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R a d i u m 149
and six hours. Now in the above experiment we were using the radium
practically unfiltercd, getting the full effect of the beta rays as well as
the gamma rays. Since the volume of beta rays giver, off by a given
quantity of radium is 100 times that of the gamma rays, we may assume
that at least 99% of the erythema effect was produced by the beta rays.
This being true, if we should filterthe radium rays heavily, as is done
in all attempts to get deep effects from radium, we would have only one
per cent of the previous radiation left, so that to get the same degree of
erythema it would be necessary to continue the application 100 times as
long, or 200 minutes. If we should attempt to treat a growth one inch
or 25 m.m. below the surface by laying the radium capsule on the skin,
the radium itself would be about twelve times as far from the diseased
tissue as from the skin. It would therefore be necessary to make the
exposure 144 times 200 minutes, about 20 days, in order to get a mild
erythema dose to the point desired. In doing this the skin would receive
about 150 times an erythema dose. If now to improve this surface
depth ratio we should withdraw the radium to 15 cm. or six inches
the distance at which the X-ray dose was given in the first experiment.
and allow 2 m.m. for the thickness of the radium filter, that is, the
actual distance of the radium from the skin in the surface application,
the distance in the second position would be 75 times that in the first
and the time required to give an erythema dose would be equal to the
square of 75 or 6,525 times the 3 hours required in the firstcase, which
gives a total of about 16.000 hours, nearly two years, and even then
the point one inch below the surface would have received less than threefourths
of a full dose. With these figures before us it may be stated
that there is no such thing as deep therapy by means of radium in quantities
at present available."
"The discharge of radiant energy from 50 or 100 m.g. of radium is
vastly inferior in amount or intensity to that given off by an active X-ray
tube. This may possibly be roughly visualized by comparing the discharge
from radium to the discharge of bullets by a squad of riflemen
firing rapidly in the same general direction, and the discharge from the
X-ray tube to the discharge from a battery of machine guns in action.
At a given distance from the riflemen a small tree would receive an occasional
bullet resulting in material damage, while at the same distance
from the machine guns it would receive a solid spray of lead which in
a few moments would reduce it to powdered bark and splinters."
"Now which ever of the present theories as to the way in which
radiation produces its results, we may favor, we come face to face with
this fact: That in order to produce these results in the most marked
degree wc must produce a certain density of radiation within the irradiated
field. If the 'point-heat' theory of Dessaucr should be correct,
it would seem that a considerable intensity of irradiation within the
field is necessary in order that a sufficient number of cells may be struck
a sufficient number of times within a given period—otherwise a sufficient
number of heat-points will not be developed to kill the cells."
"If we favor the theory of ionization and believe that by atomic
disruption new combinations are formed and in this way chemical changes
are set up within the tissue, this still would bring us to the conception
of a rather richly irradiated field; for if only an occasional ion were
knocked off from an occasional atom, these would likely recombine with
their recoil atoms and matters shortly be 'as they were.' "