CHAP. IX.] ENDOWMENTS OF NEKVE-FIBKES. 233 



patient complains of pains or tingling, which he refers to the am- 

 putated fingers or toes. 



It may be stated, in confirmation of the view above taken, that 

 in many cases of complete paralysis of a limb from cerebral disease, 

 the patient is not conscious of its presence, and really feels as if it 

 did not exist. We have known instances in which this unconscious- 

 ness has been so great, that when the paralyzed part came in contact 

 with some sensitive portion of his body, the patient for a time be- 

 lieved it to belong to another person, or imagined it some entirely 

 foreign substance. In such cases the affection of brain necessary to 

 create the feeling cannot be produced in consequence of the morbid 

 state of that organ. 



The distinction which has been made between nerves of common 

 and of special sensation, is indicated by the fact, that while a sti- 

 mulus to the former causes pain, that to the latter gives rise to a 

 peculiar or special sensation, as of light, sound, or taste. These nerves 

 are so organized at their periphery as to be peculiarly adapted to re- 

 ceive impressions from the agents to which they specially respond : 

 and in this, as well as in their connexion with some special part of 

 the great centre of sensibility, consist their main anatomical pecu- 

 liarities (see p. 56). 



The same law of nervous action applies to these nerves as to those 

 of common sensation. Thus, their ordinary mode of action is to 

 propagate to the centre impressions made at the periphery; but 

 irritation at any part of them may give rise to their peculiar sen- 

 sation ; and if the brain be stimulated at the part whence these 

 nerves arise, similar sensations are produced. Such phenomena of 

 vision and hearing, to which the term subjective has been applied, 

 are familiarly known to practitioners, as not unfrequent forerunners 

 of more serious symptoms of cerebral disease. Muscae volitantes, 

 ocular spectra, tinnitus aurium, are instances of these phenomena, 

 which, although of every~day occurrence, ought always to excite the 

 attention of the medical man, as indicating some departure from the 

 normal state of the optic or auditory nervous apparatus. Pressure 

 on the eyeball, a galvanic current passed through it,* rotation of 

 the body, are capable of giving rise to similar phenomena, by 

 exciting the retina, or the central connexions of the optic nerve. 

 A sense of giddiness, similar to that produced by the means last 

 named, is also a very common symptom of cerebral affection arising 

 from a disturbed circulation, or from the blood being defective in 



* A strong sensation of a flash of light may be produced by passing a gal- 

 vanic current in the close vicinity of the eyeball. 



