LAMINAR LESIONS IN CEREBRAL CORTEX 



363 



Fig. 4. Area enclosed by the rectangle in Fig. 3 shown imder magnification of 150. 



liniated, '■detocused" beam from the cyclotron. Measurements ot the current 

 in an aroon-filled, transverse ionization chamber, placed at the end of the 

 beam pipe, were made to calculate the radiation doses. After the beam left 

 the ionization chamber, it traxersed usually 334 in. of air before strikint;' the 

 taroet. A rifle telescopic sisht with an illumination de\"ice and a mirror was 

 mounted on a slide on the ionization chamber, so it could be moved with 

 precision into alignment, and the taroet area centered in the cross hairs of 

 the telescope. With suitable calibrations, the telescope served to center the 

 target in relation to the beam and to bring the target to a predetermined 

 distance from the ion chamber. 



The aseptic operation consisted of removal of the bone, preparation of 

 a bloodless field, and closure after irradiation. All irradiations were done 

 with dura intact. 



Figure 6 shows the well known Bragg curve. The curve, for 20 Mev deu- 

 terons. plots the relative ionizations after penetration of aluminum foil 

 against the thickness of the foil. There is a sharp rise in number of ions 

 produced just before the end of the range, and the value for the ionization 

 peak is nearly 5 times higher than at the beginning of the range. This sharp 



