444 SCIENCE PROGRESS 



or by some gastric extract, of some of the products hitherto 

 attributed to trypsin. Malfatti has drawn attention to the 

 frequent appearance of tryptophane among the products of a 

 peptic digestion, and has sought to separate pepsin into two 

 enzymes of the two classes we have under consideration. 

 Failing to do so, he has felt drawn to a view long ago stated 

 by Hoppe-Seyler, that pepsin has peptoclastic powers as well 

 as trypsin, an opinion, however, which is opposed by the fact 

 that a very intense peptic digestion is possible without any 

 appearance of tryptophane. 



Glaessner claims to have detected an enzyme existing in 

 the stomach side by side with pepsin, which possesses 

 proteoclastic power in a neutral or faintly alkaline medium, as 

 well as in an acid one. He has named it pseudopepsin, and 

 says it is yielded mainly by the pyloric mucous membrane 

 during autodigestion. He adds that it produces tryptophane 

 in the course of its activity, and thereby he distinguishes it 

 from pepsin. 



Glaessner's conclusions are disputed by Klug, who failed 

 to find any evidence of the existence of pseudopepsin. 



Other authors, however, have obtained results which confirm 

 Glaessner to some extent, inasmuch as they find tryptophane can 

 be produced by the action of gastric preparations. Pekelharing 

 describes some experiments made upon a juice extracted by 

 Buchner's pressure method from the pyloric mucous membrane, 

 which, after being freed from ordinary pepsin, was found to have 

 proteoclastic powers in neutral and faintly alkaline media, and 

 to form tryptophane. It was, however, very feeble. Pekelharing 

 found it in the stomach of the pig and in the gastric juice 

 of the dog. He adds, however, that unaltered gastric juice 

 working in an acid medium will give rise to tryptophane after 

 several days' action, and says that his researches lead him to 

 the opinion that this is a property of all pepsin, even when 

 purified by means of acetate of lead and oxalic acid, provided 

 that the solution is sufficiently concentrated, and that too 

 much hydrochloric acid is not present. With not very strong 

 pepsin solutions the acid must not exceed o*2 or even o - i per cent. 



Admitting that pseudopepsin may exist in small quantity 

 side by side with pepsin in the stomach of the dog, Pekelharing 

 is not inclined to admit that it is a secretion of the gastric glands, 

 but suggests that it is to be regarded as an autolytic enzyme in 



