OF THE RESPIRATORY ORDER OF NERVES. 73 



IV. Of the Respiratory Order of Ncnvs. All animals that possess a perfect cerebrn- 

 spinal system have an intermediate order of nerves which connect the vegetative func- 

 tions of the ganglial system with the functions of the encephalon. This order of nerves 

 has lately been very satisfactorily examined into, both as respects their distribution and 

 functions by Mr. Charles Bell. 



On investigating- the minute structure of the nerves whih, both in man and in the 

 lower animals, arise from the spinal marrow by double roots, and those which proceed 

 from the medulla oblongata, by single origins, to the organs of respiration and those 

 parts of the face and trunk which evince an intimate relation with this important func- 

 tion, Mr. Bell perceived their texture and mode of distribution were very different. 

 This circumstance led him to consider that two distinct orders of nerves must exist in- 

 dependently of the sympathetic, the one simple and uniform, the other irregular and 

 complex in proportion to the complexity of the organization. The former he has called 

 original or symmetrical, the latter supcradded or irregular. In the superadded class of 

 nerves, which are chiefly devoted to the function of respiration, Mr. Bell arranges, 1st, 

 the par vagum ; 2d, the portio dura ; 3d, the spinal accessory ; 4th, the phrenic ; 5th, 

 the external respiratory nerves, &c. " The nerves,'* this Physiologist states, " on which 

 the associated actions of respiration depend, and which have been proved to belong to 

 this system, by direct experiment, and the induction from anatomy, arise very nearly 

 together. Their origins are not in a bundle, or fasciculus, but in a line or series, and 

 from a distinct column of the spinal marrow. Behind the corpus olivare, and anterior to 

 that process which descends from the cerebellum, the corpus retiforme, a convex slip of 

 medullary matter, may be observed ; and this convexity, or fasciculus, or virga, may be 

 traced down the spinal marrow, betwixt the sulci, which give rise to the anterior and 

 posterior roots of the spinal nerves. This portion of medullary matter is narrow above 

 where the pans varoUi overhangs it. It expands as it descends ; opposite to the lower 

 part of the corpus oli-vare it has reached its utmost convexity, after which it contracts a 

 iittle, and is continued down the lateral parts of the spinal marrow." 



From this tract of medullary matter on the side of the medulla oblongata, arise in 

 succession from above downwards the portio dura, the glosso-pharyngeus, the par vagum t 

 the nervus accessorius, the phrenic, and the external resfriratory. These superadded 

 nerves are comparatively but little sensible ; they do not arise by double roots, as the 

 symmetrical do : and they have no ganglia on their origins, and while the other volun- 

 tary nerves have large, free, and round filaments, they have a close, loose texture, re- 

 sembling a minute plexus. " These are the nerves which give the appearance of con- 

 iusion to the dissection, because they cross the others, and go to parts already plenti- 

 i'ully supplied from the symmetrical system." 



From these anatomical investigations, and from experiments made in order to ascer- 

 tain the exact functions of this order of nerves, Mr. C. Bell and Mr. Shaw have drawn 

 some important inferences ; 1st, They consider that the portio dura of the seventh 

 pair " produces all those motions of the nostrils, lips, or face generally, which accord 

 with the motions of the chest in respiration. When cut, the face is deprived of its con- 

 sent with the lungs, and all expression of emotion. 2d, The par vagum associates the 

 larynx, the lungs, the heart, and the stomach with the muscular apparatus of respira- 

 tion. 3d. The spinal accessory controls and directs the operations of the muscles of 

 the neck and shoulder, in the offices of respiration. 4th, The phrenic nerve has its 

 functions sufficiently characterized in the name of internal respiratory, which Mr. Bell 

 has assigned it. 5th, The glossopharyngeal nerve, &c. ; and, 6th, the external respira- 

 tory nerve, perform the functions which those parts, to which they are distributed, 

 have in connexion with the operations of respiration. 



act in the manner of a voltaic pile, and to transmit, under the direction of the brain, 

 and through the channel of the spinal cord and nerves, the moving principle to the 

 muscles. Mr. Flourens, as we have shown, views this organ as the regulator and ba- 

 lancer of the muscular contractions. M. Magendie regards it as requisite to the pro- 

 iluction of motion forwards : and Mr. C. Bell, Messrs. Fodera, Foville, and Pin el- Grand - 

 champ are of opinion, that it is the seat of sensibility. 



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