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cells ill selacliii, I lie <j,Teiitest iiuiiibers on a ci'oss section are met 

 with in the third and fonrth fifth parts of the sagittal dimension of 

 the nucleus. There are no important differences between the number of 

 cells situated before and behind it. 



The wa>' in which the respective mesenc. roots leave the brain- 

 stem is different in these two orders of animals, and differs also from 

 that in the higher animals. In sci/1/üfjii cmüciila T found relat ionshijis 

 of a very peculiar nature which may in iirinciple be of imjiortance 

 in solving the problem alluded to at the commencement of this article. 



After the axones have united latei'o-dorsallj to the aquaeduct 

 to a comparativel}' compact bundle, and |)roceeded distally, we sec, 

 frontally to the entrance of the sens, trigeminns root, where the gan- 

 glion Gasseri (G. G.) is visible, several fibres separate from this bundle 

 and pass to the jieripherj of the oblongata, where it leaves it (fig. 4). 



Fig, 4. Scyllium canicula. 



Immediately ventrally to this, but clearly se])arate from it, the most 

 frontal stem of the motor trigeminus root is seen in its most medial 

 part. This last stem is followed 4 sections further caudal ly by a 

 similar new stem of the motor V running at exactly the same height, 

 still accompanied by the out-going mesenc. root-fibres, which end 

 about 250 ft more dorsally (fig. 5). Neither of the two preparations 

 show any union with the still extra-bulbar sens. V nerve (on which 

 the gang. Gasseri is visil)]e). 



The following — more caudal — section no longer shows any 

 out-going mid-brain fibres, while the motor V stem lies relatively 

 at the same place. Dorsally to this last one sees the rosiduai'y mesenc. 

 root cut slantwise (fig. G). Six sections further distally, where only the 



