i8o Striatcd Muscle Contraction [Jan. 



Jensen's arithnieticall}^ correct figure of 3000 dyiies per cm. is 

 still so very much higher than that of any known substance that one 

 is led to suppose that perhaps Jensen's method of calculating the 

 surface tension is incorrect. According to his formula, the weight 

 sustained by a plasmodium thread when divided by the circumfer- 

 ence of the thread gives the surface tension. This method may be 

 correct, but it is not mentioned among the various methods described 

 in the literature. This makes it desirable that someone prove its 

 correctness. 



To the writer it seems that the quotient obtained by Jensen does 

 not represent a surface tension. 



According to Pfeffer/^ the question of surface tension does not 

 enter the problem (of Chondrioderma) at all, for the reason that 

 the outer layers of the plasmodium thread of Chondrioderma are 

 solid at the time when a weight can be sustained. Or, to be more 

 precise, Pfeffer states that Chondrioderma have the property of 

 reversibly varying the consistence of the outer layer, from that of 

 the fluid protoplasm in the interior of the cell to that of solid 

 gelatinous masses. The tougher outer layer is regarded by Pfeffer 

 as a physiological product, and not until this has been brought back 

 to its originally fluid condition can changes in surface tension be 

 regarded as factors in the problem. 



If Jensen's formula gives results that have a real physical mean- 

 ing, it ought to be possible to apply it to other forms of living mat- 

 ter and to obtain results that can be interpreted. Parnas^^ found 

 that the smooth muscles of certain clams could sustain very great 

 weights. He so loaded living, intact clams, that in one case (p. 458) 

 a smooth muscle having a cross section of 0.3 sq. cm. sustained a 

 weight of 3000 grams for three hours. Similar observations on 

 the great weight-sustaining power of smooth muscle have been made 

 by others.^^ 



Assuming that the cross section was of uniform tensile resist- 

 ance, each sq. mm. sustained a weight of 100 grams, which is 75 



iiPfeflfer: Pflanzenphysiologie, 2te Aufl. (1904), pp. 716-718. 



12 Parnas : Arch. f. d. gesammte PhysioL, 1910, cxxxiv, pp. 441-495. 



i^Bethe: Arch. f. d. gesammte PhysioL, 1911, cxlii, pp. 291-336. Cohnheim 

 and von Uexkull : Ztschr. f. physiol. Chem., 1912, Ixxvi, pp. 314-321; Cohnheim: 

 ibid., pp. 298-313. 



