FIFTH PAIR OF NERVES. 



275 



viz the attachment of the two packets to the same 

 point, the existence of the eminence at the inser- 

 tion, and that of a cord of communication with 

 the anterior column of the spinal marrow. 



The encephalic connections of the nerve, 

 as detailed, are corroborated by those to be 

 observed in inferior animals. In those Mam- 

 malia in which the pons is but little deve- 

 loped, the nerve is attached between that part 

 and the trapezium; in those instances in which 

 the pons is more so, the nerve is attached, 

 superficially, not actually behind that part, 

 but near to its posterior margin; with little 

 trouble it can be followed to the back of the 

 pons, where it is attached, as in Man, to the 

 medulla oblongata, the point of attachment 

 presenting here also, after the separation of the 

 adjoining matter, the appearance of an emi- 

 nence or tubercle, from whence a cord de- 

 scends beneath the trapezium into the lateral 

 column of the spinal bulb. This cord is of 

 great size in many animals ; and in some can 

 be seen distinctly, without dissection, upon 

 the surface of the spinal bulb, in consequence 

 of the degree to which it projects : it is well 

 expressed in the delineation of the brain of the 

 calf in the third plate of Gall and Spurzheim, 

 and in that of the brain of the horse in fig. 275 

 of M. Serres' Illustrations of the Comparative 

 Anatomy of the Brain. 



In Birds, Reptiles, and Fish, neither pons, 

 trapezium, nor olivary bodies exist, and the 

 nerve is attached to the lateral part of the 

 spinal bulb at its superior or anterior extremity, 

 and to its lateral column the prolongation of 

 the superior column of the spinal cord. In 

 all three the point of attachment is situate a 

 little way from the back of the bulb and be- 

 neath the floor of the ventricle, the cineritious 

 stratum, of which the latter consists, being 

 directly connected to the back of the nerve. 

 In Birds (Jig. 142) the continuation of the nerve 



Fig. 142. 



can be traced downward along the side of the 

 bulb toward the spinal cord, and without diffi- 

 culty, inasmuch as it is superficial and is not 

 crossed by a trapezium, as in the Mammalia. 



In the Turtle the nerve can be traced in like 

 manner from the point of attachment down- 

 ward into the lateral column ; and in Fish the 



Fig. 143. 



Brain and Fifth Nerves of the Goose. 



1 Inferior surface of cerebrum. 



2 Spinal bulb. 3 Ganglia of fifth nerves. 



4 Root of nerve from lateral column of the bulb 

 exposed by turning aside the superficial stratum of 

 that part. 



5 First division of the fifth. 6 Second do. 

 7 Third do. 8 Auditory nerve. 

 On one side (the reader's right) the non-gan- 



glionic fasciculus has been traced beneath the gan- 

 glion into the third division of the nerve. 



Origin of nerve in Turtle. 



1 Spinal bulb. 



2 Fifth nerves. 



The pin is passed between the ganglionic and 

 non-ganglionic fasciculi, the latter being continued 

 into the third division. 



3 Ganglion. 



4 First division of the nerve. 



5 Second do. 



6 Third do. 



attachment is in all essentials similar : the com- 

 parative small ness of the bulb and the direc- 

 tion which the nerve takes in its course out- 

 ward, make it resemble the spinal nerves more 

 than in the other classes ; but its encephalic 

 connection is strictly the same, namely, to the 

 lateral column of the bulb beneath the floor of 

 the ventricle. In the Cod, after the removal of 

 the floor of the ventricle from the back of the 

 nerve, the latter may be followed for some way 

 into the column, though neither to the same 

 extent nor so satisfactorily as in the bird or the 

 Turtle; and in the Ray, while the two inferior 

 fasciculi of the nerve for in this fish it consists 

 originally of three are connected in the usual 

 mode to the lateral column, the superior is 

 attached to a convolution formed by the floor, 

 in consequence of a greater developement of its 

 margin. In the Cod the convolution adverted 

 to does not exist, but the floor of the ventricle 

 cannot be raised from the nerve without destroy- 

 ing a connection of some kind between them. 

 In the latter fish the fifth nerve is attached 

 before and rather superior to the auditory nerve, 

 and the two nerves are quite distinct as far as 

 the point of attachment, but there they are in 



T2 



