DELICACY OF ORGANIC REGULATION 51 



centration of the blood, that the very smallest 

 variation in the direction of acidity or alka 

 linity excites them to excrete a liquid which 

 is, relatively speaking, intensely acid or alka 

 line, the net result being that the normal 

 hydrogen ion concentration of the blood 

 remains practically constant. 



When we have such figures before us 

 we realise the marvellous fineness of the 

 regulation by the kidneys and respiratory 

 centre. Physiologists are still so much under 

 the influence of the old gross mechanical 

 theories of secretion that attempts at exact 

 measurements of the delicacy of regulation 

 by the kidneys have hitherto scarcely been 

 made in the case of regulation in other 

 directions, though we have every reason to 

 believe that similar delicacy exists as regards 

 the regulation of the water, salts, and other 

 blood constituents. It is hard to realise that 

 something which looks under the microscope 

 like nothing more than a somewhat indefinite 

 collection of gelatinous material can react, and 

 continue throughout life to react, true as the 

 finest mechanism of highly tempered steel, 

 to the minutest change in its environment. 



