BOUGHT WIT6 the INCOME -FROM THE SAGE ENDOWMENT FUND^ THE GIFT OF Henrs W. Sage 1891 A^j.i^'m. .,..: s-Mj Cornell University Library QP 121.M31 Contribution to the history of the,respi 3 1924 024 794 871 .„»,, ^■^ Cornell University Library The original of this bool< is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924024794871 A CONTRIBUTION TO THE HISTOEY OF THE EESPIRATION OF MAN BEING THE OEOONIAN LECTUEES DELIVEEED BEFOEE THE EOYAL COLLEGE OF PHYSICIANS IN 1895 WITH SUPPLEMENTARY CONSIDERATIONS OP THE METHODS OF INQUIRY AND ANALYTICAL RESULTS WILLIAM MARCET, M.D., F.R.C.P., F.R.S. LONDON : J. & A. CHURCHILL 1, GEEAT MARLBOROUGH STREET 1897 TO MT FOEMER COLLEAGUE AT THE BEOMPTON HOSPITAL DR. CHARLES THEODORE WILLIAMS THIS BOOK IS DEDICATED AS A TESTIMONY OF AN OLD AND VALUED PEIENDSHIP A CONTRIBUTION HISTORY OF THE RESPIRATION OF MAN LECTURE I Mr Peesident axd Gentlemen, — Allow me to begin b}^ returning my best thanks for the honour of being called upon to deliver the Croonian Lectures for the present year. I am aware that it is no light matter to discharge this duty in a way befitting the Royal College of Physicians ; allow me, therefore, to apologise for short- comings. I propose in these four lectures to examine into certain features of human respiration, and the reason for my having selected this subject requires some little explanation. My summer holidays being formerly taken up with excursions into the high Alps, it was but natural that I should wish to inquire into the influence of altitude on respiration ; and having procured the necessar\' instruments, this investigation was pursued regularly every summer from the year 1876 to 1880. The inquiry showed clearly that there was a great deal more to be done on the subject of human respiration, and througli the kindness of Professor Schiifer, a laboratory having been placed at my disposal in the Physiological Department of University College in 1883, the work commenced in the high Alps was continued in London. 1 2 RESPIRATION OF MAN Thus from 1883 to 1896, or for twelve years, my inquiries have been carried on regularly.* The results obtained were communi- cated from time to time to the Royal Society under the form of a number of papers which have been published in the Proceedings of that Society, one of them appearing in full in the ' Philosophical Transactions.' After these lectures had been delivered it was suggested to me that they might with advantage be published in book form. On attempting, however, to carry out this object, many points appeared to require further investigation, and it became obvious that an addition to the lectui-es was indispensable in order to acquaint the reader with the methods of investigation adopted, and the details of the inquiry. Therefore, while maintaining the lectures as nearly as possible in their original form, a second part was introduced, headed " Methods of Inves- tigation and Aiialytical Results," which should be looked upon as the scientific exposition of the lectures. I propose in this first lecture to treat of the relations of the oxygen breathed to the life of tissues ; the second will be devoted to the various forms of respiration in man ; the third to the influence of the exercise of volition on respiration ; and the fourth to respiration carried on under exceptional circumstances ; concluding with remarks more especially medical in their character. The Vital Enbugy and Chemical Changes within tee Living Body The first question which offers itself to our consideration is the definition of the words vital energy — or vital force — or vitality. The cellular life of Virchow is power or energy existing in the cell and radiating from it ; this cell has oxygen as part of its molecular constitution, and with the aid of oxygen is constantly undergoing change or metabolism with more or less energy, according to age, * They have been continued till going to press in 1896. LECTURE I 3 health, &c. It might be considered as if a test of vitality was the degree of power with which life clings to certain living organ- isms, as happens in the case of seeds. Nobody now believes in the power of growth of mummy wheat, but reliable information on the temporary state of abeyance of life met with in seeds is to be found in 'Nature Notes' for 1895, where Dr Carruthers states that forty years ago Robert Brown succeeded in obtaining the germination of seeds of the " Nelumbian " water-lily, which had been kept in boxes for fifty years in Sir Hans Sloane's collection, and another 100 years in the herbarium of the British Museum. I am indebted to Dr. Carruthers' kindness for showing me those seeds preserved in acid, which had sprouted to the height of several inches. Moreover the 'Gardener's Chronicle' for March of the present year (1895) informs us that Dr Peter, of Gottingen, succeeded in obtaining the growth of seeds from the soil of a dense wood with trees 100 or 150 years old. Dr Peter claims to have proved that the seeds of many field and pasture plants retain their vitality considerably more than half a century ; and the author of the article referred to remarks that, supposing the conditions to remain exactly the same, there is no reason why such seeds should not continue to retain their vital force for an unlimited time. Casimir de Candolle undertook the following interesting experi- ment.* He enclosed in a tin box various kinds of seed, and placed it in what is called the snow-box of a refrigerating machine ; the ex- periment lasted 118 days, the machine working from eight to twenty hours daily. The lowest temperature obtained in the course of the experiment was —53-89° C, and the highest —37-78° C, with a mean temperature of -41-93° C. The seeds were afterwards sown in frames under glass, when nearly all those of wheat, oat, and fennel quickly sprouted; some seeds of lobelia germinated, others failed to do so. C. de CandoUe's theory is that under the influence of intense cold * " Sur la vie latente des Graines " (' Arch. Sc. Phye. et Nat.,' 1895). 4 RESPIRATION OF MAN the life of seeds is entirely arrested ; but if placed subsequently under conditions favorable to growth, they resume their functions of life. This phenomenon he compares to the inactive state of explosive mixtures which suddenly combine under favorable circumstances, such as the presence of heat. These remarkable phenomena might possibly find an explanation in the following considerations : — Life is a contest between vital energy and that other energy known as physical force, or chemical decomposition. The instant an animal dies chemical decomposition comes into play, and the first change to take place is a combination of the oxygen, which is part and parcel of the molecular tissue. Once that oxygen gone, recovery of life is impossible. It has been shown by various authors that an acid state of the muscles is found in animals very soon after death ; and experiments by Catherine Schepiloff appear to show that this acid, a result of decomposition, is the cause of rigor mortis. If we now return to seed life, we shall find that it may be protracted, as it were indefinitely, under conditions which entirely check decomposition. The seeds of Nelumbium. speciosum had dried up without undergoing any fermentation ; those cultivated by Dr Peter had clearly found in the soil they came from some preserving or sterilising material, and those exposed to intense cold were also in a condition preventing decomposition. It is but natural to conclude that a molecule of wheat or of any other seed under such conditions would retain its oxygen, though without being able to make use of it, because of the want of moisture, heat, and possibly also from the absence of certain bacilli which have been found necessary to vegetable growth ; hence the seed was not dead, but its life remained in a potential form, or under the form of vibrations too weak to produce any other effect than maintain themselves. So long as oxygen is present as a molecular constituent these vibrations will continue, but they will cease the instant this oxygen has disappeared. Given an animal suddenly placed in a state resembling death, but in which it could retain its oxygen, would it not be possible to maintain its life in abeyance, and ready to be restored on a return to favorable circum- LECTURE I 5 stances ? Raoul Pictet, the first to liquefy oxygen gas,* states in a paper published in the ' Archives des Sciences Physiques et Naturelles,' 1893, that he freezes slowly gold fish at a temperature ranging between 32° P. and 5° P., having left them previously for twenty-four hours in water at 32° F. If the solid block of ice holding the fish is allowed to melt slowly, the fish are observed to swim about in the melted ice as they did before, without any sign of discomfort. Pictet does not state how the fish were frozen, in his experiments, but it may be assumed that their temperature was lowered quick enough for the molecules of tissue to be frozen with their oxygen before any chemical action could possibly take place, and this oxygen by reacting on the molecule of tissue under favorable circumstances brought the fish to life, exactly as it was that the reaction of oxygen in the seed brought the seed to life after life had been quiescent for a hundred and fifty years. As already stated, no phenomena of metabolism can take place without the interference of oxygen or atmospheric air. The amount of air or of atmospheric pressure required may certainly vary within wide limits, and we all know that with training, and slow transition from the sea-side to lofty mountain stations, a considerable state of adaptation may be obtained. The action of oxygen in the living body, though but little understood, is a most inte- resting study ; and first of all I shall hope to be able to show in a conclusive manner that it is not the oxygen in the atmosphere which, by ofi'ering itself to the tissues, brings about the tissue changes, but because the tissues are undergoing change they require and reso]'t to the oxygen of the atmosphere ; hence the more active the change, the more oxygen required, and vice versa. It is often thought that an increase of COg is given out at the lungs because more air is breathed in a certain time ; this is quite a popular fallacy, as shown by the experiments of Pflijger. If a person in the state of rest should increase the ventilation of his lungs by forced breathing, although he will give out more COgfor a certain time, this COg will not result from increased * Ozygen was liquefied at the same time io Paris by Oailletet. 6 RESPIRATION OF MAN tissue change, but from the emission of some of the gas normally present in the blood, there being a slight excess of 00^ produced for the additional muscular work required by forced breathing. One of the many objects of oxygen in the body is to produce heat; some of this heat is transformed into motion, and is therefore not per- ceptible by the thermometer; while another portion is tangible, and can be determined by direct observation. In cold-blooded animals the heat produced is entirely transformed into motion, and therefore cannot be tested with the thermometer ; in warm-blooded animals there is an excess of heat ready for use; the latter find, therefore, in their bodies a large supply of power wanting in the former. If the production of heat is so intimately connected with life that life cannot exist in an active form without it, it will be interesting to consider the essential nature of heat. This condition or property of matter is looked upon by physicists as produced by a vibratory motion of the ultimate molecules of bodies, very feeble but very rapid. This movement is transmitted to a distance by means of a medium extremely elastic,- known as " ether." Ether, which is distributed throughout the whole universe, filling the intermolecular and interplanetary spaces, is supposed to be struck by the vibrating molecules of bodies, and from these shocks result undulations which transmit the movement and also the heat, in the same way as the undulations of sound propagate sound. From this view the warmest bodies will be those whose molecules vibrate with the greatest speed and amplitude ; bodies as they become warm or cold merely gain or lose motion. In the living body, heat, Avhether tangible or not, is continually being generated, and therefore the molecular vibrations producing heat are ever at work. The formation of heat in the body may therefore be looked upon as the very fundamental condition of life. If oxygen is thus indispensable to life, it must be within immediate reach of the living tissues, including protoplasm ; and there can be no doubt that it is carried through tissues and protoplasm, which seize upon it in accordance with their requirements. As far as muscles are concerned, we are able to follow the oxygen LECTURE I 7 into their very molecular structure. Ludimar Hermanu, in his work ' Stoff wechsel der Muskeln,' published in 1867, states that he has caused muscles to contract iti vacuo, and obtained CO3 in sufficient quantity to be determined. It is obvious that in this experiment there was enough oxygen in the substance of the muscle for its contraction as the muscle was in vacuo, and this oxygen gave rise to a production of CO2, and therefore of heat sufficient for the contraction. It cannot be doubted that, at all events in muscles, if not in all other tissues, oxygen enters into their molecular constitution ; and it has been suggested that molecules of muscular fibres are surrounded by a layer of oxygen in a feeble state of combination, and available for immediate use, the molecule seizing upon more oxygen from the surrounding tissues and blood as fast as the oxygen it holds in store is being used up. The adoption of this view of the constitution of muscular mole- cules will assist in explaining the immediate response of muscles to the action of the will. If after sitting quiet we suddenly raise a heavy weight or deliver a blow, the oxygen is there to do the work. A large salmon on its way up a river to spawn will leap a weir several feet in height with a single stroke of its tail ; how is the heat produced for that leap if not from the oxygen in the molecular structure of the muscles themselves ? We do not know, however, by what process this heat is produced. It is not considered as due to any direct oxidation, but according to Hermann would appear to result from some power of an explosive nature with which oxygen is concerned. This same author observes that we have not a single example of direct oxidation in the body. My remarks, so far, only apply to the necessity of the pro- duction of heat in living bodies, and do not suggest the original cause of the phenomenon. Here we stop short and have to assert our ignorance. There must be, however, a cause, a power producing these heat vibrations, a power which reacts against cold and generates heat where according to physical laws the body ought to cool, a power which builds up tissues and destroys them ; which may 8 RESPIEATION OF MAN produce, when required for muscular exercise, an amount of heat perhaps four times as great as in the state of rest. That power, whatever it be, must reside in the ultimate molecules of tissues, or perhaps it is the vibration of some intermolecular matter, and that power is intimately connected with heat vibrations, and cannot be exerted without the presence of oxygen gas. An apparently available means of judging of the primary cause of the formation of heat in warm-blooded animals would be to inquire into the reasons of the increase or decrease in the generation of their heat. A common cause for an increased production of heat in health is the influence of cold — either of cold air or cold water. An acces- sion of cold will produce an immediately increased amount of animal heat, as shown by the excess of OO2 expired; so that the increase in the production of heat will counterbalance the amount of heat withdrawn, the body retaining its normal temperature in spite of the cold. We shall now ask the question, why does an accession of cold produce increased animal heat ? To this I can only see one reply : because cold excites and increases the vibrations we look upon as the essence of life, and these vibrations are communicated to the living molecules when a greater development of chemical action ensues. To give you an idea of the effect of cold in promoting the formation of heat in the body — a phenomenon, as previously observed, directly opposed to physical laws, allow me to recall an experiment I made in the winter of 1891-2. The 9th December was a fairly clear day with a cold north wind, the temperature in the open air in the grounds of University College registering 36° P. My assistant Mr B. F. Davis, B.Sc, twenty-one years of age and in full enjoyment of robust health, kindly submitted to experiment. The first stage of the experiment was clearly to obtain the volume of air and CO3 expired within a given time in the comparatively warm, laboratory inside the College, with the temperature at 53° F. The air expired by Mr Davis while in the recumbent posture in a deck chair was collected in a bell-jar suspended over salt water, and subsequently LECTURE I 9 analysed for the determination of its CO3. We next adjourned into the College grounds, where, after walking for a quarter of an hour and then remaining for twenty minutes sitting in the cold open atmosphere, the air expired by Mr. Davis was again collected and subsequently analysed. It may be added that this gentleman showed a great power of resistance to cold ; while under experiment in the College grounds he wore a light jacket and no hat, yet at a temperature of 36° he did not feel cold. The following was the result of this experiment : Volume of air expired per minute indoors at 53° F. reduced to the freezing point and seaside pressure 3'455 litres Volume of air expired out of doors at 36° P 4858 „ Increase in the cold . . . . . . 1'403 „ CO3 expired, 53° F 217 cub. cents. COo eipii-ed, 36° F 284 Increase in the cold 67 „ Equal to an increase of 309 per cent. CO, for a difference of from 53° to 36°. In another similar experiment on the same person made on 2nd January, 1893, the external air was colder than on the former occasion, the temperature being 26° F. On this occasion, while 4"0 litres of air were expired per minute in my laboratory, after resting in the outside air for about fifteen minutes in the deck chair, the volume of air expired per minute had risen to 4*530 litres ; after remaining for ten minutes longer, or altogether twenty-five minutes perfectly quiet in the chair, the volume of air had increased to 4"726 litres per minute, and a few minutes later to 5'306 litres, showing the progressive resistance of the body towards the gradual^ intensified action of the cold. Allow me to recall the universal habit of taking a cold bath in the morning when getting out of bed ; its object is clearly to excite the energy for the day's work, and the practice is undoubtedly beneficial so long as health and age do not interfere with the reaction, or with the phenomena giving rise to the increased formation of CO^. A time of life comes, however, when the cold bath is depressing rather than beneficial, and then the action of cold water may be limited to a small surface of the body, such as the head or face only. Merely plunging 2 10 EBSPIRATION OF MAN the hands in cold water is sufficient to produce increased combus- tion in the body, as shown by the following experiment. Having determined the volume of air and CO^ given out within a certain time while remaining perfectly quiet in an arm-chair, I had a bucket of cold water at a temperature of 52° .F. brought within reach of my left hand, which was then immersed in it. After a short time the air I expired was again collected and the CO3 determined ; the volume expired per minute was found to have increased from 4*224 litres to 4"795 litres, and the 00^ produced had also increased from 181*6 c.c. to 204'7 c.c. per minute. Thus it is that the immersion of the hand, only, in cold water, is sufficient to produce a distinct increase of COg and therefore of energy. If cold applied in a certain degree can be looked upon as promoting metabolism or vital energy, when excessive, or continued too long, its action is reversed — it will no longer be productive of increased heat, and we may conclude that the vibration of living matter instead of being promoted is weakened. This apparently means that while more inter-molecular oxygen is absorbed under the influence of a moderate degree of cold, less is taken in when the cold is excessive, and when it falls below a certain figm'e death must follow. Cold depresses the vital energy more powerfully the lighter the air, especially when applied to persons untrained to low barometric pressures, as training is unquestionably the main secret of resisting cold under these circumstances. It is hardly necessary for me to refer to fatal occm'rences in high mountains from the effects of cold, and perhaps I might recall the deeds of devotion of the monks of the Great St. Bernard, and the number of Italian labourers they rescue every winter from certain death. I am able to quote an illustration of the depressing action of cold on myself and a young friend when, in July, 1880, we spent three days on the summit of the Col du Geant, on the Mont Blanc range, at 11,000 feet above the sea level, with the object of inquiring into the state of our respiration at that altitude. In the valley, at LECTURE I 11 Courmayeur, before ascending the pass the mean temperature of the air was 71° F., and the barometer stood at 29'948 in.; a number of experiments were made at that station by collecting in an india- rubber bag the air we expired, and determining the OO3 it contained. Then the mountain was ascended, and for three days we remained at a temperature of about 43° in the daytime and much lower at night, barometer 20"09 inches. Instead of producing more carbonic acid as might have been expected to make up for a fall of temperature of about 30° F., we both expired less — by 12 per cent, in my case, and 16 per cent, in that of my young companion. The vitality for each of us had clearly been reduced at the time ; we always felt cold, and our appetite, which was very good at Courmayeur just before ascend- ing, fell off to a remarkable extent during our stay on the pass. Thus it was that the cold, together with diminished atmospheric pressure, had failed to excite our vitality, and, indeed, had brought about the opposite effect ; had we both been in better training this probably would not have happened. Not only may the intensity of the cold produce a depressing effect, but long exposure to cold is liable to act in a similar manner. I have looked into a number of narratives of Arctic explorations in the hope of finding information on this subject, but Arctic explorers only make passing allusions to ill-health. According to Dr Kane's interesting account, great suffering was endured the second winter spent in the Arctic regions, scurvy enfeebled many or nearly all the members of the expedition : at the same time it was quite clear Dr Kane's equipment was very defective ; his ship was thoroughly unpre- pared for two winters, and therefore, in this case, it is difficult to determine the influence of continued severe cold on the health of the expedition. Dr Nansen, in his book on ' Eskimo Life,' gives but scanty infor- mation of the state of health of those inhabitants of the Arctic regions. Their sanitary conditions are altogether bad, they inhabit hot and steamy dwellings, their food is often scarce and lacks variety, they marry in and in, and no wonder they should be a weak 12 RESPIRATION OF MAN race. They are very subject to phthisis, and Nansen observes that there are few places in the world where so large a proportion of the population are attacked by it. As these pages were going through the press Dr Nansen returned home after spending three consecutive winters in the Arctic regions. The members of his expedition appear to have enjoyed good health throughout, and Nansen himself has, it seems, increased in weight. We might conclude that persons young, in strong health, and trained to Arctic winters, can withstand this long- continued excessive formation of heat without being the worse for it.