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 rare, and they were compelled to attack the problem by indirect and less satisfactory methods. As soon, therefore, as it was determined to make an experimental division of peripheral nerves, means were taken to ensure that the nature of these deep afferent fibres should come clearly to experimental investigation.

At the time of the experiment, H. was nearly 42 years of age and in perfect health. Since boyhood he had suffered from no illnesses, excepting as the consequence of wounds in the post-mortem room. None of these had attacked his left arm or hand, which were entirely free from scars or other deformities.

For two years before these experiments began he had given up smoking entirely. No alcohol was ever taken on the days during which he was under examination, and for some years he had abstained from alcohol except on holidays.

On April 25, 1903, the following operation was performed by Mr. Dean, assisted by Mr. Sherren.

An incision 6½ in. (16·5 cm.) long was made in the outer bicipital fossa extending along the axial line of the left upper extremity; this wound was almost exactly bisected by the fold of the elbow. After turning back the skin, the supinator longus was hooked outwards, and the radial nerve (ramus superficialis nervi radialis) was divided at the point where it arises from the musculo-spiral (N. radialis). A small portion was excised, and the ends united with two fine silk sutures. The external cutaneous nerve (N. cutaneus antibrachii lateralis) was also divided where it perforates the fascia, above the point where its two branches are given off to supply the anterior and posterior aspects of the pre-axial half of the forearm. The nerve was sutured with fine silk, and the wound was closed with silk sutures, without drainage. The limb was put up on a splint with the forearm flexed at the elbow, and the whole hand was left free for testing. The wound healed by first intention.

The following morning (April 26, 1903), the radial half of the back of the hand and dorsal surface of the thumb were found to be insensitive to stimulation with cotton wool, to pricking with a pin, and to all degrees of heat and cold. Around the base of the index and middle fingers was a small area insensitive to stimulation with cotton wool and von Frey's hairs, where a response was obtained to the prick of a pin. No sensation was evoked by any manipulation of the hairs within the affected parts on the back of the hand.