56 PRACTICAL HISTOLOGY. 



numerous as the first. A third set consists of nucleated 

 protoplasts, finely granular, and much smaller than the 

 others. The nuclei can seldom be distinctly seen in the 

 white corpuscles without the addition of re-agents. 



c. The amoeboid movements of the white corpuscles. 

 Select one of the large finely-granular corpuscles of irregu- 

 lar shape, and watch it carefully for some minutes. Usually, 

 even at the ordinary temperature, it changes its shape with 

 considerable rapidity, and it is instructive to draw the out- 

 line of the corpuscle at the end of every two minutes or so, 

 in order to be fully convinced of the changes that occur. 

 The direction of the motion is indefinite ; a protrusion may 

 take place at any part of the protoplasm, and be afterwards 

 withdrawn, or the protoplasmic process may adhere to the 

 slide or cover-glass, and the mass of the corpuscle be drawn 

 after it, thus leading to a locomotion of the corpuscle. 

 Sometimes neighbouring processes coalesce, and the readi- 

 ness with which they do so is opposed to the idea that the 

 protoplasm is enclosed in a membrane, as some are inclined 

 to suppose. 



d. Effect of acetic acid. Place a small drop of dilute 

 acetic acid at the margin of the cover-glass, and gently 

 raise the cover with the point of a needle, to break the 

 coagulum, and so allow the acid to penetrate. The 

 coloured corpuscle suddenly becomes enlarged, but still 

 retains its oval form. This probably results from softening 

 of the envelope of the corpuscle, together with endosmose ; 

 the former permitting and the latter producing the enlarge- 

 ment. At the same time, the corpuscle loses colour, and 

 the nucleus becomes evident. After a time it becomes 

 very difficult to see the envelope of the corpuscle ;, the 

 nucleus, however, remains perfectly distinct. It is usually 

 somewhat corrugated. It sometimes happens that the 

 nucleus becomes of a yellow colour, owing to the acid solu- 

 tion of the blood pigment tinging it, after the manner of 

 such a dye as magenta. Until the acid is added, the nu- 

 cleus is not permeated by the blood pigment. This lies 

 entirely outside the nucleus, between it and the envelope 

 of the corpuscle. The general mass of each white corpuscle 



