22 THE ESSENTIALS OF HISTOLOGY. 



4. At the beginning of the lesson collect a drop of newt's blood into a fine 

 capillary tube, seal the ends of the tube, and mount in it a drop of oil of 

 cedar or Canada balsam. Towards the end of the lesson examine it again to 

 see white corpuscles emigrating from the shrunken clot (see fig. 19). 



5. To obtain a specimen showing white corpuscles in amoeboid condition, 

 make a preparation of newt's blood, mixed with salt solution, and set it aside 

 for ten minutes. By this time the corpuscles will be freely amoeboid, and 

 will probably show well-marked pseudopodia. To fix them in this condition 

 let a jet of steam from the spout of a kettle play for two or three seconds 

 upon the cover-glass. The heat instantaneously kills the corpuscles, and 

 they are fixed in the form they presented at the moment the steam was 

 applied. They may now be stained by passing dilute hsematoxylin solution 

 under the cover-glass, and this may be replaced by dilute glycerine, after 

 which the cover may be cemented and the preparation kept. 



The amoeboid phenomena which are exhibited by the protoplasm of 

 the colourless blood-corpuscles consist, in the first place, of spontaneous 

 changes of form, produced by the throwing out of processes or pseudo- 

 podia in various directions. When first thrown out the pseudopodia are 

 composed of hyaloplasm alone, and they are probably produced by a 

 flowing of the hyaloplasm from out the meshes of the protoplasm 

 (see p. 2). If the corpuscle is stimulated, either mechanically, as by 

 tapping the cover-glass, or electrically, the hyaloplasm is withdrawn 

 again into the spongioplasm, and the pseudopodia are thereby retracted^ 

 the corpuscle becoming spherical. A change of form, caused by the 

 protrusion of the pseudopodia, may, when active, be followed by changes 

 in place or actual locomotion (migration) of the corpuscle. When a 

 pseudopodiuin, or the external surface of the corpuscle, comes in contact 

 with any foreign particle, the hyaloplasm tends to flow round and 

 enwrap the particle, and particles thus incepted may then be conveyed 

 by the corpuscle in its locomotory changes from one place to another. 

 This property appears to play an important part in many physiological 

 and pathological processes. 



It is probable that particles of organic matter which are taken up by 

 the pale corpuscles may undergo some slow process of intracellular 

 digestion within their protoplasm. 



The processes of the granular corpuscles are generally quite clear at 

 first, and the granules afterwards flow into them. 



The migration of the colourless corpuscles from the blood-vessels into 

 the surrounding tissue, or from a blood-clot into the surrounding serum 

 (fig. 19), is owing to these amoeboid properties. 



The conditions which are most favourable to this amoeboid activity of 

 the white corpuscles are (1) the natural slightly alkaline medium, such 

 as plasma, serum, or lymph, or faintly alkaline normal saline solution. 

 Any increase of density of the medium produces a diminution of 



