The following general description of the capsule, trabeculæ, and sheaths of the splenic vessels is based on the examination of the spleen of the Kitten.
The Tunica serosa consists of a single layer of somewhat thick endothelial cells, which is continuous with the peritoneal lining of the body cavity, and in addition of a thin layer of very finely fibrillated connective tissue that lies immediately subjacent to the endothelial layer.
The Tunica propria differs from a true capsule in that it blends along its whole under surface with the splenic parenchyma, from which it cannot be detached without tearing the splenic substance.