FUNCTION OF THE (ENOCYTES OF INSECTS. 2IQ 



degree than any of the other organs or tissues. I was unable to 

 classify these oxidizing enzymes any further and am unable to 

 say whether they are oxydases or katalases. A very delicate 

 method had to be devised, for one must bear in mind that the 

 amount of cenocyte extract which can be obtained even from 

 a large number of larvae is very small. I have already called 

 attention to the fact that the oenocytes are very large in Zeu- 

 zera pyrina when compared with those of other forms, yet this 

 statement is merely relative and it must be remembered that 

 from the point of view of the physiological chemist they are 

 really minute organs. 



The pancreatic extract of the hog was again used and the 

 amounts of the extract and reagents were again decreased in 

 order to train the eye as before to light reactions. Training 

 the eye was hardly necessary in either case. The reaction 'for 

 lipase was decidedly negative while the reaction for oxidizing 

 ferments was decidedly positive. It was thought safer, how- 

 ever, to take these precautions. 



It might be well here to say something concerning the reagent, 

 which was that employed by clinical workers for the demonstra- 

 tion of occult blood. This reagent consists of: 100 c.c. of a 20 

 per cent, solution of NaOH + 2 grs. phenolphthal^'w + 10 grs. 

 zinc dust. This is boiled slowly till the solution is decolorized. 

 The fluid is then filtered while still hot into a colored bottle 

 under white petroleum oil. Great care must be exercised to 

 keep out the oxygen of the air, or it will color. 



In the experiments one half the quantity of reagent was added 

 to double the quantity of pancreatic extract and a drop or two 

 of a 3 per cent, solution of hydrogen peroxide was added to this. 

 Owing to the fact that oxidizing enyzmes are present in the 

 pancreas, the solution strikes a red color. As control tests 

 water was used instead of extract and treated in the same way. 

 No attention was paid to change of color which develops on 

 prolonged standing. A layer of petroleum was always kept 

 above the specimens to exclude the air. 



It was found that the above reagent was satisfactory only so 

 long as a considerable amount of extract was used. When I 

 came down to using very small amounts, e. g., one or two drops, 



