CHAPTER V. 

 GENERAL PHYSIOLOGY. 



There is no doubt that our knowledge of the structures of 

 Protozoa far outstrips our knowledge of their functions. The 

 minute size of the individuals and the inadequacy of micro-chemical 

 tests make it extremely difficult to follow out any physiological 

 process to its end. Furthermore, it must not be overlooked that 

 physiological problems here for the most part begin where similar 

 problems of the Metazoa leave off, namely in the ultimate processes 

 of the single cell. Here the functional activities have to do with the 

 action and interaction of different substances which enter into the 

 make-up of protoplasm and, for the most part, these are beyond 

 our powers of analysis. A few of these activities may be dupli- 

 cated individually and apart from correlated functions, in the 

 laboratory. Or specific reactions between specific chemical sub- 

 stances may be obtained as, for example, the digestion of fibrin by 

 fluids extracted from the protozoon protoplasm; or in a physical 

 sense the reversal of the sol and gel states in colloidal mixtures. 

 Such individualized processes, however, give little idea of the 

 infinite play of forces continually operating in living protoplasm, 

 all of which, harmoniously working together, make up the phe- 

 nomena of vitality and distinguish living from lifeless matter. 



As Mathews points out, the essential differences in chemical 

 actions in protoplasm and in physical nature are: (1) The order- 

 liness with which they are carried on, and (2) the speed of the 

 reactions. 



A starving Dileptus gigas will slowly decrease in size although its 

 form remains about the same (Fig. 6, p. 27). This is due to disinte- 

 gration through continued oxidation and other catalytic processes 

 which lead to the exhaustion of protoplasmic constituents unless new 

 food is added. If the process is continued the organism will ulti- 

 mately die in from one to three weeks. If a Dileptus is accidentally 

 crushed its protoplasm will completely disintegrate within a few sec- 

 onds. The process of disintegration in the first case is orderly, in the 

 latter completely disorganized. Other normal vital activities are 

 equally orderly; the orderliness dependent possibly on the regulation 

 of permeability by the colloidal membranes, the alveolar membranes, 

 nuclear membrane and investing membrane of the cell; and regula- 

 tion of permeability in turn is dependent upon the chemical make up 



