416 PROF. TH. W. ENGELMANN. 



protoplasm creeps in this manner over the motionless cortical 

 layer just as a snail's foot over the surface upon which it is 

 crawling. 



4. Stoppage of Spontaneous Movements by 

 Artificial Stimulation. 



As described above, the first result of artificial stimulation is, 

 as a rule, a standstill or slowing of the already existing spon- 

 taneous movements in the spots directly excited. Superficially 

 considered it might appear as if in all these cases no excitation 

 but rather a paralysis had taken place ; a view which has been 

 specially urged by vegetable physiologists. The opposite must, 

 however, according to our theory, take place, and it can easily 

 be shown that according to it the result observed and no other 

 would take place. Inasmuch as all not previously contracted 

 inotagmata fall into contraction as a result of the excitation, 

 the impulses to movement at all points of the protoplasmic 

 mass become essentially equal, the entire mass thus immedi- 

 ately assuming a position of equilibrium. It is just the same 

 as if all the muscles of an animal were simultaneously stimu- 

 lated to the maximum ; the external appearance in this case 

 being a standstill, a stoppage of the normal movements. 



Hitherto, in referring the movements of protoplasmic masses 

 to active changes of form of the smallest component particles, 

 we have merely postponed the solution of the real difiiculty, 

 which consists rather in an explanation of the mechanism 

 of these changes of form. Here we must limit ourselves for 

 the present to a few notes, which must be regarded as hints 

 for further investigations rather than as any solution of the 

 problem. 1 



For reasons already assigned the mechanism concerned can be 

 no other than that mechanism which lies at the basis of active 

 changes of form of muscles and ciliary organs. "With regard 



' Cp. in this respect, ■' Arch, f. d. ges. Physiol.,' vii, p. 33, et seq., 155, et 

 seq. (especially p. 176), 1873 ; viii, p. 95, et seq., 1874; xviii, p. 1, et seq., 



1878. 



