PRACTICAL OBSERVATIONS OF INFLAMMATION OF THE SCLEROTIC

pulmonary tubere. Many years ago, whenasisting at the vivisection of a stunnd rsbbit, in which the trachea and larger bronchi were fully exposed, I was surprised to observe their muscular fibres contract, dimshing the diameter of their tubes, at each movement of inspiration. It is not the general belief that the tubes are contracted during inspiration, and expanded in expiration; but if we consider the anatomical structure of the lungs and the physical effects which the whole apparatus of respiration is intended to produce, it will be obvious that, had the bronchial tubesbeen made to contract during expiration, and expand during inspiration, as they are generally imagined to do, this would have defeated the object of bestowing on them any contractility or power of elastic expansion. The intention to be fulfilled by expansion of the chest through raising the ribs and depressing the diaphragm, is to cause the air to rush into the cells of the lungs: now, if the tubes all expanded at the same time as the thorax, say, for the sake of argument, to thesame extent to which the capacity of the chest had been increaed by its expansion, it is obvious that no air whatever would penetrate into the cells, as all that was drawn into the chest would be required to fill the tubes. Or, if the parietes expanded mucT, and the tubes comparatively little, the real vacuum in the air-cells would be only the difference between the increasedcapacity of the chest, and the increased space occupied within itby the expanded tubes. But on the other hand, if instead of expanding, the tubes contract at the moment that the chest expands, thus occupying a less space in its interior just when its capacity is greatest, it is obvious that a much increased vacuum will be formed, and that it will take place in the air cells where alone it is required; and thus, whatever air enters the chest goes directly to its destination, instead of lingering in the tubes. Taking this view, the operation of expiration as well as of inspiration, will be more intelligible, for it will be seen that if the tubes expand at the same moment that the chest contracts, the air cells will be submitted to direct pressure between the expauding tubes and the contracting thoracic parietes ; and while the air that has ceased to be serviceable to the animal economy is thus more effectually expelled from them, the way is at the same time more widely opened for its exit. It will be seen from the above, that inspiration is principally due to msc6ular action in the thoracic muscles, the diaphragm and the circular fibres of the bronchial tubes, whereas expiration depends more on cartilaginous elaticity, bringing down the ribs and expanding the tubes. If additional argument be wanting for the belief that the lungs must in themselves possess considerable power of inspiration and expiration, while within the unopened chest, independent of the expansion and contraction of the thoracic parietes, we would point to the apparently very -mall amount of abdominea respiration in a case of fractured rib, bandaged ecundum artem, and to certain states of syncope, etc., that will suggest themselves to each of us, in which respiration is maintained without any apparent thoracic or diaphragmatic motion. It appears, then, that contraction and expansion of the bronchial tubes is the only satisfactory mode of accounting for the well established fact, that the sound made by the inhaled breath rushing through the tubes towards the aircells is considerably more protracted than that made by the same air returming in expiration; for there does not appear sufficient difference in the forces exerted in drawing in and expelling the breath, to account for the difference of time occupied in its entrance and its exit, if the calibre of the tube remained the same. No sooner, however, do we admit that the air-tubes contract during inspiration, and expand during expiration, than the full value of a slight prolongation of the expiratory murmur becomes apparent as a consequence, and therefore as a certain symptom, of the deposit of tubercle in the parenchyma of the lung: for what change should we a priori infer to have taken place in the condition of the bronchi, if we found the expiratory murmur becoming as long, or nearly so, as that of mspiration, but that something had occurred to impede their elastic expansion, and that the tubes remained nearly of the same calibre in expiration as during inspiration? Now the part in which the earliest deposit of tubercle is found in the structure of the lung is known to be the cellular tissue immediately surroundingthe minute bronchi; and the natural effect of this would be to impair their elastic expansibility, and cause the difference of calibre of the tube in its utmost degree of contraction and expansion to be less than in health, and consequently the duration of the murmur of expiration to approach that of inspiration. I do not know that it is ever so protracted as to equal the latter sound; nor should we expect that the deposit of tubercle, although plainly calculated to interfere with the elasticity of the bronchi, should do away with the contractile power of their muscular fibres. What gives peculiar value to prolonged expiratory murmur as a reliable Symptom of phthisis is, that so far as I know, there is no other condition of the lung capable of producing it; cancer of the lung is the only disease that appears to me likely to do so, but whether it does or not, I have had no opportunity lately of ascertaining. The importance of possessing any symptom on which we can implicitly rely, independently of concomitant evidence, cannot be too highly appreciated in this disease, because it enables us to begin and follow up earnestly a course of treatment at a stage of the malady so early as almost to insure success; and a firm conviction that this symptom is truly diagnostic has this farther advantage, that, by the concentration of our attention upon it the ear soon becomes educated to a much finer discrimination of the presence or non-existence of tubercle than at first could have been thought possible, and in some cases a diagnosis may be made from this alone with a degree of certainty, that a stethoscopist without faith in it could hardly venture to found on the aggregate of all the other evidence derivable from auscultation and percussion. But it is not only in their bearing on the early discovery of tubercle in the lungs that the above considerations will be found interesting; for there are nervous affections of respiration, in which it is important to consider the action of the bronchial tubes, such for example as the anomalous sounds heard in some curious forms of hysterical spasm of the chest and throat, but more especially in spasmodic asthma, in which it is often most painful to the ear to listen to the effects of continued muscular contraction of the tubes during expiration. To the consideration of these very interesting subjects, and that of the early treatment of phthisis, I_hope soon to return in a future paper.