PAT-SPLITTING ENZYMES 171 



hours and testing again with litmus the mixture will be found 

 to have become acid. 



A similar tube of butter fat incubated without the addition 

 of the pancreatic extract will be found to be unchanged. If 

 the action of the pancreatic juice is sufficiently prolonged, the 

 peculiar unpleasant smell of butyric acid can be recognised. 



In order to demonstrate the action of lipase upon a vegetable 

 fat, castor oil seeds may be made use of. Just as the barley 

 plant derives its nutriment from starch during the early 

 stages of growth, and for that purpose secretes during germina- 

 tion an amylase which hydrolyses the starch in the grain, so the 

 germ of the castor oil plant secretes a lipase which hydrolyses 

 the oil (a glyceride of ricinoleic acid) contained in its seeds. 

 To demonstrate this, therefore, castor oil seeds are allowed 

 to germinate for some days by embedding them in moist sand 

 placed in a small dish, which again can be placed in a moist 

 chamber, and the whole incubated at a moderate temperature. 

 When the seeds show signs of sprouting they may be thoroughly 

 ground up in a mortar and the enzyme investigated in one of 

 two ways. 



1. The fat may be extracted by grinding up with ether 

 and filtering, the operation being repeated several times till 

 no more fat is extracted, as can be readily ascertained by 

 evaporating a little of the ethereal solution on a watch 

 glass : when the fat extraction is complete, the ether should 

 leave no residue on evaporation. The fat may also be 

 removed by continuous extraction with ether in a Sohxlet 

 apparatus, but it is probable that an extraction at the ordinary 

 temperature gives a more active product ; in each case the 

 residue after extraction of the fat is freed from ether by 

 allowing the latter to evaporate spontaneously in the air 

 without heat. The ether-free residue contains the lipase. 



2. The germinated seeds are ground in a mortar with a 

 solution containing 5 per cent, of sodium chloride and 0'2 per 

 cent, potassium cyanide, which is allowed to stand in contact 



