Convulsions and even death caused by allowing children to walk about in the water at the sea-shore with their clothes tucked up, their feet chilled, and their heads exposed to the blazing sun. Whit field (Brit. Med. Jour., Aug. 8, '96).
The majority of cases occur in the afternoon, though cases are not infre quently observed at night, especially in poorly-ventilated quarters. In stoke holes, boiler-rooms, sugar-refineries, etc., where the heat is intense, heat-strokes may occur at any time.
Pathology.—After a study of eight hundred and five cases of insolation, Lambert and Van Gieson found that heat alone is not sufficient to explain all the clinical and pathological observe tions. The prodromal symptoms of sun stroke are those of acute functional dis turbance, while the later symptoms, much more serious, point to grave changes in the blood and in all the nerve-centres, especially those of the latter which control the thermic mech anism of the body.
Van Gieson examined the brain and cord in several of Lanibert's fatal cases, and found universal exhibition of acute degeneration of the neurons of the whole neural axis. In the cerebral cortex and cerebellum the cells showed the same degenerated changes; the cells of the spinal cord were not so extensively involved. The toxic agency of the symptoms of insolation seem to be shown by the changes found in the gan glion-cells. They were, in every way, similar to those produced by a number of other poisons, such as by alcohol, lead, etc., and by bacterial products.
The experiments by Vallin would tend to show that coagulation of the albuminoid bodies occurs. The toxin mia would thus occur as a result of arrested metabolism. The blood is dark, though fluid, and the corpuscles are crenated. In the hyperpyrexial form leucocytosis and degeneration of the red corpuscles may also be noted. Extravasations in the peripheral tissues are often found, and the body undergoes rapid putrefac tion.
According to de Santi, insolation is in all cases characterized, from a patholog ical point of view, by arrest of the heart, but dependent on different causes.
These may be classified as arising from intoxication by the products of muscular effort; from asphyxia; from a malarial infection called into activity by fatigue or heat. In the first form, that of in toxication by the products of muscular exertion, the victims are chiefly among soldiers unaccustomed to the fatigue of a march. The attacks occur when the temperature is high and the air is calm and humid; so that the cutaneous evapo ration is small. Sambon has emphasized the microbic origin of insolation.
The following is a description of the micro-organism found in the blood of patients suffering from heat-apoplexy and regarded as the specific cause of that disease. It is linear, ineurved, and slightly constricted in the middle. Viewed in the blood, it is from 2 to 2.5 microns long, and 0.5 micron thick; in cultures it is somewhat larger. It pre sents filaments, is slightly motile, but possesses no cilia, stains easily with ani line colors, but not by Gram's method. There are free spores in the cultures as well as in the rods. It is aerobic, does not cause fermentation in sugars, and does not give rise to indol. It grows between 30° and 37° C., but is instantly killed by a moist heat of 70° to 75° C. Cagieol and Lapierre (Montreal Clinique, Apr., '98).
Siriasis is unknown in many of the hottest countries of the world. Many critics have confounded the disease with ordinary syncope. The destruction of the red blood-cells in siriasis points to a toxic element in the blood of microbic origin. Sambon (Brit. Med. Jour., Sept. 9, '99).
In the British army in India heat stroke is most fatal and most prevalent where the heat is greatest and most op pressive, and at the time of the year when these influences are at their maxi mum. It will require much more evi dence than has yet been produced to make those who have had experience of the disease in India accept a microbial or other cause which seeks to minimize the great and predominating influence of fierce and continuous heat. W. J. Buchanan (Lancet, Sept. 15, 1900).