298
CHANGES IN THE HISTOLOGY OF THE THYROID [ Vol. XXV, Part IV,
Examinations of equations 2 and 3 will indicate that in the two equations, the
coefficients for X 1 and X 2 are equal. This suggests that 1 degree rise in air tempera-
ture caused as much change to the height of the epithelial cells or the diameter of
the testicular tubule as was due to 1 per cent change in relative humidity. Examina-
tion of equation indicates that coefficient for X 2 is almost 2 times more than X 1 .
This indicates that 1 per cent change in relative humidity caused two times as much
change in the diameter of the thyroid lobule as was due to 1 degree change in air
temperature. Thus, for variations in diameter of the thyroid lobule, relative humi-
dity was comparatively more responsible than air temperature, whereas for variations
in the height of the epithelial cells or the diameter of the testicular tubule both the
atmospheric factors were equally responsible.
To find out the effect of seasonal changes of one gland on the other correlation
coefficients between the diameters of the thyroid lobule and the height of the epi-
thelial cells, between the diameters of the thyroid lobule and the testicular tubule
and between the height of the epithelial cells and the diameter of the testicular
tubules have been worked out and presented in Table IV. It will be seen from the
Table that there was highly positive correlation coefficient between the height of the
epithelial cell and the diameter of the testicular tubule. It seems, therefore, that
when the height of the epithelial cells of the thyroid lobule increased, the diameter
of the testicular tubule also increased. Partial correlation coefficient between
the height of the epithelial cells and the diameter of the testicular tubule when air
temperature and relative humidity were held constant has been found to be 0.013
and non-significant. It indicates that variation in the height of the epithelial cells
has no direct effect on the diameter of the testicular tubule.
DISCUSSION
The thyroid has provision for storage of hormone in the central lumina of the
follicles. In periods of most active secretion, the stored hormone may be discharged
in the blood stream and the glandular cells elongate under the stimulation of increased
secretion of the pituitary thyrotropic hormone. During periods of thyroid inactivity,
hormone may be stored up in the lumina of the follicles and the glandular cells
shorten and become less active [Watzka, 1938; Baker, 1949; Holm, 1949].
From the histological studies of the thyroid of buffaloes it seems, that in spring
and winter when air temperature was much lower associated with higher relative
humidity than in summer the diameter of the lobules was significantly smaller and
the height of the epithelial cells highly significant, more than in summer. During
the active state more of the thyroid hormone was produced and discharged into the
blood as a result of which the lumina of the lobules were smaller and the height of the
epithelial cells more than that in summer. During summer when air temperature was
high, coupled with low relative humidity, the bigger lobules with lower epithelial
cells having flattened nuclei indicated that the hormone was stored up in the gland
and very little was discharged into the blood. In autumn when average air tempera-
ture was slightly lower with conspicuously higher relative humidity than in summer,
there was a significant decrease in the diameter of the thyroid lobule and the height
of the epithelial cell than in summer. This result indicates that during autumn