In animals, the principal phenomena observed by Selmi to follow the injection of the substances are the following: At first dilatation of the pupil, then constriction; tetanic convulsions, soon followed by muscular relaxation, and retardation, rarely acceleration, of heart-beat; absolute loss of cutaneous sensibility; loss of muscular contractility; paralysis of the vasomotors; greatly retarded respiration; stupor, followed by death with the heart in systole. It must be observed that in a number of cases where toxic researches had been made in the past, these bases had been mistaken for poisons which were believed to have been introduced into the organism with criminal intent. No one will ever know how many have fallen victims in the past to ignorance regarding the cellular mechanism! The extraction of these bases is a tedious and difficult operation. The materials must first be exhausted with water slightly acidulated; then, after precipitating the albuminoids by boiling and defecating by adding lead acetate, the liquid is evaporated to one-half its volume and dialyzed in a vacuum.[7] [7] ARMAND GAUTIER: _C. rend. de l'Académie des Sciences_, CXIV, p. 1256. _Ibid._, XCVII, p. 264, and XCIV, p. 1600. Phosphomolybdate is then added to the dialyzed liquid, and the precipitate formed, which now contains all the bases, decomposed by boiling with lead acetate. After removing the excess of lead, there is thus obtained a limpid solution of all the alkaloidal bases in the form of acetates. These are separated by alcohol and by means of fractional precipitations with various metallic salts, depending upon the known properties of the bases. In order to facilitate their study, the ptomaines have been grouped under two distinct classes, the one embracing the cadaveric or putrefactive ptomaines, of undetermined microbial origin, the other containing the ptomaines formed by microbes of known character. Each of these two groups is itself divided into subgroups, as shown in the following table: GROUP I. =CADAVERIC PTOMAINES OF UNDETERMINED MICROBIAL ORIGIN.= _a._ Amines. _b._ Guanidines. _c._ Oxamines (fatty or aromatic). _d._ Amido Acids. _e._ Carbopyridic Acids and analogues. _f._ Undetermined Ptomaines. GROUP II. =PTOMAINES OF KNOWN MICROBIAL ORIGIN.= _a._ Ptomaines extracted from microbial cells. _b._ Ptomaines from pathological urines. We will not here enter upon a detailed study of the bases belonging to each of these groups. This subject is a vast one, requiring for its treatment a volume devoted to it alone. We will here simply touch upon the principal properties of several of the bases of each of the subgroups named. BASES OF GROUP I. _a._ =Amines.=--Among these we find nearly all the fatty amines, such as the methylamines and the cyclic alkaloids such as pyridine. They are formed particularly by the putrefaction of fish.