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VOL. IV. No. 7.

Hygiene.

BY ALFRED CARPENTER, M.D., M.R.C.P. (LOND.),
Chairman of the Council of the Sanitary Institute.
TEA AND COFFEE, AND SIMILAR
BEVERAGES.

THAT infusions of vegetable substances fill an important position, as articles of food, in the economy of nature cannot be doubted; they have been used in some form or other from time immemorial. Infusions of bitter herbs are occasionally mentioned in the older writers, as diet drinks. We read that Esau sold his birthright for a mess of pottage. Jacob sod (seethed) pottage, and Esau, being faint, desired it. Whether this was some form of tea, or, which is more probable, some alcoholic drink made from lentils, a farinaceous fruit, is uncertain; I incline to the view that it was alcoholic. There is no doubt as to the bitter waters in the wilderness at Marah. These were sweetened by infusing the leaves of some shrub growing in the neighbourhood, and a kind of tea produced, by means of which the Israelites assuaged their thirst. This use of vegetables for correcting the badness of a water supply, therefore, is very ancient, and in the case of the Israelites deservedly ranked as a miracle; and whilst such infusions are grateful in themselves, we also have the agreeable feeling that they give us the best means of purifying an unwholesome water, and save us from its fatal consequences. Tea and its congeners are, therefore, great sanitary aids. It provides for us the cups that cheer, but not inebriate' (Cowper). The usual dietetic infusions and decoctions have active principles, which go by the name of Theine, Caffeine, Cocoine, Guaranine, Theobromine, etc. These principles are alkaline in their nature, and are identical in their effects, both chemically and physiologically; in large doses they produce convulsions, tetanus, paralysis, etc. It is said that their universal use must indicate a universal want in our natural constitution, and that they serve some physiological condition which men of science have not yet been able to point out; but the same has been said of intoxicating beverages; these, however, are thoroughly nonintoxicants. It is singular that those most generally in use are taken from allied classes of vegetables, but they are not restricted to one or two classes, for an immense number of dried leaves and prepared twigs

VOL. IV.

and roots, taken from all divisions in the vegetable kingdom, have been used for similar purposes. The popular infusions are very much alike; they contain volatile oil and astringent matter, with some so-called alkaloid which is crystallizable and is rich in nitrogen. It is possible, as has been pointed out by Liebig, that they may assist in the production of bile. They are closely related in their composition to nerve tissue, and seem to be of service in repairing exhausted brainmatter. They act to some extent in the same direction as alcohol-that is, in retarding the waste of tissue; they seem to enable food to go further than it otherwise would, so that men can, by the aid of tea or coffee, do more work with less exhaustion than with any other kind of ordinary liquid food. It is found that there is a difference also in the result as to the excretion of CO2? for whilst alcohol diminishes the formation of this debris, both tea and coffee increase the quantity excreted to a slight degree. It has been likened to the action of oil upon delicate machinery, lubricating the animal system, and so enabling it to work rather easier. The late Dr. E. Smith has pointed out that there is a greater depth and more freedom in respiration under their influences, and that the transformation of starchy and fatty food is promoted. But whilst tea induces perspiration and lessens the heat of the body, coffee dries the skin and acts upon the mucous membrane of the bowels. Each, therefore, is suited for different times and different constitutions. Cocoa differs from tea and coffee in containing a large amount of fatty and albuminous matter, and is therefore a more decided food, and has a high nutritive power. It is not so easily digested by a delicate stomach.

There are fictitious teas, coffees, and cocoas, which have none of the true advantages which belong to the real articles. The earth-nut, the chestnut, and the chicory root, do not possess the alkaloid, and have not therefore any of the distinctive properties which belong to the more specific form of diet drinks, and cannot be properly substituted for them; whilst infusions of other herbs are none of them so exhilarating and refreshing as ever to be likely to replace tea and coffee in the estimation of mankind.

AIR ITS HYGIENIC PROPERTIES. AIR consists of O 209, N 78°4, CO2 04, aqueous vapours 86, in 100 parts. There are sometimes also

