CoGHiLL, Cranial Nerves of Anibly stoma. 235 



emerge from the medulla at its extreme lateral margin. This 

 root, in some cases, becomes closely applied to the caudal side 

 of the third root of the vagus as the latter leaves the medulla, 

 but, in other cases, it meets the third root near the ganglion. 

 As it comes in touch with the ganglion it turns caudad par- 

 tially embedded in the mesial portion of the complex. At the 

 transverse level of the origin of the branchial trunks of the 

 vagus, the fourth vagus root begins to turn laterad into the 

 complex, and beyond this point can be traced as a continuous 

 fiber band among the ganglion cells until it enters the truncus 

 visceralis, of which it forms the motor component. It is prob- 

 ably accompanied, however, by the motor component of the 

 third root, as described above. 



B. THE RAMI OF THE VAGUS AND GLOSSOPHARYNGEUS. 



/. — J he Triinc2is Glossophatyngeus. 



The glossopharyngeal trunk arises from the latero-ventral 

 angle of the anterior portion of the IX+X ganglionic complex. 

 It contains all the neurones of the glossopharyngeal root and a 

 small general cutaneous component from the third root of the 

 vagus. 



The general course of the nerve {IXt.) varies greatly. In 

 the adult it turns abruptly cephalad around the lateral border of 

 the ear capsule and then turns caudad to the first branchial 

 arch. In the larvae it passes laterad, to the m. levator arcus 

 branchii primi. It usually penetrates this muscle, but in some 

 cases it passes around the posterior end of this muscle to reach 

 the distal end of the first branchial arch. When it penetrates 

 the levator muscle it passes caudad laterally of it, across the 

 lateral surface of the first epi-branchial bar, then ventrad be- 

 tween the bar and the m. cerato-hyoideus externus. It then 

 passes cephalad into the first branchial arch. 



The r. communicans IX^X ad VII [com. IX-^X ad VII) 

 arises from the glossopharyngeal trunk immediately outside the 

 ganglion. It is made up of general cutaneous and communis 

 fibers. It passes cephalad around the lateral border of the ear 

 capsule, then laterally of the suspensorio-stapedial ligament. A 