* The morbid effects produced by long exposure to low tempera- tures are apparently, in general, of an inflammatory nature. Some years ago I had occasion to converse with the monks of the Great St Bernard, who live in a cold and damp climate at an altitude of 8116 feet, and suffer much in health on that account, though all of them are young men, and selected for their fitness to stand rough and cold weather ; many suffer after a year or two from rheumatism or gastric affections, and have to leave the spot. They are liable to bronchitis, but very few become consumptive. We need not, however, look so far to observe the baneful effects of prolonged cold. This last winter (1894-5), with its long-continued low tem- perature, has proved most fatal. In the week ending on the 9th March the 'mortality in London was 41*2 per 1000. I find it stated in the ' Times ' for 6th March, " The annual death-rate per 1000 in London from all causes, which had been 21'0, 29'3, and 34'0 in the preceding three weeks, further rose last week to 38"5. During the four weeks ending on Saturday last, March 2nd, the death-rate averaged 307 per 1000, being 9"5 per 1000 above the mean rate for the corresponding periods of the years 1885 — 1894." In the * This book was on the eve of publication -when Dr Nansen read the account of his Arctic voyage before the Royal Geographical Society, on the 8th February, 1897. In this commvinication he stated that in the winter he and his companion spent away from his ship, having erected a hut, they both slept twenty hours out of the twenty-four. This is certainly a solution to the question ; the excessive genei-ation of carbonic acid to resist cold produced a reaction in the form of drowsiness, and in the explorer's long sleep, when com- paratively little heat was produced, the body recovered from the excessive drain due to the over-formation of CO; during physical activity. LECTURE I 13 course of the four weeks ending^ March the 2rid the mininiurQ temperature of the air fell to 9° under a screen in Wimbledon Park, and the readings were much lower with free exposure to radiation. Of course it is impossible to say how far the increased mortality resulted from the long-continued action of cold on healthy people, but the cold certainly produced a decidedly lowering effect on health. As stated at the beginning of this lecture, the physical 'effects of cold and its action on the vitality of animals has received much attention lately from the physicist, Raoul Pictet. In his experi- ments the temperature of the vessel in which the animals were placed was gradually lowered from 98-6° F. to —351° F. He concludes that warm-blooded animals resist for a considerable time the excessive action of cold ; but when their power is on the wane, death takes place in a few minutes, while the heat in the central portions of the body remains nearly constant to the end of this struggle for life. Fishes, Batrachians, and Ophidians resist the effect of freezing so long as the temperature does not fall below 5° F. for fishes, while Batrachians and Ophidians can bear still lower temperatures. It is to be regretted that the author of these experiments does not state the length of time the animals were exposed to such extreme degrees of cold, as time must be an important factor in an inquiry of this kind. The effect of cold on fishes is also illustrated in the following singular occurrence recorded in the 'Pall Mall Gazette' for the 23rd of Marcb, 1891, the truth of which there can be no reason to doubt, " In the early part of the month of July a boy was seriously ill in one of the boarding-houses at Godalming. Ice bags had to be applied to his head, the ice being procured from an ice-house, which had been filled in the previous December from a pond in the neighbourhood. In pouring ofi" the water from one of the ice bags after it had been used, a small fish was seen swimming merrily about. . . . Accord- ing to the master of the house, the fish was very small and so transparent that a large portion of its internal organism was clearly 14 RESPIRATION OF MAN visible." The article concluded as follows : — " At all events we have here a well authenticated case of a fish surviving its enclosure in ice for a period of from six to seven months." I have had an opportunity of observing gold fish which had been caught in the ice this last winter (1895) ; one fish swimming about in the morning was found in a solid block of ice the following night. The ice was left to thaw in a room during the night, but the fish was found dead next morning. On another occasion there remained a small quantity of water round the fish, so that it was not absolutely embedded in ice ; when examined it appeared quite dead ; there was no motion whatever of the gills, but on placing it in cold water it gradually came to life, and recovered perfectly. On another similar occasion the fisli showed signs of life but failed to recover. Two gold fish had been left in the fountain while the water it contained froze gradually into a solid mass of ice. When the ice was entirely melted early in March the two fish, and a frog which had tenanted the fountain unknown to me, were all three found dead floating on the water. The occurrence at Grodalming is remarkable ; in that case the fish probably fell from the ice on being carted to the ice- house, and found itself in a small pool of water; here the animal had lived for some months. The observation I had an opportunity of making shows that at the freezing temperature of the air fishes can remain alive though apparently lifeless, on condition of their not being absolutely embedded in ice ; but certainly gold fish frozen up in water in a winter frost will not survive if embedded in ice for some hours. Following up the contention expressed in this first address, these experiments show that the maintenance of the molecular vibration or motion of life requires very little heat in cold-blooded animals ; if, after cold has been applied, the return of life movements be disturbed by too great an accession of heat, the vibration is immediately arrested ; thus a careful handling is required to restore life in its full activity. At the beginning of this lecture I remarked, as a proposition to be proved, that it is not the oxygen that brings about the tissue change LECTURE I 15 by offering itself to the tissue, but the tissues, undergoing change, make a call, a demand, on the atmospheric oxygen ; thus the circula- tion will be regulated by the vitality of tissues, and not the vitality of tissues by the circulation. As evidence in favour of this view, the influence of cold on vitality was brought under consideration, and it was ^hown that cold began by increasing vitality, and then, when applied beyond a certain degree and limit of time, it had a tendency to produce an opposite effect. Of course there is nothing new in these statements, but my contention made it necessary for me to go into the present details. "We now have to consider a state of life, which to my mind bears some relation to the increased production of carbonic acid in the body from an accession of cold, I mean muscular exercise. The succession of phenomena in muscular exercise are as follows : — First, volition towards exercise produces an increased volume of air breathed, which occurs immediately before contraction, or simul- taneously with its commencement ; at the same time, as will be shown in my third lecture, a certain amount of oxygen is absorbed in the motor centres of the brain corresponding to tbat muscular exercise. An excess of carbonic acid is expired, together with the beginning of the exercise, which at first originates from the oxygen contained within the muscles, and in proportion as this is used up, the oxygen required for the work done is taken into the muscles from the air breathed, so that the muscles continue charging themselves afresh with oxygen. The kind of exercise adopted in my experiments was simply walking or raising the feet sixty-six or sixty-seven times per minute to a height of about four inches, in keeping with the striking of a metronome. I made a number of experiments showing that when the air ex- pired is collected at the very beginning of the exercise, the oxygen consumed is taken in a large proportion from the oxygen pre-existing in the muscular tisssue. With that object in view, the stepping exer- cise was commenced, and the air expired at the same time was collected for analysis during three minutes. In other experiments the air 16 RESPIRATION OF MAN expired was obtained and analysed after the exercise bad lasted suc- cessively three minutes, nine minutes, twelve minutes, and fifteen minutes. The oxygen consumed in every one of these experiments was obtained by analysis, and the figures when compared with each other show clearly that atmospheric air is far from supplying the required amount of oxygen at the very beginning of the exercise. The results obtained were as follows : — Duration of exercise be- "\ fore collecting the air J-From to 3 min. . 6 min. . 9 min. . 12 min. . 15 min. expired* . . .J O. consumed or O. taken Y from the air breathed I „,„ _„. „„. -„„ bitc . „ }- ... 719 c.c. . 770 c.c. . 834 c.c. . 799 c.c. . 775 c.c. and COj expired per minute . . . -" It will be seen by a glance at these figures, that during the first three minutes of the exercise under the heading " to 3 min.'' the oxygen absorbed from the air, together with the carbonic acid expired, was only 719 c.c. per minute, although the heat required was the same as after 6 minutes or 9 minutes, when much more oxygen was absorbed from the air ; hence the muscles drew upon their molecular oxygen to a marked extent. Those experiments were made on the gentleman who assisted me at the time; other series of a similar kind were undertaken on myself and another assistant the following year with corresponding results. It cannot, therefore, be doubted that the oxygen stored up in the muscular tissue is used more or less towards muscular work at the very beginning of the contractions. The connection of exercise with respiration will be more fully inquired into in a future lecture ; in the meantime if, as I contend, the amount of carbonic acid emitted in breathing, or more correctly, the amount of oxygen consumed by the body, is a measure of the vital energy of tissue, then exercise, especially with persons who produce COg readily, will be a means of keeping up and exciting the life of tissues, and thereby giving them additional power to resist any abnormal change constituting disease. The overdoing of exercise is baneful, in * The experiment made three minutes after exercise was begun was accidentally lost. LECTURE I 17 a great measure because of the difficulty the body will experience in obtaining from the air a sufficient amount of oxygen for the work, but perhaps as much, also, on account of the trouble required to rid the blood of the carbonic acid formed, which accumulates in the circulation. Muscular exercise is attended, of course, with the production of a considerable amount of heat, but I might ask, is there invariably an increase of temperature to be observed with the thermometer ? This leads us to consider the question of the temperature of the body in the act of climbing or ascending — a subject which comes to the front fi'om time to time, and was last brought before us by Dr Hermann Weber in 1893 in an interesting paper published in the ' Lancet.' But before entering upon this subject, allow me to offer a few remarks on the methods in use for testing the temperature of the body. In 1888 I had occasion to enter into a controversy with a Swiss gentleman, Dr Vernet, who published results he had obtained from taking his temperature while engaged in mountaineering. Dr Vernet is gifted in a high degree with the power of resisting cold, and feels perfectly comfortable and warm in light clothing at a considerable altitude above the snow line. He subjected himself to a series of experiments on the influence of cUmbing on temperature, using a clinical thermometer introduced into the rectum. This he declared was the only correct method for such kinds of observations. Being in the habit of taking temperatures under the tongue — a method in general use clinically, I was anxious to ascertain the accuracy of Dr Vernet's assertion, and in order to attain this object we arranged to ascend together one of the highest points of the Jura Mountains, called the Dole, offering a climb of between three and four thousand feet. On nearing the summit, and while walking, we took our rectal temperatures, and found that with both of us there was a distinct rise beyond the normal temperature. This experiment was not, in my opinion, conclusive, as in the act of climbiTig, the blood, from the effect of gravity, must accumulate in the haemorrhoidal vessels, leading to a state of congestion and thus to a 3 IS RESPIRATION OF MAN rise of temperature. The question, however, could only be settled experimentally, which was done in the following way : — On getting up from my bed in the morning, I took a few steps about the room and then determined my temperature, rectal and sublingual, at the same time ; the rectal gave 98"0° F. and the sublingual 97*9° F., a difference of 0-1° F., or practically nil. On the 1st August, in bed, just before getting up : Rectal temperature . . . . . 984° F. Sublingual temperature .... 97-9° F. DiiFerence. . . . 0-5° F. on the 2nd August, in bed : Rectal 982° F. Sublingual 97-7° F. Difference .... 0-5° F. 3rd August, in bed : Rectal 98-2° F. Sublingual 97-9° F. Difference. ... 0-3° F. 4th August, in bed : Rectal 98-2° F. Sublingual 97-9° F. Difference. . . . 0-3° F. consequently there was the very small mean increase of 0"3° F. observed in bed in favour of the rectal temperature. The following experiments show clearly that exercise, even mode- rate, produces an increase of the rectal temperature, decidedly in excess of that observed under the tongue. On the 1st August, 1885, my temperature, while reclining on a couch after exercise and a good deal, of excitement, was — Rectal 99-7° F. Sublingual 98-4° F. Difference. . . . 1-3° F. LECTURE I 19 1st October, on walking about my room, at a slow regular pace : Rectal 99-7° F. Sublingual 98-8° P. Difference. . . . 09° P. this last experiment repeated : Eectal 99-5° P. Sublingual 987° P. Difference . . . 0-8° P. Those three experiments gave a mean difference of 1'0° F. excess for the rectal temperature, and in one case the excess rose to l'B° F. ; this increase was merely from moderate walking exercise in the room, and certainly appeared to be of a local character. What would have been the increase from the same cause on ascending a steep slope with a very active circulation, and the influence of gravity exerted to a very much greater extent. From these experiments it follows that although there may be a very slight increase of the rectal over the sublingual temperature when taken under circumstances afPecting equally the temperature in both regions, I mean while lying down ; still the moment a person is standing and walking about, the rectal tempera- ture is increased notably beyond the sublingual. No doubt, in very cold air, the blood reaching the sublingual region from the lungs sooner than the rectum, a slight relative cooling under the tongue may be produced. There remains the possibility of the cold in high altitudes acting through the skin and tissues of the submaxillary region and thus reaching the under surface of the tongue. It occurred to me that a few experiments to clear up that point might be of use, and this was done by applying pieces of ice under the chin, while the bulb of the thermometer was maintained under the tongue. The ther- mometer was bent and the reading made by reflection in a looking- glass held at the back of a magnifier ; by this means it was easy to follow the oscillations of the mercury. The results of these observa- tions are given in the following chart. 20 RESPIEATION OF MAN It will be seen from this chart that on two occasions there was a perceptible rise in the temperature the moment the ice was applied, a phenomenon also observed by Eaoul Pictet in his experiments on the application of cold to animals. A slight fall quickly followed ; in the Experiment N? ^ o S ? 98°, 9 98°, 7 98°. 5 98°, 3 NorrmJ, tempercUure SuhUngucU 981^ Experiment N°2. a 2 W h w r- ^ K S % 5 98°, 5 •— 98°. 3 ^y— — • 98°. 1 'V ^ 97°, 9 > r 97°, 7 ^•^ Expepiment N?3. 98". 98°, 98°, 98°, 98°. 38°, 98°, in in 3 (\1 in o ? 8 ^•^ 7 — — ^ N, 6 V 5 4 ^ V ^ 3 V ^^ 2 ^^ Normal te-mperatiu-e SiLhlinjpuaL 98- 7 first case the maximum fall was by 0*2° F., in the second by 0'6°, in the third by 0'5°, in the course of from thirty to forty-eight minutes ; therefore the application of ice to the submaxillary region affected but very slightly the sublingual temperature. The temperature of the body while in the act of ascending has been for a long time past subject to discussion. In 1865 Professor LECTURE I 21 Marc Dufour in his inaugural dissertation to the medical faculty of Zurich stated from experiments made on himself, that in the act of ascending, the thermometer falls rapidly by 0'4° F., and he quotes another observer. Professor Tick, who, while ascending a steep slope with the thermometer under his tongue, observed a fall of temperature of from -1° to -2° C. (0-2° to 0'4° F.) Breschet and Bequerel found with a thermo-electric pile that after five mimites work, the temperature of the body rose by about 1° C. (2° F.) According to the experiments of C. Speck, in 1863, during excessive muscular work the temperature of the body increased slightly. In 1869 I began giving attention to this subject in the Swiss Alps, using a bent thermometer by Casella, which was divided into fifth of degrees Centigrade and reading the instrument by redection in a small looking-glass held in front of me. I invariably observed, while experi- menting on myself, that the temperature fell in the act of ascending. In general, it was while ascending rapidly, when fasting and perspiring freely, that the cooling was most marked. These inquiries were followed closely by those of Professor Lortet, of Lyons, who obtained similar results by observing his own temperature while in the act of climbing, but, in addition, he appeared to find a connection between the elevation and the degree of cooling. Similar observations were made by Dr Clifford Allbutt, F.R.S. ; his results were opposed to those obtained by Professor Lortet and myself; the temperature rose while in the act of ascending ; there were, however, three exceptions to this rule — in one case his temperature fell from 98-4° to 97-4°. In 1872 and 1873 there appeared two important papers on this subject by Professor F. A. Forel, of Lausanne ; this well-known physicist observed that the muscular work of ascending raised the temperature of his body, and that the greater the exercise the higher was the temperature. In 1870 Mr Gay, of Strasburg, made a number of ascents of the Cathedral of that town, testing his temperature under the tongue, and invariably observed it to fall by 0*4° to 0'5° C. 22 KESPIRATION OF MAN Immediately after the ascent the temperature rose and reached its normal degree, going beyond it for a time. Professor Ray Lankester observed that in the Alps his temperature fell in climbing; his guide exhibited a similar phenomenon. He found his temperature lowered to 96° F. while ascending under a hot sun the grass slope at Bel Alp. Dr Vernet, whose name I have already had an opportunity of quoting, observed invariably an increased tempera- ture in the act of ascending. We therefore have a number of reliable observations apparently contradicting one another, by which we are to judge of the effect of climbing exercise on the temperature of the body. On looking care- fully into the matter, there is but one way of accounting for these observations, which is to conclude that the influence of climbing on the temperature of the body varies with different people. Some persons in thorough training, young, perspiring but little, and pro- ducing as a rule a large amount of COg, or developing much heat under ordinary circumstances, will observe their temperature to rise in the act of ascending; others who generally produce less CO3, therefore developing less heat, will, while engaged in hard climbing, produce just the amount of heat they want towards the exercise, but under the cooling influence of perspiration, fasting, &c., their tem- perature will fall below the normal. LECTURE II 23 LECTURE II Mb President and G-entlemen, — Before entering on the subject proper of this lecture I must beg leave to glance at a few of the recent contributions to our knowledge of the phenomena of human respiration. In 1849 Regnault and Reiset,* from experiments on animals, observed that a marked volume of oxygen was taken in at the lungs which failed to reappear as carbonic acid in the expired air, and thej established a relation between tlie oxygen consumed and the carbonic acid produced. These experiments were repeated and confirmed in 1891 by Messrs. Chapman and Brubaker, of Philadelphia.f Dr Edward Smith, J in a paper published in 1859, divides foods into two classes, according to their action on respiration — the excito- respiratory, which increase the production of carbonic acid, and the non-excitants, which have a contrary effect. Two results are prominent in this paper: first, that fats, oils (cod-liver oil), and starch diminish the carbonic acid expired ; secondly, that although the ingestion of pure alcohol and rum act as respiratory excitants, still drinking brandy, whisky, and gin is attended with a diminution of the carbonic acid expired. The elaborate chamber constructed by Pettenkofer, of Munich, in 1863, and his important inquiries with Professor Voit,§ into the respiration of man, should be placed here on record. In 1871 C. Speck |1 published important papers on respiration. He observed that on returning to natural respiration after forced bi'eathing, much less air is expired for a short time than in ordinary * ' Annal de Chimie,' 1849. f ' Proc. of the Academy of Natural Sciences of Philadelphia,' Jan., 1891. + ' Phil. Trans.,' 1859. § ' Liebig Annal,' ii, 1863. II 'Schriften der Gesellschaft zur Beforderung der Gesamtnten Naturwissenscliaften zu Marburg,' 1871. 24 RESPIRATION OF MAN breathing in repose ; and also that the amount of carbonic acid expired as the after-effect of forced breathing falls considerably below the normal. The oxygen taken from the air is also momentarily reduced. In 1878 Paiil Bert's* remarkable book on 'The Effects of Baro- metric Pressure on Respiration ' was published. He observed that animals dying in closed vessels, and consequently in their own carbonic acid, exhibit precisely the same symptoms as if they had perished under diminished atmospheric pressure, from which he concludes that carbonic acid is absolutely innocuous, and that in such cases death is due to want of oxygen. In more recent years, Dr George v. Liebig, of Munich, f Messrs Jolyet, Bergonie, et Sigalas,| and MM. Hanriot et Richet,§ have contributed a number of important papei"s on respiration. Dr G. L. De Saint Martin || is the author of an elaborate work on respiration (1893), recording his researches on the inhalation of oxygen gas, on certain phenomena of anaesthesia, and' on the toxic effects of carbonic oxide. These last experiments have a special interest. He observes that the principal chemical agent towards the destruction of this poison when in the blood is the presence in the blood of an excess of oxygen ; and concludes that the inhalation of oxygen may be looked upon as opposed to poisoning with carbonic oxide — a view he considers as confirmed by medical experience. It should not be forgotten that in 1856, Claude Bernard observed that blood becomes bright red in contact with carbonic oxide, and can no longer assume the venous colour, — the globules are paralysed and useless towards the interchange of gases.^ These observations of 01. Bernard and De Saint Martin appear as paving the way towards the important experiments of Dr Haldane, of * ' De la pression atmospherique,' 1878. t ' Zeitsclirift flir Biologie,' Miinclien. + ' Oomptes Eendus,' 1887. § ' Annales de Ohiniie et de Physique,' 1891. II 'Bechei-clies experimentales sur la respiration.' ^ ' Lemons sur les effets des substances toxiques et medicamenteuses,' 1857. LECTURE ir 25 Oxford, published in 1895.* This gentleman, who has been engaged for some years with inquiries on the respiration of man and animals, has shown that while 0-221 per cent, of carbonic oxide in atmospheric air is fatal to mice in two hours, in an atmosphere of oxygen the pro- portion of carbonic oxide can be increased to 5 per cent, without danger ; and if the pressure of the oxygen be raised by one atmo- sphere, the two atmospheres of oxygen may[^be]mixed with an additional atmosphere of carbonic oxide without harming the animal. Amongst the chief conclusions from the present inquiry, the author observes that, " The disappearance of the poisonous action of carbonic oxide is due to the fact that at high oxygen tensions the animals can dispense entirely with the oxygen-carrying function of hsemoglobin." And, moreover, " the poisonous action of carbonic oxide is entirely due to its power of combiniug with the heemoglobin of the red corpuscles, and so putting them out of action as oxygen carriers." The phenomena of respiration, simple as they appear at first sight, lead on a closer inspection into details many in number and increasing in complexity the further the study is carried. Moreover, these phenomena are not precisely the same for everybody, and on that account my ex- pei'iments have been repeated on as many different persons as possible. The methods of investigation adopted by different authors are very various. Edward Smith inspired through one gas meter and expired through another; while C. Speck inhaled air under atmo- spheric pressure from a bell jar suspended over water, and collected the air he expired in a similar receiver, the change of direction in the respiratory current being effected by delicate valves. Dr G. V. Liebig, in his experiments, instead of directly measuring the volume of air inspired, obtained it by calculation from the nitrogen found in the air expired, assuming that nitrogen was neither absorbed in the body nor given out of it in the process of respiration. After the expenditure of much time and labour in the endeavour to obtain the most accurate results by means as simple as possible, and objecting to the use of gas meters on the ground that none could * ' Journal of Physiology,' 1895. 4 26 EESPIRATION OF MAN be found sufficiently delicate to allow of the passage of air to and from the lungs without oflfering any resistance, while valves and absorbing media were open to the same objection, I finally adopted the following method : * A cylindrical bell jar of sheet iron, holding about 40 litres, or 1-4 cubic foot of air, furnished with a scale divided into litres and fractions of a litre, was suspended in waterf over a pulley, working on friction wheels, and accurately balanced by a counterpoise. The instrument was constructed with much care by Messrs. W. Parkinson & Co., gas engineers. A small additional weight was added to the counterpoise, which gave a very slight ascending motion to the bell jar, and thus did away with the feeble effort necessary to raise it when under atmospheric pressure only. To the pulley was fixed a cycloid or lever carrying a weight, the cycloid being so constructed that the effective arm lengthened as the bell jar rose, this arrangement maintaining the receiver under atmospheric pressure at every position in its course. A thermo- meter and pressure gauge showed the temperature and tension of the air inside the receiver. The person under experiment inspired fresh air through the nose, and expired through the mouth into a tube connected with the bell jar — a process which, with a little practice, soon became quite natural, f By means of an uniformly rotating drum, moved by clockwork, and a horizontal style fixed to the top of one of the three bell jars employed, expiratory tracings were obtained on skeleton charts ; the abscissge engraved on the chart measured the number of litres expired, and the ordinates recorded the minutes through which the experiment was continued. The air collected in the bell jar was analysed for the determination of its carbonic acid, or carbonic acid and oxygen, the amount of the * See Plate following p. 26. t Salt water was used for some years, and then given up because of its destructive action in the bell jars. Plain water was found satisfactory where the COo was determined within an hour in the air expired. The tank was annular, and therefore exposed but a very small surface of water to the air in the bell jar. J See Methods of Investigation and Analytical Results, p. 84. B-ecoTchTuq Drxari' Elevation view of Bell -"jars and neconding dri. Scale of F^et. . Mi glQAiS CISj x^'ell-^arr. aTid reooirdin^ Ans-b-LLxrie-Tit seeri From abt Cycl^hd ide V- a :« ^j^lmdeT- for the detei-rmnation oi carbonic arid vVe£t.]~]e-WTniMn "photo - Hth. LECTURE II 27 former being determined bj Pettenkofer's method, and the oxygen by means of an eudiometer of a special construction. As already stated, the volume of air inspired can be determined by calculation from the volume of nitrogen expired, assuming that the nitrogen in the expired air represents exactly the nitrogen inhaled. To find out experimentally if this assumption was correct, a measured volume of air saturated with moisture was inhaled from one bell jar and exhaled into another, thus showing in a direct manner the volumes of air inspired and expired ; at the same time the volume of nitrogen in the expired air was obtained by analysis, and from it the volume of air inspired was calculated. The mean of ten experiments gave a volume of air inspired, as determined by direct observation, almost identical with that obtained by calculation from the volume of nitrogen in the expired air; thus showing conclusively that no appreciable amount of nitrogen is either absorbed or given out from the blood in the phenomenon of respiration, and also justifying the method employed.* * The following are the details of these experiments — Table I. Volumes of air observed. No. of experiment. l(self) . . 2 „ . . 3 „ . . 4 „ . . 5 (Assistant) 6 7(seH) . . 9 (Assistant) 10 Means Inspired. 33.944 c.c. 34,238 „ 33,686 „ 33,705 „ 33,996 „ 33.945 ., 33,226 „ 34,553 „ 33,194 „ 32,912 „ 33,740 c.c. Expired. 33,654 c.c. 33,833 „ 33,445 „ 33,585 „ 33,840 „ 33,774 „ 32,886 „ 34,366 „ 32,926 „ 32,585 „ 33,489 c.c. Volumes of air inspired, obtained by calculation from the volume of nitrogen found in the air expired. . 34,000 c.c. . 33,972 „ . 33,783 „ . 33,843 „ . 34,262 „ . 33,953 „ . 33,106 „ . 34,658 „ . 33,101 „ . 32,764 „ 33,743 c.c. In this table the first column of figures, on the left, shows the volumes of air inspired, as measured in the bell -jar from which the air was breathed; the second column shows the corresponding volumes of air expired, as determined in the second receiver. The third column gives the volumes of air inspired, calculated from the assumption that the whole of the nitrogen inhaled is also exhaled. It will be observed that the mean of the volumes in the third column is all but exactly the same as the mean of the volumes in the first column, the difference being only by 3 c.c. ; hence the obvious conclusion that nitrogen takes no appreciable part in the interchange of the pulmonary gases. 