l6o NORMAL AND PATHOLOGICAL BLOOD. 



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 100 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 conditions 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 

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

 They imperceptibly merge into one another. They differ from a 

 large mononuclear 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 sur- 

 rounding slightly neutrophilic cytoplasm. Cornil has described a very 

 large myelocyte 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 

 leuka&mia, the eosinophile one of myelogenic leukaemia. The oc- 

 currence of an occasional myelocyte is frequently noted in conditions 

 having a Jeukocytosis. In diphtheria their presence in numbers is of 

 bad prognostic import. Myelocytes are of diagnostic importance in 

 metastases of malignant tumors. 



