io68 



HUMAN ANATOMY. 



The inferior cerebellar peduncle is the most direct path by which the cerebellum 

 is connected with the medulla and the spinal cord. In addition to the tracts 

 originating in the cord and destined for the cerebellum (the direct cerebellar and 

 possibly part of Cowers' tract), it comprises probably fibres passing in both direc- 

 tions; that is, from the cells within the medulla to the cerebellum, and from the 

 cerebellar cells to the medulla. A more detailed account of these components will 

 be given in connection with the structure of the medulla (page 1072). Upon close 

 inspection of the surface of the medulla, the direct cerebellar tract is seen as an 

 obliquely coursing band that at the lower level of the olive leaves the lateral area and 

 gradually passes backward, over the upper and outer end of the Rolandic tubercle, 

 to join the restiform body, within which it continues its journey to the cerebellum. 

 The anterior superficial arcuate fibres also enter the restiform body, after sweeping 

 around the inferior pole of the olive, or crossing its surface, and the upper part of the 

 funiculus of Rolando. Additional contributions, the posterior superficial arcuate 

 fibres, proceed to the restiform body from the gracile and cuneate nuclei of the 

 same side. Just before bending backward to enter the cerebellum, the restiform 

 body is crossed by a variable number of superficial strands, the striae acusticae, 

 ihat may be traced from the floor of the fourth ventricle and around the inferior 

 peduncle to the cochlear nucleus. 



INTERNAL STRUCTURE OF THE MEDULLA OBLONGATA. 



As already pointed out, the correspondence between the spinal cord and the 

 medulla is only superficial, sections across the medulla revealing the presence of con- 

 siderable masses of gray matter and important tracts of nerve-fibres not represented 



FIG. 919. 



Fig. 92* 



Fig. 921 

 Fig. 920 



Ventral (A ) and dorsal (S) aspects of brain stem, showing levels of sections which follow. 



in the cord, as well as the rearrangement, modification or disappearance of spinal 

 trarm \\hidi an- prolonged into the bulb. In consequence, the medulla, even at 

 its lower end, presents new features, and towards its upper limit varies so greatly 

 in>m the cord that t>ut slight resemblance to the latter is retained. The character- 

 istic features displayed by transverse sections of tin- medulla at different levels 

 depend upon tin- changes induced by four chief factors: (i) the decussation of 

 the pyramids, (z> the appearance of the dorsal nuclei, (3) the production of the' 

 formatio n-ticularis, and (4) the opening out of the fourth ventricle. 



