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CHANGES IN THE HISTOLOGY OF THE THYROID [ Vol. XXV, Part IV,
Statistical analysis of data
To find out if the variations in the measurements of the glands during different
seasons were due to chance only, the data were subjected to statistical analysis.
The results of the analysis are presented in Tables II to IV.
Table II shows analysis of differences in the mean diameter of the thyroid
lobule, height of the epithelial cells of the thyroid lobule and the diameter of the
testicular tubule in four seasons. In the Table, the differences underlined are
statistically significant. It is apparent from the Table that there was no significant
variation in the diameter of the thyroid lobule and in the height of the epithelial
cells during spring and winter. There was also no significant difference in the
mean diameter of the testicular tubule between summer, winter and spring.
The statistical analysis of data indicates that the diameter and the height of the
epithelial cells of the thyroid lobule and the diameter of the testicular tubule undergo
seasonal changes. In this study, seasons have been classified on the basis of air
temperature and relative humidity. To find out if one or both the atmospheric
factors were responsible for seasonal changes in the two glands, partial correlation
coefficients between the atmospheric factors and the various measurements of the
two glands have been determined. This is presented in Table III. It will be seen
from the Table that the partial correlation coefficient between air temperature
and the height of the epithelial cells of the thyroid lobules was negative and highly
significant. This indicates that when relative humidity was held constant, the
increase in air temperature decreased the height of the epithelial cell of the thyroid
lobule. Similarly, the increase in air temperature decreased the diameter of the
testicular tubule when the other factor, viz. relative humidity, was held constant.
Air temperature had no significant effect on the diameter of the thyroid lobule.
Increase in relative humidity, when air temperature was held constant, decreased
the diameter of the thyroid lobule. Similarly, increase in relative humidity decreased
the height of the epithelial cells and the diameter of the testicular tubule when air
temperature was held constant. Multiple correlation coefficients (R) which indicate
the effect of combined variable atmospheric factors on the variates studied are
as follows:
R for the height of the epithelial cells= 0.869**
R for the diameter of the thyroid lobule= 0.660**
R for the diameter of the testicular tubule= 0.727**
(** Significant at 1 per cent level)
All the values of R are highly significant, and they suggest that among the three
charateristics studied, it was the height of the epithelial cell which was most
sensitive to atmospheric changes. Among the two diameters, the diameter of the
testicular tubule was more sensitive to changes in air temperature and relative
humidity than that of the thyroid lobule. Multiple regression equations X 1 for
air temperature, X 2 for relative humidity and Y the estimated value are as follows:
(1) Y (for the diameter of the thyroid lobule)= 352.54—0.697X 1 —1.469X
(2) Y (for the height of the epithelial cells)= 10.20—0—048X 1 —0.040 X
(3) Y (for the diameter of the testicular tubule)= 294.42—0.779 X 1 —0.771 X 2