322 CHAIRMAN'S SUMMATION 



what happens after radiation. One of the interesting points was the variable latent 

 period, namely, anywhere from 3 to 9 months after the animals were exposed 

 to 3,500 r, before lesions became apparent. This matter of the latent period, as 

 it concerns individual variation, is a common problem, and it always requires a 

 large series of animals before one can reach dependable conclusions. This brings 

 us to the concept of the delayed radionecrosis described by Professor Scholz. He 

 demonstrated swelling and disintegration of vessel walls before there was any 

 visible change in the surrounding spinal cord substance. The question arises as 

 to whether these vascular changes and exudative phenomena, the existence of 

 which there can be no question as seen in Professor Scholz' lantern slides, may 

 be the outcome of some peculiar sensitivity reaction. It is interesting that Dr. 

 Roizin is of the opinion that what he saw today might possibly be construed as 

 a sensitivity reaction and that the change was primarily in the vessels rather than 

 in the nerve substance around the vessels. Dr. Vogel pointed out, as did Dr. 

 Schummelfeder and others, that radiovulnerability of the cells in the central 

 nervous system varies with the species. This is a general principle of which we 

 must all be aware, but which some of us now and then tend to overlook. 



