Live Stock. 



426 



[May, 1912. 



above, all belong to one plant-family, 

 the Solanaceee. On this account we are 

 able to treat some plant families as more 

 dangerous than others ; thus the Ranun- 

 eulacese are often acrid and poisonous ; 

 the Papaveraceee, the tribe Cichoriacese 

 of the Compositae, and the Solanaceee 

 are apt to be narcotic ; the family Loga- 

 niacesB produces some of the most 

 dangerous vegetable drugs known to us. 

 On the other hand, some large families 

 of plants contain no species known to be 

 poisonous, e,g,, the Cruciferse, etc. 



Not all kinds of animals equally 

 affected. — Some kinds of animals are 

 poisoned by plants which are harmless 

 to other kinds, e.g., Darnel seed is said 

 to be poisonous to man, dogs, horses, 

 and sheep, but to be wholly innocuous 

 to cows, pigs, and ducks (Wood, Re- 

 mington, and Sadtler). The well- 

 known poison ivy, Rhus toxicodenron, 

 of the Atlantic Coast of North America, 

 and the Poison-oak, Rhus diversiloba, 

 of the Pacific Coast, are very poisonous 

 to man, but are greedily eaten in quan- 

 tity by horses with no ill-effect. Morris 

 (1896) states that Leucazna glauca is 

 greedily eaten by cattle, sheep, and 

 goats without ill-effect, though very 

 injurious to horses, mules, donkeys, and 

 pigs. Dr. Watkins Pitchford suggests 

 that probably all plants which are 

 poisonous to animals are also poisonous 

 to man. 



Not all Individuals equally Suscep- 

 tible. — Nor are all individuals of the 

 same animal species equally susceptible 

 to certain poisons. In California some 

 people are immune against poisoning by 

 Rhus diversiloba ; most persons are only 

 slightly inconvenienced, some are made 

 seriously ill, and a few have been killed 

 by it. Chestnut (1898) reports that Rhus 

 toxicodendron, of the Eastern United 

 States, acts in the same way, and he 

 further states that this variability is 

 not confined to poisons acting exter- 

 nally. 



Susceptibility may be increased by Ill- 

 health or Poverty of Condition.— The con- 

 dition, age. or state of health of the 

 animal sometimes has an influence on 



its susceptibility to certain poison, or 

 to the quantity which may be consumed 

 without serious effect. Wilcox (1901) 

 reports that sapotoxin, a poisonous 

 substance found in many plants, is far 

 more injurious when the alimentry tract 

 is ulcerated than when it is healthy. 



Acquired Craving.— In the case of some 

 poisonous plants animals which taste 

 them develop a morbid craving which, 

 when once acquired, can scarcely be 

 overcome. This is true of Astragalus 

 Hornii and other " Loco-weeds " of the 

 Western United States. Maiden (1911) 

 reports a similar result from eating the 

 Australian "Indigo Plant," Swainsona 

 galegifolia. Chestnut (1898) finds that in 

 the Southern United States stock usually 

 avoid Helenium autumnale, but some- 

 times develop a taste for the plant and 

 are killed quickly by eating it in large 

 quantity. The seeds of the common 

 Boer pumpkin of South Africa, if eaten 

 freely by poultry or ostriches, are said 

 to make the birds " crazy " and to pro- 

 duce temporary paralysis ; it is also 

 said that "once they acquire the bad 

 habit of eating the pips it is difficult to 

 break them of it." This craving may 

 be developed to such an extent that 

 animals ignore their proper food, and, 

 instead of grazing quietly, spend their 

 time hunting over the camps in search 

 of individuals of the particular plant 

 they have learned to like, even digging 

 up the roots to satisfy their craving, 

 with the result that they become ema- 

 ciated from lack of sufficient food. This 

 taste is an acquired one, and does not 

 necessarily affect all the animals in a 

 herd or flock. Certain animals on one 

 side of a fence may acquire it, while 

 those on the other side may not. It is 

 well known that animals have their 

 particular friendships, and that some of 

 them generally graze together, especially 

 if they belong to the same family. If 

 one member of such grazing group 

 acquires the taste for a certain poisonous 

 plant, it is likely that the other members 

 will learn to eat it also. 



These facts must explain the " spread" 

 of a disease caused by poisoning to 

 farms which were hitherto supposed to 



