The chemical composition of the spleen confirms the view that a retrograde change of tissue occurs very freely in it. In 1000 parts there were found (by OidtInann) nearly 250 of solid residue, of which more than 243 were organic, consisting of albumen, fats, inosite, uric acid, sareine, xanthine, leucine, tyrosine, and pigment, all of which, excepting the first two, are products of the metamorphosis of tissue. This gland also contains a large quantity of oxide of iron, obtained probably from the disintegration of red blood-disks in it.
With regard to its uses, it may be regarded as a storehouse of nutritive material, which may be drawn upon according to the requirements of the system ; and of the exertion of an assimilative action upon the albumininous matter, during its withdrawal from the general current of the circulation, we have direct evidence iu the large increase in the proportion of fibrine contained in its venous blood—the blood of the, splenic vein sometimes containing nearly six times the usual quantity of fibrine. Before the institu tion of the chemical inquiries which led to the above conclusion, it was held that the func tion of the organ was to act as a reservoir for the portal blood, with the view of pre venting the portal vessels from being unduly distended during the digestive process. To what extent it is the seat of the disintegration of old blood-corpuscles, and of the formation of new ones, is still uncertain. The removal of this organ from the body
has frequently been performed in animals without serious effects; but in some of these cases, small secondary spleens are developed, and in others, various sets of lymphatic glands are observed to increase rapidly, shortly after the operation, and these probably act vicariously for the spleen. Its singular and complicated microscopic structurb, and its extreme vascularity, would lead to the inference that this is a highly important viseus.
It is unnecessary to enter into any detail regarding the diseases of the spleen, as most of them occur secondarily in the course of other affections, as in intermittent fever (ague) and leucocythemia (q.v.), when it is sometimes enlarged to 40 times its natural weight. It is sometimes diminished to the size of a walnut, the eituf,e of this atrophy being unknown, but the apparent result being a loss of color, aed a compara tively bloodless condition. The spleen is also liable to the singular morbid change known as waxy degeneration, in which the presence of starch like amyleld granules is observed in the tissue on submitting it to microscopico-chemical inverXgation. These remarkable granules dissolve when heated iu water, and by the action a iodine acquire a bluish tint, but not the pure iodide of starch purple. In their ultimate composition, however, these granules-resemble the albuminates rather than starch, inasmuch as they contain nitrogen.