. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 536 In describing the stages which just precede and which lead up directly to a definite establishment of the thoracic and right lymphatic ducts, we will begin with a 14 mm embryo. In the 14 mm embryo, as intimated above, there is as yet no indication of a definitely established thoracic or right lymphatic duct, either in front of or behind the cardinal-Cuvierian junction. In their place, however, there are present a number of venous outgrowths which are in the process of being split off from the main venous channels, exactly
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 536 In describing the stages which just precede and which lead up directly to a definite establishment of the thoracic and right lymphatic ducts, we will begin with a 14 mm embryo. In the 14 mm embryo, as intimated above, there is as yet no indication of a definitely established thoracic or right lymphatic duct, either in front of or behind the cardinal-Cuvierian junction. In their place, however, there are present a number of venous outgrowths which are in the process of being split off from the main venous channels, exactly in the line followed by these ducts in the 16 mm embryo. These venous out- growths, in the writer's estimation, constitute the veno-lymphatic an- lages of the thoracic and right lymphatic ducts. The reconstruction of the 14 mm embryo (Fig. 2) shows the presence of the venous out- growths which arise along the dorsal surface of the left common jugular and innominate veins and, when compared with the reconstruction of the 16 mm embryo, it is seen that they occupy in this region the same relative position with respect to the main venous channel, the A. thyro-cervicalis and the sympathetic nerve, as does the thoracic duct in the 16 mm embryo (Fig. 1). These relations are further borne out by a study of the following microphotographs of transverse sections of the 14 and 16 mm embryos taken, approximately, at corresponding levels, as indicated by arrows in Figs. 1 and 2. Figs. 3 and 4, of a 14 and 16 mm cat embryo i), respectively, represent trans- verse sections through the body in the neighborhood of the left jugular lymph sac where the outgrowth from the left common jugular vein (veno- lymphatic anläge of thoracic duct) and the thoracic duct both lie be- tween the A. thyro-cervicalis and the sympathetic nerve. Figs. 5 and 6, also of a 14 and 16 mm cat embryo, respectively, represent trans-. Fig. 2. Dorsal view of a reconstruction of a 14 mm cat embryo, made after the method of B
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