54 



COLLOIDS IN BIOLOGY AND MEDICINE 



This may be illustrated by the following figures: 



All the facts mentioned above indicate what EINSTEIN emphasized 

 even in 1905, that there is a gradual transition from crystalloid to 

 colloid solutions, and that the translatory movements of the particles 

 of a colloid correspond to the diffusion of crystalloid molecules. 



[SiR WILLIAM RAMSAY, in a paper entitled "Pedetic Motion in 

 Relation to Colloidal Solutions" published in "Chemical News," 

 Vol. 65, p. 90 [1892], stated as follows: 



" I am disposed to conclude that solution is nothing but subdivi- 

 sion and admixture, owing to attractions between solvent and dis- 

 solved substance accompanied by pedetic motion; that the true 

 osmotic pressure has, probably, never been measured; and that a 

 continuous passage can be traced between visible particles in suspen- 

 sion, and matter in solution; that, in the words of the old adage, 

 Natura nihilfit per saltum." Tr.] 



Diffusion in Jellies. 



Hitherto we have considered only diffusion in pure aqueous solu- 

 tion; in the organism, however, it occurs in a more or less dense 

 colloidal medium. When the concentration of the colloid is not 

 very great, the diffusion is not much impeded. Until recently it 

 was even believed that diffusion of a crystalloid solution in a jelly, 

 e.g., gelatin or agar, occurred just as rapidly as in pure water. This 

 was the result of employing unsuitable experimental methods. 

 The investigations of H. BECHHOLD and J. ZiEGLER,* 2 KURT MEYER,* 

 PETER NELL* and L. W. OHOLM showed definitely that electrolytes 

 and non-electrolytes experience a resistance in jellies which reduced 

 the rate of diffusion by obstructing their paths, and that the inter- 

 ference increased if the gel became more concentrated. 



