102 H. V. NEAL 



Finally, the fact the fibers of the • ophthalmicus profundus 

 enter the medulla in common with those of the trigeminus will 

 not seem to morphologists a serious objection to the comparison 

 of the profundus with spinal somatic sensory nerves, since it 

 would seem a matter of indifference whether somatic sensory 

 fibers enter the brain by one path or another. In the case of 

 the union of the roots of once independent ganglia we seem to 

 have to do with a particular case under the general principle 

 of the centralization of function in the region of the medulla. 

 Analogous instances may be found in all organ systems. 



Taking all the facts into consideration there appears to be 

 no insuperable objection to the view that the ophthalmicus 

 profundus is serially homologous with spinal somatic sensory 

 nerves. 



h. How is the relation of the oculomotorius to the ciliary ganglion 

 to he interpreted? The comparison of the profundus nerve with 

 spinal somatic sensory nerves is still further strengthened by 

 the evidence of the relations with the ciliary ganglion which 

 have been found above to be those of a somatic motor nerve to a 

 sympathetic ganglion. The facts which prove the sympathetic 

 character of the ciliary anlage have already been stated above 

 and need no restatement. The ciliary ganglion of Squalus is 

 to be regarded as partly, if not exclusively, a sympathetic gan- 

 glion. So that in its relations with a sympathetic ganglion the 

 oculomotor forms no exception in the series of morphologically 

 similar sortiatic motor nerves. 



c. Hoiv may the relation of the oculoynotorius to four eye muscles 

 be best interpreted? The distribution of the oculomotor to four 

 muscles may appear to require interpretation. The fact, how- 

 ever, that all of these muscles are derived from a single myotome 

 by a process of splitting and that this splitting is correlated with 

 the considerable enlargement of the eye-ball; furthermore, that 

 the innervation of more than one muscle by a single somatic 

 motor nerve is by no means exceptional, brings these relations 

 also into line with those of spinal somatic motor nerves. The 

 oculomotor, therefore, in its histogenesis and in its relations to 

 a somatic sensory ganglion, to a sympathetic ganglion and to 



