also in that collected from country districts. He then applied himself to the measurement of organic substances in air, by so simple and ready a test, that it is only surprising it was not discovered before. It was by the decomposition of per-manganate of potash by air; the test lying in the amount required for that decomposition. Among the North Lancashire hills, noted for their purity, it took 1914 cubic inches to decompose a given quantity of per-manganate; in many apparently fresh and quite inodorous, but among the poorer parts of Manchester, it took only 87 cubic inches, or as 1 to 22, to decompose the same quantity. Thus, there is 22 times as much organic matter in Manchester as on the pure hills. In a house, by no means of the worst kind, though in a close and poor district, the back part was compared with the interior. The number at the back was 87, but in the interior it rose to 174; thus showing a far greater amount of impurity in the open air-owing to the habit of accumulating refuse matter than was discernible in the interior of an ordinary poor house, where, though the people were not notably unclean, they were by no means notably the reverse. The front of this house looked on to an open space: here the numbers rose up at once to 700, 2 less pure than the hills. A third-class railway carriage, with both windows down and quite filled, showed the same result as the close court. A bed-room, looking into a yard, but in a better district, stood at night at 696; in the morning, after one person had slept in it, it was lowered one-eigth. The room was a moderate-sized bed-room, 10 feet 10 inches by 11 feet 4 inches, and 9 feet 6 inches high. The fronts of all houses were always one-eigth or one-ninth more pure than the backs; and once, when a drain was stopped up, the instrument registered the atmosphere as nine times more impure than before. When Boussingault tested the air of Paris, he found in it 0.0002 to 0.0008 per cent. of hydrogen, existing partly free and partly as sulphuretted hydrogen and marsh gas; and air from a pestilential district in South America, tested also by him, showed 0.0017 per cent. After drainage, the proportion fell to 0.0004 per cent. One-thousandth part of sulphuretted hydrogen will kill birds, according to Dupuytren, and an air composed ofOxygen Azote 13.79 81.21 2.01 Carbonic acid was fatal to certain men, though breathed for only a few moments. This was the composition of the air in a Paris sewer. So that we can understand how even a trifling excess of sulphuretted hydrogen must be of infinite damage to the health, when a greater excess can cause death on the instant; and we can also understand the deadly mischief wrought by those substances which produce it. Dr. Smith has made another discovery of the effects of the vitiated atmosphere in towns, namely, its action on the blood. He can distinguish between town and country air, even from so small a quantity as a cubic inch, by the effect wrought on the blood, which becomes red more rapidly by, and with a smaller quantity of, the air of dense and manufacturing cities, than by that of pure country places. Dr. Smith says, that it is the acidity of town air which causes this more rapid oxidation, consequently a more feverish circulation,-consequently, again, a greater wear and tear of life, and a premature old age, an abnormal development of the nervous, and coincident depreciation of the fibrous and muscular system. More than food or clothing, more than ignorance or gin,-in fact, the first cause of almost all the wretchedness, and dis ease, and demoralization of the low-town populations depends on the air they breathe; and with wholesome, exhilarating atmospheric influences about them, we may be very sure that half the misery and crime which now sadden and debase our cities would be done away with. It is all the difference between breathing health and breathing poison, when we take into our lungs pure or impure air. But, to go back to the acidity of the air of towns, and the red blood resulting. This acidity Dr. Angus Smith shows to be caused by sulphurous acid, as well as by carbonic acid; and the sulphurous acid comes from the combustion of the sulphur of coals. He analyzed seventeen specimens of coal, and found them to contain, on an average, one per cent. each of sulphur. The air of Manchester is sufficiently acid to redden litmus-paper in less than half-an-hour-generally in about a quarter of an hour; and the rain passing through such an atmosphere is converted into positive acid itself, so far as the testpaper is concerned-a drop falling on a blue piece making it red instantly. "In the course of a year, about one thousand tons of vitriol fall on the sixteen square miles which may be said to constitute Manchester." The rain-water is most acid where the smoky chimneys are most numerous and active, and always preserves a strict average same as on the lawn before mentioned, and connexion between its own condition and among the odoriferous garden plants. Growthe number of tons of coal vapourized into ing plants, and especially odoriferous ones, sulphur in the air. But with all the evils are supposed to sensibly affect the instruand inconveniences of this excess, sulphur ment; but how far, or whether, indeed, at has also its good uses and its favourable all, are points on which the inventor has features. Sulphur is a purifier, one of the not yet fully satisfied himself. But should most