THE CIRCULATORY SYSTEM 



259 



greatly in different cells. In some cases, especially in the 

 smaller leucocytes, it is nearly spherical.. In other cells it is 

 very irregular in outline and may be deeply constricted in 

 several places, and not infrequently it may be divided into 

 two or more distinct nuclei. In the smallest leucocytes the 

 amount of cyto- 

 plasm is relatively 

 small and forms a 

 narrow, irregular 

 envelope around 

 the spherical nu- 

 cleus. The cyto- 

 plasm of the larger 

 corpuscles is 

 relatively much 

 greater in amount. 

 By virtue of 

 their amoeboid 

 movements the 

 white corpuscles 

 have the power 

 of independent 

 locomotion and 

 they even pass 

 through the deli- 

 cate walls of the 

 capillaries into the 

 spaces between 

 the other cells of the body. They are not confined, there- 

 fore, to the blood vessels like the red cells, but may be 

 found in almost every part of the organism. And they often 

 pass out of what are, strictly speaking, the limits of the body 

 into the mouth and alimentary canal. 



Fig. 71. — Blood corpuscles of the frog, a, b, c, 

 red blood corpuscles ; a and b, young stages ; 

 c, mature corpuscle ; d-h, spindle cells in differ- 

 ent stages ; d, early stage ; e, a somewhat later 

 stage ; /,£■, h, typical spindle cells ; i-l, forms of 

 leucocytes ; /', very early stage ; J, an older stage ; 

 k, cell with lobed nucleus ; /, cell with four nuclei. 

 (After Dekhuyzen.) 



