SYSTKM ANl) SUPKAUENAL BOBIKS IN TUB SPARROW. 



749 



be shown by recoiistnictions from consecutive sections, a method 

 which Hekl employed for some of his illustrations. Text-fig. 7, 

 however, shows a fortunate section of a chick embryo (D. 4 of 3| 

 (Inys), in AvJiich the curved track of darker cells is practically 

 continuous, thus furnishing a striking picture of the path of 

 migration. This path seems to bo markedly atFected by the 



Text-fifliure 7. 



Transverse section of cliick- embryo (3i dnys, ]) 4), showing an almost continuous 

 strand of sympathetic nerve cells from tlie point of exit of the ventral 

 nerve root to the dorso-lateral angle of aorta. 



Ao. Aorta. C.S. Sympathetic cell strand. Ktc. Notochord. 3Ii/L Myo- 

 tome. S.O. Spinal cord. Sym.C. Group of sympathetic cells. F.Ji. Ventral 

 root. 



segmental arteries and veins, for it is between these vessels that 

 the sympathetic cells move to their primary destination (see text- 

 fig. 3). It is possible that the intersegmental region oflFei'8 a 

 path of least resistance to this migration. 



A track of nerve fibres in the same position is clearly marked 