potent we have, and of time-honoured it prove to be so-and all that we know of usage-ever since Ulysses purified his palace the odoriferous principle of plants seems to from the blood of the slain lovers, by burn- favour that supposition,-here again would ing brimstone. Sulphur is held as a spe- be an instance of the multiplied forces of cific against the oidium, it is constantly Nature, and the infinite interchange and inused as a fumigating agent in close atmo- termingling, so to speak, of her laws. spheres, and helps to preserve light wines Granting that there is actual organic matter while in the wood. It is more than pro- thrown off by plants, in the shape of perbable, then-almost certain-that this ex- fume, pollen (we know that this, at least, is cess of sulphur, while hurtful on the one thrown off in large quantities into the air), side, is useful on the other; and that Man- or other matters, though it may be indichester and other densely-populated manu-cated by a chemical test, in the same manner facturing towns are preserved from certain as positive putrefactive substances would be forms of putrefactive diseases, whilst ex- indicated, yet that is no proof that it is hurtposed to the organic mischiefs lying in an ful to man. Experience, as well as other over-stimulated condition of the blood, and chemical experiments and demonstrations, an over-active development of the brain and show us that no human life can develope nervous system consequent thereon. into full activity, or even into the perfect Manganates have been employed by Dr. possession of all its capabilities, without the Smith to determine also the amount of car- neighbourhood of vegetation. By one of bonic acid in the air. 66 'Manganates, which those beautiful balances, those compensatare green salts, are changed into per-man- ing actions, which keep the whole universe ganates by carbonic acid, or bi-carbonates, in harmony and order, the vegetable world so readily, as to be suited for metrically absorbs the poisonous gas which human testing both air and water. The carbonic lungs give out, and give out that vital gas, acid of the air so rapidly changes the man- without which man would soon perish miseganate into the per-manganate, and the rably. Plants are, in reality, atmospheric amount of acid taken up is so uniform, that scavengers, clearing off deleterious gases; the figures expressing the quantity are but, at the same time, they are more than always the same to the third decimal place, scavengers, they are atmospheric doctors, the errors of experiment falling in the fourth members of a more royal college than that decimal place." Thus the world is in- of surgeons, and divided into no hostile debted to this able man for two atmospheric camps of inimical practices; they not only tests of singular delicacy and accuracy; and carry off what would be noxious to us, but may be that we shall soon have to inau- they also supply us with what is absolutely gurate a new era in hygienic and chemical good and wholesome. They are among the science, the great gate or entrance to which best friends which Nature has given to man; shall be the discoveries and tests of which and, had they no beauty and no sweet we have been speaking. The writer of this odours, no form to delight us, and no paper was witness to certain experiments scented gifts to charm us, they would still made by the per-manganate test, all of be worthy of all gratitude and all honour, which were curiously sensitive and corro- while they drank into their dewy cups and borative. The numbers, taking zero as the tremulous leaves that deadly foe to humaideal condition of purity, were 15 for the nity that subtle, noiseless, penetrating foe, outside of the house, on a small lawn rather carbonic acid gas. The perfection, then, of full of scented flowers; 17 for a small room, Dr. Smith's test would be, the power of with two open windows, looking on to that registering differences in disturbing insame lawn-the experimenter being at the fluences. We believe that he will accomupper end of the room, where there was plish this, and that his instrument will be least ventilation; 28 by the side of a stag- made so complete and sensitive that the exnant pond, not a dozen yards from the house. perimenter may, at a glance, know whether In an open space in the forest, but, sur-the disturbing influence which it registers rounded with trees, and grown over with is hurtful to human health. wild flowers and ferns, it was again 15, the E. L. L. THE PHYSIOLOGY OF HEALTH AND DISEASE. CHAFTER THE FIFTH. of solid constituents, and in containing THE STRUCTURE AND FUNCTIONS OF THE STOMACH-(continued.) THE glands of the human body, connected with the digestive organs of which we have organs which have puzzled physpoken, appear to perform two functions-siologists, and led to the most absurd they separate from the blood matter which notions of its functions, the spleen is the would be injurious to the system; and they most remarkable. It is a soft, highly vas separate it in a form in which, before it is cular organ, situated on the left side of the finally rejected, it becomes subservient to stomach and behind it. Although rich in other functions. Thus the saliva assists in blood-vessels, it has no excretory duct, and the reduction of the food to a pultaceous therefore it can hardly be regarded as a substance; and the bile acts an important gland. It resembles, in its structure, a