28 EBSPIRATION OF MAN If a person, while resting iu a recumbent posture in an arm-chair and breathing quite naturally, should measure the volume of air he expires, this volume will be found invariably smaller than the corre- sponding volume of air inspired. A certain volume of oxygen has remained in the body ; what has become of it ? Formerly this absorbed oxygen was looked upon by some authors as combining with hydrogen to form water, but of this there is no proof. Its amount is subject to great variations even in the same person, while these oscilla- tions appear greater in young people with active tissue change than in elderly persons with a slow and regular metabolism ; moreover, young people appear to absorb somewhat more oxygen in a given time than persons of mature age. The period of the maximum absorption of oxygen is, undoubtedly, within the first hour after a midday meal. This is a time when the carbonic acid expired is low ; but there is a demand in the body for the forthcoming increased assimilation and tissue change under the influence of digestion, and from some phenomenon which cannot be explained oxygen is taken up by tissues and stored up. From the following table, giving results of experiments on myself, it will be seen that for a person aged about 63 the mean volume of oxygen he absorbed per minute while fasting, was pi-actically the same as under the influence of food, being 35'3 c.cm. fasting and 34"6 c.cm. while under the influence of food. Oxygen Absoebed pee Minute (Atjthoe tjndee Experiment). Fasting (just before luncheon) — Teai' 1891 (6 experiments), from 25'7 c.cm. to 42'8 c.cm. ; mean, 35"3 c.cm. Mean time of 21 hours after full meal — Tear 1891 (6 experiments), from 21'3 c.cm. to 36'7 c.cm. ; mean, 30'2 c.cm. „ 1892 (10 „ ), „ 20-4 „ „ 46-1 „ „ 36-7 „ „ 1894 (21 „ ), „ 27-7 „ „ 45-0 „ „ 37-0 „ In the case of three young men who submitted to experiment — all of them from twenty-one to twenty-three years of age, strong, and in good health — the following results were obtained. LECTURE II 29 Oxygen Absorbed per Minute. Fasting. Nearly 2 liours after luiicli. Iiicriase after lunch. No. 1 (6 experiments), SoS c.cm. . . (6 experiments), 37'5 c.cm. 126 per cent. No. 2 (3 „ ), 34-1 „ . . (7 „ ), 50-0 „ 46-6 No. 3 (6 „ ), 34-4. „ . . (12 „ ), 40-5 „ 174 It will be seen from this table tbat with young men distinctly more oxygen was absorbed about two hours after a full meal than Avhen fasting; hence it appears that in young people there is a decided increase of the oxygen absorbed at a time when the carbonic acid produced is not far from its maximum. This is not, however, the occasion of the maximum absorption of oxygen which, aa stated above, occurs in the course of the first hour after a full midday meal; this is shown by the following figures for that period. The Author (4 experiments), 47'9 c.cm. to 583 c.cm. General mean : fasting and under the influence of food . 34'0 c.cm. Mr Floris (7 experiments), 564 c.cm. to 81"6 c.cm. General mean : fasting and under the influence of food . . 374 „ The oxygen absorbed added to the carbonic acid produced will indicate the total amount of oxygen taken from the atmosphere, or " oxygen consumed." The relation between the oxygen con- sumed and the carbonic acid produced has been called by Regnault and Reiset the " respiratory ratio," and is expressed by the ratio ^ =. As the CO2 given out is absolutely independent oxygen consumed of the oxygen taken in at the same time, it follows that the value of this fraction varies considerably at all times of the day, but when calculated for the mean volumes of oxygen consumed and carbonic acid produced in the daytime in a state of rest, it appears to be nearly the same for different people. Thus the mean obtained by Messrs Jolyet, Bergonie, and Sigalas was 0'864 ; that obtained on myself was the same, 0'864; the corresponding figure as a mean of twenty-seven experiments was 0*862 for one of my assistants, and 0878 for another from twenty experiments. The subject, however, requires further in- vestigation on account of the number of circumstances controlling this ratio, and I have observed conditions which appear to alter it. 30 RESPIRATION OF MAN There is no direct connection between the CO2 produced and oxygen consumed, and consequently no meaning in the respiratory ratio unless given as the average for the whole day in the state of rest, and even this average is subject to exceptions. I am anxious to make this statement, for fear of being misunderstood. It is impossible to trace the history of the oxygen taken in the lungs by the blood-corpuscles. This oxygen is carried into the tissues and there detained and stored up according to their requirements. The great increase of oxygen taken in, and the low volume of carbonic acid expired, within an hour after a meal, certainly appear to show that on this occasion the tissues store up within themselves a considerable amount of oxygen. The reverse would take place from an immediate demand for heat by the body, as would be required from a sudden accession of cold, or in the passage from a state of rest to one of muscular exercise. It has been shown in the first lecture that the oxygen absorbed from the air in the very earliest stages of exercise was insufficient in quantity for such a pui-pose, and consequently the balance required was derived from the oxygen stored up in the body. A similar phenomenon must occur from a sudden accession of cold. The DlFl'EEENT FOEMS OF Respieation. On taking a general view of human respii-ation, it is found that this function may assume four distinctly different forms, which include the endless varieties of breathing. The first is automatic breathing in a state of repose. The second, forced or laboured breathing while the body is in a state of rest. The third, breathing while under muscular exercise. The fourth, breathing while the body is in a perfect state of repose, with the mind actively at work towards the exercise of volition. I shall make no further remark on the first form, but pass on at once to forced respiration. 13 I,iti ^es. 1 mixLute . BREAtHING CHART. 2 minutes. Smimites. 4 xnmti tes. 31 UtM 31 30 y^ 30 29 /^ ?9 28 /^ 28 2^ y ?n ?,n J f.o /^ ?I0 » / ia a J 18 7 17 B A 1R 5 / 15 4 y 14 3 n. y^ 13 ?, y / m 11 y^ jJ n / y 10 / ^ 9 8 / J-^ 8 1 r y 7 6 ^ 6 5 /~* -'"'^ / ' 5 4 c y 4 3 ^ y a ^ 2 / ? = 1 ^ / 1 = B A = Lil re B. .... ' """* * '^'Sre*.'* ) AA. Normal, BC. Sneezing, CD. After Stage. ■WestiNcmnan Hth. I^itres, 1 irduute BREATHING CHAB.T. 2 minutes. Sedbuced' to half original. siz& 3 minutes. 4 minu teB. Litres, AA, Normal. BC. Sighing, CD. After Stage "WestjlTcwinsai Ti^ 8 BREATHING CHART. 2 miimleay Seduced- to half ari^viaZ siz&- a.T«iifwrf«« 4 Jninu teB. Litres, AA. Nopmal. BC. Yawning, CD.After Stage TVestjI^ewman itk. LECTURE II 33 jar will contain a smaller excess of carbonic acid over the normal proportion than the first, and the third smaller than the second, less and less carbonic acid being left in the blood as the experi- ment proceeds. Experiments on myself and my assistant show this view to be correct. The figures obtained on one occasion for carbonic acid emitted from the blood in excess of normal, when disposed on a chart yielded the following curve of a para- bolic form : 1 ST 2 ND 3RD C.C. COz.EXPIRED Per Min:from BLOOD, 1 1 1 *? "7 '3 1 1'6 c d s, N \ \ 1 S s s s. 1 h ! s c c ■s % •n ' **. ■ ?3 2 ■n C c ■^ — ^ _ Sneezing, sighing, and yawning, come under the head of forced breathino-. These forms of respiration are shown in the accompany- ing charts. Sneezing. — There was a difiiculty in exciting sneezing when wanted; but at last a fit of three successive sneezings was obtained, inspiring through nose and expiring through mouth. The pause after sneezing was very distinct, followed by a very slight increase of air breathed quickly subsiding into normal. Sighing and yawning gave much the same kind of record on the chart. The third form of breathing is under muscular exercise. In both 5 34 RESPIRATION OF MAN its physical and chemical aspects it differs greatly from the first and second form. The moment muscular exercise of any kind is taken, the volume of tidal air breathed in a given time is increased ; ttis phenomenon is absolutely automatic and unattended with fatigue. In my experiments tbe exercise taken consisted of stepping sixty-six or sixty-seven times per minute, the heels being raised to a height of about four inches. On these occasions the direction of the tracing on the chart was a fairly straight diagonal, with a much steeper rise than in ordinary breathing in repose. After the exercise had lasted for one or two minutes, the person under experiment assumed the recumbent posture in the arm-chair, breathing perfectly automatically ; the tracing on the chart was now observed to continue in the same direc- tion, for a length of time in a great measure proportional to that during which the exercise had been taken, then the inclination of the tracing became less and less steep till it gradually returned parallel to the normal. The tracing therefore exhibited no pause, as occurred in forced respiration.* Forced breathing, immediately following exercise, by removing the CO3 in excess in the blood, shortens the period of breathlessness on resuming the state of repose, and it is possible to regulate forced breathing in such a way that after two or three gasps normal respiration follows immediately. These remarks have a practical bearing ; they show that a person much out of breath from muscular exercise, on assuming the state of repose, will experience immediate relief from a few deep gasps, and also, that a long breath now and then with a short rest, in the course of protracted exercise, will be of help to respiration. Let us now inquire into the different stages of respiration under exercise. First of all more oxygen is wanted from the air for the heat required for the muscular work, hence a larger volume of air is breathed ; at the same time an increased amount of carbonic acid is expired, but this emission of carbonic acid cannot take place at a speed proportional to the rate of its production, and it therefore accumulates * A tracing for forced breathing has been introduced in the accompanying chart, in order to show the contrast with that of breathing under exercise. BREATHING CHART. 2 nriniite*. Be^lJZcejiL to ItcLhF origuunL sixe^. 3 minute g. 4 minu lea. 'Litr0B» A.A.lSTormal. B.C. Forced Toreathing for one TaxrruLte . C.D.After StM,ge. E .F. Exercis e , (stepping 6 6 time s p er min-ute ) . F. G . After S tag e . West Ne-wmaia litk . I^itres, O BREATHING CHART. 1 minute Redwyed- to hxilF original, size,. Liirea, AA. Normal. BC. Reading alonxd, CD. After Stage ■Wesi.Nevimaiilitli. 11 res, 1 minute . BREATHll 2 mil ?P CHART. uutes, Seduceii to 'haif ariglnat sixe-. SmiTiiitoa, "r\ 4 minutes. 1 -"-^ latrea 31 10 ■/ 30 » y 2» B y ?,f\ !7 / ""^ m A y ?(\ (5 y" 715 !4 / ?!4 !» / ?,H !2 / r ?,? 21 / ^1 !0 ?0 fl / 10 8 / A 18 7 /^ 17 6 / 1(> fi cy 15 14 / 14 IR J 1» 12 / / 1? 11 / r^ n in / j-r^ 10 8 1 y^ 9 8 f / A 7 I r^ 7 6 1 rJ^ 8 S 1 r^ •i 4 / 3 y 3 - 2 r^ ? = 1 / t : /a n : Lil res. . •■ . -. ... „_, " ' '" " * ^itii-A AA- Normal . B C. Screammg (I0.2]itres air expired) CD.Afcer Stage charaoteristic o£-work dene . ■Weat.Scvroiimiiai. 12 Iiitres, 1 minute BREATHING CHART, a tninutea. JUtre Rectwx£bto half orU/irval, jira 30 29 D 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 A, z z c, 11 10 AA, Normal. B C. Sereaming (12.3 litres ~^—Lz 4., 'i^-'i air expired) CD. After Stage, characteristic o£ forced "breathing. "W"est;Nev»man itk iLl BREATHING CHAB.T. 2 minutes. BedMCaoL t> ImlF ariginoL svz€,. 'Litres^ AA. NoTOial. BC. La-u-ghing, CD.AFter Stage 10 BREATHING CHART. 2 miimteSi EeJxuxdi to half oric/uwZ/ size.. '" " 31 litre a, AA. Normal. BC. After Stage of Smging, sitting. Characteristic of forced loreatli.irLg. ED. After Stage of Singing, standing. Tlie dotted, line is approximate for Singing Standing . "West, Ke^oman litii- Imi] auief BREATHII 2iiu] TO CHART. autes. 3noi] mitea. 4 xninuteB. 11 Idtrefl 31 to 30 *9 r\ 89 m j-j 38 ?t^ y 27 m y^ 26 P'.S y^ 2fi 24 f ^ fA 28 /^ 23 22 f 22 21 f 21 20 / 20 l» f A Ifl R s / 18 n f 17 Ifi J / 1(> Ift cy y lA M / r ^ H 1» / _// 18 i2 / ^ 12 11 / y' 1] 10 / / ^ 10 8 ^ y / y^ n 8 / /^ 8 T / V^^ 7 6 / /-^ 6 5 4i 5 / r ■ 4 / J'^^ 3 1 ^ 2 // 9 ' 1 // i '■= B y^ j ^- rrrr ^ Lit pei» , — ^^_^ AA. Normal. BC. SingiTig sitting. CD, Characteristic of breathi: After Stage. ng under exercise. Wast .Wffmmm litW. LBCTUEE II 35 in the blood. On arresting the exercise and assuming the state of repose, the excess carbonic acid is given out, and with that object the lungs have to be freely ventilated ; hence the state of breathlessness or dyspnoea after such exercise as running or walking. Chemical analysis shows that a large excess of carbonic acid is given out on sitting down after exercise, which carbonic acid must have been produced by the muscular work attending the exercise, as there can be no excess of combustion in a state of repose, for if there were, the temperature of the body would be raised, as the heat produced could not be disposed of in any other way but by radiation, a consideration which led to the following experiment. Two clinical thermometers were maintained under the tongue while stepping, and left there long enough to be certain of the sub- lingual temperature ; then one of the thermometers was removed, while at the same time the person under experiment assumed the state of repose. After about ten minutes the second thermometer was with- drawn, but its reading was no higher than the other; hence there is no excess of carbonic acid formed on resting after exercise, beyond a small quantity corresponding to the work done to rid the blood of tbe carbonic acid with which it is charged. The dyspnoea after exercise recalls an interesting experiment of Claude Bernard, who injected sulphuretted hydrogen into the circu- lation of a dog, and after each injection the animal drew a succession of deep breaths, thus getting rid of the gas injected, by an increased pulmonary ventilation. The sulphuretted hydrogen could be clearly detected by the odour of the animal's breath and its action on paper moistened with lead acetate. Reading, talking, singing, screaming, coughing, all belong to the form of respiration under exercise. Screaming shows from its tracings that in some cases it must be looked upon as breathing under exercise, in others as forced breathing. In the case of singing, the records on the chart point out that on singing in the sitting posture there may be either forced breathing, or breathing under muscular strain, attended with breathlessness, though this does not occur in the standing position, hence the im- 36 RESPIRATION OF MAN portance of singing standing. In reading, talking, and singing standing, tlie tracing of the "after stage" is at once parallel with the normal, showing that in these instances there is no breathlessness produced, and therefore no excess of carbonic acid retained in the blood. I shall beg to conclude this lecture with a few remarks on the exhalation of water from the lungs at different altitudes. The amount of this evaporation must be controlled by three different causes — the atmospheric temperature, humidity, and pressure. Given temperatures and humidity approximately equal, rising above the sea level will increase the evaporation in proportion to the fall of pressure. When on the Peak of Teneriffe in 1878 I selected four stations for experiment — one at the sea-side, another at an altitude of 7,090 feet, the next at 10,700 feet, and the fourth inside the shallow crater at the very summit of the peak, at an altitude of nearly 12,200 feet. The weather was very fine, and the atmospheric humidity exhibited no great variations at the different stations, except at the sea-side, where it was decidedly higher. The air expired was breathed through absorption tubes filled with calcium chloride, into a bag of known capacity, the time of breathing being also observed. The humidity of the atmosphere was determined with wet and dry bulb thermometers, and the weight of moisture contained in the volume of air inspired was subtracted from the total moisture expired; thus the weight of the water evaporated from the lungs was obtained. It was found that as the altitude increased, more and more water was evaporated from the lungs within a given time, although the amount of this increase was not quite proportional to the increase of altitude. At first I accounted for this phenomenon from the circum- stance that the loss of water from the blood at increasing altitudes left less and less to be evaporated; but on further consideration I am inclined to think that it is also a result of the fact that the volume of air breathed does not increase in relation to altitude, but in a proportion somewhat less. LECTURE III 37 LECTURE III Me PiiESiDiiNT AND Gentlemen, — III my last lecture tlie first three typical forms oi: breathing were considered ; let us now proceed to the fourth, which applies to respiration under the exertion of volition ; but before doing so allow me to recall a remarkable experiment of Professor A. Mosso of Turin. This gentleman constructed an instrument he called " ergograph," on which his hand was fixed with the jj'i/;/;. turned upwards, while his fingers, the middle one excepted, were also under control. "With this finger he worked a weight up and down, the movements being recorded graphically, until the digital muscles con- cerned in the labour were completely exhausted ; at this stage the muscular contraction was carried on by means of electrical excitation applied to the median nerve, and he found that if, after a short period, the excitation was discontinued, the finger was able still to maintain its work, showing that the muscles had not ceased contracting from actual fatigue, but from exhaustion of tlie will or brain-power which had been exercised to move them. There is an intei'esting borderland between psychology and physio- logy which is narrowing daily. The discovery of the electrical excita- bility of the brain by Fritsch and Hitzig, and of the motor centres by Ferrier and Yeo, followed by Horsley and Schiifer, has opened altogether a new field of research, and brought the mental and physical functions nearer to each other. A¥e do not know much of the physical effects exercised on the body by the perception of our senses. Moleschott, as far back as 1855, showed that fi'om one-tenth to one-fourth more carbonic acid was exhaled by frogs under the influence of light than when in tlie dark, and also that this increase varied directly as the intensity of the light, which acted through the eyes and skin. It occurred to me that if light exercises a distinct physical action on the living body, perhaps sound would produce a similar effect ; but even a fairly loud sound, such as that produced 38 RESPIRATION OF MAN by the beating of a gong close by, gave no positive result, the car- bonic acid emitted, under the influence of the sound being sometimes a little more and sometimes a little less than normal, and the same could be said of the oxygen absoi'bed. There was, however, a slight excess of air breathed (expired) while the noise was continued, which varied from 0'036 litre to 0'733 litre per minute in eleven experiments ; and this slight excess was balanced by a corresponding diminution of the volume of air exhaled during the first five or six minutes after the sound had ceased. The perceptions of our senses are certainly independent of our will, still the sight and hearing may not be entirely unconnected with voli- tion ; or it would, perhaps, be more correct to say that the impressions of our senses such as sight and sound may pass unnoticed. Take the case of a person lost in a brown study ; he does not see objects though with eyes wide open, nor will he hear a sudden noise. By submitting our senses to the exercise of volition or attention, we train them and improve their perception. Thus we train the sight to the better appreciation of the beauties of nature. Those thrilling descriptions of Alpine scenery, by Conway, Mummery, and Whymper, must be the outcome of training through the sight to the thorough enjoyment of mountain views. The rapture into which Sarasate and Joachim throw their hearers requires a certain training of the audition. A. Mosso has shown that the cerebral act towards muscular contraction is attended with fatigue. I need hardly remind you of the fatigue experienced in listening to good music ; two hours thus employed will, as a rule, be. amply sufficient, and it often happens that in less time the attention begins to flag and the impression to subside. Operatic music may be listened to much longer, for the apparent reason that in an opera the exercise of volition or attention is dis- tributed between two brain centres — those of hearing and of sight — instead of being concentrated on a single one, and is on that account less exposed to fatigue. We now come to the influence of volition on muscular movements. There are instinctive muscular movements in which volition is not 27 Litres, ImiT mte. BREATHIWG CHART. 2 minutes, 3 mi] IhdxLCAd. to half origtnaZ six^e-. outes. 4 minutes. 31 Uty^t 31 ao ^ 30 20 ?,fl 2R y" 23 2T y^ fn 2ft 2« 8fi 2!> 7A 714 2ft 23 %% / ?!2 1.\ /\ 31 20 D 20 IS) /^ y^ 1» IR XT' ^^ j^ 18 n i' -^ y^ 17 1 and give rise in the after- stage to a pause very like that which follows forced breathing ; but there is this difference with forced breathing, that when the will is applied say to the act of locomotioiij the increased pulmonary ventilation is absolutely automatic, while forced breaithing is the direct effect of volition applied towards the forcible expansion of the chest. Without wishing to enter at present into an explanation of the apncea in the foregoing experiments, the respiratory pause or apnoea is generally admitted to be the result of an increased absorption of oxygen ; and this oxygen, being used for the requirements of the body, would lessen for a few seconds the call for pulmonary ventilation. This idea* suggested that perhaps such an accumulation of oxygen in the body might be employed by the muscles for a temporary increase of power ; Dr Vaughan Harley, in a paper published in 1894 ('Journal of Physiology') on " The Value of Sugar and the Effect of Smoking on Muscular Work," remarks that, if he thought about the exercise to which he was going to apply his lingers, the maximum power was obtained at the very outset. The following experiment was made. While sitting in an arm-chair a weight of 10 lbs. was alter- nately raised and lowered with the hand in keeping with the striking of a metronome, and to my surprise it was observed that after a succession of deep inspirations the weight could be raised a much greater number of times than after normal breathing ; the increase of power was such that the weight could be lifted to the same height before exhaustion perhaps twice as often after forced breathing as after natural respira- tion. For a time this effect of forced breathing was unaccountable, as the excess of carbonic acid formed by the increased muscular work was infinitely greater than could be accounted for from any excess of oxygen absorbed in the body in the forced-breathing stage. * The apncBa in tliese expeiiments was subsequently found to be due to a cause inde- pendent of the absorption of oxygen. LBOTURE III 41 But perhaps in forced breathing there was really an excess of oxygen absorbed, which was taken up by the brain centres of forced breathing, and gave " volition " the power of doing so much additional muscular work through increased respiration. This view was subsequently investigated by experimental methods. Allow me to quote the experiments which show to what extent muscular power may be increased by the preliminary exercise of forced breathing. It might be added that, in order to succeed with these experiments, the attention should apparently be given to the act. It failed once or twice when first tried, though successful on every other occasion with that same person. Number of times Person under experiment. Autbor , Weight lifted, lbs. 8 Number of times Time weight lifted, of forced normal. breathing. min. . 24 . . 2 . weight lifted after forced breathing. . 65 . Ratio of increase. 2-71 ,, 8 . 26 . . 2 . . 50 . 1-92 J' 8 . 26 . . 1 . . 34 . 131 ,, 10 . 21 . . 2 . . 36 . 1-71 Assistant 8 . 30 . . 2 . . 32 . same. )) 8 . 33 . . 2 . . 49 . 1-47 rs 8 . 33 . . 2 . . 41 . 1-26 J, 8 . 39 . . 2 . . 63 . 1-62 )) 10 . 41 . . 2 . . 69 . 1-68 It is well known to what extent muscles become accustomed to work, and can develop more and more strength from mere training. This is seen in the figures given later on, but it is important to observe that the present remark does not apply to the above experi- ments, when the increased work was clearly due to increased power from a temporary cause. This point was set at rest by a very simple experiment. Two consecutive series of liftings were made without the intervention of any forced breathing. The weight was lifted till stopped by exhaustion 26 times in the first series, and 26*5 in the second ; hence it cannot be said that any influence of training was exerted in the comparative experiments. The effect of forced breath- ing in increasing muscular power can be tested by anyone while sitting quiet in his own room. My friend Dr Louis Parkes lifted a G 42 RBSPIEATION OF MAN weight of 8;^ lbs. fifty times while in a state of physical and mental repose ; and after forced breathing for one minute and a half he raised the same weight to the same height 125 times. A lady reclining in an arm-chair lifted with her right arm a tea-kettle weighing 4 lbs. 13 oz. sixty times, and after resting ten minutes and breathing forcibly for one minute raised the same tea-kettle 100 times to the same height. The greatest effect was produced on a medical friend, who after ordinary breathing lifted a weight of 4 lbs. 203 times in succession, and after a rest and forced breathing for two minutes lifted the same weight the same height no fewer than 700 times. In this case voli- tion taxed the muscles to the utmost, and the arm remained tired and stiff for some days afterwards. The weights in all these experiments were lifted under natural or automatic respiration after forced breath- ing had been discontinued. It now became necessary to determine experimentally if under forced breathing there was really an excess of oxygen absorbed in the body independently of the CO^ produced ; the methods in use for the determination of carbonic acid and oxygen in the expired air being extremely dehcate, the residts obtained may be thoroughly trusted. The experiment was undertaken in the following way. After rest- ing for some time in the arm-chair the expired air in normal breathing was collected for subsequent analysis, then forced breathing was practised and continued for about two minutes and the air expired collected separately. As soon as the appointed time had elapsed a signal was given, and the person under experiment relapsed suddenly into automatic breathing, while at the same time, by means of a three-way stopcock, the air expired was diverted into a third receiver, breathing being continued until it had come back to its normal condition in repose, which took place within six or seven minutes. There were thus three samples of air for analysis. The volumes of air inspired in each stage were calculated, as previously explained, from the nitrogen found, which underwent no change. The difference between the volumes of air inspired and expired (after the application of a correction for carbonic acid emitted from the LECTURE III 43 blood, into which subject it would take too long to enter at present*") gave the volume of oxygen absorbed, and it is the excess of this oxygen absorbed in the body in forced breathing, over the oxygen absorbed in normal respiration, immediately before, wliicli concerns the present inquiry. In six experiments the increase per minute above the normal oxygen absorbed under forced breathing varied from 47 to 36-4 c.c, with a mean of 18-2 c.c. (49-9 c.c. mean absorbed normal, and 68-1 mean absorbed under forced breathing). At the same time the volumes of air expired were greater under forced breathing by 87 per cent, of normal. Therefore in these experiments considerably more air had been inspired, and there was a marked increase of oxygen absorbed. So far the argument stands thus. Forced breath- ing is accompanied by an excess of oxygen absorbed in the body and leaves in its wake increased muscular power, but this excess of oxygen absorbed is very insufficient to account for the increase of carbonic acid produced towards this development of muscular power-, hence it is used for another object. Nothing, therefore, is left to explain the excessive development of force but an increased effect of volition or brain-power, brought about by the absorption of an exces- sive amount of oxygen in its motor centre. This is a new departure, and one which appears to be fraught with interest. If the exercise of the will for forced breathing, with response, necessitated the absorption of oxygen, it was natural to conclude that the exercise of "volition" for forced breathing, while checking to the utmost the response to this act of volition (a check which can be exerted to a marked extent), would be attended by a similar result; and if so, it should also prodiice an increase of muscular power as observed after forced breathing. This mode of reasoning gave rise to the following experiment. In a state of mental repose, I lifted a weight of 10 lbs. 42 times to a height of 18 inches, when the arm became too tired to continue the work. After a sufficient rest the will was applied to forced breathing, with checked response, for two minutes ; of course it was impossible to avoid the automatic * See Methods of Investigation and Analytical Results, p. 99. 