William Jay Youmans

“ We patch together different shreds of our mental experience of large things, and construct a symbolic idea which represents our planet, but we never grasp the reality in the immensity of its proportions.
Light is a force, and science holds that it is made up of impulses. ”

“ But, when we are told that the ray enters the eye at the rate of 185,000 miles per second, and—as each inch contains 57,000 waves—that when we are looking at a violet object there are 699,000,000,000,000 beats upon the retina each second, the statement baffles all imagination: we may accept, but cannot understand it. In the attempt to penetrate the nature of light we are lost in the mysteries of the infinite. ”

“ Although the luminous force acts only upon the nerve of the eye to stir up a sensation, yet we know how infinitely complex and varied is the world of color that results. There is evidence that the dark thermal and chemical radiations are of equal variability and complexity, yet there can be no doubt that all these multitudinous effects are due to a single mode of action. The difference between the thermal and the chemical rays is simply the difference between the red and the green ”

“ Of course the effect of such abrupt transitions from perfect illumination to total darkness, if it were the plan of Nature, would be most inconvenient and painful, if not destructive to the eyes. We are protected from this by the phenomena of double shadows, and the gradual passage from darkness to light, although each luminous ray moves undeviatingly in its straight line. ”

“ It is not light that makes the picture, but dark radiations that are associated with it, and that have the peculiar effect of producing changes in certain chemical compounds.
Although photography, in its wonderful development as an art, belongs to the past generation, yet the knowledge of the chemical effects ascribed to light is as old as chemical science. ”

“ Not that the body can bear unlimited exposure to great heat, any more than it can endure continuous exertion, but that it is capable of maintaining itself under even excessive heat, if the exposure is not too prolonged. ”

“ Somehow, in their mysterious nature, the luminous rays from all sources, distant and remote, effect a change in the nerve-structure of the eye by which impressions are transmitted to the brain. Into that mode of action we cannot now enter, but will confine our attention at present to the property of light by which luminous images are produced. For it is, after all, the images of things we have to deal with. We know the external world in its distances, forms, and colors, because its visible objects are all duplicated in the eye. ”

“ With this hasty sketch of the heat-producing and heat-regulating functions of the animal economy, we pass to a brief consideration of some of the more important ill-effects resulting from the action of excessive heat on the conditions of health and on the body itself.
High temperature is a powerful aid to decomposition. Dead organic matter, under its influence, speedily decays, giving rise to foul and poisonous products which, escaping into the atmosphere, find their way, sooner or later, into the system. ”

“ But, when thus exposed, the extensive evaporating surfaces of the lungs and skin are called into more active play; and, if the air is of average dryness, heat is rapidly thrown off by perspiration, the loss being so nicely adjusted that a uniform temperature of 99° Fahr. is continuously maintained. This heat-regulating function of the organism is one of the marvels of physiology. In spite of the vicissitudes of climate and season, it ever holds the temperature at a uniform degree, and, even under the stress of high artificial heat, is able to keep the balance comparatively unchanged. ”

“ In children and in females, especially in early age, the principal seat of the fatty deposit is in the cellular tissue, immediately under the skin. During adolescence, the fat has a tendency to disappear from this situation; but, about middle age, frequently becomes again deposited, not only in the subcutaneous tissues, but also in the neighborhood of certain internal viscera. The quality of the fat also varies, both with the age and with the part in which it is deposited. It is firmer and higher colored in old persons than in young ones ”

“ Although obesity may be ranked among the diseases arising from original imperfection in the functions of some of the organs, it is also, without doubt, most intimately connected with our habits of life. The inconveniences arising from it are, therefore, to be removed by correcting those habits, especially such as relate to diet and regimen. Drugs without number have been tried, both for the removal of corpulence itself, and for the many troubles to which it gives rise; but they have almost uniformly failed when diet and exercise have been neglected. ”

“ It has been thought that the nitrogenous foods are consumed chiefly in the formation of the tissues, while the non-nitrogenous are devoted mainly to the function of respiration, going principally to the maintenance of the animal temperature. Whatever basis in fact this view may have, it is pretty well established that the substances belonging to the latter class of foods are especially favorable to the production of fat, when taken into the system. This fat may exist ready formed in the food, as it is furnished abundantly by both the animal and vegetable kingdoms ”

“ The sense of taste, which, to according many physiologists, is properly limited to the perception of the acid, bitter, sweet, or saline properties of food, does not appear to suffer; but the power to recognize and enjoy flavors, which is commonly associated with taste, but which in reality belongs to the nose, is sometimes lost along with the sense of smell. Access of air to the middle ear through the Eustachian tubes is an essential to the sense of hearing, and this, too, is greatly interfered with oftentimes by the fatty thickening of the mucous membrane of the nose and throat. ”

“ THE healthy human body has a temperature which varies but little either way from 99° Fahr. The heat required to maintain this temperature is derived from the oxidation within the body of the elements of the food. In other words, our bodies are furnaces; the food we take is the fuel which supplies the furnace, and the air we breathe is the draught that keeps the combustion going. The amount of heat thus evolved is, in health, always in excess of that needed to maintain the required temperature. ”

“ Points that are very near the outer boundaries are very slightly darkened, if near the total shadow they are almost completely shaded. The penumbra is, therefore, not a uniform shadow, but gradually fades into darkness from its outer limit to the total obscuration of the umbra. It follows from this that the shadow of an opaque body falling upon a screen will not have a sharply-defined edge, but will show a transition from total shadow to the complete absence of shadow. To have the shadow clean and sharp at its edge, it would be necessary to have the source of illumination a mere point. ”

