334 A MANUAL OF PHYSIOLOGY 



stance is less stable or less easily extracted from the gland than 

 is trypsinogen. In this respect amylopsin also resembles ptyalin. 

 A small amount of maltase is contained in pancreatic juice, 

 and further hydrolyses to dextrose a portion of the maltose 

 formed by the amylopsin. 



Steapsin splits up neutral fats into glycerin and the corre- 

 sponding' fatty acids. The latter unite with the alkalies of the 

 pancreatic juice and the bile to form soaps. In this important 

 process bile acts as the helpmate of pancreatic juice ; together 

 they effect much more than either or both can accomplish by 

 separate action. Many tissues contain fat-splitting ferments or 

 Upases, which are probably not identical with steapsin. Steapsin 

 exists as active ferment in the pancreatic juice, but there is 

 some reason to believe that a portion of it may be present as a 

 mother-substance, steapsinogen, in the gland, and probably in 

 the secretion as well. Active steapsin can also be extracted 

 from the pancreas by glycerin or water. It is to be noted that 

 it is only the proteolytic enzyme which is totally inactive till it 

 reaches the intestine. The significance of this will be discussed 

 later on. 



Bile. Bile is a liquid the colour of which varies in different 

 groups of animals, and even in the same species is not constant, 

 depend ng on the length of time the fluid has remained in the 

 gall-bladder and other circumstances. When it is recognised 

 that the colour is due to a series of pigments, which are by 

 no means stable, and of which one can be caused to pass into 

 another by oxidation or reduction, this want of uniformity will 

 be easily intelligible. The fresh bile of carnivora is golden- 

 red. The bile of herbivorous animals is in general of a green 

 tint, but, when it has been retained long in the gall-bladder, may 

 incline to reddish -brown. Fresh human bile, as it flows from a 

 fistula just established, is of a reddish-brown, golden-yellow 

 or yellow colour. Beaumont speaks of the yellowish bile which 

 he could press into the stomach of St. Martin by manipulating 

 the abdomen. In a case observed by the writer, it was seen that 

 when the bile flowing from a fistula was allowed to spread out 

 in a dressing, it became greenish, because of oxidation of a part 

 of the bilirubin to biliverdin, although as it actually escaped 

 from the fistula it was yellow. The bile of a monkey taken from 

 the gall-bladder immediately after death is dark green, but if 

 left a few hours in the gall-bladder it is brown, the green pigment 

 having been reduced. It should be remembered that human 

 bile from the post-mortem room may alter its colour in the 

 interval which must elapse before it can usually be procured 

 after death. Bile, as obtained from fistulae in otherwise healthy 

 persons, has a specific gravity of about 1008 to 1010. In the 



