All snakes have a double row of teeth, which are more used to aid the snake in swallowing food than as weapons of offence ; but all vipers have a pair of fang-like teeth, which take the place of what are termed the palatine teeth.
In vipers these teeth are movable, lying back when the snake is not aroused, but raised erect when the reptile is in action. In biting, the snake makes a quick dart, rarely moving over one-third to one-half of its length, and sinks its fangs, perhaps its teeth as well, into the object aimed at. The imprint has been described as typical of the snake-biting, as the accom panying cut (Fig. 389), re produced from Langmann's article in Wood's Reference Handbook of the Medical Sciences, shows ; but this is largely accidental. In the vipers there is a channel in the fang, which leads up to a poison pocket ; and, as the snake bites, the contractions of the muscles of the jaw force the poison into the wound. This poison is a very interesting substance. Unlike the other secretions, which are alkaline, it is strongly acid, and in each species of snake it has a characteristic odour. Thus, Langmann speaks of the odour of the rattlesnake-venom as " mousy." It is a pale straw-coloured or dark orange liquid, with a high percentage of solids. On drying, the snake-venom forms a light, brownish, translucent scale. The venom is sterile when fresh. Chemically, snake-venom is a very complex substance. It is very stable, for dried venom has been kept for twenty to twenty-five years without losing any of its poisonous properties. The poison of venomous serpents kept in alcohol for years still remains active. It is thought to be a mixture of peptone and globulin-like substances, although certain facts are known which render it possible that the poisonous principle is not a proteid at all.
The effect of the bite of a venomous snake varies considerably in different individuals bitten, largely because of the variations in the amount of poison injected. The poison is capable of very rapid absorption when injected, first entering the connective tissues and thence passing into the blood. The poison of the viper does not seem to pass rapidly through mucous membranes. This fact renders it comparatively safe to try to suck viper-poison from a bite after a free incision has been made. The symptoms of poisoning also differ according to the snake that does the biting. After a cobra-bite, which shows two small dots of puncture of the fangs, from which a burning pain spreads out, the patient in about an hour commences to feel a distinct sensation of giddiness and vertigo. Then weakness develops, the gait becomes staggering, and finally the patient is unable to stand up from paralysis of the legs. Other muscles are also involved. The eyelids droop, the jaw falls, swallowing becomes difficult. There is nausea and vomiting, and slowed respirations leading up to cessation of breath ing, the heart continuing to beat some time after respiration has ceased.
Convulsive movements may occur. In a large number of instances death takes place in a few hours, but may be delayed for fifteen or eighteen hours. In non-fatal cases recovery is apt to be rapid, and there are few after effects.
The results of a rattlesnake-bite arc very different. There is an initial pain, with swelling and burning, but an additional bloody discoloration at the site of the wound. The symptoms develop in about fifteen to twenty minutes, discolorations appearing in the skin and mucous membranes both before and after the onset of the constitutional effects. There is a sense of great prostration, with nausea, vomiting, and a very marked increase in the rapidity of the breathing. The blood-pressure falls, the pulse becoming very soft, and the breathing then becomes slow and snoring. Symptoms of irritations, such as convulsions, may occur, especially if the dose has been large ; this is followed by muscular weakness, develop ing into complete paraly sis, as with cobra-poison.
Death usually takes place within twelve hours, and signs of multiple hxmor rhages in the tissues of the body are numerous. Albumin and blood appear in the urine. Recovery may be rapid, but is frequently complicated by abscess-formation in the hxmorrhagic areas.
The poison of the rattlesnake acts both upon the blood and on the nervous tissues, leading to destruction of both classes of cells. " Neurolvtic " and " hxmolvtic " are the descriptive terms used in modern toxicology to signify this type of poisoning. Langmann, in summarising the effects of snakebite.
says that the cause of death, " if taking place within a few hours, is thrombosis (coagulation of the blood in the blood-vessels) ; a patient who dies within twenty-four hours may succumb in the first few hours to respiratory paralysis, later to general paralysis ; death occurring after a considerable lapse of time, days or weeks after a bite, may be the result of sepsis or of general prostration following prolonged suppuration." The treatment must be prompt. The member bitten must be cut off from the general circulation as rapidly as possible, a tight band, preferably a rubber hand, being immediately placed about the arm or leg above the point of a bite. The underwear may be torn to provide a band. Sucking is not of much value unless the wound has been laid bare with a knife. Some physicians advise cutting out a large piece of tissue, and thus limiting the amount that can be absorbed. As to the use of alcohol, it is highly improbable that it is of much value ; large amounts are certainly more prejudicial than helpful. Its chief use seems to be in deadening the sense of alarm and despair of the bitten person. Strychnine has been used, but has not been definitely demonstrated to be a specific. In recent years anti venom serums have been used in experimental work to advantage.