In _dyeing_ and _printing_ use of poisonous colours is lessening, as they have been supplanted by aniline colours. On occurrence of aniline poisoning in aniline black dyeing see the section on Aniline. Use of lead colours and of chromate of lead are dealt with in special sections. PART II _THE SYMPTOMS AND TREATMENT OF INDUSTRIAL POISONING_ In this section the most important diseases and symptoms of industrial poisoning will be described. In doing this—considering the mainly practical purpose of this book—theoretical toxicological details and any full discussion of disputed scientific points will be omitted. I. INTRODUCTORY Hitherto in this book we have intentionally followed the inductive method, from the particular to the general: we began by citing a number of important instances of industrial poisoning, but only now will endeavour be made to give a definition of the terms ‘poison’ and ‘poisoning.’ Attempts at such definitions are numerous; every old and new text-book of toxicology contains them. A few only hold good for our purpose. It is characteristic that Lewin, after attempting a definition of the conception ‘poisoning,’ himself rejects it and declares that he can see no practical disadvantage in the impossibility of defining this notion, because deductions based upon the knowledge of undoubted cases can never be dispensed with, even if a definition were possible: one justification the more for our inductive method. But we will not quite dispense with a definition. _Poisons are certain substances which are able chemically to act on an organism in such a way as to effect a permanent or transient injury to its organs and functions; an injury consequently to the health and well-being of the person affected; this injury we call poisoning._ In the present book we have refrained from including industrial infections among industrial poisonings, and the subject has been limited to poisoning in the restricted and current sense of the word. An industrial poison is a poison employed, produced, or somehow occasioned in industrial occupation, which is brought about inadvertently, and consequently against the will of the person poisoned. From a simple survey of the action of industrial poisons in general we may group them as follows: 1. Poisons which act _superficially_, i.e. which cause in the organs which they touch gross anatomical lesions (irritation, corrosion, &c.)—so-called contact-effect. To this class belong especially irritant and corrosive poisons. 2. _Blood_ poisons, i.e. poisons which are absorbed by the blood and change it; this change can affect either the blood colouring-matter, with which certain poisons form chemical compounds, or the blood corpuscles themselves can be altered or destroyed (for instance, poisons having a hæmolytic action).