of cancer, and thousands of living mice take the place of thousands of test-tube experiments. The phenomenon of the apparently unlimited propagation of the cancer cell merits study in itself, as a biological phenomenon. Its investigation has clearly revealed features of cancer which are of fundamental importance for understanding the nature of the disease and of spontaneous or natural recovery from it, but which had not been recognised because they are obscured by complications in the course of the disease in man.

Although the observations which follow are of great importance in determining the technique of propagation, and in all questions of immunity, they will be regarded in this paper principally from the standpoint of their bearing on the biology of the cancer cell, and on the analysis of the proliferation which it exhibits during artificial propagation.