Part 14

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POISONS AND POISONING.

By V. T. ATKINSON, V. S.

DEFINITION OF A POISON.

To define clearly the meaning of the word "poison" is somewhat difficult. Even in law the word has never been defined, and when a definition is attempted we are apt to include either too much or too little. The following definition given by Husemann is perhaps the best: "Poisons are those substances, inorganic or organic, existing in the organism or introduced from the outside, produced artificially or formed as natural products, which, through their chemical nature, under definite conditions, so affect some organ of a living organism that the health or well-being of the organism is temporarily or chronically injured." The common conception of a poison is any substance which, in small quantity, will destroy life, except such as act by purely mechanical means, as, for example, powdered glass.

Some substances that are not usually looked upon as poisons may destroy life if given in large doses, such as common salt. Other substances which are perfectly harmless when taken into the body in the usual way are poisons if injected into the circulation, such as distilled water, milk, or glycerin. Living organisms are not "chemical substances," and are not considered in this connection.

SOURCES OF POISONING.

Poisoning may come from many causes, among the chief of which are the following:

(1) Errors in medication.--By using the wrong substance or too large dose an animal may be poisoned.

(2) The exposure of poisons used for horticultural, technical, or other legitimate purposes.--Poisons used for spraying plants, disinfecting, poisoning vermin, dipping cattle or sheep, painting, smelting, dyeing, or other purposes may be so handled as to come within the reach of animals.

(3) Damaged food.--Food that has undergone putrefaction or certain kinds of fermentation or heating, may have become poisonous, producing forage poisoning, meat poisoning, cheese poisoning, etc.

(4) Poisonous plants in the pasture or forage.

(5) The bite or sting of a poisonous insect or the bite of an animal.

(6) Malicious poisoning.

THE ACTION OF POISONS.

The action of poisons may be either local, and exerted directly on the tissues with which they come in contact, or remote, acting through the circulation or the nervous system; or both local and remote action may be exerted by the same drug. Poisons which act locally generally either destroy by corrosion the tissues with which they come in contact or by inhalation set up acute inflammation. When any corrosive agent is taken into the stomach in poisonous quantities, a group of symptoms is developed which is common to all. The tissues with which the agent comes in contact are destroyed, sloughing and acute inflammation of the surrounding structures take place; intense pain in the abdomen and death ensue. In a like manner, but with less rapidity, the same result is reached if the agent used be not of a sufficiently corrosive nature to destroy the tissues, but sufficiently irritating to set up acute inflammation of the mucous membrane of the digestive tract. If the poison exerts a remote influence alone, the action is quite different, little or no local effect being produced upon the digestive organs.

To produce an effect on some part of the body distant from the channel of entrance, a poison must have been absorbed and carried in the blood to the central nervous system or other region involved. The poisonous effect of any substance is modified by the quantity used; by its chemical combinations; by the part of the animal structure with which it comes in contact; by the physical condition of the subject; and also by the rapidity with which the poison is excreted. As an illustration, opium may be given with safety in much larger doses to an animal suffering from acute pain than to one free from pain, and to an adult animal with greater safety than to a young one. The rapidity with which the poison is absorbed, owing to the part of the body with which it is brought in contact, is also an important factor. So marked is this quality that some agents which have the power of destroying life with almost absolute certainty when introduced beneath the skin, may be taken into the stomach without causing inconvenience, as curara, the arrow poisons, or the venomous secretion of snakes. Other agents in chemical combination may tend to intensify, lessen, or wholly neutralize the poisonous effect. For example, arsenic in itself has well-marked poisonous properties, but when brought in contact with dialyzed iron it forms an insoluble compound and becomes innocuous. Idiosyncrasies are not so noticeable in cattle practice as in practice among human beings, but the uncertainty with which some drugs exert their influence would lead us to believe that well-marked differences in susceptibility exist. Even in some cases a tolerance for poison is engendered, so that in a herd of animals equally exposed injurious or fatal effects do not appear with uniformity. For example, among cattle that are compelled to drink water holding in solution a salt of lead the effects of the poisoning will be found varying all the way from fatality to imperceptibility.

GENERAL SYMPTOMS OF POISONING.

It is not always easy to differentiate between poisoning and some disease. Indeed, examination during the life of the animal is sometimes wholly inadequate to the formation of an opinion as to whether the case is one of poisoning or, if it is, as to what the poison may be. A chemical and physical examination after the death of the animal may be necessary to clear up the doubt. On the other hand, the symptoms may be of such a nature as to point unmistakably to poisoning with a certain agent. In general, the following classes of symptoms may be regarded as indicative of poisoning: Sudden onset of the disease without visible cause, a number of animals being similarly affected at once, with severe gastrointestinal disorder or derangement of the nervous system, or both; sudden alteration of heart action in relation to frequency, force, or rhythm; local irritation, dyspnea, or change in the urine or urination.

