Hyperaemia of the spleen arises either from a mechanical impediment in the circulation of the blood, or from the peculiar relation alluded to as existing between the spleen and certain anomalous conditions in the fluids.

The first variety occurs in organic diseases of the heart and in hepatic obstructions, though not, especially in the former, to the extent, nor as frequently, as might be expected from obstacles or stasis affecting the entire system of the vena cava and venae portae. The deranged circulating fluid appears to have no affinity for the tissue of the spleen, and to be thus in part carried off, and in part mechanically retained. This latter portion, in the first instance, induces a hypersemic turgor of the organ, and gives it a dark-red color, and subsequently, as is generally the case in these hyperaemiae, induces hypertrophy of the fibrous tissue and of the pulpy parenchyma of the spleen. The organ is more consistent, indurated, and dense.

The second form accompanies various dyscrasic conditions of the fluids, and in proportion to their duration induces an acute or chronic tumor of the spleen, which differs in appearance, and in its primary and secondarv constitution, according to the nature of the cause.

The hyperaemiae affecting the peripheral portion of the organ not unfrequently degenerates into inflammation of the peritoneal investment of the spleen; the resulting exudations are converted into the cellular, cellulo-fibrous, or cartilaginous tissues and adhesions, so often found upon spleens that have formerly been tumefied.

Anaemia of the spleen occurs in connection with the above-mentioned reductions in size.