nerves to deep parts alone were intact. In the case of H. we had no means of attacking the problem, for no part of any finger was totally insensitive to cutaneous stimulation.
But we were able to show that the interrupted current could produce sensation by contracting the muscles only. Even the slightest contraction of the abductor indicis or the adductor pollicis produced a distinct sensation of movement, localized in the muscle. No pain was evoked, unless the muscle was thrown into cramp.
(9) Temperature.
The existence of deep sensibility conveys no capacity for appreciating stimulation with any degree of temperature. Ice and water at 60° C. were equally incapable of evoking a response over the affected area of the hand. The parts could be frozen stiffly with ethyl chloride, and H. remained unconscious of any stimulation, provided the normal skin was carefully protected with a thick layer of impervious material.
This freezing produced a numb aching, in no way allied to a thermal sensation, but resembling the "numbness" produced by extended exposure of the hands to severe external cold.
In conclusion, we have shown that the peculiar aptitude possessed by
a part innervated solely by the afferent fibres of a muscular nerve is
the appreciation of all stimuli which produce deformation of structure.
Pressure or jarring contact are quickly appreciated and localized with
remarkable accuracy. "Roughness" is as well recognized on the
affected as on the sound hand.
Two points can be discriminated if applied successively, but not when contact is made strictly simultaneously.
Although pressure is well localized, all sense of relative size is lost over the affected parts.
Excess of pressure produces an aching pain; and the cramp, caused by repeated electrical stimulation of the muscles, is at once appreciated.
Pressure, which ordinarily causes a sensation of touch or of pain, produces no effect upon consciousness when applied to a fold of skin elevated into a ridge, thus proving that the sensations which are present are not due to any end-organs remaining in the skin.
The presence of deep sensibility conveys no power of appreciating any temperature stimulus.
