A particular inquiry into the structure and probable function of the ganglion of the fifth nerve would involve that of the cerebrospinal ganglia in general, and will be better post poned to another occasion : it will suffice for the present to state that according to both Monro and Scarpa, they are composed in part of nervous chords, and in part by a soft grey or brown substance, which fills the intervals between the nervous filaments, and which according to the former resembles the cortical matter of the brain, while in the opinion of the latter it is a cellular texture filled by a matter, which varies in character according to the subject; thus he states that lie has found it fatty in fat and watery in anasar cous subjects. 2. That nervous filaments can be traced through them without interruption from the nerves situate above to those situate below the ganglion, which opinion is objected to by Niemeyer, who compares the connection of the former with the ganglion to that of the foetal and maternal portions of the placenta ; but inspection suffices to satisfy one that this idea of Niemeyer is incorrect; for whether additional filaments be furnished or not by the ganglion, the continuity of filaments above and below it is evident even in the human subject, and is still more manifest in other animals : in the horse it is easily seen, par ticularly after a section of the ganglion.
The question whether the ganglion receives filaments from the sympathetic system has been a subject of dispute among anatomists. The elder Meckel* denies the existence of any filaments of cnnnection between the sympa thetic and the fifth nerve, while within the fibrous chamber or while situate by the cavern ous sinus; and others also, among whom are Eustachius, IIailer, Albinus, and Morgagni, are of the same opinion ; but later investiga tions have put it beyond doubt that such a communication does exist. Bockj- has de
scribed filaments of the sympathetic united to the trunk of the fifth, before the formation of the Gasserian ganglion, and which join chiefly the fasciculi of the trunk, from which the ophthalmic nerve originates. And Arnold states " that several very delicate filaments go from the carotid plexus to the semilunar gan glion, particularly to the first and third branches of the nerve, and upon those points the gan glionic matter is accumulated in greater abun dance." Besides this connection between the sympathetic and the ganglion, others exist between it and the branches of the ganglion.
The ganglion appears to constitute an essen tial part of the fifth nerve throughout verte brate . animals, and to be uniformly present. It also presents in all the common character of being composed both of white and cineri tious matter, though the comparative amount of the two constituents varies according to the class, the order, or even the individual. The presence of the two structures the author would regard as essential to the constitution of cerebrospinal ganglia, and lie would ex clude from such those enlargements presented by nerves in certain situations, but from which cincritious matter appears to be absent. In Blammalia, Birds, and Reptiles, the fifth nerve is provided with a single ganglion, but in Fish and in both orders of that class it possesses for the most part two ganglia and two gan glionic fasciculi; this however is not uniformly so, for in some, e.g. the lophius piscatorius, the ganglion is single.