74 J. E. Kirk and T. J. S. Laursen 



Tlie average diffusion coefficient values observed for the 

 age groups ten to thirty-nine, forty to fifty-nine, and sixty 

 to eighty years are shown in Table II. It will be seen from 

 the table that a definite tendency was found for the diffusion 

 coefficients to increase with tlie age of the individuals. The 

 significance of this tendency is also evident from the calculated 

 coefficients of correlation between age and the diffusion 

 coefficients (Table III). 



Table III 



In connection with the data reported in Table III it should 

 be noted that the total lipid and cholesterol contents of the 

 aortic membranes were likewise found to increase witli 

 advancing age. The coefficient of correlation age/total lipid 

 was -|-0-48 for the intima samples and -f-0'32 for the media 

 samples. The corresponding r values for the correlation, 

 age/cholesterol were +0-40 and +0-31. 



Tentorium cerebelli 



Diffusion studies with this connective tissue membrane of 

 comparatively simple structure were carried out on 35 samples 

 derived from individuals ranging in age between one and 



