872 NEUROLOGY 





of the mid-brain. The axons come from large cells in the stratum opticum and 

 stratum lemnisci and sweep ventrally around the central gray matter of the aque- 

 duct, cross the raphe in the fountain decussation of Meynert and turn downward 

 in the tegmentum in the ventral longitudinal bundle. Some of the fibers do not 

 cross in the raphe but pass down on the same side ; it is uncertain whether they come 

 from the superior colliculus of the same side or arch over the aqueduct from the 

 colliculus of the opposite side. The tectospinal fasciculus which comprises the 

 major part of the ventral longitudinal bundle passes down through the tegmentum 

 and reticular formation of the pons and medulla oblongata ventral to the medial 

 longitudinal bundle. In the medulla the two bundles are more or less intermingled 

 and the tectospinal portion is continued into the antero-lateral funiculus of the 

 spinal cord ventral to the rubrospinal fasciculus with which some of its fibers are 

 intermingled. Some of the fibers of the tectospinal fasciculus pass through the red 

 nucleus giving off collaterals to it, others are given off to the motor nuclei of the 

 cranial nerves and in the spinal cord they terminate either directly or indirectly 

 by terminals and collaterals among the nuclei of the anterior column. Since the 

 superior colliculus is an important optic reflex center, this tract is probably con- 

 cerned in optic reflexes; and possibly also with auditory reflexes since some of the 

 fibers of the central auditory path, the lateral lemniscus, terminate in the superior 

 colliculus. 



The vestibulospinal fasciculus (part of the anterior marginal fasciculus or Loewen- 

 thal's tract) situated chiefly in the marginal part of the anterior funiculus is mainly 

 derived from the cells of the terminal nuclei of the vestibular nerve, probably 

 Deiters's and Bechterew's, and some of its fibers are supposed to come from the 

 nucleus fastigius (roof nucleus of the cerebellum) . The latter nucleus is intimately 

 connected with Dieters's and Bechterew's nuclei. The vestibulospinal fasciculus 

 is concerned with equilibratory reflexes. Its terminals and collaterals end about 

 the motor cells in the anterior column. It extends to the sacral region of the cord. 

 Its fibers are intermingled with the ascending spinothalamic fasciculus, with the 

 anterior proper fasciculus and laterally with the tectospinal fasciculus. Its fibers 

 are supposed to be both crossed and uncrossed. In the brain-stem it is associated 

 with the dorsal longitudinal bundle. 



The pontospinal fasciculus ( Bechterew) arises from the cells in the reticular forma- 

 tion of the pons from the same and the opposite side and is associated in the brain- 

 stem with the ventral longitudinal bundle. In the cord it is intermingled with the 

 fibers of the vestibulospinal fasciculus in the anterior funiculus. Not much is known 

 about this tract. 



There are probably other descending fasciculi such as the thalamospinal but not 

 much is known about them. 



MENINGES OF THE BRAIN AND MEDULLA SPINALIS. 



The brain and medulla spinalis are enclosed within three membranes. These 

 are named from without inward: the dura mater, the arachnoid, and the pia mater. 



The Dura Mater. 



The dura mater is a thick and dense inelastic membrane. The portion which 

 encloses the brain differs in several essential particulars from that which surrounds 

 the medulla spinalis, and therefore it is necessary to describe them separately; 

 but at the same time it must be distinctly understood that the two form one com- 

 plete membrane, and are continuous with each other at the foramen magnum. 



The Cranial Dura Mater (dura mater encephali; dura of the brain) lines the 

 interior of the skull, and serves the twofold purpose of an internal periosteum 