U

traces of NH, N2O5, CH4, and SO2, and Ozone; the aqueous vapour is, however, very variable. The impurities consist of increase in the quantity of CO 2, in the more decided presence of SO, and NH3, with SH, and floating carbon, oily and organic particles of various kinds, the products of smoking chimneys. The oxygen is diminished by all those agencies which lead to oxidation, such as the respiration of animals and consumption of carbon by fires, etc., the oxidation of metals, and decomposition of all organic matters. It is, however, a curious point, that the open air in the worst districts of London and the densest parts of all large cities scarcely varies more than 700 parts in a million in the worst situation as compared with the best; whilst if the air be taken from the pit of a crowded and ill-ventilated theatre when at its worst, there is a loss of not more than 3000 parts in the million as compared with that in the open country. If the quantity of oxygen is diminished from 2019 to 18.5 per cent. a candle cannot burn in it, and, of course, animal life would soon also cease. A loss which equals three parts in a 1000 (3000 in a million) does not appear to be much, but it has a wonderful effect upon the animal world; we have, therefore, to consider the presence or absence of very minute quantities. Dr. Angus Smith has shown this very clearly in his wonderful work on 'Air and Rain,' which should be consulted by all who are observers in this direction. It is probable that the absence of O (being always accompanied by the presence of some other and unnecessary gas) may not be the real factor in the effects produced, but that it is the introduction of the impurity which has been formed at the expense of the O which has been lost. CO, is always present in the air. It is found in the open country, on mountaintops, and in deep valleys, upon the broad Atlantic, and in the caverns of the earth. Its average is about 4 parts in 10,000. It is largely increased in crowded towns, in ill-ventilated apartments, wherever life abounds and oxidation is in action. The rapid diffusive power which belongs to all gases is very manifest in the case of CO2, for it is seldom found to exceed 1 per cent. in the open, in the most densely populated towns. Dr. Angus Smith says there is no difference even in the second decimal place as to the normal in country places, and he considers 0336 per cent. (which is less than 4 parts in 10,000) in uncontaminated places as a good average. The senses are able to appreciate a difference which is exceedingly minute. This may be observed in any crowded town as compared with some open space in close proximity, and in which the excess is probably less than two parts in 10,000. The ground air of a given place is sometimes much more impure as oxidation is progressing, in consequence of the decay of organic life. CO, abounds; it is always excessive in such cases, rising, sometimes, to three or four per cent. There is an antagonism as regards the production of CO2 between animal and vegetable life; all animals produce it in consequence of the act of living; all vege. tables live upon it and return oxygen separated from the carbon back into the atmosphere. There are exceptions in the case of fungi, which give out CO., and some forms of animalcular life, which set oxygen free; but the rule is as stated; the one kingdom counteracts the depreciating power of the other. There is a doubt in the minds of some sanitarians as to the injurious effect of excess of CO2. They refer to the

fact that it may be breathed in much larger quantities than normally exist in the atmosphere, without injurious effects, provided the O is undiminished and organic impurities do not abound. It is supposed that there are more dangerous effects from the ammonia compounds and other impurities which are given off by the breath, and which rapidly putrify, and that these are the materials which give rise to danger in denselypeopled districts and over-crowded habitations; that we must look to these gases, and the minute organisms which accompany their production, for the causes of mischief, and not merely to the presence of CO, in excess. It is probable that the truth lies in a combination of both, and that small quantities of the ammonia compounds would be comparatively harmless if CO2 was not in excess and if O was at its normal amount.

Nitrogen. This part of the atmosphere appears to be negative in its qualities, and as if it existed for the purpose of diluting the oxygen, which in its pure form cannot be breathed for many minutes with impunity. It forms four-fifths of the bulk of the air. It is very inert, and animals die if kept in N simply from the absence of O; and yet in its nascent form it has tremendous power. Its deficiency or excess is of no moment in its usual state, and it need not be further considered, except in connection with its alliance with hydrogen, by which ammonia is evolved.

Ammonia, NH.-This gas is always present in the neighbourhood of large towns, either in its simple or in its combined forms. It is always found in the rain which is collected in inhabited districts, but it is the first part of a shower which contains the largest part of ammonia. The rain washes it out of the atmosphere, and sends it into the earth as food for the vegetable world; it combines with sulphurous and nitrous acids, forming ammoniacal salts, which are decomposed if the water is evaporated to dryness, and the acids then combine with the lime or soda salts, etc., which also frequently find access to deposits of rain water. The quantity is extremely minute; it is increased in foggy weather, especially in those fogs which are associated with smoke produced by the consumption of coal. Dr. Angus Smith has calculated the average to be about of a milligramme per litre, and he states on the authority of M. Bineau, that the quantities of ammonia furnished by the rain in each year would be equal to about of that which was afforded by an ordinary manure dressing, but there is a great difference in different districts according to the populous state of the country in which the specimen has been collected. Dr. A. Smith's conclusions are, that ammoniacal salts increase in the rains as towns increase, that they come partly from coal and partly from decomposed albumenoid substances, and may be taken as measures of population.

Nitric Acid, NO-When the O of the air acts on the NH, or the organic substances containing N, it forms nitric acid. Within certain limits it increases in quantity in the higher regions of the air, and it increases as the quantity of ammonia diminishes. It is more evident in a continental or an inland town than on the sea-coast, and its presence in the air of the British Isles is very much interfered with by the presence of SO2, which our fuel provides; it is more abundant in the rain which descends at the first onset of a thunderstorm, and it is also probably formed by the passage of electric currents through the air.