THE MOVEMENTS OF ORGANISMS 283 



coagulation in the affected cells. All substances and concentrations 

 which salt out or precipitate protein proved to be chemotropic. In 

 connection with positive and negative chemotropism, salts of the 

 alkalis and earth alkalis could be arranged in a lyotropic series similar 

 to that we have repeatedly found in the precipitation of albumin and 

 the swelling of gelatin, fibrin, etc. The salts of the heavy metals 

 act still more strongly and always negatively chemotropic. 



Those movements which are manifest as general effects are still the 

 most accessible to investigation. 



When placed between electrodes, bacteria, spermatozoa, yeast cells 

 and red and white blood corpuscles migrate to the anode; amebae 

 pass to the cathode. Although organized suspensions and colloids 

 migrate either to the anode or a few (e.g., iron oxid hydrosol and 

 aluminium oxid hydrosol) to the cathode, hydrophile organic colloids 

 such as thoroughly dialyzed albumin and gelatin pass in no definite 

 direction when placed in an electric field; they acquire a definite 

 direction only by the addition of electrolytes. OH ions cause an 

 anodal and H ions a cathodal migration. Since the organisms 

 mentioned, considered as a whole, are hydrophile organic colloids, 

 we must assume that their direction of migration in the electric field 

 is determined by the ions clinging to them. Normal albumin with 

 a content up to 0.01 normal NaHC0 3 still migrates to the anode. 

 We need not be surprised, therefore, that the majority of micro- 

 organs and microorganisms also migrate to the anode. The problem 

 reduces itself to determining the direction taken by pure albumin. 



The cathodal migration of amebse is remarkable and requires more 

 thorough study. Equally remarkable is the fact observed by H. 

 BECHHOLD,* as well as by M. NEISSER and U. FKIEDEMANN,* that 

 agglutinated bacteria lose their direction of migration (p. 205), 

 agglutinin having produced a neutralization. 



Following the ideas of G. BERTHOLD,* we are nowadays tempted to 

 explain by a simple formula certain individual movements of the 

 lower organisms and of leucocytes; that is, by changes in surface 

 tension. 1 A fluid or semifluid structure which is constantly under the 

 stress of surface tension assumes a spherical form, as, for instance, oil 

 in a mixture of alcohol and water. If such a drop is placed between 

 two other phases, a change in form occurs, and with it a movement. 

 A drop of oil on the surface of water spreads out; every moistening 

 brings about an enlargement of the surface, a spreading out upon the 

 moistened body (see p. 17). A structure may suffer a change of 

 surface tension in some single spot, locally, so that a movement 



1 A full bibliography is given in L. RHUMBLER'S " Zur Theorie der oberflachen 

 krafte der Amoben": Zeitschr. f. wissensch. Zoologie, 83. 



