HIGH ATMOSPHERIC TEMPERATURES 



139 



conditions, the medical writers of ancient times were silent about them. 

 This does not seem to be quite just, for Paulus ^gineta, Oribasius, and the 

 Arabians certainly understood that there were head symptoms which they 

 called ' siriasis ' (after Sirius, the dog-star), due to excessive heat. Certainly 

 this knowledge was lost, and Cardanus, in the sixteenth century, describes 

 symptoms due to morbus attonitus (apoplexy) brought about by the heat and 

 drought of the summer of 1543 in Florence. After this for a long time the 

 disease was considered to be an apoplexy till Boerhaave, early in the 

 eighteenth century, introduced the name ' insolatio,' and considered it to be 

 a phrenitis — i.e., meningitis. 



Steinkiihl (1819) thought that the congestion of the lungs caused death by 

 asphyxia; Swift (1854) that it was due to exhaustion produced by fatigue; 

 Hill (1857) evidently confounded pernicious malaria and heat stroke. Levick 

 (1859) suggested that it was an acute specific fever; H. C. Wood (1863) con- 

 sidered that it was due to a poison developed in the blood, and called it 

 thermic fever; while Stiles (1864) performed experiments on animals, and 

 concluded that the disease was due to the direct effect of heat on the muscular 

 system. 



In i86g Eulenberg and Vohl stated that the disease was due to sudden 

 liberation of the gases in the blood ; and Weikard and Richardson attributed 

 it to clotting of blood in the vessels. 



In 1870 Vallin performed several experiments by locally heating parts of 

 the body, and concluded that there were two conditions: (i) sthenic insolation, 

 due to coagulation of the muscle fibres of the left ventricle; (2) asthenic 

 insolation, due to the action of heat on the nerve centres of the brain, thus 

 disturbing the innervation of the heart. 



In 1 87 1 and 1872 Claude Bernard performed some experiments which 

 tended to show that when a warm-blooded animal died as the result of heat, 

 it was due to rigor in the musculature of the heart. 



In 1872 H. C. Wood performed experiments which showed that sunstroke 

 could be produced in animals as readily as in man by artificial or natural 

 heat. 



He came to the conclusion that death took place from asphyxia, and that 

 after death the rigidity of heart and muscles was due to the coagulation of 

 the myosin, and he further pointed out that this will take place at once in the 

 heart if the temperature of the body reaches 115° F., and said that he con- 

 sidered it to be the cause of sudden deaths in soldiers in battle. Further, he 

 pointed out that the heating of the brain of a mammal to 108° F. produces 

 insensibility, with or without convulsions, and that when 1 13° F. was reached 

 the animal died, and that, though the general symptoms of sunstroke were 

 absent; the nervous symptoms were present. He came to the conclusion that 

 no capillary thrombi were formed, that no poisons were generated in the 

 blood, and that the real condition was the heat acting upon the nervous 

 system, as a result of which there was rapid metabolism, which used up 

 oxygen and at the same time induced brain changes, causing asphyxia. But 

 he distinguished from the true heat-stroke: — 



1. Acute meningitis or phrenitis, due to exposure to the sun, in which he 

 disbelieved. 



2. Heat exhaustion, due to working in a heated atmosphere, which he said 

 did not differ from acute exhaustion due to other causes, and therefore v/as 

 not true sunstroke. 



In 1879 Jacubash classified heat accidents into: (i) sunstroke due to the 

 action of the sun on the body, when the temperature may reach 113° to 

 115° F. (45° to 46° C.) ; (2) heat-stroke, due to exertion, and often seen in 

 marching troops in the Temperate Zone; (3) thermic fever, which he considered 

 to be the true heat-stroke of the tropics, due to accumulation of heat in the 

 human body in consequence of high atmospheric temperatures without 

 exposure to the sun or muscular exercise. 



Dony (1884) considered that there were two main conditions: (i) sunstroke, 

 due to the sun's rays acting upon the cranium and brain, only without very 

 great rise of temperature; and (2) heat-stroke, due to intense heat acting on 



