DIFFERENTIAL LEUCOCYTE COUNT 213 



much value in pneumonia, as it does not occur till after the crisis, 

 but in chronic suppurative diseases, etc., a gradual increase in 

 the eosinophiles often heralds improvement. Neusser holds that 

 the same is true in tuberculosis also. 



EosinopkiU Myelocytes. — The presence of these is practically 

 diagnostic of myelogenous leucocythaemia. 



Mast Cells. — These only occur in fractional percentages in any 

 disease, except myeloid leucocythaemia, where 5 or 10 per cent, is 

 common ; this is perhaps the most definite, constant, and readily 

 recognised sign of the disease. The large forms, with circular or 

 kidney-shaped nuclei, are practically only seen in this condition. 



Morphological Changes in the Red Corpuscles. 



Normal red corpuscles (Plate VIII., Fig. i) hardly need 

 description, and the practitioner can readily make himself 

 familiar with their appearance. They are strongly oxyphile, 

 staining pink with the eosin in Jenner's stain, and with acid 

 fuchsin in the triacid. It is especially important to become 

 familiar with their size, since modifications in this respect are 

 very important in the diagnosis of certain forms of anaemia. 



Abnormal Forms of Red Corpuscles. 



Two great classes are to be recognised — those which retain 

 the characters of a normal red corpuscle, in that they have no 

 nuclei, and those which resemble the embryonic corpuscles in 

 being nucleated. The former, where they have special designa- 

 tions, have names terminating in -cyte (microcyte, megalocyte, 

 etc.j based on the type of the normal corpuscle, which is called 

 erythrocyte, xanthocyte, or normocyte, convenient terms that 

 have never gained wide currency), whilst the nucleated forms 

 have names ending in -blast. 



Abnormal Non-nucleated Forms (-cytes). 



1. Microcytes (Plate VIII., Fig. 4) are red corpuscles which are 

 decidedly below the normal in size, but are otherwise normal. 

 They are indications of anaemia, but, as they may occur in any 

 severe anaemia, and do not serve to indicate its type, their recog- 

 nition is not a matter of much importance. 



2. Megalocytes or Macrocytes (Plate VIII., Fig. 5).— These are 

 large corpuscles, and the name should be restricted to forms 



