2. The branches, which are given off next by the second division of the fifth, are those by which the nerve is connected to the spheno palatine ganglion; they are hence denominated the spheno-palatine ; the ramifications derived from them, or from the ganglion with which they are connected, are distributed to the nos tril and the palate, and they may hence with more propriety be termed the naso-palatine, an appellation which is the more appropriate, since it is already applied to the corresponding branch of the second division of the fifth in other animals. It is at the same time to be borne in mind that a difficulty has been created in this matter by the application of the epithet in question to certain secondary branches, to be mentioned by and-by; but the latter use of the term ought to be discarded. They are irregular in number, there being sometimes but one, at others two or three: they are short and of con siderable size, and ariso from the inferior side of the nerve, immediately after it has entered the spheno-maxillary fossa ; they descend from it, almost perpendicularly, into the fossa, pos terior to the internal maxillary artery, and im mersed in fat, and after a very short course they are connected to the ganglion, from which they may seem to ascend to the nerve. They are thus described by Cloquet, but this view is not sanctioned either by comparative anatomy, or by the result of experiments, both which prove that they are to be considered branches of the nerve, with which the ganglion is con nected.
The ganglion has been first described by the elder Al eckel,* and hence has also received the title of Aleckel's ganglion ; it is very small, of a grey colour, and firm consistence ; its shape is triangular or cordiform, one surface directed outward, the other inward; it is situate immediately external to the splieno-palatine foramen, its internal surface, which is flat, cor responding to the foramen, its external, which is convex, to the zygomatic fossa. It is subject to variety ; in some instances it is wanting, and then the spheno-palatine nerve gives off those branches which otherwise arise from the ganglion : in other rare cases, according to Aleckel, the two principal branches, which arise from the ganglion when present, or from the spheno-palatine when single, viz. the Vidian and the palatine,proceed separately from the trunk of the second division of the fifth ; in others again the author has observed a cineri tious soft enlargement upon the Vidian nerve at its junction with the spheno-palatine, but not involving that nerve or the branches pro ceeding from it ; and this, it is worth remark ing, is precisely the disposition of the ganglion in the dog and some other animals. Different views have been taken of the nature and rela tions of this ganglion : the Aleckels, by the elder of whom it was discovered, Bichat, Boyer, and others, have regarded it as belonging pro perly to the fifth nerve, and formed by the branches which have been mentioned : Cloquet, on the other band, considers and describes it as a part of the ganglionic or sympathetic system, and all the nerves connected with it, as well the original spheno-palatine branches as the others, to be branches from it: Cruveil hier again, while lie admits the existence of ganglionic structure, yet leaves it uncertain whether he regards it as a sympathetic or a cerebro-spinal ganglion, but he differs from Cloquet in maintaining that " the nerves," which seem to arise from it, "are not detached from the ganglion itself, and come directly from the superior maxillary." The opinions of Cloquet and Cruveilhier appear to the author to be both, to a certain degree, well-founded. The ganglion would seem not to be properly a part of the fifth nerve, because, I. it is not, as he believes, present in animals below the mam malia ; 2. it is not always present even in them, and in neither case is the general distribution of the part of the fifth nerve, with which it is connected, influenced by its absence; 3. it is
manifestly different in its characters from the fifth nerve and from the branches of the nerve to which it is attached, nor does it resemble the cerebro-spinal ganglia, the peculiar appear ance of these bodies, viz. white filaments enter ing and emerging, their continuity being appa rently interrupted by an interposed mass of cineritious matter, not being observable; while, on the other hand, it resembles the ganglia of the sympathetic, and is actually connected with that nerve by a branch having precisely the same qualities with those which proceed from it, viz. by the inferior branch of the Vidian nerve: for those reasons the author would adopt the opinion of Cloquet, that the ganglion is properly a part of the ganglionic system, and that it is only accessory to the fifth nerve. On the other hand, it appears to him that Cloquet is mistaken in considering the ganglion as the source of all the nervous filaments connected with it, and more particularly of the spheno palatine branches of the second division of the fifth, to which in man the ganglion is attached, for, as has been already stated, the general dis tribution and existence of these branches are not at all influenced by the absence of the gan glion, and when present it allows in general, as Cruveilhier has observed, the nerves to be fol lowed up and down from the swelling, and lastly, any obscurity existing with regard to this point in the human subject will be at once removed by reference to the disposition of the ganglion in other animals, in none of which that the author has examined does it involve the nerve, but is merely connected to it either by filaments or by one extremity, the continuity of the nerve being altogether uninterrupted and a marked contrast being to be observed between the characters of the two parts : thus in the dog, the ganglion is an oblong dark grey swelling, with the. posterior extremity of which the Vidian nerve is united, while its an terior is attached to the naso-palatine nerve. The author, therefore, concurs in the opinion of Cruveilhier, so far as to regard the nerves con nected with the ganglion, for the greater part, as branches of the fifth nerve and not of the ganglion; but he would exclude from this view the Vidian nerve, or at least its carotidean branch, which appears to him to belong to the sympathetic system. (See posterior branch of ganglion.) The disposition of this ganglion throughout the animal series is an object of interest. The author cannot assert its existence in the mam malia universally, but from indirect considera tions it appears to him likely that it does exist, generally at least, in animals of that class. It is asserted in the work' of Desmoulins and Alajendie on the Anatomy of the Nervous Sys tem in vertebrate Animals, that " there does not exist any trace of it in cats, dogs, the rumi nantia, the rodentia, the horse, &c. ;" and it is reasonable to infer that they had found it in others. Now their statement with regard to its absence is, in the majority of the instances which they have selected, positively incorrect, for the author has ascertained its existence most satisfactorily in the dog, the horse, the cat, the cow, and the rabbit. Nor is any ex ception to its existence mentioned by Cuvier, and hence he thinks it likely that it does exist generally, if not universally, throughout the class. It is not however similarly disposed in all ; in some it is connected with the primitive naso-palatine nerve; in others with its nasal; and in others again with its palatine division : in some it gives off few filaments ; in others, the horse, e. g. they are numerous beyond de scription. The ganglion does not appear to exist in the inferior classes.