FOODS HUMAN NUTRITION. 859 



erties of these enzyms and their relations to the conditions prevailing during 

 the processes of digestion. 



Trypsin may be presei'ved for a considerable length of time at 38° C. by salts 

 of the alkaline earth metals, particularly those of calcium. In weakly alkaline 

 solution (sodium carbonate 0.16 normal) trypsin is readily destroyed, but in the 

 presence of free acid (hydrochloric acid 0.025 normal) a small amount of 

 trypsin remains undestroyed even after boiling for five minutes. Albumin, 

 I^eptone. and amino acids protect ti-ypsin against heat destruction, albumin being 

 most effective in this respect. 



Trypsinogen is preserved indefinitely at room temperature in the presence of 

 O.IG normal soilium carbonate solutions, though it is destroyed by heating in this 

 medium to 65° for five minutes. After heating to 100° for five minutes in the 

 presence of hydrochloric acid (0.025 normal) over 30 per cent remains unde- 

 stroyed. Neutral salts raise the heat of destruction in varying degrees. 



Enterokinase Is immediately destroyed by free hydrochloric acid (0.01 nor- 

 mal) at 16°. The presence of calcium chlorid (0.5 normal) increases the heat 

 destruction temperature to 75°. 



" Enterokinase and trypsin are destroyed by the hydrochloric acid of gastric 

 juice, but trypsinogen is not acted upon. Trypsinogen is destroyed by i>epsin 

 and hydrochloric acid. Trypsin has no effect on enterokinase or trypsinogen. 

 Enterokinase has no effect on trypsin, but activates trypsinogen. Pepsin is de- 

 stroyed by the alkali of pancreatic juice." 



The ferments of the pancreas. — IV, Steapsin, J. Mellanby and V. J. Wooi> 

 LEY (Jour. Physiol, 48 {1914), ^o. /,. pp. 281-302). — Continuing the above work, 

 the authors report experimental data which may be summarized as follows : 



" The stability of steapsin in alkaline solution is similar to that of trypsin." 

 The loss of steapsin by fresh pancreatic juice increases rapidly with an in- 

 crease in temperature above 40° C, all of it being destroyed within five 

 minutes at 60°. 



The stability of steapsin in acid solution depends upon the concentration of 

 hydrogen ions in the solution, it being stable in the presence of large amounts 

 of higher fatty acids but quickly destroyed by small amounts of free mineral 

 acids. 



" Steapsin can not exist in the presence of free trypsin. Therefore, when 

 pancreatic juice is activated by enterokinase, as trypsin develops steapsin 

 disappears. This fact affords an explanation for the presence of trypsinogen 

 rather than trypsin in fresh pancreatic juice." 



Steapsin is protected from destruction by the addition to activating pan- 

 creatic juice of serum or egg albumin. 



"The action of steapsin on fat is greatly augmented by bile and bile salts. 

 Electrolytes, such as neutral salts, have no influence on the reaction . . . 



" From a consideration of the properties of steapsin and its relation to 

 trypsin it appears that steapsin consists essentially of protein ; that the de- 

 struction of trypsin in alkaline solution is not due to autodigestion but to its 

 inherent instability ; that although the conditions in the small intestine which 

 favor trypsin production are inimical to the continued existence of steapsin, yet 

 the presence of protein in a dietary may facilitate fat digestion by virtue of the 

 capacity of the protein to absorb the first formed trypsin." 



The influence of sugar injections on heat regulation, H. Freund and E. 

 ScHLAGiNTWEiT {Avch. Expt. Path. u. Pharmakol., 76 (1914), No. 5-6, pp. 303- 

 310; abs. in Zentbl. Physiol., 29 {1914), No. 2, p. 94).— The authors conclude 

 from experimental data that the nervous systems for heat regulation and for 

 sugar combustion are entirely independent. 



