314 ANIMAL PHYSIOLOGY. 
present in this fluid depending much on the length of its stay 
in the gall-bladder, which secretes this substance. 7%. There is 
throughout the entire alimentary tract a secretion of mucus 
which must altogether amount to a large quantity, and it has 
been suggested that this has other than lubricating or such like 
functions. It appears that mucus may be resolved into a pro- 
teid and an animal gum, which latter, it is maintained, like 
vegetable gums, assists emulsification of fats. If this be true, 
and the bile is, as has been asserted, possessed.of the power to 
break up this mucus (mucin), its emulsifying effect in the in- 
testine may indirectly be considerable. Bile certainly seems 
to intensify the emulsifying power of the pancreatic juice. 
There does not seem to be any ferment in bile, unless the 
power to change starch into sugar, peculiar to this secretion in 
some animals, is owing to such. 
Comparative—The bile of the carnivora and omnivora is 
yellowish-red in color; that of herbivora green. The former 
contains taurocholate salts almost exclusively; in herbivorous 
animals and man there is a mixture of the salts of both acids, 
though the glycocholate predominates. 
Fie. 268.—Gall-bladder, ductus choledochus and pancreas (after Le Bon). a, gall-bladder ; 
b, hepatic duct ; c, opening of second duct of pancreas; d, opening of main pancreatic 
duct and bile-duct ; e, e, duodenum ; /, ductus choledochus ; p, pancreas. 
Pancreatic Juice.—-This fluid is found to vary a good deal 
quantitatively, according as it is obtained from a temporary 
(freshly made) or permanent fistula—a fact which emphasizes 
