ARTIFICIAL AMEB/E 263 



neat coil within its body, where it can be digested. The process is done so sys- 

 tematically and with svich evident adoption of the moans at hand to the desired 

 end, that it seems as if it must be an adaptation of tlie amolia to circumstances, 

 the result of long experience or of heredity. That an artilicial ameba can per- 

 form the same manouvers seems hardly credible, but it is readily done with almost 

 no dilTerence in detail. If the chloroform drop is given a long fine thread of shel- 

 lac, it proceeds to bend the thread in the middle, and to send pseudopodia out 

 along the thread to pull it into the drop, coiling it up inside as the chloroform 

 softens the substance of the thread, until it is all contained within the drop, pro- 

 vided, of course, that it is not too long (a thread six times as long as the chloroform 

 drop may be taken in completely)- The bending and coiling of the thread in 

 this experiment is entirely in accord with the known laws and i)henomena of surface 

 tension. 



Fully as striking an ameboid action as the coiling up of a thread too long to be 

 taken in, is the building, by some of the protozoa clo.sely related to the ameba 

 {Difflugia) of a shell which the animal seems to form by cementing together grains 

 of sand, or diatom shells, or other suitable particles. The particles are united 

 so closely and fitted together so well that they are almost i)erfectly free from crev- 

 ices. Even this process is accurately imitated in Rhumbler's experiments. If a 

 drop of oil is mixed with fine grains of quartz sand, and dropped into 70 per cent, 

 alcohol, the grains are thrown out to the surface, where thej- adhere to the surface 

 of the drop and to one another exactly as do the particles in a difflugia shell. So 

 well fitted are the particles that the artificial shell may remain intact for months, 

 and resemble the natural shell indistingui&hahly. 



Furthermore, the phenomenon of cell division can be imitated to some extent 

 by oil droplets. Biitschli considered that the cleavage furrow of dividing cells 

 represented an area of greater surface tension, and McClendon imitated cell 

 division as follows: He suspended a drop of rancid oil and chloroform between 

 water and salt solution, and allowed sodium hydrate to flow from pipettes against 

 two opposite points in the droplet, whereon the surface tension was lowered and 

 the drop bulged at these points, the band of higher surface tension constricting 

 the drop between these two points. Burrows states that the changes seen in 

 cells dividing beneath the microscope correspond well to these experimental 

 observations.'^ 



Relation of the Above Experiments to the Phenomena Exhibited by 

 Leucocytes in Inflammation 



The experiments cited indicate strongly, to saj^ the least, that 

 amebse, and presumably leucocytes, react to stimuli of various kinds, 

 chiefly through the effect of these stimuli upon surface tension. The 

 stimuli may come from within the cell, being in this case the result of 

 changes in composition brought about by metabolic processes; such 

 chemical products alter the tension of the surface nearest their point 

 of origin, causing what appears to be spontaneous motion. Stimuli 

 acting from without may be chemical, thermal, electrical, or mechani- 

 cal, but in any event they act as stimuli to motion through their eft'ect 

 upon surface tension; if they decrease the surface tension the cell goes 

 toward them; if they increase the tension, the cell moves away.''* The 

 behavior of leucocytes in inflammation may be explained on these 

 purely physical grounds very satisfactorily, as follows: 



At the point of cell injury or of infection, substances are produced 

 that exert positive chemotaxis, as can be shown by experiments both 



'8 See Trans. Congress Amer. Phys., 1913 (9), 77. 



"' OH-ions decrease, H-ions increase the surface tension of leucocytes (Sch- 

 wyzer, Biochem. Zeit., 1914 (60), 306, 447, 454), which may explain the fact 

 that lactic and other acids exhibit negative chemotaxis. 



