280 FUNCTIONS OF THE NERVOUS SYSTEM. 



as those of the pyramids pass backwards from between them, until they meet 

 on the median line, forming the greater part of the anterior column. 3. The 

 fibres of the Restiform, or Cerebellar columns, -which, like those of the 

 Olivary columns, do not decussate, mostly pass downwards into the posterior 

 columns ; but a band (which has been termed, from its curved aspect, the 

 arciform layer) passes forwards into the anterior columns : and another 

 small fasciculus enters the lateral columns. 4. The fibres of the Posterior 

 Pyramids are stated by Sir C. Bell to decussate like those of the anterior; 

 they pass down chiefly into the posterior part of the lateral column, forming 

 part also of the posterior. 



354. The following tabular view may assist, better than any delineations 

 could do, in the comprehension of this very intricate piece of Anatomy; the 

 knowledge of which can be readily applied to the explanation of many curious 

 pathological phenomena, and cannot but assist in the elucidation of others, 

 whose rationale is as yet obscure. 



SPINAL CORD. MEDULLA OBLONGATA. BRATS'. 



( Arciform fibres of Cerebellar Columns . . ) Cerebellum 

 Anterior Column ? Olivary Columns . . . . . . $ Corpora Quadrigeinina 



( Non-decussating portion of Ant. Pyramids ? /-. Ci . 



; T^. . l ~ . . , > Corpora otriata 



TV/T-JJI r< i S Decussating portion of Ant. Pyramids . . \ 



Middle Column < r -j , o'i ^\ 



{ Post. Pyramidal Columns (decussating?) . 1 . . 



PosteriorColumn \ P rti n f Post ' P y amids (non-decussating?) . \ 



\ Restiform Columns Cerebellum 



355. The Medulla Oblongata is not to be viewed, however, solely as a series 

 of connecting bands or commissures, between the Brain and Spinal Cord; for 

 it contains vesicular matter of its own, in virtue of which it serves as a gan- 

 glionic centre to nerves that are specially connected with it. The vesicular 

 matter is partly found in a situation corresponding to that which it occupies 

 in the spinal cord ; and it forms a tract, which is continuous above with the 

 grey nucleus of the Corpora Quadrigemina, and below with that of the Spinal 

 Cord ; and which is opened out to view (as it were) on the floor of the fourth 

 ventricle, forming the calamus scriptorius. Besides this central portion, 

 there are other outlying masses, which are continuous with it. Thus the 

 bulk of the Olivary body is principally due to the presence of a ganglionic 

 mass in its interior ; inclosed in the fibres of which the olivary column is 

 composed, and which, for the most part, pass over and around it without en- 

 tering it. This mass consists of a layer of grey matter, spread in a thin pli- 

 cated stratum over a centre of white substance, and altogether forming what 

 is known as the corpus dentatum. There is a considerable amount of ve- 

 sicular substance in the Restiform bodies also ; and this is continuous with 

 the grey matter forming the posterior cornua in the Spinal Cord. 



356. We have now to inquire into the character of the ganglionic masses, 

 which form, with the Medulla Oblongata, the Encephalon of Vertebrated ani- 

 mals. We should be liable to form a very erroneous conception of the rela- 

 tive importance, and of the real nature, of these, if we were to study them 

 only in the Brain of Man and of the higher animals ; for the great develop- 

 ment of their Cerebrum and Cerebellum throws into the shade (so to speak) 

 certain other ganglionic centres, which constitute yet more essential parts of 

 the nervous apparatus. It is one of the most interesting results of the com- 

 parison of the Human Brain with that of the lower tribes of Vertcbrata, that 

 the great change in the relative proportions of the parts, which we encounter 

 in the latter, makes evident the real nature and importance of what would 

 otherwise have been considered as subordinate appendages: whilst, at the 

 same time, they afford us the connecting links, by which we are enabled 

 to trace the real analogies of the different parts of the Encephalon with the 

 ganglionic masses which represent it among Invertebratcd animals. 