44 RESPIRATION OF MAN inspiration of a slightly increased volume of air, and on suspending volition I was able to lift the weight 76 times, being an increase of 34 liftings. A similar experiment with another person gave 70 liftings for normal, and 96 after the exercise of volition towards forced breathing with checked response ; therefore in both these instances the increased development of muscular power cannot be looked upon as due to forced breathing. It has been observed that ordinary forced breathing invariably shows a pause or state of apnoea on returning to automatic breathing in repose ; I may noAV state that when volition is applied towards forced breathing, with checked response, there is no pause. If under the influence of volition, towards forced breathing, with checked response, a greater development of muscular power is obtained in the same way as when volition is exerted for forced breathing, and if forced breathing is, as previously shown, attended with an increased absorption of oxygen, it appeared probable that an excess of oxygen would also be absorbed under volition for forced breathing, though with checked response, and a number of experiments were made which showed that such was the case. In these experi- ments, six in number, the increased absorption of oxygen in the "volition" stage varied from 1*5 c.c. per minute to 48 c.c. per minute, with a mean of 23'9 c.c, and, moreover, it was observed that this excess was nearly balanced by a corresponding diminution of oxygen absorbed in the after-stage. It should be borne in mind that in these experiments, the oxygen determined as " absorbed " is taken from the air exclusively, and does not show the total volume of oxygen absorbed by the motor centres, as it is impossible to ascertain how much is supplied from the tissues. In another series of five experiments, the will being applied, without response, to running or rowing, the excess of oxygen absorbed in four of the five experiments varied from 7"7 c.c. to 18*5 c.c. per minute, with a mean increase of 9"8 c.c. per minute. In one experi- ment the oxygen absorbed was the same in the two stages. These experiments were undertaken at a mean period of two hours eighteen LECTURE III 45 minutes after breakfast (one after lunch), and therefore under the influence o£ food. Another series of seven was subsequently made at a mean time of three hours fifty-three minutes, or nearly four hours after breakfast, when the direct influence of food might be considered as over. These experiments were attended with a large excess of oxygen absorbed under volition — an excess observed in every experi- ment, and amounting to a mean of 42"8 c.c, or double the volume absorbed in mental repose. This increased absorption when fast- ing is remarkable ; at that time the minimum amount of oxygen would apparently be present in the tissues, and a larger proportion would in consequence be supplied from the atmosphere, accounting for the result obtained. The oxygen absorbed was now determined on three difl'erent occasions after applying the will without response towards lifting a heavy weight ; the results in these cases were well defined. In one experiment the excess of oxygen absorbed per minute under volition was 15'6 c.c, in another 13"8 c.c, and in the third 35'8 c.c, with a mean of 21'7 c.c. The oxygen absorbed in the after-stage in these last two series of experiments again very nearly compensated the excess under volition. It follows that whenever volition is applied towards any form of exercise there is an absorption of oxygen which must of necessity be localised in the cerebral centres concerned in the phenomenon ; and apparently, with an excess of oxygen absorbed, more work can be done than if the excess be wanting. The following experiment, iu which a mixture of oxygen gas and air was breathed, is a striking confirmation of this view. The author lifted a 10-lb. weight forty-one times before being exhausted. After a rest he exercised his volition strongly towards lifting a weight for one minute and a half, and then raised it sixty-one times in succession. Again, after another rest, he exercised the same kind of volition as before, while inspiring a mixture of two thirds of air and one third of oxygen, found by analysis to contain 43 percent, of oxygen, instead of 20'9 per cent, as in atmospheric air, and immediately afterwards lifted the weight eighty-seven times before being arrested by fatigue; therefore, under the influence of volition 46 RESPIRATION OF MAN and air twice as ricli in oxygen, he could lift the weight twenty-six times oftener than after inspiring atmospheric air, the will having been applied in each case in a similar manner. This experiment repeated on another person gave with volition and atmospheric air seventy- seven liftings, and under the influence of volition with a mixture of air and oxygen similar to the previous one, ninety-four liftings, or an increase of seventeen liftings. It might be added that the author experienced a very uncomfortable sensation in the head while inspiring oxygen under an efibrt of volition, a sensation which was not felt when breathing oxygenated air under ordinary circumstances. Breathing oxygenated air tinder an effort of volition towards locomotion is recorded in the accompanying chart, in which the apnoea is strongly marked on suspending the volition (e f and B g). If, however, the volition be directed towards forced breathing with checked response, there is no pause (h i and i k), showing that the excess of oxygen in the air breathed has nothing to do with the pause. Returning to the respiratory tracings under the influence of volition, we find that, whether the will be applied without response to locomotion, to manual labour, or to forced breathing with response, the curve is about the same — that is, first the tracing is steeper than normal; and then, on releasing volition, ther6 is a pause, followed by another rise, showing an increased volume of air breathed beyond the normal. One tracing under volition differs from all the others : it is that for volition towards forced breathing with checked response, when the pause is altogether wanting. Experiments have shown that this same absence of apnoea takes place when the will or attention is concentrated on deep breathing with response, until the volume of air breathed has reached its maximum figure. The experiment, which appears to me of interest, is made as follows : After obtaining a tracing of his respiration while in the state of rest, both physical and mental, the person under experiment directs his attention to his respiration, while breathing deeper than usual ; several tracings may be taken in succession, the breathing becoming deeper and deeper, while the attention is directed 24. BREATHING CHART. 2: Bs/huxS^ io Jialf orv^vruxL size. Sminuf . rr 4 minu te g. AA. Norma] inspiring atlnosplienc air. BC. Narma insprrmg 47 X (^2 Oxygen "by V°1- ) CD. After Stage , mspiriixg air. West.NeirmaTilxtii EF. Voliti.C3a ibr running mthDutresponeemspiring V3 0. "by volume. FG. After Stage mspirmg aar. HI. "Volition for forced'breafh.iiig TO.th.out response IK After Stage inspiring air. 26 BREATHING CHART. 2 minutes. Hedujcecl. to half oru/znjoL svze-. 3 jnimiteg, 4jttinu(fis. ljitr«a» AANormal. B-C . Yolition IzTnirLntes for deep Toreathing . CD . After Stag e litre ■. "WestWewman lith. LECTURE III 47 to the respiration. Afbei' each tracing the attention is withdrawn, when quiet automatic breathing follows ; in no case is there any pause or apnoea, the curve returns gradually to the normal. This is clearly seen in the accompanying chart. Therefore in one case we have a pause on the suspension of volition, in the other no pause, yet in both cases there has been an excess of air breathed, and therefore of oxygen available for the blood. It is, consequently, not the oxygen absorbed which can have occasioned the pause (apnoea). The explanation of this pause appears to be the following : — "When volition acts towards muscular contraction, such as running, without response, the volume of air inspired is automatically in- creased, consequently there has been a direct action of the motor centre concerned in the muscular contraction on the centre of respiration. Now, volition being suddenly suspended, the centre for respiration exerts alone its power; but this centre of respiration has not yet shaken off the influence of the motor centre, which has just been dropped; hence, the respiratory centre is slow in asserting itself, in consequence of which the pause or apnoea follows. On the other hand, when the respiratory centre alone is concerned, then on the suspen- sion of volition no time is lost, and this centre is free to assert itself at once under the influence of reflex action ; in such cases there is no pause or apnoea. In accordance with the theory given above, the apnoea in forced hreathing would be due to the influence of motor centres other than those of respiration. At first sight it is difficult to suggest what other centres, besides those of respiration, could be brought into action ; but it should be recollected that in forced breathing, muscles besides those concerned in normal respiration are brought into \\%e, and these would be controlled by brain centres different from those of respiration. The present view does not take- into account the fact that the heart's action continues unimpaired, or but very slightly weakened, during the apnoea in man ; the phenomenon is looked upon as com- mencing at the brain and not at the heart. There must be a force 48 RESPIRATION OF MAN maintaiaing the pulsalioa of the heart in the absence of respiration, or at all events doing away with the desire for breathing, and that power or energy, whatever its nature, must be the outcome of the forced breathing or of the increased pulmonary ventilation immediately preceding the pause. The experiment described by Hirn* in which a band of iudia rubber being stretched with the hands becomes warm, and therefore a source of energy, may point to an explanation of this storage of power. The exaggerated expansion of the thoracic walls "would likewise generate heat, or at all events a storage of energy calculated to assist in keeping up the heart's action during the respi- ratory pause. Although this explanation of the occurrence of apnoea in man has been long and maturely considered, still there is room for another and more satisfactory solution to this interesting question. It has been objected to these experiments that animals, such as dogs or rabbits, when subjected to forced breathing by artificial respiration exhibit a marked apnoea when the artificial respiration is suspended. Granted this, still the experiment cannot compare with those described above on man. The person under experiment was not subjected to artificial respiration, and his volition, alone, was concerned in the occurrence of the apnoea. I thought at first that possibly volition might have something to do with apnoea produced on animals by artificial respiration, but that such is not the case is shown by a very simple experiment which at my request my friend Dr J. L. Prevost kindly performed in my presence in his physiological laboi'atory at the Geneva Medical School. A cannula was inserted into the trachea of a rabbit and artificial respiration carried on by means of a bellows, a small hole in the india-rubber tubing allowing the expira- tion to take place. This was followed by marked apnoea. Next a solution of chloral hydrate was injected into the jugular vein of the rabbit, in small quantities, until absolute insensibility had been produced. Then, after practising artificial respiration as had been done before, the apnoea again clearly appeared. * ' The Mechanical Theory of Heat,' vol. i, 3rd edit., p. 9. LECTURE III 49 It might also be objected to these experiments that the volume of oxygen absorbed from the air in normal respiration is possibly liable to change every few minutes, and that the increase obtained under volition may be due to some other cause than the exercise of the "will." In order to answer this objection the following experiments were made. Air was expired while in mental repose, and reclining in an arm-chair, in three successive bell jars, each receiver taking seven or eight minutes to fill. The three samples of air expired were analysed separately, and the experiment, being repeated on three different days, gave the following figures for oxygen absorbed per minute : Cubic Centimetres of Oxygen absokbeb per Minute. Experiment I. Experiment II. Experiment III. 49-5 . . 43-0 . . 42-3 53-9 . . 42-0 . . 41-5 48-6 . . 46-6 . . 38-5 The greatest difference per minute in each experiment was therefore 5"3 c.c. in the first experiment, 4"6 c.c. in the second, and 3"S c.c. in the third, showing but little change in the oxygen absorbed in three successive experiments, and giving much confidence in the result obtained. All these experiments lead to the conclusion that the effort of the will, and no other circumstance, is the cause of the increased volume of oxygen absorbed. Now where can that oxygen go to in the body ? There must be a demand for oxygen somewhere, because, as shown in my first lecture, no oxygen is taken into the body unless it be required, and the only demand in the body is for the exercise of volition.* An additional power is given to the muscles by a preliminary efibrt of volition ; naturally there must be an increased amount of carbonic acid produced in proportion to the increase of strength developed. Three experiments were made, which showed clearly that such was the * The reader is referred to the Supplement to these Lectures, where this subject is fully developed. 7 50 RESPIEATION OF MAN case. The mean relation of the strength developed was 1 to 1"300, and of COg to CO2 while engaged in the extra work was 1 to 1'396; there was not, therefore, much difference between those relations for such a small number of experiments. If after exercising the will, instead of returning immediately to the state of physical and mental repose the weight of 10 lbs. be raised in the usual way for one minute, followed by repose, while a record of breathing is taken on the chart, the pause which has been checked by the exercise now appears, and afterwards increased respiration returns. Finally, if immediately after the exercise of volition for one or two minutes stepping exercise is taken for one minute, followed at once by a return to the sitting position, and lifting the weight, say, ten times in succession, on assuming the state of rest the pause will again appear, though perhaps less marked, followed by a considerable increase in the pulmonary ventilation beyond the normal in repose. This is clearly seen in the subjoined chart recording the experiment (see chart). Another chart is appended in which the stepping and lifting have not been preceded by the exercise of volition ; this chart clearly shows the absence of any apnoea. If anybody should be still disposed to question my contention that the increased muscular work in these experiments is due to the influence of volition, the experiment of Mosso, quoted at the begin- ning of this lecture, showing that fatigue of volition suffices to arrest muscular contraction, might be quoted as strongly in support of the views advocated on the present occasion. The following experiment, suggested by that of Professor A. Mosso, and which I have not seen elsewhere recorded, yields results in entire keeping with those he has obtained, while at the same time it confirms the foregoing conclusions, and differentiates distinctly the motor centres of the brain. Let a person, while sitting in an arm-chair, raise a weight, as in the experiments related above, until his arm is too tired to continue the work. He then takes a rest in mind and body of, say, one minute, and again resumes lifting the weight as long as he can. The number of times the weight is lifted is counted in both 15 LitreB, 1 minute. BREATHII 3 mil ?G CHART. nutes. Sedzj-ced ix> haW oriffiTvcd. aiza. »>niTn.teii. 4 minuteB. 31 ii,y i^ttws 31 HO / 30 2» / 8S 28 / 2« 31 / Q 37 2fi / ?lfi as / 25 ?A / 24 23 / 23 22 22 21 d/ 21 20 20 Ifl 1ft 18 1R n 17 m b/ Vn IS 15 14 14 1R / 1» 12 / 12 n / n 10 1 / 10 ft / / a a / / 8 ■7 / 1 T e A 5 / 1 5 4- / 1 4 3 / /A 3 - 2 .-^ r "^ 2 = 1 /^ / 1 i -T i. /A 4 ----- /a *i6 Sec* i >■ — — 1„ -..4... ----<-- -- — -—— . = AA. Normal. AB. Steppng (limn.) BC. After Stage. BD. Lifting and lowering weight (lbs. IQJ DE. After Stag "W« st^NewmaiL ^ilih.. Litres, 1 Hxinute BREATHING CHART, 2 roinutes, R&dij.cedj to ficdf ovigiTixLb size-. 3 minute B, XX 4 minu te b Litre B» A A. Normal. B C . VolitioTL to-wards locoinotioii. CE. Stepping 66 times per minute, EF. After Stage. E G. rift-ing and lowering alternately a wei^t o£ 10 lbs , G-H. After Stag,e. LECTURE III 51 cases, and is found to be nearly the same, showing that the arm is practically rested after the lapse of one minute. Next a rest is taken, pei'haps, for ten minutes, and the same kind of exercise repeated until the arm is exhausted. At the expiration of that time the arm is placed in a state of repose, but the " will " continues being applied as strongly as possible towards the exertion of lifting the weight, and this is continued for one minute. At the end of that minute the weight is again lifted with that same arm, which is then found to be so tired that it is not equal to raising the weight by perhaps more than about one half the number of times the weight was lifted under precisely similar circumstances without the appli- cation of the will. If, however, during the interval of one minute between the liftings the will be directed towards a different kind of muscular work, such as running uphill, on resuming the lifting, the arm is found to be fresh and rested, and can raise the weight the same number of times as if the mind had been at perfect rest for that minute. The following are two experiments which illustrate the phenomena. While reclining in a deck-chair I raised a weight of 10 lbs. forty-nine times, and gave up from fatigue ; after resting for one minute I lifted the same weight to the same height forty times. A long rest was now taken, and the weight lifted forty-seven times, when the work was stopped by fatigue ; then the arm was rested, while applying volition as sti-ongly as possible to a continuation of the same effort of lifting for a lapse of one minute. Lifting was now resumed, when the weight felt very heavy, and could only be raised twenty-one times — clearly not because of the fatigue of the muscles, as they were rested, but from the exhaustion of the power of volition. A similar experi- ment on my assistant gave the following results : — normal liftings, forty-two ; after one minute's mental and physical rest, forty-one liftings ; after a prolonged rest, forty-four liftings ; after one minute's physical rest, but with volition exerted towards a continuation of the same exercise, thirty-one liftings. The same experiment was repeated by both of us without applying the will towards the continuation of the 52 RESPIRATION OF MAN same exercise, but towards another, such as running, thereby resting the motor centre on which volition had exerted its action towards lifting the weight. After a minute the arm felt perfectly rested, and raised the weight the same number of times to the same height as before. This experiment clearly shows the fatigue of volition which checked mus- cular action, although the muscles themselves were not tired, as one minute's interval had proved sufficient to rest the arm nearly if not entirely. LECTURE IV 53 LECTURE IV Me President and Gentlemen, — So far we have dealt with the phenomena of respiration as carried on in the ordinary course of life. I now wish to draw your attention to breathing under circumstances which are not of daily occurrence, and first of all on ascending into high altitudes. This is an important question, not only physiologically, but also with reference to the modern treatment of phthisis. On rising on a mountain slope the air pressure falls, and the pulmonary ventilation increases in order to aerate the blood to its full extent. I hope presently to succeed in explaining that, although the volume of air breathed increases on rising higher and higher above the sea level, still the weight of that air is lessened, or its volume reduced to dryness, freezing-point, and sea-side pressure diminishes. It may be said that climbers, as they ascend higher and higher, breathe less and less air (reduced) for the production of a given volume or weight of CO2. In order to make myself perfectly clear, allow me to enter into a few preliminary considerations. Suppose a person in London, or near the sea level, should inspire in a perfect state of rest 45 litres of air per minute, and expire 0'374 grm. of CO^in that time, it would be the same thing as if he expired 1 grm. CO2 for every 12 litres of air inspired. Now, on rising on a mountain slope if the atmospheric pressure should fall — say by one quarter of its pressure at the sea-side, it might be thought that the volume of air inspired would necessarily be greater by one quarter than that inspired at the sea-side for the emission of the same volume of CO3, amounting therefore to 15 litres per minute ; but such is not the case, as less than 15 litres are actually required. It must be understood that the volumes of air breathed (reduced) decrease 54 RESPIRATION OF MAN at increasing altitudes, a fact first published by a Swiss gentleman, Dr Mermodj in ISrS, and which I confirmed a few months later with observations made at much greater altitudes, his experiments being unknown to me at the time. Although the volumes of air (reduced) breathed on ascending diminish, still a number of experiments made at different levels, on the Peak of Tenerife, have shown me conclusively that the CO^ expired in perfect health remains unaltered at different altitudes, certainly up to about 12,000 feet. In this I regret I cannot agree with Dr Mermod, who finds the CO2 expired to become greater at increasing altitude. (The subject has been fully discussed in the ' Phil. Trans.,' 1890.) Discai'ding for a moment the idea of the influence of altitudes, it is well known that when the temperature of the atmosphere falls, a greater amount of air is breathed and more COg expired, but the volume of air breathed for the emission of a certain weight or volume of OO3 is proportionately less. Therefore a fall of the atmospheric temperature gives rise to the same kind of effect on respiration as increasing altitudes without change of temperature. My earliest experiments on the Breithoi'n, 13,685 feet; St Theodule Pass, 10,899 feet, where I remained a week ; the Riffel, 8824 feet ; the St Bernard, 8115 feet ; and the Ool du Greant, 11,030 feet, were all attended with a fall of temperature at increasing altitudes ; of course this circumstance necessarily produced an increased combustion in the body in order to overcome the action of the cold. It was therefore impossible to deter- mine in the Alps the exclusive influence of atmospheric pressures on respiration, hence the necessity of selecting for these experiments a mountain of sufficient height, situated near to the tropics, where one might expect to find the temperature fairly equal and warm at different altitudes, and therefore free from the necessity of increased com- bustion in the body to resist the effect of an accession of cold. With that object in view, I decided on visiting the Island and Peak of Tenerife in 28° latitude, and carried out this object in the summer of 1878, taking with me all the necessary instru- ments. Three weeks were spent on the Peak while engaged in this LECTURE IV 55 inquiry, which was undertaken at three different stations varj-iug in altitude. Tlie first station was the sea-side, the second the Plateau of Guajara at 7090 feet on the Peak, and the third Alta Vista at 10,700 feet, while a few experiments were made at the foot of the terminal cone at 1,1,740 feet. The temperature varied but slightly on the Peak stations, though somewhat higher at the sea-side, but there was no cause for any marked influence of temperature on the formation of CO3 in the body. The bright sun was indeed intensely hot at every station on the Peak, so much so that the hand could not be left for any time in contact with the sand on which we stood. I had taken the precaution to include amongst my baggage a screen made of boards, six feet in length, which could be raised on light poles, the sheltered area being increased by awnings ; it was under this shelter that the work was carried on. The air was expired into an india-rubber bag of known capacity, and a sample of this air shaken with baryta water in a glass cylinder. The fluid having absorbed all the CO2, was afterwards collected in bottles — one bottle for each analysis — and carefully stoppered, the final analysis being made at a subsequent period. The following results were obtained, every figure being the means of the number of experiments entered between brackets. Litres of air expired (reduced to dryness, freezing-point, and sea-side pressure) for 1 gramme CO3 produced : — Litres. Temperature. Sea-side 12-2 . . 757° . . (20) Guajara (7090) .... 11'9 . . 69-6° . . (21) Alta vista (10,700) . . . 10-7 . . 64° . . (20) Foot of termiHal cone (11,740) . 10-6 . . 