A contribution to the cytology of the spleen: the Romanowsky-stained bovine spleen smear

A. The essence of this work has been to provide a systematic description of the elements and an explanation of the chief artefacts of the bovine spleen smear together with an atlas-guide. Hence no general summary is possible. But attention should be drawn especially to the following points: (1) The most active phagocytosing cell of the bovine spleen is a lymphocyte, termed a a phagocytosing lymphocyte by us, and doubtlessly corresponding to the macrophage, clasmatocyte (smaller type), " splenocyte", and even perhaps the "monocyte" of some authors. (2) Phagocytosis in the spleen includes erythrocytes, leucocytes, and blood platelets. Thrombophagocytosis is a very extensive phenomenon in the spleen of bovines, only to be appreciated by the use of refined technique. (3) Monocytes are of infrequent occurrence. They are derived from reticulum cells, through an intermediate stage which may be spoken of as a monoblast; but not from lymphocytes. (4) Although ultimately in aged plasma cells distinction between the two types is impossible, plasma cells may be derived from reticulum cells and monocytes, as well as from lymphocytes. (5) The sinus-lining cells have a distinct morphology, especially in their nuclear characters and their content of iron-containing pigment "haemofuscin" at both poles of the nucleus. No evidence of phagocytic or cytogenic abilities could be demonstrated. (6) The Schweigger-Seidel sheath cells are described in smears and details of their morphology are provided. The view is advanced that they are of the same nature as reticulum cells as far as reticulin production, mobilisation and phagocytosis are concerned, although differing morphologically from them in the resting state. (7) The nature of certain puzzling epithelial-like elements in routine spleen smears was cleared up by the finding that they are mesothelial cells of the splenic serosa. B. Besides the cells already mentioned, the following elements are briefly described as they appear in the Giemsa-stained spleen smear: endothelial cells, smooth muscle cells, mast cells, eosinophils (their youthful appearance and the presence of Liebreich's alpha 1 granules are commented upon), neutrophils (mention has been made of their macrophagocytic activity), megakaryocytes, erythrocytes, as well as blood platelets, reticulin, collagen and elastic fibres, haemosiderin and "haemofuscin". C. The status and genesis of artefacts have been discussed. Theoretically a distinction can be drawn between artefacts produced by making and subsequent manipulation of preparations (exogenously produced artefacts), artefacts conditioned by states of senescence or degeneration of the cells (endogenously conditioned artefacts), and artefact-like appearances resulting from physiological processes; in practice this distinction is not always possible. The artefacts described include cellular distortion, cytoplasmic fragments and free cytoplasmic constituents, naked nuclei, distorted and smudged nuclei, various contaminants, stain deposit, etc. The effects of autolysis have also been mentioned. D. Problems of cell derivation and terminology have been discussed. E. In view of the phagocytic powers of lymphocytes and neutrophils and the inactivity of the sinus endothelium in this respect, a critique is offered on the R.E. system, and the proposal is put forward that the name be changed to "Phagocytic System".