oN
chromosome, the change of permeability of the cell membrane, the
_
suppression of cell-division, the decrease of leucocyte, the induction
of the boil, death, etc.
One of the most important facts about the biological effect of
radiation is known as the law of Tribondeau-Bergony which asserts that
the cell is most sensitive to the radiation when it is young and has
the tendency of cell-division. For instance, in the human body, blood-
producing organs (bone, spleen, lymphatic, etc.) and genital cells are
most likely to be injured by radiation.
The injury of radiation from outside of the body may be classified
into two categories. One is caused by the 6 - ray of fission products
adhered to the skin. In this case, the skin turns to black, gives rise
to bleb or fester, and the hair may be lost from the head. In fact,
hands and faces of two patients who entered the Tokyo University Hospital
on March 15 were black and had festers at some places. It was found by
a Geiger counter that the radioactivity was strong at the head, ears,
neck, armpits, abdomen, sole, parts of hands or feet between the fingers
or toes. The result of measurement by the miliroentgenometer (distance
5 em) is given in Table kh.
Fig.
The radioautograph of the hair is shown in
3 e
The other is caused by the y - rays of radioactive substances
adhered to the deck, cabin, fishing implements, clothes, etc, Since the
{- ray has a large penetrating power, it will irradiate the whole body ami
cause the change of blood (decrease of leucocyte), recurrent anenta,
depilation, injury to the genital cells, hereditary change, etc.
wear
te
As is well-known, we are incessantly exposed to the cosmic-ray from
the sky and the radiation of natural radioactive substances like radium
and radon from the earth. Nevertheless, we are not injured by these
radiations, not to a visible extent at least. This is due to the fact
that even the exposure on successive days has no damage if the amount
of irradiation is less than a certain limit. The maximum amount which
the human body can tolerate is called the permissible dose. The international society of radiology determined that the permissible dose is
300 miliroentgen per week. People living on a boat are exposed to the
radiation at any time so that the permissible dose is 1.8 mr per hour.
The intensity of radiation on the Fukuryu Maru measured at Yaizu on
March 17 was 10~ 100 mrper hour which was 5~50 times the permissible
dose.
In Table 5, it is shown how the intensity of radiation changes from
place to place in the boat and how it changes with time. It is seen that
on the average the intensity decreased to about 20~30 % of the value of
* Marth ‘17 during the period of a month. If one estimates the intensity
‘of radiation on March 2 from the damping curve, it is about 50 times
larger than that of March 17.
Several hours after the ash began to
come down many fishermen felt sick and some vomited.
-3-
ie
This is the so-called