Excerpt from An Introductory Lecture, Preliminary to a Course on the Institutes of Medicine: Delivered on the 9th of October, 1850, Before the Medical Class of the University of PennsylvaniaThe atmosphere is vitiated and contaminated in various ways. Respi ration is the most common. Accurate observations have established that from 4 to 5 per cent. Of carbonic acid is contained in the air expired by a. Male adult, and a somewhat larger per centage of oxygen has disappeared. The amount of air passing through the lungs in 124 hours, is about 400 cubic feet, which loses about 20 cubic feet of oxygen, and receives about 16 cubic feet of carbonic acid. The same air breathed three or four times becomes poisonous. One per cent. Of carbonic acid in the air, if breathed for some time, is prejudicial and death has been caused by a vitiation of not more than 12 or 15 per cent.These facts show the importance of free ventilation to the preservation of health, and the free exercise of the functions, mental and physical.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.