THE INTESTINAL ENZYMES. 341 



extractives concentrated solutions of different salts. He found that some salt 

 solutions extracted all three ferments, while others especially extracted one 

 ferment accompanied by traces of the others. Thus sodium chloride, sodium 

 sulphate, and potassium chlorate extracted all three ferments indifferently; 

 sodium bicarbonate, with a little of the normal carbonate added, extracted best 

 the fat-splitting ferment ; the proteolytic ferment was taken up best by 

 potassium iodide, arsenite, or sulphite ; and the diastatic ferment by 

 potassium arsenate alone or with the addition of ammonia. 



Dastre l has recently described methods for approximately separating the 

 proteolytic and diastatic enzymes of the pancreas. 



1. If the pancreas of an animal killed during digestion be cut into large 

 pieces, and these then digested for 15-20 minutes at 40 C., in normal saline 

 (*7 per cent.), the filtrate is found to possess a strong diastatic action, but 

 scarcely any proteolytic action. If, after this first extraction, the pieces are 

 finely minced and extracted anew with normal saline (1 per cent, of sodium 

 fluoride being added to prevent putrefaction), an extract is obtained rich 

 in proteolytic ferment, but containing scarcely any diastase. 



2. On extracting a fresh gland with alcohol of increasing strength, after- 

 wards with ether, and drying over sulphuric acid, a powder is obtained 

 which yields, on extraction with saline, a fluid which is almost inert towards 

 starch, but is actively proteolytic. 



3. An extract made from the pancreas of an animal which has not been fed 

 for some days, contains proteolytic ferment but has scarcely any diastatic action. 



THE INTESTINAL ENZYMES. 



Practically nothing is known of the enzymes of the small intestine 

 save their action on foodstuffs; none of them have been obtained in 

 even approximately pure condition, and the fact that there are enzymes 

 rests on the observations (1) that the action is destroyed by boiling, 

 and (2) that it takes place under antiseptic conditions. Until the 

 importance of this latter condition was demonstrated by the work of 

 Ktihne on pancreatic digestion, there was much difference of opinion 

 as to whether the succus entericus contained a proteolytic enzyme 

 or not ; some observers had observed digestion of proteids by this 

 fluid, and others had been unable to do so. At length it was shown 

 by Masloff 2 and by Wenz 3 that when precautions are taken to 

 prevent bacterial growth, the succus entericus or extracts of the 

 intestinal mucous membranes have no action on proteids or on 

 albumoses. 



With regard to the action of succus entericus on carbohydrates, the 

 more recent work on the subject all goes to show that starch is con- 

 verted into maltose, maltose into dextrose, and cane-sugar into dextrose 

 and Isevulose, both by the succus entericus and by extracts of the 

 intestinal mucous membrane. 



The succus entericus contains no enzyme which acts on neutral fats. 

 The power of emulsifying fats, which was occasionally observed by the 

 earlier workers on the subject, was doubtless due to the alkalinity of the 



1 Compt. rend. Soc. de bioL, Paris, 1893, tome xlv. p. 648 ; Arch. dephysiol. norm, etpath., 

 Paris, 1893, tome xxv. p. 774. 



2 Untersuch. a. d. physiol. Inst. d. Univ. Heidelberg, 1882, Bd. ii. S. 920. Masloff 

 found very slight action of the juice when acidified, probably due to infiltrated pepsin. 



3 Ztschr. f. BioL, Miinchen, 1886, Bd. xxii. S. 1. This result is confirmed by the 

 observations of Tubby and Manning on human succus entericus, Guy's Hosp. Rep., London, 

 1891, vol. xlviii. p. 277. 



