448 Dr. R. D. Thomson [June 



the microscope, the rays of light are strongly deviated at 

 their entry and departure, so that only those reach the 

 eye which pass through the interior of the globule, and 

 hence, they appear as black balls with a white nucleus. 

 They consist of vesicles, filled with a gummy matter, which 

 hardens in contact with air. In water of the temperature 

 122° the bladder is expanded, probably by the increase in 

 volume of the gum. In boiling water it is ruptured and 

 precipitated, while the gum (the dextrine of Biot) dissolves 

 in the water. Iodine colours the grains, not by combining 

 with them, but by merely attaching itself to the exterior of 

 the visicles. The form of the grain is not altered ; for, if 

 inorganic salts capable of combining with the iodine, and 

 forming hydriodates, are mixed with the starch, the colour 

 disappears, and the starch remains colourless. # 



The nature of the diatase which Payen and Persoz have 

 found in starch, Raspail explains in this way : In the act of 

 germination the grains of which starch consists increase by 

 successive layers, beginning nearest the cotyledon, while at 

 the same time acetic acid is formed ; now this acid dissolves 

 gluten, and renders it equally soluble in water and alcohol. 

 If the flour of germinating barley be macerated for an hour 

 in pure water, the water will dissolve the gum, sugar, and 

 gluten combined with the acetic acid. When exposed to 

 heat a flocky precipitate will be produced by the disen- 

 gagement of a portion of the acetic acid by heat, or of its 

 saturation by some base, disengaged from the tissue by the 

 temperature. Alcohol will increase the quantity of the 

 precipitate. Raspail digested for a few minutes some wheat 

 flour in acetic acid, at first concentrated, and then diluted 

 with a hundred times its weight in water. It was filtered, 

 and the liquid poured into a solution of starch. A precipi- 

 tation of the tegumentary matter immediately ensued. 



These facts are extremely important when considered in 

 connexion with the process of malting, because they exhibit 

 in a powerful manner the greatness of the change which is 

 produced by the slightest effort of Nature's operations, and 

 because they enable us to comprehend more readily the 

 variety of alterations which the elements of grain undergo 

 in the same process. 



* Nouveau Systeme de Chimie organique fond6 sur dea methodes nouvelles 

 d'observation par F. V. Raspail, 8vo. 1833, p. 8, 562. 



