74 THE NEW PHYSIOLOGY. 



normal life-history, yet in ultimate analysis all this must 

 be due simply to the reactions between its physico- 

 chemical structure and environment. I will not at this 

 point quarrel on general grounds with the " must," but 

 simply endeavour to test it by the facts of physiology. 



We can distinguish in a living organism what seems 

 a more or less definite structure of bony matter and con- 

 nective tissue. Yet we know that all this is built up, 

 and in adult life is constantly being pulled down, rebuilt 

 and repaired, through the activities of living cells. It 

 is thus within the living cells that we must look for the 

 structure which is supposed to react so as to maintain 

 the normal. These cells are made up of what has been 

 called "" protoplasm." Now the more we study proto- 

 plasm the more evident does it become that this ' ' sub- 

 stance " is extraordinarily sensitive to the minutest 

 changes in environment. Take away or diminish or 

 increase the minute traces of calcium or potassium salts 

 in the blood-plasma, or the traces of various substances 

 supplied to the body by other organs ; or add traces of 

 certain other substances : the reactions of the proto- 

 plasm are quickly altered, and its structure may be 

 destroyed. It is evidently in active relation with its 

 environment at every point, and one cannot suspend 

 this activity without altering it. Even deprivation of 

 oxygen for perhaps a minute may kill a nerve-cell. 

 There is no permanent physical structure in the cell : 

 the apparent structure is nothing but a molecular flux, 

 dependent from moment to moment on the environment. 



Now, when we look at the blood, the internal or im- 

 mediate environment on one side of the cells in the body, 

 we find, as already shown, that this is almost incredibly 



