Lead poisoning and lead absorption

by Sir Thomas Morison Legge; Kenneth Weldon Goadby

2. The muscles concerned in pronation are of small capacity for work, and are not called on for sustained work.

As for the muscles acting on the wrist and hand, he concludes that the extensors (carpi radialis longior and brevior, carpi ulnaris, and the extensors of the fingers) are powerful, and much exceed in capacity for work the flexors (flexor carpi radialis, flexor carpi ulnaris, the flexors of the fingers, etc.), but in all fine manual work, and specially where close grasping movements enter into association with the flexors, external strain is put upon them, whilst the flexors merely support their action.

The extensor communis digitorum is the weakest of all the long finger muscles; its volume is hardly one-fourth that of the corresponding flexors, and while it acts only on the first of the phalanges, the flexors act on all three. In all fine work they are called on for heavy strain, especially the interossei and the lumbricals, but in harmony with the long flexors when grasping movements are performed. The small muscles of the fingers have nearly the same mass as the extensor communis, and in all fine movements the grasping efforts are taxed severely; but their play is under considerably more favourable physical relations than that of the extensors, whilst in addition they are aided in their work at times by the long flexors. The chief adductor muscle of the thumb (extensor metacarpi pollicis) is particularly powerful; the other extensors of the thumb are very weak, and work under unfavourable physical conditions, but are supported in their action by the strong abductor muscle. The muscles of the abductor, opponens and flexor brevis, in the complicated work thrown on the thumb in manipulation, are much exerted, so that the effects of overexertion show themselves first in this region.

Thus, Edinger maintains that the muscle-supply of the arm is designed for coarse heavy work, the muscles of the fingers and the hand having to carry out more work than can be expected of them from a consideration of their volume and their physical action.

The commonest form of lead palsy, the antibrachial type of Déjerine-Klumpke[5], is explicable from consideration of overexertion of the particular group of muscles named. The supinator muscle, supplied also by the musculo-spiral nerve which serves the paralyzed muscles, escapes because of its size, and the fact that functionally it belongs to the flexor group, and the first-named reason also, explain the frequent escape of the long abductor of the thumb.

Teleky[6] investigated thirteen slight cases of the antibrachial type. In one both hands were affected, in one the left only, and in all the others the right only—facts which he thinks bring out the rule of causation by employment. Of fourteen painters, three had the right forearm affected only, the other eleven both right and left, but always more marked in the right. Amongst them he cites cases where the shoulder muscles were paralyzed, which he considered was due to the extra strain of unusual employment, involving a raising of the arms above the head, or lying on the back painting the under parts of carriages. In several of the painters the index-finger was the least affected, by reason of the less exertion thrown on it by the position assumed in holding the brush between the second and third fingers. The long abductor, probably because of its size and power, is in no case completely paralyzed.

In file-cutters he insists that the predominant share, falling on a single or on several small muscles of the hands, makes the early appearance of paralysis of the small muscles the characteristic sign. In this connection we have frequently observed decrease in the size of the thenar and hypothenar eminences amongst lead rollers; in fact, in the majority of lead rollers who have followed their occupation for a large number of years the flattening of both thenar and hypothenar eminences is well marked, but it is only fair to point out that in these cases very considerable stress is thrown on the muscle of this part of the hand by the pressure of the lead plate in pushing it inwards into the roller and grasping it on its appearance back again through the roller, and that, further, the use of large and clumsy gloves with all the fingers inserted into one part, and the thumb only into the other, tends to produce inaction of portions of the lumbricals and of the opponens pollicis, and may, therefore, from purely mechanical reasons cause damage to this part of the hand.

Teleky[7] cites cases of right-sided paralysis of the adductor brevis pollicis supplied by the median nerve, and partial paralysis of the long extensors and of the extensor ossis metacarpi pollicis supplied by the radial nerve, and in one or two cases complete paralysis of the thenar muscles and adductor, whilst the extensors of the fingers and wrists were only partially paralyzed. The cases all occurred in lead capsule polishers. This particular selection of muscles is clearly the result of the peculiar movement necessary in polishing the capsules of bottles on a revolving spindle, involving specially the use of the opponens muscle.

This observation of Teleky’s is in direct accord with the observation quoted above of the hands of persons engaged in lead rolling.

In the lower extremity, paralysis of the muscles associated also with paralysis of the adductor and extensors of the thumb was found by Teleky in a shoemaker who had contracted plumbism by the use of white lead. He explains this lower extremity paralysis by the exertion thrown on the adductor muscles of the thigh whilst holding the shoes.