November 3, 1911] 



SCIENCE 



585 



emphasized that the influence which this 

 theory exerted on the further development 

 of physico-chemical research in medicine 

 has become one of tremendous value. This 

 will become clear from our further consid- 

 erations. 



But even during the decade referred to 

 this theory exerted considerable influence. 

 For some time after its appearance in its 

 completed form (1887) this theory had a 

 stimulating influence, however latent this 

 may have been. Such terms as "water-at- 

 tracting force" and "isotonic coefficients" 

 no doubt served well the purpose of suc- 

 cessful work, but their meaning was rather 

 puzzling and their explanation by the new 

 theory was received like a revelation. 

 Furthermore, the theory of osmotic pres- 

 sure with its more exact terminology and 

 concepts helped much in shedding new 

 light on what had been accomplished inde- 

 pendently of it in the decade above men- 

 tioned. 



It may well be asked why it was that 

 relatively many years passed before Van't 

 Hoff's theory came to be recognized in the 

 medical literature. An explanation for 

 this, I think, is given in the fact that the 

 theory met with rather unfavorable criti- 

 cism among the professional chemists^ and 



coloring matter from the blood corpuscles (1884) 

 and the investigations on the concept of "physi- 

 ological salt solutions," on the influence of CO2, 

 alkali and acids on blood; here belong also the 

 investigations on lymph, resorption, etc. 



' An illustration to this we may well see in the 

 following incident: 



The board of directors of the Deutsche Chem- 

 ische Gesellschaft had in 1893 invited Van't Hoff 

 to give a lecture on his physico-chemical researches. 



In this lecture on January 8, 1894, Van't Hoff 

 is said to have hesitated between two themes and 

 made the following very significant remark : ' ' On 

 the other hand there was the theory of diluted 

 solutions and osmotic pressure, but I preferred 

 to leave the choice to the directors, because I 

 should not like to speak on a theme which may 



also from the circumstance that the field 

 of work opened up by the theory of isotonic 

 coefficients was so large and the problems 

 suggested by it so numerous that there 

 actually was no time to take into consid- 

 eration also the theory of osmotic pressure. 

 Besides, for some time — ^we may well say, 

 in the first ten years — little interest was 

 shown in these new researches and accord- 

 ingly the number of workers was very 

 scarce. Indeed we were almost alone in 

 our efforts. 



However this may have been, that much 

 at least is quite certain, that the theory of 

 osmotic pressure announced in 1885 would 

 not have achieved such great success, had 

 it not been for the fact that Van't Hoff 

 was aile to utilize Arrhenius's theory of 

 electrolytic dissociation as a supplementary 

 one to his own. 



Not infrequently one finds that there are 

 very unclear and inexact notions about this 

 rather intricate matter. It may, therefore, 

 not be uninteresting to give an account of 

 how it developed, using the original publi- 

 cation as a guide. 



What was the actual situation? 



According to Van't Hoff the dissolved 

 substance, when in a diluted solution, be- 

 haves like a gas. He found that in such 

 solutions the particles of the dissolved sub- 

 stance diffuse in their medium, and in this 

 way exert a pressure on the walls of the 

 dish. If a watery solution is made up in 

 a dish, whose walls are semi-permeable, 

 that is, impermeable to the medium of the 



at present appear rather undesirable on account 

 of the unfavorable criticism at the hands of pro- 

 fessional colleagues, which we all highly esteem. 

 [Italics mine.] However, the directors chose the 

 theory of solutions." (Cf. J. H, Van't HofE, 

 "Wis die Theorie der Losungen entstand," Ber. 

 der Deutschen Chem. Gesellschaft, XXVII., I., 

 1894, p. 6.) 



This, then, was nine years after Van't Hoff's 

 famous publication in the Swedish academy. 



