6. We have already considered some few mineral substances which are absorbed by the aid of the free alkali contained in the Biliary and Pancreatic secretions.[26] The sixth kind of absorbed matters consists of some vegetable and animal products which can only be rendered soluble by a similar agency. Fats and oils, resinous matters, and some principles resembling resins, come under this head. Fats and fixed oils consist of acids, as Stearic, Margaric, and Oleic, insoluble in water, in combination with a base, Glycerine, which, when isolated, is soluble. With a free alkali such a fat forms a soluble salt, called a soap, and the base Glycerine is set free. In Man the Bile and Pancreatic juice are discharged together into the middle of the Duodenum. The fatty matters of the food are not absorbed before they meet with these secretions. But, after they have mixed with them, a milky fluid, called chyle, is formed, which is then taken up by the lacteal absorbents. It passes thence into the Thoracic duct, meeting there with an albuminous lymph, and is discharged at length into the general circulation at the junction of the left jugular and subclavian veins. M. Bernard, in some papers laid lately before the French Academy, states, as the result of his experiments, that the function of the Pancreatic juice is to reduce the fat to the condition of a white emulsion. He states that no milky chyle is formed when the Pancreatic ducts are tied in dogs. He considers it absolutely necessary that saccharine and albuminous matters should be absorbed by the capillaries of the Portal veins, and then pass through the liver; and believes that the sole function of the lacteals is to take up fat thus emulsified. His experiments and inferences have received the high sanction of M. Magendie. M. Frerichs has since affirmed that, whatever be the function of the Pancreatic juice, the Bile, by virtue of the alkali which it contains, is an indispensable agent in the absorption of fats. But M. Bernard has also found that the Pancreatic juice is always alkaline in health. Whatever be the particular function of the Bile, it may reasonably be concluded that the alkali contained in one or both of these fluids is engaged in the saponification and solution of the emulsified fats. If it were not for this, this alkali would seem without an object; and further, it is contrary to all we know of the process of absorption to suppose that oil could pass through to a watery fluid without the intervention of an alkali to reduce it to the soluble state. Thus it would seem likely that by means of the Pancreatic juice, with or without the aid of the Bile, fatty matters are first emulsified, in order to undergo an increase of surface, and then again saponified before they can be absorbed by the lacteal villi.