Benjamin Franklin

Dear Doctor,

Your observations on the causes of death, and the experiments which you propose for recalling life in those who appear to be killed by lightning, demonstrate equally your sagacity and your humanity. It appears that the doctrine of life and death in general is yet but little understood.

I have not seen the book you mention of Tissot, on the diseases of literary men; but have perused another piece of his on the diseases of people of fashion, which contains many useful cautions.

I have long been satisfied from observation, that besides the general colds now epidemic, people often catch cold from one another when shut up together in small close rooms, coaches, &c. and when sitting near and conversing so as to breathe in each other’s transpiration. I think therefore that when you are obliged to sit near a person afflicted with a cold, it would be prudent to turn your face a little aside.

The opinion you mention as universal in France, that sleep in a room with green vegetables or plants is dangerous, is an error. You will find abundant testimony in contradiction of this superstition from the observations of physicians.

Confined air, when saturated with perspirable matter, will not receive more; and that matter must remain in our bodies, and occasion diseases. But the air we breathe is never so confined, but that it mixes more or less freely with the external air.

I have long been satisfied that cold air is wholesome and warm air relaxing. I therefore neither close my chamber door nor window at night, but leave some opening for the admission of fresh air, and I constantly sleep with open windows, even in the coldest weather.

But what I principally wish to insist upon is this: I rise almost every morning and sit in my chamber without any clothes whatever, half an hour or an hour, according to the season, either reading or writing. This practice is not the least painful, but on the contrary agreeable; and if I return to bed afterwards, before I dress myself, as sometimes happens, I make a supplement to my night’s rest of one or two hours of the most pleasing sleep that can be imagined.

I find no ill consequences whatever resulting from it, and that at least it does not injure my health, if it does not in fact contribute much to preserve it. The air bath has, at least, the merit of supplying us with one of those pleasing sensations of which we have been cheated by our dress. The sensation is exquisite, and I flatter myself that the practice may be of great service.

In support of this opinion I would observe, that the most minute vessels are necessarily compressed by clothes, however loose, which compression prevents the due perspiration and free circulation of the fine fluids, and may therefore occasion numberless disorders.

Experience teaches, however, that the degrees of heat most friendly to health are those of the common temperature of the air in the shade, in this climate, during the months of May, June, July, and August.

I shall now conclude this long letter with a Dutch proverb, which, being translated, is: The best physicians are Dr. Diet, Dr. Quiet, and Dr. Merryman.

I am, with great esteem, dear Doctor, your most obedient humble servant,

B. Franklin