primarily impaired by Age. 1 83 
be analogous to the lungs of animals, is it very improbable 
that the natural debility of old age of trees and of animals, 
may originate from a similar source? — This is a question, 
upon which I am not by any means prepared to give an 
opinion : but I believe it will very generally be admitted, that 
the human subject is best formed for long life, when the 
chest is best formed to permit the lungs to move with most 
freedom. I have also long and attentively observed amongst 
our domesticated animals, that those individuals longest re- 
tain their health and strength, and best bear excessive labour 
and insufficient food, in which the chest is most deep and 
capacious, proportionately to the length of current the circu- 
lating fluid has to run ; and the same remark will, I believe, 
be generally found applicable to the human species. 
I am, my dear Sir, 
with great respect, 
sincerely yours, 
THO, AND. KNIGHT. 
Downton f Feb, 2 6 , 1810. 
