1915] 



DAVIS — ENZYME ACTION IN MARINE ALGAE 789 



Three general antiseptics were used — toluene, alcohol to 20 

 per cent, and 5 per cent thymol in chloroform. Toluene was, 

 in general, the most satisfactory. Usually it was used to 2 

 per cent concentration, but where large surfaces were exposed, 

 as high as 4 per cent was found necessary. The chloroform- 

 thymol was also very efficacious, but in the carbohydrate ex- 

 periments chloroform could not be used because of its power 

 of reducing copper. In the lipase work the substrate was made 

 up to 20 per cent alcohol since the action seemed to proceed 

 best in the presence of this antiseptic. In all cases where the 

 experiments were maintained over a considerable period of 

 time, it was necessary to add additional antiseptic from time 

 to time. 



Checks were set up in all experiments — on the substrate, on 

 the material used to demonstrate enzyme action, and on the 

 substrate plus such enzyme material boiled to destroy any 

 ferments that might be present. 



CARBOHYDRASES OF THE ALGAE 



In these experiments the alcohol precipitate from an 

 aqueous extract of crushed, fresh or dried, algal tissue was 

 employed as an enzyme source, this precipitate being diffused 

 in such a volume of distilled water that one gram of the 

 original material was represented by 5 cc. of the diffusion. 

 Thus one can more closely compare the amounts of enzyme 

 present in definite amounts of different algal tissue. The 

 number of cubic centimeters of diffusion will be noted in con- 

 nection with each set of experiments. 



Substrates. — Starch, dextrin, inulin, sucrose, maltose, lac- 

 tose, glycogen, and in one or two cases, laminarin isolated 

 from Laminaria Agardhii, were used as substrates. These 

 were made up in 1 per cent concentrations with the ex- 

 ceptions of maltose and glycogen, where .25 per cent, and 

 laminarin, where .5 per cent concentrations were employed. 



Of the many suggested methods for making up starch paste, 

 the following one used by Clark ('11) was found to give the 

 best satisfaction. Ten grams of potato starch were weighed 

 out and placed in a beaker with 250-300 cc. of distilled water. 



