106 



NERVOUS SYSTEM. 



pansions of the columns of the spinal marrow and medulla oblongata, 

 and to terminate by radiating fibres on the periphery of the brain ; as 

 well as to those of M. Desmoulins, 1 and others who regard the convolu- 

 tions as the seat of the mind. We have, however, cases on record, that 

 signally conflict with this view of the subject ; in which the cortical 

 substance has been destroyed, and yet the moral and intellectual mani- 

 festations have been little, if at all, injured. Many years ago, the 

 author dissected the brain of an individual of rank in the British army 

 of India, in the anterior lobes of which neither medullary nor cortical 

 portion could be distinguished, both one and the other appearing to 

 be broken down into a semi-purulent, amorphous substance ; yet the 

 intellectual faculties had been nearly unimpaired ; although the morbid 

 process must have been of some duration. 



The encephalon affords us many striking instances of the different 



effects produced by sudden, 



Fig- 30 - and by gradual interference 



with its functions. Whilst a 

 depressed portion of bone or 

 an extravasation of blood may 

 suddenly give rise to the abo- 

 lition of the intellectual and 

 moral faculties, gradual com- 

 pression by a tumour may 

 scarcely interfere with any of 

 its manifestations. 



The circulation of blood in 

 the encephalon requires notice. 

 The arteries are four in num- 

 ber, two internal carotids, 

 and two vertebrals: to these 

 may be added the spinal or 

 middle artery of the dura 

 mater, arteria meningsea me- 

 dia. The carotid arteries 

 enter the head through the 

 carotid canals, which open on 

 each side of the sella tur- 

 cica, or of the chiasma of the 

 optic nerves. The vertebral 

 arteries enter the head through 



1. Vertebral arteries. 2. Twoanteriorspinalbranch.es the foramen magnum of the 



uniting to form a single vessel. 3. One of the posterior r\r*n\r\\ts\] hrmp nrnrp rm fViP 



spinalarteries. 4. Posterior meningeal. 5. Inferior cere- OCClpltal DOnC , I 



bellar. 6. Basilar artery giving off its transverse branches medulla Oblongata to form the 



basilary artery, which passes 

 forward along the middle of 

 the pons varolii ; and, at the 

 anterior part of the pons, gives 

 off lateral branches, which 



Circle of Willis. 



to either side. 7. Superior cerebellar artery. 8. Posterior 

 cerebral. 9. Posterior communicating branch of the in- 

 ternal carotid. 10. Internal carotid, showin the curva- 



ing 

 hal 



tures it makes within the skull. 11. Ophthalmic artery 

 divided across. 12. Middle cerebral artery. 13. Anterior 

 cerebral arteries connected by, 14. Anterior commumcat- 



ing artery. 



Anatomie des Systemes Nerveux des Animaux a Vertebres, p. 599, Paris, 1825. 



