

/.'. Sabin. 



"i 'lull red grapes against the cardinal vein; in the older specimens 

 • ■I the IhiiI- are markedly larger than others, while ai 1 I mm. 

 -i of them in;i ki -~ n definite sac with large sprouts p 

 dorsalward. At this stage, namely, 11 nun., the sac can be in- 



• 



5 i 



-As- 



Pro. 7. Injection of the left Jugular lymph sac in an embryo pis which 

 measured 18 mm. in its greatest diameter. The specimen was fixed in in 

 per cent formol and cleared by the Spalteholz method. Magnified about 30 

 times. The glass canula which shows piercing the upper border of the arm 

 bud shows the point of injection. A. c. - anterior curvature of the lymph 

 sac; A. s. = apex of the lymph sac; 1. = glass canula used for injection; 

 S. s. = stalk of the lympb sac: V. j. i. = vena jugular interna. 



by direel puncture. The preceding or plexus stage is shown bj E. !.. 

 Clark for the corresponding sac in the chick in fig. L5. The beginning 

 -.n i- shown for the human embryo in lL r . I!M (Sabin 134). 



It is not easj to gel perfect injections by direel puncture, but by 

 the timi the embryo is Ifi nun. the dorsal sprouts from the sac arc 



