330 COLLOIDS IN BIOLOGY AND MEDICINE 



by decomposition of salts through the adsorption of bases by the 

 pellicle of plant cells. 



Investigations of gastric secretion, as far as they relate to physical 

 chemistry, have hitherto almost exclusively consisted of observation 

 of the osmotic condition and the electrolyte concentration; the ma- 

 terial for review is consequently as yet far too limited for a colloid- 

 chemical consideration. 



The Secretions Which Pour Into the Intestines. 



There are 200 c.c. of succus entericus daily secreted by the in- 

 testinal glands. 



The Succus Entericus is usually hypertonic. If we inject into 

 an animal (D'EnRico, chickens, D'ERRICO and SAVARESE, dogs) a 

 hypertonic common salt solution, the osmotic pressure of the succus 

 entericus becomes still higher so that its freezing-point depression 

 may increase to from 0.89 to 0.99 (blood = 0.59). This corre- 

 sponds to our conception that an ultrafiltrate may be concentrated 

 by the absorptive activity of the intestinal wall. The succus en- 

 tericus, like the pancreatic juice which pours into the intestine, 

 is almost neutral. The OH ion concentration is about 10~ 8 at 18 

 according to AUERBACH and PICK. Its alkalinity is approximately 

 that of a sodium bicarbonate solution. On account of its higher 

 sodium bicarbonate content, pancreatic juice has a greater capacity 

 to combine with acid than has succus entericus. 



According to H. ISCOVESCO * 2 the colloids of the pancreatic juice 

 are electropositive; they form with the electronegative colloids of 

 the succus entericus complexes soluble in a neutral environment. 



The Bile: 600 to 900 c.c. of bile are secreted per day. 



The osmotic pressure of the bile is approximately that of the 

 blood; its conductivity is somewhat higher. According to H. ISCO- 

 VESCO, * 2 the colloid constituents of the bile probably have an elec- 

 tronegative charge. 



The Kidneys and the Secretion of Urine. 



(See also p. 409 et seq., on "Diuretics.") 



We shall briefly review the structure of the kidneys of vertebrates: 

 the renal artery branches and in the cortex or outer portion of the 

 kidney develops by the formation of numerous glomeruli an enor- 

 mous surface (Fig. 50) . These are knotted ball-like branches of the 

 smaller arterial vessels placed in a vesicle (Bowman's capsule). The 

 artery leaves Bowman's capsule, subdivides into capillaries which 

 collect together and form the renal veins. Bowman's capsule has an 



