1. =Xanthic Leucomaines.=--The bases of this group appear to have a composition resembling that of uric acid. When hydrolyzed, they yield urea and guanidine. They are weak bases, and exhibit both basic and weakly acid properties. They all possess the common characteristic of being precipitated by copper acetate in acid solution with heat, and by ammoniacal silver nitrate in the cold. According to Kossel, these bases are derived from the nucleo-albumins which are found in the cell nuclei, and which are, as we know, substances rich in nitrogen and phosphorus. Among the bases of this group may be mentioned _adenine_, C{5}H{5}N{5}, which is obtained from infusions of tea.[15] This base is non-toxic; it was discovered by Kossel,[16] and it crystallizes easily. [15] KRUGER: _Bull. Soc. Chim._ (3), VIII, p. 687. [16] KOSSEL: _Zeitschrift für physiol. Chim._, X, p. 248; and _Bull. Soc. Chim._ (3), III, p. 239. Some others of this group are: _Guanine_, C{5}H{5}N{5}O, non-toxic, discovered by Unger; _pseudo-xanthine_, obtained from muscular tissues; _sarcine_, C{5}H{4}N{4}O, also but slightly toxic, discovered by Scherer; _xanthine_, C{5}H{4}N{4}O{2}, which is found in many urines, and which acts as a stimulant on the cardiac muscles; _paraxanthine_, C{7}H{8}N{4}O{2}, a toxic base found in certain pathological urines; _caffeine_ and _theobromine_, powerful diuretic bases; and _carnine_, C{7}H{8}N{4}O{3}, from meat, a muscular stimulant like caffeine. 2. =Creatinic Leucomaines.=--These have for their type guanidine; they differ from the xanthic bases in that they are not precipitated by copper acetate, but frequently are by ammoniacal silver nitrate. They yield double salts with the chlorides of zinc and cadmium. To this group belong _glycocyanine_, C{3}H{7}N{3}O{2}, and _glycocyanidine_, C{3}H{7}N{3}O, both very toxic; _creatine_, C{4}H{9}N{3}O{2}, only slightly toxic; _creatinine_, C{4}H{7}N{3}O; _lysatine_, which very easily decomposes to form urea; _lysatinine_, _xanthocreatine_; _arginine_, a vegetable base, etc. 3. =Neurinic Leucomaines.=--These have none of the characteristics of the preceding bases; their type is neurine, a highly toxic base found in the brain, nerves, and certain fish ova. These bases are sometimes normally produced by the animal economy, and are also frequently the result of microbic action. They are the result of the simple phenomena of fermentative hydrolyzation of protagons and lecithins. Among these bases are _choline_, a weak alkaloid, and _betaine_, which appears to be non-toxic. The former has the formula C{5}H{15}NO{2}; it was discovered by Stocker. Wurtz synthesized it by combining trimethylamine and glycol-monochlorhydrine, and treating the resulting hydrochloride with silver oxide. Betaine, C{5}H{11}NO{2}, is found in beets; it was discovered by Scheibler. Neurine is, chemically, trimethylvinylammonium hydrate.