388 ANATOMICAL TECHNOLOGY. 



is distributed to the ventral aspect of the stomach ; the other branch of the vagus vrinds 

 to the dorsal side of the cesophagus, where it is joined by a small branch from the right 

 vagus. The union of the two forms the dorsal gastric nerve, which penetrates the dia- 

 phragm on the dorsal side of the oesophagus, and is distributed to the dorsal aspect of the 

 stomach and especially to its greater curvature (Fig. 79). 



The vagus supplies branches to the larynx, trachea, heart, lungs, maophagus and stom- , 

 ach. Throughout its entire extent it is closely related to certain spinal nerves and to the 

 sympathicus. 



The origin, course and distribution of the right vagus is nearly the same as that of the 

 left, except that the recurrent laryngeal is given off opposite the A. snbclama dextra (Fig. 

 1 08), and winds around to its dorsal side to reach the trachea. 



The account of the vagus is introduced partly in order to illustrate the origin, course, 

 distribution and relations of a peculiar cranial nerve, but especially on account of its 

 importance from an experimental standpoint. 



DISSECTION OF THE VAGUS NERVE. 



§ 1031. Specimen and Preparation. — The specimen should be young and lean (§ 1008). 

 The vascular system should be filled from either the femora] or abdominal vessels (§§ 352, 

 363). The same specimen is to be used for the sympathic (§ 1042). 



§ 1032. Exposure and Dissection. — A block should be placed 

 under the cat' s neck so that the head may be slightly dorslducted. 

 After parting the hair (§ 354), make an incision from the left exter- 

 nal auditory meatus to a point opposite the tip of the xiphistemum, 

 going about 2 cm. to the left of the ventrimeson. The skin should 

 be reflected on both sides of the incision for 2-3 cm. and held aside 

 with pins. Find the position of the larynx and trachea (Fig. 88) by 

 pressing on the ventrimeson. 



Make a longitudinal incision through the sterno-mastoid mus- 

 cles just laterad of the trachea, commencing near the 1st rib and 

 cutting cephalad to the bulla (Fig. 57). It is necessary to proceed 

 with caution, however, in order not to injure the vessels and nerves 

 on the ental side of the muscle. Turn the cut edges of the muscle 

 aside and fasten them with pins. This will expose three structures 

 lying parallel to the trachea : — the carotid artery, which, being 

 injected, will be very apparent ; at the same level as the carotid, 

 but laterad of it, the combined vagus and sympathic nerves ; and 

 finally between the two, but somewhat ventrad, the internal jugu- 

 lar vein (Fig. 101). 



Commence near the middle of the neck and follow the nerve 

 cephalad, using the tracer, fine forceps and scissors. Near the 

 bulla (Fig. 57 and 107, B), the submaxillary and lympliatic glands 

 (Fig. 87) and the thyroid hody (Fig. 101) must be removed. At the 

 ganglion of the root the vagus may be easily separated from the 



