4 Introduction [ch. 



foreign origin are occasionally sold for food purposes owing to the 

 mistaken idea that they are a valuable addition to the ration {e.g. the 

 poisonous "Java" beans). In any case in which an animal is believed 

 to have been poisoned purchased feeding stuffs should always be con- 

 sidered as a possible source of injury and be submitted to examination. 



Clippings and trimmings from gardens and shrubberies have proved 

 a more or less common cause of hve stock poisoning, such material 

 being too often carelessly thrown out for animals to pick over. In 

 such circumstances it may quite easily happen that the animals get 

 yew, daphne, privet, rhododendron, azalea, solanums, and other 

 plants of a poisonous character. For this reason it is better to destroy 

 such trimmings, etc., by burning them, or by adding them to the com- 

 post heap as the case may be. 



A further source of poisoning must be noted here— ^fleshy and para- 

 sitic fungi (toadstools, rust fungi), moulds and similar organisms. 

 Many toadstools are directly poisonous when eaten, but the microscopic 

 organisms are probably in themselves harmless, though taken with food 

 which they are responsible for injuring (bad hay, cakes, etc.), the 

 poisoning being due to the changed and damaged feeding stufPs, or 

 possibly to poisonous principles directly elaborated by the micro- 

 scopic fungi. Fungi and related organisms cannot be dealt with in 

 this volume, but it may at least be said that the use of mouldy hay 

 and similarly affected feeding stuffs is attended with some danger, 

 which is not yet very clearly defined. 



Effect of Soil, Climate and Cultivation on the Toxic Properties of 

 Plants. In general, wild poisonous plants are richer in either alkaloids 

 or glucosides than the same species when cultivated, though there are 

 exceptions. In many cases it is found that plants vary considerably 

 in toxicity, or the percentage content of the poisonous principle, accord- 

 ing to soil, light, moisture, etc. Solanaceous plants in particular vary 

 in this way, and one or two instances may be given as examples. 

 Solanum nigrum varies so much that it has been regarded as harmless 

 in one country and quite poisonous in another (p. 52). 



Experiments conducted at the Arlington Experimental Farm, 

 Virginia, showed that in 24 first-year plants of Atropa Belladonna 

 grown in 1910 the alkaloid contents of the leaves varied from 0-334 to 

 0-700 per cent., and averaged 0-547 per cent. In 1911 the alkaloid 

 contents (usually the average of five pickings) of the leaves of 59 plants 

 varied from 0-306 to 0-766 per cent., and averaged 0-532 per cent. In 

 1912 the alkaloid contents (commonly the average of 5 pickings) of the 



