HYPNOTICS are agents that induce sleep. They may be mental, physical or medicinal. Thus certain kinds of music, the human voice and suggestion may have power to induce sleep, which may also follow from eating, or from a walk, or a warm bath before retiring. All such simple measures should be used before drugs are resorted to in the treatment of in somnia (q.v.). Hypnotics per se may be di vided into two broad groups — those that induce sleep by alleviating pain and those that have no pain-relieving character. The latter are pure hypnotics. Combinations of the two are fre quently employed in medicine. The pain relieving drugs all come under the head of analgesics (q.v.). The pure hypnotics may be divided into a number of groups based on their chemical relationship, for in this class of drugs the relation between chemi cal composition and physiological action is peculiarly close. Alcohol is one of the most prominent of the hypnotics, but while it is extensively used to induce sleep, thepractice of taking a °nightcap') cannot be regarded as a safe one. Substituted alcohols, however, yield some of the most widely employed of all hyp notics. Chloral, paraldehyde, amylene hydrate belong to this series, while from chloral as a basis a number of allied hypnotics have been made. These are chloralamide, chloralose,
chloretone, urethane, etc., which are all re garded as less objectionable than alcohol. They all dilate blood-vessels, relieve spasm and in duce sleep. In large doses they depress the heart action. Another group of hypnotics in cludes substituted sulphur compounds. The most important of these are sulphonal, trional and tetronal. They are all closely allied in chemical structure. Sulphonal is the weakest, tetronal the strongest, trional occupies a middle position. In poisonous doses, and even in small doses if long continued, hypnotics of this group cause a form of chronic poisoning in which the red blood-cells are disintegrated. This is shown by the appearance of a cherry-red or purple-red discoloration in the urine. A third group of hypnotics depends on some form of bromine, as bromides. Sodium bromide, potas sium bromide, bromal bromoform, etc., are representatives. These are regarded as the least objectionable. They depress the activity of the brain and are useful hypnotics. If used very long the bromine compounds cause skin-erup tions, foul breath and heart-depression. See ALCOHOL; CHLORAL; INSANITY; INSOMNIA; NEURASTHENIA; SULPHONAL.