304 



COMPARATIVE PHYSIOLOGr. 



derived from the decomposition of the bile acids. Part of their 

 mucus must also he referred to the bile, the quantity originally 

 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 emulsiflcation 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. 



Fig. 246.— Gall-bladder, ductus choledochus and pancreas in man (after Le Bon), a, 

 gall-bladder: b, hepatic duct; c, opening of second duct of pancreas: d, opening 

 of main pancreatic dnct and bile-duct; «, «, duodenum; /, ductus eiioledochnB; ji, 

 pancreas. 



