Clinicopathological Tests of Ageing 97 



extended our findings. The fact that the incidence of senile 

 elastosis increases with chronological age strongly suggested 

 that the reaction of one of the constituents of the dermis 

 varied with age. Keech (1955) demonstrated a different 

 degree of reactivity of collagen, from the skin of the abdominal 

 wall, to collagenase in different age groups. Burton and co- 

 workers (1955) extended the studies and found that the re- 

 action of skin collagen to other enzymes and alkaline buffer 

 solutions also varied with the age of the subject from which 

 the sample of dermal collagen was obtained. We claim that 

 these findings indicate that definite changes occur in the 

 composition and the reactivity of human dermal collagen 

 with chronological age but as yet we cannot exclude the 

 possibility that these changes are brought about as a result of 

 environmental factors or disease. 



The marked degenerative changes that occur in the aorta 

 and major arteries of the elderly have long attracted scientists 

 to the study of physical properties of these structures. The 

 loss of elasticity is all too apparent, amounting in the case of 

 the Monckeberg type of sclerosis to complete rigidity of the 

 vessel, the calcification in the latter disorder being confined 

 mainly to the media. Lansing, Rosenthal and Alex (1950) 

 estimated the calcium content of the aorta and pulmonary 

 artery in different age groups, always selecting a non-athero- 

 matous area for analysis. They observed a striking increase in 

 the calcium content of the aorta with increasing years but 

 only a slight increase in the pulmonary artery. Further, 

 Lansing and co-workers (1951), using chemical and chromato- 

 graphic analyses found that the amount of elastic tissue in the 

 aorta after the second decade was constant, or might even 

 increase slightly. The amino-acid analyses, however, did 

 reveal differences in the composition of the aorta from the 

 young and from the elderly. There were significant increases 

 in the amount of aspartic and glutamic acids in the elderly. 



The discovery by Balo and Banga (1949&) of the enzyme 

 elastase in pancreatic tissue provided a new approach to the 

 study of arterial changes. The precise nature of elastase is 



AGEING — III — 4 



