Effect of Age on the Body's Tolerance 145 



water, +7 per cent (Wynn, 1956); potassium, +5 per cent 

 (Drescher et al., 1958); total body sodium (euproteinaemic 

 subjects), +30 per cent (Leaf, personal communication). In 

 the case of phosphorus the end-point chosen was elevation 

 of extracellular inorganic phosphorus concentration to 12 mg. 



160 



140 



HOURS OF 

 OVERLOAD 

 TO PRODUCE 

 TOXIC EFFECTS '20- 



30% INCREASE IN BODY SODIUM 

 GAIN =25 mEq/m2/24« X X 



5% INCREASE IN BODY POTASSIUM 

 GAIN«25 mEq/m2/24'' o— o 



SERUM PHOSPHORUS CONC. ELEVATION 

 TO 4mmol/L (I2.4mg.%) 

 GAIN « ISmMol /m2/24» ? f 



7% INCREASE IN BODY WATER 

 GAIN •l.5L/m2/24» • • 



/ 6 3 6 9 12 18 2 

 BIRTH WKS. --MONTHS— 



3 4 6 e 10 12 16 20 

 YEARS ' 



Fig. 4. Hours of overload (ordinate) needed to produce the 

 percentage increase in body content indicated for each sub- 

 stance in individuals of various ages (abscissa). The rate of 

 gain is that which obtains when rate of input exceeds the 

 physiological maximum tolerance levels for adults shown in 

 Fig. 2 by approximately ten per cent. 



per cent.* Individuals who have surpluses of these degrees 

 are apt to show the signs of intoxication listed in Table I. 



As might be expected, Fig. 4 indicates that infants are 

 relatively much more vulnerable to overloading than older 

 children and adults. This is true not only in the relative 

 terms depicted here, but also in absolute terms because the 

 quantity needed to produce intoxication in a small individual 



* This assumes no bodily capacity for cellular or skeletal storage of surplus 

 inorganic phosphorus, a point on which we have no objective information. 



