378 



PHYSIOLOGICAL EEGULATIONS 



certain electrolytes and the replacement of excised tissues are the 

 slowest processes. Net exchanges of heat and of water are about 

 equally provided for. About the same order among components 

 is represented in the quotients available for two species. 



Physiologists know that it takes longer to recover one's nitro- 

 gen balance than to recover one's breath ; that an excess of bromide 

 may last for weeks and an excess of lead for years ; while an excess 

 of CO2 lasts for a few seconds and a deficit of excitability for a 

 millisecond. In poorly defined terms it could be said that the fast- 

 est adjustments are the most urgent; and for some of the corre- 

 sponding components there is evidence that loads of them interfere 



TABLE 41 



Rates of recoveries in dog and in man. Data from tables 42 and 40. 

 Velocity quotient - rate /load = 1/hour 



readily with many other processes. Stated more accurately, the 

 velocity quotient is a suitable measure of the promptness with 

 which recoveries occur. 



The data also indicate a relation between velocity quotient and 

 tolerated load. Attainable loads of carbon dioxide and of oxygen 

 are very small compared to water in terms of molecules, grams, or 

 other usual dimensions. For those two components a small incre- 

 ment in molecules is a large increment in per cent of the content 

 at balance, however. Again, the ratios of turnover to content 

 (table 40) are very large for those components having high veloc- 

 ity quotients (oxygen = 12) ; this ratio may prove to stand in close 

 proportion to the quotient. It may mean that high sensitivity to 

 increment accompanies large change in relative concentration, such 

 a change being secured by having the content small. Many ex- 

 haustive studies are required to furnish the data from which such 

 correlations can be adequately and broadly drawn. 



When quotients are considered in relation to loads, several 



