TSE SPINAL NERVES. 747 



filament of tlie stylo-glossus muscle, and, finnlly, the tonsilitic ramuscules that form, around 

 the amygdala, the tonsilar plexus. 



Fneumogastria. — Formed by the union of the sensitive roots, the pneumogastrio leaves 

 the cranial cavity by the posterior foramen laoerura ; in the interior of that foramen it 

 shows the jugular ganglion ; a little lower, it has a second fusiform enlargement, the 

 rjangliform plexus, whioli is found in the Dog. Here it receives the internal branch of 

 the spinal accessory, or otherwise its motor roots. Beyond this gangliform enlargement, 

 the pneumogastrio is placed a little within the sympathetic, descends along the neck, 

 enters the chest, and terminates on the stomach and in the solar plexus. The relations 

 of the two pneumogastrics in the thoracic cavity are the same as in animals. In 

 terminating in the semilunar gdnglion, the two pneumogastrics unite and form an arch 

 named the memorahle loop of Wrisberg 



The various anastomoses of the pneumogastrio in Man offer nothing particular. 

 The pharyngeal branches leave the gangliform plexus, and are constituted by the 

 filaments carried to the pneumoj:astrio by the internal root of the spinal accessory. They 

 are two, three, or four in number, and form tlie pharyngeal plexus. 



The superior laryngeal nerve also arises from the gangliform plexus, and offers, as in 

 Kuminants, a Galieu branch tliat anastomoses, end to end, with a branch of the infeiior 

 laryngeal. The external laryngeal is furnished by this nerve ; it is distributed to the 

 inferior constrictor muscle of the pharynx, tlie crico-thyroid muscle, and the mucous 

 membrane of the subglottic portion of the larynx and the ventricle of the glottis. 

 The recurrent nerves affect a distribution analogous to that already made known. 

 The pneumogastrio also gives cardiac, pulmonary, and oesophageal branches. The 

 cardiac lie beside those coming from the sympathetic and recurrents, and enter the 

 ganglion of Wrisberg, situated at the base of the heart. Tlie oesophageal branches are 

 remarkable for their numljer and complexity, and form a veritable oesophageal plexus. 

 The gastric branches are also very numerous. 



Spinal accessory. — It presents bulbous roots which are well known, and medullary roots 

 which usually extend to the fifth cervical, and sometimes to the first dorsal. After its exit 

 from the posterior foramen lacerum, it divides into two branches— an internal and external. 

 The internal branch, formed by the bulbous roots, enters the gangliform plexus of the 

 pneumogastrio. The external branch cumports itself as in animals. 



The hypoglossal resembles that of Carnivora, and, like it, possesses a bianch for the 

 hyo-thyroideus and genio-hyoideus. 



CHAPTER II. 



SPINAL NERVES. 



"We designate as spinal, vertebral, or rachidian nerves, those which emanate 

 from the spinal cord, and leave the vertebral canal by the intervertebral 

 foramina to proceed to the various organs. . i j. n 



They are estimated at 42 or d3 pairs, and are apportioned as follows in 

 the five regions of the spine : cervical, 8 pairs; dorsal, 17 pairs; lumbar, 6 

 pairs ; sacral, 5 pairs ; and coccygeal, 6 to 7 pairs. 



They differ from the encephalic nerves in closely resembling each other 

 in the fundamental points of their constitution. All proceed from the lateral 

 aspects of the spinal cord by two orders of roots: one motor the other 

 sensitive (Pig. 317). In all, these two roots unite in a very short trunk 

 in passin<^ through the intervertebral foramen ; and this trunk divides almost 

 immediately into two terminal branches : a superior, destinea to the spinal 

 muscles and tfie integuments covering them ; the other, inferior, passes to 

 the lateral and lower parts of the trunk or to the members. All send Irom 

 their inferior branch, one or more ramuscules to form the great sympathetic. 



The roots of the spinal nerves offer everywhere the same disposition ; 

 each nerve is formed by two fasciculi of converging filaments, superior and 

 inferior which are naturally more numerous and large when they belong to 



