735 
1879-J oV M ie Natural Duration of Life . 
subject of the relation of occupation to health and longevity 
from the registration reports of England and America, and 
he also studied the lives of many prominent brain-workers. 
So far from confirming the generally-received theory that 
the mind can only be used at the expense of the body, his 
researches led him to conclude — 
1. That the brain-working classes — clergymen, lawyers, 
physicians, merchants, scientists, and men of letters 
— live very much longer than the muscle-working 
classes. 
2. That those who follow occupations that call both 
muscle and brain into exercise are longer lived than 
those who live in occupations that are purely manual. 
3. That the greatest and hardest brain-workers of history 
have lived longer on the average than brain-workers 
of ordinary ability and industry. 
4. That clergyman are longer lived than any other great 
class of brain-workers. 
5. That longevity increases very greatly with the advance 
of civilisation, and that this increase is too marked 
to be explained merely by improved sanitary know- 
ledge. 
6. That although nervous diseases increase with the in- 
crease of culture, and although the unequal and 
excessive excitements and anxieties attendant on 
mental occupations of a high civilisation are so far 
both prejudicial to health and longevity, yet these 
incidental evils are more than counterbalanced by the 
fadt that fatal inflammatory diseases have diminished 
in frequency and violence in proportion as nervous 
diseases have increased ; and also that brain-work is, 
per se, healthful and conducive to longevity. 
The title of Dr. Richardson’s Address was “ Salutland ; 
an Ideal of a Healthy People.” About three months ago 
Dr. Richardson and Mr. Chadwick discussed with Professor 
Owen the question of longevity and the natural duration of 
life of different classes of animals. 
“With his usual scientific accuracy and industrious re- 
search, Owen had estimated, from various data he had 
collected, the natural term of life of that curious animal, 
the hippopotamus. He had learned that its term of life is 
thirty years. He explained to us the mode by which he had 
arrived at that fadt ; how into the calculation it had been 
necessary to take into account the dentition of the animal ; 
the stages of development ; the natural wearing out of the 