part in the preparation of the food for its large body on each side of the throat called ultimate uses in the body. Although we the thyroid gland, and also two masses are ignorant of many of the effects produced placed above the kidneys called suprarenal on the animal frame by the action of the capsules. These bodies are sometimes called glands, yet that they are very necessary to vascular or blood glands. When the spleen life may be inferred from the presence of is cut through, it exhibits a very compli these glands so generally even in the lower cated structure, being composed of bloodanimals. This is more especially the case vessels and fibrous and cellular tissue, diswith the salivary glands and the liver, posed in various forms. It is covered with which give indications of their existence a fibrous membrane, which is projected into very low down in the animal scale. Thus its interior, forming a series of follicles. these organs have been found in some of In the walls of these follicles are a number the Entozoa. of gland-like bodies, called the Malpighian bodies of the spleen. They are composed of convoluted blood-vessels and absorbents. the In addition to the liver, the stomach has two other bodies connected with it, of which we must now speak: the one is a true gland, The history of the supposed functions of the other is an organ performing doubtful the spleen is an amusing chapter in phy functions. The first is called the pancreas siology, and shows how little importance is (Fig. 12, hi, p. 212), and the last the spleen to be attached to the mere opinions of the (Fig. 12, r.) The pancreas is a long flat-wisest men upon subjects on which they tened gland, lying immediately behind the stomach; and, when removed from animals, is known by the name of the sweetbread. It is from six to eight inches in length, and weighs from two to four ounces. It is supplied with a number of large blood-vessels, and when cut into, it exhibits a lobular appearance. In its general structure it resembles the salivary glands, its ultimate lobes opening into little ducts, which at last terminate in one large tube called the pancreatic duct, which runs through the entire length of the gland, and passing out joins the common duct of the gall-bladder and liver (Fig. 8, n, p. 145), and opens with it by the same orifice into the duodenum (o). This gland secretes a fluid very like to the saliva; hence it was called by the older anatomists the abdominal salivary gland. The pancreatic juice differs, however, from the saliva, in containing a large quantity have not had an opportunity of making Whatever may be the true function of the spleen, there can be little doubt that it has an important relation to the stomach. It is not found amongst the invertebrate animals, and even when this organ has been removed in the vertebrate animals, they have not immediately suffered. The most probable explanation of its function is, that it acts as a safety-valve for preventing congestion of the stomach during the process of digestion. The distention of the stomach pressing on the portal veins prevents the free passage of the blood through them, and their congestion is relieved by the distention of the spleen. The spleen is known to increase in weight from two to twenty ounces when the portal vein has been tied, and it is more congested after a meal than before. It has been also inferred, from the presence of the Malpighian bodies before alluded to, that the spleen exercises an influence in changing the chyle into blood. of matter. We are now prepared to examine the nature of the changes which the food undergoes in the stomach, previous to its being fitted for the nutrition of the body. The food as it passes into the stomach is a pultaceous mass, and although presenting a very compound character, and composed of substances derived from various sources, may yet be reduced to a few simple classes In the first place, the food is composed of liquid and solid matters. The liquid consists principally of water, either contained with the solid matter when eaten, or introduced separately, either in a pure form, or mixed with tea, coffee, alcohol, or other substances, forming the distinguishing features of our various beverages. This water holds a number of salts, or saline matters which are soluble in water, in solution. There are many such substances in the vegetable and animal food taken by As an illustration, we may mention common salt, which soluble in water, and which is taken in smaller or larger quantities at all our meals. Now, in all parts of the body we find water containing various saline matters in solution, and as we can find no difference between the nature of the water and the salts it holds in solution in the body, and that which these substances possess in the stomach, we infer that in order to get into the body they undergo no change during digestion. We know, in fact, that water, and the solutions of salts in it, can pass through animal membranes without any special organ or process for the purpose. The property of the animal tissues by which this is effected is called permeability. It may be made evident by an easy experiment. If we take a portion of animal membrane-bladder or intestine man. and fill it with water, tying it close, and then plunge into a solution of sugar and water, we shall find that the water will pass out of the little bag of membrane into the sugar and water, and vice versû. The least