30 



BRIZZEE, JACOBS, KHARETCHKO AND SHARP 



The mean values for neuroglial packing density in the control groups 

 decreased from 45,000 cells/mm^ at 1 day to 27,000 at 20 days, but the dif- 

 ferences between the various age levels in this series are not significant owing 

 to a rather large variance in counts. The mean neuroglial packing density 

 for all four age groups in the nonirradiated animals was 34,000 cells/mm^. 

 The neuroglial density in the 100 and 200 r groups did not differ significantly 

 from the controls, but in the 300 r group, the value for neuroglial density in 

 1 -day-old animals was significantly higher (80,000 cells/mm'; /; < .05) 

 than in the nonirradiated groups. In later stages the differences were not 

 significant. 



The neuroglia/neuron index (Fig. 2), almost entirely as a result of the 



0.40 



0.38 



0.36 

 034 



0.32 



030 



0.26 



xO-26 



UJ 



00.24 



z 



022 



z 



S020 



D 

 UJ 



z 0.18 

 < 0.16 

 §0.14 



010 

 0.08 

 0.06 



0.04 

 0.02 



1= CONTTROL 

 A^ lOOr 

 o-200r 

 o- 300r 



10 

 AGE (DAYS) 



20 



Fig. 2. Increase in neuroglia/neuron index from 1st to 20th postnatal day. 



