General Discussion 65 



air would be increased. This is exactly what happens with 

 increasing age (Fig. 7). 



In young normals the average CO uptake is 57 per cent 

 while in the older age group it is down to 48 per cent and in 

 emphysema it falls to 31 per cent. With advancing years the 

 contact between alveolar air and pulmonary blood, or 

 diffusing capacity as it is sometimes called, becomes impaired. 



In conclusion, as age increases the chest wall becomes less 

 mobile and the elastic recoil of the lung is reduced. In conse- 

 quence the volume of the lung increases and the efficiency 

 with which gases are mixed in the alveoli is reduced. The 

 capacity of the lung to ventilate the pulmonary blood is also 

 slightly impaired. All of these changes occur in a greatly 

 exaggerated form in pulmonary emphysema. 



REFERENCES 



(A full bibliography will be found in these references). 



Bates. D. V. (1952). Clin. Sci., 11, 21. 

 Bates, D. V., and Christie, R. V. (1950). Clin. Sci., 9, 17. 

 McIlroy, M. B., and Christie, R. V. (1954). Clin. Sci., 13, 147. 

 McIlroy, M. B., Marshall, R., and Christie, R. V. (1954). Clin. Sci., 

 13, 127. 



DISCUSSION 



Franklin: 1 wonder if Prof. Christie will tell us what he thinks is the 

 real connection of ageing with emphysema. 



Christie: I think it has some relationship to what Medawar said yester- 

 day. You remember he said that senescence is due to a combination of 

 inborn deterioration or change in vulnerability, and deterioration due to 

 repeated injury or stress and strain. I think this concept certainly 

 applies very well to the lung. The lung, as you know, is a highly elastic 

 organ, and there are two pathological conditions which can subject the 

 lung to increased stress and strain. One is chronic cough or chronic 

 bronchitis, and the other is asthma. Provided the asthma stops before 

 the age of thirty-five you will not develop emphysema, and similarly 

 with chronic bronchitis. But if they persist, or if they develop after the 

 age of thirty-five, you are likely to get emphysema. In other words, 

 from the point of view of that stress and strain, the lung seems to become 

 more vulnerable around the ages of thirty-five to forty-five. The 

 connection with ordinary senescence is this: that even without chronic 

 bronchitis or asthma the lung is perhaps unique among structures in 

 that it is constantly subject to stress and strain with each breath. It is 



