PRODUCTS OF METABOLISM 177 



are probably specific substances. Different enzymes have 

 been noted which are able to produce fermentations of 

 saccharose (inverting enzymes) ; of dextrose, lactose, cellulose 

 (amylolytic enzymes), producing eventually carbon dioxide 

 and water ; which coagulate milk similar to rennet (rennet 

 enzymes); which digest protein, producing amino-acids, etc., 

 (proteolytic enzymes); and that split fats into fatty acids 

 and glycerine (steatolytic enzymes). 



Colloidal solutions of metals, such as platinum, show 

 many similarities in action to known enzymes. These col- 

 loids can be made to produce changes in proteins almost 

 identical with those produced by true enzymes. They are 

 also affected by chemical changes and by temperature in the 

 same way as enzymes. 



There are many writers who hold the view that all so-called 

 enzyme action is due to physical changes produced in the 

 various organic substances, and not to any definite chemical 

 reactions. The magnetism in the magnetic bar is in many 

 ways similar to an enzyme. When heated magnetism and 

 enzymes disappear, when treated with acids and alkalies 

 they disappear, and neither can be isolated in a pure state. 

 Arthus thinks that enzymes are not forms of matter, but that 

 they are forms of energy. 



Enzymes possess the power of producing chemical changes 

 without entering to any great extent into the reaction. They 

 can produce an oxidation of a sugar compound into carbon 

 dioxide and water, and can break down protein compounds 



