of each; the bottoms ground plane. They were attached bottom to bottom, by means of gas lute, with the holes in apposition. A piece of wood, having one end tapered, as a plug for the holes, and long enough to extend without the mouth of the jar, was fixed in the holes. Two stop-cocks were affixed to a bladder, one at the neck and the other at the fundus, so as to inclose a space capable of containing ten cubic inches. The bladder was filled with expired air expelled immediately after having made an ordinary inspiration; it was passed from thence into one of the jars; the operation was repeated till the jar was full; and its mouth was then stopped. Here was collected a quantity of air which had been inspired, and expired, each portion was the last taken in, and none of it had passed beyond the mouth and trachea; if it, therefore, contained carbonic acid, from some substances within these parts, it must have obtained it. The empty jar was filled with transparent lime-water, the plug withdrawn, and the mouth stopper applied, the limewater dropped slowly through the air, and the air rose in small bubbles through the lime-water, the jars were turned several times. At length the bottom holes were again stopped, fresh air and lime-water introduced into the jars in like manner as before, and the whole process renewed, taking care to retain all the chalk deposited. These operations were continued till a considerable quantity of chalk was collected. This experiment affords proof that the carbon of expiration is not at all received from the blood in the air-cells, but that a portion at least is derived from substances within the passages. So far it is conclusive, but it is desirable to find the substance which produces it, and the method by which it is generated; the following hypothesis is offered in explanation. The only matter to be found in the passages is the mucus, poured into them by proper secretory organs. Physiologists say that all the fluids of the body contain salts in the alkaline state, except the mucus of these passages, in which they are in the neutral state. It is assumed for proof is not attainable, that this particular fluid is also sent from secretory organs having alkalies in solution, that having all favourable circumstances in attendance for the purpose, the oxygen of the atmospheric air is attracted by the alkali, that carbonic acid gas is disengaged by the new combination, mixes with the air contained in the pas sages, and is expired together with it. Whether this explanation be received or not, still it is no less certain that carbonic acid is generated in the passages, and that it can emanate from no other substance than the mucus thereof. A very large proportion of the bulk of the lungs consists of cells, their dimensions are enlarged by inspiration, and lessened by expiration, and the variation of dimension is in exact proportion to the amount of air taken in and expelled by these two acts; still they are in every state full of air. It is in the cells that the function is ex clusively performed; air is an agent in the function; the air which inhabits them must be that agent. The method by which this air is supplied, and its use in the function must be explained. It has been supposed that the quantity of air expelled by expiration is the same as that taken in by inspiration, and taking it for granted that air is an agent in the function, and seeing that no air is dissipated in the operation thereof, an anomaly was suspected, for the universal order of nature, especially throughout the animal system, is, that all matters in action suffer waste, but in the instance before us it seems to be interrupted, for if the air taken in is returned without diminution of quantity it loses nothing. If it be shown that the expelled air differs from the inspired only in quality though not in quantity, or that its bulk is increased by addition during its stay in the lungs, the difficulty will be removed. It is vulgarly known that the air or breath comes from the lungs loaded with a large quantity of vapour; it is true vapour is condensed as soon as it comes in contact with the external air, vapour which is only in simple mixture with the air of respiration, but vapour holds place in warm air in two ways, first by simple mixture, and secondly by chemical combination; in the latter case the water is not separable from the air except by chemical decomposition. No circumstances can be conceived more favourable for this combination than those existing in the lungs, contact of steam and warm air, and pressure. The thermometral temperature of breath was ascertained to be 76°. Temperature of room 62°. Temperature of water in the pneumatic trough was raised to 76°. A bladder capable of containing thirty cubic inches, having a stopcock at the neck and another at the fundus, was filled with atmospheric air, the nozzle of one stopcock closed was fixed in the mouth of the double jar, and the whole of the other taken into the operator's mouth. The air was inhaled into the lungs, immediately expelled into the bladder again, and thence passed into the jar; the jar was filled by repetitions of this process, and left with the under