Moreover, the X-rays have a double value in medicine. In the first place, they are used as an aid to diagnosis, forming those branches of radiotherapy known as radioscopy and radiography. Then they are also used to great advantage in the alleviation or cure of certain maladies. By means of radioscopic or radiographic examination it may be found that there is a tumor in the chest, and as a result of that diagnosis it may be decided to institute treatment (radiotherapy) by means of X-rays or radium rays or the two combined. The method of employing extremely penetrating X-rays—under high voltage and amperage—seems to have been first used in Germany, during the World War, but was soon developed to a high degree of efficiency in France, England, and the United States, especially by Dr. William Duane, professor of biophysics at Harvard. As early as 1919, Professor Dessauer, in Germany, produced the penetrating X-rays by means of a high-tension current ranging from 170,000 to 240,000 volts. It was later found, that rays at 200,000 volts became homogeneous, so that a further increase was considered as of no therapeutic value. In March, 1923, Dr. I. Seth Hirsch, head of the X-ray department of the Bellevue Hospital in New York, gave a drastic treatment—for cancer—of four periods of 16 hours each with the X-rays at 250,000 volts, apparently with satisfactory results. The patient suffered no pain or inconvenience during the treatment with the exception of occasional nausea. A year later an experiment was made in a Philadelphia laboratory where an X-ray treatment of 300,000 volts was used. It seems that alleviation rather than cure has been the result of nearly all cases where cancer had been well advanced. Other important improvements, meanwhile, were being introduced by the German specialists, during the World War and later, among which was the just mentioned method of giving large tissue-destroying doses, requiring from ten to 15 hours; to this was added careful filtration of the rays, and the invention of the _ionto_—a quantimeter for exact measurements. A number of malignant diseases is reported to have yielded to this new system of massive doses under higher voltage. But Professor Duane has stated that neither X-rays nor the gamma rays of radium should be considered as a permanent cure for cancer. Until recently the tubes in which X-rays are produced have always been made of glass. The latest discovery is a tube made of fused silica, or vitreosil. Vitreosil permits the passage of the short rays, will stand a much higher temperature than glass, and is much stronger. This means more continuous service from X-rays.