On the Capacity of the Lungs, and on the Respiratory Functions, with a View of Establishing a Precise and Easy Method of Detecting Disease by the Spirometer

ON THE RESPIRATORY FUNCTIONS.afterwards, this truth is disputed, and even then not generally believed; so that from Galen to Robert Boyle, naturalists, physicians, and philosophers, explained the simple operation of breathing in three ways:First,-" That by the dilatations of the chest, the contiguous air is thrust away, and that, pressing upon the next air to it, and so onwards, the propulsion is continued till the air is ' driven into the lungs' and so dilates them."Second,-That the chest is like to a pair of common bellows, " which becomes to be filled because it is dilated."Third,-" That they are like a bladder, which is therefore dilated because it is filled."Boyle, the greatest philosopher in his day, adopts the view of the bellows action, and that the lungs are filled with air, because the chest is dilated, and that without the motion of the thorax they would not be filled." Indeed," says Boyle, "the diaphragm forms the principal instrument of ordinary and gentle respiration, although to restrain respiration (if I may so call it), the intercostal muscles, and perhaps some others, may concur."* About this time (1667), Richard Lowert correctly describes the respiratory act, and makes a dog breathe like a brokenwinded horse, by dividing the phrenic nerve.These truths were not then relished, so that for nearly 100 years afterwards, a number of unfounded hypothetic and contradictory specn- lations continued to prevail.A Latin tract t appeared in 1671, and was noticed in the 5th volume of the Transactions of the Royal Society, p. 2141, wherein the author contends that the "lungs do not follow the motion of the thorax and diaphragm, nor are moved and plied like bellows, and that the diaphragm cannot move up and down ;" but the breath- ing operation is accounted for by curious motions, termed "Extrosum, Introsum, Intumescence, Propulsion," &c.There appears no proof that Galen believed in the exist-