Chapter XVI 



UNIFORMITIES AND COMPARISONS 

 AMONG COMPONENTS 



§ 131. Variabilities 



The materials contained in the last two chapters lead to highly 

 general considerations. How much of the approach suggested in 

 chapter I has proven useful in dealing with the regulations of 

 diverse components? What general rules are to be derived with 

 respect to rates of exchanges? Which of the rules contribute to 

 the understanding of physiological maintenances? 



The measurement of how much a given physiological property 

 fluctuates under defined conditions allows several kinds of com- 

 parisons. The variability of content of one or many components 

 may be studied in a single individual, in two or more states, in ran- 

 dom individuals of a race or species, or in various periods of time. 

 Each, it seems to me, represents the resultant of organismal and 

 other processes that are maintaining the living unit. 



Upon investigating single individuals, a series of standard 

 deviations of content or of exchange are found. Once a mean con- 

 trol content of the component is measured or its mean rate of 

 exchange is established, deviations may be converted into coeffi- 

 cients of variation. The several quantities studied may then be 

 arranged to form a series of increasing variabilities (table 39). 

 Those maintained most accurately are quantities such as body 

 weight that possess a supposedly large inertia, but equally may be 



TABLE 39 

 Coefficients of variation during 15 to 24 months in dogs under standard conditions 



No. of observations 



Rectal temp. (°C.) 



Body weight 



I?esp. quotient 



Heat prod, rate per unit area 



Pulm. ventil. rate 



Heart frequency 



Breathing freq 



Urjnary N rate 



Source of data 



Indiv. A 



43 

 0.77 

 1.33 

 1.25 

 4.01 

 8.33 



12.8' 

 24.9 



Indiv. O 



46 

 0.52 

 1.32 

 2.22 

 4.64 

 5.79 



8.33 

 18.0 



Wierzuchowski ('37b) 

 361 



11 indiv. 



281 

 0.69 



6.37 

 18.5 



DeBeer and Hjort ( '38) 



