REGULATION OF ENVIRONMENT 77 



sugar, by feeding with sugar or sugar-forming mate- 

 rial, was slight. If sugar was introduced in very large 

 quantities it was simply excreted in the urine. He 

 then discovered the part played by the liver in regu- 

 lating the concentration of sugar in the blood, and he 

 soon saw that other conditions of life are similarly 

 regulated. This led him to express the opinion that 

 **all the vital mechanisms, varied as they are, have 

 only one object, that of preserving constant the con- 

 ditions of life in the internal environment." 



Bernard's teaching has been to a large extent for- 

 gotten or obscured in masses of unconnected detail, 

 but in reality has been strikingly confirmed by the 

 progress of physiology since his time, and not merely 

 in connection with the physiology of respiration. Let 

 us look at some of the facts. 



I will refer first to the regulation of the amount of 

 water in the blood, since this is a subject which Dr. 

 Priestley and I have quite recently been investigating. 

 It is well known that when large quantities of water 

 are drunk an increasing secretion of urine follows. 

 This increased secretion is evidently the expression 

 of what may be called metaphorically the effort of 

 the body to rid itself of unnecessary water. We made 

 a study of the water excretion by the kidneys on the 

 same lines as we had followed in studying the regula- 

 tion of breathing. 



The increase in secretion of urine a short time after 

 drinking a large quantity of water is very remarkable, 

 the increase being usually to about twenty-fold or 

 more, so that as much urine may be secreted in an hour 



