594 TROPHIC NERVES IN THE TRIGEMINUS. 



latter and shield it from injuries, and he found that the inflammation and other events occurred 

 at a later date, while, according to Meissner and Biittner, if the eye be protected by means of a 

 complete capsule, the inflammation does not occur at all. There can be no doubt that the loss 

 of the sensibility of the eye favours the occurrence of inflammation. But Meissner, Biittner, 

 and Sciiiff observed that inflammation of the eye occurred when the trophic (most internal) fibres 

 alone were divided, the eye at the same time retaining its sensibility ; this would seem to 

 indicate the existence of trophic fibres, but Cohnheim and Senftleben dispute the statement. 

 Conversely, the sensibility of the eye may be abolished by partial section ot the nerve, yet the 

 eye does not become inflamed (Schif). 'Ranvier, who denies the existence of trophic nerves, 

 made a circular incision round the margin of the cornea through its superficial layers, so as to 

 divide all the corneal nerves. Insensibility of the cornea was thereby produced, but never 

 keratitis. Further, in man and animals, when they are unable to close their eyelids, there is 

 redness with secretion of tears, or slight dryness and opacity of the surface of the eyeball 

 (xerosis), but never the inflammation already described (Samuel). 2. We must also take into 

 consideration the following : Section of the trigeminus paralyses the vaso-motor nerves in the 

 Interior of the eyeball, which must undoubtedly cause a disturbance in the intraocular circula- 

 tion. According to Jesner and Griinhagen, the trigeminus also contains vaso-dilator fibres, 

 whose stimulation is followed by increased flow of blood to the eye, with consecutive excretion 

 of the fibrin -factors and increase in the amount of albumin of the aqueous humour. 3. After 

 section of the nerve, the intraocular tension is diminished (while stimulation of the nerve is 

 followed by increase of the intraocular pressure) (Hippell, Griinhagen). This diminution of the 

 normal tension necessarily must alter the normal relation of the filling of the blood- and lymph- 

 vessels, and also the movement of the fluids, upon which the normal nutrition is largely 

 dependent. 4. Kiihne observed that stimulation of the corneal nerves was followed by con- 

 traction of the so-called corueal-corpuscles. Perhaps the movements of these corpuscles may 

 influence the normal movement of the lymph in the canalicular system of the cornea ( 384); 

 these movements, however, would seem to depend upon the nervous system, so that its destruc- 

 tion is likely to produce disturbance of nutrition. 



[There are three conditions on which the changes may depend (1) mere loss of sensibility, 

 which alone is not sufficient to explain the phenomena ; (2) vaso-motor disturbance, which is 

 excluded by the above facts, and also by the other consideration that, if the fifth nerve be 

 divided and the superior cervical ganglion excised simultaneously, ophthalmia does not occur, 

 and, in fact, excision of this sympathetic ganglion may modify the results of section of the 

 fifth (Sinitzin). Thus, we are forced to (3) the theory of trophic fibres, whose centre is the 

 Gasserian ganglion.] 



Pathological. In cases of anaesthesia of the trigeminus in man, and, more rarely, in severe 

 irritation of this nerve, inflammation of the conjunctiva, ulceration and perforation of the cornea, 

 and finally panophthalmia, have been observed (Charles Bell). This condition has been called 

 ophthalmia neuroparalytica. Samuel found that a similar result was produced by electrical 

 stimulation of the Gasserian ganglion in animals. 



There are other affections of the eye depending upon disease of the vaso-motor nerves, which 

 are quite different from the foregoing, as they never lead to degenerative changes. Such is 

 ophthalmia intermittens (due to malaria), a unilateral, intermittent, excessive filling of the 

 blood-vessels of the eye, accompanied by the secretion of tears, photophobia, often accompanied 

 by iritis and effusion of pus into the chambers of the eye. This condition is regarded as a vaso- 

 neurotic affection of the ocular blood-vessels by Eulenburg. Pathological observations, as well 

 as experiments upon animals, have shown that there is an intimate physiological connection 

 between the vascular areas of both eyes, so that affections of the vascular area of one eye are 

 apt to induce similar disturbances of the opposite eye. This serves to explain the fact that 

 inflammatory processes in the interior of one eyeball are apt to produce a similar condition in 

 the other eye. This is the so-called " sympathetic ophthalmia. " Thus, stimulation of the 

 <iliary nerves, or the fifth on one side, causes dilatation of the blood-vessels not only on its own 

 side but also on the other side as well (Jesner and Griinhagen). The pathological condition of 

 glaucoma simplex, where the intraocular tension is greatly increased, is ascribed by Donders to 

 irritation of the trigeminus. [Increased intraocular tension may be produced by irritation of 

 the secretory fibres contained in the fifth nerve (Bonders), by stimulating the nucleus of the 

 trigeminus in the medulla oblongata (Hippell and Griinhagen), and also reflexly by irritation of 

 the peripheral branches of the fifth, as by uicotin placed in the eye. It is possible, however, 

 that some forms of glaucoma are produced bv diminished removal of the aqueous humour from the 

 eye.] Unilateral secretion of tears, due to 'irritation of the ophthalmic division of the fifth, has 

 been repeatedly observed, but unilateral cessation of tears, due to paralytic conditions, very rarely. 



II. Superior Maxillary Division (fig. 429, e). It gives off 

 1. The delicate recurrent nerve, a sensory branch to the dura mater, which 

 accompanies the vaso-motor nerves, derived from the superior cervical ganglion of 

 the sympathetic, and is distributed to the area of the middle meningeal artery. 



