28 LECTURES ON IMMUNITY 



seems not to have known the results of Madsen's and my 

 investigations on this point; instead he drew untenable 

 conclusions from Brodie's 1 experiments, which indicate 

 that diphtheria-antitoxin does not in an appreciable degree 

 pass through a gelatin filter in a very short time. We 

 may therefore leave the theoretical considerations of Craw, 

 which he furthermore himself considered not to be appli- 

 cable to certain of his own experiments. 



Others say, with Nernst, 2 that the laws of van 't Hoff 

 are not applicable to colloids, i.e. to toxins and antitoxins. 

 Nernst has himself shown that diffusion is caused by and 

 is proportional to the osmotic pressure. As now toxins and 

 antitoxins diffuse just as other known substances, we may 

 conclude that they obey van 't Hoff's law of osmotic pres- 

 sure. In Madsen's and my experiments these substances 

 showed themselves to be distributed in the different layers 

 of gel just as these laws demand. And if van 't Hoff's 

 law is found to be valid for the osmotic pressure of these 

 substances, then also the laws of chemical mass-action 

 (Guldberg and Waage's law) must hold good for their 

 reactions. And even if we did not know that these sub- 

 stances behaved in this regard as do other substances, we 

 would be entitled to work with this quite natural hypothe- 

 sis, until it was shown with great accuracy that the hypoth- 

 esis was wrong. Otherwise we would proceed in a 

 manner wholly different from that used in the other 

 disciplines of science. 



There has been very much discussion of this question 



1 T. G. Brodie : Journ. of Pathology and Bacteriology, 97. 460-464 (1896). 

 3 Nernst : "Uber die Amvendbarkeit der Gesetze des chemischen Gleich- 

 gewichts," Zeitschr.f. EUktrochemie, 10, No. 22 (1904). 



