432 EVENING DISCOURSES 
Clearly, it was desirable to get as much information as possible about the 
rate of respiration of the apple, and so experiments were made in which 
apples were enclosed in small chambers through which air was passed in a 
steady stream in order that the rate of breathing of the apples could be 
measured. ‘The purity of the air was known, and the quantity of carbon 
dioxide given off by the apples was measured in the ordinary way. The 
results are given in the diagram. ‘The curve starts in May when the apple 
sets; from May to September inclusive, the normal apple lives on the 
tree, and as it grows it becomes less acid ‘and changes its colour, while its 
seeds come nearer to maturity. 
It will be observed that in the early stages respiration is rapid, but the 
rate falls until, as maturity is approached, it is but one-tenth of the starting 
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RESPIRATORY ACTIVITY 
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value. Then, corresponding to the point B on the curve, there comes a 
sudden critical change in the life of the apple—a change which is called 
the climacteric. ‘The rate of respiration is rapidly doubled, flavour and 
aroma are developed, and the apple attains maturity at C. Thereafter the 
rate of respiration slowly subsides until the fruit dies, death itself being 
marked by a short-lived rise preceding the final collapse. Instead of there 
being seven ages as in man, in the life of the apple there appear to be four 
ages. 
Under natural conditions the history of the apple would end at B, and 
at this point a wild apple would fall, the function of the apple as an organ 
of the tree being merely to provide the seeds with cover whilst they are 
ripening. From B onwards the store-keeper, the salesman and the con- 
sumer are keenly interested in the apple. In the curve the period B—D is 
about three months ; the problem is to prolong it to six months or more. 
You will not be surprised to hear that the research worker found the 
apple, like most living matter, to react in an extremely complex way to any 
