38 DEVELOPMENT AND HEREDITY. 



viscous body than in a rigid or elastic body. Fur- 

 thermore, it follows from the theory, that the less 

 homogeneous the body acted upon by an external 

 force, the more complicated will be the resulting 

 changes in the body. 



We might, therefore, expect the action of the 

 various kinds of forces upon such a viscous body as 

 living matter to be very pronounced and permanent. 

 Also the results ensuing from the viscous nature of 

 living matter would be still further intensified by two 

 conditions. First, living matter is not homogeneous ; 

 it is formed of a mixture of different compounds rang- 

 ing in their physical states from solid particles to 

 liquids. This fact must add greatly to the complex- 

 ity of the molecular changes. The second condition 

 is also a source of further complexity, and makes 

 living matter peculiar among viscous substances ; for 

 not only does living matter change in the configura- 

 tion of its groups of oscillating molecules, as do other 

 viscous bodies, but it is also undergoing a constant 

 chemical change in its molecules, thus increasing its 

 physical instability by adding thereto a chemical 

 instability. 



Living matter is therefore a substance which is 

 eminently fitted to respond readily to the forces 

 acting upon it, and to retain the impression of those 

 forces. It is in a state of mobile equilibrium, which 



