2G 



Florence E. Sabin. 



slight, not as marked as in the chick, nor as it is on the left side of this 

 same embryo. 



Arising from the cardinal veins there is a series of seven deep 

 segmental branches extending to the nervous system between the 

 area of the primitive posterior cerebral vein (Mall 143), which arches 



1__A 



Fig. 4. — Injected specimen to show the anterior cardinal vein and its 

 branches in an embryo pig which measured 7 mm. in its greatest diameter. 

 Magnified about 28 times. This is a stage before the lymphatic vessels 

 have begun. A = aorta arches; D. C. = duct of Cuvier; V. c. p. = vena 

 cerebralis posterior; V. 5 — fifth segmental vein. 



downward over the medulla and cord and the cerebral end of the arm 

 bud. The first two of these branches drain the medulla, and hence 

 there are five spinal or segmental branches proper. Each of these 

 branches has a corresponding artery which lies slightly caudalward 

 and nearer the midline. Only the lower four segmental arteries are 

 injected in this specimen. The relative position of artery and vein 



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