its affection, I could not find in the literature, therefore future investigations must show whether our propositions are correct or not regarding the microscopical changes in this nerve in tabes dorsalis.

The second pair, nervus opticus, consists of fibers which are nothing but axy-cylindrical processes of multipolar ganglion cells of the retina. This nerve is entirely analogous to the spinal nerves with their ganglia and processes. In this case the ganglia are the nerve cells of the retina, the peripheral processes or nerves are represented by a row of formations contained between the rods and cones on one side and

the ganglion sheath on the other.* As central processes there are the fibers of the optic nerve, which penetrate the membranes of the base of the brain and become divided by them into separate bundles. In tabes, according to our supposition, we have to deal especially with the inflammation and thickening of the membranes; we must have here a lesion of the optic nerve, by which lesions we will have fibers gradually compressed by the changed membranes. Like the posterior roots the fibers of the optic nerve must, because of the disconnection from the center-the retina, undergo degeneration with the consequent atrophy; this latter, as in the roots, must start in the marginal fibers of the optic nerve; later on axial fibers, the centrally located, must become affected; besides this the atrophic process in its development must be a centripetal one-from the retina to the brain, and finally it must affect also the proximal part, which is immediately connected with the retina. These propositions are completely verified by the literary facts.

Leyden and Goldscheider in their treatise on tabes dorsalis, prepared for Nothnagel's Encyclopædia, write the following of the atrophy of the optic nerve in tabes: "In tabetic atrophy of the optic nerve the marginal fibers become especially affected; the central ones become affected also, but in a lesser degree and in the latest stages.

*Moster: Zeitschr. f. klin. Medic. Bd. XXIX.

"It is necessary also to accept that the atrophy of the optic nerves is a process going centripetally from the retina.” Besides this the pia mater, as we have already pointed out, projecting into the optic nerve, divides it into separate bundles, forming numerous septa that compose a substantial part of the optic nerve. If the optic atrophy is the result of inflammation of the membranes, then we have to find in such a case proliferation of the connective tissue in the atrophied nerve, dependent on the inflammation of the septa or of the pia mater. On this account Gowers says on p. 474 of the first volume of his text-book (ed. 1896): "The atrophied optic nerves represent disappearance of the nerve fibers and usually a remarkable proliferation of the connective tissue, which forms thick, jelly-like bundles."

Direct communications about the combination of the atrophy of the optic nerves with the thickening of the membranes of the brain I could not find, if we exclude Türk's communication, from which we can draw only an indirect conclusion of such a a connection. On page 118 of the several times quoted paper of Professor Türk (Stzb. der Akad. der Wissen. zu Wien, 1656) he says: "In one case of an intensive jelly-like degeneration of the posterior columns and posterior parts of the lateral columns there was thickening and adhesion of the internal cerebral membranes with the surface of the brain convolutions and jelly-like degeneration of the optic nerves." This observation shows that the atrophy of the optic nerve may be the result of the inflammation of the membranes; in favor of this is also the fact of the atrophy of optic nerves in epidemic cerebro-spinal meningitis, especially when the latter becomes chronic.

A long compression of the nerve fibers will lead to atrophy of the optic nerves and eventually to the loss of vision. Thus the membrane theory of tabes dorsalis explains very well one of the most important and constant symptoms of locomotor ataxia-the atrophy of the optic nerves.

The nervus oculomotorius (the third pair) arises from the nerve cells in the region of the corpora quadrigemina and leaves the brain in trigonon interpedunculare from the sulcus oculomotorius. Here it becomes invested by the pia mater and tunica arachnoidea and must therefore undergo changes in tabes dorsalis, provided the latter consists in inflammatory changes of the membranes. The character of these alterations is the same as for the spinal nerves, namely the degeneration of the peripheral portion because of its disconnection from the center and in more rare cases-old cases -the degeneration of the central portion and even of the nuclei. According to Kahler and Pick* the fibers of the oculomotor nerve destined for different muscles are located differently: laterally are located fibers destined for the musculus palpebrarum; further follow fibers for the musculus rectus super., obliq. inf., etc., which must give as a result different ocular disturbances in tabes, as ptosis, strabismus, diplopia, myosis, etc.-everything depends on the localization and the degree of development of the morbid process, viz., on the quantity of fibers involved in the process of compression by the thickened brain membrane. Existing observations completely confirm our proposition, because the ocular symptoms are very often met with in tabes and the degeneration with atrophy of this nerve, with or without simultaneous lesion of its nucleus, was described many times, but while some authors, as Möbius, ascribe the atrophic changes of this nerve to the lesion of its nuclei, the others accept here not the central degeneration, but the peripheral one of the trunk itself of the third pair. The second assertion is most correct, because Möbiust himself says, that "In a few cases the latter (oculomotor nerve), or some branches of the

*Kahler and Pick: Zur Localisation central bedirgter partieller Oculomotoriuslähmungen (Arch. f. Psych. X).

