Chapter II 

 THE MAST CELL IN EVOLUTION 



DURING the sixty years which followed Ehrlich's discovery, research 

 on the mast cell was almost entirely histological. Controversies arose 

 but their resolution for the most part merely emphasized the soundness 

 of Ehrlich's original work. 



Thus Ranvier (1890) described his 'clasmatocytes' — cells which cast off 

 (' comatose') fragments of protoplasm; but it is clear from Ranvier's own 

 descriptions that many of the cells which he originally recognized as clasmato- 

 cytes are tissue mast cells. In the newt and salamander especially the mast cells 

 are exceptionally large and irregular in shape and are easily damaged during 

 preparation of the tissues. Moreover, Ranvier used a watery fixative ( 1 per cent 

 osmic acid), a watery stain (violet 5B) and a watery mountant (glycerine) 

 whereby the granule substance rapidly diffuses from the cytoplasm. Using 

 the same stain and a more adequate fixative, Raudnitz (1883) had already 

 successfully demonstrated mast cells in man. The situation was finally clarified 

 by Jolly (1900) who clearly distinguished mast cells from clasmatocytes in 

 mammals and showed that the huge arborizing cells in amphibia are the tissue 

 mast cells of these species. 



The use of a watery technique likewise led Pappenheim and his school to 

 assert that mast myelocytes are lacking in the bone marrow of the rabbit and 

 in the marrow of patients with myeloid leukaemia, thereby implying that the 

 numerous blood mast cells in both are derived from precursors in the tissues. 

 This misconception persisted until Maximow (1913) and Ringoen (1919) 

 conclusively re-established Ehrlich's views and again stressed the extreme 

 water-solubility of the mast granules in certain species (Kanthack and Hardy, 

 1894). Not all mast granules are so readily soluble; the mast granules of the 

 rat are surprisingly resistant to water (Paff and Mergenthaler, 1955). It will 

 be shown later that once the limitations of a watery technique for mast cells 

 are appreciated the method can be used to yield information concerning the 

 physiological function of the cells. 



In only one respect did Ehrlich's early work fail to find complete acceptance 

 later. It will be recalled that Ehrlich's classification and nomenclature of the 

 granular leucocytes rested on the ' specific affinities ' of the granules for various 

 dyes. As the scope of the search for mast cells widened, it became increasingly 

 apparent that in many lower organisms not only are the mast granules frequently 

 non-metachromatic, but that, at least during certain phases of their life history, 

 they may even be acidophilic. The significant homology for the mast cell is 



