360 PROTOPLASMIC ACTION AND NERVOUS ACTION 



conditions of mechanical stimulation; related observa- 

 tions are those of Carlson, who observed that increasing 

 the mechanical tension of the heart-ganglion of Limulus 

 increased the rate of nervous discharge;^ and in frog's 

 muscle it has been found that stretching causes an 

 increase in the production of CO2 and lactic acid.^ 

 Increase of permeability is probably a factor in both of 

 these effects. 



The effects of mechanical, electrical, thermal, and 

 other changes of physical condition on indifferent or 

 unspecialized cells of various kind (blood corpuscles, 

 egg-cells, epithelial cells, etc.) all have a bearing on the 

 question of the relation of permeability-change to 

 stimulation. The constant current causes polar dis- 

 integration in many cells, an effect analogous to polar 

 stimulation ; similarly it causes polar secretion in cutane- 

 ous and mucous gland cells.^ The laking of blood 

 corpuscles by induction shocks has also evident analogies 

 to electrical stimulation. 



There is abundant evidence of an increase in the 

 permeability of the surface layer of many Qgg cells during 

 the early stages of normal fertilization. In some cases 

 the surface protoplasm undergoes extensive alteration 

 and there results a visible loss or secretion of material to 

 the exterior {Nereis, lamprey, frog).^ In the sea-urchin 



^ Carlson, American Journal of Physiology, XVIII (1907), 149. 



* Eddy and Downs, American Journal of Physiology, LVI (192 1), 188. 



3Loeb, Arch. ges. Physiol., LXV (1896), 308. 



4 Cf., for Nereis, F. R. Lillie, Journal of Experimental Zoology, 

 XII (191 2), 414; for the lamprey, Bataillon, Arch, de zool. exper. et 

 gen., VI (1910), Series 5, 128; for frog, Backmann and Runnstrom, 

 Arch. ges. Physiol., CXLIV (191 2), 287. 



