504 



Dr. E. F. Armstrong. 



[Apr. 5, 



agitated with 200 c.c. water, using the modified ice-cream mixer 

 described by Moody : * after 4 — 6 hours, when the grains were 

 reduced to a fine pulp, 5 c.c. of toluene was added and the closed 

 vessel set aside at about 20° over night. The milky liquid was then 

 decanted and rapidly filtered, filtration being repeated, if necessary, 

 until a clear liquid was obtained. The extract thus prepared was a 

 clear yellow liquid : as changes took place in it on standing, it was 

 used without delay. It is probable that a nearly saturated solution 

 of the enzyme is obtained by operating in the manner described, as 

 the residue is still very active ; thus on extracting it for a further 

 period of 24 hours with 200 c.c. water, an extract was obtained of 

 about one-fourth the activity of the first. 



The unfiltered milky extract is much more active than the filtered, 

 probably because it contains some enzyme in suspension ; it may also 

 be mentioned that repeated filtration seems to diminish the activity 

 even of the clear liquid. Although lactase prepared by the ordinary 

 methods, involving precipitation and subsequent washing with alcohol, 

 possesses some power of inducing the hydrolysis of milk sugar, it is 

 only feebly active in comparison with an extract prepared as above 

 described. The following figures, showing the parts per hundred of 

 sugar hydrolysed during the intervals indicated in 50 c.c. of a 

 5 per cent, solution of milk sugar, may be quoted in illustration : — 



1 hr. 4 hr. 24 lir. 



Solution containing 20 c.c. filtered extract 4*8 16 45 



„ „ 20 c.c. unfiltered extract ... 15 38 80 



40 c.c. „ „ ... 29 57 86 



„ „ Kephir residues 17 45 74 



As the extract affects cane sugar, it may be supposed that it contains 

 invertase as well as lactase ; there is also reason to believe that one 

 or more proteoclasts are present. 



Maltase. — The extract was prepared by merely grinding up with 

 water, in presence of toluene at about 21°, yeast which had been dried 

 as rapidly as possible — by spreading it in a thin layer on biscuit ware 

 and exposing it to the atmosphere ; the clear filtrate was used. 

 Experience seems to show that the activity of such an extract depends 

 on the temperature at which it is made and that different yeasts 

 require to be extracted at different temperatures. 



Toluene has been used as an antiseptic throughout the experiments, 

 as it was found not to influence the activity of the enzymes, whereas 

 chloroform had a distinctly retarding effect. 



Eough experiments made to ascertain the temperature at which 

 lactase exercises its maximum activity show this to be about 35° : 



* ' Chem. News,' 1902 rol. 86, p. 230. 



