178 Striated Muscle Contraction [Jan. 



As ftirther evidence of the correctness of the surface-tension 

 theory, Macallum^ recently quoted Jensen'* to the effect that "a 

 thread measiiring one mm. in diameter formed of the Plasmodium 

 of Chondrioderma, a Myxomycete, may, when it is in the dense 

 condition, bear up a weight of nearly a gram. If the force engaged 

 is surface tension it would amount to about 6000 dynes per cm." 

 Because of its enormity this figure of Jensen's at once arrests the 

 attention, for nowhere in the annals of physics and chemistry, can 

 a surface tension of 6000 dynes per cm. be found. Most organic 

 substances that are fluid at ordinary temperatures, have surface 

 tensions well below 50 dynes, ^ when measured against air. Very 

 few aqueous Solutions have surface tensions higher than 85 dynes 

 per cm. For a large number of molten salts the figures vary be- 

 tween 100 and 200 dynes. For most of the metals, when melted, 

 the figure varies between 250 and 1000, altho platinum seems to be 

 exceptionally high, having a surface tension in the molten state of 

 about 2000 dynes per cm.^ 



Presumably, the plasmodium of Chondriodeniia has a chemical 

 composition similar to that of other living matter and consists essen- 

 tially of water plus the usual materials present in living matter. 

 The surface tension of water, when measured against air at ordi- 

 nary room temperatures, is about 70 dynes per cm.''' Altho small 

 amounts of some organic substances can lower the surface tension 

 of water considerably, the surface tension of water cannot be raised 

 very much by any substance, even when present in large amount. 

 There seems to be an upper limit to the surface tension of aqueous 

 Solutions (in exceptional cases this is as high as 109 dynes per cm. 



^Macallum: Jour. Biol. Chem., p. iio. 



* Jensen : Anatomische Hefte, 1905, xxvii, p. 842. 



^ If not otherwise indicated, figures for surface tension are in dynes per 



r dvnes 



centimeter, t. e.,-^ . The magnitude of the dyne can be easily grasped if it be 



cm. 



borne in mind that a mass of i gram is attracted to the earth with a force of i 



gram, or 981 dynes. Consequently, a dyne is practically equal to a milligram 



(force). 



^FreundHch: Kapillarchemie, pp. 30, 62 (Leipzig, 1909). Landolt-Börnstein : 

 Physikalisch-chemische Tabellen, 4te Aufl., pp. 1 14-129 (BerHn, 1912). 



''Landolt-Börnstein: Loc. cit., pp. 112, 128, 129; Freundlich: Loc. cit., p. 62; 

 Lewis: Ztschr. f. physikal. Chem., 1910, Ixxiv, p. 619; Heydweiler: Ann. Physik., 

 1910, xxxiii, pp. 145-185. 



