410 

[JUNE 10, 1915 

gested that destructive organic effects are due to un- 
timely oxidation. 
The physician possesses in radiation a subtle means 
of attacking the mechanism of cell-growth, and one 
of unlimited power. It is a characteristic feature of 
true scientific advance that new powers, based on 
newly-discovered forces, are placed at our disposal. 
The possibility of physical interference with the atomic 
linkages of organic structure and its sustaining meta- 
bolic processes is a recent conception. The older 
practice recognised one way only of effecting such 
interference—by the intervention of chemical actions 
set up by drugs assimilated through the digestive 
system. Although we are to-day far from a_know- 
ledge giving complete control of radiative effects, I 
venture to think that these will ultimately be found 
to be more definable and manageable than medicinal 
treatment. 
Let us consider, so far as' we can, what we are 
doing when we insert into a tumour a needle filled 
with emanation. 
Within the tube the radio-active transformations of 
the atom are attended by three forms of radiations. 
(1) a rays, which are positively electrified helium 
atoms, and cannot pass the walls of the tube. With 
these, therefore, we have nothing to do. 
(2) Also B rays, o1 electrons, are sent out. Some 
of these are so slow as also to be stopped by the thin 
glass and steel walls surrounding the radio-active 
Substances. But these walls are thin enough, as used 
in the technique introduced by the Radium Institute 
of the Royal Dublin Society,t to permit a large pro- 
portion of them to escape. Their velocity varies over 
a wide range, some electrons moving at speeds nine- 
tenths that of light. Their velocities are such as to 
give, as already stated, both a line and a continuous 
“spectrum” when sorted out by a magnetic field. 
These electrons are known to be the direct agents 
in effecting ionisation. The faster electrons probably 
penetrate a couple of centimetres in soft tissues, their 
energy dying out in the creation of ions and secondary 
y rays. The latter are re-converted to 8 radiations, 
which again take up the work of ionisation. Thus 
the whole of their energy, or the greater part of it, 
is, probably, ultimately spent in the work of ionisa- 
tion: in other words, on work which is capable of 
seriously modifying the chemical and molecular pro- 
cesses progressing in the medium. 
(3) There emerge, also, from the tube the y rays 
of RaB and RaC. The latter enormously pre- 
dominate, most of the rays of Ra B being sufficiently 
soft to be absorbed in the walls of the tubes. These 
rays, as we have seen, move with certain definite 
quanta of energy, or in integrals of a certain quantum 
in each case: in short, in trains of rays. Wherever 
they traverse atoms they give rise to 8 rays. Some of 
these, taking up the whole energy of a wave-train, 
move with velocities similar to the most penetrating 
primary @ rays given out by the parent radio-active 
atoms. This is the inner history of the events lead- 
ing to the ionisation of the medium according to 
recent views. 
The number of ions which these rays can generate 
in air has been computed.’ In reckoning the number 
of ions two count for one, as each electron separated 
involves the formation of both a+ and a —ion. The 
numbers given refer, therefore, to pairs of ions. 
The quantities of the substances RaB and RaC 
used in the estimates are those which will be in equili- 
brium with one gram of elemental radium or with 
one curie of emanation. These substances alone con- 
4 Stevenson, Brit. Med. Jour., July 4, 1914, and March 20, 1915. 
5 Moseley and Robinson, P/zl. Mag., vol. xxviii., September, 1914. 
NO. 2380, VOL. 95| 
NATURE 
\ 


‘ cern the surgeon when’ he applies radio-active treat- 
ment by usage of the emanation. The rays are sup- 
posed to act for one second of time. 
From B rays of RaB 0-325 x 10° 
a9 0) SARE RaC 0:64 x 10'° 
ay) 5, RaB 0-084 x 10!” 
ety. ss RaC 1-134 x 107° 
Total 2-183 x I0'* 
Now it is of interest to estimate what these num- 
bers would represent in the therapeutic use of these 
radiations in body-tissues, on the assumption that the 
energy is in a similar degree expended on ionisation 
—an assumption which may approximate to the facts, 
seeing that the mere state of aggregation—solid, 
liquid, or gaseous—should not much affect the results. 
I take the volume of an average cell as 125 x 107° 
cubic centimetres, which is the volume of a cube 
1/500 of an inch on the edge. 
I shall assume the surgeon inserts the radio-active 
needles containing the emanation one centimetre apart, 
and that he has only one millicurie in each needle, 
the radio-active length of the needle being one centi- 
metre. I shall also assume, as a first_approximation, 
that the radiations are completely absorbed within the 
boundaries of the tumour being treated. 
The number of pairs of ions generated per second 
by one millicurie will be 218x10!2. And as the 
needles are one centimetre apart, we have this number 
generated per cubic centimetre. In a single cell the 
number is 272 x Io* pairs of ions. 
In actual practice there may be about five millicuries 
in each needle. We have then, theoretically, more 
than 1-3 million pairs of ions generated per cell per 
second. The assumption that all the rays are absorbed 
in the tumour is not accurate, and again the numbers 
given apply to quite unscreened radiation only. The 
softer 8 and y rays suffer absorption in the glass and 
steel envelopes. This loss applies chiefly to the rays 
from RaB. In order to make a safe allowance for 
these sources of error, as well as for the loss of the 
most penetrating of the y rays of Ra C which escape 
from the tumour, I take 50 per cent. of the calculated 
number of ions, that is, 136,000 pairs of ions per cell 
per millicurie per second; or, in the working condi- 
tions, 680,000 per cell per second. In exposures 
measured by hours the numbers rise to thousands of 
millions : in ten hours to twenty-four thousand millions 
of pairs of ions per cell. 
These figures are instructive, whether they represent 
entirely effective and useful ionisation or not. Even 
if only a small fraction is usefully expended, they 
reveal the power of radio-therapeutic methods in con- 
trolling or initiating chemical changes within the cell. 
The effects of this powerful ionisation on the cells of 
the body have been demonstrated repeatedly by micro- 
scopic examination. I would refer more especially to 
the fine series of photographs obtained by A. Clifford 
Morson on carcinoma and sarcoma before and after 
exposure to radiation.® After treatment for twenty- 
four hours with 90 mgrms. of radium the obliteration 
of structure is far advanced, or even, to all appear- 
ance, complete. In the case of healthy cells of the 
rat, Lazarus-Barlow has shown that considerable expo- 
sures may produce no more than temporary disturb- 
ance of growth, and that even while treatment is pro- 
ceeding the)cells may become again apparently normal.” 
The important point has frequently been brought out 
that the healthy cell behaves as a less sensitive system. 
This, of course, is at the basis of radio-active treat- 
ment. It is not improbable that a dosage which will 
& Morson, ‘ Archives of the Middlesex Hospital,” XXXill., P. ITO. 
7 Lazarus-Barlow, Zoc. cit., p. 34- 
