Quantitative Study on the Postnatal Growth and Involution of the Thymolymphatic Tissues in the Albino Rat

In the present study, the postnatal growth and involution of the thymolymphatic tissues of the albino rats at different ages were studied chiefly by means of the quantitative analysis. The chief results are as follows: 1. The absolute growth of the thymus reached its maximum in the 3rd month in females and in the 4th month in males. The mesenteric lymph nodes, in both sexes, reached its maximum development in the 4th month, and the spleen in the 3rd month in females and in the 6th month in males (Figures 2, 3 and 4). 2. Looking into the relative growth, the thymus after reaching its maximum at the 2nd or 3rd weeks, underwent a rapid involution, while the mesenteric lymph nodes and spleen intiated their development in this period and were still growing in the 3rd or 4th months (Figures 5 and 6). This suggests that a rapid involution of the thymus may be closely related with further growth of the other lymphatic tissues.