er and more easily absorbable rays, that it has been
found necessary to stop these softer rays--both the y and ss--by
wrapping lead or platinum round the tube. In this lead or
platinum some thirty per cent. or more of the rays is absorbed
and, of course, wasted. But in the absence of the screen there is
extensive necrosis of the tissues near the tubes.

If, however, in place of one or two such tubes we use ten or
twenty, each containing one-tenth or one-twentieth of the dose,
we can avail ourselves of the softer rays around each tube with
benefit. Thus a wasteful loss is avoided. Moreover a more uniform
"illumination" of the tissues results, just as we can illuminate
a hall more uniformly by the use of many lesser centres of light
than by the use of one intense centre of radiation. Also we get
what is called "cross-radiation,"which is found to be beneficial.
The surgeon knows far better what he is doing by this method.
Thus it may be arranged for the effects to go on with approximate
uniformity throughout the tumour instead of varying rapidly
around a central point or--and this may be very important-- the
effects may be readily concentrated locally.

Finally, not the least of the benefit arises in the easy
technique of this new method. The quantities of

258

emanation employed can fit in the finest capillary glass tubing
and the hairlike tubes can in turn be placed in fine exploring
needles. There is comparatively little inconvenience to the
patient in inserting these needles, and there is the most perfect
control of the dosage in the number and strength of these tubes
and the duration of exposure.[1]

The first Radium Institute in Ireland has already done good work
for the relief of human suffering. It will have, I hope, a great
future before it, for I venture, with diffidence, to hold the
opinion, that with increased study the applications and claims of
radioactive treatment will increase.

[1] For particulars of the new technique and of some of the work
already accomplished, see papers, by Dr. Walter C. Stevenson,
_British Medical Journal_, July 4th, 1914, and March 20th, 1915.

259

SKATING [1]

IT is now many years ago since, as a student, I was present at a
college lecture delivered by a certain learned professor on the
subject of friction. At this lecture a discussion arose out of a
question addressed to our teacher: "How is it we can skate on ice
and on no other substance?"

The answer came back