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Rh do not cure a cancer, although they are of value for the relief of pain and for the healing of cancerous ulcers. Diminution of size in cancerous growths has frequently been observed, and in some instances sarcomatous tumours have completely disappeared under X-ray treatment. Sooner or later, however, the cancer or sarcoma returns either in the original site or elsewhere, and the patient dies of the disease. It is probable that X-ray treatment is able to prolong life in a fair number of cases, and by its agency in causing a healing of ulceration in cancer cases it is able to give valuable relief both to the body and mind of the patient, and this relief may last for a year or more.

In rodent ulcer X rays are usually sufficient to provide a lasting cure, but there are some exceptions, as for instance when the rodent ulcer has been long neglected, and has spread deeply so as to invade bony structures. An important factor in the successful treatment of rodent ulcer by X rays is to continue the applications at intervals for several months after apparent cure. If this precaution is omitted there is a very great likelihood of relapse taking place later on.

In the treatment of skin diseases by X rays the method finds a very suitable field. Almost all chronic skin affections yield to X-ray treatment fairly quickly, and maximal doses are not usually necessary.

In ringworm X rays have achieved wonderful results. The rays act upon the hair papillae, and not upon the ringworm fungus. They cause a shedding of the hair fifteen days after exposure and the fungus then dies out from the hair follicles, so that when in due course the hair begins to grow again after a period of two months it grows healthily and without disease. The X-ray treatment of ringworm has been a real advance, and Sabouraud has told us of the enormous pecuniary saving which has been effected in Paris by the shortening of the stay of the ringworm cases in the special schools maintained there for the affected children.

In lupus X rays are valuable, but not fully satisfactory. The treatment by the rays will often succeed in bringing about a healing of the ulceration of lupus, but relapses are frequent, because foci of infection are apt to remain in the healed scar tissue and after a period of quiescence these may gradually provoke fresh mischief.

X-ray treatment is of service for the treatment of enlarged “strumous” glands in the neck. When these glands are in the early stages, and there has not been any softening or breaking down of the gland tissue, the application of X rays, a few times repeated in moderate doses, will determine the subsidence of the enlargement and may effect a complete cure.

In the massive glandular enlargements of lymphadenoma a great reduction of the tumours can be brought about by heavy doses of X rays, but the results are to give a symptomatic rather than a real cure, for fresh glandular growths take place internally, and the usual course of the disease is not fundamentally modified.

So too in leukemia, the symptom of excessive abundance of white cells in the circulating blood can be surprisingly altered for the better by X rays, but generally without real cure of the underlying condition. The effect appears to be due to a direct destructive action upon the leukocytes or white corpuscles of the blood.

Quite recently the use of X rays in fibroid tumours of the uterus has been advocated, particularly by Courmelles in France and Albert-Schonberg in Germany. The action of the rays seems to be in part due to their influence upon the activity of the ovaries and in part to a direct effect upon the growing fibroids themselves, causing decrease of activity, relief of symptoms and reduction of the tumours.

 XYLANDER, GUILIELMUS (, according to his own spelling) (1532-1576), German classical scholar,

was born at Augsburg on the 26th of December 1532. He studied at Tübingen, and in 1558, when in a state of abject poverty (caused, according to some, by his intemperate habits), he was appointed to succeed Micyllus (Molshem, Molseym or Molsheym) in the professorship of Greek at Heidelberg, which he exchanged for that of logic (publicus organi Aristotelii interpres) in 1562. He died at Heidelberg on the 10th of February 1576. Xylander was the author of a number of important works, among which his Latin translations of Dio Cassius (1558), Plutarch (1560-1570) and Strabo (1571) deserve special mention. He also edited (1568) the geographical lexicon of Stephanus of Byzantium; the travels of Pausanias (completed after his death by F. Sylburg, 1583); the Meditations of Marcus Aurelius (1558, the editio princeps based upon a Heidelberg MS. now lost; a second edition in 1568 with the addition of Antoninus Liberalis, Phlegon of Tralles, an unknown Apollonius, and Antigonus of Carystus—all paradoxographers); and the chronicle of George Cedrenus (1566). He translated the first six books of Euclid into German with notes, the Arithmetica of Diophantus, and the De quattuor mathematicis scientiis of Michael Psellus into Latin.  XYLENE, or , C6H4(CH3)2. Three isomeric hydrocarbons of this formula exist; they occur in the light oil fraction of the coal tar distillate, but they cannot be separated by fractional distillation owing to the closeness of their boiling points. The mixture can be separated by shaking with sulphuric acid, whereupon the ortho and meta forms are converted into soluble sulphonic acids, the para form being soluble only in concentrated acid; the ortho and meta acids may be separated by crystallization of their salts or sulphonamides. Ortho-xylene is obtained from ortho-bromtoluene, methyl iodide and sodium as a colourless mobile liquid boiling at 142°, melting at -28°, and having a specific gravity of 0.8932 at 0°. Oxidation by potassium permanganate gives phthalic acid; whilst chromic acid gives carbon dioxide and water. Meta- or iso-xylene, the most important isomer, may be prepared by nucleus-synthetic reactions, or by distilling mesitylenic acid, C6H3(CH3)2CO2H, an oxidation product of mesitylene, C6H3(CH3)3, which is produced on the condensation of acetone, with lime; this reaction is very important, for it orientates meta-compounds. It boils at 139°, melts at -54°, and has a specific gravity of 0.8812. Para-xylene is obtained when camphor is distilled with zinc chloride, but it is best prepared from para-brom-toluene or dibrombenzene, methyl iodide and sodium. Dilute nitric acid oxidizes it first to para-toluic acid and then to terephthalic acid. It boils at 138°, melts at 15°, and has a specific gravity of 0.8801 at 0°.  XYLOPHONE (Fr. xylophone; Ger. Xylophon, Strohfiedel or Holzharmonika; Ital. armonica de legno), a small instrument of percussion, of definite sonorousness, used in the orchestra to mark the rhythm. The xylophone consists of a series of little wooden staves in the form of a half cylinder and graduated in size. The staves, each of which represents a semitone, rest on two, three or four wooden bars, covered with straw and converging to form an acute angle. They are so arranged that each stave is isolated. In some models the staves are grouped in two rows, comprising the naturals and the accidentals. The xylophone is played with two little wooden hammers, and has a compass of two or three octaves. The quality of tone is inferior to that of the steel harmonica or glockenspiel.

 XYSTUS, the Greek architectural term for the covered portico of the gymnasium, in which the exercises took place during the winter or in rainy weather; this was known as the, from its polished floor (, to polish). The Romans applied the term to the garden walk in front of the porticoes, which was divided into flower beds with borders of box, and to a promenade between rows of large trees. 