Report of Experiments on the Physiology of the Lungs and Air-tubes. By CHARLES J. B. WILLIAMS, M.D., F.R.S. WHEN at the request of the Medical Section of the British Association, I undertook three years since to investigate experimentally several doubtful points respecting the properties and offices of parts of the respiratory apparatus in the higher classes of animals, I hoped to be able to include in the inquiry the chemical process of respiration, and the vital effects of its interruption. Professional engagements having obliged me to relinquish these points, I have restricted my attention to others more immediately bearing on practical medicine. The chief of these are the contractility and sensibility of the air-tubes and lungs. It has long been a matter of controversy whether the lungs and air-tubes are more than passive in the motions of respiration; whether they possess any self-contracting or expanding power, independent of the muscles which affect the capacity of the chest. Different writers, both ancient and modern, have maintained opposite opinions. Laennec, after Sennert, Bremond and others, attributed to the lungs both a self-contractile and self-expansive power, in addition to their mechanical or elastic properties. Haller, on the other hand, was led by experiment to deny that any independent vital motions are exhibited by the lungs of animals, corresponding with those of respiration; and Müller has confirmed these negative results. Within the last few years certain writers in this country and in France*, have denied altogether the muscular contractility of any part of the air-tubes below the larynx. These negative observations are in opposition to the generallyreceived opinion, derived chiefly from the anatomical researches of Reisseissen, that the circular fibres of the air-tubes, from the trachea to their terminations, are muscular. Very few attempts have been made to solve this problem by experiment. Varnier and Wedemeyer only succeeded in exciting partial contractions in the smaller bronchi; but after all their results, Müller concludes that "it is remarkable that there exists at present no direct proof of the contractility of the muscular fibres of the trachea and its branchest. I need scarcely remark, that this subject is by no means one of merely speculative interest. Much of the pathology and * MM. Trousseau and Belloc, Dr. Geo. Budd, &c. treatment of various diseases of the respiratory organs, especially asthma, is at present founded on the supposition of a muscular contractility of the air-tubes, the very existence of which is stated by one of the most eminent of modern physiologists to be little more than assumed. The chief objects of the following experiments were to test the existence of muscular irritability in the air-tubes; and if such were present, to determine its character, and the circumstances or influences which could affect or disturb it. The experiments were performed at the London University College, and in several of them I was kindly assisted by Professor Sharpey, Mr. James Blake, Dr. Davison, and several of my pupils, especially Messrs. Blomfield, Carlill, Parkes and Jos. King. In most of the experiments I made use of Poiseuille's hæmadynamometer, which is a tube bent like an inverted siphon, containing a coloured fluid; the short limb of this tube, furnished with stop-cocks, being adapted to the windpipe or one of its branches, the column of fluid within would be readily moved by any contraction of the air-tubes or lungs, causing pressure on the air in it: and the rise or fall of this fluid was measured by a scale divided into inches and tenths. 1. A dog was killed by pithing. The chest being immediately opened, the lungs collapsed completely. They were taken out with a part of the trachea, which was then tied to the brass tube of the hæmadynamometer (or as I shall call it, the dynameter); on completing the communication by turning the stop-cock, the fluid in the tube oscillated several times to the amount of about one fourth of an inch. On passing a galvanic current, from a trough of thirty three-inch plates, from the margin of the lungs to the brass tube in the trachea, the fluid rose quickly, but gradually, nearly two inches; it sunk speedily on breaking contact; again rose on repeating it; but fell slowly when the contact was continued for some seconds. When the current was passed only through a single lobe, the rise was still distinct, amounting to three or four tenths of an inch. The rise was repeatedly produced, but to a diminishing extent, and after two or three minutes the effect seemed to be exhausted. 2. The preceding experiment was repeated with eight dogs of various sizes, with similar results. The rise of the fluid column caused by galvanising the whole lung amounted at first to from 1 to 2 inches, but afterwards gradually diminished. If the current was passed continuously for some length of time, the fluid in the tube fell, and could not be raised by the galvanism for a minute or two after. It was found also that inflating the lungs impaired the effect of the current. On repeating the experiments further, it was found that the irritability was only exhausted for a time; and on waiting two or three minutes between each application of the galvanism, the liquid was raised again and again for upwards of an hour; at first to the extent of one or two inches, but afterwards to a gradually diminishing extent, until all effect ceased. So, too, although no effect ensued immediately after inflating the lung, yet on waiting a minute or two the contraction took place, only diminished in degree by the compressed state of the air, which required more contractile force to move it. The fall on interrupting the current was pretty rapid, the fluid recovering its level in from ten to twenty seconds. 