A MANUAL OF PRACTICAL X-RAY WORK by DAVID ARTHUR, M.D., D.P.H.

INTRODUCTORY

To one already acquainted with radiology it matters little in what sequence we consider its various factors or problems.  He will seek out for himself the parts in which he may be  specially interested, or the points on which he may desire enlightenment.

As a general plan of the work, we have thought lit to begin by considering the immediate production of X rays; next to consider the remoter means of their production; then to proceed to the discussion of their practical uses. For the benefit of those who have not previously studied the subject, we have sketched the following brief introductory note on the evolution of the X-ray tube. Like so many other processes utilised by the medical profession, radiology is based on the results of painstaking research in pure science—research initially remote from any suggestion of therapeutic issue.

The present X-ray tube has been evolved from the older Oeissler or vacuum tube. In the latter, when the pressure is reduced slightly, the resistance to electric discharge is lessened, and discharge takes place through the tube with striking phenomena of illumination, depending in character on the degree of exhaustion. The chemical nature of the residual gas also affects the character of the illumination; but we are concerned only with the presence of ordinary air.

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