CHANGES WROUGHT IN PATHOLOGY. 105 



to the behavior of certain typical substances. For from 

 this division there has arisen the conception that all 

 living matter is of necessity connected with the existence 

 of a colloidal ground-substance in which all changes 

 take place. Nevertheless, more than twenty years were 

 necessary before a systematic attempt was made to obtain 

 a conception of the changes that go on in living matter 

 from a study of changes in the state of colloids. In the 

 three years from 1888 to 1891 HOFMEISTER took the first 

 step in this direction, in that, in attempting to explain 

 the physiological effects of salts, he compared the effect of 

 salts upon colloids in a test-tube with the effect of these 

 salts upon the animal organism. During the last decade 

 similar investigations have been carried on with the 

 means offered by physical chemistry, which has during 

 that time enjoyed most rapid growth, and have, in con- 

 junction with the investigations of chemists on inorganic 

 colloids, furnished so abundant a material that the time 

 for a broad alliance between biology and colloidal chem- 

 istry seems to have come. From this most promising 

 section of applied chemistry I would to-day like to take 

 a few facts which to all appearances seem to be of funda- 

 mental biological importance. 



The colloidal substances are present in two forms in 

 the body in a more or less jelly-like condition in the 

 cells, and in a fluid condition in the blood and the tissue 

 juices. The laws of colloid chemistry govern the changes 

 that go on in the cells, only these laws are modified 

 through the metabolism of living matter, the character- 

 istics of which we do not as yet understand. The behavior 

 of the extracellular material is, however, of a much 

 simpler character. In the former case there exists only 



