Johnston, Nerves of Petromyzonts. 



605 



one end plate is formed a fiber continues to form others. I have 

 not seen his second paper (1905) with figures and do not know 

 whether he has seen the simple motor endings in the myotome 

 described in this paper. 



2. The distribution of the branchial nerves to the two demi- 

 branchs adjacent in each case to the arch in which the nerve runs. 

 Both sensory and motor fibers take part in this arrangement. 

 This means that in the lamprey each nerve supplies one whole 

 gill, while in gnathostomes each nerve divides into pre- and post- 



FiG. 31. A medium and two fine fibers in a dorsal nerve root for comparison with motor fibers, etc., 

 sp.c, spinal cord; vert., wall of spinal canal. Magnification, 375 diameters. 



trematic rami and supplies the two demibranchs bounding a gill 

 slit. This change is possibly brought about by a downgrowth of 

 the visceral ramus into the next anterior gill arch. 



3. The large size of the sympathetic trunk and its evident 

 importance in the branchial region; the distribution of sympathetic 

 fibers in the ventral branchial region by way of the VII nerve; 

 and the endings of sympathetic fibers in the walls of blood vessels. 

 The bodies of most of the sympathetic neurones must be situated 

 in the facial ganglion or within the brain. From this condition in 



