Metabolism; Digestion and Translocation 269 



particularly considered, are believed to act by oxidation, 

 and simple, molecular decomposition may also occur. 

 The products may be diverse, as is common, or alike, as 

 when maltose is transformed into two molecules of 

 dextrose. 



From relatively recent work it has also become certain 

 that enzymes are important in synthetical processes as 

 well as in the analytical ways referred to. In the former 

 case they are said to possess a reversible action ; that is, 

 for example, - - contrary to the instance above cited, where 

 cane-sugar may be hydrated with the production of hex- 

 oses, - - the hexose molecules may be built up by means of 

 an enzyme into the anhydride or disaccharid form. Re- 

 versible actions appear to be very common, but little 

 definite information is available at the present time. 



Direct sunlight is promptly injurious to enzyme action. 

 Fermentation is also commonly weakened at temperatures 

 above 50 C. and " death ' may result above 70 C. 

 Most toxic agents are injurious to enzyme action at con- 

 centrations much above the normal death-point of the pro- 

 toplasm, but at considerable dilution acids or alkalies may 

 be stimulating. While a weak percentage of alcohol and 

 a saturated solution of chloroform may not be injurious, 

 strong alcohol may be fatal, so that in the precipitation of 

 enzymes by 95 per cent alcohol there may be danger of 

 losing the product. 



156. Carbohydrate enzymes and their products. - 

 Of the many carbohydrate enzymes it is possible here 

 briefly to consider only a few. Chief in importance among 

 these are diastases (amylases), acting upon starch, the 

 hydrolysis and splitting of which yields a series of dextrins, 



