Chem. [mod. f. ALKALI + -OID. Cf. mod. Fr. alcaloïde.] A body resembling an alkali in properties. Applied gen. to all nitrogenous basic substances, natural or artificial, with alkaline reaction (Nitrogen alkaloids), or to all nitrogenous organic bases, whether animal or vegetable (Organic alkaloids); spec. to the Vegeto-alkaloids or Vegetable alkalis, a series of highly complex organic bases found in many plants, having mostly a very bitter taste, and powerful action on the animal system, the first of which to be discovered was morphine in 1817. Chemically they may be regarded as substitution compounds of ammonia. (The names of organic alkaloids are regularly formed in -ine, as nicotine, strychnine, quinine, aconitine, theine.)
1831. Ure, Dict. Chem., 135. They are called by the German chemists alkaloids.
1833. Penny Cycl., I. 158. The detection of the alkaloids in cases of poisoning by them.
1863. Watts, Dict. Chem. (1879), I. 120. The number of natural alkaloids now known is very great, and includes many substances which cannot in any strict sense be called alkalis.
1874. Roscoe, Elem. Chem., 427. The alkaloids act most powerfully on the animal economy; some, such as strychnine, nicotine, &c., form the most violent poisons with which we are acquainted, whilst others, such as quinine and morphine, act as most valuable medicines.
2. attrib. or adj.
1859. in Worcester.
1882. T. Stevenson, in Echo, 11 March, 3/2. An alkaloid extract which contained a trace of morphia.
