In general, heterophils
tend to be round, although their shape may be
distorted, and have a mean diameter of 8.8 μm. Peripheral
pseudopodia and/or lobopodia may occasionally be
noted morphologically. Heterophil size tends to be uniform
for each species of bird, although slight species variations
may be noted morphologically (Maxwell, 1973).
Laboratory technique in preparation of the blood film
may also be a factor in heterophil size variability (Roberts
and Maxwell, 1993).
The nucleus of the mature heterophil is lobed (two
to three lobes), with coarse, clumped, purple-staining
chromatin. The nucleus is often partially hidden by the
cytoplasmic granules.
The cytoplasm of normal mature heterophils appears
colorless and contains granules that stain an eosinophilic