THE MOVEMENTS OF ORGANISMS 287 



It may be concluded from this that a substance may be neutral for 

 certain leucocytes and positively chemotactic for others (papayotin), 

 and that the chemotactic relation may vary with concentration 

 (K and Na salts; with reference to lactic acid and quinine solutions 

 see pp. 286-288). 



What relation does all this bear to the theory of changing surface 

 tension? Some data are in its favor. The very first observation of 

 E. STAHL on the plasmodia of sethalium septicum of tanner's bark gives 

 a decided impression that a surface phenomenon is involved. When 

 he brought such a plasmodium clinging to the internal surface of a glass 

 in contact with pure water by introducing the water from below, the 

 plasmodium spread out uniformly; if he introduced tarmic acid, it trav- 

 eled downwards; and on the addition of from 1/4 to 1/2 per cent sugar 

 solution, it traveled upwards. It is just this action of tannic acid 

 which tans the surface of protoplasmic mucus and the phenomenon 

 of spreading out in pure water that point to surface forces. They are 

 also suggested by the observation of RANVIER, according to whom 

 leucocytes spread out more, the larger the surface development of the 

 given body (better on rough than on smooth surfaces and especially 

 well upon elder pith). On the other hand, we recognize from what 

 has been said that the theory which attributes the decrease in 

 surface tension to an electrical charge does not suffice for the ex- 

 planation of all phenomena. An intensely positive chemotactic 

 action is possessed not only by bacteria, but also by extracts and 

 proteins obtained from them. The chemotactic experiments under- 

 taken on the bodies of higher animals (eye, pleura, etc.) do not 

 justify a physico-chemical explanation, because in this instance two 

 factors coexist. The substance itself may act chemotactically; 

 on the other hand, it may be inactive yet cause a necrosis of the 

 adjoining tissue, which then becomes chemotactic and simulates 

 activity 011 the part of the substances under investigation. [Else- 

 where (p. 234) reference has been made to the observations of 

 A. B. MACALLUM. His monograph "Surface Tension and Vital 

 Phenomena," No. 8 Physiological Series, University of Toronto 

 Studies, 1912, includes a bibliography. Tr.] 



Possibly the very original "Quantitative Studies on Phagocytosis" 

 of H. J. HAMBURGER and HEKMA* will permit conclusions concern- 

 ing the causes of the protoplasmic movements of leucocytes, when a 

 method shall have been discovered for measuring the surface tension 

 of protoplasm against water and salt solution. Even now it may be 

 recognized from these studies that the causes of movement are quite 

 complicated since it has been shown that the calcium ion has an 

 entirely specific action in stimulating phagocytosis. If such action 



