324 JOURNAL OF THB WASHINGTON ACADEMY OF SCIENCES VOL. 11, NO. 14 



bility, dissociation, colloidal state, electrical charge and the like. 

 Of course, in the last analysis the physical state is but an expression 

 of the chemical constitution and vice versa, but these are problems 

 for the chemist, not the pharmacologist. 



However, I do not mean to be understood as stating that chemical 

 constitution has nothing to do with physiological action. I mean 

 merely that very frequently changes in constitution produce changes 

 in action chiefly because they influence the physical properties of the 

 substance rather than its power of reacting chemically with other 

 substances. Certainly very slight changes in constitution often 

 produce very great changes in physiological action. You all know that 

 stereo-isomerism influences the taste of simple amino acids, some being 

 sweet, some bitter;^ that one form of asparagin is sweet while the 

 enantiomorphous form is tasteless; that 1-adrenalin causes the smaller 

 arteries to contract greatly while d-adrenalin is far less active.^ The 

 examples might be multiplied almost indefinitely. Indeed, as we shall 

 see later, substances of a very widely different chemical structure may 

 have a very similar action. Of these we may be sure that their action 

 depends rather upon their physical than their chemical properties. 



What I have to say tonight will deal as much with physical or 

 physico-chemical properties as with chemical constitution. Moreover, 

 I do not propose to deal with many simple inorganic substances like 

 arsenic, iodine or phosphorus. The physiological action of many of the 

 elements seems to be an intrinsic property as much as their atomic 

 weight. Indeed, within the same group of the periodic system the 

 toxicity of kations, with certain exceptions, increases with the increase 

 of the atomic weight.^** Until we know far more than we do now 

 concerning the underlying causes for the physical properties of the 

 elements we are not likely to know why, for example, iron is less 

 poisonous than cobalt. It is much the same question as why bromine 

 is red and chlorine green. We do know, however, that elements like 

 arsenic, phosphorus and nitrogen, which exhibit variable valence, maf 

 be toxic and we suspect that their action is probably in some way 

 connected with their change from one state of valence to another. We 

 also know that in some way the toxic action of kations and anions is 



* B. Oertly and R. G. Myers. A new theory relating constitution to taste. Journ. 

 Amer. Chem. Soc. 41: 861. 1919. 



^ W. H. ScHULTz. Quantitative pharmacological studies: Adrenalin and adrenalin-like 

 bodies. Hygienic Lab. Bull. 55, U. S. Public Health and Marine Hospital Service, 1909. 



" Blake. Compt. rend. 1839; Proc. Roy. Soc. London 1841. Amer. Journ. Sci. 1874; 

 Ber. deutsch. Chem. Ges. 14: 394. 1881. 



