244 A MANUAL OF VETERINARY PHYSIOLOGY 



that portion of the duct penetrating the wall of the intestine, by 

 which means the bile is driven back through the cystic duct to the 

 gall-bladder. The bile as formed is propelled along the bile -ducts 

 by a contraction of the muscular coat of the tubes, but doubtless 

 both the forcing onward of the bile and the circulation through 

 the liver are largely assisted by the respiratory movements, 

 during which the liver is compressed between the abdominal 

 viscera and the diaphragm. 



By some it is considered that no bile enters the bowel while 

 the stomach is empty, but that the passage of acid chyme along 

 the duodenum causes a reflex contraction of the gall-bladder, 

 and an injection of bile into the intestine. 



The amount of bile secreted varies, but is greater in herbivora 

 than carnivora. Colin's experiments gave him the following 

 amounts as hourly secretions : 



Horse - 250 to 310 grammes (8 to 10 ounces) per hour. 



Ox - 93 to 120 „ (3 to 4 ounces) per hour. 



Sheep - 8 to 150 „ (£ ounce to 5 ounces) per hour. 



Pig - 62 to 150 ,, (2 to 5 ounces) per hour. 



Dog - 8 to 16 ,, (I to \ ounce) per hour. 



The Use of the Bile from a digestive point of view is disappoint- 

 ing, inasmuch as it does not digest in the same sense that pepsin 

 and trypsin do. It is intimately connected with the function of 

 the pancreas, with which object the secretions are poured out 

 either close together in the bowel, or, as in some animals, by a 

 duct practically common to the two glands. As the horse 

 possesses no gall-bladder, the secretion is poured into the intes- 

 tine as fast as it is prepared ; not so with the ox, sheep, pig, 

 and dog, where the bulk of it is stored up in a capacious recep- 

 tacle until required. The reason offered for the horse having 

 no gall-bladder is that as digestion, under ordinary circumstances, 

 never ceases, the bile is poured into -the bowel as fast as it is 

 secreted, but that in the case of other animals it is only poured 

 out when the contents of the stomach are passing out into the 

 intestine. This explanation, however, does not meet all the 

 difficulties of the case. The following animals, like the horse, 

 have no gall-bladder : the camel, elephant, rhinoceros, tapir, and 

 deer. 



The bile being alkaline, its first action on the chyme is to neu- 

 tralise the gastric juice, and precipitate the albumoses and 

 peptones. One effect of this is probably to delay the progress 

 of the chyme along the bowel, by which means absorption is 

 assisted. 



Bile has a solvent and emulsifying effect on fats, being more 

 active in the presence than in the absence of pancreatic juice. 