mouth open in the water. At the expiration of twentyfour hours 11 cubic inches of water had risen into the jar. Four drachms of caustic potash were put into the jar, and five inches more of water had entered in twelve hours. A change of weather afforded an opportunity of repeating the experiment with advantage. The temperature of the room was 72-of breath 82°-in nine hours 12 cubic inches were condensed-caustic potash absorbed six more. These experiments demonstrate what was clear enough before, that atmospheric air taken into the lungs is there increased in temperature, and therefore in space, and that it is further increased in quantity by addition of water in the state of vapour; the necessary result of which must be, that as the same bulk of air is returned as was inhaled, some of that which had been inspired must be left behind, expiration being finished, and the quantity left must be exactly equal to the increase of bulk attained through increase of temperature, and through addition of vapour. Caloric expands, and VOL. XVII. No. 33. vapour takes the place of atmospheric air so expanded, detaching a quantity proportionate to its own bulk, so that this amount of displaced air remains in the lungs after expiration is completed. But it was conjectured that the foregoing experiments did not declare the full amount of air left behind, and the following confirmed the conjecture. Three large bladders were procured, and two circular pieces of wood, grooved at the edge like the wheel of a ship's block, and perforated in the centre by a hole half an inch in diameter; two bladders were attached to each piece, so as to maintain communication with each other by means of the holes. To the opposite extremity of one of the last bladders in the line a stopcock was fastened. This apparatus was filled with atmospheric air amounting to 350 cubic inches. This air was drawn into and expelled from the lungs by 70 inspirations and as many expirations, one of the last succeeding each of the former, the whole was left in a cold cellar 24 hours, at the expiration of which time upwards of 100 cubic inches were found to have been lost, being about 1 cubic inch from each inspiration, and this under the influence of simple condensation alone; the air still held water in chemical combination, and it will not be overlooked that if this had been removed by decomposition, the result would have been 18 much more favourable. The residual air then is supplied by the respiration, and a quantity equal to that lost is consumed by the function during the time occupied by every act of respiration. Concerning the use of the residual air, it is concluded from the foregoing inquiry, that air having once entered the cells, never returns into the atmosphere, but on the contrary is constantly receiving accession from it; indeed, were there no waste, and the same quantity were returned as had been received by the different acts of the organ, the residual air would ever be the same, unvarying in quantity, a portion of it would only change place, at expiration a portion sufficient to fill the space left by the air just expelled would rise from the cells into the passages, and at inspiration it would return to the cells, and make room for the atmospheric air that enters. This would be the mode of procedure if the capacity of the tubes and bulk of inspired air were equal, or if the latter exceeded the former, but if the capacity be inferior to the bulk, then a portion of air equal to the excess of bulk over capacity rises from the cells, and is thrown out of the mouth at expiration, and a like quantity of fresh air descends into the cells at inspiration, but the greater part of the contents of the cells moves to and fro as in the former case, the result would be scarcely different. Whichever then may be the state of the case, we cannot hesitate to admit that the residual air is the only inhabitant of the cells, and as it is universally known that the function is carried on in the cells and in no other part of the organ, the residual air must be regarded as the only agent in the process of renewal of the blood. The air receives caloric in the passages, acquires much increase of temperature, and consequently much augmentation of bulk; the air expired, indeed, on account of its short stay, is not much affected, but the alimental portions taken from each inspiration and the residual gain the temperature of the body. A quantity of water in the state of vapour becomes mixed with itanother quantity of water becomes chemically combined with it-its oxygen is continually attracted by a substance residing there, and entering into new combinations -and carbonic acid gas is continually being generated and mixing with it. All these changes are known to be in progress, because all expired air is increased in temperature-has water mixed-and in chemical combination-and exhibits loss of oxygen-and acquisition of carbonic acid. These changes are effected upon the air of inspiration during its momentary stay in the passages, and they must be more consider able upon the alimental and residual portions, which having once entered the passages never return. The alimental portion descends