96 R. E. TUNBRIDGE 



Organs and tissues vary both in their complexity and their 

 accessibility. They tend, however, to be less complex than the 

 whole organism and in some cases portions may be detached for 

 detailed study and therefore become much more suitable for 

 controlled studies. All would agree with the observations of 

 Prof. Danielli, that even the simplest tissue is very complex 

 when compared with the cell. 



The ease of access of the skin has made it a favoured organ 

 for study. Samples may be readily taken for detailed examina- 

 tion and environmental conditions, in so far as the external 

 surface is concerned, can be controlled. Many changes have 

 been observed in the skin associated with chronological age 

 and even poets and authors have felt the changes sufficiently 

 significant to write about them. All are familiar with the 

 increase of capillary naevi in the elderly, the changes in cer- 

 tain of the skin appendages such as the hair, and the changes 

 in the texture of the skin, the thinning of the skin, the tend- 

 ency to scarring, haemorrhage and pigmentation particularly 

 in certain sites, such as the face and the extensor surface of 

 the forearm. It is usually suggested that the latter changes 

 are brought about by exposure but there is no convincing 

 proof for the theory. The incidence of the changes increases 

 with chronological age after 60, no matter what the previous 

 occupation or mode of life of the individual, and they are 

 equally prevalent both in the female and in the male. Histo- 

 logical examination of the affected areas reveals the presence 

 of an increase of elastic staining material. Unna (1896) des- 

 cribed changes in the staining properties of both collagen and 

 elastin and clearly recognized that metachromatic staining 

 was obtained with a variety of tissues. It is surprising, 

 therefore, that later workers persisted in referring to the 

 dermal changes in senile elastosis as indicating an excess of 

 elastic tissue. Tattersall and Seville (1950) working in my 

 Department, in co-operation with Astbury and Reed (Tun- 

 bridge et ah, 1952), were able to show that the elastic stain- 

 ing material was altered collagen. Other workers, notably 

 Gillman and co-workers (1954), have since confirmed and 