64° . . (5) The difference is not great, still for 10,700 feet it amounts to 1-6 litres, which means that about an eighth less air (reduced) was required at the two higher stations to produce through the respiration the same amount of CO3 as at the sea-side. In other experiments made on the Col du Geant while the air was very cold, the extreme volumes of air breathed (expired) for 1 gramme 56 RESPIRATION OF MAN of CO3 were 15"5 litres and 12"6 litres for a difference of altitude of 9800 feet, equal to a reduction of about one fifth. In tbe case of a young companion on the Col du Geant, the reduction between the foot of the pass and its summit, for 1 gramme OO3 was from 13*7 litres to 12'6 litres, or rather less than a twelfth part. Again at altitudes varying from 8115 feet to 13,680 feet, the reduction was from 13'6 litres to ll'OS liti^es, equal to a falling off of 2'6 litres expired for 1 gramme CO3. The mean of all these experiments gave for a difference of altitude of 11,256 feet a reduction of air breathed for 1 gramme of CO2 produced, equal to 203 litres. These experiments show that the aeration of the blood takes place more readily at high altitudes, from the effects of reduced pressure and fall of temperature, than it does at the sea-side. It is, indeed, not easy to account for the greater readiness of the aeration of blood under low pressure. Paul Bert has observed that blood from various animals forwarded to Paris from the town of La Pas in Bolivia, 12,139 feet above the sea, when shaken with oxygen gas, had the power of absorbing considerably more oxygen than the blood of similar animals kept in Paris, and concludes that the Bolivian blood contained more haemoglobin. This may be perfectly correct, but apparently such a character of the blood could only be acquired after a number of years, if not of generations ; while in my experi- ments the effect was produced, if not immediately, certainly after a few hours, when no change in the constitution of the blood could possibly have taken place. There is an interesting experiment bearing on this subject made by Dr Edward Frankland ; he found that candles burned more vividly and brightly in air rarified by means of an air- pump than in the surrounding atmosphere, and concluded that oxygen in rarefied air has a greater mobility than in air under atmospheric pressure. The more ready passage of oxygen into the blood at the lungs on reaching high altitudes may be due to some similar cause. It will now be interesting to consider the medical aspect of the question with reference to the treatment of phthisis in high winter LECTURE IV 57 stations. People residing in such places as Davos aud St Moritz must live under circumstances facilitating the aeration of their blood, and I have no doubt that this is a primary and important cause of the beneficial effects produced. The extreme cold experienced in these winter sanatory resorts must also prove beneficial for the very reason that cold reduces the volume of air required for the produc- tion of a given amount of CO2, so that both altitude and cold join in facilitating the respiratory changes. Interesting information on the resistance to cold at Davos is contained in the Lumleian Lectures on Aerotherapeutics delivered to this college in 1893 by Dr C. T. Williams. We are indebted to Dr Frankland for another experiment which throws light on this same subject. Having carried across the receiver of an air-pump a platinum wire connected with a battery, he passed a current through the wire, and made it red-hot. On exhausting partly the receiver, he observed the wire to glow with a much greater brilliancy, and therefore to lose less heat, but as soon as the air was restored the brilliancy fell to its pristine condition. He concludes that light air removes less heat by conduction than comparatively heavy air, and proposes a theory in accordance with this experiment to account for the fact that in perfectly still air, cold is not nearly felt to the same extent in high winter stations as it would be at the sea level. On further examination into this subject, if increased atmospheric pressure should exert a tendency towards the withdrawal of heat by conduction, this must be synonymous with the production of cold. It is stated by Paul Bert, in his book on barometric pressures, that compressed air develops no unusual sensation of heat ; on the contrary, it has a tendency to the production of a feeling of cold, although the temperature of the compressed air chamber should be higher than that of the external air ; and with some persons particularly subject to the impression of cold he observed the sensation of cold to increase the longer the exposure and the greater the pressure. I cannot help believing with Dr Frankland that increased lightness 8 58 RESPIRATION OF MAN of the air, by checking loss of heat by atmospheric conduction assists materially in accounting for the remarkable circumstance that patients at Davos are so little troubled with the intense cold. On attaining on a mountain slope in the Alps to an altitude of about 8000 feet, the respiratory frequency begins to increase. In an ascent of Mont Blanc, long before the summit is reached, most parties stop, for a few seconds, every ten or fifteen steps to take breath, especially when walking is laborious from soft snow. Training now asserts itself, climbers in good condition think nothing of Mont Blanc with its 15,785 feet, but tyros — and there are many — are apt to give way to fatigue, or to a sleepy sensation, or to mountain sickness. Perhaps the most remarkable illustration of the importance of training is shown in the case of Mr Whymper, who, having fought his way slowly and patiently to the summit of Ohimborazo, 20,517 feet, in spite of the suffocating eflTect of the low atmospheric pressure, experienced no diffi- culty whatever in repeating the same ascent six months later, having been engaged meanwhile in explorations at great altitudes in the Andes. It was shown in my last lecture that a connection existed between respiration and volition, I may, therefore, now be permitted to draw the reader's attention to the effect of low atmospheric pressures on volition. Paul Bert shut himself up in an iron chamber, and sub- mitted himself to a considerable reduction of pressure. At a pres- sure of 17'5 inches, while breathing the air of the chamber, having attempted to whistle, he found it impossible to do so ; at 17 inches he suffered from dizziness, which recurred at 16" 6 inches ; at 16 4 inches he felt rather unwell, and having counted twenty-eight pulsations at the wrist in twenty seconds, experienced great difficulty in multi- plying that figure by three : he writes in his note-book, " difficult to calculate." These statements are interesting as showing that Bert experienced in a marked degree what we might call want of power to exercise volition under very low pressures. When the pressure had risen to 23*2 inches he began to recover his powers of whistling. Is this not an illustration of the action of oxygen towards promoting the exercise of the will ? LECTURE IV 69 A more remarkable instance of the effect of a deficient supply of oxygen towards the suspension of the action of volition is found in the account given by Glaisher of his balloon ascent with Coxwell on the 5th September, 1862, when at an elevation of 29,000 feet, the balloon still rising rapidly, he lost consciousness. Allow me to ex- tract verbatim from Glaisher's book, ' Travels in the Air :' — " At 1 o'clock and 51 minutes the barometer read 108 inches ; after this I could not see the column of mercury in the wet bulb thermometer, nor the hands of a watch, nor the fine divisions on any instrument. I asked Mr Coxwell to help me to read the instruments. In conse- quence, however, of the rotatory motion of the balloon, which had continued without ceasing since leaving the earth, the valve line had become entangled, and he had to leave the car and mount into the ring to readjust it. I then looked at the barometer, and found the reading 9|- inches, still decreasing fast, implying a height exceeding 29,000 feet. Shortly after I laid my arm upon the table, possessed of its full vigour, but on being desirous of using it I found it powerless ; it must have lost its power momentarily ; on trying to move the other arm I found it powerless also. Then I tried to shake myself and succeeded, but I seemed to have no limbs. In looking at the baro- meter my head fell over my left shoulder. I struggled and shook my body again, but could not move my arms ; setting my head upright for an instant only it fell on my right shoulder, then I fell baclovards, my back resting against the side of the car, and my head on its edge. .... As in the case of the arms, so all muscular power was lost in an instant from my back and neck. ... In an instant intense dark- ness overcame me, so that the optic nerve lost power suddenly, but I was still conscious, with as active a brain as at the present moment while writing this. . . . While powerless I heard the words ' temperature ' and ' observation,' and I knew Mr Coxwell was in the car speaking to and endeavouring to rouse me before conscious- ness and hearing had returned. I then heard him speak more emphatically, but could not see, speak, or move. . . . Then the instruments became dimly visible, then Mr. Coxwell; then shortly 60 RESPIRATION OF MAN I saw clearly. Next I rose from my seat and looted around, as though waking from sleep. ... I tLen drew up my legs, whicli had been extended, and took a pencil in my hands and began observations. ... It is probable that three or four minutes passed from my hearing the words ' temperature ' and ' observation ' till I began to observe." The case of Mr Grlaisher is very remarkable if taken in conjunction with the fact, which I look upon as proved experimentally, at all events as far as experiment can go for the present, that the exercise of volition requires the direct action of oxygen on the brain centre. In the present instance the conception of volition was not in abeyance, as Mr Glaisher could direct his will as he pleased, but there was no response ; he wished to move his limbs and could not. Hence, as far as can be concluded from the experiment of Bert and the narrative of Glaisher, the conception of volition does not require oxygen, but the manifestation or response of volition cannot be carried out without it. There is an effect of rarefied air interesting to note in connection with the action of oxygen on motor centres, that is a sensation of drowsiness frequently experienced on high mountains. Low pres- sures, especially when accompanied by intense cold, have a peculiar influence on the mental faculties, and appear to check the exercise of volition. The person afi'ected will insist on going to sleep, be it only for a few minutes, notwithstanding the entreaties of friends or guides who know- that sleep cannot be allowed. Under such circumstances there is nothing else to do but to retrace one's steps downward. So much for the effects of diminished atmospheric pressure ; those of an increase of pressure have been the subject of many inquiries. Paul Bert assimilates the effect of increased atmospheric pressure to the respiration of a proportional addition of oxygen under ordinary pressure. This view, however, does not take into account the cooling influence of compressed air. From Dalton's law the solubility of gases increases in proportion with the pressure; hence under LECTURE IV 61 increased atmospheric pressure a little more oxygen should be absorbed by the blood, which is found to be actually the case by direct experiment. According to Bert there is a slight increase of CO3 expired, which may bo observed up to about five atmospheres, the maximum increase occurring at about three atmospheres. Then the phenomena of oxidation diminish and fall below the normal. He observes, " I know nothing in physiological chemistry more remark- able than this sort of action of the dissolved oxygen, having for its effect not to excite, but to arrest combination." This cessation of the oxidation of tissues from excess of oxygen takes place in all living matter. Even seeds, observes Paul Bert, maintained under pressure no longer germinate. I had occasion to make experiments with the inhalation of atmo- spheric air in which one third was replaced by an equal volume of oxygen. According to the views advocated by Bert, this artificial air, holding about 47 per cent, of oxygen, instead of 20'9, the normal proportion, would be equal to an increase of pressure of a little over one atmosphere; in every case there was a very large increase in the oxygen absorbed by the blood, an increase which clearly exceeded the absorbing power of the blood-corpuscles ; but from a number of analyses of air expired while this oxygenated air was beiug breathed, sometimes the CO3 was found to be the same as that expired with common air, and on other occasions it was slightly in excess (see page 114). As for the slight excess of CO2 expired when the body is placed in an increased pressure chamber, I would be inclined to account for it in some measure from the air under pressure robbing the body of a portion of its heat by conduction. Dr 0. T. Williams has been engaged for a number of years with observations on the eff'ect of increased atmospheric pressure on selected cases at the Brompton Hospital for Consumption and Diseases of the Chest, and he published in 1S85 a series of lectures on ' The Com- pressed Air-bath, and its Uses in the Treatment of Disease.' In cases of asthma he has obtained most decided benefit. 62 RESPIRATION OF MAN I account for the favorable action of compressed air in asthma by looking upon the bath as a method of training respiration. Dr Williams observed that a larger volume of air is breathed after the bath than before ; this increased pulmonary ventilation will obviously assist in ridding the body of its CO^. Had the proportion of COa in the air expired been determined, I have very little doubt but that the percentage vs^ould have been found lower than normal, the pheno- menon being one of unconscious forced breathing. Let us now pass on to another subject. Allow me to draw your attention to the effects of the inhalation of CO2, and first of all to the phenomena observed by the re-breathing of one's own expired air. I have given much attention to this subject, as it appears to me one of particular importance and interest. The experiments were made by re-breathing for five minutes 35 litres of air contained in a bell jar suspended over salt water. The air was inspired through a nasal can- nula attached to a flexible tube connected with the roof of the receiver or bell jar, and expired by the mouth through the stand-up pipe opening inside the receiver. Thus a circulation of the same air was kept up through the bell jar ; at each inspiration the bell jar fell slightly, and then it reseat the following expiration. Little or no distress was felt in the first three or four minutes, though in the last minute a slight feeling of want of air was occasionally experienced. Indeed, the sensation varied considerably with diflFerent persons ; some were quickly afi"ected, while others could go on breathing the air in the bell jar without any particular discomfort for a much longer time. Tracings of this kind of breathing have been obtained from an india-rubber bag by Dr Haldane ; those I am about to show you have been recorded by breathing in and out of a bell jar. As breathing continued the inspira- tion and expiration became deeper and more rapid. It will be observed that the direction of the tracing is not quite horizontal, but has invariably a tendency to fall. This is due to the absorption of oxygen and carbonic acid in the blood, reducing the volume of air contained in the receiver carrying the style ; you will also notice the rapid ascent of the tracing when fresh air is inhaled, after " re-breathing," showing LECTURE IV 63 that a large amount of air is taken in before normal respiration is recovered (see chart, p. 109). The history of the phenomenon is very simple. The CO3 produced accumulates rapidly in the bell jar, and being re-breathed prevents the diffusion of the gas from the blood into the lung cavity, just as would happen if, on dialysing a solution of common salt into pure water, salt was added to the water ; of course this would check the passage of the salt through the membrane of the dialyser. As the COg increases in the air re-breathed, the portion of this gas retained in the blood also increases; indeed, blood can hold a large amount of CO2 in solution. But in addition to the accumulation of OO3 in the air breathed, and absorption of CO^ in the blood, there is another phenomenon to be taken into account — the oxygen in the air breathed falls rapidly, and consequently this air becomes less and less fit to maintain life. In my inquiries five persons submitted to 6, 10, 11, 10, and 5 experiments respectively ; these experiments were made in four different stages as follows : — In the first or preliminary stage the COg was determined in normal respiration; in the second stage 35 litres of pure air collected in the bell jar was re-breathed for a period of five minutes, and the COg left in the bell jar was determined. Immediately after re-breathing, and while fresh air was being inhaled, the air expired was diverted into another bell jar aud collected separately, its CO3 being also determined, — this was the third stage; when from 30 to 35 litres had been thus expired the air given out from the lungs was collected in another receiver — this was the fourth stage ; hence there were four different volumes of air for analysis. The total number of experiments amounted to forty-two, and therefore necessi- tated 168 determinations of CO^, which were all done with equal care by Pettenkofer's method. The oxygen was determined in five ex- periments by means of my eudiometer. The broad results obtained from this inqtdry were as follows.* First, on re-breathing air in a closed vessel, less CO3 is expired * Tte details and numerical results will be found in the "Supplement" to these Lectures, pp. 109, 110. 64 RESPIRATION OF MAN within a given time than in ordinary breathing, a certain proportion remaining absorbed in the blood. Secondly, when fresh air is taken into the lungs immediately after re-breathing 35 litres of air for five minutes, the volumes of air breathed and of OOg expired are greater than in ordinary breathing. Thirdly, when after the re-breathing stage fresh air is inspired, in the course of five or six minutes the blood has recovered its normal state, and given out the whole of the CO^ which had been absorbed in the re-breathing period. Paul Bert considers that he has estabhshed by a large number of experiments that animals when left to die in closed vessels are not asphyxiated from COj, but die simply from want of oxygen ; as would happen if they were submitted in an air-pump to diminished pressures corresponding to the proportions of oxygen left in the receiver in which they were confined; and the same phenomenon could be produced if the COj were absorbed by potash as fast as it was produced. From this view it would follow that the decrease of in the confined air re-breathed is proportional to a decrease in the pressure of the air breathed. In five experiments after re-breathing 35 litres of air for a mean time of five minutes, the mean per cent, of oxygen whicli had disappeared was 19'2, and the mean pressure corresponding to this reduction of oxygen would be 24'23 inches — a fall of pressure which would be equal approximately to climbing to an altitude of 7480 feet (calculated from the means of two months' baro- metric observations taken daily at the Great St. Bernard, 8115 feet); therefore, after breathing 36 litres of air over and over again for five minutes, the state of the respiration would be much the same as at an approximate height of 7480 feet. Such a low altitude would explain the absence of any difficulty or distress in the breathing ; yet it will be observed, by referring to the chart recording the respiration on re-breathing, that distinctly more air was inhaled in a given time towards the close of the re-breathing stage. It was unfortunately not possible to determine the volumes of air breathed. LECTURE IV 66 My assistant, Mr Floris, had occasion to re-breathe about 14 litres of air in a bell jar till he felt very giddy, a dark mist appearing before his eyes. The subsequent analysis of this re-breathed air gave lB'64i per cent, of COg, and only 5"40 per cent, of instead of 20"93. This would correspond to a pressure of 7'74 inches, and an altitude nearing that attained by Glaisher and Coxwell on their memorable ascent from Wolverhampton. It may be asked if there is a limit to the altitude man can reach. The question is impossible to answer, because, as I have shown, when a person rises higher and higher above the sea level he wants less and less air to breathe, or in other words, the air breathed finds its way more and more readily into the blood. The secret for attaining to very great heights is training and time. Whymper reached an alti- tude of 20,517 feet on the Chimborazo. The brothers Schlagenweit rose to 22,239 feet; in 1864 Johnson climbed a ridge in the Western Himalayas which exceeded 22,300 feet, and in the following year is said to have attained to an altitude of 23,728 feet. Sir Martin Conway, in his recent explorations in the Himalayas, ascended on August 25th, 1893, a peak called " Pioneer Peak," of which he calcu- lated the altitude by barometer at 22,600 feet. This digression has somewhat taken us away from the influence of CO2 on respiration, which certainly appears to lose some of its interest if it is to be looked upon physiologically in the same light as hydrogen or nitrogen. It is often asked to what extent we can breathe carbonic acid with impunity, or in what proportions CO^ can be breathed in the atmosphere. The subject was investigated, amongst others, by Professor Emmerich, of the Institute of Hygiene at Munich, and Dr von Pettenkofer. Thege gentlemen, in company with others, shut themselves up in a small vault under the Institute of Hygiene, together with bottles of liquid COj and six lighted candles. The gas was let out of the bottles, and when the lights were extinguished most of the visitors left the chamber; Emmerich and Pettenkofer remained inside, and when seized with headache and discomfort took several samples of air for subsequent analysis, then leaving the vault none the worse for the 9 66 EESPIRATION OF MAN. experiment. The analysis of tlie samples of air gave a mean of 8 per cent. CO2 ; so that 8 per cent, of COg in air can be breathed with- out producing any serious effect. In the autumn of 1893 I went to Munich with the object of calling upon Dr von Pettenkofer. Nothing could exceed the welcome he gave me, and among other interesting objects, he showed me the vault where the above experi- ment had been carried out three years before ; oddly enough, we met Professor Emmerich in the Institute, and all three adjourned together to the vault. We all know the intensely fatal effect of breathing pure CO2, which according to Paul Bert might be called air free from oxygen. The following instance is a remarkable case in point ; it happened in 1886 in a small village near Bordeaux. Two labourers named Loubrie and Blanc were working in a shed ; Blanc noticed his wine was fermenting in the vat, and that the grapes were driven to the surface by the gas that was given off. He then got into the vat to keep down the bunches of grapes, and immediately fell suffocated. Loubrie called for help, and a man of the name of Finore, who was working in the neighbourhood, ran to the vat to help Blanc. As he also disappeared, Loubrie determined to try and save both, and he also fell a victim. In succession two other persons went into the vat, notwithstanding the warnings and protests of the bystanders, and they shared the same fate as the others. It was found necessary to demolish the roof with which the vat was partly covered, when only the man Finore was found living. It would appear from statements made by Professor Emmerich, that, according to Professors Friedlander and Harter, rabbits withstood for more than an hour an atmosphere contain- ing 34 per cent. CO3, and even one of 60 per cent, during three quarters of an hour, when very violent breathing set in, accompanied at intervals by intense cramp. After thirty or forty seconds symptoms of coma appeared, breathing became slower and weaker, and the bodily tem- perature fell ; but even after remaining a quarter of an hour in a 60 per cent, atmosphere of CO2 the animals were quickly restored to their normal state when taken into the open air. Asthma. — After having said so much on respiration, allow me, gentle- 31 j^.^^^ BREATHING CHART. Bsdu^aitt-hM- origmal^m^. 0_! iTvipirt. 2 TY,<,.i.f «.. a^im.ta«. 4 minii teg. 31 AA. Normal, B C . Cou-glnrLg . CD . After Sta^ e of Coiigliing "West J^ewnaan lith. , LECTURE IV Ql men, to offer a few remarks on a disease which is peculiarly one of the respiratory function — that is asthma; and first of all, as an introduc- tion to that subject, let us analyse the phenomenon of coug-hing. In coughing a long breath is taken, but it is different from deep breathing. In ordinary deep breathing the air expired is followed by the pause previously referred to on the resumption of automatic respiration in repose. In coughing the respiration is laboured, the muscles having to strain against the closure of the pharynx, and drive out the air from the lungs by forcible expulsion. The residt is an increased formation of CO2; hence at the end of the expiration there is an excess of OO3 in the blood. This is no theory, but is clearly demon- strated by the form of the record on the chart, produced by the expiratory act of coughing, in which there is no pause, no apnoea (see chart) ; but, like the curve of breathing under muscular exercise, it continues rising for a few seconds, then bends downwards, assuming a direction parallel with the tracing in repose.* The last forced expiration in a fit of coughing is followed by a deep breath, taken to supply the blood with a fresh quantity of oxygen, and rid it of the excess of COj produced ; and this is continued until the blood is again perfectly aired, and the CO^ in excess completely eliminated. From the above consideration, it will be understood that in cough- ing there is a distinct tendency to an accumulation of CO3 in the blood, a condition met with, though in a much intensified form, in asphyxia. Now asphyxia is occasionally productive of spasms of the glottis, as seen in some cases of recovery from drowning ; and could it not be that from a similar reason the momentary increase of CO3 in the blood, and possibly the decrease of oxygen, due to a bad fit of coughing, might be productive of spasmodic asthma in people who are subject to it ? The followino- observation was made by a physician who at times had severe attacks of asthma, though usually in the enjoyment of good health. On the 13th of February last, after taking a cup of tea at 2.30 at night, loud breathing came on together with tightness of the chest. He then took a succession of forced inspirations, with the immediate * In certain cases, however, coughing may assume the form of forced breathing. 68 RESPIRATION OF MAN result of arresting both the wheezing and tightness ; later in the same night the wheezing reappeared and forced breathing was again practised, being productive of the same effect, which lasted through the night. In this case forced breathing returned to the tissues the oxygen they were apparently in want of, while removing the CO2. I have shown in my third lecture that oxygen is necessary towards the exercise of the functions of the brain motor-centre ; it appears to follow that a deficient supply of oxygen to the respiratory centres has also something to do with asthma. In keeping with these remarks it may be said that all circumstances productive of an excess of CO^, and therefore leading to a deficiency of oxygen in the body, pre- dispose to asthma ; cold and exercise do so pre-eminently, so does the ingestion of food. A bad fit of asthma is usually ushered in with a sudden loud dry cough, coming on in the evening or at night ; this is instantly followed by a bronchial spasm during inspiration, then comes the acute distress, or a feeling of suffocation. It may be observed that after fighting for breath for ten, twenty, or thirty hours, with occasional short remis- sions, the respiratory muscles and also volition towards the respira- tory effort become very tired. It is difficult to reconcile the fact that some asthmatic persons find themselves the better under lower atmospheric pressures, while others, on the contrary, suffer the moment they leave the sea level. The only explanation to be offered is that some people thus affected take in oxygen more readily under low pressures and others under high pressures. I cannot help comparing asthma in those who suffer under low pressures to a sort of mountain sickness. The higher they go the worse they are, and the moment they return into the lower plains the asthma passes off as by magic. If asthma is a form of mountain sickness, and if that distressing affection of high altitudes can be cured by training for the exercise of climbing, why should not asthma also yield to the training of the respiration, carried out by practising the respiratory movements wanted 32 BREATHIBfG CHAB.T. 2 mixmtea. Seetiuei, to frnif original, s vxe,. 3mii»ite». 