1058 



THORAX. 



TABLE N, Inspiratory Muscular Power 

 (corrected). 



Thus we see that in the mere act of or- 

 dinary breathing there is an elastic resistance, 

 independently of the elastic force of the lungs, 

 equal to more than 100 Ibs. This is to be 

 lifted 18 or 20 times every minute of our life. 



OF THE ELASTIC POWER OF THE LUNGS. 

 Independently of the powerful collapse 

 of the ribs and their cartilages, expiration 

 is greatly aided by the elasticity of the lungs 

 themselves, which at all times, and in all the 

 stages of respiration, are tending to collapse 

 upon themselves ; and hence, immediately 

 upon puncturing the thorax, the lungs col- 

 lapse to half their dimensions. 



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- 

 niond*, were in favour of their independent 

 action ; and Bartholin, Diemerhoeck, Mayow, 

 and Hallerf, 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 walls, which, 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." J 

 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 

 siftt, were inflated to their maximum. Pro- 

 bably the ribs interfered by their resistance 

 in aiding the collapse of the lungs. Never- 



* Mem. cle PAcad. des Sciences, Paris, 1739 : 

 Miiller, p. 346. 



t El. Phys. t. iii. 1. viii. p. 22fi. . 

 j Phil. Tr. 1820, part i. pp. 42, 43. 



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 say?, 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 nuchaa 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 O and P. the total elas- 

 tic collapse of the male lung was equal to about 

 4-301 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 sav, in making a deep inspiration for the 

 vital capacity-volume, that we may estimate the 

 elastic collapsing power of the lungs at one half 

 Ib. 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 Ibs., and 

 in the female 123 Ibs. 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 haemadynamometer ; 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 Ibs., 



