318 



We now get a measure of tlie obstructions bj expressing tlie 

 differences in percentages of the amounts of inculcation. 



Age 



Obstruction 



9 — 15 years 

 16—40 „ 



45 o/„ 

 44.1 7o 



over 40 „ 52 "/o 



From these tables it is apparent that this investigation proves what 

 is to be expected, that the iiu'ulcation is smallest above 40 years of 

 age, and that the destiuctiou of impulses received is then also strongest. 



These lamp-tests were modified in such a way that this investigation 

 became serviceable for clinical purposes. Just as with the former tests 

 we expei'imeuted on five different days, now however not in a dark 

 room, but iu broad daylight. Four round coloured discs were pasted 

 on a piece of grey caidboard. These colours were shown to the 

 subject during 2 .'seconds. Then, after an inteival of 15 sec. he had 

 to name the colours in the riglit order. If the answer was not 

 correct, the colours were exposed till the correct answer was 

 given twice iu succession. 



The tests were then again repeated, but with this difference that, 

 after the observation of the colours, the light of an electric lamp, 

 in a little box, of which the cardboard with the colours formed the 

 foreside, was exposed by the removal of the cardboard and the light 

 allowed to shine in the eyes of the subject during 15 seconds. The 

 influence of the subsequent strong light could be determined by 

 investigating how often the test had to be repealed to get the correct 

 answer twice. 



This test was subsequently repeated in precisely the same way 

 with four figures e.g. X O A D which are drawn in pairs next to 

 each other on the cardboard, and afterwards also Avith three coloui-s 

 and three figures, which were drawn in such a way that there was 

 a colour next to each figure. 



The result of these tests was such that in normal people a very 

 slight destruction was caused by the subsequent inq)ulse, but iu 

 persons suffering from dementia this was the case to an important 

 degree. At my insligalion these experiments have been repeated in 

 a slightly modified form and the results obtained will be published 

 in a thesis. 



