The Energy of Segmentation 289 



THE EPITOMIZING FORMULATION OF THE FOUR LAWS, AND THE 

 CONDITION FOR THEIR PRACTICAL APPLICATION 



Already it has been emphasized, at least implicitly, that it is 

 with systems, arbitrarily limited to a certain extent, that we are 

 most intimately concerned in working out the meaning of, in apply- 

 ing, and in deducing the implications of the Four Laws. Now 

 systems are by nature somewhat limited or closed; they are 

 spatially marked off from their environment by a certain perma- 

 nence of their configuration and proximity of their parts. It is 

 with such systems that we have to do in experimenting with living 

 organisms; in these the parts may be regarded as cells, or as organic 

 structures within these, or as colloidal particles, etc., while from 

 these parts there result creatively the qualities of whatever is for 

 the problem at hand regarded as a whole. 



Now, concerning any system which undergoes a change as a 

 whole, three statements can be made, which are in agreement 

 with the Four Laws, namely: 



L That by it a certain quantity of heat will either be taken 

 up or given off. 



IL That either it will do work or work will be done on it. 



IIL That the quantity of energy of the system will either in- 

 crease or diminish. 



In general, the change in the internal energy of the system is 

 equal to the difference between the work done by the system and 

 the quantity of energy added to it. This may be formulated as 

 follows : 



Let U = the internal energy of the system; 



Q, = the heat energy taken up; 



A = any other energy added; 



W -= the work done by the system; then 

 Q,-\-A = E, the total energy added. 



Then, according to the First Laiv, and giving an analytic expres- 

 sion to it, after any change in the internal energy from U^ to t/g, 

 as identical with which the system does work, the value of the 

 change equals 



U,-U,=E-W [i] 



