RADIATION 



M5 



whether there is such a condition, were those by Scaghosi on rabbits 

 exposed to the Sicilian sun. Their temperature rose considerably, 

 and if the experiment was continued long enough they died, but 

 if it was stopped they recovered. The post-mortem changes were 

 hyperaemia of the meninges, heart, lungs, liver, and spleen. The 

 nerve cells of the brain and spinal cord showed coagulative necrosis 

 and chromatolysis. 



The next experiments of importance on the aetiology of this 

 condition are those of Moller on rabbits, who showed that thermal 

 rays, with or without chemical rays, if directed on to the skin cover- 

 ing the skull, produced more or less intense cerebral disturbance, 

 and sometimes even sudden death. The autopsy after intense 

 irradiation showed the skin of the head much swollen and bloody, 

 with gelatinous exudation in the subcutaneous tissue. The peri-, 

 osteum, cranial bones, and dura were discoloured, and covered with 

 ecchymoses. The vessels of the brain surface were much dilated, 

 and showed numerous, and in part confluent, ecchymoses. 



Our own experiments on rabbits, performed yearly for several 

 years, during the particularly hot weather in Colombo, show that 

 if such animals are exposed to the sun at about twelve noon they 

 die with all the symptoms, post-mortem appearances, macroscopical 

 and microscopical, of sunstroke, in about sixty-seven minutes, 

 whereas other rabbits similarly treated and exposed at the same 

 time and in the same place, but protected by red glass, live. 

 Although it is true that the red glass did absorb a proportion of the 

 heat rays, still the rabbit was intensely hot to the touch at the end 

 of the experiment, being kept in position under the red glass by 

 being placed in a box painted black externally and so narrow that 

 the sun's rays fell directly upon its shaven head and unshaven back. 

 Nevertheless, the protected rabbits, though kept under observation 

 for months, never seemed to be any the worse for their treatment. 



We came to the conclusion that the ultra-violet rays were not 

 the pathogenic agent in these experiments, but that the active rays 

 were in the visible blue and violet ; and in this we were much aided 

 by Professor Browning, who supplied us with glasses spectroscopi- 

 cally adjusted. 



Aron studied the action of the tropical sun in the Philippine Islands, and 

 concluded — 



1 . Under climatic conditions rabbits and monkeys, having by nature only 

 a limited power of physical heat regulation, die if exposed to sun, the body 

 temperature rising to febrile heights. 



2. The post-mortem findings are haemorrhagic lesions of the meninges and 

 (in monkeys) of the heart. 



3. In animals with a poorly developed sweat-gland system the subcutaneous 

 tissues are heated by radiation from the sun to temperatures above that com- 

 patible with life. 



4. The human skin is warmed to about 3° to 4° above normal skin tempera- 

 ture, but an increase in bodily temperature is prevented by evaporation of 

 sweat, which causes a fall of skin temperature. 



5. Brown skin shows a smaller rise in temperature than white skin, due pos- 

 sibly to an earlier and better water evaporation by sweat secretion. Hence a 

 coloured skin is a better heat regulator than a white skin. 



