210 



DISSECTION OF THE BRAIN. 



the convolutions : their expansion in the hemisphere resembles a fan bent 

 down in front and behind, forming thus a layer which is concave on the 

 under side. 



Their extent. All the fibres of the peduncle do not reach the surface of 

 the brain, for some end in the corpus striatum and the optic thalamus, 

 especially in the former. And some of the fibres in the convolutions begin 

 in the ganglionic bodies before mentioned, and extend to the surface of 

 the hemisphere. 1 Thus, in addition to the fibres continued throughout, 

 viz., from the crus to the surface, some unite the peduncle of the cerebrum 

 with the ganglia, and others connect the ganglia with the convolutions on 

 the exterior. 



1. Superior peduncle. 



2. Middle, and 3, infeiior pc duncleof 



the cerebellum. 



4. Process from the fillet of the oli- 

 vary body to the corpora qnadri- 

 geniina : on the right side it \s 

 cut and reflected. 



5 Posterior pyramid. 



6. Continuation of the lateral tract 

 into the optic thalamus. 



7. Corpora quadrigemiua. 



8. Optic thalamus. 



9. Corpus striatum. 

 10. Corpus ciillusuin. 



CONNECTION POSTERIORLY BETWEEN THE CERJBRUM AKD THE MEDULLA OBI.ONQATA AND 



CEREBELLUM. 



Their source. The fibres thus entering inferiorly the cerebrum through 

 its peduncle, and continued thence to the periphery of the hemisphere, are 

 derived from the component pieces of the medulla oblongata except the 

 restiform body (fig. 57), viz., from anterior pyramid, lateral column and 

 olivary body, and posterior pyramid (p. 183) : they serve to connect the 

 spinal cord with the cerebrum. The decussation between opposite sides 

 has been before referred to (p. 186). 



The transverse or commissural fibres connect the hemispheres of the 

 cerebrum acros the middle line. They give rise to the great commissure 

 or the corpus callosum (p. 210) : and to the anterior and posterior com- 

 missures (p. 207). Those bodies have been already examined. 



Longitudinal fibres. Other connecting fibres pass from before back- 

 wards, uniting together parts of the same hemisphere. The chief bands 

 of thi system are the following, the fornix, the tsenia semicircularis, and 

 the peduncles of the pineal body. Other longitudinal fibres may be enu- 



1 According to some authors none of the fibres of the peduncle reach farther 

 than the corpus striatum and the optic thalamus. 



