32 Vitality and Orgariizatioti of Protoplasm. - 



plasm is rendered possible, we shall have gained a scientific insight into 

 that which principally constitutes it a living substance. 



Selecting suitable protoplasmic individuals as objects of investiga- 

 tion, the sundry processes operative in the self-movement of their sub- 

 stance are readily detected. And here protozoa, belonging to the Sarco- 

 / dina, afford the easiest and clearest view~of the intimate workings' that 

 ; underly vital motility. By carefully watching the emission and retrac- 

 tion of their so-called pseudopodia; or rather by watching the outflow, 

 stagnation, remelting and shrinking of the substance of their pseudopo- 

 aia, the desired information can with certainty be gathered. 



In order to arrive quite unmistakably at the correct interpretation 

 of what are the actuating causes when protoplasmic pseudopodia are 

 seen forcibly to flow out into space, eventually to come to a standstill, 

 and finally to shrink, collapse and be reincorporated into the body of the 

 protoplasmic individual ; in order to gain an understanding of these 

 Q^ fundamental vital occurrences it is best to select such amoeba, or such 

 rhizopods as emit slowly long and broad pseudopodia, whose flow of 

 granules and distinction of granular and hyaline substance clearly in- 

 dicate what is really taking place. The most favorable specimens for 

 the purpose I have met with were gigantic amoeba, whose long, ])lunt 

 finger-shaped pseudopodia measured 0.8 mm. in diaineter. And almost 

 ') , as favorable were gigantic difflua pyrifornis, whose pseudopodia were 



often equally as broad, and at times about three times as long as the 

 shell, though in this latter case they were niuch more slender in propor- 

 tion to their length. 



First, then, what causes the stagnation, shrinking and collapse, or the 

 so-called contraction of the living substance composing the pseudopodia ? 

 Definite, unmistakable signs prove it to be due to chemical disintegra- 

 tion. The stagnation of the outflowing pseudopodia is seen to begin at 

 the surface of contact with the medium, extending more and more 

 deeply towards the axis of the protoplasmic cone or cylinder. This 

 occurrence is clearly evidenced, first, by the slackening flow of the 

 granules embedded in the substance near the surface, and. then, by that 

 portion of thejjyaline substance brought into contact with the medium 

 JDecoming itself flocculent and eventually granular. Complete proof 

 that the change here observed is, in fact, the work of chemical disinte- 

 gration, is visibly given in vesicles, or so-called vacuoles, forming 

 within the disintegrating substance, in which are gathered the effete 

 fluid products of disintegration, presently seen to be eliminated. 



Now, as to the influences that are causing this chemical disintegra- 

 tion, they are readily detected. Any sort of contact or external stimu- 

 lation tends to decompose more or less profoundly the highly complex 

 rnd explosive constitution of the protoplasm. In this "sensitiveness" 

 to stimulation consists its so-called "irritability," formerly considered 

 the very essence of vitality, or, at least, its most characteristic mani- 

 festation. On artificial stimulation an expanded pseudopodium, or arp 

 entire expanded amoeba will instantly shrink or contract. And if the 



