686 TRIGEMINAL NERVE. 



The results described take place, however, only when the nerve is divided in 

 the Gasserian ganglion or peripherally (but not centrally) from it. The cause of 

 the nutritive disturbances is dependent upon the ganglion-cells. In an estimation 

 of the views as to the trophic libers the following points must be taken into con- 

 sideration: (i) Division of the trigeminus renders the entire eye anesthetic. The 

 animal, therefore, is not conscious of direct injury and makes no effort to escape 

 it. Also, adherent dust and mucus are no longer removed reflexly by closure of 

 the eyelids. In general, in consequence of absence of the reflex, the palpebral 

 fissure is wider and the eye is thus exposed to many injurious influences and to 

 desiccation. Reflex secretion of tears also is wanting. When Snellen attached in 

 front of the eye the sensitive auricle of the rabbit, through whose sensibility it 

 avoided injury, the inflammation of the eye occurred much later. On placing a 

 perfectly secure protecting capsule in front of the eye the inflammation was entirely 

 prevented. The same result was observed when Gudden sutured the freshened 

 margins of the lids in rabbits anql permitted them to grow together. The cornea 

 can be kept intact also by scrupulous cleanliness. There can, therefore, be no 

 doubt that the loss of the sensibility of the eye favors the occurrence of inflamma- 

 tion. Efforts were made, further, to discover the trophic nerves and to divide 

 them separately. As Meissner, Biittner, and Schiff observed the eye to become 

 the seat of inflammation after dividing only the trophic (innermost) fibers of the 

 trigeminus, the eye retaining its sensibility, the existence of trophic fibers might 

 be considered as demonstrated; but Cohnheim and Senftleben contradict these 

 facts. Conversely, the sensibility of the eye may be lost in consequence of partial 

 injury of the nerve, and the eyeball does not become inflamed. Ranvier, w T ho 

 denied the existence of trophic nerves, incised the cornea in a circular manner 

 through its superficial layers, at the same time dividing the nerves, all of which 

 are present in this situation. There resulted anesthesia, but never keratitis. 

 Further, in men and animals in which inability to close the eyes exists, redness 

 with flow of tears or slight desiccation and cloudiness of the surface of the eyeball 

 (xerosis) set in, but never such a destructive inflammation as that described. 



(2) The following factors, to which hitherto little reference has been made, 

 should further be taken into consideration : Division of the trigeminus paralyzes the 

 vasomotors in the interior of the eyeball, and in consequence derangements in the 

 circulation of the blood must take place. According to Jessner and Griinhagen 

 the trigeminus also transmits vasodilator fibers to the eye, irritation of which 

 causes increased flow of blood to the eye, with consecutive elimination of fibrin- 

 factors and increase in the amount of albumin in the aqueous humor. 



(3) After division of the nerve the tension of the eyeball is diminished. Con- 

 versely, irritation is followed by considerable increase in the intraocular pressure. 

 The reduction in intraocular pressure must, naturally, alter the normal relation 

 between the fulness of the blood-vessels and the lymphatic channels and the move- 

 ment of the fluids within them, upon which the normal nutrition in large measure 

 depends. 



(4) W. Kiihne observed movement of the corneal corpuscles on irritation 

 of the corneal nerves. It does not appear impossible that the movement of 

 these corpuscles has an influence upon the normal movement of the fluid in 

 the canalicular system of the cornea. If, however, it were dependent upon the 

 nervous system destruction of the latter would be followed also by nutritive dis- 

 turbances. As a matter of fact, Gaule observed after division of the nerve that 

 the corneal corpuscles were partly shrunken, partly enlarged, and that the epithe- 

 lium of the cornea was partly necrotic, partly in a condition of proliferation. 



Pathological. In man, inflammation of the conjunctiva, ulceration and per- 

 foration of the cornea and finally panophthalmitis. which is designated neuro- 

 paralytic ophthalmia, have been observed after trigeminal anesthesia and less com- 

 monly in association with profound irritative states of the fifth nerve. Samuel 

 was able to induce the same effects in animals by electrical stimulation of the Gas- 

 serian ganglion. 



The affections of the eye due to disorders of the vasomotor nerves are 

 entirely different than those described, as they never give rise to degenerative 

 processes, as does division of the trigeminus. In this category belongs intermit- 

 tent ophthalmia, a condition of unilateral, intermittent marked injection of the 

 ocular vessels, due to malarial influences, associated with flow of tears, photo- 

 phobia, often also with iritis and suppuration in the chambers of the eye, which 

 was first considered by Eulenburg and Landois as a vasoneurotic disorder of 

 the ocular vessels. Pathological observations, as well as experiments on animals, 



