116 ARON. 



I have exposed the heads only of monkeys, by placing their bo- 

 dies in a large wooden box 33 by 33 by 50 centimeters, the top of 

 the box being fitted closely around the neck of the animal. Several 

 holes were made in its walls to allow a free circulation of air, and, 

 finally, the first box was placed inside a second, larger one, 50 by 50 by 

 48 centimeters. In this way the body was in the shade and well pro- 

 tected against the rays of the sun, while the head was unprotected. 

 Monkeys have been exposed in this way for several days, from morning 

 to afternoon, without any effect. One monkey, number 6, was insolated 

 in this way for a total of fifty-four hours in twelve days, and the animal 

 is still well and healthy. Temperatures up to 47° were measured in the 

 hair of the head during several exposures, but the rectal and subcutaneous 

 temperatures of the animal never went above the normal, 



P. Schmidt ^* assumes that the heat rays from the sun, although partly 

 absorbed by the skin and bone of the skull, at least in part penetrate the 

 brain, and the latter organ, being very sensitive to an increase of heat, 

 will not withstand the effects of the rays. 



In my experiments with the monkeys in the box the heat rays could 

 penetrate freely to the brain. The fact that the radiation reaches the 

 skull appears to have no effect, if the body temperature does not rise at 

 the same time. 



Deleterious effects are only observed when the body temperature rises 

 to febrile heights, but if this rise is prevented by a strong current of air 

 or by protecting the greater part of the body against the heat rays, the 

 animal will not suffer from radiation from the sun. 



Post-mortem findings on monkeys dying after exposure to the sun, give 

 the following characteristics : 



Hypersemia of the subcutaneous vessels and of all internal organs. In 

 two monkeys small haemorrhages in the subcutaneous tissues and in some 

 of the muscles are observed. I can not exclude injury from the chains 

 with which the animals were fastened as a cause of the latter condition. 

 The alterations in heart and brain are of greater interst : All monkeys ^^ 

 which die after exposure to the sun show extensive haemorrhages in the 

 muscular wall of the left ventricle. These hsemorrhages are situated 

 beneath the endocardium and for the greater part near the auriculo-ven- 

 tricular border, sometimes they are also in the papillary muscles. Their 

 extent and number varies somewhat, the smallest are rectangular, 3 by 3 

 millimeters. Considering the size of a small monkey's heart, these are 

 quite severe alterations. The vessels of the dura mater are far more 

 distended than with normal monkeys, and at several places small hsemor- 

 rhages are found. The arachnoidea is slightly raised by an exudate lying 



" hoc. cit. 



" This protocol ia based on seven animals. 



