204 CHEMISTRY OF THE PROTEIDS CHAP 



somewhat larger amounts in human milk. Siegfried attributes to 

 these substances, especially in muscle, a considerable biological import- 

 ance, but Folin l and Kutscher 2 throw doubt on the chemical uniformity 

 of these derivatives. 3 



Physiology of Albumoses and Peptones 



The part played by the hydrochloric acid in peptic digestion is as 

 yet but little understood. Meissner 4 stated that 0*2 per cent hydro- 

 chloric acid, acting on non-coagulated egg-white, produces a water- 

 soluble substance not coagulable by heat, which we now know to be an 

 acid-albumin, while Goldschmidt and Lawrow, as already stated on 

 p. 199, maintain that hydrochloric acid without pepsin will ultimately 

 produce the same effect as if pepsin had been present. From this it 

 would appear as if the chief function of the pepsin was to hasten the 

 effect of the hydrochloric acid. If the author's view is correct that 

 the greater part of an albumin molecule under normal conditions is in 

 the pseudo-acid-pseudo-basic state, i.e. that the amino-acids in the 

 albumin molecule become de-ionised owing to ring-formation occurring 

 (see pp. 211 to 215), then the first stage in gastric digestion must be 

 the opening up of these rings, This may be done, firstly, either by the 

 action of the acid H-ion of the HC1 of the gastric juice, or the basic 

 OH 7 - radical of the sodium carbonate of the pancreatic juice ; or, 

 secondly, by the enzymes uniting primarily with the albumin. If we 

 consider how firmly enzymes adhere to the albumins, it becomes 

 necessary to explain this union as depending on chemical action, and 

 it is legitimate to suppose that the new chemical compound is so 

 constituted that it is readily split up by the H- or OH'-ions. If 

 ferments are able of reacting in both alkaline and acid media, then, 

 according to the author's view, these ferments must be considered to 

 be amphoteric (see p. 208). 



Attention is also directed in this connection to the interesting 

 observation of Schwarz 5 that trypsin cannot act on albumin which has 

 been treated with form- or acet-aldehyde, while pepsin + HC1 has the 

 power of acting on the acid methylene- and ethylene-albumins, which 

 are formed by the action of the corresponding aldehydes. 



For the combined action of pepsin and hydrochloric acid it is best 

 to employ the pure gastric juice obtained by J. Pawlow's method, as 



1 0. Folin, ' Some Constituents of Witte's Peptone,' Zeitsclir. f. physiol. Chem. 25. 

 152 (1898). 



2 Fr. Kutscher, ' Antipepton,' I. bis III. ibid. 25. 195 (1898), 26. 110 (1898), 28. 

 88 (1899). 3 Meissner, Zeitschr.f. rationale Medizin, III. 8. 280 (1860). 



4 Leo Schwarz, Zeitschr.f. physiol. Chem. 31. 460 (1901). 



5 See Zentralbl.f. Physiol. 1904, under 'Nucleon.' 



