36 STOCK-POISONING PLANTS OF MONTANA. 



for a hog, notwithstanding the difference in size. It takes over a 

 pound of the sugar of lead (lead acetate) to kill a horse, while a tenth 

 of tha<" quantity will kill a cow of equal weight. Chemical reaction 

 between the digestive juice of various animals and the poisons con- 

 tained within the plants, as Avell as the chemical reactions between 

 the poisons and the chemical constituents of the various food stuffs, 

 undoubtedly have considerable influence in some cases on the effect 

 of poisons before they are taken mto the blood. If, for example, a 

 plant containing a poisonous alkaloid were eaten together with another 

 containing tannin, some or all of the alkaloid would be rendered inert 

 by the formation of the insoluble tannate of the alkaloid. So, too, 

 phj^siological processes in one animal ma}' tend to retard the absorption 

 of the poison from the stomach, while in others they may exert no 

 such reaction. In the latter case, of course, the poison will exert its 

 influence on the system before there is any chance for it to be eliminated. 



The fundamental rule relative to the effect of the poisoning of any 

 animal is that a certain amount of the toxic substance must be in cir- 

 culation in the blood and that the amount circulating depends not only 

 on the amount administered but on the rapidity with which excretion 

 takes place. It may, therefore, happen that very poisonous substances 

 may so quickly ))e eliminated by the animal that there will never at 

 an}' one time be a sufficient amount of it in the blood to produce a 

 fatal effect or even any effect at all.^ 



From the foregoing it is evidentl}' quite probable that the suscepti- 

 bility to some poisons will differ in the case of rabbits as compared 

 with that of stock. As a rule, however, the results obtained with rab- 

 bits are considered by pharmacologists as trustworthy indications of 

 the effects which would be obtained by similar experiments upon stock. 

 The animals must, of course, be in a healthy condition when used. 



The general method of procedure, which after a few preliminary 

 experiments was adopted in our work, was as follows: 



A delinite quantity of the fresh plant or an extract thereof was offered 

 to a rabbit of known Aveight and the results noted in chronological 

 ordei . The weight of the fresh material eaten was determined by sub- 

 tracting the weight of the residue left after a certain time and making 

 a proper allowance for the loss of its weight due to the evaporation 

 of water from its tissues. To ascertain this loss a weighed portion of 

 the material identical Avith that Avhich was fed Avas subjected as far as 

 possible to the same e\^aporation influences and again weighed at the 

 end of the experiment. 



In several cases it was found that the rabbits would either eat but 

 a very small quantity of the plant or eat it too slowly for a satisfactory 

 test. In this case extracts were made and fed in known fjuantity by 



' Hermann's Experiniontal Pharmacology, p. ()•"'. 1S8;1 