dense fluid, however, will pass most rapidly into the other, so that our bag would soon exhibit signs of decrease. Wherever fluids are separated by membranes in animal bodies, this process goes on: it takes place in every cell in the human body. To this passage of the fluids in organised bodies the terms endosmosis and exosmosis are applied. Endosmosis means the flow in-exosmosis, the flow out. As we should infer from the structure of the tissues of the body, this process goes on more quickly in some parts of the body than in others. The surfaces on which it is most active are the mucous membrane, and other free surfaces in the interior of the body. No sooner, then, is the food applied to the mucous membranes of the mouth, gullet, and stomach, than this action ensues, and the fluid parts of the food are at once conveyed into the blood. That such is the case we know from the fact that when the pyloric end of the stomach is tied, and fluid introduced into the stomach, it is absorbed into the system. It is also well known that when coloured liquids are taken into the stomach, the colour is communicated to the excretions in the course of a few minutes after their being swallowed. In the same manner, turpentine, camphor, and alcohol, are very speedily smelt in the breath after having been taken. The solid matters of the food (of the division of which into two classes, the heatgiving and the nutritious, we shall have subsequently to speak) are submitted to a much more complicated process. The object of this process is the reduction of a certain quantity of the solid food to a state in which it can be carried into the blood, and the getting rid of the remainder, with certain excretions, as refuse from the system. In order to effect these objects, one of the first agents to which the food is subjected is a liquid formed in the stomach, called the gastric fluid or acid. This fluid is produced in the mucous membrane of the stomach, but is only produced when food is Fig. 15.* present. It is formed by little tubes, or follicles (Fig. 15), which thickly stud the A gastric gland from the middle of the stoma ch. mucous membrane of the stomach, and are aggregated together into the form of small glands. They differ much in form and size in various parts of the stomach (Fig. 16), Fig. 16.* but all agree in having tubes ending in a sacculus, and in several of these being placed together. The tubes open together upon the surface of the stomach, from three to five or more, together, in little pits, or depressions (Fig. 17). From these tubes the gastric fluid issues. The composition of the gastric acid has been the subject of much discussion. It is, however, allowed on all hands, that it contains two distinguishing ingredientsfirst, an acid or acids; second, an organic substance called pepsin. It has been ascertained that in the human body the gastric fluid contains hydrochloric and acetic acids. Pepsin is a compound body, and unites nature of the food. The mass of the food is not all at once reduced to chyme, but the outside first: as it is formed it is propelled from one end of the stomach to the other, and quits it through its pyloric orifice. The motion of the chyme is secured by the muscular action of the stomach, which, as long as food is present, secures the turning round of the whole mass, and the gradual propulsion of it from the cardiac to the pyloric extremity. When the food or chyme has passed out of the stomach into the duodenum (Fig. 8, o, p. 145), it comes in contact with the secretions of the liver and pancreas. We have already hinted that the action of the pancreatic juice seems to be the fitting the fatty parts of the food, which are not affected in the stomach, for absorption into the system. This was a function which at one time was very generally attributed to the bile. Whether either of these secretions produce any effect on the fatty matters of the food or not, it shows that the purpose of the bile is not yet fully understood. Surely this ought to be a lesson to those pretenders to a knowledge of the physiology of health and disease who speak of the bile as though its whole purpose and object in the economy of nature was known, and who speak as confidently of bilious diseases as they impudently recommend their antibilious nostrums for their cure. We know, in fact, very little with regard to the nature and functions of the bile, and the best way to know more is to confess our ignorance. The summary of our knowledge of the bile is, that it is secreted, as described in our last chapter, in the liver, and that it either passes directly into the duodenum, or accumulates in the gallbladder, from whence it is ejected when needed. On reaching the chyme, the bile produces a remarkable effect upon it, separating it into three distinct parts, which may be best seen by removing the chyme, and adding the bile to it out of the body. These three parts are, first, a reddish brown sediment, which sinks to the bottom; second, a fluid like whey, which occupies the centre; and third, a cream-like pellicle, which floats on the top. It is only a portion of these substances that are absorbed into the system; there can be no doubt that the creamy matter at top is one, but how much of the other substances is absorbed is doubtful. plicated. It consists of from eight to ten The composition of the bile is very comThe solid matter consists of various salts per cent. solid matter, the rest water. |