436 SCIENCE PROGRESS 



These reactions completely negative the idea that the whole 

 of the proteoclastic changes due to pancreatic juice are the work 

 of one enzyme only. There are clearly two present, though so 

 far the actual division of labour between them does not seem 

 clearly established. Vernon's experiments leave open the 

 question of the exact role of trypsin, i.e. whether it is pepto- 

 clastic, or whether the whole of the peptone-splitting is due to 

 the erepsin. 



Besides its existence in the digestive juices of the pancreas 

 and the small intestine, erepsin has been ascertained to be 

 more or less abundant in almost all the tissues of the body, and 

 not to be restricted to those of warm-blooded animals. Much 

 of our knowledge on this head, again, is due to Vernon, who has 

 made very exhaustive researches in this direction. It seems, as 

 a tissue enzyme, to be most abundant in the kidney; then, in 

 order of quantity, in the intestine, pancreas, spleen, liver, and 

 muscles. Whether its prominence in the kidney is connected 

 with the profound proteoclastic action which produces urea 

 may be a subject for further research. 



The distribution of erepsin has not been exhaustively 

 ascertained at present. Cohnheim holds it, as does Vernon, to 

 be very widespread in the animal kingdom. From a study of 

 the products of digestion in the Octopoda, he has been led to 

 believe in its existence in their alimentary canal. Suspending 

 the latter, under appropriate precautions, in a bath of the blood 

 of the animal, kept oxygenated by leading a stream of the gas 

 through it, he found that the canal maintained its spontaneous 

 movements, and absorption of the foodstuffs it contained went 

 on. After some tine crystalline derivatives of proteid were 

 found in the blood-bath, but nothing giving a biuret reaction. 

 The blood circulated through the alimentary canal contained 

 neither. 



Vernon also has discovered erepsin in various groups below 

 the Mammalia, tracing it in almost all the tissues of the pigeon, 

 the frog, the eel, and the lobster, and in the organ of Bojanus 

 and the muscles of the Anodon. The amount obtainable was, 

 however, relatively small in the tissues of the cold-blooded 

 animals, with the exception of the pancreas of the frog, which 

 was singularly rich. 



Researches made upon the proteoclastic enzymes of plants 

 during the period under consideration have been very fertile in 



