THE CELL. 31 



fluence is negative, (negative chemotaxis), and the cell is forced 

 away from the center of the disturbed chemic equihbrium. 



Ciliary movement is the wave like motion of small hair like 

 protoplasmic projections of cells known as cilia. Ciliary motion 

 occurring in migrating or wandering cells produces movement 

 of the entire cell and in stationary cells, produces move- 

 ment of fluids or semitluids that contact the cilia. In higher 

 animals motion of entire cells as a result of ciliary movement 

 is observed only in spermatozoa. The normal function of ciliary 

 movement is to aid m i^ropelling mucus in the respiratory tract, 

 ova in the Falh^pian tul)es, spermatozoa in the ^'as deferens, etc. 

 Ciliary movement is due to intracellular protoplasmic disturb- 

 ances, at least it is the result of chemic influences. Cver stimu- 

 lation or disease may produce increased action and finally fatigue 

 or paralysis of the cilia, or they may produce cessation of their 

 action. The most e.xtensive and important cell movement is 

 noted in the highly specialized muscular cell. As the muscle 

 cell maintains its relative position when contraction takes place, 

 the movement is principally evident in the structures to which 

 the muscle fibre is attached. The rate and extent of contraction 

 vary in the different varieties of muscle. The spongioplasm is 

 the active portion of the cell in contraction, the hyaloplasm being 

 passive only in function. Xerve fibres terminate in end-organs, 

 i. e., muscle plates, through which are transmitted impulses that 

 produce muscular contraction. Muscular movement is an in- 

 dispensable function, as circulation and respiration are abso- 

 lutely dependent upon it. Digestion and urination would also 

 be suspended if muscular action were curtailed. Immobility ma)r 

 be the result of muscular fatigue or dissociation of motor nerves 

 and muscle fibres, or be due to neuroses. Muscular spasms 

 are usually the result of violent stimulation of the motor nerves, 

 although it mav result from excessive stimulation of the muscle 

 fibres themselves. 



Metabolism.— Metabolism is a term used to designate the 

 processes included in nutrition or digestion, absorption, assimila- 

 tion, katabolism, and excretion. These processes are the results 

 of cell action. Metabolism includes two general processes, i. e., 

 constructive metabolism or anabolism and destructive metabol- 

 ism or katabolism. Active cells are constantly consuming foods 

 and eliminating waste material. The qirantity, quality and 

 previous preparation of the nutritive substances required, varies 

 according to the specialization and degree of action of cells. The 

 leucocyte is relatively simple, i. e., it is a primitive type of cell. 

 A leucocyte is not very selective in its food requirements. It 



