336 



HISTOLOGY. 



geminus and intermedius (facial) and to the ventral root which makes the 

 abducens. The pons transmits the ascending and descending fibers 

 between the cord and the anterior portion of the brain, together with 

 fibers to and from the medulla. Many fibers of the pons pass through the 

 lateral wall of the brain-tube into the cerebellum, forming a large bundle 

 on each side, called the branchium pontis (Fig. 391). The cerebellum also 

 receives on each side a bundle from the anterior part of the brain, the 

 branchium conjunctivum, and another from the medulla, the restiform body. 

 These three bundles not only contain fibers to the cerebellum but also 

 those passing from it. The cerebellum (Fig. 393) is a large lobular mass 



inf. 



FIG. 391. A, DORSAL AND B, VENTRAL VIEW OK THE POSTERIOR PART OF THE ADULT BRAIN. THE 

 CEREBELLUM AND ROOF OF THE FOURTH VENTRICLE HAS BEEN REMOVED FROM A. 



b. c., Brachium conjunctivum; b. p., brachium pontis; c. m., corpus mamillare ; c. p., cerebral peduncle; 

 c. q. a. and c. q. p., anterior and posterior corpora quadrigemina; inf., infundibulum; med., medulla; 

 ol., olive; p., pons; p. b., pineal body; pyr., pyramid; r. b., restiform body; ven., floor of fourth ven- 

 tricle. The nerves are oc., oculomotor; tr., troclear; tri., trigeminal; abd., abducens; int., inter- 

 medius, fa., its facial portion; ac., acoustic; gl., glossopharyngeal; va., vagus, ace., its accessory 

 portion; hy., hypoglossal. 



of nerve tissue, consisting of an arborizing medulla of white substance, and 

 a cortex composed of special forms of nerve cells. 



The isthmus presents on its dorso-lateral surfaces the brachia 

 conjunctiva. Beneath the floor of the central cavity or aqueduct it 

 contains the motor cells from which the fibers of the trochlear 

 nerve arise. After crossing to the opposite side above, the aqueduct, 

 these fibers emerge from the dorsal surface of the isthmus. Ventrally 

 the tracts of fibers extending between the hind-brain and the fore-brain 

 form projecting elevations which diverge as they pass forward; the eleva- 

 tions are called the peduncles of the cerebrum. 



The mesencephalon forms dorsally four rounded elevations, the 

 corpora quadrigemina. The superior or anterior pair receives fibers from 



