52 DISEASES OF CATTLE. 



THE ACTION OF POISONS. 



The action of poisons may l:>e 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 gener- 

 ally either destroy by corrosion the tissues with which they come in 

 contact or Ijy inhalation set up acute inflammation. When any cor- 

 rosive agent is taken into the stomach in poisonous c|uantities, a group 

 of symptoms is developed which is common to all. The tissues with 

 which the agent comes in contact are destroyed, sloughing and ai;iite 

 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 suffi- 

 ciently corrosive nature to destroy the tissues. I)ut sufficiently irritat- 

 ing 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 invobed. 

 The poisonous eff'ect of any substance is modified by the quantity 

 used ; Ijy its chemical combinations ; l)y the part of the animal struc- 

 ture with which it comes in contact ; by the ph^'sical 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 youno- one. 

 The rapidity with which the poison is absorbed, owing to the part of 

 the hodj with which it is brought in contact, is also an important 

 factor. Ro marked is this quality that some agents which have the 

 power of desti'oying life with almost aljsolute certainty when intro- 

 duced lieneath the skin, may be taken into the stomach without caus- 

 ing 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 brouglit in contact with dialyzed iron it forms an insoluble 

 compound and becomes innocuous. Idios_vncrasies are not so notice- 

 able in cattle practice as in practice among human beincs, but the 

 uncertainly with which some drugs exert their influence would lead 

 us to believe that well-marked differences in susceptibilitv exist. 

 Even in some cases a tolerance for poison is engendered, so that in a 



