CONVERGING FIBRES. 



The fibres which enclose the corpus olivare, under the name of fascicuji 

 siliquse, are separated by that body into two bands ; the innermost of the 

 two bands, funiculus siliquce internus, accompanies the fibres of the corpus 

 pyramidale into the crus cerebri. The funiculus siliquce externus unites 

 with a fasciculus proceeding from the nucleus olivse, and the combined 

 column ascending behind the crus cerebelli divides into a superior and an 

 inferior band. The inferior band proceeds w r ith a fasciculus presently to be 

 described, the fasciculus innominatus, into the upper segment of the crus 

 cerebri. The superior band (laqueus) ascends by the side of the pro- 

 cessus e cerebello ad testes, and, crossing the latter obliquely, enters the 

 corpora quadrigemina, in which many of its fibres are distributed, while 

 the rest are continued onwards into the thalamus opticus. 



The corpora restiformia derive their fibres from the anterior as well as 

 from the posterior columns of the medulla oblongata; they diverge as they 

 approach the cerebellum, and leaving behind them the cavity of the fourth 

 ventricle, enter the substance of the cerebellum, under the form of two 

 rounded cords. These cords envelope the corpora rhomboidea, or gan- 

 glia of increase, and then expand on all sides so as to constitute the cere- 

 bellum. 



Besides the fibres here described, there are, in the interior of the me- 

 dulla oblongata, behind the corpora olivaria, and more or less apparent 

 between these bodies and the corpora restiformia, two large bundles of 

 fibres, the fasciculi innominata. These fasciculi ascend behind the deep 

 transverse fibres of the pons Varolii, and become apparent in the floor of 

 the fourth ventricle, under the name of fasciculi teretes, or posterior 

 pyramids. From this point they are prolonged upwards beneath the cor- 

 pora quadrigemina into the crura cerebri, of which they form the upper 

 and outer segment, and are thence continued through the thalami optici 

 and corpora striata into the hemispheres. The locus niger of the crus 

 cerebri is a septum of grey matter interposed between these fasciculi and 

 those of the corpora pyramidalia. 



CONVERGING FIBRES. In addition to the diverging fibres which are 

 thus shown to constitute both the cerebrum and cerebellum, by their 

 increase and development, another set of fibres are found to exist, which 

 have for their office the association of the symmetrical halves and distant 

 parts of the same hemispheres. 



These are called, from their direction, converging fibres, and from their 

 office, commissures. The commissures of the cerebrum and cerebellum 

 are the 



Corpus callosum, 



Fornix, 



Septum lucidum, 



Anterior commissure, 



Middle commissure, 



Posterior commissure, 



Peduncles of the pineal gland, 



Pons Varolii. 



The Corpus callosum is the commissure of the hemispheres. It is 

 therefore of moderate thickness in the middle, where its fibres pass 

 directly from one hemisphere to the other; thicker in front (genu), where 

 the anterior lobes are connected ; and thickest behind (splenium), where 



