From the earliest period of physiological re search, as usual, totally opposite opinions have alternately prevailed as to whether the lungs themselves are active in the respiratory move ments. Averroes, Riolan, Planter, and Bre mond*, were in favour of their independent action ; and Bartholin, Diemerhoeck, Mayow, and Haller t, opposed to it. Their elastic con tractility can only have been lost sight of by reason of their quick contractible power ; for immediately the thorax is punctured, before parts are cleared away sufficiently to give a view of the contents of the thorax, the lungs have collapsed to their minimum, and a vast space is always presented between the lungs and the thoracic wallsovhich, by the old anatomists, even in the time of Hoadly (1740), was con sidered to contain air necessary for respiration.
Dr. Carson of Liverpool appears to have first noticed this elastic power of the lungs. He judiciously observes : " Breathing is, in a great measure, the effect of this intermin able contest between the elasticity of the lungs and the irritability of the diaphragm." $ In his experiments upon the lungs of some lower animals (bullocks), he found a collapsing power equal to a column of from 12 to 18 inches of water ; in a calf about 18 inches ; and in a dog about 10 inches.
In these experiments, the lungs, when in situ, were inflated to their maximum. Pro bably the ribs interfered by their resistance in aiding the collapse of the lungs. Never theless, at all times of inflation, even when the residual volume only was in the lungs, there was an elastic power in operation. Mr. Gulliver informs us, that from an examination of the lungs of man and the lower mammalia he has been led to infer that the elastic tissue is an important agent in expiration. This tissue, he says, may be seen to invest the entire surface of the lungs, forming a strong, elastic, though delicate, capsule to the organ. This investment of the lungs in the horse, he informs us, •resembles the fibres of the ligamentum nuchm and the fibrous coat of the aorta of the ox, as depicted in Gerber's Anat. pp. 54, 55.
The longitudinal fibres which enter into the structure of the air-tubes throughout their entire extent are very elastic, like the coats of the arteries, and these are justly supposed to possess the power of contracting each mi nute ramification of the lungs. When this elastic power is at rest, and the lungs are col lapsed to their minimum, no external pressure can discharge the remaining volume of air, because the very pressure, to accomplish this, compresses the exit tube in some part of its course. The elastic contraction of each tube
acts somewhat like the vermicular motion of the intestines, causing a specific diminution of calibre upon each part of the column of air in a ramification, driving it forward. But when the elasticity has arrived at its mini mum, and this tissue is quiescent, we cannot extract any more air from the lungs, because the vermicular expelling power derived from this elastic tissue ceases to act. The col lapsing power of the lungs acts in the same di rection as that of the ribs, but with less force.
According to Tables 0 and P. the total elas tic collapse of the male lung was equal to about 4301 grs. or nearly 10 oz. avoirdupois (9.8) upon the superficial square inch of that organ, and in the female about 5060 gr. or 11.3 oz. upon the superficial square inch. We think, taking all things into consideration, that it is safe to say, in making a deep inspiration for the vital capacity-volume, that we may estimate the elastic collapsing power of the lungs at one half lb. avoirdupois, per superficial square inch ; therefore, allowing the mean superficial mea surement of the male lung to be 300 in. and the female 247 in., that the gross resistance, by the elasticity of the lungs against the inspiratory muscles, would be in the male 150 lbs., and in the female 123 lbs. This is to be added to the elastic force of the ribs (Table N). In the female an unknown portion of the residual volume escaped before we could connect the hxmadynamometer ; for the next volume added, of 90 cubic inches in the man with all his residual volume, the collapsing power was 7.2 in., and in the female, with the addition of 100 cubic inches, it was 5.5 in., which about makes up the difference of 2 in. of collapsing power lost by the accidental escape of the residual volume.
In the case of two healthy persons ex amined immediately after death,— E. F. M., male, height 5 ft. 9 in., weight 10 st. 10 lbs., circumference over the nipples, alive, 38 in. ; dead, 36 in. — died with an expiration, — we, by means of the lmnadynamometer, contain ing water, attached to the trachea, found, with different volumes of air in the lungs, the following elastic collapsing power (tem perature — of body 98.5° Fahr. — of atmo sphere 59.5', barometer 29.753).