Manual of Human Embryology Volume 2

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...first at one or several points in the cytoplasm, and increase gradually in number until they occupy the whole body of the cells, with the Flo. 363.--Finely granular (neutrophile) leucocyte with compact nucleus, a so-called myelocyte. From the circulating blood of a healthy adult. (After Weidenreich.) exception of the immediate neighborhood of the centrosome. Meanwhile the colorability of the intergranular substance diminishes. In a human embryo of three and one-half months the majority of "leucoblasts" in the bone medulla are without granules, but both neutrophile and eosinophile cells are present. During the fourth and fifth months the finely granular cells become more numerous. 2, B. The coarsely granular leucocytes (eosinophiles) develop at the same time as the finely granular, but are morphologically wholly different. The original round nucleus becomes eccentric and kidney-shaped, then more slender and longer, and bends around the centrosome, which takes a central position. Up to this point of its development it can scarcely be distinguished from the nucleus of the finely granular cell, but finally it assumes its permanent shape by forming two lobes (Fig. 364), which are united "The fine research of M. Heidenhain upon the leucocytes of Salamandra (Festschr. f. Kolliker, 1892, p. 138) must be regarded as the starting-point of our knowledge of the centrosome of leucocytes. by a strand varying in width and length. As a rule, the lobes are of unequal size, but the inequality is seldom striking. The lobes are in general round or oval and occasionally pear-shaped. They usually have very regular contours, but occasionally one sees a small projecting hump. The length of the uniting strand is very variable. Nuclei occur with shapes which do not ex...