138 PHYSICAL CHEMISTRY IN MEDICINE. 



group because of numerous properties that they have 

 in common. This behavior will, no doubt, have to be 

 taken into consideration by any one who attempts to 

 extend the analogy of the behavior of colloids in general 

 to that of the colloidal substances in the fluids and tissues 

 of the organism. For it has been found that the reactions 

 of all colloids do not approximate the reactions that 

 occur in the living body, in consequence of which it has 

 proved necessary, in the attempt to discover such anal- 

 ogies, to cling to the colloidal products of living matter 

 itself, namely, to the proteins. 



The value of an accurate knowledge of the proteins 

 as a means of understanding the inner workings of life 

 phenomena has at different times been differently 

 estimated by physiologists. While a time once existed 

 when many believed that a knowledge of protein structure 

 would by itself give us an explanation of the peculiar 

 metabolism of living matter, we have to-day, when the 

 beginnings of a protein synthesis are apparent and many 

 important constituents of the protein molecule have been 

 isolated, become quieter and soberer in our expectations. 

 Largely independent of a complete insight into the 

 chemical composition of the proteins is the knowledge 

 of their physico-chemical properties, which can only be 

 obtained through utilization of different methods. This 

 knowledge gives us an immediate understanding of the 

 majority of the general properties and functions of the 

 tissue fluids, and is applicable without reserve to those 

 cases also in which no longer living but more or less 

 coagulated cell material serves as an object of research. 

 In the end, however, such a knowledge also renders easy 

 an insight into the changes that take place in living 



