General Discussion 79 



the tissue, but I have no opinion on the direct relation between the 

 cholesterol content and the diffusion cocllicients. 



Bean: Was there an indi\idual correlation as well as an average 

 correlation? 



Kirk: We have only carried out experiments on 50 membranes, and 

 the number of samples for each five-year group is too small in my opinion 

 to make a computation. 



Franklin: What is the total amount of fluid diffusing through the wall 

 of the aorta as compared with that in the capillaries? 



Kirk: I don't know \ The data that I reported refer only to the diffusion 

 of solutes through the membrane. One of the valuable features of the 

 procedure is that the free-moving syringe plungers in the diffusion 

 apparatus ensure a constant total pressure on both sides of the mem- 

 brane, so there should be no mechanical movement of fluid from one side 

 to the other. We usually measure the volumes of fluid in both compart- 

 ments at the end of the experiments. They generally correspond quite 

 closely to what should be expected, which indicates that there has been 

 no net transfer of fluid from one side to the other. 



