194 NORMAL AND PATHOLOGICAL BLOOD 



The trilobed nucleus stains less intensely than the granules. As a rule, 

 the mast cell is about the size of a polymorphonuclear. 



In a differential count of normal blood we find about the following percentages. 



Polymorphonuclears, 65 to 70%, about 5000 per c. mm. 



Small lymphocytes, 20 to 25%, about 1500 per c. mm. 



Large lymphocytes, 5 to 10%, about 500 per c. mm. 



Large mononuclears, i to 2%, about 100 per c. mm. 



Transitionals, 2 to 4%, about 200 per c. mm. 



Eosinophiles, i to 2%, about TOO per c. mm. 



Mast cells, 1/4 to 1/2%, about 25 per c. mm. 



The leukocytes which are found in the peripheral circulation only 

 in pathological additions are: 



1. Neutrophilic Myelocytes. The common type is a large cell 

 with a large centrally placed, feebly staining nucleus. This may be 

 recognized by the difficulty of distinguishing the nucleus from the cyto- 

 plasm, there being no sharp line separating these parts of the cell. They 

 imperceptibly merge into one another. They differ from a large mono- 

 nuclear in that the cytoplasm is distinctly dotted with neutrophile 

 granules and that we cannot make out a distinct line of separation of a 

 slightly irregular or indented nucleus from the surrounding slightly 

 neutrophilic cytoplasm. Cornil has described a very large myelo.cyte 

 with eccentrically placed nucleus and neutrophilic granules. 



Myelocytes are at times found with both basophilic and neutrophilic 

 granules, and may rarely be seen to have all three kinds of granules on a 

 single myelocyte, acidophile, basophile, and neutrophile. 



2. Eosinophilic Myelocytes. These can be distinguished from 

 normal eosinophiles by their possessing a single round nucleus, not 

 bilobed. These myelocytes may be as large as a normal eosinophile, 

 but frequently are no larger than a red cell. 



The neutrophile myelocyte is characteristic of spleno-myelogenous 

 leukaemia, the eosinophile one ofmyelogenic leukaemia. The occurrence 

 of an occasional myelocyte is frequently noted in conditions having a 

 leukocytosis. In diphtheria their presence in numbers is of bad prog- 

 nostic import. Myelocytes are of diagnostic importance in metastases 

 of malignant tumors. 



3. The Irritation Cell of Turck, or Plasma Cell, This cell has a 

 faintly staining, eccentrically placed nucleus, and a dark opaque blue, 

 frequently vacuolated, cytoplasm. They are usually recorded as large 



