. The American journal of anatomy . r division into the right and left limbsof the duct becomes shifted far back of the lymph sac. Series192 (3, fig. 35) presents an intermediate stage in which the orig-inal plexiform condition is still suggested but has been almostentirely obliterated by the transverse fusion and consequentreduction of the number of interanastomosing channels. No matter whether the thoracic duct anlagen arise as extra-intimal spaces or entirely apart from the veno-lymphatics, dur- 456 OTTO F. KAMPMEIER ing their genesis their walls are composed of the undifferentiatedmesenchy
. The American journal of anatomy . r division into the right and left limbsof the duct becomes shifted far back of the lymph sac. Series192 (3, fig. 35) presents an intermediate stage in which the orig-inal plexiform condition is still suggested but has been almostentirely obliterated by the transverse fusion and consequentreduction of the number of interanastomosing channels. No matter whether the thoracic duct anlagen arise as extra-intimal spaces or entirely apart from the veno-lymphatics, dur- 456 OTTO F. KAMPMEIER ing their genesis their walls are composed of the undifferentiatedmesenchymal cells (figs. 6, 9, 18, etc). We have also seen themethod of concentric addition of tissue spaces by which theanlagen enlarge during the later transition and early lymphaticstages, implying thus a continual shifting of their boundaries sothat an intima may be said to be temporarily established, replaced,and reorganized a number of times (figs. 22, 25, etc.) Ultimately,however, we can speak of a definite and permanent endothelium. Fig. 26 Transverse section through the region of the cisterna chyli in a 23 embryo (series 67, slide 43, section 14), X 150. 5, anlage of the cisterna chylishowing the indefinite and ragged outline of its cavity, the absence of a specializedintima, and the addition of small spaces (4) from the mesenchyme; the vestigesof the former veno-lymphatics have completely disappeared; 13, aorta; 14, sym-pathetic nerve trunk. THORACIC DUCT DEVELOPMENT IN THE PIG 457 12d 12 s V> V-- ViM&i ■ • - kw r 14 i 5d - ■UV»■$^-t-^Tji ) , < -•
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1912
