THE DIGESTIVE ENZYMES OF LEPIDOPTER A. 339 



Some general knowledge of the digestive enzymes of insects 

 may be obtained from the investigations mentioned, but as 

 there exist among insects both herbivora and carnivora, the 

 character of the digestive enzymes may also be different. Further, 

 since the investigations of Krukenberg and others hitherto made 

 have related chiefly to proteolytic enzymes and not to amy- 

 lolytic and lipatic enzymes, some further questions remain to be 

 solved. 



The author has, therefore, undertaken to investigate the 

 digestive enzymes of Lepidoptera, especially those of the silk- 

 worm. 



The insects used in the first experiment were the living 

 larvae of Dasychira lumulata Butl. 



They were dissected, and the expanded part of the digestive 

 canal (stomach) was taken out, and freed from its contents by 

 washing it in water, and 3 grs. of these stomachs were triturated in 

 a mortar with the addition of powdered glass. The crushed mass 

 was divided into two parts. One part was digested with 15 grms. 

 of glycerin containing \0% of water, while the other part was 

 made faintly acid with dilute acetic acid, according to the 

 tiypsin-extraction method of Heideiihain^ and exposed to the 

 air for a short time, whereupon it was digested with glycerin 

 like the other part. To furnish a control case for the method of 

 extracting enzymes, the stomach and intestines of a snake were 

 treated in the same manner as those of the insects. After three 

 days the glycerin extract prepared without the acid treatment 

 was filtered. To the filtrate strong alcohol was added till a 

 precipitate was produced. The precipitate was collected on a 

 filter, dissolved in water, filtered and again precipitated. But 

 this precipitate was too insignificant to be separated again from 

 the filter. It was, therefore, exposed to the air on the filter, 

 and after the evaporation of the alcohol, the whole was divided 

 into two parts. One part was dissolved in about 20 c.c. of water 

 containing o.\% of HC1, and the other in 20 c.c. of 0.3% 

 solution of sodium carbonate, since, according to Hammarsten,'* 

 trypsin acts best in a fluid containing 0.3 — 0.4% of sodium 

 carbonate. The extract of the stomach of the snake was treated 



1 Hammarsten. Lehrbuch der Physiologischen Chemie. S. 171. 

 ^ Ibid, S. 172. 



