FIBRES OF THE BRAIN. 429 



Observing this remarkable increase in the white fibres, apparently 

 from the admixture of grey substance, Gall and Spurzheim considered 

 the latter as the material of increase or formative substance to the 

 white fibres, and they are borne out in this conclusion by several 

 collateral facts, among the most prominent of which is the great vascu- 

 larity of the grey substance ; and the larger proportion of the nutrient 

 fluid circulating through it, is fully capable of effecting the increased 

 growth and nutrition of the structures by which it is surrounded. 

 For a like reason the bodies in which this grey substance occurs, are 

 called by the same physiologists " ganglia of increase" and by other 

 authors simply ganglia. Thus the thalami optici and corpora striata 

 are the gangiia of the cerebrum ; or, in other words, the formative 

 ganglia of the hemispheres. 



The fibres of the corpora pyramidalia are not all of them destined to 

 the course above described ; several fasciculi curve outwards to 

 reach the corpora restiformia, some passing in front and some behind 

 the corpus olivare on each side. These are the ardform fibres, and 

 they are distinguished by Mr. Solly into the superficial and deep cere- 

 bellar fibres. In the pons Varolii the continued or cerebral fibres 

 (Solly) of the corpus pyramidale are placed between the superficial 

 and deep laj r ers of transverse fibres, and escaping from the pons, con- 

 stitute the inferior and inner segment of the crus cerebri. From the 

 crus cerebri they pass for the most part beneath the thalami optici 

 into the corpora striata. 



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

 fasciculi siliquae, are separated by that body into two bands ; the 

 innermost of the two bands,/w2*/MS siliquce internus, accompanies the 

 fibres of the corpus pyramidale into the crus cerebri. The funicidus 

 KiliqucB extemus unites with a fasciculus proceeding from the nucleus 

 olivae and the combined column ascending behind the crus cerebelli 

 divides into a superior and an inferior band. The inferior band 

 proceeds with 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 processus e cerebello ad 

 testes, and crossing the latter obliquely enters the corpora quadrige- 

 mina. 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 between 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 ganglia of increase, and then expand on all sides so as 

 to constitute the cerebellum. 



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

 medulla oblongata behind the corpora olivaria, and more or less appa- 

 rent between these bodies and the corpora restiformia two large bun- 

 dles of fibres, the fasciculi innominati. These fasciculi ascend behind 



