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ILLINOIS ACADEMY OF SCIENCE 



protoplasmic membranes. On this basis he conceived 

 that they were not only held within the cell, but also localized 

 within the separate compartments of the multivacuolate proto- 

 plasm, as he pictured it. It has been shown, however, that en- 

 zymes are very highly dispersed colloids and that they diffuse 

 readily through 10 per cent gelatin and Ruhland (13) believes 

 through cell walls and protoplasm generally. This author 

 thinks retention within the cell is due either to adsorption or 

 more likely to actual chemical union with the protoplasm. He 

 believes that this also accounts for the localization of enzymes 

 within the cell. 



In many of their activities enzymes behave like colloids. 

 The question has often been raised whether their main function 

 is a typical colloidal reaction or more of the nature of reactions 

 in molecular solutions. The evidence generally is in favor of 

 the second. In the first case diffusion should play the main 

 role and the speed coefficient for 10° C rise in temperature 

 should not exceed 1.25. For lipase, invertase, catalase, and 

 tryosonase the coefficient is about 1.5, but for most enzymes 

 it is from 2 to 3. Where the coefficient is as low as 1.5 dif- 

 fusion between the two phases of the system (aided by in- 

 creased Brownian movement of the enzymes and reduced vis- 

 cosity of the medium) may be the main rate determining pro- 

 cess ; but where the coefficient lies between 2 and 3 the rate is 

 probably determined by a reaction typical of homogeneous 

 systems. The action of enzymes is, however, very complex, 

 involving adsorption by the substratum and often by products 

 of their action, and many other disturbing factors. As a conse- 

 quence we are far from a quantitative statement of the kinetics 

 of enzymes. 



VII IMMUNITY BODIES AS COLLOIDS 



In general when the physiological significance of colloids 

 is discussed the characters and behavior of immunity bodies 

 are used as illustrations. These show much in common with 

 enzymes and many of the questions concerning the colloidal 

 nature of the one has been asked and answered similarly for 

 the other. Space does not permit the discussion of the colloidal 

 characters of this group of substances and besides an excel- 

 lent statement can be found in many texts (1, 2, 28). 



VIII SOME COLLOIDAL PHENOMENA OF SOILS 



There is a large number of reactions in the soil that are 

 colloidal in nature and of great interest to the plant physiol- 

 ogist. The soil is the environment of approximately one-half 



