16 



INTEODTJCTION PEOTOPLASM CELL 



(a) Ameboid motility is exemplified in the movements of an ameba; 

 hence the name. This consists essentially in the formation of a proto- 

 plasmic process or pseudo podium, into which the main mass of proto- 

 plasm flows, thus pro- 

 ducing progression (Fig. 

 20). The movement of 

 the white blood-corpus- 

 cles is of this sort (Fig. 

 21). 



(b) Ciliary motility 



FIG. 21. A LEUKOCYTE FROM HUMAN BLOOD IN 

 ACTIVE AMEBOID MOTION. 





The figures .indicate the successive forms assumed ig characteristic of hair- 

 by the cell. Drawings were made at intervals of one 



minute. X 500. llke processes ot certain 



cells; such processes or 



cilia represent essentially permanently differentiated delicate pseudo- 

 podia. The method of cilium formation is illustrated in its simplest 

 form in the transient vibratory processes that arise under certain condi- 

 tions on leukocytes (Fig. 225). In metazoa generally ciliated cells are 

 attached, motion being limited to the cilia, which are located on the free 

 border. The function of cilia is to pro- 

 pel secretions toward the surface. The 

 motion is wavelike and always in one 

 direction. The cilia are generally at- 

 tached to a double row of granules, the 

 'basal bodies' (Fig. 22), perhaps parti- 

 tion products of the centrosome. In 

 Protozoa, e.g., Paramecium (Fig. 3), 

 the entire surface of the cell may be 

 ciliated; the function of the cilia here 

 being progression, and the direction of 

 stroke is reversible. Certain cilia are 

 non-motile, e.g., in the epididymis, 



FIG. 22. THREE CELLS FROM THE 

 EPIDIDYMIS OF THE RABBIT. 

 The non-ciliated cell has a diplo- 



some at its free border. The ad- 



where they are closely clumped into Jacent ciUated cells have in place a 

 , double row of basal granules to 



brushhke masses (Fig. 25). The func- which the cilia are attached. (Aftp- 



tion of such cilia is, in part at least, to v. Lenhossek.) 



furnish a means for the elimination of 



secretions. Flagellate motion is to be regarded as a variety of ciliary 



motion. A flagellum is commonly regarded as a more robust cilium. 



The purpose of flagella is to propel the cells to which they are attached. 



Usually in higher animals the number of flagella is limited to one to a 



cell. The best examples of flagella are furnished by spermatozoa (Fig. 23). 



