INTRODUCTION. 9 



Mayer noted, in in^'cstigat.ions with dextro and tevo forms of nicotine on guinea-pigs, 

 tluit the former is only luilf as poisonous as the latter, and tliat the two differ markedly 

 in certain respects in their physiological actions. Poulsson, in studies of the actions of 

 the cocaine group, found that the application of a 5 per cent solution of racemic cocaine 

 gives rise to a quicker and more intense but less lasting action than the same strength 

 of solution of the la!V0 form. Albertoni, in his investigations of the actions of certain 

 drugs on the brain, recorded differences in cinchonine and cinchonidine, which are stereo- 

 isomers, the former being the dextro form and the latter the lajvo form. The latter is 

 the less acti^'e, and its actions differed somewhat from those of the other. Ehrlich and 

 Einborn found that the physiological actions of laivo-hyoscine (scopolamine) and racemic 

 hyoscine (atroscine) differ. Piutti records that dextro-asparagine is sweet and Ltcvo- 

 asparagine tasteless; and Menozzi and Appiani discovered the same peculiarity in gluta- 

 minic acid. Werner and Com-ad, in examinations of odors, noted differences in the esters 

 of the dextro- and Ijevo-trans-hexohydro-terephthalic acids; and Schmidt and Tiemann 

 state that the optically active terpenes are more odorous than the racemic forms. Cushny, 

 in experiments with atropine (racemic hyoscyamine) and its optical isomers dextro-hyo- 

 scj'amine and hevo-hyoscyamine, found "that the two hyoscyamines differ to a marked 

 extent in their pharmacological actions, the lajvo-rotatory natural base possessing a very 

 powerful action on the terminations of the nerves of the salivary glands, heart, and iris, 

 while the dextro-rotatory artificial base is almost devoid of effect on these organs, but 

 exercises a stronger stimulating action on the central nervous system of .the frog. The 

 action of atropine (racemic hyoscyamine) is the resultant of the actions of its compo- 

 nents, la3vo- and dextro-hyoscyamine, and it thus affects the ner\'e terminations about 

 half as strongly as lajvo-hyoscyamine, while possessing a more distinct stimulant action 

 on the central nervous system." In another study in which the dextro-, tevo-, and 

 racemic hyoscines were the subjects, it was recorded that Icevo-hyoscine acts twice as 

 strongly as the racemic form on the secretory nerves of the salivary glands and on the 

 inhibitory nerves of the heart; and that lajvo- and racemic hyoscines have the same effect 

 on the central nervous system in man and animals and on the terminals of the motor 

 nerves of the frog, in which animal, however, they seem to be without effect on the central 

 nervous system. 



Such facts might be materially amplified, but anyone who knows them and has any 

 real ap])reciation of the meanings of the differences in physiological, pharmacological, and 

 toxicological actions, and of the relations of these differences to the configurations of the 

 molecules, must, if he does not conceive of the stupendous importance of stereochemistry 

 to protoplasmic processes, be absolutely devoid of imagination. 



Moreover, the fact that a given isomeride may he transmuted into another form under 

 conditions which are identical with or similar to those which exist in plant and animal 

 life is one of apparently the greatest and most widespread fundamental biological impor- 

 tance. It has already been found that many stereoisomers show marked evidences of 

 unstability, tending under certain conditions to be changed with the greatest readiness 

 from one form into another; that the degree of unstability varies, the direction of the 

 change usually being from the more unstable to the less unstable configuration; and that 

 in some, and perhaps in all, instances, the transmutation may be more or less markedly 

 accelerated or inhibited by very simple conditions, as has been shown in the case of cer- 

 tain sugars and related bodies, ethylenes, cobalt-amines, diazo-compounds, chromium 

 and silicon and platinum compounds, and other bodies. Such transformations may be 

 brought about dircdhj, whereby one form is changed into another by a simple trans- 

 position of molecular components; or indirectly, by the formation of an intermediate 

 compound. Direct transmutation may be caused by spontaneous change, in accordance 

 with the laws governing the establishment and maintenance of equiUbrium of solutions; 



