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of all his creatures , to be the index of sorrow and cheerfulness , of compassion , of severity , &c . With this we consent and with it we deny . With this we manifest pride and contempt , and other passions that have their sources elsewhere .
Of the structure of the brain and nerves , and of the nature of their powers little is known . We read of the operation of the mind , and frequently measure its powers in the extent of genius and science : but though we can view the astonishing
properties of the brain in their results * we are at a loss to explain how these results are produced . We kuow , however , first , That the brain and nerves constitute the organs of feeling and sensation : for upon touching the brain with a knife or other instrument , the animal is seized with convulsions : and
if a probe be thrust into the spinal marrow all the muscles of the limbs will be violently convulsed . By irritating or tying a nerve , the muscles to which the branches are distributed will' be violently convulsed , and the animal thrown into the most acute pain .
Secondly , All the other parts of the body derive their power of feeling and sensation from the brain , the spinal marrow and the nerves , being in themselves wholly insensible , and made capable of feeling only in proportion as they have the nervous
branches distributed over them : this fact is made evident by tying up a nerve that leads to any part of the body , that part becomes immediately paralytic below the ligature ; but will
recover its powers on freeing the nerve . And it is further proved by the degrees of sensibility of the different parts of the body , bearing proportion to the quantity of nervous branches which can be discovered
to belong to that part . Thirdly . The excitement to all voluntary motion , or to those actions which are produced by the will , flows from the brain or spinal marrow , through the medium of the nerves , or to those parts of the body which we wish to move . For if the brain be
compressed by any cause ,, the body becomes paralysed , and the power of motion is suspended , but on removing the pressure , the paralysis will cease , and the whole frame , unless it has been permanently -injured , will reco-
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ver its sense and action . Again , if a particular nerve , which conveys tfee immediate cause of motion from the brain , or spinal marrow , to a part to be moved , be injured or compressed * the . part to which this nerve is
distributed will become senseless , and lose its power of motion 5 hence injuries of particular nerves produce palsies of the parts to which these are sent , as loss of voice , of hearing , of speech , &c .
Fourthly . The nerves are the organs , and the brain the receptacle of our sensations , and the source of our ideas . That sensation arises from impression made on a nerve and conveyed to it by the brain is evident
from this , that if a nerve be irritated pain is produced , and the mind becomes instantly informed of the suffering : but if that nerve be compressed above the seat of its irritation , so , as to cut off the channel of
communication between it and the brain , the mind is then no longer conscious of any irritation that is made below the point of compression , and the affected parts are reduced to a state of insensibility similar' to that of parts which are destitute of nerves , and may be injured or even destroyed without exciting pain *
Pain is occasioned by disagreeable sensations produced by the forcible contact of bodies with the organs of our senses , and it is wisely planted in the system to guard it against injury , for without pain , as the result of excessive sensations , the delicate structure of our frames would be
almost constantly liable to destruction from various bodies in nature around . But as pain is the salutary consequence of excessive sensations , so sensations without pain are the results of a due impression on our sensitive organs , from the objects that are
calculated to influence us : and as long ; as the body remains in health in all its parts , these impressions will continue to cause sensations in the nerves which will forward them to the brain , where ideas 6 Y the nature and properties of the impressing objects will
be instantly formed for the instruction of the mind . Hence the skin and other parts possessed of what we call feeling is susceptible to the touch , and communicate to the brain and the mind the sensations of hardness , softness , &c . pf such bodies as may
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£ O Natural Theology . No , XII . — the Brain and Nerves .
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Citation
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Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Jan. 2, 1816, page 20, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct2448/page/20/
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