120 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



balsam and the cover glass pressed down over it, any excess 

 of Canada balsam exuding from the edges of the cover glass 

 being carefully wiped away with a clean rag. As soon as the 

 Canada balsam is set, the section is ready for examination 

 under the microscope. 



Before making a permanent preparation it is well to 

 examine a number of sections in order to obtain one which is 

 really characteristic. A good section will show the structure 

 of the grain as in Plate II (ii). Here a is the germ, b the 

 scutellar epithelium which divides the germ from the endosperm 

 c, while d is the husk. 



If the section of a barley grain so obtained be compared 

 with a section of undried malt, in the first place by simple 

 examination of the grain with the naked eye, it will be seen 

 that the germ has grown very considerably and that the cells of 

 the endosperm are broken down, so that the main bulk of the 

 grain is soft and friable, and it is extremely difficult to make 

 a microscopic section of it in this condition. As a matter of fact 

 the cellulose walls of the starch-containing cells have been 

 broken down in the first stage by a cellulose dissolving enzyme, 

 and afterwards the amylase has penetrated the bulk of the 

 endosperm and has largely saccharified the starch present. 



The difference in the distribution of amylase in the un- 

 malted and malted barley grain can be seen if a section 

 through the median line is treated with a small quantity of 

 guaiacum resin and hydrogen peroxide, when the blue colour 

 will be found to extend all over the grain in the case of the malt, 

 but to be only noticeable in the neighbourhood of the embryo 

 in the case of the barley. This observation suggests that the 

 seat of production of amylase is in the embryo ; this can be 

 proved by the following experiment first made by Brown and 

 Morris. 



Some starch gelatine is prepared by adding 7 grams of 

 gelatine to 100 c.c. of a 1 per cent, solution of soluble starch in 

 water, warming until the gelatine is uniformly dissolved and 



