THE JOURNAL OF PHARMACOLOGY. 249 



progress has been made in expressing the laws of mixture, combination, 

 sokition. dissociation, and chemical transformation on a generalized 

 basis, and chemistry and chemical physics are gradually being brought 

 under the sway of dynamical laws. 



PHYSICAL CHEMISTRY AND THILRAPEUTICS. 



Within the last 15 years the remarkable and daring theories of van't 

 Hoff and his followers upon the nature of dilute solutions, based upon 

 certain physical data (viz., osmotic pressure, alterations of the boiling 

 point and freezing point), together with Arrhenius's hvpothesis of ionic 

 dissociation, have largely engaged the attention of physicists and chem- 

 ists ; nor have they failed to make their impress upon pharmacological 

 investigations. 



The earliest reference I have noted in pharmacological work to 

 van't Hoff's important researches is contained in a paper by Hofmeister 

 (Zur Lehre von der Wirkung der Salze. Archiz' f. exper. Ptahol. und 

 Pharmak. Bd. xxv., 1889). 



Tn the same journal (Bd. xxix., 1892) is a suggestive paper by 

 Dreser, "Ueber Diurese und ihre Beeinflussung (lurch pharmakolog- 



ische Mittel." 



In this connection T may specially refer to Dr. C. R. Marshall's 

 excellent summary of the "Ion" question, published in the Practitioner, 

 February, 1898. In this paper which broached the subject for the first 

 time in an English medical journal, he gave an abstract of Kronig & 

 Paul's theorv of the action of antiseptics in the light of the electrolytic 

 dissociation theory, and also of Loeb's views on the physiological effect 

 of various radicals. 



But, furthermore, we have to take into account, not only the number 

 and kind of atoms in the molecule, and their interior arrangement and 

 grouping (constitution), but certain physical properties of compounds 

 previously inexplicable have found their explanation in another develop- 

 ment of chemical theory which has proved extraordinarily fertile. I 

 refer to stereo-chemistry — i.e., the doctrine of the spatial configuration 

 of the molecule. This theory has done much to elucidate the difficult 

 problems of isomerism in organic chemistry, and we cannot doubt that 

 it will shed light upon chemical transformations occuring in the organ- 

 ism. Dr. Emil Fisher has published in the Zeitsch. f. Physiolog.. 

 Cherii., 1899, an important paper, in which he seeks, in conjunction with 

 Thierf elder, to explain the selective action exhibited by the enzymes 

 either in effecting fermentation or in producing hydrolysis. 



It is well known, for example, that a glucoside, e.g., salicin, may 

 be attacked by one enzyme (emulsin) and not by another (yeast en- 



