NERVOUS SYSTEM. VERTEBUATA. P. 1 



cord behind. The nerves that arise from this region of the 

 cord are stouter than the rest of the spinal norvcM. In 

 minute structure, these eminences agree with the iu<-t;n 

 enlargements at the anterior end of the cord in the Gur- 

 nards. In both cases they are due to an iiim-a^- in tin- 

 dorsal horns of the grey matter of the cord <-<>rn^|,<nnlinj{ 

 to an increase in the development of the sensory roots of 

 the anterior spinal nerves. The cleft between th< 

 prominences is occupied by a mass of giant ganglion-n-lU, 

 whose axis cylinders have been traced to the root- of the 

 trigeminal. They are probably connected with tin- inn 

 tion of the epidermal processes upon the head of the li.-h. 

 The cord rapidly diminishes in size posteriorly, until upon 

 a level with the 3rd or 4th vertebra it is represented hy ;i 

 delicate thread lying in the centre of a " cauda equina " 

 formed by the roots of the posterior spinal nerves. The 

 actual posterior limit of this terminal filament is not very 

 clear in the specimen, but it apparently stops at .-OMM- 

 distance from the extremity of the tail. The filament is 

 indicated by bristles and black paper placed beneath it. 



Another example of the spinal cord of this fish i> >ho\vn 

 in D. 100. 0. C. 1347 K. 



Fritsch, Arch. f. Mikr. Anat., Bd. xxvii. 1886, p. 13. 



D. 755. A Gurnard (Trigla hirundo) with the brain and spinal 

 cord exposed from above. The cord is remarkable for a 

 series of five pairs of rounded eminences upon its dorsal 

 surface close behind the medulla. The first two pair- 

 relatively insignificant, but the last three an- lar#- and of 

 about equal size. The eminences consist of grey matter 

 with a superficial layer of small ganglion-cells. Like the 

 sensory cranial nerve-nuclei, which they much ren-mhle in 

 structure, they are formed by a great development of the 

 grey matter of the anterior horns, arising in response to a 

 demand for increased nerve-supply. They give origin 

 the dorsal roots of the three anterior pairs of spinal ner 

 These (especially the roots of the 3rd pair) are of 

 size and supply the free digitiform rays of 

 fins. 

 Ussow, Arch. Biol. t. iii. 1882, |.. G 



