Applying histological and morphometric methods, construction and cell composition of the inguinal lymph nodes have been studied in 125 white rats subjected to a daily dynamic (swimming) and static (hanging on a pole) loading. It has been demonstrated that the structural and cell composition changes of the lymph nodes depend but slightly on the character of the loading (dynamic or static), but rather essentially vary in the animals differently adapted to the loading. When adaptation is satisfactory, the rats gain in weight, in their lymph nodes the areas occupied by the connective tissue elements grow smaller, while the part of the cortical substance increases, with increasing number in them of follicles having light centres. As to the cell composition in the lymph node of these animals, a characteristic feature is an increasing amount of large and middle lymphocytes, lymphoblasts, plasmic cells and mitoses, that demonstrate an accelerated activity of the organism's immunological reactions. When adaptation to the physical loading is insufficient--exophtalmus, brown rings around the eyes appear, with a successive motor excitation. These animals poorly gain in weight, the number of lymphoblasts and large lymphocytes in the light follicular centres of their lymph nodes decreases, as well as the number of plasmic cells in the myelin cords; that demonstrates unsatisfactory immune processes.