To meet these, we have, besides rest from care, change of air, and generous feeding (all of which are of the greatest importance), three sorts of tonics: blood-renewers, appetizers, and nervines. Of the first class, referring to works on Materia Medica for others, the most valuable, in the generality of cases, are iron and cod-liver oil. To the second class belong the vegetable bitters, as gentian, quassia, columbo, chamomile, etc.; and the mineral acids, as aromatic sulphuric acid (elixir of vitroil), and others. Under the third head may be named quinine as most largely and safely applicable to general debility. Physicians also use, in some selected cases, strychnia and phosphorus, as powerful nervine tonics; but they are too dangerous to allow in the family medicine chest for use without medical advice. One preparation, if labelled poison, and kept out of the way of the children and of ignorant servants, may sometimes find safe use as a tonic both to the digestive organs and to the nervous system; tincture of nux vomica; safe in the small dose of ten drops twice or thrice daily.