392 PROTOPLAS]\IIC ACTION AND NERVOUS ACTION 



which excitation is transmitted from one region of a 

 protoplasmic element to another; this assumption, 

 however, is a direct corollary of the local action theory 

 of transmission. Further comparative observations in 

 this field are desirable; the theoretical side also needs 

 careful consideration, since both extracellular and 

 intracellular conductivities are concerned and the 

 precise relations between these two are insufficiently 

 known/ 



Various other facts of comparative physiology also 

 indicate the importance of the bioelectric variations in 

 the different forms of protoplasmic transmission. The 

 transmission of excitation between cells which are in 

 contact or close proximity but not otherwise connected 

 is a phenomenon difficult to explain except on the electri- 

 cal theory; the ''rheoscopic frog" experiments have 

 already been cited as examples of transmission demon- 

 strably resulting from secondary electric stimulation by 

 bioelectric currents. Several years ago, I called atten- 

 tion to a number of instances of apparently the same 

 effect;^ for example, one active swimming plate in a 

 ctenophore can influence another through several 

 millimeters of sea water; spermatozoa collected in a 

 clump are soon found beating synchronously;^ ciHated 

 epithelial cells transmit waves of movement; the trans- 



^ Brooks has recently studied the relation between the conductance 

 of living cells and tissues ( Laminar ia, yeast, bacteria, Chlorclla) and the 

 conductivity of the medium, and finds a close proportionality between 

 the two (Jour. Gen. Physiol., V [1923], 365. 



^Op. cil. (1914), pp. 4275. 



3 The detached cilia of Paramoecium show a similar behavior, 

 according to recent obsrvations of Al verdes {Arch. ges. Physiol., CXCV 

 [1922], 245). 