into the cells, and comes into action on the blood in this altered condition. Two ox lungs were procured, they were cut into narrow strips in the pneumatic trough, under a glass jar, and as much air as could be expressed was collected. A large coffee-mill was fastened to a log of wood, this was inverted in the trough, each strip of lung passed through the mill, and the air set loose directed into the jar. Into a jar full of this air, ignited charcoal was introduced, it was speedily extinguished. Phosphorus would not burn in it. Lime-water was poured in, and shaken together with it; a copious precipitate of chalk took place. Into a jar containing another quantity of the air a solution of sulphuretted hydro-sulphuret of potash was poured, and after shaking, and opening the mouth of the jar under water, it was scarcely perceptible that any water rose in the jar. In the jar again filled with another quantity of the air deprived of carbonic acid by means of quick lime, caustic potash was suspended, and the mouth of the jar sunk in water, after a few hours much water had risen. Thus it was ascertained that the residual air consists of water in chemical combination with it-of a large proportion of carbonic acid gas; perhaps it contains no oxygen, and if any, a very small portion. What other gases it contains was not discovered through want of acquaintance with chemical manipulation. A summary of the facts thus produced is this. But let it be premised, that the tubes ramify in the lungs, and terminate at about surface-that the cells are placed in rows an inch distance from each other on their parallel with them, and all around themthat the cells in contact with the tubes communicate with them by means of pores in the sides of each-aad that the cells communicate with each other by like means. In the ordinary process of respiration there is a pause, the moving powers rest after expiration has been finished, and before inspiration begins; in this state let the organ be contemplated: the cells and passages are all full of air. The muscles of inspiration are called into action-the cavity of the chest is enlarged-the cells are expanded— each cell is affected in an equal degree-the line of cells in the centre of the space between tube and tube attract air from the cells in contact and communication with them these last also from others attached to them each row in succession does the same-the last, or those in contact and communication with the tubes, attract from them-the membranous tubes expanded in circumference, and elongated attract from the cartilaginous bronchi―these enlarged in length attract from the trachea, mouth, nose and atmosphere. This will be the course of procedure whatever may be the relative capacity of the parts, and the amount of air taken in. But in the succeeding act of inspiration it will be necessary to consider it in two different relative states of capacity, first as though the volume of air inspired exceeded the capacity of the passages, and secondly as though it was equal or inferior to it. Following then the progress of the function, bearing in mind that inspiration and expiration are supposed to take in and send out an equal volume, these will be found to be the mode of proceeding, and result under the first consideration. The muscles of expiration act, the air is propelled from all the parts in the order in which it entered them reversed, all the air contained in the passages is sent out through the mouth and nose, and as much from the cells also as is equal to the excess of bulk of inspiration over and above the capacity of the passages. Say, for instance, that the capacity of the passages is 30 cubic inches, and the bulk of inspiration 40, then ten cubic inches of air will rise from the cells and be thrown out of the body. Besides this portion of air, another will rise from the cells equal in magnitude to the capacity of the passages, and occupy them; the cells too will remain full of air. The inspired air during its stay in these parts gives away part of its oxygen, which uniting with carbon existing in the fluid contained in them, forms carbonic acid, the new compound being of equal bulk with the oxygen which disappears. The air obtains also a quantity of water in the state of vapour. This body of air so changed, and augmented by addition, is further swelled by the expansive quality of heat, to which it is here exposed. A quantity of air equal to the magnitude acquired by these means is left behind in the passages after expiration, and besides it will be found that expiration is not really equal to inspiration, consequently another portion equal to the excess of inspiration over expiration is also left behind. This quantity of air so changed, deprived of some of its original components, and increased by addition of other matters, remains at the top of the column, in the mouth and nose, at the end of expiration, at the succeeding inspiration descends again into the cells, again at expiration ascends, but now not so high as its former position, by as much space as it at first occupied, a fresh quantity occupying that which has taken the same course and undergone the same changes as itself; at