4 minutes. AA, Normal .sitting on dumzny cycle . B C _After Stage of stegpizig 84' times perirmxTite . DE .After Stage of cyoliag 14*0 steps per xnmiite. Dottedlines give liLe direction of lin e -under fexercise, (Cycling & Stepping ] . Iiitrea. ^ ■VVest,N"*vwiiflun. Utll. LECTURE IV 69 to carry the tidal air througli the kings ? Of all means of training respiration I think cycling is the best. "When a person first takes to cycling exercise it will be found, especially on going uphill, that the breath is wanting, tbe heart beats uncomfortably, and the legs tire ; but after some training these dis- comforts all disappear, nothing will be thought of hills to ascend, the heart has become perfectly comfortable, all breathlessness has dis- appeared, and the legs will not longer fieel any fatigue. Curves of the expired air taken while riding a dummy bicycle (home-trainer) (see chart) show distinctly that there is little or no breathlessness produced by moderate cycling; while, on the other hand, walking at the speed of eighty-four steps per minute, for example, is productive of a distinct state of dyspnoea, or want of breath. Why should not people liable to attacks of asthma also train their respiration by such a kind of exercise, of course on condition of the heart and lungs being in perfect health ? Cycling exercise first of all increases the depth of breathing, and that without fatigue, as the respiratory movements are automatic ; at the same time it will accustom the rider instinc- tively to take in at each respiration the volume of air required to aerate the blood, and to eliminate a fixed proportion of CO2, leaving in the cir- culation the precise balance of CO3 compatible with health. Moreover cycling can be done to any extent — in great moderation with beginners, and then in an increased amount. Persons who do not care for cycling out of doors can take the same kind of exercise at home by means of a dummy cycle, — known, I believe, as the " home-trainer," consisting of an iron wheel driven by pedals, the resistance of the wheel being so contrived as to simulate bicycle riding. A strap carried partly round the rim of the wheel can be tightened at will by the rider, thus increasing the labour and recalling the effort of riding uphill. There is a marker in connection with the wheel, showing from the number of revolutions the distance apparently travelled in miles. Such a machine might, I feel assured, be used profitably by asthmatic subjects, beginning with an exercise of say half an hour, and daily increased. I have one here for your inspection. 70 RESPIRATION OF MAN My experience of the results of this treatment is unfortunately only limited to one person; in this case it has proved eminently successful. This person took to bicycle riding about three years ago for pleasure, and in very great moderation for the first two years. He observed last summer that the attacks of asthma, to which he was subject, had become very much fewer, — he was only troubled twice with a bad return of the asthma since last Octobei-, the attacks being brought on in both cases by exposure to cold. The tightness and wheezing, which occurred every night, have now entirely disappeared, and his sleep improved. I shall now beg to summarise shortly the Croonian Lectures of the present year. In the first lecture the oxygen of the atmospheric air was shown to be the main agent of life, and Hermann's discovery that oxygen is an integral part of the tissues was appealed to, with the object of explaining the remarkable vitality of certain organisms, such as seeds, and their capability of resuming the function of life after an unlimited period of complete repose. Next came an attempt to explain that it is not the oxygen of the air which, by offering itself to the tissues, produces the phenomena of metabolism, but living tissues call upon oxygen to effect the changes they undergo. The influence of tissues as the prime movers in the matter was shown by the action of cold, which first increases their vitality, and consequently the demand for oxygen, though when excessive it exerts an influence the reverse in its character. Muscular exercise invariably tends to the production of 00^ in excess, and the phenomenon was afterwards appealed to as an illustration of increased molecular vibration ; this led to some remarks on the influence of walking exercise in the act of ascending, on the temperature of the body : it was concluded that with some people there is a slight rise, and with others a slight fall of temperature. The second lecture was prefaced with a short allusion to some of the principal investigations on human respiration ; then followed the history of the different forms of breathing, which were illustrated by tracings taken directly from the person under experiment. Attention LECTURE IV 71 was also drawn to the absorption of oxygen in the body, and a numbei- of analyses were quoted showing to what extent this absorption takes place. The third lecture was given up entirely to the influence of volition on respiration. It was shown that volition without response towards any kind of muscular exercise, including forced breathing, is attended with increased pulmonary ventilation ; and also with the absorption of an excess of oxygen, and that this oxygen is necessary towards the exercise of volition ; if necessary to volition it must be taken up by the motor centres of volition. A remarkable effect on the development of muscular force by this charging of the motor centres with oxygen was found to take place. It was also shown that on the return to the state of physical and mental rest, after volition had been exerted with and without response, a pause or state of apnoea was invariably produced ; but this apnoea failed to appear when volition or attention was forcibly directed to respiration in deep breathing. Finally, an experiment was described in which, volition becoming tired out, the muscles refused to woi'k, this experiment being in keeping with Mosso's remarkable discovery. The fourth lecture was devoted first of all to an account of the influence of climbing on the respiratory changes, and on the state of the respiratory phenomena at high altitudes. Next, air re-breathed under atmospheric pressure was considered, and it was shown tbat when re-breathing the same air over and over again there is an accumulation of OO2 in the body, which is quickly expired when fresh air is breathed. This was followed by statements from Paul Bert and quotations from Mr Glaisher, showing the effects of low atmospheric breathing towards checking the exercise of volition. The lecture was concluded with an allusion to asthma, and to a method of treatment depending mainly on the improvement of the respiratory phenomena by what may be called a process of " training." SUPPLEMENT Methods op Investigation and Analtticai; Rksults It was impossible, while pi'eparing these lectures for the Royal College of Physicians, to describe at full length the methods and details of the present inquiry. Still, no satisfactory and complete account can be given of any experimental reseai"ch without entering into par- ticulars of the experimental methods and analytical results. Hence it was, that after writing the lectures in a form which appeared to me suitable for delivery, I came to the conclusion that they were very incomplete, and required either writing over again entirely, or being supplemented with the particulars which had to be omitted in the lectures. This last alternative has been adopted in order to retain the lectures as much as possible in their original form, while at the same time affording the reader the means of testing the accuracy of the various statements by referring to the details of the work. It is a pleasure to me, while at the same time a duty, to recall the names of the gentlemen who have assisted me in the present inquiry, as well as in other work, and to them all I take this opportunity of returning my best thanks for their labours. First of all, the reader's attention will be called to a large number of experiments and observations made, in order to determine which was the * During the season 1886-87, A. Landriset (afterwards D.Sc). 1887-88, Percy Hoskins, P.C.S. 1888-89, Ch. T. Townsend, F.C.S. 1889-90, Oh. T. Townsend and Edward Russell, F.C.S. 1890-91, Edward Russell, F.C.S. 1891-92, G. P. Darnell Smith, B.Sc. 1892-93, Bernard F. Davis, B.Sc. 1893-94, R. B. Floris, F.C.S. 1894-95, 1895-96, 10 74 EBSPIRATION OP MAN best method of collecting the air expired from the lungs in perfectly natural breathing. When experimenting in the mountains, in the earliest part of the inquiry, the person under experiment first sat down, say for ten minutes or a quarter of an hour, in as convenient a spot as could be found, and then, when his respiration had become perfectly quiet, he collected the air he expired into an india-rubber bag of known capacity under a certain pressure of water. With this object a face-piece was used supplied with very delicate ebonite valves, manufactured by Messrs. Coxeter and Son, and known as " Clover's." The volume of air expired in a given time was determined by observing how long it took to fill the bag. This bag was con- nected to a water-gauge by means of an india-rubber pipe, while through another short tube a thermometer was introduced, giving the temperature of the air within it. In all cases, where portability was required, bags had to be used, but they were objectionable for many reasons ; first of all, because of the difiiculty of gauging exactly the volume of air expired, and then on account of an invariable, though small, loss of OOg by diffusion through the india-rubber texture.* Besides the objection to the use of bags, breathing through the face-piece was far from satisfactory : (1) because the absolute tightness of the valves when closed was not reliable ; (2) because of a slight resistance the valve opposed to breathing ; (3) on account of the space inside the face-piece retaining a certain volume of expired air, which at each inspiration was re-breathed ; and finally, from the difficulty of ensuring a perfect tightness of the face-piece on the face. I can do no better, in order to illustrate the effect of the face-piece and valves on respiration, than reproduce here a chart, showing graphically the respiration with the face-piece and without it. The tracings are obtained in the following way. The person under experiment sitting perfectly quiet in an arm- chair inspires through the nose and expires through the mouth. He * In the covirse of these experiments it was observed that facing the bags with oil-silk glued to the rubber canvas lessened materially the loss of COj by diffusion, and since then the bags used were always protected in this way. litres, 1 miT lUte, BREATHIJ rC CHART. lutest 3 mil iitfls, 4 minutes. 1 ' Utoei 31 30 a 20 R 28 ^ 27 R ?fi 5 ?5 4. G M » r^ ?3 2 /^ 1^?! 1 y^ ^1 y W » r 1» ft 18 7 ly n R / r^ M^ S Yr^ y^ 15 4 ^ ^ r^ 14 a / A^ 13 ? /^ _/" 12 1 r^ r^ 11 y^ r^ 10 A r^ C -^ V 9 H r^ _^ A 1 r^ ^ 7 R r^ A s r^ r^ fl 4 r^ 4 3 ^-^ « E j-^ ^ 2 = 1 / ^ 1 = /b. .A - Li tre.. ^16 S.O.- -#■ i — - "Litre*.'' B C . Valves only. CD. After Stag e . E.F. Valves 3c TleTDreathing . F.G. After Stage. 'West.N'ewrp.ajn lith. METHODS OF INVESTIGATION 75 collects his expired air in a bell jar suspended over water in sucli a way, as will be described later, that no effort is experienced when raising the bell jar at each expiration. As the bell jar ascends, it describes a tracing by means of a style moving over a chart which is fixed to a drum revolving by clockwork, the abscissa lithographed on the chart indicating in litres the volumes of air expired, and the ordinates the time in minutes through which the experiment has been carried on. The first tracing, a a, gives a record of normal breathing in a perfect state of repose. The face-piece is now applied to the face, and the expiratory tube joined with the bell jar through india-rubber tubing. Another tracing (e f) is then obtained of the air expired through the face-piece. It will be observed at once that this tracing is steeper than the other, showing that decidedly more air has been expired, and therefore breathed, than in normal respiration. After breathing through the face-piece has been continued for two minutes, the person under experiment quickly removes from the face- piece the india-rubber tube used for expiration, and discarding tbe face-piece he resumes the original naso-buccal respiration through the india-rubber tube. This can be done with very little or practically no effort likely to interfere with the respiration. Then follows the after- stage, when the tracing r g is seen to continue rising for nearly two minutes, and then to bend downwards parallel with normal breathing. This means that the use of the face-piece for a period of two minutes has produced a slight though distinct amount of breath- lessness or dyspnoea, which continued for nearly two minutes after the face-piece had been removed, when the breathing again became normal.* Having obtained graphic records of the air expired when respira- tion was carried on through the face-piece, it was necessary to ascertain how far the face-piece modified the volumes of air breathed and CO2 expired. With this object in view a similar experiment was repeated five times (though of course without the interference * See chart facing p. 76. 76 KESPIEATION OF MAN of the recording apparatus), when the vohimes of air expired were read off on the scale of the bell jar. On these occasions three different bell jars were used, — one for normal breathing, another for breathing through the face-piece, and the third for the after-stage. The numerical results of the five experiments are shown in the following table, in which the volumes of air and CO3 expired are expressed per minute. Normal. Fiice-piece. After-stage. CO.,. C.c. 183-2 157-0 159-8 171-8 173-5 Volume of nir expired. Litres. . . 3 527 . . . 3-299 . . . 3103 . . . 3-477 . . . 3405 . CO2. P. cent. . 519 - 4-76 . 5-15 . 4-94 . 5-09 Means 169-1 . . 3-362 5-03 Volume of air expired. COo. Litres. . . 5-437 . . . 5-739 . CO,. C.c. 210-2 181-8 177-2 193-9 P. cent. . 3-87 . 316 5-542 . . 3-20 6-213 . .3-12 176-1 . . 5-645 . . 3-12 187-8 . . 5-715 . . 3-29 Volume of air expired. COj. Litres. Per cent. . . 3-358 . . 5-29 . . 3-475 . . 4-63 . . 3-5-20 . . 5-07 CO2. C.c 177-5 160-9 178-6 188-3 4-034 . . 4-67 191-4 . . 3-979 . . 4-81 179 3 . . 3-673 . . 4-89 In the subjoined diagram the line A A represents normal breathing, the curve a b the first stage, and ode the after-stage of the experiment. A With face-piece — Volume of air expired ABC 134-948 litres in 23 mill. 40 sec. Normal, in same time 79567 „ 56 381 ., CO2. ABC . . . . = 4-454 ,. Normal, in same time = 4002 „ ., ,, -452 „ After- stage — Volumes of air expired, c D E 133-271 litres in 36 min. 31 sec. Normal, same time . 122-825 „ ,, „ = 696 % increase of air expired over normal. = 11-3 % increase of CO3 expired. 10-446 . .= 6-518 „ Normal, same time . = 6-178 ,, -340 = 8-5 % increase of air expired. = 5-5 % increase of COj in air expired, METHODS OP INVESTIGATION 77 These experiments show an increase over normal of air expired with face-jnece of 69*6 per cent., and 8*5 per cent, in the after-stage ; total, 78" 1 per cent. : while the excess of CO3 with the face-piece is 11"3 per cent, of normal, and in the after-stage 5"5 of normal ; total, 16"8 per cent. This increased amount of COj expired must be owing in a great measure to the increased labour of the respiratory muscles, due to a sensation resembling that of breathing rarefied air, though really pro- duced by the re-breathing of a small portion of the air expired. Perhaps one of the most remarkable effects of the face-piece and valves was produced on the percentage of CO3 in the expired air. This percentage will be observed in the table to fall from a mean of 5-03 in normal respiration to a mean of 3 "29 with the face-piece and valves. Hence it is obvious that the face-piece produces an uncomfortable sensation, as if from want of air, and exerts an instinctive desire to inhale much more air than would be required to supply the oxygen wanted, and eliminate the CO3 formed. The subject appeared to grow in interest the further it was pursued, and the question to be next considered was to ascertain for what reason the face-piece proved so objectionable in connection with normal respiration. There could only be two ways of accounting for this circumstance : either the obstacle to breathing was due to the small quantity of expired air (about 100 c.c.) which it was impossible to remove from the cavity of the face-piece after each expiration, and which had to be re-breathed; or to the resistance of the valves, slight as it was ; or to both these causes acting conjointly. Again, here the recording apparatus was brought into use, and three tracings were made on the chart in the following way : the first tracing was obtained inspiring through nose, expiring through mouth, without the use of any face-piece, and recorded normal breathing; the second was taken with the face-piece, including both valves and re-breathed air ; and the third was obtained with the face-piece into which a short glass tube had been introduced, one end fitting 78 EESPIRATION OF MAN air-tight into the expii^atory tube and the other projecting into the face-piece, the valves being left in situ. (See drawing, p. 79.) The person under experiment took this tube into his mouth, and expired through it while inspiring through the nose and face-piece. It will be easily understood that in these experiments there was no expired air in the cavity of the face-piece, but the valves acted the same as usual. After breathing for two minutes in this way, the face-piece was removed and the breathing continued, inspiring fresh air through nose and expiring through month into the bell jar ; this constituted the after-stage. These tracings (b o and c d) show distinctly that the effect produced exclusively by the valves is but slight; indeed, though there is a slight feeling of discomfort when the face-piece is used in the ordinary way (with re-bi'eathed air), there is none with the valves alone. The analysis of the expired air confirmed in every way the results obtained with the recoi"ding instrument. In the following table the effect of the re-breathed air only is shown. This was done by collecting the air expired through the face-piece and valves only, and therefore in the absence of re-breathed air, and then by using the face-piece with both valves and re-breathed air, when the air expired was driven into a separate bell jar ; finally the air for the " after-stage" was collected in a third bell jar. The results of the analysis of the contents of the three receivers is now subjoined. METHODS OF INVESTIGATION 79 Pace-piece (Clovee's) with Glass Tube — No Aik re-breathed I. 3 o T ^ Face-piece — A.ir re-breathed Jrrt 80 RESPIRATION OF MAN Exi^ERIMENTS SHOWING THE EXCLUSIVE INFLUENCE OF Rb-BREATHING Normal. Per minute After-stage. Valves only Valves and re-breathing. Witliout face-piece. Volume of air Volume of air *- Volume of air CO2. expired. COj. CO3. expired. CO2. COo. expired. COj. Cc, Litres. Per cent. Cc. Litres. Per eeut. Cc. Litres. Per cent. 1833 . 3-958 . 4-63 1930 . 5-874 . 3-29 187-6 . 3-687 . 5-09 219-5 . 4-578 . 4-79 211-9 . 6-259 . 3-38 265-4 . 5-926 . 4-48 198-4 . 4-137 . 4-79 202-7 . 6-433 . 3-15 207-0 . 4-296 . 4-82 191-4 . 4104 . 4-66 194-4 . 5-120 . 3-80 206-1 . 4 307 . 4-78 174-3 . 4-195 . 4-15 184-3 . 5-843 . 3-15 217-2 . 5-434 . 4-00 191-8 . 4-295 . 4-46 178 4 . 6-513 . 2-74 227-8 . 4-455 . 5-11 174-1 . 4-312 . 4 04 172-9 . 6-201 . 2-79 203-8 . 4-700 . 4-34 190-4 . 4-226 . 4-50 191-1 . 6-035 . 3-19 216 4 . 4-686 . 4-66 In tte above diagram — Volumes of air expired re-breathing, ABC Noi'mal, same time, A c Increase over normal 57131 191-518 litres in 31 miti. 48 sec. 134-387 „ = 42-5 % increase of vol. of air expired over normal. OO2 expired re-breath- ing, ABC. . . . Normal, same time, A c Increase over normal . 6062 6055 = 01 % increase CO2 expired. After- stage : Volume of air expired, C D E 190 539 litres in 40 min. 32 sec. Normal, same time, C E 171-264 „ Increase over normal . 19-245 „ = 112 % increase air expired. = 12-0 % increase CO2 expired. CO2 expired, c D E . 8-644 „ Normal, same time, c E 7-717 ,, Increase over normal . 927 ,, — showing 42 "5 per cent, increase of volume of air breathed over normal with the valves and while re-breathing, and 11"2 per cent, corresponding increase in the after-stage over normal := total increase of 53" 7 per cent. METHODS OF INVESTIGATION 81 Witli reference to the CO3 expired, the increase over normal is 0"1 per cent, in the re-breathing stage, and 12*0 per cent, in the after-stage = together 12'1 per cent.; showing that the increase is entii^ely given out in the after-stage, which, of course, was due to an accumulation of 00^ in the blood. Having considered the effects of the air re-breathed through the cavity of the face-piece, it now remains to inquire into the effects pro- duced when the face-piece is used with the valves only, and therefore in the absence of any re-breathed air. The arrangement of the face-piece has been already described, the analytical work gave the following numerical results : EXPEEIMENTS SHOWING THE EXCLUSIVE INFLUENCE OP THE VaLVES. Normal. Face-piece with Valves and Mouth-piece. After-stage. Volume of air Volume of air Volume of air CO,. C.c. expired. Litres. CO2. Per cent. CO.,. C.c. expired. Litres. CO2. Per cent. COo. C.c. expired. Litres. COo. Per ceu 188-4 . 4-154 . 4-53 . . 198-2 . . 4-440 . 4-46 . . 191-6 . . 4-456 . 4-30 188-7 . 3-719 . 5-07 . . 192-3 . . 3-821 . 5 03 . . 194-8 . . 3-816 . 5-10 176-5 . 3-585 . 4-92 . . 180 4 . . 3-897 . 4-63 . . 179-9 . . 3-579 . 5-02 167-3 . 3-566 . 4-69 . . 174-3 . . 3-809 . 4-58 . . 193-0 . . 3-941 . 4-90 197-8 . 4-575 . 4-32 . . 192 6 . . 4-220 . 4-56 . . 208-9 . . 4-805 . 4-30 183-7 . 3-719 . 4-71 . . 187-6 . . 4-039 . 4-65 . . 193-6 . . 4-119 . 4-74 Valves and mouth-piece : Volume of air expired, ABC 137-823 litres in 34 min. ]? Normal, in same time, A c 127562 ,, „ Increase over normal . . 10-261 ,, „ CO2 expired, A b c . . 6-422 „ Normal, in same time, AC 6-301 „ „ Increase over normal . . '121 „ „ After-stage : Volume of air expired, ABC 137-412 litres in 33 min. 41 Normal, in same time, ce 125269 „ „ 12-143 „ OO2 expired 6-493 „ Normal, in same time, C E 6-188 ,, ,, 80 % increase air expired. = 1-9 % increase CO, expired. Increase over normal . •305 =; 9-7 % increase air expii-ed. = 4-9% increase CO2 expired. 11 82 RESPIBATION OF MAN Therefore in these experiments there was an increase of air expired with valves and mouth-piece (no re-breathing) of 8'0 per cent, and 9*7 per cent, in after-stage, total = 17'7 per cent. ; and of CO3 an excess of 1"9 per cent, with valves and mouth-piece (no re-breathed air), and 4-9 per cent, in after-stage = total 6'8 per cent., which is very small. The final resnlt of this inquiry shows the effect of the re-breathing and valves when acting separately and together ; and, moreover, it will be observed that the figures indicating the individual action of re- breathed air and of the valves in the face-piece, when added together, will be approximately equal to those obtained through their conjoint action. These figures are as follows : Excess vol. over uormal. Excess CO^ over normal. Re-breathing . . . 53'7 per cent. . 121 per cent. Valves .... 17-7 „ . . 6-8 Total . . 71-4 „ . . 18-9 Found both together . 78-1 ,, . . 16-S It is of course impossible, in work of this kind, to obtain figures exactly agreeing for such a small number of experiments ; still they approximate each other sufficiently to show the effect of the air re- breathed and of the valves taken singly ; and also that the influence of the valves taken singly is very slight compared with that of the re-breathed air. By practice, the exclusive influence of the valves would become less and less marked, so that really, were it not for the impossibility of getting rid of the residue air expired, there would be no great objec- tion to using valves on condition that they could be depended on to close lightly, quickly, and tightly, which, however, are desiderata not easily obtained. From the above inquiry it is obvious that the use of a valvular face-piece in experiments on respiration is objectionable; on that account the person under experiment became accustomed to inspire through the nose and expire through the mouth. At first he com- pressed his nostrils at each expiration by a movement with the fingers. METHODS OF INVESTIGATION 83 hardly perceptible, but after some time became sufficiently proficient to do without this precaution. It should be stated that these experi- ments were made either on myself or on my assistants, who were better prepared than anybody else for this kind of work. If, however, anybody should still hold that it is impossible to expire into a bell jar in the course of natural breathing, I would beg to refer him to a series of experiments to be shortly described. The suspension of the bell jars* came in for a considerable share of attention. When, in 1883, these experiments were commenced, it occurred to me that the best plan was to have the bell jar (weighing between seven and eight pounds and holding 40 litres of air) perfectly balanced by means of counterpoise weights ; the adjiistment was made as follows. After ascertaining that the receiver was balanced at different stages of its course, showing the correct working of the cycloid, it was driven down to on the scale, and then a slight ascending motion was given it by a gentle strain on the balancing cord, say through two or three litres ; on releasing the cord the bell jar had to stop dead ; if there was any tendency to rise or fall, a change was made in the counterpoise of the cycloid. The apparatus was so well constructed that there was no difficulty in obtaining the required result. Thus it was made certain that no error was introduced from acquired speed at every expiration. It was observed, however, that when two bell jars were filled in succession with expired air, which took seven or eight minutes for each, there was often a difference of 5 or 6 per cent, in the volume of air expired within a given time ; while a third bell jar very often, if not usually, gave approximately a mean volume of the two other receivers. Moreover, after being engaged with these experiments for some hours, a certain degree of fatigue was experienced in the muscles of respiration. Finally, the percentage of CO2 in the air expired appeared in every experiment higher than that usually accepted by about 0"5. Under these circumstances it was found necessary to make an alteration in the suspension in the bell jars, and instead of having * For plate showing construction of bell jars see page 26. 84 RESPIRATION OF MAN them exactly balanced in every stage of their course, a slight weight was added to the counterpoise, which after various trials was fixed at 90 grms. ; this weight was but light, though still suflBcient to give the receivers a very slight tendency to rise when left to them- selves. The speed of this upward movement was less than that imparted to the instrument by the expired air, but the lungs had practically no work to do, and at the termination of each expiration the bell jar came to an immediate standstill, the mouth-piece remain- ing in the mouth. The error of volume from difference of pressure was too slight to be taken into account, the reduction of pres- sure being less than one millimetre of water. This arrangement proved very satisfactory ; it relieved entirely the strain on the breathing experienced when the bell jar was used under atmospheric pressure, and as a result, brought down the percentage of CO3 in the air expired to what may be safely looked upon as its correct figure, while at the same time there was a much greater uniformity in the volume of air expired. The figures recorded in this book for volumes of CO3 and found in air expired were all obtained with the counter- poise weighted slightly as described above. Before proceeding to the description of the methods used for the analyses, and instruments employed, I feel it necessary to allude once more to the naso-buccal method of breathing adopted in these inves- tigations, which may be looked upon as the key to every expeinment. If anybody should refuse to beheve that inspiring through the nose and expiring through the mouth can be carried on in the course of natural breathing, or that the person under experiment can make sure of expir- ing no air through the nose, which would be lost for the bell jar, then, of course, he can have no confidence in the work herein described. It is therefore of much importance that such doubts should be re- moved. The objection is often raised that one cannot breathe naturally where the attention is directed to the breathing, and that consequently natural breathing is not compatible with any artificial mode of respiration. In order to demonstrate experimentally the fallacy of this view, 28 BREATHING CHART. 