Feb. 2,1924 
Digestibility of Tested Grain Hulls 
253 
and in addition the percentage of starch was determined in the hulls, and 
pentosans and lignin in all the feeds and solid excreta. Pentosans were 
determined according to the official method as described in the manual 
of the Association of Official Agricultural Chemists. 8 
Starch was determined by pancreatin in the following manner: 
Two grams of finely ground (100-mesh) material were transferred to a hardened filter 
paper and washed with several portions of hot 10 per cent ethyl alcohol to remove 
the sugars. The residue was immediately transferred by means of a stemless funnel 
and a minimum of water from a wash bottle to a 250 cc. volumetric flask. The 
suspension, if not already diluted sufficiently by the water used for transferring, 
was further diluted to about 100 cc. and boiled for half an hour to rupture the cell 
walls and the starch granules and liberate the starch. The flask was then filled 
almost to the mark with distilled water and allowed to cool to below 37 0 C. A pinch 
of sodium bicarbonate was then added to insure slight alkalinity for optimum action 
of the pancreatin, followed by one-tenth of a gram of full-strength pancreatin. 9 The 
solution was at once made up to the mark, shaken well, and placed in a water bath 
at 37 0 to 40° C. for half an hour, at the end of which time the contents of the flask 
were emptied into a 500 cc. beaker to facilitate subsequent pipetting; 200 cc. of 
the liquid were immediately pipetted off into another 500 cc. beaker as rapidly as 
possible, and 20 cc. of HC 1 (sp. gr. 1.125) added at once, thus inactivating the pan¬ 
creatin. The 220 cc. of liquid were then filtered by suction into another 250 cc. 
flask, using a platinum cone to support the filter paper, and a bell jar of suitable 
size on a ground glass plate to hold the flask into which the filtrate passed. As soon 
as possible after filtration was complete, the flask was placed under a reflux condenser 
and heated gently for two hours, the solution cooled, nearly neutralized with NaOH, 
and made up to 250 cc. With some materials another filtration was necessary at 
this point, but suction was not required. Reducing sugar was determined in aliquots 
of the solution by Allihn's modification of Fehling’s method. 10 
Lignin was determined by a modification of the method of Ost and 
Wilkening (reported by Cross and Bevan, 8, p. 39), which was proposed 
by Mahood and Cable (31) . The principle of the method consists in the 
hydrolysis of all the constituents of the material except the lignin by 
means of concentrated sulphuric acid. The dissolved substances are 
removed by filtration and washing and the residue is dried and weighed 
as lignin. The details are as follows: 
Two * 11 grams of the material were extracted with ether in an ordinary fat extraction 
apparatus, transferred to a 1,000 cc. Erlenmeyer flask and covered with 10 times its 
weight (13 cc.) of 72 per cent sulphuric acid. Considerable care and some practice 
were necessary at this point in order to get all particles of the dry material in contact 
with the relatively small amount of acid. The hydrolysis was allowed to proceed 
for 16 hours at room temperature, at the end of which time the solution was diluted 
with ordinary tap water to a strength of 3 per cent (480 cc. of water was the amount 
necessary for that degree of dilution). The solution was then boiled under a reflux 
condenser for 2 hours, filtered through linen, washed with hot water, transferred to 
a tared Gooch crucible, dried at ioo° C., weighed, ignited, and weighed again. The 
loss in weight was considered as lignin. 
Some preliminary work was done in determining lignin by the method 
of Willstatter (reported by Magnus, jo, p. 14 ), in which 42 percent 
hydrochloric acid is used as the hydrolyzing agent, instead of sulphuric 
acid. This method proved less satisfactory because of the cost of HC 1 
so highly concentrated, the difficulty of keeping it at that strength, and 
the extreme unpleasantness of the dense fumes given off. 
8 OP. CIT., p . q6. 
9 This material was furnished to us through the courtesy of Parke, Davis & Co., of Detroit, Mich., and, 
unlike the ordinary reagent, contained no diluent. 
10 Association of Official Agricultural Chemists, op. cit., p. go. 
11 Mahood and Cable ( 31 ) use 4 gm., but half that quantity was better adapted to our purposes. 
