The true neuralgias in which syphilis only plays the part of secondary factor, and which have been referred to in Part I. of this work, may depend for their exciting cause on local syphilitic processes, affecting either the peripheral distribution, the main trunk or the central origin of a sensory nerve; but I have pointed out the fact that, whatever the reason may be, syphilis does but rarely attack the central portions of individual sensory nerves, in comparison, with the frequency with which it attacks individual motor (cranial) nerves. But without any neuralgic predisposition at all, and without any limitation of the syphilitic process to a particular sensory nerve, the latter may become neuralgic in consequence of being involved in extensive intracranial or intra-spinal syphilitic mischief. The trigeminus is liable to suffer in this way from spreading syphilitic processes about the base of the brain; and my own impression is, that the cause of the neuralgic pain in some such cases is the extension of the mischief to the vertebral artery of the affected side, leading to interfering with the nutrition of the trigeminal nucleus in the medulla. A very interesting case is reported by Dr. Hughlings Jackson (who has done so much to acquaint us with syphilitic affections of cerebral arteries) in vol. iv. of the "London Hospital Reports," pp. 318-321. The patient was a woman, aged twenty-seven, and the initial symptoms of the malady which destroyed her life were violent trigeminal neuralgic pains on the right side: subsequently she had complete paralysis of the fifth, and of the sixth, seventh, and eighth nerves of the right side. After death the right vertebral artery was found engaged in the mass of syphilitic deposit; it must be added, however, that the (superficial) origin of the fifth nerve was itself softened, opposite the pons. Another mode in which syphilitic disease very probably causes neuralgia of the fifth, in a certain number of cases, is by injuring the Gasserian ganglion, upon the integrity of which (according to Waller's general law concerning the ganglia of posterior nerve-roots) the nutrition of the sensory root of the trigeminus materially depends. I have seen an example (as I cannot but suppose) of this sequence of morbid events; the evidence appears sufficiently complete, although I was unable to obtain a _post mortem_ examination: