44 PHYSICAL CHEMISTRY IN MEDICINE. 



at another it protects the protoplasm against the poisons 

 of its own products. Questions in absorption, secretion, 

 pharmacology, and immunity are Connected with, these 

 changes in state, a discovery of the nature of which 

 must constitute one of the great aims of biochemical 

 research. 



3. The Colloidal State and the Reactions that Go On in 

 Living Matter.* 



I. 



COLLOIDAL material enters into the construction of 

 living matter in two forms first, in the liquid or solid 

 state, in GRAHAM'S sense of the word, and, second, in 

 the form of a more or less solid, swollen mass, at 

 times sufficiently solid to have independent form, at 

 others, because of its approximation to the semi-solid 

 condition, still subject to the laws of surface tension 

 governing liquids. We wish to consider in this paper 

 some of the properties of this swollen (jelly-like) condition 

 which can be attained not only through the absorption 

 of the so-called "solvent" by the original solid material 

 for example, the absorption of water by dry gelatine but 

 also through "gelation" of the liquid colloid. This 

 gelatinous state is of the greatest interest to the biologist 

 in that it represents a state of aggregation in which the 

 properties of a solid and those of a liquid are often united, 

 a condition which is so frequently necessary in living 

 matter. For this reason the experiments that have been 



* From Naturwissenschaftliche Rundschau, 1902, XVII, p. 312. 

 Address delivered before the Morphologisch-physiologische Gesellschaft 

 in Vienna, May 13, 1902. 



