A Mechanical Account of Poisons in Several Essays

by Richard Mead

For Vipers live chiefly upon Lizzards, Frogs, Toads, Mice, Moles, and the like Animals, which they do not chew, but swallow down whole, and they lie in the Stomach; or if that be not big enough to receive them, partly in that, and partly in the Œsophagus, which is membranous and capable of great Distension, till by the Salival Juices of those Parts, together with the Help of the Fibres of the Stomach, and the Contraction of the Muscles of the Abdomen, they are gradually dissolved into a Fluid Substance, fit for the Nourishment of their Bodies, which is the Work of many Days; this is one Reason why these Creatures can live so long without taking any fresh Food, which I have known them to do Three or Four Months; as another is, that their Blood is a grosser and more viscid Fluid than that of most other Animals; so that there is but a very little expence of it by Transpiration, and consequently less need of Recruit; this not only Microscopes discover, but Reason teaches; because there is but very little Muscular Force in the Stomach to comminute the Food, and make a Chyle of fine Parts, and therefore the Blood must accordingly be of a Tough and Clammy Consistence. Besides, the Heart of a Viper has properly but one Ventricle, and the Circulation of the Blood is performed after the same Manner as it is in a Frog and Tortoise, in which not above one Third of it passes thro’ the Lungs; upon which Account its Comminution in them by the Air is proportionably lesser than in other Animals. Now such a manner of Feeding as this does necessarily require, that the Prey should upon the first Catching be immediately kill’d, otherwise it were by no means fit to be let into the Stomach; for we are not to think that the Force of this Part would be alone sufficient to destroy it, the Subtilty of a living Creature (besides the Consideration of the Weakness of the Fibres) being in a great Measure able to elude that, as indeed we do every Day find live Animals in the Ventricles of others; and therefore to do this is the proper Use both of the Teeth and their Poison; for which being designed and adapted, it is no wonder if the Viper, this same Way by which it destroys its Prey, proves sometimes mischievous to any other Creatures besides, when it happens to be enraged, or by any Provocation stirr’d up to bite.

The Description of the Poisonous Fangs, their Make, Articulation and Motion, as also of the Glands that separate the Yellowish Liquor, and the Bags that contain it; I shall give, together with some Anatomical Observations, at the End of this Discourse.

This Venomous Juice it self is of so inconsiderable a quantity, that it is no more than one good Drop that does the Execution; and for this reason Authors have contented themselves with Trials of the Bite upon several Animals, never Essaying to examine the Texture and Make of the Liquor it self; for which purpose I have oftentimes by holding a Viper advantageously, and inraging it till it struck out its Teeth, made it to bite upon somewhat solid, so as to void its Poison; which carefully putting upon a Glass Plate, I have with a Microscope, as nicely as I could, viewed its Parts and Composition.

Upon the first Sight I could discover nothing but a Parcel of small Salts nimbly floating in the Liquor, but in a very short time the Appearance was changed, and these saline Particles were now shot out as it were into Crystals of an incredible Tenuity and Sharpness, with something like Knots here and there, from which they seemed to proceed, so that the whole Texture did in a manner represent a Spider’s Webb, tho’ infinitely Finer, and more Minute; and yet withal so rigid were these pellucid Spicula, or Darts, that they remained unaltered upon my Glass for several Months [(13)].

I have made several Trials with this Juice in order to find out under what Tribe of Salts these Crystals are to be ranged; and not without some difficulty, by reason of the Minute Quantity of the Liquor, and the Hazard of Experiments of this Nature, have plainly seen that it does, as an Acid, turn the blue Tincture of Heliotropium to a Red Colour.

I did not succeed so well in mixing it with Syrup of Violets, and yet it did really seem to induce in this a Reddish Hue; but I am very certain it did not at all change it to a Greenish Colour, as it would have done if any ways Alcalious.

This may suffice in their own way of arguing, to convince those Gentlemen, who without the Assistance of any Experiments, meerly to serve an Hypothesis which they have too fondly taken up, have with great Assurance told the World, that the Viperine Venom is an Alcali, and consequently to be cured by Acid Remedies. But it is by far more easie to Spin out a false Notion into precarious Reasonings, than to make faithful Experiments, and fairly improve ’em by just and necessary Consequences.

To proceed, this Discovery agrees very well with a Relation communicated by an Ingenious Person to Dr. Tyson, which does so much illustrate this Matter, that I shall transcribe it in his own Words, out of the before cited Philosophical Transactions; he says then, That being in the Indies, there came to him an Indian with several Sorts of Serpents, offering to shew him some Experiments about the Force of their Poison; having therefore first pulled out a large One, the Indian told him this would do no Harm; and making a Ligature on his Arm as in letting Blood, he exposed it naked to the Serpent, being first irritated to make him bite it; the Blood that came out of the Wound made by his Teeth, he gathered with his Finger, and laid it on his Thigh, till he had got near a Spoonful, after this he takes out another called Cobra de Capelo, which was lesser, and inlarges much upon the Greatness of his Poison; to shew an Instance of it, grasping it out about the Neck, he expresses some of the Liquor in the Bags of the Gums, about the Quantity of half a Grain, and this he puts to the coagulated Bleed on his Thigh, which immediately put it into a great Fermentation, and working like Barme, changed it into a Yellowish Liquor.

This I say does well enough accord with what we have been advancing concerning the Nature of this Juice, for Mr. Boyle has long since proved by Experiments, that there is nothing of Acid in human Blood; and Dr. Pitcarn [(14)] has demonstrated, that the Acid Substances of Vegetables taken into the Stomach, are by the Action of this Part, the Lungs and Heart, when they come into the Blood-Vessels, turn’d to Alcalious; so that the Arterial Fluid must necessarily be considered as an Alcali; and therefore according to the known Principles of Chymistry, its mixture with such a Liquor as we have discovered the Viperine Sanies to be, will always exhibit some such appearance as this now related.

But not to engage any farther in these sort of Controversies, we may perhaps from the foregoing Observations receive some Light in order to understand the Nature and Reason of all those Symptoms which attend the Bite of this Creature. For the pungent Salts of this Venom, when with Force thrown into the Wound, will not only as so many Stimuli, irritate and fret the sensile Membranes, whereupon there necessarily follows a greater Afflux than ordinary of the Animal Juices that way, (as is manifest from the Bellinian Doctrine, De Stimulis) so that the wounded Part must be Swelled, Inflamed, Livid, &c. but also these Spicula being mixt with the Blood, will so disjoin and disunite the Parts of it, that its Mixture must be quite alter’d; and from the various Cohæsion of its Globules will arise such different Degrees of Fluidity and Impulse towards the Parts, &c. from what this Liquor had before, that its very Nature will be changed, or in the common way of speaking, it will be truly and really Fermented.