We find an analogous process in the absorption of fats. As we have seen, the fats of the food are broken apart in the small intestine into glycerin and free fatty acid, a portion of the latter, and perhaps all, combining with the alkali of the intestinal juices to form soluble soaps, or sodium salts of the respective fatty acids. The neutral fats present in animal and vegetable foods are all alike in containing the glyceryl radicle, but they differ in the character of the fatty acids present. Further, one form of animal fat, like that from beef, may contain quite a different proportion of stearin, palmitin, and olein than is present in the fat of another animal, like mutton. By digestion, however, they are all broken apart into fatty acid and glycerin. These acids and their salts can be readily detected in the intestine, but they are not found in the blood or lymph, yet shortly after fatty food is taken the lymph is seen to be milky from fat. Obviously, the fatty acids liberated in the intestine are absorbed, either as soluble soaps or as free fatty acids dissolved in bile, but as they pass through the epithelial cells of the intestine into the lacteal radicles, there is a synthesis or reconstruction of fat; and as a result, neutral fats and not soaps are found in the lymph. Here, then, we have a process quite analogous to what apparently occurs in the absorption of proteid, though less complex; and it is possible that this is one of the factors which aids in the formation of a specific fat mixture corresponding, in a measure, to the type of fat present in the particular species. It is well understood that the fat of an animal’s tissues may be modified somewhat by the character of the fat fed, yet in spite of this there is a certain degree of constancy in composition which calls for explanation. Sheep and oxen feeding in the same pasture have fat widely different in the proportion of stearin, palmitin, etc. The fat of man’s tissues is fairly definite in composition, yet he eats a great variety of fatty foods. One man may consume large amounts of hard mutton fat with its relatively large content of stearin, while another individual may take his fat mainly in the form of the soft butter fats, with their relatively large content of olein and palmitin. In both cases, the fat of the man’s tissues will be essentially the same. To be sure, the changes that take place in the tissue cells, reinforced by the construction of fat from other sources, may be partly responsible for this constancy of composition, but the transformations incidental to absorption are quite possibly, in some measure, helpful thereto.