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OTTO F. KAMPMEIER 



of the mesenchyme by which large and small fissures and spaces 

 (4, fig- 18) arise irregularly and indiscriminately along the chan- 

 nels designated. Sometimes these spaces (4-) cling closely to the 

 receding walls of the venules (6c), and at other times they are 

 separate with a perceptible amount of tissue intervening, but they 

 are always discontinuous and non-venous in character. Like the 

 more anterior lymphatic anlagen in their inception, no visible 

 difference either of form or arrangement can be discerned 

 between the cells which comprise their circumference and the 

 cells of the intricate meshwork of the mesenchyme. Strands and 



Fig. 19 Transverse section immediately in front of the mesonephroi in a 22 

 mm. pig embryo (series 105, slide 36, section 1), X 150. 4, lymphatic spaces 

 replacing the periaortic veno-lymphatics (6c); 8, dorsal segmental vein; 12d, 12s, 

 right and left supracardinal veins; 13, aorta; 14, sympathetic nerve trunk; 19, 

 embryonic vertebral column. (Reconstruction, fig. 33). 