2 miiiutes. Hedvuo^ to hcOf origmaL size-. CCanii C, C. Normal, to ooinpare withfiaeiiinogira.pii cliajrt. n, A AA.3c AA..Norrnal,'OT-th.Piae-aiaogra-pli,a,VLtoiiia,ti.o lorea-thijig - E.B X. BB .TSformal jTispiEing Nose,Ex]Oii-iTig MoTxtlfL. C C &. C' C' . Normal ,a.s B B . with BellJarX^Cliart . West.NewDiail lltli. METHODS OF INVESTIGATION 85 a Marey's pneumograph was used, by means of which a tracing is imparted to smoked paper on a revolving drum by the contractions of the chest acting oa a girdle placed round the thorax. The girdle is so lightly affixed that it opposes practically no obstacle to respiration, while the mind is absolutely unconcerned with the act of breathing; hence the tracing is in reality a record of natural breathing, although it does not show the volumes of air inspired or expired. It is obvious that if the tracing thus obtained, and a corresponding tracing recorded while inspiring through nose and expiring through mouth, are absolutely similar, then there can be no difference between the two forms of respiration. In one of these the attention was unconnected with the respiration, in the other it Vi^as, though in a very slight degree, as habit had rendered the movements very nearly automatic. The following six horizontal tracings, obtained with Marey's pneumograph, show the two forms of breathing. The two tracings A A and A A record ordinary automatic breathing in repose ; b b and B B differ from the above by their being obtained while inspiring through nose and expiring through mouth, c c and o'c' (horizontal) inscribed with the pneumograph are under the same conditions as the last while accompanied with the oblique tracings c c and o'c' obtained simultaneously with the bell-jar recording apparatus. Should the relative volumes of air expired, as shown by the pneumograph, be determined on the charts, by measuring with a pair of compasses the whole length of the tracings, following their curves as far as possible into all their details, it will be seen that, although there may be some slight difference in each pair of experiments, still the mean of each form of tracing from a number of experiments will be the same. The following were the mean measurements of twenty different sets of tracings from the same person, each set including one tracing for absolutely normal breathing, and another for respiration carried on as in these experiments, when air was inspired through the nose and expired through mouth ; it will be observed that the mean lengths of the tracings are practically the same. 86 RESPIRATION OF MAN Mean measurement in millimetres of tracings obtained in 1 min. 22 sees, in normal respiration (Marey's spirograph) . . 401;'7 mm. Tracing obtained inspiring through nose and expiring through mouth 4056 „ Pair of figures giving greatest differences. Normal Inspiring through nose, expiring through mouth Difference 420-5 3800 40-5 ;= 96 per cent. The mean naiiiber of respirations per minute was a little less in the experimental method than in absolutely normal breathing, being 17 in the first and 15 in the second — difference 12 per cent. In these experiments, therefore, the only difference between the two forms of breathing is a mean reduction of 12 per cent, in the number of respirations within a given time. Another person who submitted to similar experiments while having a tracing of his breathing recorded with Marey's pneumograph took the same mean number of respirations per minute. In this case he also collected his air expired in the recording bell jar, thus obtaining a hell jar tracing of his respiration at the same time as a pneumograph tracing. The measurements of the pneumograph tracings were obtained not with compasses, but by fixing pins into the points of greatest curvature and carrying a thread round the pins ; the length of the thread was afterwards determined in millimetres. The lengths of the tracings according to these measurements were as follows : Normal ordinary breathing. 3 observations. Mean length of tracing . . 581 mm. Inspiring nose, expiring mouth, into open air. 3 observations. Mean length of tracing . . 562 mm. Inspiring nose, cxp'ring mouth, into boll jar. 4 observations. Mean length of tracing . . 565 mm. — showing a difference of only 3 "3 per cent, and 2' 7 per cent, between the length of the tracing for ordinary breathing and breathing as per method adopted. Therefore, with two persons under experiment, breathing in repose with and without any attention being given to the respiratory act, it may be said that the mean pulmonary ventilation within a given time METHODS OF INVESTIGATION 87 was the same, notwithstanding slight differences in the experiments taken two by two; it may be concluded, also, that although there is possibly a slight tendency to fewer respirations within a given time, when inspiring through mouth and expiring through nose, still this tendency is not met with in every case. It is therefore concluded that the method of breathing adopted in these experiments is perfectly reliable as illustrating normal respiration. Instruments for analyses. — Tlic instruments for the analyses of the air expired were comparatively few, and gave very satisfactory results. Enough has been said of the apparatus for collecting the air expired. For the determination of COj, considerable time was taken up in the attempt to find a volumetric method, rapid and accurate; but after spending more than a whole year on this one subject of inquiry it Avas given up, as nothing could exceed the accuracy and speed of Pettenkofer's method, which was therefore adopted in every case. Of course the method required special manipulation. With this object I had a cylinder of about 1 litre capacity constructed of thick glass, and closed at each end with a brass cap screwed down upon it. The joints were coated with vaseline so as to make them air-tight ; the caps were supplied with a brass tube and stopcock. On the other hand a wide mouth glass bottle was selected, with a capacity of about 150 c.c, and the mouth of the bottle was fitted with a brass thread into which a brass cap was screwed. The cap was also supplied with a brass tube and tap, through which it it was connected with the cylinder. (See Plate, page 26, Lecture II.) In order to determine the CO3 in the air expired into one of the bell jars, the cylinder (used without the bottle) was joined to the delivery pipe of the bell jar through india-rubber tubing, while the other end of the cylinder was connected with an air-pump. A vacuum was now made in the cylinder, and then the air allowed to rush into it from the bell jar. After repeating the operation about ten times, a 88 RESPIRATION OF MAN weight was placed on the bell jar, and ten or fifteen litres of air were allowed to escape through the cylinder. Then the cylinder was closed and the weight removed from the receiver. The air in the receiver was under atmospheric pressure, but its volume in the cylinder had to be adjusted for temperature, so as to allow of its subsequent reduction, and this was done by immersing completely the cylinder in a cylindrical bath of water kept as nearly as possible at the temperature of the laboratory. The temperature of the water in the bath was carefully noted, and the barometer reading at the time also recorded ; thus there was to be dealt with, a known volume of saturated air at a known temperature and pressure. These data were sufficient for the reduction of the volume of air in the cylinder. After the cylinder had remained in the bath for a few minutes, the tap connecting it with the bell jar was closed and then it was removed and wiped. One hundred c.c. of a solution of barium hydrate of known strength was now introduced into the bottle, which was screwed to the cap of the cylinder. Then the tap was turned so as to open the bottle, and the alkaline solution was allowed to flow into the cylinder. The next process was to shake the instrument so as to obtain the combination of the barium ; after five or ten minutes about 100 c.c. of common air were introduced into the cylinder with a common india-rubber syringe, with the object of exerting a pressure within the cylinder and hastening the combination of the COg. After this, the shaking was resumed for ten minutes or a quarter of an hour, when the combination was complete, and the fluid was poured into a glass-stoppered bottle, there to await the settling of the precipitate. The next morning 25 c.c. of this clear fluid was decanted and the baryta it contained determined by titration with oxalic acid in the usual way. Fourteen experiments were made to test the accuracy of this analytical method. In each experiment two analyses were made from the same stock of air in the bell jar. The results are expressed as METHODS OF INVESTIGATION 89 grammes of OO3 expired per minute. The agreement of the same pair of figures shows the accuracy of the method. Gramme. 0-3905 \ 0-3881/ 0-4581 \ 0-4571/ 0-4228\ 0-4203/ 0-5108\ 0-5087/ 0-4403 ■> 0-4393/ 0-4625 \ 0-4652/ 0-4015\ 0-4007J Found Caebonic Acid as expieed per Minute DifTerence. Per cent. . 0-0011 = 0-30 0-0020 = 0-47 Difference. Per cent. Gramme. . 0-0024 = 061 0-3630\ 0-3641/ . 00010 = 0-22 0-4263\ 0-4243/ . . 0-0015 = 0-35 0-4348^ 0-4345/ . . 0-0021 = 0-41 0-4246 \ 0-4234 j . . 0-0019 = 0-25 0-4011 \ 0-4006/ . . 0-0027 = 0-58 0-4033 \ 0-4046/ . 0-0008 = 0-20 0-3766-1 0-3758/ Mean difiference , , . 0-0013 = 0-0003 = 0-07 0-0012 = 0-28 00005 = 012 00013 = 0-32 . 0-0008 031 per cent. = 0-21 It soon became obvious that the calculation for reductions could be very materially simplified and shortened by making use of a table, showing for every reading of the barometer the reduction of 1000 c.c. of air saturated with moisture. I searched in vain for such a table, which probably exists somewhere, and in despair set to work, with my assistant, to make a table for my own use. The following table was con- Vt (p - f) structed with every care from the usual formula V,, = y^,. /, , — ,>, and showed the reduction of 1000 c.c. of saturated air from 735 to 780 mm. pressure and from 10° to 25° centigrade. 12 90 RESPIRATION OF MAN Table for the Reduction to Dryness, to 0° C, and 760 mm., of 1 Litee of Babo Tem- perature 735. 736. 737. 738. 739. 740. 741. 742. 743. 744. 745. 10 921-3 9226 923 9 925-1 926-4 927-7 928-9 930-2 931-4 932-6 933-9 11 917-3 918-5 919-8 921-1 922-4 923-6 924-8 926-1 927-3 928-5 9298 12 913-2 9144 915-7 917-0 918-3 919-5 920-5 921-8 923-0 924-2 925-5 13 909-1 910-4 911-7 912-9 914-2 915-4 916-7 918-0 919-2 920-4 921-7 14 905-0 9063 907-5 908-7 910-0 911-3 912-6 9139 915-1 916-3 917-6 15 900-9 902-1 903-4 904-6 905-9 907-1 908-4 909-7 910-9 912-1 913-4 16 890-7 897-9 899-2 900-4 9017 902-9 904-2 905-5 906-7 907-9 909-2 17 892-5 893-7 895-0 896 2 897-5 898-7 900-0 901-3 902-5 903-7 1 905-0 18 888-3 889-5 890-8 892-0 893-2 894-5 895-8 897-1 898-3 899-5 900'8 19 884-0 885-2 886-5 887-7 889-0 890-2 891-5 892-7 893=9 8951 896-4 20 879-7 880-9 882-1 883-3 884-6 885-9 887-2 888-4 889-6 890-8 892-1 21 875-4 876-6 877-8 879-0 880-3 881-8 883-0 884-3 885-5 886-7 888-6 22 871-0 872-2 873-4 874-6 875-9 877-1 8783 879-5 880-7 881-9 883-2 23 866-6 867-8 869-0 870-2 871-4 872-6 873-8 875-0 876-2 897-4 878-7 24 862-1 863-3 864-5 865-7 866-9 868-1 869-3 870-6 871-8 873-0 874-3 25 857-5 858-7 859-9 861-1 862-3 863-5 864-7 865-9 867-1 868-3 869-6 IUbo Tem- perature 758. 759. 760. 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 950-5 946-4 942-0 938-1 933-9 929-7 925-4 921-1 916-8 912-5 907-7 903-9 899-2 894-6 890-1 885-5 951-8 947-7 943-3 939-4 935-2 931-0 926-7 922-4 918-1 913-8 908-9 905-2 900-5 895-9 891-4 953-0 948-9 944-4 940-5 936-3 932-0 927-8 923-5 919-2 914-8 910-4 906-2 901-4 896-9 892-3 887-9 761. 954-3 950-2 945-7 941-8 937-6 933-3 929-1 924-7 920-4 916-0 911-6 907-4 902-6 8980 893-4 888-9 762. 763. 955-6 951-5 947-0 943-1 938-9 934-6 930-4 9260 921-7 917-2 912-8 908-6 903-8 899-2 894-6 890-1 764. 956-8 952-7 948-2 944-3 940-1 935-8 931-6 927-2 922-9 918-4 914-0 909-8 905-0 900-4 895-8 891-3 958-0 953-9 949-4 945-5 941-3 937-0 932-8 928-5 924-2 919-7 915-2 911-1 906-3 901-7 897-1 892-6 765. 959-3 955-2 950-7 946-8 942-6 938-2 934-0 929-7 925-4 920-9 916-5 912-3 907-5 902-9 898-3 893-8 766. 960-6 956-5 951-9 9481 943-8 939-5 935-2 930 9 926-6 922-2 917-7 913-5 908-7 904-1 899-5 895-0 767. 961-8 95'7-7 953-1 949-3 945-0 940-7 936-4 932-1 927-8 923-4 918-9 914-7 909-9 905-3 900-7 896-2 768. 963-1 959-0 954-4 950-6 946-3 942-0 937-7 933-4 929-1 924-7 920-2 916-0 911-2 906-6 902-0 897-4 METHODS OF INVESTIGATION 91 Air SATUBA.TBD -WITH HuMIDITY, FEOM 10° TO 25° C, AND 740 TO 780 MM. 746. 747. 748. 749. 750. 751. 752. 753. 754. 755. 756. 757. 935-1 936-4 937-6 938-9 940-4 941-6 942-9 944-2 945-4 946-6 947-9 949-2 931-0 932-3 933-5 934-8 936-3 937-5 938-8 940-1 941-3 942-5 943-8 945-1 926-7 928-0 929-3 930-5 931-8 933-1 934-3 9356 936-8 938-0 939-4 940-7 922-9 924-2 925-4 926-7 928-0 929-2 930-4 931-7 932-9 934-1 935-5 936-8 918-8 920-1 921-3 922-6 923-8 925-0 926-2 927-6 928-8 930-0 931-3 932-6 914-6 915-9 917-1 918-4 919-6 920-8 922-0 923-3 924-5 925-7 927-1 928-4 910-4 911-7 912-9 914 2 915-4 916 6 917-8 919-1 920-3 921-6 922-8 924-1 906-2 907-5 908-7 910-0 911-1 912-3 913-5 914-8 916-0 917-2 918-5 919-8 9020 903-3 904-5 905-8 906-8 9080 909 2 910-5 911-8 913-0 914-2 915-5 897-6 898-9 900-1 901-2 902-5 903-7 904-9 906-2 907-4 908-6 909-9 911-2 893-3 891-6 895-8 897-1 898-1 899-3 9005 901-7 902-9 9041 905-3 906-5 889-2 890 5 891-7 8930 894-0 895-2 896-4 897-7 898-9 900-1 901-3 902-6 884-4 885-7 886-9 888-2 889-0 890-2 891-4 892-9 894-1 895-3 896-6 897-9 879-9 881-2 882-4 883-7 884-7 885-9 887-1 888-4 889-6 890-8 892-0 893-3 875-5 876-8 878-0 879-3 880-1 881-3 882-5 883-8 885-0 886-2 887-5 888-8 870-8 872-1 873-3 874-6 875-7 876-9 878-1 879-3 880-5 881-7 882-9 884-2 769. 770. 964-4 960-3 955-7 951-9 947-6 943-2 938-9 934-6 930-3 925-9 921-4 917-2 912-4 907-8 903-2 898-6 965-7 961-6 957-0 9531 948-8 944-4 940-1 935-8 931-5 927-1 922-6 918-4 913-6 909-0 904-4 899-8 771. 967-0 962-8 958-2 954-3 950-1 945-8 941-4 9371 932-7 928-3 923-8 919-6 914-8 910-2 905-6 900-9 772. 968-3 964-1 959-5 955-6 951-3 947-0 942-6 938 3 9339 929-5 925-0 920-8 9160 911-4 906-8 902-1 773. 969-6 965-4 960-8 956-9 952-6 948-3 943-9 939-6 935-2 930-8 926-3 922-1 917-2 912-6 908-0 903-3 774. 970-8 966-6 962-0 958-1 953-8 949-6 945-2 940-y 936-5 932 927-5 923-3 918-4 913-8 909-2 904-5 775. 972-1 967-9 963-3 959-4 955-1 950-8 946-4 942-1 937-7 933-2 928-8 924-5 919-7 915-1 910-4 905-7 776. 973-3 969-1 964-5 960-6 956-3 952-0 947-6 943-3 938-9 934-4 930-0 925-7 920-9 916-3 911-6 906-9 777. 974-6 970-4 9b'5-8 961-9 957-5 953-2 948-8 944-5 940-1 935-6 931-2 926-9 922-1 917-5 912-8 908-1 778. 779. 975-9 j 971-7 967-1 9632 958-8 954-5 950-1 945-8 941-4 936-9 932-5 928-2 923-4 918-8 914-0 909-3 977-1 972-9 968-3 964-4 960-0 955-7 951-3 947-0 942-6 9381 933-7 929-4 924-6 920-0 915-2 910-5 780. 978-4 974-2 969-6 965-7 961-3 957-0 952-6 948-3 943-9 939-4 935-0 930-7 926-0 921-3 916-5 911-7 92 RESPIRATION OF MAN A large proportion of the figures were determined witli the formula, and then the intermediate values were calculated with the aid of constants. When the table was finished a considerable time was given to the testing of the figures in order to ascertain their accuracy, and this table was only uSed after it had been found to be perfectly correct The present table was published in the ' Phil. Transactions,' 1890, to which has been added the reductions from 735 mm. to 739 mm. A correction has to be introduced for the fractions of millimetres, which are to be multiplied by 1"26, and the result is additive ; while the fractions of temperatures have to be multiplied by 4" 3, and the result is subtractive. The determination of oxygen was efPected in a eudiometer of a somewhat special construction. The hydrogen was prepared in an ordinary WolflF's bottle from zinc and pure sulphuric acid ; the gas being passed first through a strong solution of potash and then through a nearly saturated solution of cupric sulphate. About twelve times the volume of the air-spaces in the generating bottle and washers was allowed to escape before collecting the hydrogen for use, in order to wash out entirely the contained air ; and finally the gas was collected in a receiver of about 1 litre capacity. A sample of the hydrogen obtained by this method, and ex- ploded with atmospheric air, was found to be quite pure and reliable. The collecting vessel is in the form of a glass cylinder, with a neck at the top, bearing a glass stopcock, the whole being adjustable by means of a rack and pinion to any desired depth in a circular glass vessel filled with boiled distilled water, by which means the enclosed gas can be maintained at any desired pressure. The eudiometer proper consists of a glass U tube of about 12-6 mm. in diameter, of which the left limb is made in two pieces, joined to each other with iron fittings and screws; the tube has a glass tap fused on to the lower part of the bend. A three-way tap of iron is sealed on the extremity of one limb by means of which the eudiometer can be placed in connection either with the hydrogen or the external air, or can be shut off" entirely from either of them. The whole is TD 'Flash ' for reqi ' Ma^'izmi-a Ael . djWLg yvazer edi ijT-e-ss'Lcre'. JEUj^eTL- t?.^.- l'tJl£ TUXXy 3^„'^ « "West, Nevjioan pKoto-litk METHODS OF INVESTIGATION 93 supported on a stand at sucli a height as to allow a vessel to be placed nnder the tap to receive the mercury as it flows out. The limb fixed to the iron tap has' two scales engra vied on the glass : the one on the left shows the volume of the tube in cubic centimetres; the one on the right shows the length of the tube in mm. The other limb of the U tube is also supplied with a scale engraved at the back on polished iron giving its length in mm. This scale is moveable, and can be adjusted so that its readings correspond exactly with the other scale engraved on the glass tube. The stand of the instrument is supplied with adjusting screws, and it is easy with the assistance of a spirit level to place it in a vertical position. Having done this, the moveable mm. scale at the back of the right- hand limb is made to correspond exactly to the scale on the other limb; so that if, for instance, the height of the mercury in the one limb while in connection with the external air is shown by the figure 20 (mm.), the mercury in the other limb will also stand at 20 (mm.). With this arrangement whatever the height of the mercury when the gas in the left-hand limb is cut off from the external air, it can always be brought under atmospheric pressure by either adding mer- cury to it or removing some from it, so as to make the heights of the two columns of mercury the same, as indicated by the mm. scales ; in this way any volume can be read off exactly under atmospheric pressure. The closed limb, being surrounded by a water jacket, is independent of external temperatures. The expired air in which the oxygen is to be determined is collected by water displacement direct from the bell jar in a pear-shaped glass flask holding about one litre. This vessel is closed by an india- rubber cork pierced with a hole and securely wired to the rim ; through the cork passes a short glass tube supplied with a stopcock ; this is used for introducing the solution of baryta into the flask. The operation is conducted as follows. A 100-c.c. pipette is filled with solution of barium hydrate containing about 22 grms. to the litre ; this is connected by means of india-rubber tubing with the flask, care being taken that no air is left in the tube. On opening the 94 RESPIRATION OF MAN stopcock, about half the contents of the pipette flow into the flask ; pressure is then exerted upon the fluid in the pipette by means of an india-rubber syringe through the medium of an india-rubber tube. By this means the pipette is nearly emptied into the flask, and then the tap is closed; thus the solution of baryta is mixed with the air to be analysed under a somewhat increased atmospheric pressure. It is now enough to shake the contents of the flask for about ten minutes in order to insure the combination of the whole of the CO3, there being nothing left but nitrogen, oxygen and argon in the air to be analysed. The flask is now placed on a wooden tripod about the same height as the eudiometer ; another similar vessel, filled with water, is sus- pended by a cord carried through a pulley fixed to the ceiling, by which means this vessel is easily raised to any desired height ; the object of this arrangement is to exert a pressure with water on the air to be analysed. The two flasks are now connected by an india- rubber tube filled with water, fixed to the lower opening of each of them, care being taken, before adjusting, to fill the tube of the lower flask beyond the stopcock with water; a simple manipulation being required, into which it is unnecessary to enter. By raising the flask full of water to about three feet above the other one, a pressure of about one tenth of an atmosphere is obtained. This is amply sufiicient for the purposes of the analysis. The analysis is conducted as follows : — First the eudiometer is entirely filled with mercury by means of a funnel placed in the open limb, which is slightly longer than the other, the iron tap being so adjusted as to allow the contained air to escape. "When the eudi- ometer is filled, the mercury escapes from the tap, and while it is flow- ing out this tap is closed, any mercury remaining in the passage of the tap being blown out. In this way the U tube may be looked upon as filled with an unbroken column of mercury containing no trace of air. The next process is to connect the eudiometer by means of a piece of india-rubber tubing of narrow bore with the hydrogen receiver. This is done by slipping one end of the india-rubber tube over the left- METHODS OF INVESTIGATION 95 hand projecting arm of the iron cap, while the other end of the tube is connected with the hydrogen holder. The right-hand tubular pro- jection of the iron cap is closed by a short piece of rubber tubing and pinch-cock, whose object is to receive the nozzle of a glass syringe. The rubber tubing connecting the hydrogen holder -with the eudiometer is now in readiness for washing with hydrogen gas, which is done by depressing the holder till the gas is under a pressure of 2 or 3 inches of water. The tube is then exhausted with a syringe, and maintained collapsed by closing the pinch-cock. The glass tap of the holder is very rapidly opened and closed, when the collapsed tube expands by filling itself with hydrogen. This gas still contains traces of air, which have to be washed out by means of an india- rubber syringe, of a capacity of about 4 oz. ; it is exhausted of air as completely as possible by compi^ession with the band, and while thus compressed is fitted on to the short rubber tube projecting from the cap on the right. The glass stopcock of the holder is now opened, when the india. rubber syringe expands, and the instant it is filled with hydrogen the iron tap is turned through 90°, thus connecting the eudiometer with the store of hydrogen. The mercury is now run out from the lower tap of the eudiometer till about 20 c.c. of hydrogen have entered the instrument; then the hydrogen in the holder is placed under atmospheric pressure bv means of the rack and pinion movement, when of course the hydrogen in the eudiometer is also brought under the same pressure. The tap of the holder and iron tap are then closed in the order given. For further security the mm. scales on each of the limbs of the eudiometer are read, when they oiight to correspond. The volume of hydrogen at atmospheric pressure is then noted. The right-hand arm of the iron cap is now connected, by means of a piece of rubber tubing, with the flask holding the air to be analysed ; and first of all the entire passages connecting the flask and eudiometer have to be rinsed out with some of the air stored for analysis. As this air is under a considerably increased pressure, the rinsing is readily 96 EESPIRATION OF MAN accomplislied by opening the flask and allowing enougb air to escape to tlioroughly wash out the tubes ; during the whole time the water from the upper flask flows into the air flask, so that there is no falling off of the pressure. When suSicient air has passed through the tube, it is closed at the left-hand arm of the iron tap by an india-rubber tube and pinch-cock, or better by an iron tube supplied with a tap ; this was the method in general use. Having rinsed out the tubes with the air stored for analysis, the required volume is admitted into the eudiometer in the following way : — First of all mercury is run out from the instrument by the lower tap till there is a difference of height of about 20 cm. in the two arms of the eudiometer, thus placing the measured volume of hydrogen under a correspondingly reduced pressure. The three-way tap is now opened so as to let in the air under pres- sure, when it rushes into the eudiometer with great force, and the tap is closed before any recoil can take place — a manipulation offering no diflBculty after a very little practice. The volume of air required for analysis is about 30 c.c. ; and if the amount of air taken in at the first operation is insufficient, a further volume can be admitted by repeating the process. At this stage of the analysis, the heights of the two columns are roughly adjusted by letting out mercury, and then the gases in the eudiometer are to be carefully mixed by introducing the nozzle of the india- rubber syringe into the open end of the eudiometer, and driving the column of mercury up and down for about a minute or two, by alternately compressing and releasing the bag with the hand. The two columns are then carefully adjusted by addition or sub- traction of mercury until they read exactly the same on both sides, to a fraction of a mm. The corresponding volume is now read ofi" on the other scale, taking into account fractions of tenths of a c.c. Next is the explosion, effected with a Ruhmkorff coil in the usual way. It may be noticed that the disturbance produced is but very slight. METHODS OF INVESTIGATION 97 After the explosion the columns of mercury are again adjusted for height, and left quiet for a few minutes, when the volume of air left in the tube is read off, and the oxygen calculated in the usual way. It often happens that two persons do not read the instrument in ex- actly the same way, but the final result for each will be found to agree. The instrument takes a long time to describe, though with a little practice very speedy in its working; three determinations of oxygen of the same air are easily obtained in an hour. In the present investigation it has been usual to make three deter- minations of for every experiment, but the results have been found to agree so closely with each other that in the later experiments the determinations were reduced to two in number. The following are test experiments made with atmospheric air : 20-88^ Mean. 20 871 20-90 20-881 20-88 20-91^ 20-91 20-93 20-9i; Mean. 20-91 20-89^ Mean. 20-90 1 20-i 20-1 [)-88r )-9lj 20-89 Pel- cent. COj O N 0-09-1 20-88 i 79-02 found. 99-99 Percent. COj . ., N 0-05 7 gQ.g^j found . 79-02 99-98 Percent. C0„ . N 0-09 7 . 20 89 5 '"°''"'' . 79-02 100-00 Percent. C0„ . N 06-, . 20-91 i ''^""'^ . 7902 99-99 20-91~l Mean. 20-91 1 20-91 20-9lJ The advantages of the method are speed, accuracy, and indepen- dence of external temperature, as the gases are surrounded by water. 