FIFTH PAIR OF NERVES. 



271 



eularly and accurately described by Palletta.* 

 They are distinguished by the latter into supe- 

 rior and inferior, being attached to the crus 

 cerebelli, one above and behind the other, and 

 they are frequently separated from each other 

 at their attachment by an interval of one or 

 two lines or more. In such case the superior 

 root is superior and parallel to the inner side 

 of the greater packet, while the inferior is in- 

 ternal to it, and, it may be, on a level with its 

 inferior surface; hence, in such instances, the 

 greater packet corresponds to the interval be- 

 tween the roots of the lesser, and the inferior 

 root of the lesser, in its course from the brain, 

 is placed at first along the inner side of the 

 greater packet, while the superior descends 

 internal to the greater packet, and joins the 

 inferior beneath it to constitute the lesser 

 packet. This is not, however, uniformly the 

 relation of the roots of the nerve at their at- 

 tachment to the crus, for the distance at which 

 they are placed from each other varies very 

 much; in some instances the roots of the lesser 

 packet are perfectly distinct and separated by 

 the interval mentioned, the inferior being either 

 in immediate contact with the greater packet, 

 and even entering the crus through the same 

 aperture, or being separated from it by an 

 interval varying, according to J. F. Meckel, 

 from a quarter of a line to a line; while in 

 others the roots of the lesser packet are not 

 manifestly distinct, but the fasciculi of which 

 they consist are attached to the crus in an un- 

 interrupted series reaching, from the attachment 

 of the greater packet, to within a line or less of 

 the posterior face of the crus, and separated 

 the one from the other by trifling intervals ; in 

 the latter case the lesser packet is, for the most 

 part, altogether superior to the greater at their 

 attachment. But even in this the lesser is still 

 distinguishable into two sets of fasciculi, which 

 take different routes through the substance of 

 the crus, one traversing it nearer to its ante- 

 rior, the other to its posterior surface. It has 

 been already stated that the lesser packet of 

 the nerve is characterized by the absence of a 

 ganglion ; it also has no connexion with the 

 ganglion of the larger packet, but passes it 

 without entering into it, and then becomes 

 attached to one of the trunks proceeding from 

 it; it is further maintained to be distributed 

 ultimately into those branches which are given 

 by the third division of the fifth to the muscles 

 of mastication. Pallettaf concluded from these 

 circumstances that it was a nerve distinct from 

 the remainder of the fifth ; and observing that 

 the superior root was principally consumed in 

 the temporal muscle, and the inferior in the 

 buccinator, forming the long buccal nerve, 

 he called the former the " crotaphitic," and the 

 latter the " buccinator" nerves. The distri- 

 bution of the lesser packet to the muscles of 

 mastication has been confirmed by Mayo J from 



* Pallet'.a, De Nervis crotaphitico et buccina- 

 torio, an. 1784. Script. Neurol. Min. Select. Lud- 

 wig. 



t Op. cit. 



j Commentaries, and Physiology. 



the dissection of the nerve in the ass. He 

 differs, however, from Palletta with regard to 

 its distribution to the buccinator, which he 

 denies : this point will come under considera- 

 tion again. It has been proposed by Eschricht* 

 to denominate it the masticatory nerve. 



The place at which the nerve is attached to 

 the surface of the brain in the human subject 

 is to be regarded only as the point at which it 

 enters or emerges from the substance of the 

 organ, inasmuch as it can be, without difficulty, 

 followed to a much deeper part, and the fibres 

 of the crus, which are transverse to those of the 

 nerve, manifestly separate from each other, at 

 the entrance of the nerve, to allow it a passage. 

 The larger packet of the nerve is that whose 

 course into the brain can be most easily traced; 

 this circumstance depends partly upon the 

 greater size of the packet, and partly upon the 

 fact that, for the most part, its tracts are not 

 separated from each other by those of the crus, 

 but traverse that part in a body, the fibres of 

 the crus seeming to be simply laid in apposi- 

 tion with it, and connected to it by some deli- 

 cate medium ; while those of the lesser are, in 

 the greater number of instances, separated from 

 each other, or even interlaced with those of the 

 crus ; hence the fibres of the crus may be easily 

 raised, without injury to the nerve, from the 

 larger packet, and its course be displayed, 

 while the lesser cannot be followed but with 

 difficulty. The larger is, however, subject to 

 variety in the latter respect ; in many instances 

 the fasciculi of the crus do traverse and divide 

 it, and very frequently near its ultimate attach- 

 ment, and this circumstance, when it occurs, 

 renders the pursuit of its course more difficult ; 

 but even here the fasciculus merely traverses 

 it, and its tracts are not permanently separated, 

 but reunite after the fasciculus has passed. 

 The course of the packet may be exposed to a 

 considerable extent even in the recent brain ; 

 but for the satisfactory determination of the 

 point, it is necessary that the brain be prepared 

 by some of the methods recommended for that 

 purpose, of which immersion in strong spirit is 

 by far the best, nor does it require much time, 

 for the substance will be found to separate 

 more easily when it has acquired only a certain 

 degree of firmness, than when hardened to the 

 degree which long immersion produces; the 

 plan which the author has found most success- 

 ful has been to commence the dissection early, 

 to return to it frequently, and at each time to 

 pursue it so far and so far only as it was satis- 

 factory. The course of the larger packet is 

 also beneath and before that of the lesser, and 

 hence, in the usual mode of dissection, in which 

 the brain is reversed, it presents itself first. 

 Its direction is backward, downward, and in- 

 ward, toward the upper extremity of the spinal 

 bulb ; in its course the packet first traverses 

 the middle crus of the cerebellum from its an- 

 terior toward its posterior surface, and from its 

 superior toward its inferior margin ; it pursues 

 this course until it has reached the back of the 

 crus, and descended so low as its inferior mar- 



* Journal de Physiologic, t. vi. 



