THE FROG: HISTOLOGY, GERM CELLS, DEATH 101 



% Mm 



the organism living in the blood. Each of them retains 

 all the powers of the whole organism. They are 



ationo , f e cei"8 i " irrital:)le ' as ma 7 be seen b y tneir increased 

 activity on warming, or by the effect upon them 

 of various drugs. They appear to be automatic, for we 

 can often trace their movements to no stimulus. Their 

 substance must undergo katabolism, for they expend 

 energy, as we have seen, in contraction and in the 

 manufacture and secretion of various substances. The 

 fact that the stimulation of one part of their surface 

 by the presence of a bacterium causes other parts to 

 co-operate in swallowing 

 it shows the existence 

 in them of conduction. 

 They assimilate from 

 the plasma nourishing 

 matters to repair their 

 waste. They reproduce 

 by fission, first the 

 nucleus and then the 

 cytoplasm parting into 

 two, and each half of 

 the cytoplasm taking a 

 half of the nucleus. 

 Consisting as it thus 

 does of protoplasm 

 which retains all the 

 primary powers of a 

 living being, the white 

 corpuscle shows us that 

 these powers must be 

 regarded as the birth- 

 right of all protoplasm, 

 and that their posses- 

 sion by all organisms is due to this fact, and not to 

 the presence of several kinds of protoplasm. Yet it is 

 important to notice that the independence of the leucocytes 

 is only relative. They are still wholly dependent for their 

 nourishment upon the body by which they were formed, 

 and their activity is directed to the welfare of that body. 

 With the relative independence of the white corpuscles, 



i 





Fig. 60. — Cartilage stained and mag- 

 nified, showing cells, some of which 

 are in pairs formed by the division 

 of a single cell, matrix, and the 

 newly secreted part of the matrix, 

 which forms capsules around the 

 cells. 



