504 EXPERIMENT STATION RECORD. [Vol.40 



carbohydrate silage, indicating that the carbohydrate serves as a protein 

 sparer. The theory is advanced that proteolytic action, which is responsible 

 for the offensive odors characteristic of the alfalfa silage, results, in part at 

 least, from the ability of tbe acid producers to utilize protein as a source of 

 energy in tbe absence of available carbohydrates, 



Studies on pepsin. — I, Chemical changes in the purification of pepsin, 

 L. Davis and II. M. Mebkeb (Jour. Amer. Chem. Soc., $1 (1919), Ifo. 2. pp. 

 121-228). — The literature on the chemical composition of pepsin is reviewed, 

 and an investigation is reported of the changes taking place in the purification 

 of pepsin with the view of throwing light on its chemical composition. Chemi- 

 cal analyses were made of samples of pepsin of proteolytic strength of 1:2,000 

 up to 1 : 40.000, the results of which are summarized as follows: 



"The purification of pepsin seems to consist in tbe elimination of secondary 

 protein derivatives including a-amlno acids. Calcium and sulphur appear to 

 be unaltered as a result of purification, but phosphorus is materially reduced. 

 Chlorids an' seemingly entirely removed. Aqueous solutions of pepsin, after 

 purification, show no material change in optical activity. A sample of high 

 digestive power (1: 40,000) shows a reaction very nearly neutral. Fepsin tends 

 to approach nearer to tbe actual character of a protein (possibly a glycopro- 

 tein) with increasing proteolytic activity." 



Influence of hydrogen-ion concentration upon enzymic activity of three 

 typical amylases, II. < '. Siikkm an. A. \V. Thomas, and M. E. Baldwin {Join 

 Amu: Chew. Soc.', .',1 {1919), A"". 2. pp. 181 285, fig- J).— In continuation of In- 

 vestigations on amylases and related enzyms (E. S. R., R'.t. p. 069), determina- 

 tions are reported of tbe H-ion concentration which Induces optimum activity 

 of pancreatic and malt amylases and that "f Aspergillus oryza (prepared from 

 taka diastase), and of the limits of H-ion concentration within winch any 

 enzymatic activity is Shown. Tbe H-ion concentration was determined by the 

 use of tbe Clark cell and rocking electrode. 



Pancreatic amylase was found to lie active between the limits of pH 4 to 10 

 with optimum activity at about 7, tbe solutions commonly considered neutral 

 Sbowing under similar conditions a pH value "f 5.8. Malt amylase was active 

 between pH 2.5 and 9, with optimum activity at 4.4 to 4A Tim amylase of 

 A. oryza was active from pH 2.6 to 8, with optimum activity at about 4>. 



The activities of the three amylases throughout the range of II ion concen- 

 tration in Which activity was found are summarized by means of curves. The 

 influence Of concentration Of electrolyte, as distinguished from concentration 

 of II ion alone, appeared greatest In the case of pancreatic amylase and least 

 In the case of the amylase of A. oryz<B. 



The effect of neutral salts upon the activity of ptyalin. B. W. ROGKWOOD 

 (Jour. Amer. chnu. 8oc., ',1 {1919), Xo. 2, pp. 228 280). in continuation of 

 work previously noted (E. S. K.. 37. p. 204) on auxo amylases or activators of 

 amylolytic enzyms, a study is reported of the effect of small amounts of am- 

 monium and other neutral stilts upon the activity of ptyalin. 



Variations in ptyalin activity in tbe presence of these Baits were found to 

 be a function of the anion. The effect was greatest with chlorids, hromids. and 



nitrates; considerable with sulphates and thiocyanates ; and slight with 

 fluorids, acetates, and tartrates. The nature and valence of the cation ap- 

 peared to have 00 effect. 'As a possible reason for tbe variations produced by 

 the anion, a colloidal change in either the starch or the albumin of tbe saliva 

 or In both is suggested. 



The preparation of metol (N-methyl-p-amidophenol sulphate), U. N. 

 IIaki.kk (Jour. Amer. Chem. Soc, }/ (7."/.'m. No. 2, pp. 270-276), 



