ORGANIC PRINCIPLE OF DIGESTIVE JUICES. 77 



becomes endowed with one or other of these properties, according as it is 

 acidulated or alkalinized, the function of digestion is presented to us un- 

 der a simple aspect. It is upon these principles that we may explain 

 the fact that the presence of bile in the stomach suspends or arrests the 

 digestion going on in that organ. 



Though the views here expressed are such as are received among many 

 chemists, yet it is still open for consideration whether the The nature of 

 nature of the result which is reached in these cases does not, the or s anic in - 



. gredient more 



to a great extent, depend upon the nature of the organic important than 

 changing body, the ferment, which first sets up the action. the reaction - 

 Many circumstances would lead us to infer that this must be the case, 

 and that, as with differences of temperature, so also with these differences, 

 the final result may present distinct variations, though they may be with- 

 in a certain range or limit. Thus, though the saliva and pancreatic juice 

 are both alkaline, and both impress in a general way the same digestive 

 change on starch and sugar, a minute examination of the results of their 

 action would doubtless lead to the detection of shades of difference va- 

 riations which could only be attributed to the difference between the act- 

 ive organic principle of the pancreatic juice, and ptyaline, the correspond- 

 ing principle of the saliva. 



The imputed control which the alkalinity or acidity of the digesting 

 juices exerts in determining the result, illustrates the import- j> e ] at j n f 

 ant function discharged by common salt, which furnishes to common salt in 

 the juices of the stomach and intestine the characteristic in- dl estlon - 

 gredients they require by breaking up readily into hydrochloric acid and 

 soda, and re-forming at once whenever these materials are brought in 

 contact. There is, therefore, an important reason for the instinct which 

 animals display in resorting to the use of this substance, as in the buffa- 

 lo licks at the West, and the necessity which men experience to add it 

 as a condiment to their food. But though, by furnishing an acid or al- 

 kali, as the case may be, it determines the nature of the work which the 

 secreting juices perform, it is not to be regarded as the prime mover of 

 the change. It guides rather than works. The efficient principle bring- 

 ing about digestion appears always to be a nitrogenized body, acidulated, 

 perhaps, for the production of one duty, and rendered alkaline for the per- 

 formance of another. 



Directing our attention now more particularly to the phenomena dis- 

 played by such a changing nitrogenized principle, the folio wing, illustra- 

 tions will serve to show that there is nothing mysterious in its operation. 

 Out of many cases which might be selected, those now to ]be offered are 

 more particularly interesting, since they refer to substances extensively 

 used in the diet of man. 



First, of wine. A grape, if perfectly sound, will keep for a consider- 



