Sentence:  Half crazed by the weight dragging , the dust , and the heat , the horse leaped our wall , dashing out the rider 's <WSD>brains</WSD> against it , and leaving him lying there among us - while the horse crashed away through the brush . 
Meaning of the word marked with <WSD> tags:  that part of the central nervous system that includes all the higher nervous centers; enclosed within the skull; continuous with the spinal cord