90 ORGANISM AND ENVIRONMENT 



ganic or organic substances. The organs, such as the 

 liver, or fat-containing tissues, in which material is 

 stored, appear to behave similarly; and we have now 

 every reason to believe that we should find the same 

 regulating activity in every organ or part of the body 

 if our methods of investigation were sufficiently deli- 

 cate, and we knew the small differences to be detected. 

 In every direction the progress of physiology and 

 pathology is revealing the astounding delicacy and 

 complication of the regulating processes. 



Up to a certain point we can rest satisfied in the 

 idea that the regulation of the internal medium de- 

 pends upon the specific structures and corresponding 

 reactions of the organs which bring about the regula- 

 tion. But the more we learn about the delicacy and 

 complexity of the regulating processes, the more defi- 

 nitely does a difficulty appear. It is not for nothing 

 that the body regulates its internal environment so 

 exactly. The investigations which reveal the exacti- 

 tude of the regulation reveal equally its fundamental 

 importance to the nutrition and normal working of 

 every part of the body. The organs and tissues which 

 regulate the internal environment are themselves 

 centres of nutritional activity, dependent from moment 

 to moment on their environment. They are constantly 

 taking up and giving off material of many sorts, and 

 their "structure" is nothing but the appearance taken 

 by this flow of material through them. The fact has 

 already been referred to that when the supply of 

 oxygen to the tissues is seriously restricted the result 

 is not merely a slowing down of activity, but actual 



