Clinicopathological Tests of Ageing 99 



properties of collagen from different sites, has also been able to 

 show that the collagen from ligamentum nuchae has greater 

 extensile properties than collagen from other sites. 



These observations indicate the difficulties in interpretation 

 of experimental findings. Firstly, the results obtained with 

 detached tissue do not necessarily represent what would occur 

 in the body in life. Secondly, it is impossible to know how 

 far the changes are the result of disease processes and how far 

 they can be taken as evidence of a biological process of ageing. 



The obvious limitations of human sources of material, 

 whether the whole organism or an organ, must not blind us to 

 the constant stimulus afforded by the study of such material. 

 The changing age composition of the population in what is so 

 frequently referred to as Western society is focussing every- 

 one's attention upon the present limitations of the aged. 

 We are all human and therefore the problem is personal, 

 perhaps too personal and not approached in the detached 

 way that it should be. The clinician may incorrectly attribute 

 changes to a process of ageing but his observations that 

 apparently similar stresses may produce different effects in 

 different age groups, that the skin of the face changes with 

 chronological age, but to a greater extent than the skin of the 

 back, that generalized atheroma is considered almost a normal 

 finding in the aortic arch, for a person over the age of 60, yet 

 is rarely found in the pulmonary artery of the same individual, 

 open up lines of thought which stimulate the investigator 

 and lead us to hope that one day we shall be able to decide 

 whether the so-called "effects of age" are merely the conse- 

 quence of accumulated trauma to the organ or to the in- 

 dividual or that there is really an alteration of structure and 

 of function associated with chronological age. 



It is my hunch that we are more likely to obtain a key, 

 possibly the key, to the problem "What is ageing?", or "Is 

 there a biological process of ageing?", from colony studies 

 such as those of Dr. Muhlbock or from the researches of Dr. 

 Parkes than from human studies. Of course, what applies to 

 the mouse or to the hamster need not apply to the human. 



