THE NEW PHYSIOLOGY. 75 



constant in compoatiHL. Were it oat so tibe 



of the cells would become chaotic, and 



would be completely altered, if not destroyed. Bat tike 



constancy of the blood is maintained by the combined 

 reactions of the organs and tissues themselves. 

 intimate structure of the Bring cells depends on the 

 stancy of the blood, and the constancy of 

 depends on the intimate structure of the lunm \\ If 

 regard this condition as simply a physical 

 state of dynamic balance, it is evident that the 

 must be inconceivably complicated, and at the same 

 time totally unstable. If at any one point in the 

 system the balance is disturbed, it wifl break down, and 

 everything will go from bad to worse. 



A living organism does not behave in this way : for 

 its balance is active, elastic, and therefore very stable. 

 When a disturbance affects its UiaUaic or internal 

 environment, it tends to " adapt " itself to the disturb- 

 ance. That is to say. its reactions become modified in 

 such a manner that the normal is in essential points 

 maintained. An injury heals up : destroyed tome K 

 reproduced, or other parts take on its function : the 

 attacks of microorganisms are not only repelled, bat 

 immunity to future attacks is produced. In reprodactMi 

 the body periodically proceeds to renew almost the whole 

 of its structure. Death may be regarded as a prrintfcal 

 scrapping of structural machinery, and reproduction as 

 its complete renewjJL 



The Anglo- American expedition of which I was a 

 member studied, on the summit of Pikr 

 adaptation to the want of oxygen 

 unadapted persons, all the formidable 



