98 PHYSIOLOGICAL CHEMISTRY. 



peptone is generally applied to the final product of the ener- 

 getic pancreatic digestion. Amphopeptone has been obtained 

 as a yellow powder, very soluble in water and very hygroscopic. 

 It diffuses pretty well through parchment and has a sharp 

 bitter taste. It is not possible to salt out the peptone from 

 solution, but the alkaloid reagents give precipitates, which are 

 soluble in excess. Precipitates are formed by solutions of 

 several of the heavy metallic salts also, but not by copper salts. 



The two forms of amphopeptone which have been described 

 are known as amphopeptone A and amphopeptone B. The 

 first is insoluble in 96 per cent alcohol and is further charac- 

 terized by giving a strong reaction with the Molisch reagent 

 which relates it to the carbohydrate group. The second is sol- 

 uble in 96 per cent alcohol and does not give the Molisch reac- 

 tion. Both forms give a strong biuret reaction. 



As to the exact nature of the antipeptone referred to above, 

 there is still much uncertainty. This was assumed by Kiihne 

 to represent the final product of pancreatic digestion, and it 

 was supposed that even prolonged digestion would not change 

 it further. It was found later, however, that various amino 

 acids appear here in considerable quantity, and that the diges- 

 tion may be carried so far as to yield a product which no longer 

 gives the characteristic biuret reaction ; that is, a product from 

 which everything of a really protein nature has disappeared. 

 This matter will be more fully discussed in a following chapter. 

 The reactions described as characteristic of antipeptone are 

 similar to those for the amphopeptone in the main. A good 

 biuret reaction is obtained if the digestion is not too prolonged, 

 and the alkaloid reagents give precipitates which are soluble 

 in excess. Some of the metallic salts precipitate, but copper 

 sulphate not. 



Formerly many attempts were made to show the relation of 

 these digestive products in tabular or diagram form, but it is 

 now known that most of these diagrams were inexact or rep- 

 resented more than is actually known. One of the latest tab- 

 ular arrangements is that of Hofmeister which shows the rela- 



