188 



SCIENCE 



[N. S. Vol. XXXVII. No. 944 



son indicates that laetalbumin yields much 

 more tryptophane than edestin, and that 

 edestin yields somewhat more than casein or 

 gliadin, which give reactions of about equal 

 intensity. 



We have made some preliminary experi- 

 ments to determine the effect of replacing a 

 part of the zein with other proteins, but these 

 have not been continued long enough to give 

 final conclusions. The three upper curves 

 show that when one third of the zein is re- 

 placed by casein, edestin or gliadin the rat 

 rapidly loses weight. The fall is less rapid 

 and less extensive when one third of the zein 

 is replaced by edestin than when it is replaced 

 by casein. 



Chart I., rat 634, shows that when one 

 fourth of the zein is replaced by laetalbumin, 

 weight is regained. Unfortunately this ex- 

 periment was terminated by death from dis- 

 eased lungs. 



Chart III. shows that rat 633 regained its 

 lost weight very rapidly when one half or one 



So far as these results go they agree with the 

 relative intensity of the glyoxylic acid reaction 

 for tryptophane. 



Chart IV. shows complete recovery of lost 

 weight when one half of the zein was replaced 

 by casein, and rapid decline when the propor- 

 tion of casein was reduced to one sixth. This 

 decline was at once stopped when tryptophane 

 was added to the food, the proportion of zein 

 and casein remaining the same. The last 

 period of this experiment was unsatisfactory 

 as the rat soon after died with diseased lungs 

 and kidneys. If disease had not intervened it 

 is not improbable that the lost weight would 

 have been fully regained in period 4. 



Chart V. shows a rapid loss of weight when 

 zein formed the sole protein of the diet, and 

 complete recovery when one half of the zein 

 was replaced by casein. After being again 

 reduced on the zein diet, a partial recovery 

 was made when one half of the zein was re- 

 placed by edestin, and a nearly complete re- 

 covery, when all was replaced by edestin. 



J3aA|S 



JDa^s 



quarter of the zein was replaced by laetal- 

 bumin. Eat 487 regained its loss more slowly 

 with one half edestin. Eat 644 was main- 

 tained by one half gliadin, and declined rapidly 

 and died when changed to a diet containing 

 one half zein and one half gelatin, a protein 

 which like zein lacks tryptophane. 



It is difficult to understand why diets con- 

 taining two thirds zein and one third casein 

 or edestin are so inferior to those containing 

 one half of either of these proteins. It may be 

 that experiments now in progress will not con- 

 firm these preliminary results, but it is also 

 possible that we shall find that a certain min- 



