40 PROTEIDS. 



Having thus briefly stated the steps by which our present know- 

 ledge has been reached of the possible products of a digestive conversion 

 of proteids, it now remains to deal with these products seriatim. In 

 so doing it will be best to describe first such products as arise most 

 largely and characteristically during the action of acids, and to treat of 

 the albumoses and peptones subsequently. 



Antialbumate. This substance is according to Kiihne identical 

 with Meissner's parapeptone. It is most readily formed by the fairly 

 prolonged action of dilute acids at 40, but it may also make its 

 appearance, but to much smaller extent, during a peptic digestion in 

 which but little pepsin is present. It is obtained, mixed in some cases 

 with variable quantities of an ordinary acid albumin, by neutralising 

 the digesting mixture, from which it is thus precipitated. As already 

 stated, it is characterised by the property that it cannot be converted 

 into a peptone by the most prolonged action of even the most active 

 pepsin, while on the other hand it is readily peptonised by trypsin and 

 yields then antipeptone, but no leucin or tyrosin. Apart from its be- 

 haviour with pepsin and trypsin, it resembles ordinary acid-albumin and 

 syntonin in its general chemical reactions. But the latter are chemi- 

 cally quite distinct from antialbumate or parapeptone, for either of 

 them may be peptonised by pepsin, and the peptones thus formed may 

 be partly made to yield leucin and tyrosin by the subsequent action of 

 trypsin. 



Antialbumid. By the further prolonged or active treatment of 

 antialbumate with acids it is converted into the substance to which 

 Kiihne gave the name of antialbumid. It is in all respects identical 

 with the ' hemiprotein ' of Schiitzenberger, and also probably with the 

 dyspeptone of Meissner, so far as the latter was not perhaps largely 

 composed of nucleins. It also makes its appearance, but in very small 

 amount, during a peptic digestion, and in considerable quantity during 

 a pancreatic. It is characterised by its relatively great insolubility in 

 dilute acids and alkalis, so that it separates out as a granular residue 

 during a pancreatic digestion. This residue is readily soluble in 1 p. c. 

 caustic soda; if reprecipitated by neutralisation, it is now soluble 

 in 1 p. c. sodium carbonate. From either of these solutions it is 

 very completely precipitated by the addition of a little sodium chloride. 

 In dilute alkaline solution (1 p. c. Na 2 Co 3 ) it may be partly 

 converted into a peptone by the action of trypsin, during which 

 process the larger part separates out into a gelatinous coagulum 

 or clot, which is quite unacted upon by pepsin and can only be 

 peptonised by the prolonged action of very active trypsin in presence 

 of a considerable amount (5 p. c.) of sodium carbonate. The peptone 



