OF THE FACIAL NERVE. 231 



Having distinguished that symmetrical system of nerves, the functions of 

 which are sensation and volition, we find nerves which at first appear super- 

 fluous. But these superadded nerves, although they produce, when entangled 

 with the others, the appeai-ance of extreme intricacy, are, when taken separately, 

 regular also. For we trace all to a centre, and that centre giving them an origin 

 and a source of power diflerent from the other nerves. 



When we see to what order of parts these nerves are distributed, it is impos- 

 sible to refuse to them the term of Respiratory Nerves. The distinction of ani- 

 mal functions fi-om vital and natural, has always been noticed, and the distinc- 

 tion explained on the supposition of distinct nerves ministering to each ; which 

 suggestion was resigned, because anatomists would not agree to any such distinc- 

 tion of nerves. Nevertheless the reasoning was just, and the objection of the ana- 

 tomists unfounded. 



Comparative anatomy affords us the most pleasing view of this respiratory 

 system. From the lowest link of the chain of beings to the highest, there is a 

 progressive series of nerves, increasing in complexity. It is natural to inquire, 

 On what does this complexity depend ? In the lower link of the chain of animals, 

 we see the essential operation of decarbonization performed by the contact of air 

 with the fluids circulating over aU the Jframe. We see the same object attained 

 by a sac or cavity, which admits the air, and which sac alternately opens and 

 closes again in other creatures ; such cavities commimicate with the atmosphere 

 through prolonged and intricate tubes. Witnessing aU this, we also perceive the ne- 

 cessity of new nerves of connection. When we ftirther see a new power or faculty 

 bestowed by means of the air which plays through these tubes — ^voice issuing by 

 their vibration ; when we observe that the an- drawn thi-ough the tubes is diverted 

 into another channel, and made subservient to smeUing ; when, stiU ascending to 

 the highest link of the scale, we find the faculty of speech bestowed through the 

 same means, — it would be strange, indeed, if anatomy did not in the same as- 

 cending scale disclose an increasing number of nerves. 



Again, in the mouth and in the throat are two passages. How shall the one 

 only admit air, and the other food ? How shall breathing, deglutition, and speech, 

 coughing, vomiting, be performed, each action differing from another, in the ar- 

 rangement of some fifty muscles of these tubes ? How are these actions ordered, 

 but by a minute and seemingly intricate supply of nerves ? 



In aU animals, man included, the same symmetrical system of nerves, im- 

 varying in any essential circumstance, is devoted to sensibility and locomotion. 

 But the other system, that which is superadded, varies in a remai'kable manner ; 

 comparatively simple in the animals which merely breathe, complex when the 

 organs of breathing become instruments under the will, they are at once essential 

 to life, and in their higher office minister to the quaMties of mind. It would be a 

 strange anomaly, if, with these new faculties, sympathies, and relations, there 



