20 BLOOD CORPUSCLES. 



corpuscle (often, but not always, towards the centre) one or 

 more bodies may be distinguished of roundish, ovoid, or irre- 

 gular form, and tolerably distinct contour, somewhat less re- 

 fractive than the surrounding protoplasm, and containing one 

 or more granules. These bodies are commonly close together, 

 and are called nuclei. The nuclei are usually invisible so long 

 as the colorless blood corpuscle is spheroidal ; when it spreads 

 out into a layer, they can be distinguished. But they can also 

 be observed when the lamina draws itself together into an irre- 

 gular clump ; and it may be then seen that they are subject to 

 continual change, both as regards form and relative position. 



We now leave the corpuscle we have been hitherto studying 

 and observe another, which is roundish, and exhibits a very 

 few delicate processes. At present we see no nuclei. After a 

 time we notice that one of the processes suddenly becomes 

 longer and thicker, so that the corpuscle is now club-shaped, 

 consisting of a tapering stalk ending in a knob. The stalk 

 incloses an oblong, compressed nucleus, and the knob two 

 such nuclei close together, the surfaces of both being shaggy, 

 with minute processes. We have not long to wait until the 

 body loses this form. A new process, towards which the two 

 nuclei tend, shoots out from the knob, at right angles to the 

 stalk. The knob becomes smaller in proportion to the growth 

 of the process, while the two nuclei gradually approach its ex- 

 tremity. The next change is, that each process lengthens out 

 in the direction of its axis into a filament, the two together 

 being of such a length as to stretch over the whole field. 

 These filaments spring from a small clump of granular proto- 

 plasm the original knob above mentioned. Each filament 

 swells out at its end into a little mass, which, in the one case, 

 contains a single nucleus, in the others, two nuclei. Continu- 

 ing our observation, we notice that the clump at the junction 

 of the two filaments disappears, while the other masses, which 

 are now united by a straight thread of nearly equal thickness 

 throughout, get larger, and send out new processes. The 

 larger mass now creeps nearer the edge of the field; the 

 smaller is drawn after it, but moves more slowly, so that the 

 hyaline thread which connects them gets thinnerand longer. 

 But while we are watching it, the large mass undergoes 

 changes which are a repetition of what we before observed in 

 the original clump. A process shoots out from it at right 

 angles to the direction of the thread : into this process one of 

 the nuclei finds its way; it then stretches out into a filament, 

 which is swollen at its extremity into a protoplasmic envelope 

 for the nucleus. Still later, we* find that the filaments become 

 thicker and shorter ; that the clumps between which they 

 stretch, again approach one another, until, in their confluence, 

 the original form reappears. A similar series of changes may 



