INTRODUCTION. 7 



stances have been found to cause vasodilation in warm-blooded 

 animals, but they constrict the blood vessels of the frog. 



Experiments with apomorphin likewise show that the reaction to 

 this substance varies in different species of animals. The resistance 

 of the cat to this drug is, according to Guinard, 31 ten times greater than 

 that of the dog, and the latter is more sensitive than the rabbit to 

 the crystalline form of apomorphin when given intravenously. 

 According to Robert 45 amygdalin is without effect on dogs, but it 

 is poisonous to rabbits. Lapicque 49 found that the toxicity of 

 curara varies in different species of frogs, the dose required to pro- 

 duce paralysis in Rana esculenta being three times greater than in 

 Bufo vulgaris. Weir Mitchell 59 pointed out long ago that turtles 

 stand enormous doses of curara. Schmiedeberg's experiments with 

 caffein on Rana temporaria and Rana esculenta (and more recently 

 those of Jacobi and Golowinski 42 with caffein, theobromin, and 

 theophyllin) are also of interest in this connection. These experi- 

 menters observed well-marked differences of reaction to methyl- 

 xanthins in these closely allied forms. 



Experiments with quinin have shown that the action of this sub- 

 stance differs in some animals. It causes a fall of temperature imme- 

 diately after its administration in the guinea pig, but frequently 

 produces, at first, a rise of temperature, followed by an unimportant 

 fall, in rabbits, dogs, and man. 



The numerous investigations which have been carried out on the 

 effect of atoxyl within recent years have contributed much to the 

 comparative pharmacology of this substance. Although the symp- 

 toms and organic changes produced by this substance in a variety of 

 animals present no great differences, the resistance of some has been 

 found to vary; according to Koster 46 it is more toxic for dogs than 

 for rabbits. A number of other substances have been found by 

 various experimenters to vary in toxicity for different species of 

 animals. Cantharadin, phenol, atropin, and strychnin may be men- 

 tioned as illustrations. 



Pharmacological studies on lower forms of life have also revealed 

 marked variations in the effect of some poisons. Observations made 

 by Danilewski 18 with hydrochinone indicate that solutions of 1 to 

 100 or 200 are toxic to Celentrates, causing paralysis in these organ- 

 isms. Echinoderms are killed within one or two hours in 1 to 1,000 

 or 2,000 solution, while in Vermes even weaker solutions cause 

 tetanus and finally paralysis. The experiments of Drzewina 19 with 

 potassium cyanid are also interesting in this connection. Teleosts 

 placed in 100 cc of sea water containing twentieth-normal potassium 

 cyanid showed signs of asphyxia and died in 10 to 20 minutes. 

 Actinia placed in a solution of sea water containing five times as 

 much potassium cyanid were active on the thirteenth day of the 



