Abstract
The impression that it is very difficult to
obtain objectivity and consistency in observations
on histological matè.rial was confirmed by the
reproducibility test to which the method of
classification of renal glomeruli was subjected.
This test showed a variable and sometimes high
degree of inconsistency in individual judgements
of glomerular maturity. The inconsistency was
most marked when the test was carried out by an
observer who had had no previous training in
applying the criteria, but it was also increased
by fatigue. The average results of groups of
counts showed better reproducibility than the
results of single counts. It appeared that, as
would be expected, better reproducibility was
obtained with good histological preparations than
with poor ones. It apparently made no significant
difference to the results whether the counts were
made by the "column" or the "slide" method.
It was concluded that the method of classification
and counting of renal glomeruli used in the test
could give a general picture of glomerular maturáion
but was not sufficiently objective to give reliable
detailed quantitative information.
It appears that maturation of renal glomeruli
takes place in three phases with a period of
rest preceding the final maturation. The first
phase is one of nephrogenesis which in most cases
is over by the thirty -sixth week from conception
and is not affected by the incident of birth
when this occurs prematurely. During the second
phase all glomeruli mature gradually until about
half are of adult form and the rest are at the
stage preceding full maturity. This phase is
over in most cases by the end of the first year
of post natal life. There then follows the
resing phase, which lasts until about the end of
the fifth year, in which there is little or no
change in the pattern of glomerular maturity.
Phase three, that of final maturation during which
the remaining immature glomeruli reach adult form,
is completed in most cases by the age of nine,
though in about a third of this series it lasted
until nine to twelve years of age.
A study of the changes in the relative
glomerular and secretory tubular mass in the renal
cortex indicated that, as development proceeds
from the thirtieth week from conception to the
tenth year of post -natal life there is a marked
fall in the proportion of the cortex occupied by
glomeruli and a corresponding rise in the proportion
occupied by secretory tubules. In the most
immature kidneys the ratio of glomerular mass to
secretory tubular mass was 14.5%. but by the tenth
year it had fallen to 5.4%. This fall in relative
glomemlar mass was apparently arrested between the
ages of ten months and four years, which corresponds
closely with the resting phase of glomerular
maturation.
It appeared that the changes in the glomerular
tuft epithelium used as criteria of glomerular
maturity were directly related to glomerular size
suggesting that these changes may be a simple
result of expansion of the capillary tuft
