THE MAST CELLS 



discovered the mast cells. The strong affinity of the granules for basic dyes 

 and the metachromatic staining reaction enabled Ehrlich to differentiate his 

 Mastzellen from the heterogeneous collection of 'embryonal' or 'plasma' cells 

 described by his teacher, Waldeyer (1875). Granular cells were first seen in 

 the peritoneum of frogs by Von Recklinghausen (1863). Waldeyer, who 

 described and depicted similar cells with refractile granules around small blood 

 vessels, believed them to be precursors of the fat cells which form the outer 

 layer of the perivascular sheath. Ehrlich showed that Waldeyer's granular 

 cells do not contain fat by pretreating the tissues with fat solvents, and that dyes 

 which stain fat leave the granules of mast cells unstained. According to 

 Ehrlich the mast granules represent an albuminous reserve substance for the 

 connective tissues and are the products of differentiation in healthy cells of the 

 fixed mesenchyme. 



Ehrlich then went on to study the staining reactions of the blood cells, 

 laying the foundations of modern haematology on the basis of the specific 

 affinities of the leucocytes for various dyes (Ehrlich, 1891 ; Ehrlich and Lazarus, 

 1898). Here again he encountered cells with basophilic, metachromatic 

 granules, and thus came to recognize two types of mast cell; the first, derived 

 from, and living in the connective tissues (tissue mast cell), the second — the 

 counterpart of the neutrophil polymorph and eosinophil leucocyte — whose 

 origin is in the bone marrow and whose habitat is the peripheral blood (blood 

 mast cell, basophil or mast leucocyte). Not the least of Ehrlich's genius was 

 his intuitive appraisal of the limitations of the experimental methods of his 

 day. His later work on cancer is typical of this. So it was with the mast cells. 

 He made no attempt to apply experimental methods to the problem of their 

 function or to characterize chemically the granule substance. Having described 

 the morphological features of blood and tissue mast cells, he left it to others to 

 elucidate the role of these cells in the organism, concluding his brief introduction 

 (Ehrlich, 1879) with the hope that one day the mast cells would be found to 

 have an interesting function. It is the purpose of this monograph to trace the 

 subsequent story and see to what extent Ehrlich's hopes have been fulfilled. 

 It is an interesting story, and no less interesting in the certainty that the full 

 account has yet to be written. Even now we are in the midst of one of the 

 periodic waves of enthusiasm for the mast cells, and there may thus be workers 

 in many fields to whom an interim account will be acceptable. This is built 

 around the researches of my colleagues and myself in Scotland who have 

 investigated the relationship of the mast cells to tissue histamine. At the same 

 time we have endeavoured to retain something of the wider perspective which 

 appealed so strongly to Ehrlich: that is perhaps the outstanding feature of his 

 undergraduate Thesis which has only recently become available for study 

 (Ehrlich, 1878). 



