THE VITAL PHENOMENA OF CELLS 



37 



within the protoplasm. Examples of this are found in the Amoebae and other 

 Khizopoda (Figs. 19 to 23), and in the leucocytes of all classes of animals, 

 which very closely resemble Amoebae with respect to their structure. 



This ability of the leucocytes is of great importance to the body as a whole, 

 for wherever a destruction of tissues takes place either from normal or patho- 





FIG. 22. A white blood corpuscle of the frog, containing an anthrax bacillus. The two figures 

 were drawn from the same cell at different times, after Metschnikoff. 



logical causes, the debris is taken up by the leucocytes and is removed. The 

 leucocytes play an important role also in disposing of the pathogenic Bacteria 

 which find their way into the body, since they are able to eat and to digest 

 such organisms (Fig. 22), and thereby to afford the body substantial pro- 

 tection against infection (Metschnikoff). 



The more highly organized elementary organisms provided with cilia and 

 a cell mouth, such as the ciliate Infusoria (Figs. 2 and 28), ingest solid 



FIG. 23. Vampyrella spirogyrce, a rhizopodous unicellular organism, ingesting the contents of 



an alga cell, after Cienkowski. 



particles by creating with their cilia a vortex so directed that the particles 

 arc driven into the mouth. In this and other similar ways of taking up solid 

 particles the organism can exercise an actual choice of nourishment; certain 

 Rhizopoda for example eat only certain alga cells (cf. Fig. 23). 



