THE SUPRA-ORBITAL TRUNK. 197 



these branches pierce the frontal bone by separate foram- 

 ina and distribute to the skin of the top of the head over 

 the supra-orbital canal. No sense organs were found in 

 this vicinity. Others pass to the dorsal side of the brain 

 and there in its membranes unite into an intricate plexus 

 which envelops the large pineal vesicle which lies under 

 the skull and over the extreme cephalic tip of the optic 

 lobes and the caudal part of the cerebrum. Some fibres 

 of this plexus pass to the median line cephalad of the 

 epiphysis and there in the meninges unite with a similar 

 fascicle from the other side. The nerve thus formed runs 

 cephalad exactly in the median line between the brain 

 membranes and the exceedingly delicate pallium to the 

 tip of the cerebrum. It then passes dorsad through the 

 cranial cavity to the inner side of the cranial roof in which 

 position it continues forward immediately under the 

 suture of the two frontal bones. Still farther cephalad it 

 lies in the narrow space between the frontal bones and the 

 internasal cartilage, nearly to the tip of the latter. It 

 could be followed beyond the cephalic end of the frontal 

 bones, in the latter part of its course leaving the dorsal 

 surface of the internasal cartilage to run in the sub- 

 cutaneous connective tissue, where it is finally lost. 



This peculiar nerve apparently corresponds to the " in- 

 tra-cranial ascending dorsal twigs of the N. trigeminus and 

 N. facialis," which in Silurus arise from the ganglionic 

 complex cephalad of the r. lateralis V and run forward 

 intra-cranially and under the skin of the head, one branch 

 ramifying over the nasal bone (Stannius, '49, p. 48). 

 Whether it is of sympathetic, communis or general cuta- 

 neous nature, I have no means of deciding positively. As 

 indicated on the plots, I believe that it belongs mainly to 

 the latter component. This, however, needs confirmation. 



