584 



SCIENCE 



[N. 8. Vol. XXXIV. No. 879 



salts causing the same degree of shrinkage 

 when acting upon the same cell, must have 

 a water attracting power of the same de- 

 gree. DeVries called such solutions, i. e., 

 those having an equal water attracting 

 force, isotonic solutions; and the simple 

 relations, which appeared to exist between 

 different concentrations of these solutions, 

 he named the isotonic coefficients. 



De Vries gave a lecture on these re- 

 searches in the Amsterdam Academy of 

 Sciences, and luckily had in his audience 

 my late teacher and master, Professor 

 Bonders, who, as usually, came back to the 

 laboratory in the afternoon. Bonders was 

 in the habit of discussing matters with me 

 whenever a scientific problem attracted his 

 particular interest. It was not, I think, 

 that the great man wanted to hear the 

 opinion of his assistant, but rather the fact 

 that these discussions gave him an oppor- 

 tunity to formulate his thoughts and thus 

 helped him to clarify the problem. Some- 

 times I could not help thinking that my 

 master went a little too far in his thoughts, 

 but this time everything was clear to me. 

 He spoke about the lecture of de Vries to 

 which he had listened a short while before 

 and the question at once arose whether 

 de Vries 's findings for the plant cell would 

 hold true for the animal ceU. 



I began work at once and it was the red 

 blood corpuscles that I chose as my ma- 

 terial. The first step was to find a concen- 

 tration capable of inducing plasmolysis in 

 these cells. But I failed to find it. No 

 plasmolysis could be observed in my experi- 

 ments. Then I turned to the study of 

 escape of coloring material from the red 

 blood corpuscles. And in the next year 

 my teacher was able to report on my behalf 

 the results of my investigations before the 

 Amsterdam Academy of Sciences.® It was 



' H. J. Hamburger, Proces-Verbal der Koninkl. 

 Akademie van Wetenschappen te Amsterdam, De- 



actually found that the red blood corpus- 

 cles were also subject to the law of isotonic 

 coefiicients. Between the concentrations 

 of salt solutions causing the escape of color- 

 ing matter from the blood corpuscles the 

 same numerical relation exists as between 

 the concentrations of salt solutions in- 

 ducing plasmolysis in the same plant cell. 

 These researches on the blood corpuscles 

 (1883) marked the beginning of modern 

 physico-chemical research in the medical 

 sciences. 



It was repeatedly stated that Van't 

 Hoff's theory of osmotic pressure laid the 

 foundation for these investigations on the 

 blood corpuscles, but this is decidedly a 

 mistake. 



The real basis for this work was given 

 in de Vries 's researches in plant physiol- 

 ogy. These investigations and my own 

 hx/natological researches furnished impor- 

 tant data for an experimental proof of 

 Van't Hoff's theory, which was based prin- 

 cipally on thermodynamic considerations 

 and on Pfeffer's findings and which was 

 published for the first time two years later 

 (1885). This historical accuracy, it is 

 hoped, may not be regarded as an under- 

 estimation of the importance of Van't 

 Hoff's theory for the medical sciences. 



It is true that the physico-chemical re- 

 searches in the medical sciences do not owe 

 their origin to the influence of Van't Hoff's 

 theory and that these researches were con- 

 tinued with success for almost a decade 

 independently of the theory of osmotic 

 pressure.' However, it must be strongly 



cember 29, 1883. German translation in Festiand 

 der Biochemischen Zeitsc-hrift, H. J. Hamburger 

 gewidmet zur Feier seiner vor 25 Jahren erfolgten 

 Doktorpromotion, S. 1, 1908. Berlin, Julius 

 Springer. 



' To these belong among others the first deter- 

 minations of the water attraction power (osmotic 

 pressure) of the blood serum and other animal 

 fluids by means of the study of the escape of the 



