THE SYMPATHETIC NERYE. 571 



own, controlling in some mode and degree, the processes 

 in the interior of the eye. 



Of the fibres that arise in the spinal ganglia, some 

 appear to pass into the posterior branches of the spinal 

 nerves, and to be distributed with them ; the rest pass 

 through the branches by which the spinal nerves commu- 

 nicate with the trunks of the sympathetic, and then entering 

 the sympathetic are distributed with its branches to the 

 viscera. With these, also, a certain number of the large 

 ordinary cerebro-spinal nerve-fibres, after traversing the 

 ganglia, pass into the sympathetic. 



Of the fibres derived from the ganglia of the sympa- 

 thetic itself, some go straightway towards the viscera, the 

 rest pass through the branches of communication between 

 the sympathetic and the branches of the spinal nerves, 

 and joining these spinal nerves, proceed with them to their 

 respective seats of distribution, especially to the more 

 sensitive parts. 



Thus, through these communicating branches, which 

 have been generally called roots or origins of the sympa- 

 thetic nerve, an interchange is effected between ail the 

 spinal nerves and the sympathetic trunks ; all the ganglia, 

 also, which are seated on the cerebral nerves, have roots 

 (as they are called) through which filaments of the cere- 

 bral nerves are added to their own. So that,' probably, 

 all sympathetic nerves contain some intermingled cerebral 

 or spinal nerve-fibres ; and all cerebral and spinal nerves 

 some filaments derived from the sympathetic system or 

 from ganglia. But the proportions in which these fila- 

 ments are mingled are not uniform. The nerves which 

 arise from the brain and spinal cord retain throughout 

 their course and distribution a preponderance of cerelro- 

 spinal fibres, while the nerves immediately arising from 

 the so-called sympathetic ganglia probably contain a 

 majority of sympathetic fibres. But inasmuch as there is 

 no certainty that in structure the branches of cerebral 



