232 SIR CHARLES BELL ON THE ORIGIN AND COMPOUND FUNCTIONS 



were not also an increasing complication of nerves. This intricacy, this fine de- 

 pendence of the functions, render experiments delusive and unsatisfactory. For 

 we may divide a nerve, one which appears to our conception essential, and no conse- 

 (|uent results ! We cut a nerve going to the tongue or the throat, and the animal 

 breathes, barks, and swallows. It would be dangerous therefore to conclude that 

 the nerve were superfluous. It is only by an enlarged view of the anatomy that 

 we shall be brought to just conclusions. 



From this system I have to select one nerve, and shew how through it, two 

 distinct offices — vital respiratory actions, and voluntary actions — are combined 

 in the face. 



The base of the brain being carefuUy taken out, without tearing the roots of 

 the nerves, and the whole being for a twelvemonth preserved in spirits, we may 

 commence the dissection. The medulla oblongata and 2)ons vaivlii being cleared 

 of their membranes, and the places of the sixth and ninth nerves noted, we 

 clear and arrange the filaments of the eighth pair, and the portio dura of the 

 seventh. 



We see the facialis or portio dura of the seventh nerve coming out from the 

 depth between the convexity of the pons or nodus cerebri, the corpus olivare, and 

 the root of the auditory nerve. This nerve we have now to trace inwards, and 

 in the substance of the pons or nodus. 



We shall not find this nerve arising in separate filaments, but in a flat layer 

 of nervous matter, which fan-like spreads into the nodus. 



To understand the fuU consequence of this form of the root, we must make 

 a section of the nodus or pons, to shew the manner in which the motor tract ex- 

 pands within it. Previous to this let the sixth nerve, and portio dura of the 

 seventh, be thrown forwards, and the glosso-pharyngeal and nervus vagus laid 

 aside. If we now dissect close round the corpus olivare, the motor column will 

 be found bending round that body ; and now, by following the root of the portio 

 dura inwards, its origin from the column of voluntary motion wiU be apparent. 

 One portion diverging towards the sixth nerve, the other towards the glosso- 

 pharyngeal nerve. See Fig. 3, (6, 7, and 8,) also Fig. 4, in which the relations of 

 the nerves are made more distinct. By proceeding differently, we obtain a bet- 

 ter view of the common origin of the eighth pair and poi'tio dura. Cut across the 

 processus ad cerebellum, and open up the fourth ventricle. Trace the roots of the 

 eighth pah- inwards. You find the column from which they arise in the form of 

 a tractus ascending to the corpora quadrigemina, the vahula cereb7n forming the 

 commissure of the two respiratory tracts. From this tract the portio dura, now 

 viewed from behind, will be seen to take an origin. 



We may now have a view of the relation of the respiratory nerves to the 

 sensitive column of the medulla oblongata, either by tracing up the sensitive column 

 from the spinal marrow, or by tracing down the sensitive root of the fifth nerve. 



