Rats with parasagittal incised wounds of the telencephalon were treated for 1,7, 
21 or 56 days with triiodothyronine (T3), 0.5 mug/100 g body weight, injected 
once daily. Controls were injected with the aqueous solution in which the T3 was 
dissolved. The brains were examined histologically and quantitative assessments 
were made of the regeneration of axons into and across the lesions and of the 
healing of the wounds. T3, when administered over an 8 week period, stimulated 
axonal regeneration in the dorsal cortex and corpus callosum and promoted 
healing of the wound in the corpus callosum. The results of this investigation 
suggest that the use of T3 in the clinical treatment of injury to the central 
nervous system may be of less value than the work of earlier authors had 
indicated.