520 THE NERVOUS SYSTEM. 



paralysis due to disease of the spinal cord ; they come on in three 

 or four days after the onset of the paralysis in spite of the most 

 careful attention ; they cannot be explained by vasomotor dis- 

 turbance nor by loss of sensation ; there is, in fact, no doubt they 

 are of trophic origin ; the nutrition of the skin is so greatly im- 

 paired that the mere contact of it with the bed for a few days is 

 sufficient to act as' the exciting cause of the sore." 



The subject is one of great importance, but must be regarded 

 as still unsettled. 



Ganglia of the Trigeminus. Besides the Gasserian ganglion, 

 there are, in connection with the fifth nerve, four ganglia which 

 are by some writers described as a part of the sympathetic system. 

 They are the ciliary or ophthalmic, the sphenopalatine or MeckePs, 

 the otic or Arnold's, and the submaxillary. 



The ciliary ganglion belongs, according to some authorities, to 

 the third rather than to the fifth nerve. It is not larger than the 

 head of an ordinary pin, and is situated in the orbit. The 

 branches by which other nerves communicate with it are called its 

 " roots " ; of these there are three : The sensory, from the ophthal- 

 mic division of the fifth ; the motor, from the motor oculi ; and 

 the sympathetic, from the cavernous plexus of the sympathetic. 

 The nerves that go off from it are the short ciliary nerves, which, 

 joining with the long ciliary nerves, form the nasal branch of the 

 ophthalmic division, and together they are distributed to the ciliary 

 muscle, the iris, and the cornea. These nerves supply motion 

 to the sphincter and dilator pupillse, sensibility to the iris, choroid, 

 and sclerotic, and vasomotor influences to the blood-vessels of 

 the iris, choroid, and retina. If the trophic influerfce already 

 spoken of exists, it must be conveyed to the eye through the 

 ciliary nerves. 



The sphenopalatine or Meckel's ganglion, which is the largest 

 of the four, is situated in the sphenomaxillary fossa. This gang- 

 lion also has three roots : The sensory, sphenopalatine, from the 

 superior maxillary division of the fifth ; the motor, large superficial 

 petrosal nerve from the facial ; and the sympathetic, large deep 

 petrosal nerve from the carotid plexus of the sympathetic. The 

 Vidian nerve is made by the union of these two latter nerves. 

 The nerves from this ganglion are distributed to the posterior por- 

 tion of the nasal passages and the hard and soft palate, giving 

 them sensibility ; to the levator palati and azygos uvulae, giving 

 them the power of motion ; and to the blood-vessels of this 

 region. 



The otic or Arnold's ganglion is situated on the inner side of the 

 inferior maxillary division of the fifth, just below the foramen 

 ovale. It likewise has three roots : The sensory, from the inferior 

 maxillary and glossopharyngeal ; the motor, from the facial and 

 inferior maxillary ; and the sympathetic, from the plexus around 



