Some Human Digestion Experiments. 119 



concentrated hydrochloric acid diluted with an equal volume of 

 water is added from a burette until precipitation is complete, 

 carefully avoiding an excess. If the nucleic acid does not flock 

 out after the solution has been quiescent for several minutes, the 

 same process should be repeated upon another aliquot after first 

 adding 5 per cent, of magnesium sulphate (MgS0 4 .7H 2 0). Mag- 

 nesium sulphate renders nucleic acid more insoluble. A pro- 

 portionate quantity is then added to the bulk of the solution. 

 The nucleic acid, which forms large flocks and slowly settles, is 

 washed successively with 60, 80, and twice with 95 per cent, 

 alcohol by decantation, filtered on hardened filter paper, washed 

 again with 95 per cent, alcohol and finally with ether and then 

 rapidly dried at about 70 0 C. 



The yields from different glandular tissues vary from 0.8 per 

 cent, to 1.5 per cent. 



67 (1527) 



Some human digestion experiments on raw white of egg. 



By Mary Swartz Rose and Grace MacLeod. 



[From the Department of Nutrition, Teachers College, Columbia 



University.] 



Experiments to determine the relative digestibility of raw and 

 cooked white of egg in the human subject were carried out with 

 four young women students in two periods of five days each. 

 As they all had practically the same food requirements, they took 

 the same diet, quantitatively and qualitatively, throughout the 

 experiment, the only variation being the change from raw whites 

 to cooked whites for half the time, and some differences in the 

 ways in which the whites were prepared. The egg whites fur- 

 nished 48 grams of protein per capita per day out of a total of 

 67. grams. Besides the eggs the diet consisted of rice, cream, 

 saltines, butter, olive oil, fruit juice and a small amount of lettuce. 

 The cooked eggs were never subjected to a temperature or method 

 of cooking which would toughen them unduly; the raw whites 

 were taken unbeaten by one person, all beaten light by another, 

 and about half and half by the other subjects. 



The coefficients of digestibility for the two diets have been 

 calculated for the total protein and for the egg white protein alone. 



