ox SUPRARENAL BODIES TN THE MOUSE 



223 



(s. r.) is seen ns n rounded mass (al)out ^ mm. tliiek) of cells lying 

 between the aorfa(Ao.) and the mesonepliros (st.), immediately below 

 the cardinal veins (v. car.). Already at this staL>,"e, a blood vessel 

 (e. V.) is seen in the posterior portion of the blastema, coming from 

 the cardinal vein ; this vein is ultimately transformed into the central 

 vein of the adult suprarenal. The suprarenal blastema (s. r.) is 

 distinguished from all neighl)ouring tissue cells by the densely packed 

 state of its large and faintly granular cells. Cell boundaries within 

 the blastema are only faintly indicnted, but a careful observation 

 sliows that relis are collected into irregular groups, separated by 

 scanty connective tissue cells. The cell nuclei are slightly granular 

 and their size varies between 5-7 u. These characters of the cortical 

 cells are retained during the subsecpient developmental phases and aie 

 useful in distinguishing them from the medullary cells. 



Woodcut 3. 



UigJit 



A cross section taken near the posterior end of the suprarenal bodies. — 13th day 

 embryo. Ao.=aorta, c. v.=eentral vein of the suprarenal, Gr. 0.=generatiye organ, 

 s. r. = suprarenal blastema, sy. g. ^sympathetic ganglia, v. c =vena cava, v. car ;= 

 cat'dinal vein. 2xaa. 



The sympathetic ganglia (woodcut 3 sy. g.) are well developed 

 on the upper lateral corner of the aorta, ami a strong branch from 



