Abstract
A total of 121 pregnant m ice were used for this study. Quantitative histometrical measurements (frequencies per square millimeter of occurrence of follicles over 50 it in diameter and irregular-shaped follicles, and percentages per field of occurrence of follicles containing darkly stained colloid) were made. It was found that some histological fluctuations may occur in follicles and colloid with the progress of gestation.
Early pregnancy: Immediatly after mating the thyroid gland is composed predominantly of small follicles and colloid is feebly stained. During the first half of this period the gland is composed of large follicles with a predominant occurrence of darkly stained colloid and suggests a transitory storage phase. During the second half, presumably shortly before and at the time of implantation of fertilized ova, the gland shows a trend to decrease in size and irregular change in shape of follicles, together with poorer staining of colloid, marked swelling of follicle epithelium and capillary hyperemia.This may suggest evidently a phase of release of colloid.
Mid pregnancy: The gland shows a trend towa r d s increase in size of follicles and subsequently a stable state of follicles and colloid. The gland is generally composed of large follicles with darkly stained colloid.
Late pregnancy: The gland indicates a slightly unstable state, especially near term. Colloid stains inconstantly. General follicles are decreased in size and show irregular change in shape.
The author wishes to acknowledge his thanks to Prof. D r. Shooichi Sugiyama for his kind guidance throughout the course of this study. Further, the author is indebted to Prof. Dr. C hikataro Togari for kind encouragement and help.
