53 



Observations on the Life-History of Leucocytes. 



By C. E. Walker (Assistant-Director of Cancer Eesearch Laboratories, 

 University of Liverpool). 



(Communicated by C. S. Sherrington, F.R.S. Received January 9, — Eead 



January 18, 1906.) 



[Plates 7—10.] 



In presenting this preliminary communication it is necessary to explain 

 that the term leucocyte is used in the widest sense, and is intended to include 

 all the wandering nucleated cells and their immediate ancestors. After many 

 endeavours to make the observations here recorded compatible with the 

 current classification of these cells, it has been found imperative to use a 

 term that will include them all, and, at any rate in most cases, to put aside 

 for the moment the question as to which particular kinds of leucocyte are 

 being dealt with. 



The tissues used have been chiefly bone-marrow, lymphatic glands and 

 spleen, but the leucocytes in various other tissues and the free leucocytes in 

 the blood have also been examined. Most of the work has been clone with 

 material derived from the guinea-pig and the rat, but tissues from man, 

 rabbit, mouse, crocodile, frog, Triton and Axolotl have also been used. In 

 every case the tissues have been normal and, with one exception, derived 

 from adult or nearly adult animals, the one exception being the testis of the 

 early embryo of the guinea-pig. 



In examining a section of bone-marrow one of the most striking, constant 

 and frequent objects met with is the giant-cell or myeloplax. In the 

 myeloplaxes there is, as a rule, an appearance of amitosis in the nucleus or 

 nuclei (see fig. 1). 



Occasionally, however, a myeloplax is found in which mitosis is taking 

 place, and in such cases the mitotic figure is pluripolar but otherwise of the 

 somatic type (see fig. 2). A further search shows that myeloplaxes with 

 the chromatin of the nuclei in the ordinary somatic spireme form are not 

 uncommon (see fig. 3). On the other hand, it is seen that the majority of the 

 myeloplaxes divide amitotically. A portion or portions of the cell containing 

 one or more nuclei are then separated off (see fig. 4). 



Following the cells thus produced, one is forced to conclude that many of 

 the smaller cells in the bone-marrow are derived from them. Among these 

 are the cells commonly known as " polymorphic nuclear leucocytes " and many 

 of the cells containing a single and more or less rounded nucleus (see fig. 5). 



