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XII. " On the Cutaneous Sensibility of the Hand and Foot in 

 different parts of the Surface, as tested by the Continuous 

 Galvanic Current." By HARRY LOBB, Esq. Communi- 

 cated by JOHN SIMON, Esq. Received May 28, 1861. 



Procure a 60-element Pulvermacher's bath battery, excite it with 

 ordinary vinegar, and hang it up free in the air by a piece of cord. 

 Attach conducting wires to the terminal hooks, and to the wire from 

 the copper or positive pole connect a moistened sponge-conductor, 

 which tie round the neck, so that the sponge may rest upon the skin 

 over the middle cervical vertebra. To the wire, from the zinc or 

 negative pole, attach a conductor of smooth metal. 



Upon placing the metal conductor upon the skin of the arm or 

 back of the hand the burning sensation is unbearable for a single 

 moment. 



Upon placing it upon any portion of the skin of the palm, or under 

 surface of the fingers, no pain is experienced, nothing but the touch 

 of the conductor. 



There is, however, a line running down the side of each finger 

 nearer the back than the palmar surface, where painful sensation 

 commences. This line is also to be traced round, between the thumb 

 and first finger, along the back surface of the thumb and the limit 

 between the skin of the palm and the wrist. This line can be easily 

 detected by the eye ; the smooth papillary skin of the palm being in- 

 sensible, whereas the hairy, polygonally reticulated skin of the back 

 of the hand and wrist is acutely sensible. 



The skin on the back of the first phalanges is insensible, and also 

 a part of the way down the second, varying in different persons. If 

 the conductor be placed in the centre of the palm of the hand and 

 held there* with gentle pressure for a minute or two, the idea con- 

 veyed is that of greatly increasing pressure, as if the instrument was 

 being thrust through the palm, until the pain becomes unbearable ; 

 but there is no sensation of burning, pricking, or stinging. The same 

 laws are discovered to hold good in respect to the foot. 



