ARNETH INDEX 1 93 



1. Polymorphonuclear Leukocytes. -This cell normally constitutes 

 the greater proportion of the leukocytes. It is an amoeboid, actively 

 phagocytic cell, about 10 or 12 /* in diameter, and is the microphage of 

 Metchnikoff. Bacteria are actively phagocytized by this cell, and it is 

 the cell concerned in determining the opsonic power of blood to various 

 bacteria. It has fine lilac granules which are termed neutrophilic (ep- 

 silon granules). The single nucleus is rich in chroma tin and is lobose 

 like the kernel of an English walnut; frequently it resembles the letter 

 z. These cells are derived from the neutrophilic myelocytes of the bone 

 marrow. It is in these cells that the glycogen, or iodophil granules, 

 appear in certain suppurative conditions. 



A great deal of interest has been aroused in the so-called Arneth index, espe- 

 cially in connection with prognosis in tuberculosis and various pyogenic infections. 

 The basis of the test is that polymorphonuclears showing only one or two nuclear 

 nodes are considered immature while those having three, four or five nuclear nodes 

 possess greater phagocytic power. 



A normal distribution is as follows: 



Class I. Class II. Class III. Class IV. Class V. 



6% 35% 42% 16% i% 



To obtain the Arneth index add to the sum of the polymorphonuclear percent- 

 ages of cells containing one and two nodes one-half of the percentage of those having 

 three nodes. In the above we have as the normal Arneth index 62. 



In an advanced case of tuberculosis we might have an index of 79, obtained as 

 follows : 



Class I. Class II. Class III. Class IV. Class V. 



20% 45% 28% 6% i% 



2. Eosinophile Leukocytes. These are very striking cells with 

 coarse granules staining brilliantly pink, the eosinophile, oxyphile, or 

 acidophile granules (alpha granules of Ehrlich). The cells are a little 

 larger than the polymorphonuclears. The normal eosinophile is to be 

 distinguished from the eosinophilic myelocyte by its possessing two 

 distinct lobes in the nucleus. At times we find three nuclei. The 

 nucleus of the myelocyte is round. The eosinophile is the cell so 

 frequently increased in infections by intestinal animal parasites. 



3. Mast Cells. These also have coarse granules, but they stain a 

 deep violet blue. Hence they are basophile granules (gamma granules). 

 In fresh blood these granules do not show up very well, thus they can be 

 distinguished from the highly refractile granules of the eosinophile. 



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