Sensory Symptoms and Disorders. 9 



Visceral hypercesthesia is shown in many cases of spasms of in- 

 volnntarj' muscles (colic, arrest of intestinal calculi, gall stones or 

 urinary concretions), and in inflammation of serous membranes 

 (pleurisy, peritonitis). 



Parsesthesia. This is a painful or morbid sensation caused 

 by a lesion in the central nerv'ous structures or in the nerves, but 

 referred by the sufferer to some peripheral organ over which such 

 centre presides. It may even be referred to an organ or part that 

 has been amputated or otherwise removed. This may cause lame- 

 ness of a kind to indicate suffering in a given muscle, tendon or 

 joint, when the cause is purely central. In dourine, sexual acts 

 are excited which have their real source in the nerve centres. 

 The rabid dog snaps at imaginary flies in mid-winter, when such 

 insects are only phantoms of his brain. 



Pressure on a nerve trunk induces sensations of tingling, 

 vibration, formication, heat, cold, and paresis, referred hy the 

 mind to the part to which that nerve is distributed, and when the 

 pressure is removed these sensations recede in the order in which 

 they came. This may explain some occult cases of lameness. 



Itching may be a pure, persistent neurosis without any skin 

 lesion. Treatment should then be addres.sed to the nervous sys- 

 tem. 



Anaesthesia, or absence of .sensation, is in its degree partial or 

 complete. The latter is familiar as occurring in parts the sensory 

 nerves of which have been cut acro.ss, also in parts the sensory 

 nerve or nerve centres of which have become completely degene- 

 rated. There is no response to the prick of a needle, the touch 

 of a hot wire, to pinching or cutting. If the nerve remains intact 

 as far as the spinal centres, reflex action may still occur, but the 

 patient himself has no consciousness of this nor of the injur}' 

 causing it. Accordingh^, he makes no movement of head, ears, 

 eyes, or other parts still dominated by the brain. 



In partial or imperfect anaesthesia the response to irritation 

 is less marked and may be even delayed. In some forms of cen- 

 tral lesions the response to a prick may be delayed two, five, or 

 ten .seconds, or even more. 



AiicEsthesia causes awkwardness or uncertainty of movement, 

 especially if the subject is blindfolded. 



Anccsthesia may be induced by medicine, as in the general 



