Licence: Public Domain Mark
Credit: A text-book of pathology / by Alfred Stengel. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![lire of the heart, or the respiratory muscles. Before this extreme is reached, however, it may be found that the consumption of the tissues of the body is greatly in excess, though the respiratory quotient is altered in favor of the amount of air inhaled. Con- tinuous exposure to excessive heat frequently causes peculiar dis- turbances in man, known as heatstroke, sunstroke, or insolation and heat-exhaustion. In these conditions hyperemia and edema, or even inflammation of the meninges, may occur. These lesions are sometimes supposed to be the result of the direct effect of the heat; but there is reason to believe that they may be occa- sioned by poisonous substances produced within the body by dis- turbed metabolism, as a result of the heat. Cold.—Exposure to extreme degrees of cold may cause results quite similar to those produced by heat. Exposure of the skin to liquefied air, solidified mercury, or other substances at excessively low temperatures produces vesiculation and necrosis of the tissues like those produced in burns. Exposure of the body to greatly reduced but bearable tempera- tures of the surrounding atmosphere causes vascular disturbances followed by necrosis of the tissues and inflammatory changes. The parts so affected are the extremities or projections of the body, like the toes and fingers, nose and ears. The primary result of cold is vascular constriction and local anemia. These serve the purpose of preserving the body heat by preventing heat radiation ; later the blood-vessels are paralyzed and extreme hyper- emia results. Then cellular exudation and necrosis may occur. These changes are well seen in the condition termed chilblain. In prolonged exposure to cold there are a gradual reduction in the activity of the various organs and a gradual obtunding of the sensibility till the patient becomes comatose. The retention of excrementitious products of metabolism, or the formation of products of abnormal metabolism, may be important in causing this condition. Exposure to cold plays an important part as a clinical cause of disease. Various forms of pharyngitis and coryza or bronchitis so frequently follow such exposure that the term cold is gener- ally used._ Other conditions,like rheumatism, pleurisy, pneumonia, and the like, bear a similar relation. It is now recognized that in most of these cases cold is merely a predisposing cause, the imme- diate cause being in many, if not all, cases specific micro-organ- isms. The mode of action of the exposure is uncertain ; probably it causes a reduction in the resisting ]K)wers of the organism and thus favors the activity of bacteria. In some cases it may be that the cold alters the fluids of the body in such a way as to permit increased virulence of micro-organisms alreadv ju-csent, or to pro- mote their entrance into the system. Increased Atmospheric Pressure.—Exposure to extreme](https://iiif.wellcomecollection.org/image/b21981668_0023.jp2/full/800%2C/0/default.jpg)
