From the liver the bile is conducted into the duodenum through a membranous tube, of about the diameter of a quill, and which is called the _biliary_ or _hepatic duct_. In its course a similar pipe, called the _cystic duct_ (from κυστις, _kystis_, a bladder), from the gall-bladder, unites with it into one trunk, like the two limbs of the letter Y; and this trunk enters the duodenum by an orifice common to it and the pancreatic duct. In the healthy state bile is to be found only in the duodenum, and not in the stomach; although one would suppose the contrary from the familiar way in which we speak of the stomach being oppressed with bile, and of our being “very bilious.” When vomiting is excited, either artificially or by illness, we, no doubt, often bring up plenty of bile. Sometimes this bile has been existing in the stomach, and causing nausea; but very often it is brought into the stomach solely by the inverted action which constitutes vomiting, and was consequently placed there by the very remedy which is supposed to have cleared it away. The process of vomiting is accompanied by an inverted action of the intestinal canal whereby it propels its contents upwards instead of downwards, and thus the bile is, as it were, forced up from the duodenum into the stomach, instead of being propelled downwards and expelled in the usual way. Hence, in sea-sickness for example, the first fits of retching generally bring up nothing but food or mucus--the real contents of the stomach,--and it is only after continued straining that bitter bile makes its appearance. In the healthy state, fat or oily food often causes the presence of bile in the stomach, as if its aid were necessary there for the accomplishment of digestion. The _pancreas_, or sweetbread, PP, is a large oblong gland, which lies across the spine, and secretes a fluid almost identical with the saliva. Its duct, as stated above, enters the duodenum along with the biliary duct, so that the two fluids meet at their entrance, which takes place at the first curvature of the intestine, at the distance of about one-third of its whole length from the stomach. The bile and pancreatic juice thus poured out together are both requisite for the formation of chyle, and apparently modify the action of each other. The bile being somewhat of an unctuous nature, and the pancreatic juice somewhat alkaline, their union forms a kind of saponaceous compound, which is less irritating and more easily incorporated with the chyme than pure bile.