436 



OTTO F. KAMPMEIER 



6b 



" m '" IS*** 



.^ — lis 



Fig. 12 Transverse section taken immediately posterior to the left Cuvierian 

 duct in a 20 mm. pig embryo (series 194, slide 29, section 4), X 150. 4d, isolated 

 lymphatic spaces in the right thoracic duct line; 6b, postcardinal veno-lymphatics; 

 lid, lis, right and left postcardinals; 13, aorta; 17, oesophagus. (Reconstruction, 

 fig. 29.) 



tion of the right thoracic duct limb of series 103 applies with 

 almost equal force to the left limb of this embryo, and vice versa. 

 (B) Postcardinal division. In the region of the postcardinal 

 veno-lymphatic channels the discontinuity of incipient lymphatic 

 anlagen and their origin in situ from the mesenchyme can be 

 plainly demonstrated. In a destined course and at intervals, 

 though not metamerical in sequence, spaces and fissures are pres- 

 ent in the evenly meshed tissue along the channels mentioned. 

 For instance, they can not be mistaken in figure 12 (series 194- 

 20 mm.), where two of them are shown as clear crevice-like spaces 

 (Ifd) quite sharply defined, while several others are invading the 

 environs of the veno-lymphatics (6b) and are beginning to enclose 

 one of their smaller branches. In other sections this process of 

 circumclusion has proceeded further, but in every case venous 



