44 BLOOD. 



When seen in a normal condition, and " at rest," the white corpuscle is a 

 small, spherical, colorless mass, varying in size, but with an average diameter 

 of about 10 v, and presenting generally a finely but sometimes a coarsely 

 granular appearance. [Fig. 9.] The surface, even when the corpuscle is 



[FIG. 9. 



a, white corpuscles of human blood; d, red corpuscles (high power).] 



perfectly at rest, is not absolutely smooth and even, but somewhat irregular, 

 thereby contributing to the granular appearance ; and at times these irreg- 

 ularities are exaggerated into protuberances or "pseudopodia" of varying 

 size or form, the corpuscle in this way assuming various forms without 

 changing its bulk, and by the assumption of a series of forms shifting its 

 place. Of these " amoeboid movements," as they are called, we shall have 

 to speak later on. 



In carrying on these amoeboid movements the corpuscle may transform 

 itself from a spherical mass into a thin, flat, irregular plate ; and when this 

 occurs there may be seen at times in the midst of the extended finely gran- 

 ular mass or cell body, a smaller body of different aspect and refractive power, 

 the nucleus. The normal presence of a nucleus in the white corpuscles may 

 also be shown by treating the corpuscle with dilute acetic acid,, which swells 

 up and renders more transparent the cell body but makes the nucleus more 

 refractive and more sharply defined, and so more conspicuous, or by the use 

 of staining reagents, the majority of which stain the nucleus more readily 

 and more deeply than the cell body. In what perhaps may be considered 

 a typical white corpuscle, the nucleus is a spherical mass about 2-3 // in 

 diameter, but it varies in size in different corpuscles, and not unfrequently 

 is irregular in form, at least after the action of reagents. It occasionally 

 appears as if about to divide into fragments, and sometimes a corpuscle may 

 contain two or even more (then generally small) nuclei. Though staining 

 readily with staining reagents, the nucleus of an ordinary white corpuscle 

 does not show the nuclear network which is so characteristic, as we shall see, 

 of the nuclei of many cells, and which in these is the part of the nucleus 

 which especially stains; in the closely allied lymph corpuscles, to which we 

 shall have immediately to refer, a nuclear network is present. 



The cell body of the white corpuscle may be taken as a good example of 

 what we have called undiffereritiated protoplasm. Optically, it consists of a 

 uniformly transparent but somewhat refractive material or basis, in which 

 are imbedded minute particles, generally spherical in form, and in which 

 sometimes occur minute vacuoles filled with fluid; it is rarely, if ever, that 

 any distinct network, like that which is sometimes observed in other cells, 

 can be seen in the cell body of a white corpuscle whether stained or not. The 

 imbedded particles are generally very small, and for the most part distributed 

 uniformly over the cell body, giving it a finely granular aspect ; sometimes, 

 however, the particles are relatively large, making the corpuscles coarsely 

 granular, the coarse granules being frequently confined to one or another 



