MORPHOLOGY OF EYE MUSCLE NERVES 105 



The foundation for Gast's speculation consists, primarily, in 

 the evidence of close or intimate relations with a cerebro-spinal 

 ganglion. But if such logic were rigidly followed, it would be 

 necessary to regard every spinal somatic motor nerve as a lateral- 

 horn (splanchnic motor) nerve, since close and intimate relations 

 with a cerebro-spinal ganglion is characteristic of spinal somatic 

 motor nerves in Squalus. 



The supposed demonstration of the participation of sensory 

 elements in the genesis of the oculomotor is one that would 

 satisfy only on the basis of a strong presumption in its favor. 

 The position of the nidulus of the oculomotor and its peripheral 

 distribution create a strong presumption against the assumption. 

 Spindle-shaped cells lying in the mesenchyma between the pro- 

 fundus ganglion and the oculomotor nerve are not necessarily 

 neuroblasts. Spindle-shaped cells may be found almost any- 

 where in the mesenchyma. Even if it be admitted that the 

 evidence that these cells are in the process of migration toward 

 the oculomotor anlage is convincing, Gast does not know their 

 fate. They may form neurilemma or they may enter the sympa- 

 thetic or what-not. Their later histogenesis is wholly unknown. 

 Gast has not used neurofibrillar stains in order to ascertain their 

 neuroblastic character. It would be surprising if morphologists 

 accepted Gast's conclusion upon the basis of the slight evidence 

 he is able to present in its favor. 



The evidence in favor of the view that the oculomotor nerve 

 is a mixed nerve homologous with typical cranial nerves such as 

 the trigeminal is so unconvincing, while the evidence of its histo- 

 genesis and its central and peripheral relations so strongly sup- 

 port the supposition that it is a somatic motor nerve, as the 

 majority of morphologists have beheved, that the acceptance of 

 the latter seems unavoidable. This view at least does not re- 

 quire support from such an unproved assumption as the second- 

 ary fusion of lateral and ventral motor niduli. 



