The action of both these methods of treatment is in essence the same. It has been found that X-rays and radium have the power of destroying living tissue when such is exposed to their action for varying lengths of time. Fortunately, cancerous tissue is destroyed before normal healthy tissue, and it is the aim of the treatment to expose the growth to that dosage of rays which will kill the malignant tissue but just fall short of doing harm to the normal tissue. Sometimes this is more easily done with X-rays and sometimes with radium; it all depends on the position of the growth. This all sounds very attractive, and one would think that, on the surface of things, with such a weapon at our disposal, every case could easily be efficiently dealt with. But, like many other superficially attractive things, it is found on further examination to have its drawbacks. Although a proper dose of X-rays will kill cancer tissue, a smaller dose will stimulate it to further action. Further, these rays have, comparatively speaking, a very low penetrating power. They are absorbed and rendered inactive by thin layers of metal, of skin or of other tissue. Now, as has already been explained, a malignant growth, as well as extending superficially, tends to spread very deeply and also to involve neighbouring structures, and when X-rays or radium are applied to it, we find that in some cases it will deal with the more superficial parts of the growth but leave the deeper parts untouched, or even more active than before. All kinds of methods have been tried to get over this, such as burying radium in the substance of the growth, and using very big doses, applied to various aspects of the growth, but, so far, although there have been some very encouraging results, the problem has not been solved. As has been said, it is extremely difficult to estimate the exact value of this treatment, as no figures are of any value till _seven years_ at least have elapsed after treatment, and no such figures have been published. There can be no doubt, however, that an occasional case has been cured, but it is the experience of all that the results of radium treatment do not approximate in any way to the percentage of cures obtained by surgery, even in those types of cancer which react best to X-rays or radium. Dr Knox, of the Cancer Hospital, London, who has had much experience of high tension X-rays, says that the treatment of malignant disease by X-rays has not yet reached that stage where it ought to be given to any operable case instead of an operation. I think this opinion may be regarded as an authoritative statement of the situation as it is at present.