Chapter III 

 THE BLOOD MAST CELL, BASOPHIL OR MAST LEUCOCYTE 



EXAMINATION of suitably fixed and stained preparations of the blood 

 of vertebrates shows a minority of the leucocytes to contain basophilic 

 metachromatic granules in their cytoplasm. These are the blood mast 

 cells or mast leucocytes and have been described in reptiles (Loewenthal, 1930; 

 Ohuye, 1952), fishes (Michels, 1923; Loewenthal, 1930), birds (Forkner, 1929) 

 and in many other vertebrate species (Ponder et al, 1928, 1929; Knoll, 1932). 

 The chief morphological features which distinguish the mast leucocyte from 

 the tissue mast cell are its smaller size, more rounded shape, its relatively scanty 

 cytoplasm and the decidedly polymorphous character of its nucleus (Harris, 

 1900), differences which the cells retain even though they leave the blood stream 

 and enter the tissues (Zimmermann, 1908; Ringoen, 1923). Like the tissue 

 mast cells, the mast leucocytes were first clearly described by Ehrlich. 



It was not Ehrlich's habit to linger over his discoveries. In his 

 ' Farbenanalytische Untersuchungen ' of 1891 — forerunner of modern texts on 

 haematology — the chapters on tissue mast cells and on eosinophil leucocytes are 

 already handed over to his colleagues, Westphal and Schwartze. Meanwhile 

 Ehrlich (1891, p. 58) had discovered basophilic granular cells in human blood, 

 though so far only in myeloid leukaemia. Nevertheless, with characteristic 

 insight he at once perceived that the blood mast cells in higher vertebrates 

 are true leucocytes stemming from precursors in the bone marrow. By the 

 time that his textbook came of 1898 to be revised (Ehrlich and Lazarus, 1909) 

 the evidence for the myeloid origin of the blood mast cell was complete (Jolly, 

 1900). 



It was thus all the more curious that the rival school of haematology led 

 by Pappenheim should criticize Ehrlich's views on blood mast cells without 

 checking the findings by the use of Ehrlich's own methods. As Michels (1938) 

 points out, the controversy which developed hinges on the interpretation of 

 findings obtained with inadequate histological techniques. Unfortunately 

 for Ehrlich's critics the two situations in which blood mast cells are common, 

 namely the blood of the normal rabbit and leukaemic blood in man, are 

 precisely those situations in which the mast granules are most water-soluble, 

 lending themselves readily to the production of artifacts during fixation and 

 staining (Westphal, 1891; Michaelis, 1902; Piette, 1955). 



We have already reviewed the evidence of Jordan (1926) who, nearly twenty 

 years later, argued in favour of the degenerative character of the tissue mast 

 cell. With even less justification Pappenheim (1909) and his contemporaries 



b 17 



