58 LAWRENCE T. FAIRHALL AND PAUL M. BATES 



the amount of energy applied. The following study shows that 

 lipases suspended in oil are greatly weakened, if not destroyed, 

 by exposure to ultra violet rays. 



To obtain a suspension of lipolytic enzymes in oil, 0.5 gram 

 of pancreas extract (Fairchild Bros. & Foster) was emulsified in 

 500 cc. of dried and filtered cotton seed oil. Portions of this 

 emulsion were exposed at a distance of 5 cm. from the quartz 

 mercury vapor lamp for different lengths of time. The tem- 

 perature was kept below 40° by exposing the emulsion in thin 

 layers in open dishes floated on ice water. 10 cc. of the emulsion 

 so exposed were emulsified with 10 cc. of distilled water and 

 incubated at 37° for eighteen hours. No great increase in 

 acidity was observed in samples so incubated over those incu- 

 bated for a few hours only. After incubation the samples of 

 emulsion were titrated with N/100 sodium hydroxide, using 

 phenolphthalein as an indicator. 



Similar experiments were made using a fresh suspension of the 

 pancreatic extract, but flowing the suspension around the lamp 

 by means of the quartz spiral and at the same time chilling the 

 oil. Small quantities could thus be handled at a speed allowing 

 an exposure of one minute. By returning the oily suspension 

 through the spiral, exposures of from one to ten minutes could 

 be made with the one sample. Portions were drawn off for each 

 minute of exposure, emulsified with 10 cc. of distilled water and 

 incubated for eighteen hours at 37° in flat dishes. The purpose 

 of this technique was to insure as large a surface of contact be- 

 tween the oil suspension and the water as possible. After incu- 

 bation, the dishes were washed out with water and the emulsion 

 titrated as before. The results are collected in the tables below 

 and shown graphically in figure 2. 



The variation between the values for the incubated lipase 

 suspensions may perhaps be due to variation in the enzyme con- 

 tent of different portions of the pancreatic extract. In any case, 

 however, these values indicate that the lipolytic action of the 

 enzyme is weakened or inhibited by the action of the ultra 

 violet rays and that the greatest change in the enzyme occurs 

 within the first few minutes of exposure, i.e., during the period 



