380 



FIBRES OF THE BRAIN. 



pora restiformia : these are the posterior median fasciculi of the 

 medulla oblongata. 



If a thin layer of the pons Varolii be carefully raised, or if a lon- 

 gitudinal incision be made across it, it may easily be seen that the 

 corpus pyramidale passes through the pons into the crus cerebri. 

 If the crus cerebri be traced forwards, it will be found to enter the 

 thalamus opticus, and leaving it by the opposite border to plunge 

 into the corpus striatum, and pass from thence onwards to the con- 

 volutions of the hemispheres. 



Fig. 127.* 



From pursuing this remarkable course, and spreading out as they 

 advance, these fibres have been called by Gall the diverging fibres. 

 While situated within the pons it is found that the fibres of the cor- 

 pus pyramidale separate and spread out, and have gray substance 



* The base of the 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 crus cerebri crossed by the optic nerve (4), and spreading out 

 into the substance of the middle lobe. 5. The two roots of the optic nerve; 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 the 

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

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

 striatum. 11. Their distribution to the hemispheres. 12. The fifth nerve; its two 

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

 backwards to the corpus restiforme. 13. The fibres of the corpus pyramidale which 

 pass outwards with the corpus restiforme into the substance of the cerebellum ; these 

 are the arciform fibres of Solly. The number rests upon the upper part of the corpus 

 olivare ; the rest of that body having been cut away, the arciform fibres are below the 

 number. 14. A section through one of the lateral lobes of the cerebellum, showing the 

 corpus rhomboideum in the centre of its white substance; the arbor vitae is also beauti- 

 fully seen. 15. The opposite lobe of the cerebellum. 



