SECTION VI 

 THE BILE 



THE fact that the bile, the secretion of the liver, is in so many 

 animals poured into the intestine by an orifice common to it and 

 the pancreatic juice suggests that these two fluids co-operate in 

 their actions on the ingested food-stuffs, and points to a direct use 

 of the bile in the processes of digestion. In addition to this function, 

 the bile must also be regarded as an excretion, representing as it 

 does the channel by which the products of disintegration of haemo- 

 globin the red colouring -matter of the blood are got rid of from 

 the organism. As an excretion the production of bile must be 

 continuous, and related, not to the processes of digestion, but to the 

 intensity of destruction of the red corpuscles. On the other hand, 

 bile, as a digestive fluid, is needed in the gut only during the period 

 that digestion is going on. The exigencies of the body therefore 

 require a continuous excretion of bile by the liver, but a discontinuous 

 entry of this fluid into the small intestine. This discontinuity in the 

 entry of a continuous secretion into the intestine is secured, in the 

 majority of animals, by the existence of the gall-bladder, a diverti- 

 culum from the bile -ducts, in which all bile, secreted during the 

 intervals between the periods of digestive activity, is stored up. 

 In the horse, where the gall-bladder is absent, its place is taken to 

 some extent by the great size of the bile -ducts. Moreover in such 

 an animal the process of digestion is much more continuous in char- 

 acter than it is in carnivora. Since the bile accumulates in the gall- 

 bladder during the whole time that digestion is not going on^and 

 is only poured into the gut during digestion, in a fasting animal 

 the gall-bladder is distended, whereas in an animal some hours after 

 a meal the gall-bladder is practically empty. 



During the period that the bile secreted by the liver remains 

 in the gall-bladder it undergoes certain changes, as is shown by 

 comparison of the composition of bile obtained from the gall-bladder 

 with that obtained from a fistula of the bile-duet. 



803 



