Literary Notices. cxiii 



The first part deals with the transition between the cord and the 

 medulla and opens with a detailed description of the histological 

 structure of the cervical cord. As the cord passes into the medulla, 

 the first significant alteration is the presence of more numerous 

 medullated fibres in the grey matter. The ventral commissure in- 

 creases in size, more fibres passing to the lateral columns and some 

 even to the dorsal columns. The dorsal commisure also becomes 

 stronger, sending part of its fibres laterally and dorsally in such a 

 way as to isolate the dorsal cornu from the rest of the grey matter. 

 Other fibres of the dorsal commissure pass further ventrad to the later- 

 al columns. 



The alterations in the white substance appear first laterad of the 

 dorsal cornu and dorsad of the lateral cerebellar tracts, where the 

 longitudinal fibres begin to turn ventro-laterad Gradually the lateral 

 columns begin to assume the same direction, until finally they reach 

 the ventral surface and cross' the median line under the ventral col- 

 umns, thus closing the ventral fissure. Some of these fibres enter the 

 ventral columns and there assume a longitudinal direction again. 

 Meanwhile the dorsal columns have diminished in size and in density 

 and part of their fibres have gradually turned laterad and pursued the 

 course followed by the fibres of the lateral columns. At this level 

 the ganglion cells of the ventral cornu begin to send their fibres to 

 the hypoglossus instead of to the first cervical nerve, and the nidulus 

 of the vagus appears. 



The lateral columns receive contributions from almost all of the other 

 columns and present a very complicated aggregation of fibres. 

 After crossing either in the ventral commissure or beneath the ven- 

 tral columns, they take up their former axial direction somewhat ven- 

 trad of the position occupied by the uncrossed fibres. Some of these 

 crossed fibres, however, pass farther dorsad and enter the restiform 

 tracts. The latter also receive some fibres from the uncrossed portion 

 of the lateral columns of the same side. The lateral columns supply 

 the optic lobes; from them also pass at least a part of the fibres of the 

 pedunculi cerebri. The exact course of the pyramidal bundles in 

 birds is still an open question. 



The dorsal columns send a great part of their fibres either cross- 

 ed through the ventral commissure or directly to the lateral columns. 

 Of the remainder which retain their dorsal position, the lateral part 

 enters into relations with the ascending trigemimus root and. after 

 crossing, apparently with the fasciculus solitarius ; the median part 

 is cqnnected with the cerebellum and the acusticus group. 



