384 DISEASES OF CATTLE, SHEEP, GOATS, ETC. 



much or too little.) The following is perhaps as satisfactory a 

 definition as may be given: A poison is a chemical substance hav- 

 ing an inherent deleterious property rendering it capable in small 

 quantities of producing serious functional disturbances upon gaining 

 access to the system by the usual channels; or it is a substance which, 

 when introduced into the system or applied externally, injures health 

 or destroys life irrespective of mechanical means or thermal changes. 

 The common conception of a poison is any substance which, in 

 small quantity, wall destroy life, excepting 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 glycerine. Living organisms are not chemi- 

 cal 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, dis- 

 infecting, poisoning vermin, dipping sheep, painting, smelting, dye- 

 ing, 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, or food that is infested 

 with insects, may have become poisonous, producing forage pois- 

 oning, 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 OP POISONS. 



This may be either local, and exerted directly on the tissues 

 with which they come in contact, or remote, acting through the cir- 

 culation 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 con- 

 tact or by inhalation set up acute inflammation. When any cor- 

 rosive agent is taken into the stomach in poisonous quantities, a 

 group of symptoms is developed which is common to all. The tis- 

 sues 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 



