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.
The granule of venogen is distinguished from the granule of elaborated venom by its affinity for Unna’s blue, safranin, and fuchsin. The granule of venom has an affinity for eosin; it is never excreted in granular form, but after intracellular dissolution.
Venogen is never met with in the lumen of the gland-tube.[6]
Collection of Venom.
Venom can be extracted from the poison-glands of either freshly killed or living snakes.
In cases in which the venom of dead snakes has to be collected, the best method of extraction consists in fixing the head of the animal to a sheet of cork and carefully dissecting out the gland on each side. The reptile being placed on its back, the lower jaw is removed with a pair of scissors; two strong pins or two tacks are thrust through the skull, in the median line, in order to keep the head from moving. The poison-fangs are next drawn out of their sheaths, and, without injuring them, the two poison-ducts, which open at their bases, are isolated and tied with a thread in order to prevent the poison from running out.
The dissection of the glands is then very easy; they are lifted out and placed in a saucer. The end of the duct is cut between the gland and the ligature, and with a pair of fenestrated or polypus forceps the whole of the glandular mass is gently squeezed from behind forwards, the liquid which flows out being received in a large watch-glass.