Kahler and Pick: Zur Localıs. part. Ocul. Läm. (Prag. Zeitsch. 1881). +Möbius: Twentieth Century Practice of Medic. XI, p. 819.

latter, have been found degenerated, the nuclei not being affected," which in our opinion would be utterly impossible in any case, if the cause of the affection of oculomotor nerve in tabes were the changes of its nuclei. On this record Prof. Lloyd says: "In tabes, however, it is still a question whether ocular paralyses are due to involvement of the nerve trunk or that of the nuclei. The degeneration of tabes is so nearly confined in all parts of the nervous system to the sensory fibers that it may be a question whether in this instance the third nerve forms a true exception to the rule.”* The oculomotor nerve does not form any exception; its affection in tabes, the character of its changes, can be logically explained by the ground cause of all tabetic symptoms-by the alteration of its membranes.

What was said on account of the oculomotor nerve is applied also to the fourth pair-the nervus trochlearis, which supplies only one muscle (m. obliquus super). It occupies a small space on the base of the brain exteriorily to the peduncle of the brain where it pierces through the pia mater. The affection of the latter involves the nerve and will produce affection of the supplied muscle, which causes strabismus internus as a result. This really is a fact in tabes dorsalis, though not very often observed separately; but in connection with lesion of other cranial nerves this symptom is of not infrequent occurrence. Changes in nervus trochlearis in tabes were described by Cassirer and Schiff: in one observation there was degeneration of the roots of the oculomotor nerve and of the abducens, in the other case (4th observation)-unilateral lesion of the roots and nuclei of the nervus trochlearis. +

Let us proceed to the fifth pair-nervus trigeminus. It

*Lloyd: Diseases of the cerebrospinal and sympathetic nerves in 20th Century Practice of Medicine, Vol. XI, p. 143.

†Cassierer u. Schiff: Beiträge zur Path. der chron. Bulbärerkr. (Arb. aus dem Lab. des Prof. Obersteiner, Wien, 1896.

consists of a motor portion (portia minor) and a sensitive one (portio major). The former arises in cells of the motor nucleus, located in the pons, the latter-the sensitive rootin the Gasserian ganglion.

nosa.

The Gasserian ganglion plays the same rôle in regard to nervus trigeminus, that the spinal ganglia play in regard to the spinal roots. The central process of the sensory part of the fifth pair goes from the Gasserian ganglion into the pons, where its fibers are split into an ascending branch, going on to the sensory nuclei of the trifacial nerve, and into the descending, going through the pons, medulla oblongata and spinal cord as a spinal trifacial root (spinale Trigeminuswurzel of Prof. Obersteiner) and ends in the substantia gelatiBoth roots of the nervus trigeminus, the motor and the sensitive one, appear on the lateral surface of pons Varolii, where they pass through the cranial membranes. Supposing now the localization of the tabetic process to be in this place of the pons Varolii or around the roots of the fifth nerve in general, we must have as a result some symptoms of lesion of the latter, as, for instance, hypersæthesia, anæsthesia, paræsthesia, which symptoms are very often met with in tabes, provided the tabetic process is localized in the cranial part of the central nervous system (tabes cervicalis, according to Remak). If the membranes will steadily compress the sensory root in front of the Gasserian ganglion, which is for this nerve a nutritive center, we must get the degeneration and atrophy of the trifacial spinal root, which was described by Prof. Westphal (1864),* by Hayem,† Oppenheim and Siemerling, Cassirer and Schiff (.c.) In the cases of Oppenheim and Siemerling (7th and 9th observations) there were observed during lifetime anæsthesia in the region of the

*See Gowers: Diseases of the Nervous Syst., Vol. I, p. 474 (3rd ed.). Erb: Ziemsen's Handb. Bnd. XI, p. 549.

Oppenheim u. Siemerling: Beitrage zur pathologoschen Anatomie der Tabes dors. und der peripheren Nervenkr. Arch. d. Psych. 1887. Bnd.