LECTURE I 

 INTRODUCTORY REMARKS 



IN these lectures we shall consider living organisms as chemical 

 machines, consisting essentially of colloidal material, which possess the 

 peculiarities of automatically developing, preserving, and reproducing 

 themselves. The fact that the machines which can be created by man 

 do not possess the power of automatic development, self-preservation, 

 and reproduction constitutes for the present a fundamental difference 

 between living machines and artificial machines. We must, however, 

 admit that nothing contradicts the possibility that the artificial produc- 

 tion of living matter may one day be accomplished. It is the purpose 

 of these lectures to state to what extent we are able to control the phe- 

 nomena of development, self-preservation, and reproduction. 



Living organisms may be called chemical machines, inasmuch as 

 the energy for their work and functions is derived from chemical pro- 

 cesses, and inasmuch as the material from which the living machines 

 are built must be formed through chemical processes. It is therefore 

 only natural that the dynamics of living matter should begin with an 

 analysis of the specific character of the chemical processes in organisms. 

 It is neither our intention nor is it possible for us to give an exhaustive 

 analysis, and we shall only go far enough to satisfy ourselves that no 

 variables are found in the chemical dynamics of living matter which 

 cannot be found also in the chemistry of inanimate nature. 



The material of which living organisms consist is essentially col- 

 loidal in its character. Graham introduced the discrimination between 

 colloidal and crystalloidal substances : the latter diffuse easily, the former 

 only with difficulty, or not at all, through animal membranes. The 

 colloidal substances may be in solution or fine suspension, or they may 

 appear in a jellylike or coagulated or precipitated form. In the former 

 case wheje they are liquid we speak of sols, in the latter of gels. The 

 structures which we find in living matter originate mostly through a 

 gelation or coagulation of liquid colloids. We shall see in these lectures 

 that liquefactions and gelations or coagulations may possibly play a 

 great role in various physical manifestations of life ; but as the physics 

 of colloids is still in its beginning, we must not be surprised that it is as 

 yet impossible to carry its application to life phenomena very far. 