“ In all these instances heat appears to act not so much upon the body itself as upon the various external agencies influencing health. It is to bad conditions what fire is to powder. If the match is withheld, the powder is harmless; but, as the two are liable to come together, we secure safety by removing the magazine. So the presence of filth in water, in soil, and above-ground, may be innocuous by itself, but let the action of heat touch it off into decomposition, and we at once get the effects in the shape of disease. ”

“ If we construct a conical surface touching the body all round, and having its vertex at the luminous point, it is evident that all the space within this surface on the farther side of the opaque body is completely screened from the rays. The cone thus constructed is called the shadow-cone, and its intersection with any surface behind the opaque body defines the shadow cast upon that surface. In the case which we have been supposing—that of a luminous point—the shadow-cone and the shadow itself will be sharply defined. ”

“ The pupils fail to respond to the action of light, and may be somewhat contracted, the breathing becomes hurried and difficult, and the action of the heart is irregular and tumultuous. Convulsions may come on early, or be postponed until late in the disease, or they may be absent altogether. Numerous minor and less constant phenomena have been recorded by different observers; but, when a person is suddenly attacked during exposure to great heat, the symptoms already enumerated will enable any one of ordinary intelligence to recognize the true character of the disease. ”

“ If, by exposure to cold, for example, heat is lost more rapidly from the surface than it is supplied within, its warmth must decrease, and there needs but a few degrees of fall to induce disease; on the other hand, if, by exposure to external heat, loss from the body is impeded, its temperature rises, and disease again results.
In hot climates, or during the hot season in temperate latitudes, we are in contact with an atmosphere which frequently attains a temperature nearly or quite equal to that of the body ”

“ The belief is universal in that country, that excision of the tip of the tongue permanently destroys the power of speech, while its removal at or near the root leaves the victim a chance of regaining the ability to again speak his mind. ”

“ Nature has been shown to conform all kinds of dynâmical effects to rhythmical pulsing, or wave-like action and the impulses of light are held to be of the same kind. There are, at any rate, measurable effects which are unequal in the different colored lights, and the scale has been determined. In an inch of violet light it is shown that there are no less than 57,000 waves, a statement in which there is nothing extraordinary or impossible, as Nobert, the German optician, is in the habit of ruling his microscopical test-glasses at rates all the way from 100,000 to 200,000 per inch. ”

“ This fact is illustrated by numerous instances both among the lower animals and among men. At Strasbourg, the geese are fattened by shutting them up in darkened coops within a heated room, and stuffing them constantly with food. The high temperature lessens the escape of heat, and thus favors the process. Here all the conditions for insuring obesity are resorted to—viz., external heat, obscurity, inactivity, and the cramming of the animals with fattening food. A still greater refinement for pandering to the appetite is resorted to by the Italians who relish the fat of the ortolan. ”

“ Climate and locality seem also to exert considerable influence on the deposition of fat. The inhabitants of low, swampy situations, in temperate climates, are usually remarkable for their bulky flabbiness, and propensity to corpulence; while the inhabitants of very hot and of very cold climates, as well as the inhabitants of mountainous regions, have, perhaps, less tendency to obesity. There is this remarkable difference, however, between the dwellers in hot, and in cold climates: those living in hot climates rarely become fat, without becoming otherwise diseased ”

“ Decaying vegetable matter in the soil is held to be the source of malarial poison; and here, again, if moisture is present, decay is always hastened and increased by excessive heat. So great, in the opinion of Dr. Parkes, is the influence of heat on the development and spread of malarious disease, that, in selecting a residence with a view to escaping its effects, he recommends that, in tropical countries, the point be 1,000 or 1,500 feet higher above the source of the poison than is required in temperate latitudes. ”

“ Light cannot turn corners like sound. This is explained by the excessive shortness of the luminous as compared with sonorous waves. Sound-waves are so large that they flow around objects in the air, and consequently cast but feeble shadows, although Deschanel (from whose admirable work on "Natural Philosophy" our cuts are borrowed) states that Collodon, in his experiments on the transmission of sound through the water of the Lake of Geneva, established the presence of a very sharply-defined sound-shadow in the water behind the end of a projecting wall. ”

“ Heat thus aids the pollution of both air and water, keeps alive and active the germs of disease in the excreta of the sick, and in both ways favors the spread of contagion.
Its direct action upon the person becomes most apparent when some of the functions are going wrong. When the body is healthy, and proper precautions are taken in its management, there is little to fear from exposure to heat. ”

“ MANY animals possess the attribute of voice, but man is the only one among them all capable of modulating voice into speech. This he does by changing the shape of the cavities of the throat, mouth, and nose, by the actions of the muscles which move the walls of those parts, and by the movements of the tongue. The latter organ is commonly credited with the most important share of the work ”

“ WITH that proneness to go wrong, which we notice in most things human, and which crops out in science as well as elsewhere, the art of making pictures by the chemical action of radiant forces has got a false name. ”

“ Sunstroke, or the disease hitherto passing under that name, though known since early times, is even yet not well understood. Up to within a few years, it was believed by patient and physician alike that, to produce it, the body, and especially the head, must be exposed to the direct rays of the sun. There is now abundance of proof to the contrary. ”