88 



a few rare myelocytes and leucocytes 

 may also be seen. 



Under a strong power the study of 

 the parenchyma revealed the followmg 

 facts: 



Great scarcely, or almost complete 

 disappearance of the polymorphonuclear 

 leucocytes is to be seen. 



Cells with the appearance of lym- 

 phocytes are particularly abundant 

 (Fig. 4, Piale 19); tliese cells appear 

 isolated and never form groups of more 

 üian 2-3 cells. 



Besides the lymphocytes, which, in 

 certain fields appear to be the domina- 

 ting element, myelocytes are to be seen. 



Some myelocytes show a nucleus 

 well-slained by haemaloxylin, very often 

 apparently two-lobed. 



Some myclocylcs possess two circu- 

 lar nuclei of unequal si/.e; agglomera- 

 tions of -1 and more cells are not rare; 

 each cell shows, then, a two-lobed nu- 

 cleus or possesses two spheric nuclei 

 always of une |ual size (forms of division 

 of the myelocytes). 



Liesidcs the above described myelo- 

 cytes olhcr not uncommon ones show 

 dilit'ienl lesions. In somo, the nucleus 

 ajipcars frankly stained, in a diffuse 

 way, like tlie shadowing of a normal 

 nucleus (caryolysis); ia otheis. the nu- 

 cleus is reduied to a black-coloured con- 

 denseil mass, or to small sphe ic mas- 

 ses (3-")) oí unequal si/.e, strongly stai- 

 ned (caryorrhe.iis and ptjcnosia'). 



The volume of almost all the fat- 

 cells is reduced as compared with a 

 fat-cell of normal bone marrow (Fig. 3, 

 Piale 68). 



The nucleus occujjies a very much 

 more central posilion than it would in 

 a normal lal-ceil (Fig. 4, Plate GS); it- 

 is never pertetlly central but always 

 slightly e\ienlric also more volumaious 

 than in normal lal-ceils, ovoid in shape, 

 and poor in chromatin. It occupies a 

 zone of protoplasm with a reticular 

 structure. In the meshes of the reti- 



culum, round the nucleus, are s^en lif-^ 

 tie vacuoles. In the peripheric part of 

 the protoplasm the vacuoles a''e bigger, 

 separated by fine septa from t)ie reticu- 

 lum. 



In the immediate neighbourhood 

 of the fat-cell a substance of uaiformly 

 rose colour is seen in preparations stained 

 by ha^maloxylLi-eosin (fluid transudate 

 of cedema). 



It is not possible to find a mega- 

 locaryocyte with a normal appearance; 

 these cells are reduced in number and 

 have diiierent appearances. 



In one case, the volume is appro- 

 ximately that of a normal megalocaryo- 

 cyle. The nucleus shows the characteris- 

 tic configuration. It stains, howexer, very 

 little by hematoxylin, looking like a 

 shadow of dark blue colour, biüier than 

 a normal nucleus; no fine details of 

 structure are seen, in it, the mass having 

 on the contrary, a homogeneous and uni- 

 form appearance. 



The protoplasm is made up of mi- 

 nute, densely grouped granulations, of 

 uniorm, si e, frankly coloured rose-red 

 by the hicmaloxylin-eosin and pale blue 

 by GlEMSA's fluid process. 



In another, aspect, the volume of 

 the cell is enormously reduced, some- 

 times lo one half the normal size. The 

 megalocaryocyte has in this case the 

 dimensions of a myelocyte (Fig. 5, Plate 

 PJ). 



The nucleus appears as a condensed 

 mass, strongly slained in very deep blue; 

 it does not show fine structural details. 



The granular protoplasm forms 

 round the condensed nucleus a more 

 or less narrow zone; it shows the gra- 

 nular structure described above. 



The lesions of the bone-marrow 24 

 hours after the commencement of iin- 

 munisalion are, therelore: 



iy aplasia (reduction of the number 



of cells y . 



2) relative abundance of cells with 

 the morphology of lymphocytes which 



