JoLY — Radio-Tlierapy : its Scientific Basis and its Teaching. 511 



we come to the cell there is not so much to differentiate the vegetable from 

 the animal. 



We see, tlien, that not only the parallel with the photo-sensitive film, but 

 also the experiments which liave been made on embryonic cells, support the 

 view that the initiation of cancer involves two factors : the presence of a 

 sensitizer which acts to increase mitosis and cell proliferation, and tlie absence 

 of a substance (the positive ion) which normally acts as a restrainer towards 

 the growth processes of the cell. The presence of the former may be harmless 

 so long as the latter exists in sufficient quantitj' to neutralize its effects. This 

 view has led us to seek for the cause of tlie increase of cancer in the increased 

 consumption of such articles of diet, notably tannin, as may introduce sensi- 

 tizing substances into the system. Reverting to tlie theory of radio-therapy, 

 we are led to tlie inference tliat in radio-active treatment we effect ionic 

 changes in the cell whicli are equivalent to increasing the amount of 

 sensitizer present. But tlie cancer cell has already within it almost the 

 limiting amount of the sensitizer which its continued metabolism permits. 

 The result of radioactive treatment is to overstep this limit and bring the 

 amount of the sensitizer up to tlie lethal concentration. The surgeon must 

 notice that on this view he is increasing the alkalinity of the cell, and, as it is 

 impossible to confine this action entirely to the tumour, excessive radioactive 

 treatment is to be avoided. The use of small multiple centres of radiation, 

 the effects of which are more easily localized and rendered uniform, is 

 preferable to strong centralized radiation where lethal effects are long 

 surpassed in one region before tlie destructive dosage is reached in another.' 



IVEAGH GeOI.OGICAL LABORATORY, 



Trinity College, Dublin. 



Note addkd in the Press. 



According to Dr. W. S. Bainbridge (" The Cancer Problem," p. 67, New 

 York, The Macmillau Co.), "cancer of lip, tongue, cheek, and buccal mucous 

 membrane is of relatively frequent occurrence in both sexes in India, in 



1 Stevenson, Brit. Med. Journ., July 4, 1914, and March 20, X915 ; Joly, Proc. Roy. Dublin 

 See, vol. xiv, May 8, 1914, p. 290. 



SOIENT. PKOC. E.D.S., VOL. XIV., NO. XXSVII. 4m 



