Fine structures of the neutrophils obtained by hemolytic method from the peripheral blood of 5 clinically normal sheep were examined by an electron microscope. The results thus obtained were summarized as follows. 1) The nuclei of the cells showed one to several nuclear lobes, and the nuclei with 2 to 4 nuclear lobes were observed most commonly. 2) The nuclear lobes of the cells showed a clear maculous appearance with two distinct densities, one light and the other dark, according to the amount of the chromatin condensation. 3) The specific granules were classified into two types on the basis of their electron density, the one with high density and the other with less density. 4) Most of the specific granules had the homogeneous interior without any internal structures. However, some of them had internal structures such as a middle plate-like substance, round defects with or without vacancy, sacs with small vesicles and clear spaces between the membrane and matrix of the granules. 5) A small number of mitochondria measuring 0.3 by 0.7μ on the average, Golgi complex, a number of smooth-surfaced and a few rough-surfaced endoplasmic reticulum, and a few large round or oval bodies supposed to be lysosome were observed in the cytoplasm
