THE MAST CELLS 



bears a striking resemblance to the mammalian lymph node : however, it also 

 gives rise to coarse granulocytes, and these, in the sturgeon, may contain both 

 basophilic and acidophilic granules within the cytoplasm of the same cell. This 

 is a disturbing state of affairs to one brought up strictly in the Ehrlich tradition 

 of a cytological nomenclature based on specific affinities. Drury (1914) 

 observed typical eosinophils free in the peritoneal fluid of bony fishes but no 

 basophils, since 'they do not migrate from their normal place of occurrence, 

 around the blood vessels, amongst the teleostean fishes'. It will be emphasized 

 later that perivascular tissues are outstanding sites for the formation of mast 

 cells in mammals. 



Kidney and gonads. In Ichthyopsida the kidney tubules are embedded in 

 a mass of reticular lymphoid tissue from which develop cells with amphophil, 

 basophil and acidophil granules, the granules of basophils usually being coarser 

 than the rest (Drzewina). This tissue in a ganoid, Polyodon spathula, was 

 extensively studied by Downey (1909) who discusses the evidence for secretion 

 by the granular cells. Of the three main types recognized by Downey, the cells 

 with basophilic granules eventually become metachromatic and finally dis- 

 integrate through the diffusion of the metachromatic material into the cytoplasm 

 and the formation of multiple vacuoles. Blood formation is also active, in the 

 disproportionately large gonads of fishes. Jordan (1926) describes coarse 

 granulocytes with basophilic and eosinophilic granules in the gonads of 

 elasmobranchs (e.g. skate). 



Liver. The liver provides an illuminating example of the minor differences 

 in distribution of the 'lymphoid tissue' in a single organ within a group of 

 closely allied animals. According to Drzewina lymphoid tissue is greatest in 

 the livers of urodeles, least in many frogs and toads. It is absent from the livers 

 of adult birds and mammals though present there during embryonic life 

 (Dantschakoff, 1916). In some species of Ichthyopsida the simple perivascular 

 cuffs, as in ganoids, undergo hypertrophy cortically or centrally in the liver 

 to form comparatively large masses of tissue. Oppel (1889) was the first to 

 describe the thick 'couche corticale' of lymphoid tissue beneath, but not 

 attached to, the hepatic serosa of the primitive urodele 'Proteus anguineus'. 

 Drzewina found a similar arrangement in the liver of the terrestrial salamander 

 and believes this layer to be made up of the fused perivascular cuffs of 

 numerous cortical blood vessels. Similar vagaries in distribution will be 

 noted when the location of mast cells in the livers of higher vertebrates is 

 examined. 



There is some experimental evidence that the extent and activity of the 

 lymphoid tissue of Ichthyopsida are influenced by the nutritional state of the 

 organism and that a compensatory increase in activity of this tissue follows 

 splenectomy (Drzewina, 1905; Ohuye and Ochi, 1954). 



10 



