4 PRACTICAL HISTOLOGY. 



the coloured corpuscles, colourless, irregular, granular bodies. They are few in number 

 compared with the red, and by careful searching three distinct varieties may be made out 

 as follows : 



(a) Finely granular Corpuscles. These have no definite shape, are colourless, and have a 

 faint, finely granular appearance. They are usually slightly smaller than the coloured 

 corpuscles, and irregular in outline, with fine projecting processes. Careful observation may 

 discover nuclei, which are irregular in shape, and sometimes subdivided. 



(/S) Coarsely granular Corpuscles. These also are indefinite in shape and colourless, but 

 contain a large number of highly refracted granules, usually lying at one side of the corpuscle, 

 whilst the subdivided nucleus occupies the other side. They may be either larger or smaller 

 than (a) and their processes are usually blunt and rounded. 



(7). The third variety consists of small nucleated masses of protoplasm about the size of the 

 nucleus of a coloured corpuscle ; and as these latter sometimes escape from the corpuscles, care 

 must be taken not to confound the one with the other. 



Amoeboid movements of Colourless Corpuscles. The finely granular corpuscles (a) may be 

 seen to change their shape and place (in the newt even at the ordinary temperature of the air) 

 in the same manner as an amoeba does, hence the term amoeboid ; and the coarsely granular 

 corpuscles (13) behave in a similar manner. In these latter, the granules, being more distinct, 

 may be seen as it were to rush from one part of the corpuscle to another. In this change the 

 granules are passive, they are carried by the protoplasm. The small nucleated masses (7) 

 undergo similar changes of site and form, but, on account of their smallness, these phenomena 

 are not so easily observable. The best way to notice these changes is to make drawings from 

 time to time say every two minutes of a colourless corpuscle. The change of form is some- 

 times so great that a corpuscle may actually be seen to divide into two. At other times a 

 transparent spot --a vacuole which contains fluid may be seen in some corpuscles. All these 

 changes take place more rapidly when the slide is warmed on a hot stage (p. xxviii) ; and 

 when this is done, it is necessary, in order to prevent evaporation, to surround the cover 

 with a little oil or, better, with a ring of melted paraffin. (Sketch tlie changes of shape in 

 ' PI. I., Fig. 8). 



Feeding Colourless Blood-corpuscles. That the colourless corpuscles can take small par- 

 ticles into their interior is easily demonstrated, thus : all that is required is to rub up a little 

 china ink or vermilion in a three quarter per cent, salt solution, and to mix a drop of this 

 with the blood and examine the preparation from time to time on a hot stage, as indicated 

 above. The preparation requires to be sealed up with oil to prevent evaporation. For newt's 

 blood 30 C. is sufficient. 



The EFFECTS OF KEAGENTS on the colourless corpuscles should next be observed. 



(a) Water. When the blood is irrigated with water, the protoplasm of the white corpuscles 

 swells up, becomes quite clear and transparent, and the nuclei, usually two or three in number, 

 come clearly into view. Sometimes also when so treated the granules may be seen to exhibit 

 Brownian movement. 



() Acetic Acid. When blood is irrigated with a one per cent, dilution of acetic acid, the 

 protoplasm becomes clear and transparent, and a bi- or tri-partite nucleus is distinctly seen. 

 (Indicate this effect in one of the corpuscles sketched in PI. I., Fig. 8.) 



(c] Magenta. When the blood is irrigated with magenta solution (p. xliv), the protoplasm 

 takes on a faint red, the nuclei a deep red colour. (Indicate the effects in one of the corpuscles 

 sketched in PI. I., Fig. 8.) 



