Table XIV

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Organ of touch

The hand is presented here as the most important organ of touch. One of the models reproduces the palm covered by the tegument and shows the thenar and hypothenar eminences along the two margins, and the digito-palmar pad in front of the roots of the last four fingers. Among these prominences there is the depression of the hand (‘puculum Diogenis’ of old anatomists) with all its creases. The other model shows the distribution of the cutaneous nerves on the palmar face.

One can see, over the abductor pollicis brevis, the ventral branch of the trifurcation of the superficial branch of the radial nerve which, after having detached a few small branches, courses along the thumb as its lateral dorsal digital nerve. Medial to the thenar eminence, deep to the arch formed by the superficial palmar artery, we have the first common palmar digital nerve of the median nerve; here only the lateral pal mar digital nerve of the thumb and that of the index finger are visible.

One can also observe, between the first three tendons of the flexores digitorum superficial (sublimis) and profundus and the superficial arterial arch, the second and the third common palmar digital branches of the median nerve which are then divided into the digital medial palmar nerve of the index finger and the lateral of the middle finger, into the medial of the middle finger, and into the lateral nerve of the ring finger. Over the hypothenar eminence we can also find the two terminal branches of the ulnar nerve; medially one can therefore recognize some of the ramifications of its dorsal branch for the hand, that are laid upon the abductor digiti minimi muscle while, laterally, the palmar cutaneous branch is visible.

The latter descends around the lateral border of the pisiform bone and divides into the deep and the superficial branches, the first one goes between the abductor and flexor digiti minimi brevis and the second originates the medial pal mar digital nerve of the little finger, and the fourth common digital palmar nerve which then divides into the two pal mar medial digital nerves of the ring finger, and the lateral one of the little finger (the first of these is cut whilst the second is hidden under the cutis).

The two other models reproduce the two distal phalanges of a finger dissected longitudinally and the last phalanx of the thumb (enlarged) with its nail removed in order to show the nail bed and its epidermis raised to demonstrate the dermal ridges.

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