296 PHYSIOLOGY OF NUTRITION. 



colour 011 addition of a trace of alcoholic Iodine solution. After 

 a few minutes the fluid containing the starch and diastase has 

 become clear, but a sample of it still gives a blue coloration on 

 addition of Iodine. If we wait for some time, a sample of the 

 fluid assumes a violet coloration with Iodine. A sample taken 

 still later becomes brown on addition of Iodine, and finally (per- 

 haps after two or three hours) Iodine no longer produces a marked 

 coloration in a sample of our fluid. Under the influence of dias- 

 tase the amylum. as is known splits up into a series of related 

 dextrins and sugar (maltose). These dextrins do not all assume 

 the same colour on addition of Iodine, and thus the Iodine reac- 

 tion affords a very convenient means of following accurately the 

 transformation under the influence of diastase. To determine 

 with certainty the diastatic action of a plant extract, especially if 

 the quantity of ferment is inconsiderable, it is necessary for rea- 

 sons given by Wortmann, in his treatise cited below, not to add the 

 Iodine till the mixture of plant extract and starch paste has been 

 boiled and completely cooled again. If then no blue coloration 

 is found, starch is certainly no longer present. The formation of 

 sugar may also be easily demonstrated. We determine by means 

 of Fehling's solution the amount of sugar present in 5 c.c. of malt 

 extract (see 115), treat 25 c.c. of starch paste with o c.c. of malt 

 extract, and after a few hours estimate the amount of sugar in the 

 fluid. It is found to contain far more sugar than did the 5 c.c. of 

 malt extract. 



If a not too small quantity of malt extract, made as strong as 

 possible, is treated with a large excess of absolute alcohol, a volu- 

 minous precipitate is thrown down. We collect this on a filter, 

 wash it with alcohol, and dry the residue in the air. It consists 

 of a number of different substances, and among them the diastase 

 precipitated by the alcohol. If we dissolve a small quantity of 

 the dry mass in water, we shall obtain a fluid which transforms 

 starch very energetically. 



It is of interest to make a few experiments to show that not 

 only barley seedlings, but other seedlings also, and leaves and 

 stems of different plants contain diastase. I have, e.g., experi- 

 mented with wheat seedlings a few days old, and pea seedlings ten 

 days old (the seedlings had developed in darkness), and also with 

 leaves of Sedum maximum and stems of Impatiens Balsamina. 

 The material was pounded in a mortar, flooded with a little water, 

 and after some time filtered. The solutions obtained transformed 



