10GO 



THORAX. 



inflate them by expanding them (removing the 

 external atmospheric pressure), and allow the 

 air to drop into the air vesicles by its own 

 gravitation (as in living respiration), when 

 they would in all probability collapse freely 

 to their original position. When they are in- 

 flated by expansion (the natural way of life) 

 the delicate cells of the lungs can safely resist 

 a force of from 3 to 9 inches of mercury, or 

 from 40 to 121 inches of water (see next 

 column) ; but when expanded by inflation, 

 their collapsing power was damaged so that 

 it could sustain only 17 or 20 inches of water. 

 This is worthy of notice in resuscitating the 

 apparently asphyxiated person, at which times 

 we have long been of opinion that bellows 

 and pumps are highly dangerous instruments 

 to use for maintaining artificial respiration. 

 Of the muscular contractility of the lungs. 



In the trachea transverse muscular fibres 

 extend across posteriorly, connecting the tips 

 of the incomplete rings of cartilage. In the 

 smaller bronchi they encircle the whole tubes, 

 and there appears to be little doubt but that 

 these circular fibres are to be found in every 

 part of the air tubes as far as the terminal air 

 vesicles. 



Physiologists have disputed whether these 

 fibres are muscular or not ; if muscular, they 

 are important agents in respiration, acting as 

 a series of little expiratory muscles. 



Dr. C. J. B. Williams lately read a paper at 

 the meeting of Glasgow (September 1840), 

 upon the subject.* He experimented upon 

 the lungs of some of the lower animals, 

 several dogs, a rabbit, a bullock, a horse, &c., 



as soon as possible after death, submitting 

 their lungs to galvanic stimuli, and securing a 

 haemadynamometer with a stop-cork to the 

 trachea. He found that, upon applying this 

 stimulus, the fluid in the bent tube rose from 

 1 to 2 inches, and it immediately fell on break- 

 ing contact. This effect could only be pro- 

 duced by muscular contraction. 



Kolliker, a very accurate observer, confirms 

 these views.-}- He found in man, in the larger 

 and finer bronchial tubes, a coat formed 

 of annular fibres, in one or more layers 

 according to the size of the tube, consisting 

 of unstriped muscular fibres ; and over this 

 coat a thin layer of fibro-cellular tissue 

 with nucleus-fibres. He found no mus- 

 cular fibres directed longitudinally. He ob- 

 serves, " In former observations I thought 

 I had convinced myself of the existence of 

 unstriped muscular fibres in the air-cells; but 

 in my resumed examination of the lungs of 

 man and mammalia, I can with certainty see 

 nothing distinctly characteristic as such mus- 

 cular tissue." Our knowledge of these cir- 

 cular muscular fibres was first chiefly derived 

 from the researches of Reisseissen. Laennec 

 considered spasmodic asthma to be assignable 



* The Pathology and Diagnosis of Diseases of 

 the Chest, 8vo. by Dr. C. J. B. Williams, 1840, Lon- 

 don, p. 320. 



\ Beitrage zur Kenntniss der glatten Muskeln 

 in the Zeitsehrift fur Wissenschaftliche Zoologie, 

 H. i. S. 40. 8vo, 1848. 



to a spasm of these circular fibres. We are as 

 yet ignorant of the possible extent of contrac- 

 tion of these fibres. The discharge of air is 

 paramount, and that from the most remote vesi- 

 cle ; and we know that by no mechanial means 

 can we obtain this, and therefore a molecular 

 power is necessary, which we readily imagine 

 can be obtained by these tissues acting so 

 as to give a peristaltic motion, and thus dis- 

 placing from every individual vesicle the de- 

 licate stream of air necessary to be dis- 

 charged. We do not need these tissues for 

 inspiration, because the atmosphere, by its 

 mere weight, can penetrate into the most 

 remote air-cell, overcoming all the friction 

 against the sides of the air-tubes. The in- 

 spiratory volumes of air are but for one pur- 

 pose, to aerate the blood ; but the expiratory 

 volumes are for the voice and other purposes 

 sometimes requiring great force to aid in cer- 

 tain expulsive efforts. 



OF RESPIRATORY MUSCULAR POWER. 

 Young falls into an error in supposing " that 

 in muscles of the same kind the strength 

 must be as the number of fibres, or as 

 the extent of the surface which would be 

 formed by cutting the muscle across ; and it 

 is not improbable that the contractile force 

 of the muscles of a healthy man is equivalent 

 to about 500 Ibs. for every square inch of the 

 section."* When we examine men we find 

 no such calculations are to be relied upon. 

 It is very common to find two men of cor- 

 responding dimensions produce very different 

 effects upon any dynamic instrument. 



The respiratory power may or may not cor- 

 respond with the general development of mus- 

 cular force. 



We have submitted 1.500 men of various 

 classes to an experiment upon the inspiratory 

 and expiratory power. The resistance to this 

 power was a column of mercury, thehcsmacfy- 

 namometer, or bent tube, first used by Dr. 

 Hales. He observes, " A man, by a peculiar 

 action of his mouth and tongue, may suck 

 mercury 22 inches, and some men 27 or 28 

 inches, high ; yet I have found by experience 

 that, by the bare inspiring action of the dia- 

 phragm and dilating thorax, I could scarcely 

 raise the mercury 2 inches." f Hales appa- 

 rently never tested the expiratory power. 



We connected the column of mercury witli 

 the index on a dial plate, which represented the 

 inches and tenths of inches of mercury lifted. 

 A tube was adapted to fit the nostrils through 

 which the inspiratory or expiratory effort was 

 made. By the former the index was moved 

 in one direction, and by the latter in the con- 

 trary direction ; each half of the dial plate 

 representing, respectively, inspiratory and ex- 

 piratory power, with expressive words at- 

 tached, as follow : (See top of next page.) 



It will be observed that the figures on each 

 side of the same word differ in their value, 

 those of the expiratory side ranging about one- 

 third higher than those on the inspiratory side. 



* See Nat. Phil. Lond. 8vo, 1845, p. 99. 

 t Stat., vol. i. p. 267. 



