Two large _Cerastes_ vipers, from Egypt, yielded me, one 0·123 gramme, the other 0·085 gramme of liquid venom, which, after desiccation, left respectively 0·027 gramme and 0·019 gramme of dry residue. Under the same conditions, a magnificent _Crotalus confluentus_ (Mottled Rattle-Snake), for which I was indebted to the kindness of Mr. Retlie, of New York, yielded, two months after reaching my laboratory, 0·370 gramme of liquid venom and 0·105 gramme of dry extract in _a single bite_. The total quantity of liquid venom that I found contained in the two glands of the same reptile, when extirpated after death, and after the snake had been in the laboratory for five months, amounted to 1·136 gramme, which gave 0·480 gramme of dry extract. We see, therefore, that the proportion of dry residue, including albumin, salts, the _débris_ of leucocytes, and the toxic substance, oscillates between 20 and 38 per cent. Its strength varies with the length of time that has elapsed since the snake’s last bite or last meal. * * * * * From the _histological standpoint_, the process of the secretion of venom, in the cells of the glands, may be divided into two stages:-- (_a_) A stage of nuclear elaboration. (_b_) A stage of cytoplasmic elaboration. These two stages are superposed and successive. In addition to the passive exchanges between the nucleus and the cytoplasm, the nuclear mass actively participates in the secretion. This participation is rendered evident:-- (1) By the difference of chromaticity in the granules of chromatin. (2) By the emission of formed granules into the cytoplasm, granules which are spherical and of equal bulk, with the chromatic reactions of differentiated intranuclear chromatin. (3) By the exosmosis of the dissolved nuclear substance, accessorily formed in an ergastoplasmic shape. These formations constitute, on the one hand, the granules of _venogen_; on the other, the ergastoplasmic venogen. In the poison-cell of _Vipera aspis_, and in the serous cell of the parotid glands of _Tropidonotus natrix_ (Grass Snake) the venogen is elaborated chiefly in granular form. On entering the perinuclear cytoplasm, the granule of venogen and the ergastoplasmic venogen may either disappear immediately, as happens in periods of cellular stimulation, or else continue to exist for some time within the cell, indicating a period of saturation by the elaborated material. During cytoplasmic activity the granule of venogen and the ergastoplasmic venogen disappear. Nuclear elaboration and cytoplasmic elaboration constitute two different cycles of secretion. The effect of the nuclear cycle is to furnish the cytoplasm with the elements necessary for the work of secretion properly so-called. Cytoplasmic elaboration is not confined to the basal protoplasm, but takes place throughout the entire cell: it is especially active in the perinuclear cytoplasm.