284 CARNEGIE INSTITUTION OF WASHINGTON. 



sequently, when the purest material had been obtained, the determina- 

 tions were repeated with equal care, giving values 5.885 and 6.081 

 respectively. Evidently indium had produced no essential effect upon 

 the expansion on freezing. Even if the more carefully prepared 

 gallium was not absolutely pure, it is evident from the outcome, by 

 extrapolation, that the purest gallium must still possess this unusual 

 property. 



Several of the investigations of previous years were prepared for 

 publication and are recorded on page 36 of this volume. 



Sherman, H. C, Columbia University, New York. Continuation of the chem- 

 ical investigation of the amylases. (For previous reports see Year Books 

 Nos. 11-16.) 



During about one-third of the time since the writing of the last 

 report, experimental work upon this research was suspended while the 

 writer, with the approval of the Institution, was engaged upon an 

 investigation of the food-supply of Russia in behalf of the War Council 

 of the American Red Cross. Early in 1918, the laboratory study of the 

 amylases and related enzymes was resumed. 



On account of the present importance of the partial substitution of 

 other grains and of potatoes for wheat in our national food economy, 

 the work of the present year is chiefly devoted to a comparative study 

 of the digestibility of wheat, maize, rice, and potato starches. The 

 experience gained during several years' study of the starch-splitting 

 enzymes is thus being brought to bear upon the present-day problem of 

 wheat saving, and the results thus far obtained are favorable to the 

 view that the starches of the principal substitutes for wheat are, 

 under comparable conditions, quite as readily digested as is the starch 

 of wheat itself. When all are purified by the same method and gela- 

 tinized by boiling with water in the same manner, wheat, maize, and 

 rice starches appear to be hydrolyzed by enzymes with practically 

 equal facility. Under the experimental conditions thus far inves- 

 tigated, this has been true whether the digestive (hydrolytic) agent 

 were saliva, pancreatin (natural mixture of pancreas enzymes), puri- 

 fied pancreatic amylase, malt extract, purified malt amylase, takadi- 

 astase, or the purified amylase of Aspergillus oryzce. With potato 

 starch the results are less regular and require further investigation. 

 The cereal starches should also be compared through a greater range 

 of experimental conditions before final conclusions are drawn. For 

 the present we propose to devote our efforts primarily to this phase 

 of the research. Such a comparative investigation of the action of 

 typical amylases and digestive secretions upon starches of different 

 origin has always been a part of our general plan of research and is 



