286 APPLIED PHYSIOLOGY 



cause jaundice. By squeezing the liver between the 

 diaphragm and the abdominal muscles the pressure is 

 raised, and the escape of bile favoured. This is believed 

 to explain the beneficial effect of horseback exercise in 

 some cases. During the act of vomiting the liver is 

 forcibly squeezed in this way, and the older school of 

 physicians used often to induce an artificial vomit at the 

 outset of an acute fever, in the belief that by this means 

 poisonous materials could be voided from the liver. 



The discharge of bile into the intestine reaches its 

 maximum about three hours after a meal, and is ap- 

 parently brought about by contraction of the muscular 

 coat of the gall-bladder, the motor nerve for which is the 

 vagus, whilst the sympathetic supplies it with relaxing 

 fibres. If the gall-bladder contains biliary calculi its 

 contraction causes pain, and the occurrence of this at 

 a definite period after the taking of food is apt to suggest 

 that the pain is of gastric origin, and to lead to errors of 

 diagnosis. 



In addition to the well-recognized biliary constituents, 

 it is probable that the liver excretes or destroys other 

 toxic materials, some of which may be derived from the 

 bowel, and inefficiency in performing this function has 

 been advanced as an explanation of biliousness. The 

 liver, in fact, may be regarded as a filter placed between 

 the portal system and the general circulation, the 

 purpose of which is to prevent the escape of poisonous 

 materials from the former into the latter. Seeing, too, 

 that the liver is concerned in the final stages of the 

 formation of urea, and in the destruction of uric acid, 

 it must be regarded as in every respect one of the most 



