GROWTH AND THE AGING PROCESS 



959 



TABLE 2 



EFFECT OF GROWTH ON MUSCLE, LIVER, AND BRAIN OF CATS 



(Yannet and Darrow, 1938) 



A = cats weighing 300-800 g (approximately 1-2 months of age) 

 B = cats weighing 800-2500 g (2-6 months of age and older) 



Muscle 

 A B 



Group 



Liver 

 A B 



Number of animals 

 II 9 



Brain 

 A B 



Observed data 



Water — g/kg total tissue 785 



Fat — g/kg total tissue 20 



Chloride — mequiv./kg total tissue 28.2 



Sodium — mequiv./kg total tissue 36.8 

 Potassium — mequiv./kg total tis- 

 sue 80.0 

 Phosphorus — mA//kg total tis- 

 sue 59.0 

 Nitrogen — g/kg total tissue 24.7 



Derived data 



Extracellular fluid — g/kg total 



tissue 220 



Cell water — g/kg cells 746 



Potassium — mequiv./kg cell water 1 39 



Phosphorus — mA//kg cell water 104 



Nitrogen — g/kg cell water 43.6 



770 

 25 



23-3 

 90.4 



66.4 

 29.1 



730 



25 



31.0 



38.6 



80.1 



75-6 

 23-7 



707 

 60 



27.7 

 33-3 



73-7 



90.3 

 27.4 



846 808 

 30 60 



43-2 39-0 

 55-1 52.5 



87.0 



76.9 

 14.7 



5.0 



96.3 

 16.8 



* The presence of an undetermined amount of extracellular nitrogen and phosphorus in 

 brain makes these figures uncertain. 



tent may be actually an index of the decreasing amount of "primitive connective 

 tissue" which contains great quantities of intercellular fluid. 



The decrease in sodium and in chloride during human development is taken 

 by Shohl (1939) and Stearns (1939) as a consequence of the decrease of inter- 

 cellular fluid. Murray, (1926) had shown that in the chick, between the sixth and 

 the eighteenth days while the dry body weight (fat-free, feather-free, bone-free) 

 increases to 217 per cent of its starting point, there is a drop of about 25 per cent 

 in chloride content. Such a decrease in extracellular fluid probably is a phenomenon 

 common to vertebrate embryos. 



Similar evidence of a decrease in extracellular fluid is seen in studies by lob and 

 Swanson (1934) on a series of fetuses ranging from 3.2 to 10 lunar months (Table 

 i). In this series there is a progressive fall in chloride, at least from 3.7. months to 

 ID months, and a fairly steady rise in potassium. The changes in these constituents 

 have been interpreted to signify a progressive rise in the proportion of cells, from a 

 value of 320 g/kg of body weight at 4.3 months to 512 g/kg at term. The concen- 

 tration of solids in the cells after 4.3 months fails to show any consistent trend 

 with age. 



Literature p. gji 



