Add to ORKGThe authors are generous in observing that the high degree of success achieved by (Katz\u27s δ-ray theory of track structure) in fits to survival curves for heavy ions, and in analysis and prediction of other biological effects is almost legend. We remind them that the model is physical, and has little to do with biology in an explicit way, except that an oversimplified bean bag model of a eukaryotic cell is used, in which the bag represents the cell nucleus and the beans represent internal targets. No explicit biologically mechanistic structure or response is inferred. No reference is made to DNA. The model rests on its fit to data rather than on its relationship to a presumed mechanism, however universally that presumption is held