214 THE INCOME OF EKERGY 



test-tubes, A and B. Boil the contents of tube 

 B. Place both at 37 C. At intervals- of half 

 an hour titrate a portion from 'each tube with 

 2*0 KOH solution. The acidity will diminish in 

 both, but much more rapidly in the tube contain- 

 ing the active ferment. 



The acidity is diminished by the combination 

 of the fatty acid with the glycerine to fgrm a 

 neutral fat. 1 



Fats are bydrolyzed to some extent in the stomach, 2 

 but stomach lipase is active only in neutral solutions. 

 It is inhibited or destroyed by 0.3 per cent hydro- 

 chloric acid. Other ethereal salts besides the fats are 

 hydrolyzed in the intestine, e. g. salol. 8 



The rate of change by lipase increases with the 

 amount of the enzyme present. 4 



Reversible action is seen in ferments other than 

 lipase, as in the following experiments. 



Splitting of Hippuric Acid by Histozyme. A pig's 

 kidney was perfused four hours with one litre detibri- 

 uated pig's blood to which 0.8 gram hippuric acid 



1 Hanriot : Comptes rendus de la societe de biologic, 1901, 

 p. 70. 



2 Marcet: Proceedings Royal Society, London, 1858, ix, 

 p. 306. Ogata : Archiv fur Physiologie, 1881, p. 515. Cash : 

 Arehiv fur Physiologie, 1880, p. 323.' 



3 Baas: Zeitschrift fur physiologische Chemie, 1890, xiv, 

 p. 416. 



4 Kastle and Loevenhart : loc. cit., p. 511. 



