General Discussion 105 



very early in the work, and I can say that the calcium exists largely as an 

 apatite-like crystal. At least the ratios are proper for an apatite. I 

 indicated, in referring to the dicarboxylic acids, that we may have only 

 a primary linkage, meaning that perhaps the initial calcium may have 

 gone to one of the carboxyl groups and then formed a nidus for the 

 gro\\i;h of a crystal-like chain. Now it is not adventitious calcium 

 phosphate derived from non-elastic tissue, because one can expose this 

 calcified old elastin to dilute acids, and remove all of the calcium and 

 then, in rendering the solution slightly alkaline, add calcium ions under 

 controlled conditions and effect recombination. Not all of it goes back, 

 we are not reconstituting the long chain calcium apatite but we do 

 recombine a significant amount of calcium to the elastin. We can't do 

 that with young elastin. So apparently there are groups in old elastin 

 which have an affinity for calcium. 



Aub: But you get such a large percentage of calcium — a tremendous 

 change. Is that all attached to your elastin? Could some of it be 

 phosphate or apatite? 



Lansing: I think it is calcium phosphate. And, as I say, some of it at 

 least is directly linked to the elastin molecule. How far the change goes 

 in crystallization I can't say. Anatomically in micro-incineration all the 

 mineral is directly in or on the elastic fibres. Visual observation, of 

 course, doesn't establish chemical continuity, but anatomically all the 

 calcium salts are in or on the elastic fibres when viewed in dark field 

 micro-incinerations . 



Medawar: I'm interested in the idea raised by Lansing that the elastic 

 fibre systems of the skin and of the blood vessels may have very different 

 properties. Dr. Bean mentioned that in Osier's disease there was im- 

 perfect development of elastic fibres in vessels; I presume they are all 

 right in the skin. Is it not also the case that there are congenital affec- 

 tions in which elastic fibres are very poorly developed in the skin but 

 are normal in the arteries? If so, that would tend to reinforce the idea 

 that we are really dealing with two somewhat independent fibre systems 

 which might well be expected to undergo different types of senescent 

 change. 



Tunbridge: If I may butt in here, I must cross swords with Lansing 

 rather strongly on certain statements he has made. First of all, the 

 amount of elastic tissue in normal skin is very small. The criteria for 

 that are three-fold. One is qualitative and histological, which is always 

 unreliable. The second is qualitative but makes use of more advanced 

 techniques, particularly electron microscopy in which, as Lansing said, 

 the pattern of collagen is very distinct, and the pattern of elastin, 

 although amorphous, by that very fact is distinctive. In qualitative 

 studies from all sites of the body we have found very little elastin— a 

 finding substantiated by Wyckoff using the glass knife, w hich cuts a very 

 thin section and minimizes the criticism that with the mechanical tear- 

 ing techniques the elastic fibres might be lost. This was a serious 

 technical criticism, in view of the widely held opinion that there were a 

 lot of elastic fibres in ordinary skin. One of Prof. Astbury's workers has 

 taken large masses of skin from different sites and dealt with it on a 



