290 HEAD AND NECK 



or three filaments, which convey to the ganglion its sensory 

 and secretory roots, whilst the anterior connecting branch must 

 be looked upon as a twig given by the ganglion to the lingual 

 nerve. 



In common with the other ganglia developed in connection 

 with the branches of the trigeminal nerve, this ganglion has 

 three roots viz. (i) a sensory root from the lingual nerve ; (2) 

 a secretory root from the chorda tympani ; and (3) a sympathetic 

 root from the plexus around the external maxillary artery. 



From its lower border several minute twigs proceed, and 

 these are distributed (i) to the submaxillary gland and 

 duct ; (2) to the sublingual gland from the branch which 

 it gives to the lingual nerve ; and (3) to the mucous mem- 

 brane of the mouth. 



Nervus Hypoglossus. This nerve has been traced in the 

 dissection of the anterior triangle to the point where it 

 disappears under cover of the mylo-hyoid muscle (p. 231). 

 It is now seen passing anteriorly upon the hyoglossus muscle, 

 above the hyoid bone and below the level of the deep 

 part of the submaxillary gland. At the anterior border of 

 the hyoglossus it gains the surface of the genio - glossus 

 muscle, into the substance of which it sinks; and finally 

 it breaks up into branches which supply the muscular sub- 

 stance of the tongue. Upon the hyoglossus muscle it is 

 accompanied by a vena comitans. 



The branches which spring from the hypoglossal nerve in 

 this region are very numerous, and are entirely distributed to 

 muscles. It supplies (i) thestylo-glossus; (2) the hyoglossus; 

 (3) the genio-glossus ; (4) the genio-hyoid ; and (5) the 

 intrinsic muscles of the tongue. 



In addition, it communicates freely with the lingual 

 nerve. The more apparent of these connections take place 

 in the form of one or more loops in relation to the anterior 

 border of the hyoglossus. Other communications with the 

 same nerve are effected in the substance of the tongue. 



Reflection of the Hyoglossus. The hyoglossus should now be 

 carefully detached from the hyoid bone, and thrown upwards towards 

 the tongue. In doing this there is no need to divide the structures 

 which lie upon its surface. By the reflection of this muscle the follow- 

 ing structures will be fully displayed (i) the profunda linguae artery 

 and the veins which accompany it ; (2) the dorsales linguae arteries and 

 veins ; (3) the posterior part of the genio-glossus ; (4) the origin of the 

 middle constrictor of the pharynx ; and (5) the attachment of the stylo- 

 hyoid ligament. 



