352 Messrs. R J. Caldwell and S. L. Courtauld. [May 9, 



the other methyl-a-glucoside, cannot be decided at present : the discovery of 

 an oi-glucase different from maltase, however, is of considerable interest as an 

 indication of the existence of separate a-glucosidoclasts. 



It may be pointed out that the disproportion observed by E. F. Armstrong* 

 in the relative rates at which maltose and methyl-a-glucoside are hydrolysed 

 by maltase and acids respectively was perhaps in a measure due to the fact 

 that the " maltase " contained the two enzymes which are capable of hydro- 

 lysing the glucoside, but only one capable of acting on the maltose. 



Method follovjed. — The experiments were carried out in small closed 

 flasks, which were heated in a Hearson incubator ; excepting pipettes and 

 funnels, all the vessels used were of hard Jena glass. The top yeast used was 

 a pale ale yeast, for which we were indebted to Mr. Julian Baker. The 

 freshly pressed yeast was first well washed with water saturated with 

 toluene and without loss of time thoroughly drained on a vacuum filter ; it 

 was then rapidly dried on bibulous paper, the drying being completed by 

 exposure over sulphuric acid in vacuo. Professor Emil Fischer had the 

 kindness, at Dr. E. F. Armstrong's request, to obtain for us a quantity of 

 dried bottom yeast (8. Cerevisice, Eace 12, Berlin), which was ostensibly 

 similar to that which he had used. 



To prepare the extract, one part of dried yeast was added to 20 parts 

 of water and a little toluene ; the mixture was then digested at the required 

 temperature, being shaken at intervals ; it was finally clarified by filtration. 

 Usually, the liquor was in contact with the yeast during 4 to 6 hours, experi- 

 ment having shown that nothing was gained by extending the period. 



Solutions of the hydrolytes were prepared containing four-tenths of a 

 gramme-molecular proportion per litre. Equal volumes of the solution (20 c.c.) 

 and of the yeast extract, heated to the temperature at which hydrolysis was 

 to be effected, were quickly mixed in a flask ; a sample of 10 c.c. was at once 

 withdrawn and, the enzyme having been destroyed by the addition of a single 

 drop of concentrated sulphuric acid (or in the case of cane-sugar, a solution 

 of caustic soda), 10 c.c. of a 10-per-cent. solution of sodic acetate was run in ; 

 the liquid was then heated to 80° to precipitate the dissolved protein as far as 

 possible. Finally, the filtered solution was examined polarimetrically in a 

 20-mm. tube at 25°. Meanwhile, the main bulk of the mixture had been 

 placed in the incubator, where it was kept at the required temperature ; at 

 intervals, usually after 24, 48 and 72 hours from the commencement of an 

 experiment, 10-c.c. samples were withdrawn, and treated as before described. 



The amount of the substance hydrolysed was estimated by dividing the 

 observed change in rotatory power by that calculated to correspond to 

 * ' Koy. Soc. Proc.,' 1904, vol. 74, p. 193. 



