tate diagnosis by suggesting the plants that should be 

 looked for when certain symptoms are observed and plant 

 poisoning is suspected. 



A word may not be inopportune on the need of re- 

 search on poisonous plants. The indefiniteness with 

 which many statements have had to be made and the 

 dearth of positive experimental work upon which to base 

 conclusions have been keenly felt in the preparation of 

 these pages. Two lines of attack are evident, one based 

 on the detailed chemical analysis of the poisonous plant, 

 the other on feeding experiments with the plants them- 

 selves. These two lines are complementary and both very 

 necessary. The toxic substance having been determined, 

 it is often at once evident what the chemical antidote 

 should be. Moreover, much is known or could be easily 

 learned of the conditions of its action. For example, how 

 much is immediately apparent when it is known that 

 prussic acid is the chemical responsible for Cherry or 

 Sorghum poisoning. Knowing the volatile character of 

 this toxic substance we can at once see why the dried 

 fodder is harmless. Again, when the chemical responsi- 

 ble for Hemlock poisoning was found to be polymerized 

 by heat much of the erratic character of the poisoning 

 in this case was understood. It was quite evident why 

 this plant was less dangerous in the heat of summer. 

 Still all the emphasis must not be placed on this line of 

 research, essential though chemical analysis assuredly is. 

 The constitution of a plant is exceedingly complex and 

 several factors may co-operate in producing the poison- 

 ous effects. As mechanical injury in the case of Skunk- 

 tail Grass opens the way for bacterial infection, so in the 

 case of Horsetail poisoning, it is quite possible that irri- 

 tation of the digestive tract by the indigestible silica may 

 pave the way for the attack of a chemically poisonous 

 substance. It is thus only by feeding experiments, ap- 



