Section IV. 



The Oblongata. 



1. General Morphology of the Oblongata. 



In Wustslus, the transition of the architecture of the 

 spinal cord into that of the oblongata is traceable with a 

 degree of definiteness which rarely obta.ins in ottier animals. 

 It is therefore possible to contribute toward the solution of 

 certain probleiris which ve>. the study of this highly specialised 

 region of the mamnialian brain. Only an introductory survey 

 of the entire field will be presented here, leaving the devel- 

 opment of details and the consideration of special questions 

 to the following subsections. 



As the canalis centralis widens into the fourth ventricle, 

 the several structures of the cord lateral to it are pushed 

 into more and more widely divergent positions, retaining, howev- 

 er, essentially the same mutual relations to each other. Con- 

 comitant with this divergence, the dorsal ependyma becomes 

 broadened to form the morphological roof of the fourth ventri- 

 cle(Pig.P,t.c.p. ). 



In approaching the oblongata, the ventral cornua are en- 

 croached upon more and more by commissural fibres until. Just 



(?3) 



