_Dangers._--Absorption of lead follows from the dust generated by each blow, from brushing the dust off the cut file, and from licking the finger and thumb holding the chisel. Other conditions predisposing to plumbism before the present regulations came into force, and not altogether without effect still, were--too close proximity of one stock to another, defective ventilation of the (frequently) small shed in which the work was done, overcrowding, accumulation of dust on the benches, uneven floors, inadequate washing facilities, and, apparently, lack of appreciation of the danger. The remarkable feature of plumbism in this industry is the long duration of employment before pronounced symptoms manifest themselves (see p. 51). The insidious onset is, however, accompanied by an undermining of the constitution, showing itself eventually in atrophy of the muscles, especially of the thenar and hypothenar eminences of the hand, and of the lumbricals and interosseous muscles of the fingers, the result of continual gripping of the hammer and chisel, chronic interstitial nephritis, with its associated arterio-sclerotic changes, and heavy incidence of phthisis. Provision of locally applied exhaust ventilation has never been suggested for this industry, owing to absence of power to drive a fan in the small workshops, and because no lead dust is seen to be given off. Diminution in the number of cases is due to the fact that machine file-cutting (with zinc as the bed) has been substituted for hand file-cutting for coarse files. In hand cutting, in some instances, beds of pewter, or of alloys with comparatively small proportion of lead, have replaced the use of lead beds. The remedial measures prescribed in the regulations have also played a part. At the time the regulations came into force, in 1903, there were about 708 file-cutting shops in the United Kingdom, of which 517 were in Sheffield. Immediately after they came into force 126 certificates of exemption were granted for use of beds containing less than 5 per cent. of lead, and every year fresh applications are received[16]. There does appear, however, to be difficulty in securing beds which conform to the standards laid down. Thus, in the four years 1907-1910, of 23 samples submitted as containing less than 5 per cent., 16 were in excess. The number of reported cases of poisoning in the five years 1900-1904 was 151, and 51 in the five later years 1905-1909. The attack rate is about 10 per 1,000, but, although this may be low compared with other trades, the much greater severity of the attacks has to be borne in mind. =File-Hardening.=--The process consists in keeping the files in a bath of molten lead at high temperature, covered with charcoal. The file is removed when red-hot, straightened if necessary, and plunged into a solution of brine.