2Q2 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



(see p. 254), using the emulsion exactly as if it were blood. 

 This may be stained by Jenner's method (see p. 260) or fixed 

 and stained subsequently. Any of the fixing and staining 

 methods described for blood may be used, but I prefer to 

 allow the film to dry, fix with saturated solution of perchloride 

 of mercury for a minute or two, wash, stain in carbol thionin 

 for two minutes, wash, dry and mount. This renders every- 

 thing very distinct except (sometimes) the nucleoli of the 

 endothelial cells and the granules of the polynuclears. Where 

 the latter have to be inquired into (which rarely happens) the 

 film should be fixed with heat and stained with triacid (see 

 p. 260). 



CELLS MET WITH IN EXUDATES. 



Leucocytes derived from the blood are present in the 

 majority of exudates, and in most cases they are of ordinary 

 appearance, and readily recognized from the descriptions 

 already given. The polynuclears, however, may undergo 

 various forms of degeneration, and become so altered that 

 their nature may be difficult to make out. This occurs mainly 

 in old exudates, especially in pus. There are three chief 

 forms : 



(a) In some cases the nucleus undergoes fragmentation 

 i.e., breaks up into several isolated masses, so that the cell 

 becomes truly polynuclear (Plate IX., Fig. 2, where the 

 ingested leucocytes are fragmented). These masses stain 

 deeply, and the cell is easy to recognize, but it often happens 

 that the fragments of the nuclei are set free, and may then 

 be mistaken for small lymphocytes. If a specimen be stained 

 by the triacid stain, they may often be distinguished by a few 

 granules which remain adherent to the nucleus. 



(b) Dropsy of the nucleus, which converts it into a large 

 circular or reniform mass which stains faintly. In this case 

 the cell resembles a large lymphocyte, large hyaline leucocyte, 

 or myelocyte. It may usually be distinguished from the 

 former by the presence of granulations, and the latter is not 

 known to occur in exudates except in cases of leucocythaemia. 

 It is occasionally found in serous exudations complicated 

 by fractures of bones (ribs, etc.), the marrow-cells escaping 

 into the fluid. Such exudates naturally contain blood, 

 normoblasts, etc. 



