FIBRES OF THE BRAIN. 



387 



quit that body greatly increased in number and bulk. Precisely the same 

 change takes place in the corpus striatum, and the fibres are no\v so extra- 

 ordinarily multiplied as to be ca- 

 pable of forming a large proportion g< 173> * 

 of the hemispheres. 



Observing this remarkable in- 

 crease in the white fibres, appa- 

 rently from the admixture of grey 

 substance, Gall and Spurzheim 

 considered the latter as the mate- 

 rial of increase or formative sub- 

 stance 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 vascularity of the grey sub- 

 stance; and the larger proportion 

 of the nutrient fluid circulating 

 through it is fully capable of effect- 

 ing the increased growth and nu- 

 trition of the structures by which 

 it is surrounded. For a like rea- 

 son, 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 ganglia 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 cor- 

 pora restiformia, some passing in front and some behind the corpus olivare 

 on each side. These are the arciform fibres, and they are distinguished. 

 by Mr. Solly into the superficial and deep cerebellar fibres. In the pons 

 Varolii the continued or cerebral fibres (Solly) of the corpus pyramidale 

 are placed between the superficial and deep layers of transverse fibres, 

 and escaping from the pons, constitute the inferior and inner segment of 

 the crus cerebri. From the crus cerebri they pass for the most part be- 

 neath the thalami optici into the corpora striata. 



$ 



* The base of tlie brain, upon which several sections have been made, showing the 

 distribution of the diverging fibres. 1. The medulla oblongata. 2. One half of the pons 

 Varolii. 3. The cms cerebri crossed by the optic nerve (4) and spreading out into the 

 hemisphere to form the corona radiata. 5. The optic nerve near its origin; the nerves 

 about the crus cerebri and cerebelli are the same as in the preceding figure. 6. The 

 olfactory nerve. 7. The corpora albicantia. On the right side a portion of the brain 

 has been removed to show the distribution of the diverging fibres. 8. The fibres of tbo 

 corpus pyramidale passing through the substance of the pons Varolii. 9. The fibres 

 passing through the thalamns opticus. 10. The fibres passing through the corpus 

 striatum. 11. Their distribution to the hemisphere. 12. The fifth nerve: its two roots 

 may be traced, the one forwards to the fibres of the corpus pyramidale, the other back- 

 wards to the fasciculi teretes. 13. The fibres of the corpus pyramidale which pass out- 

 wards with the corpus restiforme into the substance of the cerebellum ; these are the 

 arciform fibres of Solly. The fibres referred to are those below the numeral, the nu- 

 meral itself rests upon the corpus olivare. 14. A section through one of the hemi 

 ppheres of the cerebellum, showing the corpus rhomboideum in the centre of its white 

 substance; the arbor vitae is also seen. 15. The opposite hemisphere of the cere- 

 Dellum 



