THE DIGESTIVE ENZYMES OF I.EPIDOPTER A. 34 1 



Solutions. 



Materials 

 used. 



Temperature. 



Intervals. 



Results. 



Alkaline solution of 

 the enzymes of the 

 insect-stomach. 



» 







dissolved, and 

 produced biuret 

 reaction. 







36°C 



2 days. 







starch. 



room- 

 temperature. 



3 hours. 



starch 

 completely 

 disappeared. 



The acid extract of the insect-stomach and that of the 

 snake-intestines were examined in just the same way as the 

 former. The results were the same as those obtained with 

 the insect-stomach. I therefore infer : 



I. That the enzymes of Lepidoptera act only in an alkaline, 

 and not in an acid solution. 

 II. That in the digestive organs of Lepidoptera tryptic 

 enzyme is present, while pepsin is absent. 



Since, however, it might be objected that there was present 

 pepsinogen, which failed to be converted by the highly diluted 

 acetic acid into the active state, a second experiment was made, 

 and this time with old silk-worms. 16 grs of stomachs and 

 3 grs of intestines were obtained from silk-worms in the same 

 manner as in the former case, and these were divided into 

 two portions. After adding to one part some HCl of o.\% 

 (according to Podzvysozki 1 pepsinogen is easily transformed 

 into pepsin by HCl), both portions were crushed as above and 

 digested with glycerin as above. After three clays it was 

 filtered, and to the filtrate strong alcohol was added. The 

 precipitate was collected on a filter, dried and divided into two 

 parts. Since according to King, 2 pepsin acts best in a solution 

 containing 0.5—0.6,% of HCl, and according to Ewald 3 trypsin 

 acts also in a solution containing 0.3% of HCl, one part was dis- 

 solved in about 30 c.c. 0(0.4% HCl, and the other in about 40 c.c. 

 °f °-3% solution of sodium carbonate. Both solutions were 



1 Neumeister. Lehrbuch der Physiologischen Chemie. S. 178. 



2 Oppenheimer. Fermente und ihre Wirkungen. S. 100. 



3 Ibid. S. 113. 



