Io8 CHORD ATE ANATOMY 



Leucocytes are permanently nucleated and do not carry hemoglobin. 

 Several types are recognized. (Fig. 105) 



L5rmphocyte: usually small, cytoplasm scanty and usually non- 

 granular, nucleus spherical. 



Large mononuclear leucocyte (monocyte) : more abundant and non- 

 granular cytoplasm, nucleus excentrically placed. 



Polymorphonuclear leucocyte : large, with conspicuous granules in 

 cytoplasm, nucleus indented, lobulated, irregular or separated into two 

 or more parts. Several kinds are distinguished on the basis of the 

 reaction of their granules to anilin dyes. Basophiles have granules 

 which take basic stains; eosinophiles have an afl&nity for eosin, an 

 acid dye; the granules of neutrophiles take both basic and acid dyes. 



Most leucocytes are capable of active ameboid motion. Many are 

 phagocytic. 



Blood plates (Fig. 105) are minute bodies which seem to be proto- 

 plasmic and yet are not nucleated. They probably result from fragmen- 

 tation of cells in bone marrow or elsewhere. They seem to have some 

 relation to the clotting of blood as indicated by the fact that the filaments 

 of fibrin (Fig. 104) tend to radiate from blood plates. 



Lymph resembles blood but lacks erythrocytes and is therefore color- 

 less. The fluids occupying the coelomic spaces and the cavities of brain 

 and spinal cord, the aqueous humor of the eye and the amnionic fluid are 

 all of the general nature of lymph but contain relatively few cells and differ 

 from one another in details of chemical constitution. 



HISTOLOGICAL SPECIFICITY 



In general, histological differences are less conspicuous than the 

 corresponding anatomical differences. Unstriated muscle fibers appear 

 much the same whether they are in the wall of a stomach or of a lung. 

 Nevertheless tissues and cells usually exhibit characteristics which mark 

 them as belonging to a particular organ or animal. The nerve cells 

 of a spinal ganglion differ from the motor nerve cells in the spinal cord 

 of the same animal. Epidermal tissue of a fish differs from that of a 

 reptile. 



It follows, therefore, that the individual tissue cell may, in its visible 

 structure, exhibit characteristics reflecting as many as four grades of 



Fig. 105. — Cells from smear preparation of normal human blood; Wright's stain. 

 In the center: adult red blood corpuscles, blood platelets and a polymorphonuclear 

 neutrophile. At left above: two polymorphonuclear basophiles and two polymorpho- 

 nuclear eosinophiles. At right above: three large and four small lymphocytes. At left 

 below: polymorphonuclear neutrophiles; two of these cells, the uppermost and lower- 

 most of the group, are young, with merely crooked nuclei; the mature cells have multi- 

 lobed nuclei. At right belov/: six monocytes; in the younger cells the nuclei tend to be 

 rounded, in the adult cells they arc horseshoe-shaped, indented or lobed. (From 

 Bremer, "Text-book of Histology'.') 



