1918.] AGRICULTURAL CHEMISTRY AGROTECHNY. 613 



later have been supplied with the missing food complex." Absolute proof that 

 the physiologically active dietary factor is being dealt with should include re- 

 sumption of grov^ th and maintenance of health. 



The experimental data show that the water-soluble B is not extracted di- 

 rectly from beans, wheat germ, or pig kidney by either benzene or acetone, 

 but is readily extracted by alcohol. After being removed by alcohol it is 

 soluble in benzene but very slightly soluble in acetone. That there can be 

 two or more physiologically indispensable substances in water-soluble B the 

 authors feel to be improbable in view of the solubility relations with the three 

 solvents. The water-soluble B is relatively stable toward nitrous acid (an in- 

 dication that it is neither a primary nor a secondary amin) and toward hy- 

 drochloric acid. It is rapidly destroyed by even moderately dilute alkalis, as 

 previously shown by Voegtlin and others (E. S. R., 36, p. 464). 



Effect of time of digestion on the hydrolysis of casein in the presence of 

 starch, J. S. McHaegue (U. S. Dept. Agr., Jour. Agr. Research, 12 {1918), No. 

 1, pp. 1-1). — This is a report of experiments conducted at the Kentucky Ex- 

 periment Station in duplication of the work of Hart and Sure (E. S. R.. 37, 

 p. 10) on the effect produced on the hydrolysis of casein by the presence of 

 starch by investigating the effect of varying the time of Tligestion. 



Determinations were made with casein alone and with a mixture of 10 gm. 

 of casein and 50 gm. of starch. The periods of digestion were 12, 15, 24, and 

 48 hours. The Van Slyke method was followed in detail and the results of 

 the analyses tabulated. From the data the author draws the following con- 

 clusions : 



" The Van Slyke method for protein analysis, when applied to mixtures of 

 casein and starch in the proportion of 1 : 5, and hydrolyzed from 12 to 15 hours 

 with 20 per cent hydrochloric acid gives results for the amino-acid gi'oups that 

 are comparable with those obtained by Van Slyke upon casein alone. A 

 digestion period of more than 15 hours with 20 per. cent hydrochloric acid on 

 a casein-starch mixture brings about a redistribution of the nitrogen con- 

 tained in the histidin and cystin groups. The insoluble residue obtained from 

 a casein-starch digestion after being thoroughly washed contains nitrogen, 

 which is not seriously affected when distilled with calcium-hydrate suspension, 

 very small amounts being split off as ammonia or remaining in the filtrate. 

 This indicates that the nitrogen is in an inert form and its estimation should 

 not be included in the humin determination." 



A foam inhibitor in the Van Slyke amino nitrog'en method, H. H. 

 Mitchell and H. C. Eckstein {Jour. Biol. Chem., 33 {1918), No. 3, pp. 373- 

 375). — Phenyl ether is reported by the authors to be a very effective foam 

 inhibitor in the Van Slyke nitrous acid method of determining aliphatic amino 

 nitrogen in animal and plant extracts. A convenient iJTocedure for preparing the 

 reagent at comparatively low cost is described. 



Nitrogen content of bacterial cells. — I, Method, H. C. Bradley and M. S. 

 Nichols {Jour. Biol. Chem., S3 {1918), No. 3, pp. 525-529). — An adaptation of 

 the Folin microchemical method (E. S. R., 29, p. 508) was used for determin- 

 ing the nitrogen content of Bacillus diphtlieriw and B. hoffmanni. The bacteria 

 were grown on Loeffler's blood serum medium for 72 hours. The growth was 

 then removed by a glass spade with rounded edges, transferred to tai-ed cover 

 slips, and dried in a calcium chlorid desiccator at 37° C. for 72 hours. The 

 weighing was done on an assay balance sensitive to 0.000,005 gm. The diges- 

 tion material for each tube consisted of 2 gm. potassium sulphate, 0.2 gm. cop- 

 per sulpliate, and 5 gm. concentrated sulphuric acid. The digestion was con- 

 tinued for 15 minutes after the liquid had become colorless. The digest was 

 cooled, made alkaline with sodium hydroxid, and the ammonia aspirated into 



