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TEXT-BOOK OF PHYSIOLOGY. 



(See Fig. 113.) The protruded process, the pseudopod, can also attach itself 

 to some point of the surface on which it rests, and then draw the body of 

 the corpuscle after it. By a repetition of this process the corpuscle can 

 slowly creep about and change its position in reference to its environment. 

 By \irtue of these amoeboid movements the corpuscle can appropriate small 

 particles of pigment, such as indigo or carmine, and after a short time elimi- 

 nate them from various parts of the surface. It is also capable of thrusting 

 a process into and through the wall of the capillary vessel, after which the 



remainder of the corpuscle follows (Fig. 114). 

 This continues until the corpuscle is outside the 

 vessel and in the lymph-space, where it resumes its 

 original shape and movement. This process is best 

 observed in inflammatory conditions, when the 

 blood has come to rest and the vessels are occluded 

 with both red and white corpuscles. To this pas- 

 sage of the white blood-corpuscles through the 

 capillary wall the term diapedesis is given. The 

 movements of the white corpuscles are increased by 

 a rise in temperature up to 40 C., beyond which 

 they cease, owing to the coagulation of the cell- 

 substance. A low temperature also arrests the 

 movements. Induced electric currents also cause 

 contraction and death of the cell. Moisture and 

 oxygen are necessary to their activity. From their 

 similarity to lower organisms the white corpuscles 

 may be regarded as independent organisms living 

 in the animal fluids, just as the amoeba lives in its 

 natural liquid medium. 



Varieties of Leukocytes. A detailed study of 

 the blood with the aid of the triacid staining fluid 

 of Ehrlich or any of the various eosin and methy- 

 lene-blue stains, reveals the presence of five distinct 

 varieties of leukocytes and transitional forms which 

 may be classified as follows: 



i. Small lymphocytes, so called from their resem- 

 blance to the corpuscles of the lymph-glands, 

 consisting of a deeply staining and relatively 

 large round nucleus, encircled by a narrow rim 

 of cytoplasm. Found in from 20 to 25 per cent, of all leukocytes. 

 They vary in size from 0.004 to 0.007 mm - 



2. Large lymphocytes or hyaline cells, which are believed by some to represent 

 the preceding type at a later stage of development, by others to have an 

 independent origin, are distinguished by a round or ovoid nucleus 

 staining faintly and surrounded by a relatively larger layer of cytoplasm 

 than is seen in the small lymphocyte. The large lymphocyte is present 

 to the extent of from 4 to 8 per cent. Transitional forms, usually pre- 

 sent from i to 2 per cent, are very much like the large lymphocyte in 

 appearance and size, with the exception, however, that they possess a 

 cresentic or indented nucleus and have a somewhat greater affinity for 



FIG. 114. SMALL VES- 

 SEL SHOWING VARIOUS 

 STAGES IN THE DIAPEDESIS 

 OF LEUKOCYTES. (G. Bach' 

 man.) 



