1‘
= 23 -
depth is near the base of the hair follicle which comprises
the deepest reservoir of ‘epithelial cells of the germinal
layer, it was suggestive that this might be a critical
The suggestion gained
region in the observed carcinogenesis.
significance from the observations that most of the tumors
are similar to hair follicles, and that in the non-ulcerogenic
dose range the number of tumors per rat was in nearly constant
ratio
(1/2000-1/4000) with the number of atrophied hair
follicles.
Thus the carcinogenesis in this experiment
was remarkably correlated with the dose to and specific
damage of a particular skin structure.
When exposures were
made with strive and sieve patterns of roughly 1 mm scale,
geometrical effects were observed:
most notably the cancer
induction in the sieve geometry was suppressed at doses of
1700 rad but not at doses of 2300 rad.°
The reduction, however,
was again consistent with the reduction in damage as characterized
by atrophied hair follicles.
To summarize this important experiment, a high incidence
of cancer was observed after intense local doses of radiation,
and the carcinogenesis was proportional to the damageor
disordering of a critical architectural unit of the tissuc,
the hair follicles,
.,