Causation of Vital Movement* 



431 



connected by thread-like bridges. Everywhere the taking on of a 

 figure with smallest surface is the result of stimulation, and the 

 expression of augmented contraction (6) . That which was outstretched 

 becomes shox^ter and in like measure thicker, just as a muscle swells 

 when it shortens itself. 



Since protoplasm, which either does not move at all spontaneously 

 or so slowly that we cannot perceive it, reacts in the same way to 

 stimuli, we must in the case of ordinary movements infer the exist- 

 ence of processes originating them either in the interior, i.e., automatic 

 stimuli, or of external processes which had at first escaped us. 

 Whoever sees for the first time the action of any one of the simpler 

 independent Protozoa cannot avoid the idea that psychic activity 

 in the strictest sense of the term lies behind it, something like will 

 and design. He sees the elementary being seeking and taking up 

 food, avoiding obstacles, and when touched by foreign objects ener- 

 getically drawing back, so that he infers sensation also. Possibly he 

 has struck the correct solution, at least we could not refute him, but 

 we should put his deduction to a hard proof if we showed him the 

 same phenomena in the colourless cells of his own blood, or in the 

 protoplasm of a plant-cell ; and if we placed before him the rhyth- 

 mically contracting cells from the beating heart of a bird's egg 

 incubated barely a couple of days, he would certainly wish with us 

 that the search were for a more material cause, and hope that 

 some chemical or physical cause might be found to set up the 

 process. Biology cannot indeed yet claim to have established such 

 causes in explanation of the automatism of protoplasm, but. no one 

 will blame the science for continuing the search for them. 



Some causes are already excluded, e.g., light, although there are a 

 few micro-organisms whose movements are excited by it (7). Fluctu- 

 ations of temperature may also be left out of account. On the other 

 hand, oxygen has a notable influence (8). Withdrawal of the vital air 

 stops all protoplasmic movement, though without killing the cell-body, 

 as is seen from the fact that after the loss of automatism electrical 

 stimulation can supply its place, and that the normal movements return 

 on readmitting the air. 



We might thus consider oxygen the prime mover in automatism 

 and processes of oxidation its essence, did we not remember that many 

 objects need very prolonged withdrawal of the gas to come com- 

 pletely to rest. This might, however, depend upon the difficulty of 

 removing the last traces of oxygen completely, or it maybe that these 

 cannot be removed by the means adopted, but must remain until 

 consumed by the protoplasm itself. 



Since protoplasm is of pap-like softness, and may be in a state of 

 rest or motion at any spot, its exterior limits are just as capable of 

 change as everything within it is capable of quitting its position and 



