Three dimensional analysis of thymic medulla

In consecutive serial paraffin sections centers of gravity were defined for individual cross-sections of thymic medulla of the rat. Coordinates of the centers provided grounds for a three-dimensional reconstruction of thymic medulla using for the purpose computer techniques. In all cases the medulla exhibited continuity throughout the organ and showed dendritic character with up to IVth order branching. Moreover, analysis of thymic medulla structure allowed to exclude existence of a structure which would correspond to thymic lobuli. Apart from volume and area of the cortex and the medulla, lengths of the medulla and of its branches were determined. Statistical analysis of the results demonstrated that length of individual types of medulla branches was the least variable character of the thymus while the most variable one included area of the cortex and the medulla and their volume. All parameters describing volume and area of the thymic cortex/thymic medulla were found to correlate with each other. No significant relation was observed between the parameters on one hand and length of the medulla on the other.