13 98 RESPIRATION OF MAN The eudiometer has to be cleaned only on rate occasions, for which purpose it is disconnected at the iron joint, a wooden rod and a fine cloth being used for wiping out the tube inside. Care Should be taken never to introduce an iron rod, as the glass is apt to crack after- wards; it is well, however, to clean the instrument as seldom as possible, in order to avoid the risk of an accident. Influiinob op Volition on Respiration This subject has been treated at full length in Lecture III ; but there are two points which had necessarily to be omitted, as too technical in their character to find any place in the lectures. The first relates to the method adopted for the calculation of the oxygen absorbed. This method requires some consideration, and in order to make the explanation perfectly clear the following diagram may be referred to. B K--- ~^. ^ A Let the line a a represent normal breathing. The curve a b c breathing whilst volition is applied towards any particular object, such as running, carrying a heavy weight, cycling, or swimming. D E is the curve for the after-stage, or breathing immediately after suspension of the act of volition and while returning to the ordinary condition. Now a b o — a o is the excess of CO^ expired under volition over the CO3 expired normally in the same lapse of time. ABODE — AE will be the amount of COj expired in excess of that which would have been expired in the same time in normal breathing; and this excess gives the amount of COg for "work done" owing to the increased labour of the respiratory muscles. It must be borne in mind that this figure includes the whole of the phenomenon, and that the breathing has come back again to the normal at e, consequently any METHODS OF INVESTIGATION 99 excess of CO3 must be owing to " work done." At first sight this increase might be looked upon as due to CO3 given out of the blood, but it cannot be so, as the blood has had time to recover its CO3 before the end of the experiment ; therefore we can now estimate the excess of COj expired under volition, and the total amount of CO3 for work done. If, as must be, the whole of the "work done" takes place during the volition period, then by subtracting the figure for " work done " from the total excess given out while breathing under volition, the difference will necessarily correspond to the excess of COg dis- placed from the blood by the tidal air. There is another point to be taken into consideration — that is the COo emitted in the after stage. It must be clearly understood that in the second or after-stage, a certain amount of CO3 must be retained in the blood in order to compensate for that which has been displaced (beyond the normal) in the first stage. This diminution of CO3 expired will clearly lessen the volume of air expired, thus increasing the difference between the volumes of air inspired and expired, and showing apparently an increase of absorbed. But this is only an apparent increase, the true figure for absorbed being obtained by subtracting from the apparent figure the volume of CO3 emitted from the blood — that is the excess of a b over A c diminished by the CO2 for work done. The argument with reference to the after-stage may be briefly stated as follows : Total volume of air inspired (calculated from the nitrogen expired) less total volume of air expired = apparent oxygen absorbed in after-stage. Apparent absorbed— (excess CO3 over normal in violition stage — work done) = true absorbed in after-stage. 100 RESPIRATION OF MAN The following experiment, with the calculations in full, illustrates the present mode of reasoning. ABC (volition), CO2 . c D E (after-stage), C0„ ABODE, total A B (normal), OOj . Difference = Worh done in Volition Stage 492 c.c. in 2 min . 2 sec. 610 )i 3 »j 33 SJ .^- 1102 )» 5 ,, 35 9} 984 » 5 >j 35 Si 118, ABC (volition), CO2 . . . =: A c (normal), COj . . . = Difference = OOj from blood and work done = Work done , . . = Difference = COj (in excess) from blood . = 492 c.c. in 2 min. 2 sec. 351 jj 1 >j 141 118 „ 23 c.c. Total volume of air inspired (volition stage) ). . ,1 » expired „ „ Difference = Apparent oxygen absorbed OO2 excess from blood True O. absorbed 13281 c.c. in 2 min. 2 sec. 13205 „ J3 3> 76 c.c. 23 „ 99 c.c. in 2 min. 2 sec. Oxygen absorbed per minute under volition = 48'7 c.c. „ :, „ normal . — 33'1 „ J, „ „ in excess for volition = 15'6 c.c. After-stage. Total volume of air inspired „ expired Difference = Apparent oxygen absorbed COj (excess) from blood re- absorbed Difference = True oxygen absorbed 14455 c.c. in 3 min. 33 sec. 14308 „ 107 „ 23 84 c.c. = 23-7 c.c. per min. METHODS OF INVESTIGATION 101 The results of these experiments are expressed in the following tables : Oxygen absorbed pee Minute, the Will being applied without Response to Running oe Rowing Normal respiration in repose. Bespiratiou under voli- tion. S-i o 1-! > Found in after-stage. Mean of vo- lition and alter-Btage (from total figures). Volumeofair expired normal. Volumeofair expired under volition. Time after last meal. C.c. C.c. C.c. C.c. C.c. Litres. Litres. Hr. M!n. -, W. M. . 31-9 50 4 ]8-5 24-7 33-4 3-767 6-760 2 30. Lunch. R.B.F.431 43-2 01 38-2 39-4 4-039 4-550 2 30. Breakfast. „ 49-9 59-9 100 40-2 44-5 3-903 5-887 2 35. Under the in- „ 43-9 51-6 7-7 38-6 42-4 4051 5-143 1 45. 1 flence of „ 43-6 56-2 12-6 37-2 41-5 3-863 5-633 2 10. 99 food. Means . 425 52-3 9-8 351 40-2 3-925 5-595 2 18. 25-4 90-2 64-8 24-4 406 3-296 5-091 4 0. Breakfast.^ 35-8 84-6 48-8 31-8 40-9 3-383 5-891 4 5. 36-9' 95-7 58-8 23-1 37-7 3192 5-399 3 23. 53-2 86-0 32-8 13-5 31-2 3-134 5-999 4 80. 59-7| 63-3 36 52-4 55-7 2-816 5-343 3 45. > Fasting. 40-6 78-2 37-6 34-4 45-6 3-550 5-120 3 20. 32-6 So 9 53-3 30-7 43-6 3-337 5-776 4 10. ■■ 1 Means . 40-6 83-4 42-8 300 42-2 3-248 5-517 3 53. Oxygen absorbed pee Minute Volition for lifting a weight, luithout response Normal. Volition for lifting weight. Excess for volition. Means for volition and alter-stage (total figs.). Volume of air expired normal. Volume of air expired under volition. Time after last mea . C.c. W. M. . 331 R. B. F. 48-6 „ 47-2 Co. 48-7 62-4 83-0 C.c. 15-6 13-8 35-8 C.c. 32-8 44-2 42-5 Litres. 3-963 3-826 3-675 Litres. 6-503 5-938 4-740 Hrs. Mins. 2 30 after lunch. -) 2 30 after breakfast. 2 30 Under food. Mean 43-0 64-7 21-7 39-8 3-821 5-727 2 30 „ „ J W. M. Volition for running and for cycling without response Running. 53-0 91-0 Cycling. 38-0 52-0 89-4 37-4 63-3 53-8 3-744 3-521 5-970 5-747 4 10 after breakfast. 3 50 „ [Fasting. ^ ., 102 RESPIRATION OF MAN Oxygen absorbed pek Minute, Volition applied to Fokced Bueathing with Checked Response* Normal. Under volition. Excess for volition. Means for volition and after-stage (total figs.). Volume of air expired normal. Volume of air expired under volition. Time after lust meal. C.c. W. M. . 40-5 42-5 R.B.F. 67-9 470 53-8 57-0 C.c. 88-5 52-0 88-8 67-9 97-0 58-5 C.c. 4S-0 9-5 20-9 20-9 43-2 1-5 C.c. 44-8 46-8 59-4 38-6 57-6 43 3 Litres. 4-246 4975 4-16i 3-929 4-015 3-882 Litres. 6-043 6-784 4-872 4-644 5-018 4-520 Hrs. Mins. 3 after lunch. 2 40 „ „ 3 after breakfast. 2 30 „ 3 „ 11 2 30 „ Mean 51-4 75-4 23-9 48-4 4-202 5313 2 47. * The duration of the " after-stage," in all the volition experiments without response, varied from three to seven minutes ; direct experiments showed that in three minutes after the volition stage, the CO2 expired and O absorbed had practically returned to the normal. The CO2 had perfectly recovered, the O absorbed still exhibited a slight variation, though not sufficient to vitiate the results. This is shown in the following table, in which the value for OO2 and O are expressed in cubic centimetres per minute. Normal. Duration of first after-stage. Second after-stage. CO2 absorbed. CO2 absorbed. 173-2 194-2 213-7 205-7 42-5 55-6 37-5 49-2 3 mins. sees. 3 „ „ 3 „ 15 „ 3 „ „ 175-8 200-3 212-2 193-9 50-1 48-2 53-2 48-8 Means . 1967 46-2 195-5 50-1 183-5 179-6 179-3 170-2 64-3 58-1 630 61-0 4 mins. 59 sees. 5 „ „ 5 „ „ 5 „ „ 175-0 180-3 180-6 175-9 69-9 61-3 590 66-8 Means . 178-1 61-6 177-9 64-2 192-8 181-2 171-5 193-7 54-2 56-3 50-5 36-8 6 mins. sees. 5 „ „ 6 „ „ 6 „ „ 184-8 177-5 175-7 186-7 51-9 55-7 53-6 42-5 Means . 184-8 49-4 181-2 50-9 METHODS OF INVESTIGATION 103 Oxygen absorbed pee Minute in Forced Breathing, Volition naturally directed to forced breathing Normal respiration. Forced respira- tion. Excess for volition. Volume of air expired normal. Volume of air expired under volition. Time after last meal. C.c. C.c. C.c. Litres. Litres. Hr. Min. R. F. . . . . . . 44-7 81-1 36-4 4-399 8-433 1 45. Breakfast. „ . . . . . . 52-9 80-3 27-4 4-051 5-309 2 15. . . . . 73-5 85-0 11-5 4-467 5-648 1 1 40. W. M. . . . . . . 36-8 41-5 4-7 4-457 11-058 2 30. Lunch. . . . 340 47-6 13-6 4-051 6-413 1 2 45. R. F. . . . . . . 57-5 73-2 15-7 4-713 6-102 : 2 0. Breakfast. Means . . . . . . 49-9 68-]. 18 2 4-354 7-144 ^ 2 9. A few words will suffice for the consideration of these tables. The first shows a very marked difference between the excess of oxygen absorbed for volition while under the influence of food and while fasting, the figures being 9'8 c.c. at a mean time of two hours and eighteen minutes after the last meal ; and 42*8 c.c. at a mean time of three hours fifty-three minutes after a meal. The mean oxygen absorbed for volition and after stage is calculated from the total volumes oxygen absorbed in the volition and after stage during the whole experiment, and not from the volumes obtained per minute in each of the two stages ; this was necessary as volition was applied usually for two minutes, while the after stage lasted generally from five to seven minutes. It should be remembered that the excess of " absorbed " as determined in these experiments is taken from the air inspired only, and not from the present in the body. This would seem to explain the fact that when fasting, the effect is very much more marked than under the influence of food. In the fasting experiments there would be less in the tissues to supply the requirements of volition, and consequently more would be taken from the air; while, on the other hand, under the full influence of a meal, the tissues contain a larger store of oxygen, which might serve towards the requirements of volition, thus reducing the taken from the atmosphere. 104 RESPIRATION OF MAN In the first table, the mean oxygen absorbed under the influence of food for " volition and after stage " is very like the normal, being 40*2 c.c (mean figure) as compared with 42-5 c.c. normal ; the corresponding figures fasting being 42"2 c.c. and 40-6 c.c. This certainly shows that the lessened absorption of oxygen in the after stage compensates the excessive absorption under volition, and the same phenomenon is observed throughout the whole of this inquiry, including twenty -three experiments. The mean of the twenty- three experiments being 45-2 c.c. per minute for normal absorbed, and 44-5 c.c. per minute for mean of volition and after stage, these figures agreeing, therefore, in a remarkable way. This occurrence of a decreased amount of oxygen absorbed in the after-stage, compen- sating for the increased absorption of oxygen under the influence of volition, certainly appears to show that the absorption of oxygen under the strain of volition is unattended by any chemical action ; it seems as if the motor centre of tlie brain was temporarily charged with oxygen which gave it power to perform its function, this oxygen being, on the release of volition, carried away back again into the circulation. It will be seen in the first table that under volition, the increase in the volume of air breathed when fasting (70 per cent.) is much greater than the corresponding increase \xnder the influence of food (39-5 per cent.) ; showing an excess of oxygen absorbed fasting over the oxygon absorbed under the direct influence of food, as an increased demand for oxygen would necessarily bring about the desire for an increased amount of tidal air through the pulmonary organs. In the fourth table, where volition was applied towards forced breathing, and consequently attended with response, we again find a marked increase in the absorption of oxygen — being 18"2 c.c. in excess of 49"9 c.c. absorbed in normal respiration. In these last experiments the mean of the oxygen absorbed under volition and in after-stage cannot compare with the normal oxygen absorbed, because the response to the volition introduces a complication which appears very difficult to estimate ; for that reason the column lieaded " Means of METHODS OF INYESTTGATION 105 volition and after-stage " has not been introduced in the table. lu all probability, however, if this circumstance could be taken into account, the same law would be found to exist with reference to the oxygen absorbed under volition, as when the "will" is exercised without being attended with response. These experiments, of course, only concern " oxygen absorbed," and leave aside completely any reference to the influence of volition on the production of CO2. The respiratory movements of the chest are limited to a certain order of muscles, and may be looked upon as automatic ; but if an effort of volition be brought to bear on this ordinary automatic respiration with the object of increasing its depth, increased con- traction of the respiratory muscles will follow, although no other muscles may be brought into use ; this can hardly be called " forced breathing." On the occasion of laboured or forced breathing the muscles con- cerned are the same as those applied to ordinary breathing with the addition of others which, from their position, may contribute to an in- creased expansion of the chest, as clearly stated in Michael Foster's ' Text-book of Physiology,' whose words are (p. 226) with reference to laboured breathing : — " In fact every muscle which by its contrac- tion may either elevate the ribs or contribute to the fixed support of muscles which do elevate the ribs, such as the trapezius, elevator anguli scapuli and rhomboidal, by fixing the scapula, may in the expiratory efforts which accompany dyspnoea be brought into play." If a person should be sitting still in an armchair in readiness to take a tracing of his expired air, and then apply his attention to his breathing with the object of increasing the depth of his respiration, though short of forced breathing,* then the record obtained on the <5hart will not be that of forced breathing, but the line rises speedily * This is not the same experiment as that described in Lecture III, in which volition was applied towards increased or forced breathing, while at the same time the response was checked. In that experiment, however, the tracing obtained exhibited somewhat the same characters as on the present occasion. 14 106 RESPIRATION OP MAN beyond the normal, and if after a minute or two the effort of the will should be suspended, the tracing will show no pause, or state of apnoea, but continue rising for a short time and then return gradually parallel with the normal ; this is seen distinctly in the chart facing page 46, in which the air expired varies in one and a half minutes from 11 to 16*16 litres. When, however, the volume of air inspired has reached a certain limit, then the tracing shows that the respira- tion has become what is called forced or laboured. This is obvious from the pause which occurs on the release of the voluntary act. Thus it is, that if a person should breathe deeper than usual while at rest, short of forced breathing, having his volition or attention directed to his respiration, on the release of the voluntary act, no apnoea follows; but by increasing the depth of the breathing beyond a certain point respiration passes into forced breathing, its graphic record indicating the pause of apnoea. This difference in the course of the tracing is apparently owing to the new set of muscles which come into play when respiration is forced. So far volition has been exercised towards carrying a weight, running, rowing, and forced breathing. In other experiments it was applied to the rapid gyration of an arm. This was done while sitting in a chair, the arm being whirled round and round. A rapid rise of the expiratory tracing was observed on the chart, and on arresting the movement the pause was clearly seen, and then the tracing again rose to return parallel with normal (see chart). If the attention or volition was brought to bear strongly on the gyrating movement, the pause following on the arrest of the gyration was deeper and lasted longer than in the absence of the effort of volition. In one experiment the author remained twenty-one seconds, and Mr. Floris fifteen seconds, without breathing. This stoppage of the respiration is quite involuntary, and produces no feeling of dis- comfort. After it has lasted a few seconds a sudden and deep inspiration follows, equally involuntary, and by degrees respiration returns to the normal condition. Should the volition be exerted towards any other form of muscular exercise, instead of that carried on at the time, 18 'es, BREATHING CHART. BediLCed^ to hcdf original svzW. mtes. 4 raiflulei. 1 ■ ^ * Utrei ni rt 30 =) 2» R y D 38 ^ r^ 81 n / ?({ 5 / ?5 4 X ?4 » y 78 2 / 22 1 ?7 / ?0 » J 1» R r in •3 y n R r^ 1(i ,<> r' 15 4 r^ 14 R l« ' ^ ia / ^^ 12 1 y V"^^ 11 J / 10 n / jj 9 A J ^ 8 T 1 1 f; J 6 5 / y s 1- r r^ ^. 3 r y^ 2 ^ ? J /' 1 \ y' , ^ J ^B /k = Li tr««. — » * tlS B.B.- -— -^ — ♦-— i J.,...^. ...,._... -Jj-5^j;^1 D AA. Normal. B C. Gyrating Arm, CD. After Stage. "Vfest.NewrDan litB. 34; J-OS, Imii lute. BREATHin 2 mix G CHART. Rjuiixct^to lialf ori^i;n.aL svze. Lutes. SmixLutes. 4 minutes. /**!"/" ' »1 /-' xV 30 y^ ?ft y ?8 J y ?1 / G ?R ?5 r^ y^ ?4 ^ «3 ^ / j^ 22 ^ y^ y 21 I ^^-^--^ / , ^ ?,n j y _y ifl / / / 18 / r-^ 17 r r / ie r // 15 r' A, H f ^j^J 13 1 ^f ^ ri 12 r J I 11 r f r 10 J J 1^ y ft J f r' / a J 1 J / 7 k j I y" 6 /^ 5 \ J / * r 1 y 3 = r J y^ 2 ; J f /^ 1 = IE B c£^ ^ ^ J ~ . ' . ^ 1 i :^ 3 = «■ -■-+ — — 4' 'i- »16 S.B. -♦ -••"" Xitre«.^ lii^ea» AA. Normal. m^ a cv B,C .GyrfiLtmg armyoli-tLOii directed. towa.rds respiration. CD, Alter bta.ge. E Y . Gyrating arm yolition for cycling . F. G .After S tag e H.I .Gyrating armyolition towards gyration. I.K.After Stage . "Wesl Newraatn-lith, 36 till res, Imii nule. BREATHIl 2 rni] ^G CHART. autes. Bcduced. to half original s3.e. SmiTniinii, 4 minutes. 1 Iiitreii 31 in 30 n 29 R E 28 '1 27 a 26 (5 - y^ ?5 M. j^ ?4. 'A D ^ 23 2 / 22 !1 r 21 !0 J ?n » _r in 8 y 18 1 r^- n ft j-> 1f> R , J 15 4 / 14 a ^ 13 8 / 1? 11 J^ Aj 11 c ^A^ ^ 10 » / _^ q B _^ R 7 7 6 8 5 1^ * 4 » f ^ T ' 2 f ^ ? = 1 J y^ T = IB .£^ • " Lit pes. ■•- f '""^"" * -iGs;;;^ AA.]N"or.ma.L^ BC. Gyrating arm .volition, exerted "t.rongly towa.i-lo gyratio-p u volition dropped' DE. After Sta.ge. WesOTewma-Ti It i^-^ CD. 36 BREATHING CHART. 2 nuimtes. Hei^zicciL to TiolsC origvn^ svx^. 3 minutes. .r-. 4 ininutes Xitrea, AA-TSTormal . BC.Gyratnag srra-'mxh. attention dxrected towards. resToiration. CD _ ,, voHtioii(or a.t-ten.tioiL) dropped. DE, After Stage. We s t ,Ne wmanJitii . Litr 31 2B BREATHING CHART. BedaCBcL to half crigiiwd- sine.. D ami autes. SmimiteiL 4 minutes. /^G liitrei 31 7^ ap / 29 / 28 / 27 / RR r lis f ?4 J D ?a j ?? 1 ?i / ?n T7 ^ in i* 18 / n / , y ift J r* -r / i» J 14 f / 13 y y 1?! / y A, 11 y f / 10 / y / ft / _r y 8 / ' / T / / / fi / / / ,1 / / y 4 / / y 3 ^ / / / ? ^ y / / 1 = /e ^ ^A. n^ rtpoa. "^'itp«»."* AA,]Sroiraaa.l. B-CVoTitLozL forlocomotiorL limuruLtes . CD .After Stage. E F, Stepping 68 tunes per miTiute with Volition specially, directed towards running . F.G. After Stage. ■ • WestNewma-n Hth. METHODS OF INVESTIGATION 107 such as riding a bicycle, the same pause will be observed on the cessation of the exercise and effort of volition (see chart). It was remarkable that if while gyrating an arm the attention or volition, instead of being directed to the movement of the arm was fixed upon the respiration itself, then on suspending the gyration, no pause whatever, and therefore no apnoea, was recorded. It was con- sequently very obvious that after a rapid whirling of the arm the apnoea was entirely due to the suspension of the volition bearing on the movement. If while the arm was being gyrated under an effort of volition, the attention or volition was withdrawn, and the gyration continued under unconscious volition, a distinct pause appeared on the chart, and then the tracing again rose and continued much the same as before (see chart). In this instance the unexpected phenomenon was witnessed of a somewhat violent exercise while respiration had nearly come to a standstill, and without producing the slightest sensation of distress. Should under similar circumstances the attention be directed to respiration instead of gyration, the pause is absent, as shown in the accompanying chart. Again, when the arm was gyrated under the influence of forced volition, and then arrested in its movement while the effort of the will was continued towards the gyration, then no pause or apnoea appeared on the chart. It may be asked, " Why was there no apnoea produced when after walking exercise the person sat down ? " The answer is clearly that walking requires such a slight effort of volition that it is practically unconscious and its suspension is unnoticed. The proof of this view is the fact that if volition is brought to bear on the act while walking and then suspended on sitting down, the pause or apnoea is at once evident. (See tracing r f and f G on chart). On looking back upon the experiments quoted above, dealing with the influence of volition on respiration, we observe the following phenomena : I, Yolition towards some form of muscular exercise without 108 RESPIRATION OF MAN. response and return to mental repose. — Steep ascent of tracing and pause in after-stage, followed with more or less increase of the steep- ness of the line l)efore returning to normal. II. Exercise under ordinary brain stimulus, such as walking, and return to state of rest. — Steep ascent of tracing continued in state of rest (no pause) and gradually returning to normal. III. Exercise under excessive brain stimulus (volition) and then return to mental rest; exercise continued. — Steep ascent of tracing, then on releasing volition (exercise continued), pause,, followed by a considerable rise of the tracing, returning gradually to the original inclination under exercise. IV. Exercise under effort of volition and then return to physical rest, although the act of volition is continued (gyrating arm).' — Steep ascent of the tracing, but on return to physical rest, no pause indicative of apnoea. V. Increased breathing under influence of volition, or attention directed towards breathing, followed by mental repose. — Steep ascent of tracing, without pause in the after-stage, and returning quickly to normal ; except when depth of breathing is carried beyond a certain limit, in which case the pause oi forced breathing appears. VI. Forced or laborious breathing under ordinary brain stimulus. — Steep ascent of tracing, followed by a pause, then a slight rise beyond normal and gradual return to normal. Breathing Air in Closed Vessels When air is breathed from and into a closed vessel, the COg as it accumulates in the vessel interferes with the emission of CO2 from the blood circulating through the lungs, so that a certain proportion of the gas, which under ordinary circumstances would be expired, remains in the body. The instant fresh air is inhaled there is a rush of this retained CO2 into the pure tidal air, and it is given out. It was interesting to determine the time required for the emission of this OOj, and experiments^ were made with this object in view. Litres, 1 TnimitR . 2 tniputRBi 3 miiiutHH, 4j 31 30 28 28 27 2fi 2S 24 23 22 21 20 ■ 19 18 n 16 / 15 y 14 13 r^ 12 / 11 y 10 f 9 _r 8 f -i 1 J 6 f^ 5 ____ .,_ J 4 / 1 3 ^wwwwwwv P-A-A-A fl-A-A A ft A- -A- »-A-» / 2 wwwvyvww ij 1 irvvvvvYVVw mwwwm mmmmm N0W/WW O AA.Normal. BB^ReToreatimig 6 litres of At. Air for 2 mm. B.C. After Staq e R-RReTDi-eathmg 18 litr-e.s of At. Air. G CHART. Saainute. _G_miauteg, Iie 1» l?l / ^ 12 11 r / n 10 / r^ A^ 10 9 r* ^ _X^ 9 8 1 y R ^ r ^^ y 1 a J ^ / 6 5 1 L _____ __ _ .._/• X ^ a 4 1 y y^^ 4 3 c y' y 3 = 2 y^ A y ? : 1 / y 1 = B^ n = Lii re«. '15 Soo.-* * ' ■^itee..'* > AA.NonxLal.inspirnag aim o spTaer-xc air. BB , ISTormal m spiring 73 Oxyg en 2c% an?. CD . Forced (2 litres v.- 51 expira,ti.oii) ixispiring Vb Ckygen & % air. DE After Stage West.Uevnnai] liUl... le. BREATHING CHART. 2 mimAtest 3ntmutes. ir 4 minu teg. Litres, AA, Normal. a; A, NorTnal for HIK. B C. Ordinary Torea-thin^ H I, Ordinary "breathmi ♦ 15 See.— liiteeiV''* with 2>2>% Hydrogen, CD. After Stage, gmth 50/^ Hydrogen, IK. After Stage. "West '^llewniaii litli- METHODS OF INVESTIGATION 115 resuming tlie direction parallel with normal breathing. (See chart facing p. 113.) It may happen, however, that if the breathiiig be forced to such an extent that two litres or more of air are taken in per respiration, instead of only one litre as in the former case, then after a minute, the reaction or after- stage is not the same as that of breathing under exercise, and will show the pause and gradual return to normal met with invariably in forced breathing with pure atmo- spheric air. (See chart.) Therefore the tracing obtained with moderate forced breathing under ordinary brain stimulus lost its pause in the after-stage because of the oxygen gas in excess in the air breathed ; a circumstance which might find an explanation in the necessity of the body to rid itself of an abnormal amount of oxygen, and certainly showing that the paiise is not due to an excess of oxygen in the body. Air mixed with Hydeogen Experiments were made by inspiring a mixture in the proportion of 1 part hydrogen and 2 pai'ts air, and also when in equal volumes. The effect produced from the inspiration of these mixtures was in no way unpleasant, and there was no sensation of discomfort. The tracings obtained showed that the volume of air expired while breathing H was increased, which might have been expected ; and on suddenly substituting the respiration of atmospheric air for that of hydrogen the tracing was continued somewhat steeper than for ordinary breathing, and then returned to normal. The object of the excess of air inspired in the after-stage is clearly to replace the oxygen wanting, in consequence of its having been breathed in deficient quantities. If the mixture of air and hydrogen be prepared in the proportion of one third hydrogen to two thirds air, and inhaled for one minute when breathing forcibly, followed by the normal respiration of pure air in the after-stage, then a pause will be observed, and afterwards another increase of pulmo- nary ventilation before the return to normal. This being apparently an effect of " volition." 116 RESPIRATION OF MAN Inspiring Aie and COg. Mixtures of 3 and 4'5 per cent. CO2 and atmospheric air were inspired for one minute, when the tracing was decidedly steeper than normal ; then ordinary air was breathed, and the tracing continued in the same direction, becoming gradually parallel with normal. It was obvious from the steepness of the line, and the time it took to retui'n to normal, that the increased ventilation was necessary not to supply oxygen but to eliminate the excess CO2 which had accumulated in the blood. If we compare the effects of hydrogen and CO3, it will be observed that with such proportions as 3 per cent, of CO3 and 30 per cent, of hydrogen, while breathing is continued for one or two minutes, the effects produced on the chart are much the same, but after the prolonged breathing of CO2 for two and a half minutes the steepness of the line continues for a longer time than with hydrogen, this being due to the increased retention of CO3 in the blood. If air containing 4'5 per cent. CO3 be inspired for one minute, the volume expired is greatly increased — in the present instance it amounts to no less than 15 litres ; the after-stage continues almost as steep to the top of the chart. (See chart.) This graphic method of inquiry can, so far, be looked upon as an attempt to show by physical methods the action of gases on human respiration ; and might probably, if developed, become a means of attaining many further results. PRINTED BY ADLAED AND SON, BAETHOLOMBW CLOSE, B.C., AND 20, HANOVER SQUARE, W. l-i BREATHING CHART. 2 minutes. I?ed2Mceci -to JtaJjf or-igiTuxh •size. Xitres^ AA. Normal. BC. Inspiring 3% GQ^frecordtegmsaDfiimiiute after firstmspiration), CD. After Stage. ■»Vert,Ue>™,=i.iith. EF. Inspiring 3% CO^(record "begins Ismm. after first inspiration), F&. After Stage, 21 O Irniu au». BREATHIB 3nux rC CHART. lute*. .„ B^jdujced, to JuaJf arigvnah svz&. 31 . y-D LiireB 31 30 / Vif\ m / 29 3ft \ ?ft 21 f ?7 3fi / ?6 DA / rf> 714 / ?4 2H 23 n / f,f, 21 J ^ f^ sn / / ?,0 l» f / i» 1ft ( 18 17 \ y 17 1ft f / IR lA rf J / If) 14 *^ / 14 13 / 13 1» y 15! 11 /^ 11 10 t / 10 9 / » s / 8 7 1 / 6 5 4 3 2 1 /' 5 / 4 ■V — ^ 3 = T — ^ 2 ^ 1 = n = i y ■ ff^ A .....4 — -. i. -i- — ■ -4- J g-.----j [^-—--4- i ■:-■ llBS.«.— - Xitrei. Litras, AA. Ncrraal. B -0 , Inspir-ing air conteimu^; 4s5%C0 for one minute. CD.After Stage sfecmiBgiio sign of recover-y. 'W«0ti'N«winaii liliL