each succeeding inspiration it descends deeper and deeper, aud at each expiration rises less and less high, till it is spent in the object of the function. From the time of its entrance by the mouth, till it is wasted, it travels an incalculable number of times up and down the passages, and it must be plain that as the expired air undergoes so considerable a change during its momentary visit in the passages, this suffers an incomparably greater; perhaps it loses all its oxygen; it is known that it obtains carbonic acid, and a large quantity of water, in a state the most apt for using its affinities, and forming fresh unions. We know that the nitrogen returns unchanged and undiminished, but we do not know whether the nitrogen, carbonic acid and water, form any new compounds amongst themselves, or with other substances when they come into communication with the blood. The conjecture that they do carries with it much probability from the length of time they are returned in the passages and cells, subject to all the means of synthesis, and exposed to agitation, such a powerful auxiliary of the purpose. It has been seen that in this first assumed state of relative capacity of the passages and bulk of air a portion of the air, equal to the excess of the last above the capacity without coming in contact with the blood in of the other, will have entered the cells. It the cells, the seat of the function. may be objected to the present hypothesis, that this portion receives all the carbonic acid, contained in expired air, from the blood, to which it is in them exposed, and that all the oxygen lost is there given to that fluid. To this objection, the first experiment is a full answer; and it may be stated, in corroboration, that the same fluid (mucus) is poured into the cells as is found in the passages; therefore the same change takes place in them as in the passages, by the same process, between the same substances. If the second supposed state of parts exists, namely, if the magnitude of inspiration is equal or inferior to the capacity of the passages, then the same course of procedure will be observed, and the same result follow, as in the former case. This has been traced and pointed out above, except that none of the air will enter the cells or come in contact with the blood, and all the changes effected upon it will be wrought within the passages only. This account of the result of the process has reference only to the air expelled by expiration; but in this second supposed case, as in the other, there is a portion left behind by each act of expiration, which has been designated alimental, because it maintains the residual, the most important, vitally important, part of the air of respiration, the only part which has influence in the function, none other coming into contact with the blood of the pulmonary artery. Each alimental portion takes the same course, and rises and sinks in the same manner in the passages in this as in the former, and undergoes the same changes; the only difference is, that whereas, in the first, some of the atmospheric air taken in by inspiration goes directly to the cells, and is there exposed to the blood, and is expelled into the atmosphere by the succeeding expiration; in the second, all the air taken in by inspiration is confined to the passages, and all, except the alimental portion, is again expelled by expiration, LVI. CASE OF TIC DOULOUREUX, PRODUCED BY A SCIRRHOUS TUMOUR ON THE BASE OF THE BRAIN. BY JAMES HEYGATE, M.R.C.S. MRS. B. aged 53, the lady of Captain B. R.N. had been troubled some time with chronic inflammation in both eyes, and though the conjunctiva was considerably suffused with red blood, and lymph thrown out on the cornea, she felt no pain in the eyes. This inflammation reluctantly gave way to the usual remedies. She then complained of pain in the left side of the head, over the temple. This continued (with temporary relief from bleeding, blistering, &c.) for a few weeks, when the affection began to put on a more formidable appearance, and was marked with all the characteristic symptoms of that most painful disease, "tic douloureux." Paroxysms of severe pain extended over the cheek bone, just below the orbit, the ale of the nose and the upper lip, which was considerably drawn up, shewing the second branch of the fifth pair of nerves to be affected. The line of demarcation was most clearly drawn, the nerves of that side of the face being implicated only. The pain was not attended with any discoloration of skin, only numbness, and occasionally the cheek and tenple were puffed. Pressure neither gave pain nor produced relief: severe fits of pain would sometimes reach the ear, which led me to suppose that the portio dura of the 7th pair of nerves was affected. The digestive organs, in the earlier part of the attack, were not deranged. Thus things went on, with nothing decidedly and unequivocally to lead one to suppose that there was organic disease at the base of the brain; but my suspicions gradually began to strengthen, when no real, or hardly temporary benefit, followed the use of the most approved remedies; such as, externally, counter-irritation by blisters, tincture of |