In man and in certain of the lower vertebrates, nodal collections of lymphoid cells occur, and are divisible into two groups, namely, those which are provided with lymph sinuses, or ordinary lymph nodes, this group comprising by far the larger number ; and those which are provided with blood sinuses, the latter being variously known as hemolymph nodes, splenolymph nodes, or more simply and better, perhaps, as hemal nodes. The exact anatomic position of the hemal nodes has not been determined. The preponderance of evidence, however, favors the view originally advanced by Vincent and Harrison,1 that they are more closely related to the spleen, structurally and otherwise, than to the lymph nodes proper. In fact, Meyer,2 in a series of injection experiments in sheep, has shown that the hemal nodes are in no way connected with the lymphatic system. Embryologically, the hemal nodes, like the spleen, are vascular bodies or masses of erectile tissue that have become modified in the process of development by the interposition of focal collections of lymphocytes in the meshes of a reticulum derived from the walls of blood vessels.3
ing of the bladder between the fetal head and abdominal wall. The importance of these mechanical conditions and the stasis resultant therefrom is not to be overlooked.
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