ACID-PRODUCTION BY MARINE SNAILS 11 



still find in modern science (especially in medicine) some 

 lingering residuum of the painstaking endeavors of the mas- 

 ters of the Middle Ages to impress properly the audience 

 with the fact of the extreme difficulty of understanding their 

 very learned disquisitions. 



However, a physicochemical explanation in point is to 

 be found in the proposition which Daneel predicates upon 

 the principle of ion activity: If it be conceived that free 

 organic acids are produced in the gastric mucous membrane 

 (and we have every reason for assuming that the production 

 of free lactic acid is a function common to cells in general, 

 although the acid is quickly neutralized by the alkalies of the 

 circulating fluids), we may represent by the symbol E 

 an organic acid radical; and the dissociation of sodium 

 chloride and of acid would follow the formulas : 



HE = H' +E'. 



Of the two cations H' is more active than Na' and of the 

 anions Cl' more active than E' ; wherefore from a mixture 

 of sodium chloride and organic acid it is possible for HC1 

 to form by diffusion, as if the stronger mineral acid were 

 driven out of its salt by the much weaker organic acid. It 

 would, of course, not be difficult for any physical chemist 

 to raise exception to this method of explanation. The 

 author, however, has a constant feeling that more attention 

 should be given to the matter; but further progress in the 

 chemistry of colloids, particularly in the obscure field of the 

 phenomena of adsorption, must doubtless be attained before 

 the subject can be further clarified. 



Acid-production loy Marine Snails. In this place it is 

 possible only in the briefest manner to remind the reader 

 that the gastric production of acid among mammals is by 

 no means an isolated phenomenon of this sort in nature. 

 When Johannes Miiller visited Messina in 1854 he saw with 

 astonishment that a streak of fluid from the proboscis of the 



