188].] 1^1 [Stowell. 



Thoracic division of N. vagus sinister: The main trunk of N. 

 vagus sinister enters the thorax dorsad of V. innominata sinistra at the 

 union of Y. subclavia and V. jugularis externa, meso-dorsad of V. verte- 

 bralis and laterad of A. carotidea primitiva sinistra. In the thorax cephalad 

 of the arch of A. aorta the nerve lies between AA. carotidea and subclavia 

 meso-dorsad of A. sternalis until it reaches a point 10-15 mm. cephalad of 

 A. aorta, at which point it rests upon the ventral surface of A. subclavia 

 and crosses the arch ventro-laterad of the origin of A. subclavia. Opposite 

 the origin of A. sternalis the nerve is crossed by N. phrenicus and lies 

 dorso-laterad of this nerve in the area between the two arteries aforenamed. 



As N. vagus enters the thorax, two fasciculi from the middle and caudal 

 areas respectively of the middle cervical ganglion of N. sympathicus, G. 

 thyreoideum, connect N. vagus with N. sympathicus; these commissural 

 fasciculi are about 3 mm. apart. Between a point opposite A. sternalis 

 and the arch of A. aorta the trunk of N. vagus sustains intimate relations 

 with N. sympathicus, N. cardiacus magnus and N. cardiacus minor 

 through numerous anastomotic filaments which constitute aplexiform net- 

 work around the arteries, trachea and oesophagus in this region of the 

 thorax — AA. subclavise, carotidese primitivse and innominata. Opposite 

 the caudal border of the arch of A, aorta a considerable fasciculus from 

 the main trunk about 5 mm. in length joins N. laryngeus inferior. 7 mm. 

 peripherad of this fasciculus, where N. largyneus inferior bends around 

 the arch of A. aorta,^a ramulus is given off whose interlacings with rami 

 from NN. vagus and sympathicus constitute a plexiform network which 

 is related with the cardiac plexus. In its course caudad of arch of A. 

 aorta. N. vagus passes dorsad of the root of the left lung. 



Pulmonary Rami : Between a point opposite the cephalic border of 

 A. pulm<niaris and 15 mm. caudad, N. vagus gives several ramuli meso- 

 ventrad to anastomose with terminal filaments of N. cardiacus minor and 

 N. laryngeus inferior in the formotion of the ectal (superficial) cardiac 

 and the ventral (anterior) pulmonary plexuses. From the same region of 

 the main trunk filaments are directed meso-dorsad, which interlace in a 

 dense network with filaments of offsets detached from the main trunk of 

 the area above named, and with terminal filaments of N. cardiacus minor, 

 and other filaments from N. sympathicus to form on the ventral aspect of 

 the trachea just cephalad of its bifurcation, a large plexus, the ental car- 

 diac — Px. %>rofundus magnus — from which filaments ramify upon the 

 bronchi and have intimate relations with the plexiform network which is 

 formed by filaments from the offsets named and accessory offsets from 

 thoracic ganglia of N. sympathicus around the bronchi, — dorsal pulmonary 

 plexus. Offsets from this plexus may be traced along the air tubes into 

 the substance of the several lobes and upon the broncho-pulmonary mu- 

 cous membrane of the sinistral lung. The ramuli which form th'e dorsal 

 pulmonary plexus are noticeably larger than those given to the ventral 

 plexus. 



CEsopliageal Hami : Cephalad and caudad of the pulmonary rami 



PROC. AMER. PHILOS. SOC. XX. 111. Q. PRINTED MARCH 8, 1882. 



