642 'Journal of Comparative Neurology and Psychology. 



ago, fully expecting to find it a motor bundle as described by Cajal, 

 Wallenberg and others, I have been unable to find any good evidence 

 for this interpretation. 



I have pointed out (1905, 1906) that the existence of a general 

 sensory (cutaneous) column extending up into the tectum mesen- 

 cephali is a strong support for the theory of primitive functional 

 divisions of the nervous system with which all readers of recent 

 literature have become familiar. This general interpretation rests 

 upon the demonstration of true axones of the ganglion cells ending 

 in the tectum and is more secure than before so far as the primitive 

 brain is concerned. The hypothesis suggested above implies that the 

 tectum mesencephali in mammals has largely lost its primary general 

 sensory function. 



ABBREVIATIONS USED IN ALL THE FIGURES. 



a,J),c, bun*es of the radix mesencephalica. 



Aq., Aqueduct. • 



hr.. €071]., brachium conjuuctivum. 



chlm., cerebellum. 



c. p., coinmissura posterior. 



c. v., corpus restiforme. 



dec. vel., decussatio veli. 



ep., epiphysis. 



lem. lat., lemniscus lateralis. 



loc. ccei:, locus coeruleus. 



nuc. coch., nucleus cochlearis. 



nuc. haJ)., nucleus habenulse. 



s., sensory nucleus of trigeminus. 



s. 1., sulcus limitans. 



sg. or suJ). gel., substantia gelatinosa. 



ter. gust., tertiary gustatory tract. 



tr. sp. V, tractus spinalis trigemini. 



V chllr, cerebellar fibers of trigeminus. 



V g, ganglion trigemini. 



y mes, radix mesencephalica trigemini. 



V mot, motor root of trigeminus. 



y mot. o)\, decussating fibers of motor trigeminus. 



V mot. nuc., motor nucleus of trigeminus. 



V se7is, sensory root of trigeminus. 

 VIII c, nervus cochlearis. 



VIII vest., nervus vestibularis. 



Yen, foiu'th ventricle. 



V, 10, X. y, s, bundles of the motor root of the trigeminus. 



