TRANSVERSE SECTIONS OF EMBRYO OF 12 MM. 



197 



ries. • By an oversight the two arteries are represented as one in the engraving. 

 To the right and left of the oesophagus appear the circular sections of the two 



Nch. ^- 



Ven.S. 



Fig. 120. — Pig, 12.0 mm. Transverse Series 5, Section 470. 

 Ao.S, Left descending aorta, ^m.o', Right auricle. Br.Plx, Brachial plexus. D.C.S, Ductus Cuvieri 

 sinistra. Z*.^, Dorsal root of spinal nerve. /^, Cardiac fissure. C, Spinal ganglion. Z, Anterior limb-bud. 

 Nch, Notochord. Nv, Branch of brachial plexus. CE, CEsophagus. R.D, Ramus dorsalis of spinal 

 nerve. S.a.c, Septum of the auricular canal. Scl.V, Subclavian vein. Som, Sdniatopleure. ^.^r, Spinal 

 cord. S.s, Septum superius. Tra, Trachea. Val, Auriculo-ventricular valve. Ven.S, Left ventricle of 

 the heart. V.N, Ventral root of spinal nerve. X 22 diams. 



descending aortae, of which the left, Ao. 5, is already somewhat larger than the 

 right. Ultimately the greater part of the right aorta will disappear, the aortic 



