NERVOUS SYSTEM OF VERTEBRATA. 



127 



of con. ibres, by which the nerves proceeding from anyone division 



are brought into relation with distant portions of the organ, and with the large 

 ganglionic masses at its anterior extremity. In this respect, then, it corre- 

 sponds precisely with the doable nervous cord of the Articulata; the only 

 prominent difference between the two being, that in the former the ganglionic 

 matter is continuous from one extremity of the organ to the other, whilst in 

 the latter it is interrupted at intervals ; and in the Mollusca, the centres are 

 still further separated from each other. The connection of the Spinal Cord 

 with the large ganglia contained within the cavity of the cranium, is effected 

 by means of processes from its superior extremity, the arrangement of which 

 is somewhat complex. This portion of the cord, which also lies within the 

 cavity of the cranium, has been termed the Medulla Oblongaia. It has 



Fig. 20. 



Fig. 21. 



A posterior superior view of the Pons Varolii, the 

 Cerebellum, and the Medulla Oblongata and Spinalis. 

 1, 1, the crura cerebri ; 2, the pens varolii or tuber-aii- 

 nularis; 3, its middle fossa; 4, an oblique band of me- 

 dullary matter seen passing from its side ; 5, the external 

 surface of the cms cerebelli in its natural state ; G, the 

 same portion deprived of outer layer; 7, the "nervous 

 matter which united it to 4; 8, the trigeminus or fifth 

 pair of nerves; 9, portion of the auditory nerve the 

 white neurine is seen passing from the oblique band 

 which comes from the corpus .restiforme to the trige- 

 minus nerve in front, and the auditory nerve behind ; 

 10, 11, the superior portion of the hemispheres of the 

 cerebellum; 12, lobulus amygdaloides ; 13, corpus oli- 

 vare; 14. corpus pyramidale ; 15, medulla spinalis. 



A posterior view of the Medulla Ob- 

 lonsrata, as split open vertically on the 

 middle line At the bottom of the fis- 

 sure is a succession of fasciculi which 

 interlock and cross from right to left. 

 The cerebellum has also been cut off 

 from its crura with great care, so as to 

 show plainly the three principal ele- 

 ments in its composition. 1. the thalami 

 nervi optici slightly separated; 2, the 

 corpora geniculata; 3, the tubercula 

 quadrigemina; 4, the pineal gland di- 

 vided in the middle; 5, the aqueduct of 

 Sylvius laid open; 6, the fasciculated 

 portion of the crura cerebelli; 7, 8, 9, the 

 internal, middle and external fasciculi 

 of the crura cerebelli ; 10, rootoWne au- 

 ditory nerve ; 11, corpus restiforme ; 12, 

 posterior portion of the corpus pyra- 

 midale ; 13, posterior middle fissure of 

 the spinal marrow; 14, point of the cala- 

 mus scriptorius; 15. 15, between th6e 

 figures is seen the interlocking of the 

 two halves of the me"dulla oblongata. 



