TRANSMISSION OF IMPULSES 9 



are capable of transmission to neighboring protoplasts, or to dis- 

 tant regions of the body. It has been supposed that the disturb- 

 ances thus communicated might consist of variations in electric 

 potential, diosmotic changes, physical vibrations or hydrostatic 

 changes in pressure, although it is probable that the impulse is 

 in itself a characteristic phenomenon of living matter and not di- 

 rectly assignable to any of these comparatively crude classifica- 

 tions of phenomena ; it is furthermore not proven and not neces- 

 sarily true that impulses in all plants are identical in character. 

 The path by which impulses travel has not been identified in 

 any single instance. It is found, however, that transmission is 

 effected more readily in some directions than in others, and that 

 the line of readiest transmission agrees with the location of cer- 

 tain fibrillar structures in cells and with the well-known inter- 

 protoplastic threads of cytoplasm. The fibrillae which serve in this 

 supposed transmission are specialized only in their arrangement 

 and do not offer a parallel to the nervous tracts of the higher 

 animals. 1 



1 Nemec, B. Die Reizleitung und die Reizleitenden Strukturen bei den Pflanzen. 

 Jena. 1901. 



