FEEDING OF WHITE CORPUSCLES. 43 



not quite in the middle but somewhat eccentrically. 

 Occasionally the nucleus is seen to be round; but 

 this is an accidental change, and may be brought 

 about by mechanical injury. Indeed, if the precau- 

 tions above recommended for avoiding pressure are 

 not taken, a large number of the corpuscles become 

 injured, so much so as even to be ruptured and de- 

 stroyed altogether, in which case the rounded nuclei 

 are liberated, and may be mistaken by the beginner 

 for pale blood-corpuscles. 



With regard to the white corpuscles, it will be 

 observed that they are more numerous and larger 

 than in human blood. Moreover, they soon begin, 

 even in the cold, to exhibit very distinct amoeboid 

 movements; and, on account of the greater size of 

 the corpuscles, both these and the other phenomena 

 exhibited by them are much more striking, and 

 tbese corpuscles are therefore much better suited for 

 observation than those of mammals, which in other 

 respects they closely resemble. The distinction be- 

 tween the finely and the coarsely-granular corpuscle 

 is met with again here; but there is also sometimes 

 seen a third kind of corpuscle, fusiform or oat-shaped 

 and devoid of amoeboid properties. It has been sug- 

 gested that these are cells which have belonged to 

 and have become detached from the lining membrane 

 of the bloodvessels. 



Preparation 9. Feeding of the White Corpus- 

 cles. The white corpuscles of the blood exhibit a 

 strong tendency to take into their interior any small 

 particles of insoluble materials which may happen to 

 be in their neighborhood. This tendency they have 

 in common with all amoeboid organisms, and it is 

 nowhere better seen than in the case of the amoeba 

 itself. Because of their greater size, number, and 

 activity, it is better to take the frog's corpuscles for 

 this experiment rather than those of mammalia. 



To obtain the white corpuscles in quantity, and 

 comparatively free from colored ones, take a capil- 

 lary tube (like those used for preserving vaccine 



