The heloderma is classed as follows: Order: Saurii. Lacertilia. Lizards. Sub order: 5. Fissilinguia. Family: Lacratidæ. Heloderma horridum of Mexico; the crust lizard; the Mexican Caltetopen. Called heloderma from its skin being studded with nail or tubercle-like heads. The Gila monster is a native of Arizona, New Mexico and Texas. It is smaller than the Mexican variety, and is called, by Cope, Heloderma Suspectum. It is the only lizard whose character is not above reproach, hence the name. Zoology says: An esquamate-tongued lizard with clavicles not dilated proximally, a postorbital arch, no postfront-osquamosal arch, the pre and post frontals in contact, separating the frontal from the orbit, and furrowed teeth receiving the different ducts of highly developed salivary glands.
(There has been considerable difference of opinion as to whether the Heloderma is poisonous or not; but the following abstract from a paper on the subject read before the College of Physicians, Philadelphia, 1883, by S. Wier Mitchell, together with the provings made later, ought to very effectually settle all dispute on this point; the conclusions are the result of experiments on animals):
The poison of heloderma causes no local injury. It arrests the heart in diastole, the organ afterwards contracts slowly—possibly in rapid rigor mortis.
The cardiac muscle loses its irritability to stimuli at the time it ceases to beat. The other muscles and nerves respond to irritants.
The spinal cord has its power annihilated abruptly, and refuses to respond to the most powerful electrical currents.
This virulent heart poison contrasts strongly with serpent venom, since they give rise to local hæmorrhages, causing death chiefly through failure of respiration and not by the heart unless given in overwhelming doses. They lower muscle and nerve reactions, especially those of the respiratory apparatus, but do not cause extreme and abrupt loss of spinal power. They also produce secondary pathological appearances absent in heloderma poisoning.
The briefest examination of the lizard's anatomy makes it clear why it has been with reason suspected to be poisonous, and why it poisons with so much difficulty. Unless the teeth are entire, the poison abundant, and the teeth buried in the bitten flesh so as to force it down into contact with the ducts where they open at the crown of the teeth, it is hard to see how even a drop of poison could be forced into the wounds. Yet it is certain that small animals may die from the bite, and this may be due to the extraordinary activity of the poison, and to the lizard's habit of holding tenaciously to what it bites, so as to allow time for a certain amount of absorption.
(The provings and the clinical cases that follow were from the virus of the Gila monster obtained by Dr. Charles D. Belden, of Phœnix, Arizona, in 1890, who suggested it as a possible remedy for paralysis agitans and locomotor ataxia. He obtained the virus from a captive monster by irritating it and then letting it strike, or bite, a piece of heavy glass; by this means he obtained a few drops of a pasty yellowish fluid. In his letters Dr. Belden quotes Sir John Lubbock as follows):
This animal does not bite frequently, but when it does it is understood that the result is a benumbing paralysis like to paralysis agitans or to locomotor attaxia. There is no tetanic phase, being, as I apprehend, a condition almost reverse in objective symptoms to hydrocyanic acid or strychnia.
(Dr. Belden also writes):