SECRETION AND EXCRETION 329 



secretion, there is an increase of the alkali carbonates in the mucus, 

 which like all alkaline substances fluidify the mucus colloids, 

 especially the mucin. The utilization of potassium iodid as an ex- 

 pectorant may be similarly interpreted; possibly it also favors ultra- 

 filtration in the sense of H. BECHHOLD and J. ZIEGLER. Moreover, 

 R. HOBER upon applying iodin found an increase in the ciliary move- 

 ments in the ciliated epithelium of frogs; this increased activity 

 may assist in the discharge of mucus. 



Gastric Juice. 



The daily excretions of the stomach amount from 1000 to 

 2000 c.c. 



As has been mentioned, the osmotic pressure of the gastric juice 

 usually is less than that of the blood, and according to H. STRAuss* 2 

 it normally has a freezing-point depression of from 0.36 to 0.48. 

 Pathologically it may rise to 0.58, which is the freezing-point depres- 

 sion of the blood. It is of especial interest to know that in those 

 cases where osmotic pressure approaches that of the blood, accord- 

 ing to H. STRAUSS, free HCl is usually absent. These observations 

 have been confirmed by others (WINTER, S. SCHONBORN). This 

 fact of itself would indicate that in a stomach where the second 

 glandular function, the modification of the ultrafiltrate, is arrested, 

 the composition of the gastric juice is more like that of the blood 

 crystalloids. We cannot omit to mention that another fact is 

 opposed to this: in normal gastric juice, the NaCl content is nearer 

 that of the blood (0.59 per cent) than in subacidity. Unfortunately, 

 I know of no adequate data upon pure gastric juice from a subacid 

 stomach, so that for the present the interpretation must remain 

 indefinite. 



The secretion of a juice with free hydrochloric acid from a neutral 

 fluid, the blood, is one of the problems which offers especial diffi- 

 culties to physiologists. An attempt has been made to explain the 

 phenomenon by the law of mass action with the help of carbonic acid. 

 In my opinion colloid chemistry offers analogies which permit an 

 unforced explanation. We know that neutral salts may be split into 

 acids and bases by adsorption (see p. 28); thus, for instance, an acid 

 fluid with free sulphuric acid remains after shaking a solution of 

 potassium sulphate with hydrated manganese dioxid (J. M. VAN 

 BEMMELEN). With this in mind we need not be surprised at the 

 splitting off of free HCl from a solution of chlorids. 



The secretion of gastric juice is analogous to the secretion of acid 

 by plant roots, which, according to BAUMANN GULLY, likewise occurs 



