The spleen may be removed from the body without any marked changes taking place in the blood or the economy generally. It is said that if an animal whose spleen is extirpated be allowed to live for a certain time, the lymphatic glands increase in size, or become swollen.

In attempting to assign a definite function to the spleen all the foregoing facts must be carefully reviewed, and the peculiarity of its (i) structure, (2) chemical composition, (3) the changes the blood undergoes while flowing through it, (4) the variations in blood supply which follow normal and pathological changes in the economy, and (5) the absence of effect following its extirpation, must all be borne in mind.

Its structure teaches us that it is intimately related to lymphatic glands. The Malpighian bodies are simply lymph follicles, and the pulp may be regarded as a sinus like that of a lymph gland, with this difference, that it is traversed by blood instead of lymph. The cell elements found in it indicate that not only white cells are rapidly generated, but also that these cells have some peculiar relationship to haemoglobin, as they are often found to contain some. The varieties in size, form, and general appearance of the red corpuscles can be accounted for by either their destruction or their formation occurring in this organ.

Its chemical composition also shows that certain special changes go on in the pulp, and that probably stages of the construction or destruction of haemoglobin are here accomplished may be inferred from the peculiar association of iron with albuminous bodies.

From the characters of the blood flowing from the spleen it has been argued that, besides an enormous production of white corpuscles, the destruction of the red discs goes on, while some new discs are formed, probably by means of the white cells making haemoglobin in their protoplasm, which, gradually disappearing, leaves only the red mass of haemoglobin.

The increased activity of the spleen after meals, and in certain abnormal states of the blood, as shown by its containing more blood, distinctly points out that some form of blood elaboration goes on in it, which is nearly related to, or associated with, nutrition.

Section of Spleen through a lymph follicle (Malpighian body).

Fig. 163. Section of Spleen through a lymph follicle (Malpighian body) (a) injected to show the vessel (c) entering the follicle, the lymphoid tissue of which is pale in comparison with the pulp (6), the meshes of which are filled with injection. (Cadiat).

The swelling of the lymphatic glands after extirpation of the spleen confirms its relation to these organs, and the fact is undisputed that it is a source of the white corpuscles of the blood; but the paucity of evidence after this operation as to changes in the number or character of the red discs proves that if the spleen be either the place of origin or destruction of the red corpuscles it cannot be the only organ in which they are produced or destroyed.