THE CEREBRUM. 859 



been hardened in spirits of wine, and it is constituted by what 

 are called, by MM. Gall and Spurzheim, the diverging fibres of 

 the brain. 



The point is not, indeed, entirely settled that the diverging 

 filaments end in the convolutions, or do not rather afterwards 

 inflect or double on themselves, and pass inwards again to the 

 middle line of the brain, forming, by their convergence, the cor- 

 pus callosum. At all events, the fact is quite demonstrable, that 

 as the under and lateral portions of the hemispheres consist in 

 diverging filaments, arising in and from the crus cerebri, so the 

 upper portion and the corpus callosum, consist in filaments which 

 arise in the adjoining convolutions, and collect towards the mid- 

 dle line of the corpus callosum, where they adhere to the con- 

 generic filaments of the other side. 



The arrangement, in the most simple conception and illustra- 

 tion of it, would be exemplified by folding a strip of cloth double 

 on itself, so as to convert it into a loop; the under part of the 

 loop would then represent the diverging fibres of the cerebrum 

 and the upper part the converging fibres, or corpus callosum; 

 it being at the same time borne in mind that the continuation pf 

 the two orders of fibres into one another in the brain is not so 

 fully ascertained as it would be represented by this model. 



Between the two orders of fibres there is a horizontal cleft or 

 interval. This interval is the lateral ventricle of the hemisphere, 

 which may be got into under the posterior margin of the corpus 

 callosum, from its being open there, or rather only closed by an 

 adhesion of the membranes, which is easily lacerated. 



The preceding is intended as a mere outline upon which to 

 form the base of the descriptive anatomy of the cerebrum. 

 The following, therefore, may be considered as the detailed ac- 

 count: 



The Crura Cerebri are rounded below; are about eight lines 

 long, and increase in their transverse diameter as they advance; 

 their vertical diameter is about ten lines. They mutually di- 

 verge, beginning from their roots, and are separated by a deep 

 fissure, considered as a continuation of that on the front of the 

 medulla oblongata. This fissure is the third ventricle of the 

 brain. Their surface is marked by superficial furrows, running 

 longitudinally; and about two lines before the tuber annulare, 

 by a transverse fasciculus of. medullary matter, very slightly 



