Feb. 23, 1924 
Utilization of Lactose by the Chicken 
599 
The procedure adopted for the extraction of the reducing substances 
in the excreta was as follows: The total excreta of each hen for the period 
of the experiment were extracted by pouring 200 to 500 cc. portions of 
hot water over the excreta in a large evaporating dish, macerating 
thoroughly with a pestle, and filtering through cloth. The residue in 
the cloth was returned to the dish and extracted again. When the total 
volume of the washings measured 4,000 cc., the extraction was con¬ 
sidered complete. An extract of this volume was previously shown to be 
sufficient by mixing 25 gm. of lactose and 25 gm. of glucose with a seven- 
day collection of excreta and extracting with 200 to 500 cc. portions of 
hot water until the last extract failed to give a carbohydrate test with 
Fehling’s solution. The reducing substances in the total excreta for the 
period of the experiment were estimated by determining the reducing 
substances, calculated as lactose, C 12 H 22 O u , in aliquots of the thoroughly 
mixed extract. 
Two methods were used throughout for the determination of reducing 
substances. The first was the combination of the Munson and Walker 
and the Bertrand (2) methods, as described by Mathews (4, p. 994 ), for 
the quantitative determination of reducing sugars in urine and other 
fluids, and the second was Benedict’s (1) method for the estimation of 
glucose in urine. The first is a method of the Association of Official 
Agricultural Chemists 4 for the determination of reducing sugars in 
foods and feeding stuffs and has been found in this laboratory to be 
rapid and accurate. This method, however, has the disadvantage that 
substances other than sugars, uric acid in particular, are capable of 
effecting reduction of the alkaline cupric tartrate and hence, if present, 
would be calculated as lactose. Uric acid would, of course, be present 
in considerable quantities in hot aqueous extracts of chicken excreta. 
However, since the quantity of uric acid excreted daily from a diet in 
which only the amount of lactose varied would probably change but 
slightly, it was thought that the variation in quantity of reducing sugars 
present could be estimated without the previous removal of uric acid. 
On the other hand, the Benedict method is not appreciably affected by 
the presence of uric acid. Tests designed to show the effect of uric 
acid and to determine the applicability of the combined Munson-Walker- 
Bertrand and the Benedict methods to aqueous extracts of chicken 
excreta containing a constant amount of uric acid and varying amounts 
of lactose were conducted. 
First, the effect of uric acid on the determination of lactose in milk 
by each of the two methods was tested. Lactose was determined in a 
sample of separated milk by the two methods in the usual manner. 
Then, uric acid, varying from 0.01 gm. to 1 gm. was added to 25 cc. 
portions of the sample and the lactose was determined by the combined 
Munson-Walker-Bertrand and by the Benedict methods in the usual 
manner with the following averaged results. 
4 Association of Official Agricultural Chemists, official and tentative methods of analysis. 
As compiled by the Committee on Revision of Methods. Revised to November i, 1919. 417 p., 18 fig. 
Washington, D. C. 1920. Bibliographies at ends of chapters. 
