94 LIBBIE H. HYMAN 



ones, 22 and that the direct mechanical cause of the contraction 

 of the muscle is the coagulation in the anisotropic segments with 

 displacement of fluid into the isotropic ones. The relaxation is 

 the reverse process. Lillie thinks the cause of the coagulation is 

 the depolarization of the cell membranes due to the nerve im- 

 pulse. In the amoeba, of course, there is no nerve impulse, no 

 constant external factor to initiate the chemical changes which 

 precede locomotion, and certainly one cannot postulate a de- 

 polarization of the surface. It is indeed a far cry from the 

 locomotion of an amoeba to the contraction of a striated muscle 

 but we may perhaps believe that a similar principle is involved 

 in both, although doubtless working in a very different way and 

 through a different structural mechanism. We may imagine that 

 nature starting with a colloidal solution such as protoplasm has 

 been able to make it move by the very simple method of altera- 

 tion of the colloidal state, and then gradually evolved a structure 

 which could use the same principle in an infinitely more effective 

 way. 23 



Lillie (loc. cit.) has referred to one case in which contraction 

 is accompanied by visible coagulation, namely, the.ctenophore 

 swimming plate. The contractile activity of this structure, if 

 artificially accelerated, is accompanied by a progressive coagula- 

 tion of its substance. Various similar facts of coagulation ac- 

 companying contraction are known for vertebrate muscle, but 

 their interpretation is not as clear as in this case. Another 

 clear-cut case is that of the foraminiferan Astrorhiza (Schultz, 

 '15). The surface of this animal consists of a sticky 'skin' 

 which can be drawn out into long threads. The inner protoplasm 

 is quite different, and cannot form threads. The organism nor- 

 mally puts out very long slender pseudopodia in bundles. The 

 ends of these move about in the water and finally attach them- 

 selves. After this attachment, the pseudopodia develop a very 



22 This statement finds complete confirmation in the dissections of Kite ('13), 

 who states that living striated muscle is the most "viscuous, elastic, and cohe- 

 sive of living gels," and that the dark segments are more concentrated gels than 

 the light segments. 



23 I consider that it would be futile to attempt to discover the details of the 

 mechanism of striated muscle by studying amoeboid movement. 



