242 STOCK-POISONING PLANTS AND THEIR CONTROL 



caused by the grazing of these dangerous plants if they will 

 familiarize themselves with the more common poisonous species, 

 avoid grazing the stock upon heavily infested areas, check over- 

 grazing, provide sufficient salt, and, at the same time, put into 

 practice certain other improved methods of handling. 



The following chapters aim, first, to point out the conditions 

 under which serious poisoning is liable to occur; second, to ex- 

 plain practical, thoroughly tested methods for preventing losses; 

 third, to picture and describe the species which cause the heaviest 

 losses; and, fourth, to note the preventive and remedial measures 

 for each, in so far as they are known. 



What is Poison? — By poison is here meant any substance, 

 which, when taken internally, acts in a noxious manner other 

 than mechanical, either causing death or interfering more or less 

 seriously with health. The toxic substances found in the differ- 

 ent poisonous plants vary widely both in their poisonous effect 

 upon the animal and in their chemical and physical properties. 



The subject of poisonous plants is by no means new. The 

 word " toxicology " is derived from the Greek word toxikon, 

 which referred to the poison in which arrows were dipped. The 

 American Indian and various uncivilized races of Africa and 

 other parts of the world were familiar with numerous poisonous 

 plants long before chemistry had advanced far enough to isolate 

 and identify poisonous plant substances. Numerous interesting 

 illustrated treatises of poisonous plants, prepared by ancient 

 Greek and Latin botanists or " medicine " men, show that many 

 descriptions of the properties of plants given by the ea'-ly workers 

 have more recently been substantiated by scientific investiga- 

 tions. 



Important Families of Poisonous Plants. — Of the many 

 species of poisonous plants occurring throughout the United 

 States, those contained in six genera are probably responsible 

 for at least 75 per cent of all livestock poisoning. These genera 

 are members of four families. 



To the bunchfiower family {Mela^ithaceae) belong the well- 

 known species of death camas (Zygadenus). The plants of this 

 genus are found largely in the western part of America. 



