958 



GROWTH AND THE AGING PROCESS 



14 



TABLE 1 



VARIATION DURING HUMAN FETAL DEVELOPMENT IN PHASE RELATIONS 

 AND CELL WATER CONTENTS 



(after lob and Swanson, 1934) 



* Calculated on the basis of total fat-free tissue 



+ Calculated on the basis of fat-free, bone-free tissue. 



+ Bone calculated from calcium by formula: Bone (g) = 0.102 {xnM Ca — 5). 



§ Corrected for bone and for extracellular salts = 1% of extracellular fluid. 



from cytoplasm to nucleus, and from one region to another within each of these 

 cell elements. 



On the physical side, then, senescence does not show any orderly and recogniz- 

 able features such as that which characterizes growth. While there are weight 

 changes in various organs, a decrease in weight is not found in all organs nor in 

 those where it usually occurs is it seen in all senescent individuals. 



The chemical aspects of growth and senescence include the changes in the rela- 

 tive quantities of the various elements and compounds in the organism as a whole 

 and the shifts in their distribution. During the process of growth, from a very 

 early embryonic stage and until maturity is reached, there is a progressive decrease 

 in the amount of water present relative to the weight of the organism. The majority 

 of authors who have written concerning this decrease have given the impression 

 that it represents an actual partial "desiccation" of the protoplasm. A number of 

 recent writers, however (Needham, 1931 ; Shohl, 1939; Stearns, 1939) have indi- 

 cated that by far the greater part of the decrease in amoimt of water is due to a 

 decrease of extracellular fluid rather than a "dehydration" of the cells themselves. 

 Thus Needham (1931) mentioned the possibility that the decrease in water con- 



