NERVOUS SYSTEM. 261 



intended that this sentient being shall be capable of per- 

 ceiving. As these objects can, in the first instance, make 

 impressions only on the organs situated at the surface of the 

 body, it is evidently necessary that some medium of com- 

 munication should be provided between the external organ 

 and the brain. Such a medium is found in the nerves^ which 

 are white cords, consisting of bundles of threads or fila- 

 ments of medullary matter, enveloped in sheaths of mem- 

 brane, and extending continuously from the external organ 

 to the brain, where they all terminate. It is also indispen- 

 sably requisite that these notices of the presence of objects 

 should be transmitted instantly to the brain; for the slightest 

 delay would be attended with serious evil, and might even 

 lead to fatal consequences. The nervous power, of which, 

 in our review of the vital functions, we noticed some of the 

 operations, is the agent employed by nature for this import- 

 ant office of a rapid communication of impressions. The ve- 

 locity with which the nerves subservient to sensation trans- 

 mit the impressions they receive at one extremity, along 

 their whole course, to their termination in the brain, exceeds 

 all measurement, and can be compared only to that of elec- 

 tricity passing along a conducting wire. 



It is evident, therefore, that the brain requires to be fur- 

 nished with a great number of these nerves, which perform 

 the office of conductors of the subtle influence in question; 

 and that these nerves must extend from all those parts of the 

 body which are to be rendered sensible, and must unite at 

 their other extremities in that central organ. It is of espe- 

 cial importance that the surface of the body, in particular, 

 should communicate all the impressions received from the 

 contact of external bodies, and that these impressions should 

 produce the most distinct perceptions of touch. Hence, we 

 find that the skin, and all those parts of it more particularly 

 intended to be the organs of a delicate touch, are most abun- 

 dantly supplied with nerves; each nerve, however, commu- 

 nicating a sensation distinguishable from that of every other, 

 so as to enable the mind to discriminate between them, and 



