MAST CELL IN EVOLUTION 



the tissue mast cells. It will be helpful to keep this genealogical background 

 in mind when the apparently capricious distribution of mast cells in higher 

 oiganisms is under consideration. 



Detailed distribution of mast cells in vertebrates 



Lower vertebrates. In lower vertebrates, production of coarse granulo- 

 cytes is for the most part restricted to certain well-defined sites, notably gut, 

 mesentery, subcutaneous and intermuscular tissue, liver, spleen, kidney, 

 gonads, perivascular tissues generally, lungs (when present) and to a lesser 

 extent pancreas and even skull (Drzewina, 1905; Michels, 1923). 



Alimentary tract. In the alimentary tract of Ichthyopsida (fishes and reptiles) 

 the 'lymphoid tissue' (Drzewina, 1905) forms an almost continuous sheath 

 between mucous membrane and muscle, a region which corresponds to the 

 location of the Peyr's patches and isolated lymphoid nodules in man. Drzewina 

 failed to find granulocytes in the alimentary lymphatic tissue of carp though 

 they have been described there by Al-Hussaini (1948). In the carp coarse 

 granulocytes are particularly abundant in the perivascular tissues and serous 

 membranes, especially mesentery (Michels, 1938). Greene (1912) found in the 

 gut of the King salmon a layer of coarse granular cells so dense that he refers 

 to it as the 'stratum granulosum'. However, Arvy (1955a) points out that 

 apparently similar cells in the trout more closely resemble the granular cells 

 of the exocrine pancreas; they are decidedly more acidophilic than basophilic 

 in their staining properties. Numerous coarse granulocytes were seen in the 

 gut of other salmonoids by Bolton (1933) who has no hesitation in calling them 

 'mast cells'. Migratory activity and concomitant change in staining properties 

 of the coarse granulocytes in teleosts were clearly recognized by Al-Hussaini 

 (1949). Duthie (1939) shows coarsely granular basophils migrating towards 

 mucosal and serous surfaces: as the surface is reached the now acidophilic 

 granules become orientated in a manner which suggests (p. 40) 'a discharge of 

 the granules on to the surface of the epithelium'. It will be seen later that there 

 is evidence for limited migratory activity of perivascular mast cells towards 

 mucosal and epithelial surfaces in higher vertebrates (Riley, 1953a; Arvy, 

 1956a; McGovern, 1956). Typical mast cells have been described in the gut 

 of various Batrachians (anurans and urodeles) by Arvy (19556). 



Heart and blood vessels. As long ago as 1857 Leydig described a richly 

 cellular sheath surrounding the mesenteric vessels in several teleostean (bony) 

 fishes. The regular occurrence of haemopoietic tissue in this situation is well 

 seen in certain 'ganoids' (e.g. sturgeon). Drzewina (1905) describes such a 

 tissue clothing the heart of the sturgeon and extending along its blood vessels; 

 Ohuye and Ochi (1954) observed a similar genesis of basophilic granulocytes 

 in a urodele, the Japanese newt. According to Drzewina the formative tissue 



