THE TEGMENTUM AND THE PEDUNCLE OE THE MIDBHAIN. 



305 



contains, besides the fibers which connect the ocular muscles among them- 

 selves, also fibers for the other cranial nerves. 



The posterior longitudinal fascicle sends its most anterior fibers much 

 farther forward than to the nucleus of the oeulo-motorius. In the central 

 gray matter just anterior to the beginning of the aqueduct is a collection of 

 large ganglion-cells from which a number of such fibers arise, — nucleus 

 fasciculi longitudinalis superioris (see Fig. 179). This nucleus is demon- 

 strable in all vertebrates. In mammals it lies in those planes which ven- 

 trally intersect the posterior part of the corpus mamillare. Inasmuch as it 

 is found in all vertebrates, and always from the interbrain to the region 

 of the anterior columns of the spinal cord, it must be recognized as one of 



ff-'-HiiiiMiinniin'ttiirimiiTifi^ifinuuiijmjj^^ 1)1"' 

 Aquaeducfus ^ 



Vent 







Fig. 197. — Longitudinal, nearly median, section through the midbrain of a 

 twenty-eight weeks' human fetus, partly through the outer wall of the aque- 

 duct, showing the end of that part of the posterior longitudinal fascicle which 

 belongs to the nucleus of the oculo-motorius. Vierhilgelplatte, Midbrain-plate. 

 Hint. Ldngsbiindel, Post. long, fascicle. Hirnschenkel, Pes pedunculi. 



the fundamental features of the drain. (See also Chapter VI, Figs. 43 

 a,nd 44, and text). 



The boundaries of the numerous systems of fibers to be found in the 

 region of the corpora quadrigemina can only be sharply differentiated 

 through studying the development of their medullary sheaths. In Fig. 198 

 we have a section from a nine months' human fetus, through the anterior 

 ■quadrigeminal bodies just at the posterior commissure. All of the fibers, 

 which at this stage of development are medullated, are stained with 

 hsematoxylin. 



