SEVENTH PAIR OF NERVES. 



549 



while lying closely by the side of the vestibular 

 branch of the auditory nerve (c), gives off a 

 filament (of), which passes towards it. Before 

 joining with it, however, a similarly small 

 branch which comes off from the latter nerve, 

 unites with that previously given from the 

 portio intermedia, and the common trunk 

 thus formed passes into and is lost in the 

 vestibular nerve. 



The intermediate nerve next emits two 

 small filaments (e), which join the portio 

 dura, and cannot be satisfactorily traced 

 through its trunk. 



The description is now complicated by the 

 introduction of a large branch of the facial (f) 

 which emerges from it to take a spiral course 

 around the portio intermedia ; and which, 

 after running with it for some distance, re- 

 turns to the facial at a lower point than that 

 from which it set out. 



Setting aside this fictitious junction, the 

 whole of the portio intermedia, after the 

 giving off of the facial and auditory branches, 

 was traced into the genuform intumescence : 

 this, it will be recollected, is seated on the 

 first bend of the facial in the Fallopian canal, 

 and close to the hiatus of the same name. 



The nature of this intumescence is the 

 next question to which the description directs 

 itself, and is perhaps even more important 

 than the preceding dissections. The appear- 

 ances of this swelling, and its reddish-grey 

 colour, had long given rise to conjectures of 

 its ganglionic nature. Many anatomists, in- 

 deed, have affirmed its identity with the true 

 ganglions. By others, however, it has been 

 somewhat obscurely described as intermediate 

 in structure between a ganglion and a gangli- 

 form enlargement: a description which can 

 only be understood as indicating their doubt 

 of its ganglionic character, since the supposi- 

 tion of such a gradation of texture is perfectly 

 gratuitous. And others have altogether de- 

 nied its ganglionic characters ; attributing its 

 colour to the minute vessels which pass through 

 the hiatus Fallopii to the facial nerve and 

 internal ear, and explaining the appearance of 

 enlargement or intumescence by the diver- 

 gence of the fibres of the superficial petrosal 

 nerve where it joins the facial. 



With the question of the ganglionic struc- 

 ture of this body has necessarily been mixed 

 up that of the course taken by the nerves 

 which arise from it, and their relation to the 

 facial. Indeed, the negative side of the ar- 

 gument the denial of the ganglion perhaps 

 requires its advocates to explain the real 

 nature of the swelling, and to show the ar- 

 rangement of its supposed constituent nerve- 

 fibres. But in the present day at least, the 

 affirmative of the question may be justifiably 

 reduced to the detection, in the so-called 

 ganglion, of the globular vesicles which are 

 essential to the structure of a nervous centre. 



it is singular that for a considerable time 

 this simple method of settling the disputed 

 nature of the intumescence should either have 

 escaped notice or failed to afford any satisfac- 

 tory results : the latter seems to have been 



sometimes the case; but more frequently, 

 perhaps, this method of proof or disproof was 

 overlooked. The discovery of the ganglion 

 corpuscles, and thus the establishment of its 

 ganglionic nature, belongs to Morganti. He 

 describes it as consisting of meshes or reticu- 

 lations of nerves, the intervals of which are 

 filled by a yellowish ash -coloured substance. 

 In the latter, he states himself to have verified 

 the existence of these bodies. 



The essential part of this description I am 

 able to confirm. It appears difficult to obtain 

 specimens from the human subject in a state 

 sufficiently fresh to observe these delicate and 

 easily decomposed corpuscles. In the lower 

 animals, however, this difficulty is no longer 

 met with ; and many of them present the 

 additional advantage of a much less dense 

 neurilemma than that which is present in the 

 human structure. After removing the brain 

 of the sheep, the ganglion may thus be easily 

 exposed and removed, preferably with the 

 nerves still attached to it. Cutting off the 

 attached extremities of these, and very gently 

 and imperfectly tearing up the ganglion which 

 remains, completes the preparation of the 

 specimen. Under these circumstances, the 

 corpuscles of the grey matter are readily 

 visible. They are of an oval or roundish 

 shape, and of a very large size, which amounts 

 in the average to about the 1 -200th of an inch. 

 In the uninjured parts of the specimen, they 

 appear to be disposed with considerable regu- 

 larity, each being in contact with several others 

 by a part of its surface. On a rough calcula- 

 tion, the ganglion contains about three or four 

 hundred of these corpuscles. The contents 

 of the corpuscles are of the ordinary kind. A 

 nucleus occupies some portion of their inner 

 surface, and a large quantity of the usual 

 granular substance fills up the remainder of 

 their interior. Most of them also contain a 

 quantity of pigment towards one extremity of 

 their ovoid cell-cavity. This is disposed as a 

 dark brown mass of an oval form, and some 

 of these masses, when seen isolated by the 

 accidental rupture of their containing vesicles, 

 have exhibited a defined and sharp outline, 

 which induces me to suspect their inclusion 

 in a cell membrane, separating them from the 

 rest of the contents of the vesicle. Rarely 

 there are appearances of short processes from 

 these vesicles. Nerve tubules in rather spar- 

 ing quantity are found in contact with these 

 large cells, mostly occupying their interstices, 

 or coiled around their circumference ; and the 

 periphery of the ganglion itself is surrounded 

 by a kind of layer of them : these appear- 

 ances, however, seem distinctly traceable 

 to the mechanical violence employed in the 

 examination, which forces the tubes into the 

 situations of least pressure ; and one cannot, 

 therefore, regard them as affording the least 

 insight into the mode in which the nerves are 

 arranged with respect to the vesicles. 



From this ganglion emerge, or rather to it 

 are attached, the following branches : 1 . 

 and 2. The superficial petrosal nerves, the 

 greater of which (fig. 405, k) passes to the 



N N 3 



