That portion of chyme which is not needed, or cannot be converted into chyle, descends into the intestines, and is finally carried out of the body by the rectum. The manner in which the gastric fluids act on alimentary matter, is by solution and chemical action; for cornstalks and foxgrass, that cannot be dissolved by ammonia or alcohol, yield readily to the solvent power of the gastric secretion. Bones and other hard substances are reduced to a pulpy mass in the stomach of a dog; while, at the same time, many bodies of delicate texture remain in the stomach, and ultimately are ejected, without being affected by the gastric fluids. This different action on different subjects is analogous to the operation of chemical affinity, and corroborates the theory that digestion is effected by solution and chemical action. _The Spleen_, or _Milt_, is an oblong, dark-colored substance, having attachments to the paunch. It is composed of blood-vessels, nerves, and lymphatics, united by cellular structure. It appears to serve as a reservoir for the blood that may be designed for the secretions of bile in the liver. P. M. Roget says, "Any theory that assigns a very important function to the spleen will be overturned by the fact, that in many animals the removal of this organ, far from being fatal, or interrupting, in any sensible manner, the continuance of the functions, seems to be borne with perfect impunity." Sir E. Home, Bichat, Leuret, Lassaigne, and others, suppose that "the spleen serves as a receptacle for the superfluous quantity of fluid taken into the stomach."