- 31 the chromosomal structural changes which characterize a malignant cell must be brought about by alpha interactions and not by low In this connection, the determination intensity X-rays or y-rays. of the nature of the structural differences between the healthy and the malignant cells of each organ could shed some light on this important question." Comments: The first sentence of this paragraph indicates that the paragraph will present "several other lines of evidencé which reinforce the possibility that alpha interactions with cells play a unique role in human cancer production." If the author intends that the word “unique” be used in the strict sense of the word, e.g. single or sole, it should be pointed out that no type of radiation effect has been observed which cannot be caused by otheragents or conditions, and that no type of effect of alpha radiation has been observed that cannot be caused by other kinds of ionizing radiations. The differences between effects of various types of fonizing radiations are quantitative rather than qualitative, and are owing to diterences in relative biological effectiveness, LET, distribution, etc. The next two sentences in the paragraph refer to observations of high concentration of alpha activity et sites of cancer. In regard to bronchial cancer sites, the suthor refers to a paper on distribution of polonium in pulmonary tissues ot cigarette smokers. In regard to cancer sites in the lymphatic system, the author refers to a paper entitled, "Only vertebrates with a lymvhatic system are subject to malignant disease,” and to a note to the Health Physics Journal, entitled, "The lymphatic system--a storehouse of long-stay deposits of inhaled radioactive particles." The author's references to anomalously