382 THE NERVOUS SYSTEM IN GENERAL, [ch. ii. 



the cortical than in the brain, and gives off its medulla, partly 

 upwards to the corpora quadrigemina, and partly downwards to 

 the medulla oblongata, but principally to the pons varolii of 

 which it constitutes the greater portion. Beneath the pons 

 varolii the caudex medullaris takes its origin, and passes through 

 the occipital foramen. It has been specially designated the me- 

 dulla oblongata by late anatomists, and consists of the anterior 

 and posterior pyramids, with the olivary bodies between them, 

 in which the cortical matter is so peculiarly interwoven, that a 

 transverse section of an olivary body presents serpentine lines, 

 having somewhat the appearance of a small tree. The composi- 

 tion of the medulla oblongata is of a simpler character ; it is a 

 thick nervous cord, occupying the cavity of the vertebral column: 

 on its anterior surface there is a groove (some call it a fissure) 

 which divides it perpendicularly into two columns, internally 

 in its centre there is, as some think, something of a cortical 

 substance. The origin of the nerves of the brain, and of the 

 medulla spinalis, is different as to situation and size, more 

 simple in some, in others compounded of many roots ; of these 

 are some which are enlarged near their origin by a ganglion, 

 as in the fifth pair of cerebral nerves, and in all the spinal 

 nerves, but others more distantly, as is particularly the case in 

 the intercostal nerves. As to other points, all the nerves 

 passing out from the cranium and vertebral canal are furnished 

 with a double investing membrane, and contain a continuation 

 of the medullary substance of the brain and spinal cord, but 

 are of a firmer consistence. In their course to various parts, 

 the fasciculi of which they are composed enter into remarkable 

 plexuses and connections, until they terminate variously in 

 various parts ; in the eye, the optic nerve expands into a mem- 

 brane ; in the ears, in the Schneiderian membrane, in the pa- 

 pillae of the tongue, in the skin, in muscles, and in various 

 secreting viscera they probably terminate differently ; but as to 

 this point nothing is known, for they escape the most acute 

 vision. 



All these portions of the nervous system, which I have only 

 cursorily enumerated for the sake of brevity, and of which 

 anatomy furnishes an accurate description and delineation, ^ 



• Monro, Winslow, and Haller, have published most accurate descriptions of the 

 nerves ; and their works are so well known and received with such general approval, 



