THE DIGESTIVE ENZYMES OF LEPIDOPTERA. 345 



We may therefore infer, that there exist enzymes in the 

 intestines which act upon albumin, but that amylolytic and 

 h'patic enzymes are completely absent. Plateau s opinion that 

 there are no enzymes in the intestines, seems to be erroneous. 



As regards the products of digestion I have made tests 

 with the enzyme precipitates obtained from the stomach of the 

 silk-worm and of Caligula japonica. These precipitates were 

 dissolved in a 1 % solution of sodium carbonate (cryst). Some 

 fresh egg-albumen served for the test with the enzyme from 

 the silk-worm (a), while coagulated albumen was used with 

 that from Caligula japonica (b). After the addition of some 

 crystals of thymol the mixtures were kept at 36 0 C. for eighteen 

 days. Putrefaction had been successfully prevented by the 

 presence of the thymol. There was still some unchanged 

 albumen present, as the test with nitric acid showed. The 

 undigested albumen was removed from (a) by lead acetate 

 according to Hammer steri s method, 1 and after freeing the filtrate 

 from lead by H 2 S, it was neutralized with NH 3 and evaporated. 

 The residue thus obtained was extracted with boiling alcohol, 

 but no crystals of leucin or tyrosin could be observed on 

 slow evaporation of this extract. The part insoluble in alcohol 

 gave no indication of tyrosin crystals on slow evaporation of 

 its solution ; it consisted of a syrupy mass that behaved towards 

 the usual reagents in every respect like peptone. The test 

 for tryptophan was, like that for leucin and tyrosin, ineffectual ; 

 a solution of chloride of lime failed to give the purple-red 

 color. 2 Tryptophan is a characteristic product of the tryptic 

 digestion and according to Neumeister the formation of leucin 

 and tyrosin can directly be inferred, when the reaction for 

 tryptophan gives a positive result. 



We observe therefore that the end-products of digestion 

 were peptones, but no further decomposition products. Hence, 

 the proteolytic enzyme of the stomach of Lepidoptera is different 

 from the pepsin as well as from the trypsin of Vertebrata ; it agrees 

 with the pepsin in so far as it produces as end-products of digestion 

 peptones, but differs from it as to the reaction of the active 

 solution ; and on the other hand, while it agrees with the trypsin 



Physio. Chem. S. 175. 



The same results were obtained from (b) after it had stood seven days at 36 0 C. 



