9 



connexion with a nerve-cell, which exerts over it a peculiar influence 

 which enables it to retain its structure," &c. He does not think it 

 proved, however, that all ganglia exert an influence both in a cen- 

 tral and peripheral direction like those of the posterior spinal roots, 

 and indeed experiments have shown that certain ganglia, such as the 

 superior cervical of the sympathetic, exert their sustaining power on 

 the nerve-fibres connected with them, in one direction only. 



The investigation of the effects of section on the optic nerve, 

 which forms the subject of the present communication, promised to 

 yield interesting results on several grounds, and especially as calcu- 

 lated to throw light on the relations of the fibres of the nerve to 

 those of the opposite one in the optic chiasma or commissure, and 

 on the question as to the manner in which they are connected with 

 the brain. 



After some observations on the structure of the optic nerve, the 

 author describes his experimental procedure. To see the nerve 

 whilst operating, and thus be assured that the section was eifected 

 at the desired point, he began by dislocating the eyeball forwards 

 from its socket, while the animal was under the influence of ether. 

 This operation he found could be effected in the rabbit, by simply 

 pressing the eyelids widely apart, and was unattended with any 

 serious disturbance of the functions of the organ. In dogs the 

 operation is more difficult, and occasions more injurious effects. 

 "When the eye is dislocated, its axis is inclined downwards and in- 

 wards, and the optic nerve can be reached without difficulty ; so that 

 it may readily be cut at any desirable distance behind its place of 

 entrance into the eyeball, and may even by moderate traction be 

 broken off immediately before the chiasma. 



After stating various observations which he made on the dislocated 

 eye, the author gives an account of the effects which resulted from 

 section of the optic nerve. The condition of the retina after the 

 operation, was studied during the life of the animal by means of the 

 ophthalmoscope ; and, after death, its structure, as well as that of 

 the optic nerve before and behind the place of section, the chiasma, 

 the optic tracts, and connected part of the brain, was examined 

 with the microscope. 



The elements of the retina, as well as those of Jacob's membrane, 

 were found unaltered four months after the time of section. The 



