104 General Discussion 



always interested me. Foetal haemoglobin is quite a different proposition 

 from adult human haemoglobin, and we know there are a number of 

 proteins in the foetus which change biochemically but do not apparently 

 change functionally with development. In the study of ageing might 1 

 call your attention to the possibihties of the placenta, which ages very 

 rapidly and calcifies very rapidly also. You might get some interesting 

 leads and connections betM^een foetal life and adult life by a study of the 

 ageing placenta. 



Tunhridge: I am sorry Dr. Hall is not able to be here, because he has 

 found a number of very interesting facts dealing with less drastic methods 

 of getting elastin. I think Dr. Lansing will agree that even one-tenth 

 normal sodium hydroxide is very drastic chemically. It will remove 

 much of the non-protein material present, since it destroys mucopoly- 

 saccharides. It will also, however, cause hydrolysis of peptide linkages 

 in the main protein chains themselves and therefore it is surely not the 

 best reagent for the preparation of a pure undegraded sample of 

 "elastin". Using methods which, though still chemically drastic, are less 

 likely to produce the effects of alkalis, we do find marked differences. 

 F'irst of all the polysaccharide is retained in quit^ liigh concentration. 

 We do not agree with Balo and Banga that the amount of carbohydrate 

 is of the order of 10 per cent, because if you look at their methods, they 

 have not allowed for the amino acid content of their hydrolysates, 

 which would probably be included in any determinations of reducing 

 sugars. In fact, after correspondence with them, they now agree that it 

 is more of the order of 5 per cent. I suggest most tentatively that 

 although the amino acid composition of so-called elastin and of collagen 

 differ from one another, the main reason for their differing physical pro- 

 perties lies elsewhere, probably in the fact that their polysaccharide 

 content differs, both qualitatively and quantitatively. The difference in 

 physical properties would suggest that elastin has a rubber-like con- 

 stitution with enormous stretch right up to the point of breaking, as 

 opposed to collagen which only stretches slightly before breaking. It is 

 difficult to get pure specimens, and one hesitates to draw conclusions, 

 but I do think Hall's work shows that there is a definite difference 

 between the two proteins. It is not clearcut; the chemical differences 

 when a more gentle method of separation is used are not as great as 

 those usually suggested. It is fascinating, and it is in line with what 

 McCance has said. 



Auh: I liked Dr. Lansing's presentation, but there is one question that 

 puzzles me, and that is the extraordinary increase in calcium in this 

 elastin. If I'm correct in my chemistry, calcium phosphate would still 

 be intact in 1/10 n sodium hydroxide. You only spoke of calcium and 

 not phosphate, but in your last slide I saw that phosphate also went up 

 in your preparation. I wonder whether the calcium is really attached to 

 the elastin or whether it is a residue of calcium phosphate or of an apatite 

 which remains in your solution after it is digested. Then it would be 

 just calcification remaining behind and not attached to the elastin. Its 

 significance would be very different. 



Lansing: That is a question which, of course, came to our attention 



