88 TRANSACTIONS OF THE [jAN. 11, 



The examination of the deep cervical loop and hypoglossal 

 anastomosis in the Cynomorpha throws important light on the 

 character and mode of the communication, and on the question 

 of the nerve supply of the individual hyoid muscles. 



Fig. VI. of Plate YII. represents the plan of the right deep 

 cervical ansa and of tlie infra-hyoid muscular distribution in a 

 female specimen of Macacus f^hesus (Body weight 2,546 grms. 

 Brain weight 73 grms.) 



The periphei'al communicating branch of the First Cervical 

 nerve (Plate II., Fig. I., 3) enters the sheath of the Hypoglossal 

 immediately after the exit of the latter nerve from tlie skull at the 

 jioint where it crosses in front of the Vagus. It leaves the 

 Hypoglossal in front of the External Carotid arter}^ descends 

 obliquel}' on the outer surface of the sheath of the vessel, and is 

 joined, near the bifurcation of the Common Carotid, by the com- 

 municating branch from the Second and Third Cervical nerves. 



The Second Cervical nerve gives off three short internal 

 branches. Two of these (Plate VII., Fig., VI., 1, 3) supply the 

 anterior prevertebral muscles; the third (Fig. VI., 2) passes 

 to the Vagus. 



The remainder of the nerve continues downward in two divi- 

 sions ; one of these joins an ascending branch from the Third 

 cervical to form the communicating loop to the deep cervical 

 ansa ; the other descends to the main trunk of the Third Cervical 

 and is continued peripherally into the Auricularis magnus. 



The point of communication of the branch from the First Cer- 

 vical and the branch from the Second and Third Cervical reveals 

 the structure of the cervical ansa completel3\ The nerves are 

 merely loosely connected by a thin fascial investing sheath and 

 are easily separated from each other. Above or in front of the 

 point of communication the ventral limb of the loop is composed 

 of two nerve trunks passing in opposite directions. The as- 

 cending trunlv, derived from the Second Cervical nerve, passes 

 upward to the point where the loop is connected with the Hypo- 

 glossal, enters the sheath of the latter nerve, and continues in 

 a peripheral direction, giving one branch to the Thyro-hyoid 

 muscle, the remainder passing with the Hypoglossal nerve to the 

 tongue proper, to supph' the Genio-hyoid muscle. 



The descending trunk of the ventral limb of the loop consists 

 of the entire contribution of the First Cervical nerve, reaching 

 its distribution b3' travelling in the sheath of the Hj-poglossal. 

 Leaving this sheath at the intersection with the Carotid vessels 

 the nerve descends in the ventral limb of the loop to the " point 

 of communication." Here the nerve crosses the ascending 

 branch derived from the Second Cervical nerve, being only 