After death, lesions of the greatest variety may be found, and it is necessary for one to be skilled in anatomy and pathology in order to determine their significance. Oftentimes the stomach and intestines are red, have thick walls, and contain blood. This signifies a severe irritant, such as arsenic or corrosive sublimate. Other alterations sometimes found are inflammation of the kidneys or bladder, points of hemorrhage in various organs, changes in the blood, congestion of the lungs, and certain microscopic changes.

GENERAL TREATMENT.

The treatment of animals suffering from poison must vary according to the nature of the toxic agent. There are a few general plans of action, however, which should be followed so far as possible. In man and in some of the smaller animals it is possible to eliminate unabsorbed poison by the use of the stomach pump or by causing vomiting. These proceedings are impracticable in cattle. It is well, therefore, in many cases to endeavor to expel the unabsorbed poison by emptying the digestive tract, so far as may be, with a nonirritating purge. Castor oil in doses of 1 pint to 2 quarts is adapted to this purpose. If the poison is known to be nonirritant--as a narcotic plant--from 10 to 20 drops of croton oil may be given with a quart of castor oil. When poisons are somewhat prolonged in their effect, Epsom salt in doses of 1 pound can be given advantageously. To protect the mucous membrane from the action of strong irritants, one may give flaxseed tea, barley water, the whites of eggs, milk, butter, olive oil, or fresh lard. Chemical antidotes may sometimes be used for special poisons, as advised below. In general, if an acid has been taken it may be neutralized with an alkali, such as chalk, magnesia, bicarbonate of soda (baking soda), ammonia (diluted), or soap. If the poison is an alkali, such as caustic soda or potash (lye), or ammonia, an acid, such as diluted (1 per cent) sulphuric acid or vinegar, may be administered. Special treatments and antidotes are considered below.

A poisonous agent may be so gradually introduced into the system as to slowly develop the power of resistance against its own action. In other cases where the poison is introduced slowly the poisonous action becomes accumulative, and, although there is no increase in the quantity taken, violent symptoms are suddenly developed, as if the whole amount, the consumption of which may have extended over a considerable period, had been given in one dose. Other agents, poisonous in their nature, tend to deteriorate some of the important organs, and, interfering with their natural functions, are productive of conditions of ill health which, although not necessarily fatal, are important. Such might properly be called chronic poisons. Poisons of themselves dangerous when administered in large doses are used medicinally for curative purposes, and a very large percentage of the pharmaceutical preparations used in the practice of medicine if given in excessive quantities may produce serious results. In the administration of medicines, therefore, care should be exercised not only that the animal is not poisoned by the administration of an excessive dose but that injury is not done by continued treatment with medicines the administration of which is not called for.

MINERAL POISONS.

ARSENIC POISONING.

Of the common irritant and corrosive poisons, arsenic, especially one of its compounds (Paris green), is likely to be the most dangerous to our class of patients. The common practice of using Paris green and other compounds of arsenic as insecticides for the destruction of potato beetle and other insect enemies of the farmer and fruit grower has had the effect of introducing it into almost all farming establishments. White arsenic is also a principal ingredient in some popular dipping preparations, and poisoning from this source occasionally takes place when, after dipping, animals are allowed to run in a yard in which there is loose fodder. The drippings from the animals falling on the fodder render it poisonous and dangerous to animal life if eaten. Familiarity with its use has in many instances tended to breed contempt for its potency as a poison. Rat poisons often contain arsenic. The excessive use of arsenic as a tonic, or of "condition powders" containing arsenic, has been the means of poisoning many animals. This is the common poison used by malicious persons with criminal intent. The poison may also be absorbed through wounds or through the skin if used as a dip or bath.

If a large dose is given, at once acute poisoning is produced; if repeated small doses are given, chronic poisoning may result. The poisonous dose for an ox is from 3 drams to 1 ounce.

Symptoms.--The symptoms of acute poisoning first appear as those of colic; the animal is restless, stamping with the feet, lying down and getting up. There is tenderness on pressure over the abdomen. The acute symptoms increase; in a few hours violent diarrhea is developed; in many cases blood and shreds of detached mucous membrane are mixed with the evacuations. There is irregular and feeble pulse and respiration, and death is likely to supervene between the eighteenth hour and the third day. If the latter period is passed, there is a reasonable hope of recovery.