464 THE TISSUES. 



ferent, however, from these smaller elements are the large cells dis- 

 covered by Purkinje, and which are found only in the innermost 

 portions of the gray, next to the ferruginous layer. (Fig. 808, a.) 

 These measure ^^ to ^^ of an inch, are round, pyriform, or oval, 

 with finely granular colorless contents, and 1 to 4 (generally 2 or 

 3) long and much branched processes ; the largest of these being 

 given off from the sides of the cells which look from the ferrugin- 

 ous layer, and extending nearly to the outer surface (f or f- of its 

 thickness), and producing a striation seen in horizontal sections. 

 At their origin these processes are sometimes g^^ of an inch thick, 

 and very finely granular or delicately striated. As they proceed 

 they become more homogeneous, and divide into numerous ex- 

 tremely slender branches, the ultimate ones being scarcely goo^ir 

 of an inch thick. Kolliker has traced these processes even g 1 ^ of 

 an inch without coming to the finest subdivisions. While their 

 principal prolongations are thus continued through the gray layer, 

 they give off their branches at acute or right angles, producing a 

 second striatiou, crossing the -one before-mentioned at a greater or 

 less angle. 



The crura cerelelli contain nerve- fibres only; being a continua- 

 tion of the white matter of the cerebellum itself. 



3. The Ganglia of the Cerebrum. 



Of these there are three pairs ; the corpora quadrigemina, the 

 optic thalami, and the corpora striata. (Fig. 309.) All these are 

 bulky collections of gray substance and nerve-fibres. The latter 

 connect these ganglia on the one hand with the cerebellum and 

 medulla oblongata, and on the other with the hemispheres of the 

 cerebrum. They present no histological peculiarities. 



Nor is it necessary particularly to describe the gray matter in 

 these three ganglia. Kolliker considers it as made out that the fine 

 nerve-fibres traceable to the outermost part of the ventricular nu- 

 cleus (the posterior and inferior portions) of the corpus striatum, 

 terminate there, and do not proceed to the cerebral hemispheres. He also 

 regards it as probable that the fibres becoming attenuated in the 

 optic thalamus and the tubercula quadrigemina, terminate in like 

 manner. At the same time, it appears to be the fact that nerve- 

 fibres rising in the cerebral hemispheres also become attenuated 

 and terminate in these same ganglia. 



Other parts connected with these ganglia, and containing gray 



