y the rays send
out ss-rays; these in turn are hurled against other atomic
systems; fresh separations of electrons arise and new attractions
and repulsions spring up and the most important chemical changes
are brought about. Our mental picture can claim to be no more
than diagrammatic of the reality. Still we are here dealing with
recognised physical and chemical phenomena, and their description
as "occult" in the derogatory sense is certainly not
justifiable.

Having now briefly reviewed the nature of the rays arising in
radioactive substances and the rationale of their influence, we
must turn to more especially practical considerations.

The Table given opposite shows that radium itself is responsible
for a- and ss-rays only. It happens that

252

Period in whioh 1/2 element is transformed.

URANIUM 1 & 2 { a 6 } x 109 years.

URANIUM X { a ss } 24.6 days.

IONIUM { a 8 } x 104 years.

RADIUM { a ss } 2 x 102 years.

EMANATION { a } 8.85 days.

RADIUM A { a 8 } minutes.

RADIUM B { ss y } 26.7 minutes.

RADIUM C { a ss y } 13.5 minutes.

RADIUM D { ss } 15 years.

RADIUM E { ss y } 4.8 days.

RADIUM (Polonium) F { a } 140 days.

Table showing the successive generations of the elements of the
Uranium-radium family, the character of their radiations and
their longevity.

253

the ss-rays emitted by radium are very "soft"--_i.e._ slow and
easily absorbed. The a-ray is in no case available for more than
mere surface application. Hence we see that, contrary to what is
generally believed, radium itself is of little direct therapeutic
value. Nor is the next body in succession--the emanation, for it
gives only a-rays. In fact, to be brief, it is not till we come
to Radium B that ss-rays of a relatively high penetrative quality
are reached; and it is not till we come to Radium C that highly
penetrative y-rays are obtained.

It is around this element, Radium C, that the chief medical
importance of radioactive treatment by this family of radioactive
bodies centres. Not only are ss-rays of Radium C very penetrating,
but the y-rays are perhaps the most energetic rays of the, kind
known. Further in the list there is no very special medical
interest.

Now, how can we get a supply of this valuable element Radium C?
We can obtain it from radium itself. For even if radium has been
deprived of its emanation (which is easily done by heating it or
bringing it into solution) in a few weeks we get back the Ra