72 



On the Granular Leucocytes. 



[Nov. 28, 



mitosis of all leucocytes except the largest granular forms. The 

 lymphocyte develops into the small hyaline forms, from which the 

 three groups branch off. 



I. The cells may remain Hyaline, and attain their maximum 

 development in such cells as the la,rge phagocytes of the alimentary 

 canal or the giant-cells of bone marrow. In this case they remain 

 sluggishly amoeboid, their centrosomes are very evident, and the 

 cytomitoma and microsomes, while visible, are not easily made out. 



II. In the Acidophile group are included the so-called neutrophile 

 and amphophile cells, which are really oxyphile, and the eosinophile 

 or coarsely granular cells. In the transition forms from the small 

 hyaline cells to the oxyphiles the mitoma of the cell-body becomes 

 more visible, and it is this rather than the presence of granules which 

 gives rise at first to the finely granular appearance. The granules 

 are simply the microsomes of the mitoma. In the transition forms 

 between the oxyphile and eosinophile cells some of the microsomes 

 become larger and take up acid dyes and iron-haematoxylin better 

 than others, and when the large eosinophiles are reached the threads 

 of the mitoma have become thicker, and also take up iron-haema- 

 toxylin. The microsomes in the eosinophiles vary greatly in size ; 

 they are arranged subradially, with the largest microsomes usually at 

 the periphery. In this group the centrosomes are well seen, better 

 in the eosinophiles than in the oxyphiles. 



III. The cells of the Basophile group vary immensely in size and 

 shape. The nucleus is generally ellipsoidal, except when the cells 

 are actively amoeboid, probably because the cell-body is usually 

 relatively large. As the cells increase in size the amount of basi- 

 chromatin in the nucleus becomes increased out of proportion to the 

 size of the nucleus. This has no relation to mitosis, which has only 

 once been observed in these cells. The centrosomes can be seen 

 fairly easily in the smaller rounded forms. In the larger forms 

 they are difficult to make out, and it seems possible that there may be 

 several subordinate centrosomes. These cells are derived from the small 

 hyaline forms by an increased visibility of the mitoma, and an 

 increase in size of the microsomes, which are at first usually very 

 irregular in size, and do not exhibit metachromasia with methyl- 

 blue. As the cells become larger, so generally do the granules; they 

 become more uniform, but are never all quite of one size. Meta- 

 chromasia becomes more constant, and the mitoma more evident, 

 especially in those cells which are moving, or which are greatly 

 branched. The staining of the microsomes is never quite the same 

 as that of the nuclear chromatin. 



The granules of leucocytes are therefore not products of the meta- 

 bolic activity of the cell embedded in a structureless protoplasm, as 

 was hitherto supposed, but represent an altered condition of the 



