PANCREATIC JUICE. 403 



white precipitate. Prussiate of potash a bulky white, and red 

 prussiate a green precipitate. Carbonate of soda throws down a 

 white gelatinous precipitate, soluble in water and alcohol. The 

 liquor is still precipitated by tannin but not by prussiate of po- 

 tash. It is also precipitated by acetate of lead and by a solution 

 of alum. Corrosive sublimate throws down a bulky white pre- 

 cipitate, and sulphate of copper an abundant greenish -blue pow- 

 der. Vogel analyzed this last precipitate, and found the albu- 

 men unaltered in its chemical constitution. Nor does the fibrin 

 dissolved in the pepsin liquor seem to have changed its nature.* 

 From the preceding detail, which has been lengthened out in 

 consequence of the obscurity of the subject, it appears that the 

 gastric juice is secreted only when the stimulus of food is applied ; 

 that it is a clear transparent liquid containing as essential ingre- 

 dients, about 2 1 per cent, of muriatic acid, and a certain pro- 

 portion of pepsin which has not been determined. Whether the 

 pepsin of the gastric juice be analogous to amygdalin of the al- 

 mond, has not been determined. It is much more probable that 

 it is a substance quite peculiar, formed in the stomach for the 

 express purpose of converting the food into chyme. 



CHAPTER V. 



OF THE PANCREATIC JUICE. 



THE pancreas is a conglomerate gland resembling closely in its 

 appearance the parotid. It is about the size of a dog's tongue, 

 and extends from the spleen to the curve of the duodenum, rest- 

 ing over the spine. The duct, which conveys the liquid secret- 

 ed by the pancreas, was first demonstrated by John George Wir- 

 sung of Bavaria in 1641 ; though it is stated by Haller that it 

 was, pointed out to Wirsung by Maurice Hoffmann. Be that as 

 it may, Regnier de Graaf collected the gastric juice of a dog in 

 1664, and endeavoured to determine its nature. He opened the 

 duodenum, introduced a quill into the pancreatic duct, and al- 

 lowed the liquid to pass through it into a bottle. He describes 

 it as limpid and acidulous, or most commonly acidulo-saline. 



* Jour de Pharmacie, xxv. p. 652. 