3. Several trials were made to compare the contractility of the smaller and the larger bronchial tubes respectively. When the galvanism was passed along only the margins of the lobes, scarcely any contraction ensued. When passed from the margin to the middle of the lobes the column rose two or three tenths and soon subsided. When passed across a lobe, at right angles with the chief tubes, the rise was from two to four tenths. But the greatest amount of contraction was caused by passing the current from the margins of the lobes to the larger tubes, or across the direction of these tubes, especially near the bifurcation of the trachea. The rise produced by galvanising these portions could be also renewed at intervals for a period much longer than in other parts. 4. The preceding experiments were all made on the lungs removed from the body immediately after death. I tried to obtain the same results with the lungs in the body; but it was not easy to galvanise the lungs without affecting the muscles of the chest, the contractions of which might interfere with the results. The expedient adopted was, immediately on the death of the animal to adapt the dynameter to the trachea; then to open the chest and break back the ribs, and having separated the lungs, to pass between them and the walls of the chest a piece of oiled cloth, and then to apply the galvanic wires to different parts of the lungs. This experiment gave less distinct results than when the lungs were removed from the body. It was repeated five times; but it will be sufficient to describe one instance in which the galvanism was tried on the par vagum as well as on the lungs themselves. A large dog was pithed, and the dynameter adapted to the trachea. On opening the chest, the collapse of the lungs caused the fluid to rise three inches. The vagi being exposed in the neck, one was pinched; it caused no effect on the dynameter. The other vagus was then galvanised across and along a portion of it; no effect followed in the bronchial tubes, but the oesophagus was strongly convulsed. The nerve was then separated and the galvanism passed through it to the base of the lung; this raised the dynameter only a tenth. On passing the current from the base of the lungs to the trachea the column rose more than an inch, sinking again rapidly on the withdrawal of the galvanism. : 5. In all the preceding experiments the animals were killed by pithing other modes of death were afterwards tried. A rabbit was killed by a blow on the back of the neck. The lungs and trachea being cut out, moderately inflated and galvanised, little effect was produced in the first ten minutes, but the column had gradually sunk about three tenths of an inch, after this the galvanism repeatedly raised it two tenths. 6. A large dog was bled to death by dividing the jugular veins. Death was preceded by very deep and rare breathing; the heart beat a few pulses after respiration and sensibility had ceased. On adapting the dynameter to the trachea, the column was stationary; on opening the abdomen it sunk half an inch. On opening the chest it rose five inches. After taking the lungs out of the body, galvanism failed to raise the column; but this failure probably arose from the tube being obstructed with viscid mucus; for on applying the wires to the bifurcation of the trachea the tubes were seen to contract distinctly. This suggested another mode of observation which had been distrusted before, as liable to error. The lungs were cut by sharp scissors at right angles to the chief air-tubes; the open sections being galvanised contracted to half, and in some instances to less than half their former diameter. To ensure accuracy, the gaping ends, as soon as cut, were measured by compasses or tubes of similar size. The contraction was most distinct in the middle-sized tubes, and those of the size of a crow-quill. One of these closed completely. These results were obtained for half an hour after death, and long after the heart had lost its irritability. 7. A large greyhound was killed by pithing. The lungs being removed, one lobe was tried by galvanism and the dynameter, with the usual results. A large bronchus of another lobe was then cut open longitudinally, laid flat and then galvanised. It became hollow and contracted a third, and at one part half its diameter. The divided ends of other bronchi also contracted to less than half. In one instance, when the interior of a large bronchus was galvanised, bloody mucus was expelled from one of its branches across which the current passed. 8. A bullock's lung was experimented on about twenty minutes after death, which was caused as usual by a blow on the |