12 PHYSICAL CHEMISTRY IN MEDICINE. 



through a utilization of the methods of physical chem- 

 istry. 



The studies of HOFMEISTER on the protein -precipitating 

 power of salts have shown that these arrange themselves 

 in the same order as they do when arranged according 

 to their diuretic or cathartic action. 



In a study of the condition of swelling which I pub- 

 lished some time ago a large number of biological rela- 

 tions were found. Analogies exist, for example, between 

 the absorption of water by substances capable of swelling 

 and the absorption of water by the living organism; 

 and the velocity of swelling and the time of a muscle 

 contraction are about the same. A continuation of 

 these experiments along the line of changes in the physical 

 state of the proteins has led to results whose significance 

 also extends beyond that for the dead material itself. 



As is well known the proteins suffer when subjected to 

 heat a change in state, a so-called coagulation, which, gen- 

 erally speaking, is not reversible. The coagulation point, 

 that is the temperature at which this change takes place, 

 is, among other things, dependent to a large extent upon 

 the presence of neutral salts. If we employ the neutral 

 salts in the form of equimolecular solutions, we can 

 compare their effects on the coagulation-point, which 

 may vary between more than fifteen degrees centigrade. 

 If now we plot the concentrations upon the abscissas, the 

 corresponding coagulation temperatures upon the ordi- 

 nates, we obtain curves which give a general survey of 

 the laws governing the process. From these we learn 

 that with solutions of a medium concentration, the 

 order in which the different salts follow each other when 

 arranged according to their different acicjs is independent 



