PHYSIOLOGY 103 

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Fig. 41. Outline sketches of photomicrographs of Amoeba proteus dur- 

 ing locomotion, as viewed from side (Bellinger). 



In the face of advancement of our knowledge on the nature of 

 protoplasm, Rhumbler realized the difficulties of the surface ten- 

 sion theory and later suggested that the conversion of the ecto- 

 plasm to endoplasm and vice versa were the cause of the cyto- 

 plasmic movements, which was much extended by Hyman (1917). 

 Hyman considered that: 1) a gradient in susceptibility to potas- 

 sium cyanide exists in each pseudopodium, being the greatest at 

 the distal end, and the most recent pseudopodium, the most sus- 

 ceptible; 2) the susceptibility gradient (or metabolic gradient 

 arises in the amoebae before the pseudopodium appears and hence 

 the metabolic change which produces increased susceptibility, is 

 the primary cause of pseudopodium formation; and 3) since the 

 surface is in a state of gelation, amoeboid movement must be due 

 to alterations of the colloidal state. Solation, which is brought 

 about by the metabolic change, is regarded as the cause of the ex- 

 tension of a pseudopodium, and gelation of the withdrawal of 

 pseudopodia and of active contraction. Schaeffer (1920) mentions 

 the importance of the surface layer which is a true surface tension 

 film, the ectoplasm, and the streaming of endoplasm in the amoe- 

 boid movement. 



Pantin (1923) studied a marine hmax-type amoeba (Fig. 40, h) 

 and came to recognize acid secretion and absorption of water 

 at the place where the pseudopodium was formed. This results 

 in swelling of the cytoplasm and the pseudopodium is formed. 

 Because of the acidity, the surface tension increases and to 

 lower or reduce this, concentration of substances in the "wall" 

 of the pseudopodium follows. This leads to the formation of a 

 gelatinous ectoplasmic tube which, as the pseudopodium, ex- 

 tends moves toward the posterior region where the acid condition 

 is lost, gives up water and contracts, finally becoming trans- 

 formed into endoplasm near the posterior end. The contraction of 



