We show in a later chapter that the excretion of lead in persons tolerant of the metal takes place through the medium of the bowel, and that probably those individuals who are engaged in what are recognized as dangerous processes in lead industries, and yet show no signs of illness, have established a kind of balance between the intake of the poison and its excretion by the bowel. It is rarely possible in such persons to find any lead excreted through the kidney. Occasionally, however, such persons, after working a considerable time in a dangerous lead process, become suddenly poisoned, and inquiry frequently discloses the fact that some disturbing factor, either intercurrent illness, alcoholic excess, etc., has occurred, or that the breathing of a big dose of dust has precipitated the symptoms of general lead poisoning. On the other hand, the experience of all persons engaged in the routine examination of lead workers is that, although a worker may show signs of lead absorption as distinguished from definite lead poisoning during the earlier period of his employment, he later shows less and less signs of the influence of the poisonous substance; even a mild degree of definite poisoning in the early stages of work in a lead process does not seriously militate against this gradually acquired tolerance, whilst careful treatment during such a time as the man is acquiring tolerance to the poison frequently tides him over the period, and enables him to withstand the ordinary dangers attached to his work. The earliest symptom of lead absorption is anæmia. The anæmia is not very profound, and the diminution in the red blood-cells rarely reaches as low as 2,000,000 per c.c., the hæmoglobin remaining somewhere between 75 and 80 per cent. Some loss of orbital fat, as well as fat in the other parts of the body, occurs, but beyond this no obvious clinical signs of poisoning exist. Should such persons possess unhealthy gums, a blue line rapidly makes its appearance, but where the gums are healthy it is unusual to see any sign of deposit in this prodromal stage.