452 THIRD REPORT — 18.33. 



orders of animals from indirect or remote impression, and the 

 operation of all remedies which act through the medium of the 

 sensibility. 



The mode in which the sentient substance is arranged, its 

 more or less minute subdivision, and the degree of arterial 

 vascularity, determine the phaenomena of sensibility as they 

 come under our observation. Hence, we find that the brain, 

 even different parts of it, the spinal marrow, the trunks of the 

 nerves, and their sentient extremities, are so differently en- 

 dowed, that we might be almost led into the error of supposing 

 them all composed of different materials. 



It is well known to surgeons and to experimental physiolo- 

 gists, that the brain is not endowed with any feeling, in the 

 common meaning of the word. It may be wounded without 

 any sense of pain to the individual. 



The trunks of the nerves not possessing the arrangement of 

 the sentient substance suitable to common sensation can only 

 transmit the feeling of pain. Thus, patients after amputation 

 often complain of pain in the part that has been removed ; but 

 the author believes that in no instance have they experienced 

 natural or agreeable sensations, or have expressed a conscious- 

 ness of the presence of the removed limb unattended with 

 pain. 



The sentient extremities of nerves are alone capable of being 

 affected by narcotic poisons. Half a tea-spoonful of the es- 

 sential oil of almonds introduced into the substance of the 

 brain of a rabbit did not produce the least effect on the ani- 

 mal, nor was any effect produced by placing the end of the 

 sciatic nerve in a spoonful of the essential oil of almonds 

 during half an hour, although the animal was afterwards killed 

 in the usual manner by a few drops of this liquid on the 

 tongue. 



Impressions on the extremities of nerves sent to the organs 

 of sense and to the external surfaces of the body are attended 

 with consciousness in the individual, whilst those naturally 

 made on the interior surfaces cause no perception. These 

 surfaces, however, are amply supplied with nerves, and possess 

 a high degree of local sensibility, by which they not only 

 discern mechanic forms, but qualities in food and medicines 

 that the perceptive powers of the individual cannot distinguish. 

 These internal and unperceived sensations are continually 

 though secretly influencing the condition of the whole nervous 

 system, and are often the cause of remote morbid actions. 

 Under some circumstances movement follows impression made 

 on the external parts of the body after consciousness has be- 



