2 8 PHYSICAL CHEMISTRY IN MEDICINE. 



who has formulated the question of the state of aggre- 

 gation of living matter in both a penetrating and per- 

 tinent way and has attacked it with the armament of 

 modern physico-chemical research, could bring about a 

 separation of droplets within the contents of a number of 

 cells such as those of the sea-urchin and of the kidney. 

 Such a separation is dependent upon differences in sur- 

 face tension, such as can exist apparently only between 

 fluids. Even before him BERTHOLD had regarded the 

 normal formation of granules and vacuoles in protoplasm 

 as a separation of droplets. JENSEN, has measured the 

 tensile strength of the pseudopodia of orbitolites and 

 has found that it about corresponds with the calculated 

 surface tension. This author has also again pushed into 

 the foreground the surface-tension properties of liquids 

 as a means of explaining many mechanical properties of 

 living matter. 



In spite of these results, which are all of them, appar- 

 ently, capable of only one interpretation, a generalization 

 in the sense that all living substance must be liquid meets 

 with difficulties. The maintenance and the individuality 

 of form in cases in which no supporting framework is 

 demonstrable would have to be attributed by the believer 

 in the liquid state of protoplasm to currents that are 

 able to hold their own against disturbing forces. What 

 is of static origin in the solid state of aggregation needs 

 here a dynamic explanation which brings with it the 

 assumption of a constant expenditure of work. Since 

 an inner stabile differentiation is impossible in a liquid 

 (for even the finest particles of matter dissolved or sus- 

 pended in a liquid endeavor with great force to become 

 uniformly distributed throughout the whole), the assump- 



