406 DR. C. F. SONNTAG ON THE ANATOMY, 



The Spinal Accessory Nerve emerges as in Man from the 

 jugular foramen, pierces the cleiclo-mastoid, runs deep to the 

 sterno-mastoid and gains the deep surface of the trapezius, where 

 it has already been described. It supplies the cleido-mastoid, 

 sterno-mastoid and trapezius, and it communicates with the 

 cervical plexus, but not with the sympathetic. 



The Hypoglossal Nerve emerges as in Man from the skull, and 

 has a similar disposition till it reaches the hyo-glossus muscle. 

 At the anterior border of that muscle it forms a loop and exhibits 

 a swelling slightly anterior to it. This swelling receives filaments 

 from the lingual nerve, and there is no separate submaxillary 

 ganglion. Finally it divides into twigs for the stylo-glossus and 

 genio-glossus. Branches: — (1) On the left nerve there is a 

 strong descendens hypoglossi, but it is replaced by two branches 

 on the right side. (2) Nerve to the thyro-hyoid muscle. (3) 

 Nerves to genio-hyoid. (4) Comiiminicating to the lingual nerve. 

 (5) Nerves to genio-glossus. (6) Nerves to stylo-glossus. 



The Cervical Plexus (text-fig. 47). 



The cervical plexus is formed from the first four cervical nerves, 

 and its relations are similar to those in Man; but there are 

 differences in the branches. The first and second nerves form a 

 loop. Branches of the second and third nerves form cords ; a 

 mesia,l cord forms the nerve to the sterno-hyoid (S-H.M) and 

 a latei'al cord forms the transverse cervical (T.C.N) and occipital 

 nerves (O.N), Branches of the third and fourth nerves form the 

 descending supraclavicular nei'ves (S-C.N). The fourth nerve 

 communicates Avith the fifth. 



Branches : — 



I. Superficial Cutaneous Nerves : — Small occipital (O.N) and 

 transverse cervical (T.O.N) from 2 and 03; Descending 

 branches (acromial, steinal, and clavicular) from 3 and 4. 



II. Beep Muscular Branches to sterno-mastoid (S-M. from 2), 

 trapezius (Tra. from 3 and 4), levator anguli scapula3 (L.A.S. 

 from 3), scalenus medius (Seal. Med. from 4), omo-hyoid 

 (0-H.M. from 2), sterno-thyroid (S-T.M. from 2), sterno- 

 hyoid (S-H.M. from 2 and 3), and diaphragm (by phrenic 

 (P.N) from 2, 3, 4, 5). 



III. Deep Communicating Branches to vagus (G.N), accessory 

 (xi) and hypoglossal (xii) from 1 or 2. There are no separate 

 branches to the sympathetic on the left side, but the ganglion 

 nodosum and superior cervical sympathetic ganglion are con- 

 nected close to the spot Avhere the vagus communicates with the 

 cervical plexus. On the right side communications go from the 

 sympathetic ganglion to the first and second cerA^ical nerves. 



There is no marked ansa hypoglossi. 



The Phrertic Nerve (P.N) is mainly derived from the fourth 

 cervical nerve, but it receives fine fibres from 3, 2, and 5. 



